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RESOLUTION NO. 40
BE IT RESOLVED,
that the American College of Radiology adopt the ACR–AAPM–SIIM–SPR Practice Parameter for
Digital Radiography
Sponsored By:
ACR Council Steering Committee
The American College of Radiology, with more than 30,000 members, is the principal organization of radiologists, radiation oncologists, and clinical
medical physicists in the United States. The College is a nonprofit professional society whose primary purposes are to advance the science of radiology,
improve radiologic services to the patient, study the socioeconomic aspects of the practice of radiology, and encourage continuing education for
radiologists, radiation oncologists, medical physicists, and persons practicing in allied professional fields.
The American College of Radiology will periodically define new practice parameters and technical standards for radiologic practice to help advance the
science of radiology and to improve the quality of service to patients throughout the United States. Existing practice parameters and technical standards will
be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner, if indicated.
Each practice parameter and technical standard, representing a policy statement by the College, has undergone a thorough consensus process in which it has
been subjected to extensive review and approval. The practice parameters and technical standards recognize that the safe and effective use of diagnostic and
therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published
practice parameter and technical standard by those entities not providing these services is not authorized.
Revised 2012 (Resolution 37)*
ACR–AAPM–SIIM–SPR PRACTICE PARAMETER FOR DIGITAL
RADIOGRAPHY
PREAMBLE
This document is an educational tool designed to assist practitioners in providing appropriate radiologic care for
patients. Practice Parameters and Technical Standards are not inflexible rules or requirements of practice and are
not intended, nor should they be used, to establish a legal standard of care1. For these reasons and those set forth
below, the American College of Radiology and our collaborating medical specialty societies caution against the
use of these documents in litigation in which the clinical decisions of a practitioner are called into question.
The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by the
practitioner in light of all the circumstances presented. Thus, an approach that differs from the guidance in this
document, standing alone, does not necessarily imply that the approach was below the standard of care. To the
contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in this
document when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition
of the patient, limitations of available resources, or advances in knowledge or technology subsequent to
publication of this document. However, a practitioner who employs an approach substantially different from the
guidance in this document is advised to document in the patient record information sufficient to explain the
approach taken.
1 Iowa Medical Society and Iowa Society of Anesthesiologists v. Iowa Board of Nursing, ___ N.W.2d ___ (Iowa 2013) Iowa Supreme Court refuses to find
that the ACR Technical Standard for Management of the Use of Radiation in Fluoroscopic Procedures (Revised 2008) sets a national standard for who may
perform fluoroscopic procedures in light of the standard’s stated purpose that ACR standards are educational tools and not intended to establish a legal
standard of care. See also, Stanley v. McCarver, 63 P.3d 1076 (Ariz. App. 2003) where in a concurring opinion the Court stated that “published standards or
guidelines of specialty medical organizations are useful in determining the duty owed or the standard of care applicable in a given situation” even though
ACR standards themselves do not establish the standard of care.
PRACTICE PARAMETER
Digital Radiography
2017 Resolution No. 40
NOT FOR PUBLICATION, QUOTATION, OR CITATION
The practice of medicine involves not only the science, but also the art of dealing with the prevention, diagnosis,
alleviation, and treatment of disease. The variety and complexity of human conditions make it impossible to
always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment.
Therefore, it should be recognized that adherence to the guidance in this document will not assure an accurate
diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable
course of action based on current knowledge, available resources, and the needs of the patient to deliver effective
and safe medical care. The sole purpose of this document is to assist practitioners in achieving this objective.
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KEY POINTS
The intent of this document is to provide guidance and assistance in the understanding and clinical use of digital
radiography equipment (other than mammography) in order to deliver optimal necessary image quality at an
appropriate minimal radiation dose and to ultimately provide excellent safety and care for patients undergoing
digital radiography examinations. An introduction to the realm of digital radiography, including definitions, is
presented in section I. As new capabilities and complexities arise with digital imaging devices, the qualifications
and responsibilities of personnel—including the physician, medical physicist, radiologist assistant, radiologic
technologist, and image management specialist—are affected as outlined in section II.
I.
INTRODUCTION AND DEFINITION
This practice parameter was developed collaboratively by the American College of Radiology (ACR), the
American Association of Physicists in Medicine (AAPM), the Society for Imaging Informatics in Medicine
(SIIM), and the Society for Pediatric Radiology (SPR).
This practice parameter is applicable to the practice of digital radiography. It defines qualifications of
personnel, equipment guidelines, data manipulation, data management, quality control (QC), and quality
improvement procedures for the use of digital radiography that should result in optimal radiological
patient care. A glossary of relevant digital terms used in this document is located in Appendix A.
Increasingly Medical imaging and patient information are being managed using digital data during acquisition,
transmission, storage, display, interpretation, and consultation. The management of these data during each of
these operations may have an impact on the quality of patient care and outcomes.
For the purpose of this document, the practice of digital radiography refers to projection X-ray imaging
that uses a digital X-ray detector to capture the X-ray image. Digital X-ray detectors are typically classified
as either computed radiography (CR) or digital radiography (DR). CR uses a photostimulable storage
phosphor that stores a latent image, which is subsequently read out using a stimulating laser beam. DR is
used to describe any X-ray detector that electronically reads out an X-ray signal immediately after
exposure. Despite the fact that DR has been used for a specific acquisition technology, both CR and DR
refer to digital detection methods, and both should be considered as part of this practice parameter.
“CR” and “DR” are the commonly used terms for digital radiography detectors. CR is the acronym for computed
radiography, and DR is an acronym for digital radiography. CR uses a photostimulable storage phosphor that
stores the latent image, which is subsequently read out using a stimulating laser beam. It can be easily adapted to
a cassette-based system analogous to that used in screen-film (SF) radiography. Historically, the acronym DR has
been used to describe a flat-panel digital X-ray imaging system that reads the transmitted X-ray signal
immediately after exposure with the detector in place. Generically, the term CR is applied to passive detector
systems, while the term DR is applied to active detectors.
This practice parameter is applicable to the practice of digital radiography. It defines motivations, qualifications
of personnel, equipment guidelines, data manipulation and management, and quality control (QC) and quality
improvement procedures for the use of digital radiography that should result in high-quality radiological patient
care.
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In all cases for which an ACR practice parameter or technical standard exists for the modality being used or the
specific examination being performed, that practice parameter or technical standard will continue to apply when
digital image data management systems are used.
II.
QUALIFICATIONS AND RESPONSIBILITIES OF PERSONNEL
Individuals performing digital radiography procedures must be appropriately trained in the proper use of the
imaging equipment and must have the appropriate level of knowledge necessary to obtain optimal information for
each requested procedure. In all cases, the operator should be a physician, a radiologist assistant, a licensed and/or
registered radiologic technologist, or a radiation therapist. The radiologist assistant, technologist, or radiation
therapist must be operating under the direct supervision of a qualified licensed physician.
A.
Physician
See the ACR–SPR Practice Parameter for General Radiography [1]. Additional specific qualifications and
responsibilities include:
1. Physicians using digital radiography should understand the basic technology of image acquisition,
transmission, manipulation, processing, archiving, retrieval, and display, including the strengths,
weaknesses, and limitations of different methods. They should be knowledgeable in how to optimally
utilize the image viewing equipment. Where appropriate, the interpreting physician must be familiar with
the principles of radiation protection, the hazards of radiation, and radiation monitoring requirements as
they apply to both patients and personnel. The physician performing the official interpretation must be
responsible for the quality of the images being reviewed and understand the elements of QC of digital
image management systems2.
2. The physician must demonstrate qualifications as delineated in the appropriate ACR practice parameter or
technical standard for the particular diagnostic modality being interpreted.
3. The physician should have a working knowledge of those portions of the digital imaging chain from
acquisition to display that affect image quality and that have the potential for producing artifacts, and/or
changes in image quality.
B.
Qualified Medical Physicist
A Qualified Medical Physicist must be on site or available as a consultant. See the ACR–AAPM Technical
Standard for Diagnostic Medical Physics Performance Monitoring of Radiographic Equipment [2].
A Qualified Medical Physicist is an individual who is competent to practice independently in one or more of the
subfields in medical physics. The American College of Radiology considers certification, continuing education,
and experience in the appropriate subfield(s) to demonstrate that an individual is competent to practice one or
more of the subfields in medical physics and to be a Qualified Medical Physicist. The ACR strongly recommends
that the individual be certified in the appropriate subfield(s) by the American Board of Radiology (ABR), the
Canadian College of Physics in Medicine, or by the American Board of Medical Physics (ABMP).
A Qualified Medical Physicist should meet the ACR Practice Parameter for Continuing Medical Education
(CME). (ACR Resolution 17, adopted in 1996 – revised 2012, Resolution 42) [3]
2The ACR Rules of Ethics state: “It is proper for a diagnostic radiologist to provide a consultative opinion on radiographs and other images regardless of
their origin. A diagnostic radiologist should regularly interpret radiographs and other images only when the radiologist reasonably participates in the quality
of medical imaging, utilization review, and matters of policy which affect the quality of patient care.”
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The appropriate subfield of medical physics for this technical standard is Diagnostic Medical Physics. (Previous
medical physics certification including Radiological Physics, Diagnostic Radiological Physics, and Diagnostic
Imaging Physics are also acceptable.)
C.
Registered Radiologist Assistant
See the ACR–SPR Practice Parameter for General Radiography [1].
A registered radiologist assistant is an advanced level radiographer who is certified and registered as a radiologist
assistant by the American Registry of Radiologic Technologists (ARRT) after having successfully completed an
advanced academic program encompassing an ACR/ASRT (American Society of Radiologic Technologists)
radiologist assistant curriculum and a radiologist-directed clinical preceptorship. Under radiologist supervision,
the radiologist assistant may perform patient assessment, patient management and selected examinations as
delineated in the Joint Policy Statement of the ACR and the ASRT titled “Radiologist Assistant: Roles and
Responsibilities” and as allowed by state law. The radiologist assistant transmits to the supervising radiologists
those observations that have a bearing on diagnosis. Performance of diagnostic interpretations remains outside the
scope of practice of the radiologist assistant. (ACR Resolution 34, adopted in 2006)
D.
Radiologic Technologist, and Radiation Oncology Therapist
The radiologic technologist or radiation oncology therapist must be certified by the appropriate registry and/or
possess unrestricted state licensure.
See the ACR–SPR Practice Parameter for General Radiography [1]. Additional specific qualifications and
responsibilities include:
1. The individual must meet the qualification requirements of any existing ACR practice parameter or
technical standard for acquisition of a particular examination.
2. He or she must be trained to properly operate those portions of the image data management system with
which he or she must routinely interact. This training should include as appropriate:
a. Image acquisition technology
b. Image processing protocols
c. Proper selection of examination specific options.
d. Image evaluation
e. Radiation dose indicators
f. Patient safety procedures
E.
Imaging Informatics Professional
See the ACR–AAPM–SIIM Technical Standard for Electronic Practice of Medical Imaging [4]. The
Imaging Informatics Professional should be qualified to assess and provide problem-solving input, initiate repair,
and coordinate system-wide maintenance programs to assure sustainable high image quality and system function.
The responsibilities and experience for an imaging informatics professional include:
Maintenance of the network for all informatics systems, eg, Radiology Information System (RIS), Picture
Archiving and Communication System (PACS), speech recognition systems, and computer servers and desktops.
1. Maintenance of the integrity of system databases to ensure continuous and accurate operation of the
informatics systems.
2. Coordination of the interaction and functionality of all data entry and management systems with the
necessary radiology applications, programs, and databases.
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3. Knowledge of computer systems using all possible operating systems (Windows, Unix/Linux, Mac), data
communications standards and equipment, network protocols, database management, internet protocols,
and systems analysis methods and design.
A Qualified Imaging Informatics Professional is an individual who is competent to practice independently in the
areas of informatics listed above. He or she should have a minimum of a bachelor’s degree in computer science or
equivalent. Continuing education and experience in imaging informatics demonstrate that an individual is
competent to practice as an imaging informatics professional. Certification through the American Board of
Imaging Informatics (ABII) can be used to validate an individual’s qualification as a qualified imaging
informatics professional
III.
EQUIPMENT SPECIFICATIONS
Specifications for equipment used in digital image data management will vary depending on the application and
the individual facility’s needs but in all cases should provide image quality and availability appropriate to the
clinical needs.
A.
Image Availability and Information Standardization
To ensure the enterprise-wide availability of features and performance when purchasing digital radiographic and
connected equipment, consideration of the manufacturers’ statements of conformance with the current ACR–
National Electrical Manufacturers Association Digital Imaging and Communications in Medicine (DICOM)
standard is strongly recommended. Also, consideration of periodic upgrades incorporating the expanding features
of that standard should be part of the ongoing QC program. Compliance with the Radiological Society of North
America and Healthcare Information and Management Systems Society (HIMSS) Integrating the Healthcare
Enterprise (IHE) Initiative, as embodied in the available technical frameworks, is also strongly recommended for
all new equipment acquisitions.
Specifications and usage guidelines related to standards and interoperability include:
1. Digital radiographic devices must provide images that conform to the DICOM standard “CR” or “DX”
service class objects. These objects’ header fields specify information such as accession number, patient
name, identification number, date and time of examination, name of facility or institution of acquisition,
type of examination, patient or body part orientation (eg, right, left, superior, inferior), amount and
method of data compression, and total number of images acquired in the study.
2. The use of DICOM modality work lists is recommended to help ensure the quality and accuracy of the
information captured in the DICOM header.
3. The use of the DICOM “DX” service class object is recommended instead of the more limited “CR”
object for digital radiography [5].
4. It is recommended to use DICOM grayscale soft-copy presentation state (GSPS) objects to transmit
annotations, shutter, and display lookup tables (LUTs) [6]. Where GSPS is not available or not
supported by a picture archiving and communication system (PACS), the use of a volume values-ofinterest lookup table (VOI-LUT) within the “CR” or “DX” service class object is suggested.
5. Details related to image acquisition, such as tube potential (kV), and tube current (mA), exposure time,
beam filtration, source image distance, and radiation exposure the International Electrotechnical
Commission (IEC) 62494-1 detector exposure indicator (EI), target exposure index (EIT), deviation
index (DI), and organ-specific postprocessing algorithm employed, should be recorded in the
DICOM header. These elements should be exportable using the DICOM Structured Report.
particularly for cassette-based and cassette-less DRs that have a direct interface to the X-ray generator
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B.
Acquisition
Image acquisition should be performed in accordance with the ACR–SPR Practice Parameter for General
Radiography or examination-specific ACR practice parameters and technical standards [1].
1. Use of antiscatter grids
Scattered radiation diminishes reduces contrast in radiography, reducing limiting the available
dynamic range of X-ray intensities at the beam exit side of the patient. It also decreases the SNR
because it contains no signal but does contain X-ray quantum noise
a. Scanned slot DR detectors possess inherent scatter rejection capability and do not require the use of
a grid.
b. Area detectors employed in digital radiography should be used with an antiscatter grid in clinical
imaging situations where with increased scatter component. dominates and usually at patient
thicknesses in excess of 10 cm Grids are not required when imaging small pediatric patients or
small body parts such as extremities soft-tissue-equivalent thickness less than 12 cm. Grid uses
for specific radiographic examinations are discussed in examination-specific ACR practice
parameters and technical standards and relevant scientific literature [7]. Use of software scatter
correction, especially in pediatric patients, is encouraged.
c. When using stationary grids, consider the use of a high-strip-frequency grid of more than 60
lines/cm to avoid grid aliasing patterns caused by insufficient sampling. Consultation with a
Qualified Medical Physicist or the vendor regarding an appropriate grid is recommended.
d. When using anti-scatter grids with digital detectors, an increase in exposure tube current and/or
time (mAs) is necessary only to compensate for attenuation of primary radiation by the grid.
2. Detector exposure indicators for digital radiography
With Considering the wide exposure latitude of digital radiographic devices, the visual appearance of
brightness and contrast in radiographic images is not a good a poor indicator of the appropriateness of
the exposure delivered to the image receptor. Digital radiographic devices can create satisfactory
images over a wide range of input exposures, including exposures that are significantly greater than are
clinically necessary. For images acquired with higher than desired detector exposure, the patient may
unnecessarily receives excessive radiation dose. Images acquired at lower than required exposures may
have unacceptably high noise levels. For these reasons, digital radiography system manufacturers
should provide a number (ie, an exposure indicator, or air kerma indicator) incorporate IEC standards
on EI, EIT, and DI (also supported by the AAPM Task Group 116 report) [8]. that The EI reflects
the estimated exposure reaching a proportional estimate of the incident air kerma at the detector,
the EIT is the examination-specific target exposure index value, and the DI is a calculated value to
quantify how far the given EI is from the EIT specific to the radiographic examination. This can
provide feedback to technologists on the appropriateness of a chosen imaging technique or to a practice
in determining its standard techniques. A parameter related to incident radiation dose such as AirKerma Area Product may be provided.
Currently, most digital radiography manufacturers provide an a proprietary exposure indicator that is
displayed alongside the image on the acquisition workstation, providing feedback to the technologist
about the acquisition technique. This information should also be transmitted to the PACS in the
DICOM header of the image. Generally, display of the acquisition technical technique factors has been
of greatest use great benefit to the clinical imaging team in optimizing technique factors eventually
to the benefit of the patient population. Image review stations should be configurable to display
EI, EIT and DI. to the radiologic technologist and of less utility to the interpreting physician. However,
should it be desired, it should be configurable for the exposure indicator to be shown along with the
image on either the technologist’s QC display or the radiologist’s diagnostic display
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Today The various numerical exposure indicators currently used by the different digital radiography
manufacturers are inconsistent and not easily comparable. Incorporation of a single standard such as
the IEC 62494-1 measures of EI, EIT, and DI for various radiographic studies will help implement
a uniform feedback mechanism for technologists, radiologists, and Qualified Medical Physicists
across all platforms from various manufacturers of X-ray projection radiography systems. This
will allow standardized communication, comparison across systems, and systems improvement.
The AAPM formed Task Group 116 to address the lack of a uniform exposure indicator on digital
radiography images [8]. Its report, “Recommended Exposure Indicator for Digital Radiography,”
defines standardized radiation exposure conditions from which a relative exposure indictor can be
defined
The International Electro-technical Commission (IEC) released an international standard for the
exposure index of digital X-ray imaging systems [9] that is consistent with AAPM Report 116 [8].
Presently, new DR systems and upgraded software versions for existing equipment are incorporating
the IEC standard. In addition to the traditional exposure index, a deviation index is reported that
describes how the exposure index deviates from a target value. Users should review the target values
for all views of all body parts that the system will be used to image. Target values should be selected to
minimize the exposure to the patient while providing diagnostic images (ie, with sufficiently low noise)
for interpretation
3. Exposure creep
In digital radiography, excessive exposure to the detector can produce high-quality images with
improved noise properties. Unless there is an understanding that these higher quality images come at
the cost of increased patient exposure and strategies are in place to control patient exposure, a
radiologic practice may experience “exposure creep” [10]. Exposure creep results when there is
negative radiologist feedback for high-noise images made with low exposures but a lack of negative
feedback or even positive feedback for low-noise images made with high exposures. As technologists
respond to this feedback, patient exposures may gradually increase over time. The Qualified Medical
Physicist should help implement a program to monitor for exposure creep on a consistent, ongoing
basis. Use of modern radiation dose–monitoring software platforms may help in monitoring the
radiation dose distribution for various examinations and various age groups. as it may be a
recurring phenomenon
A method to prevent exposure creep is to develop validated radiographic techniques charts as a function
of patient size for all performed examinations. Technique charts should encourage the use of
appropriate automatic exposure control (AEC) settings (single cell versus a combination of
multiple AEC cells) for most of the body radiographic examinations. The AEC system is designed
to deliver calibrated and reproducible doses to the image receptor across a wide range of
operating conditions, including X-ray beam quality and patient size. If Often these factors are
entered into the anatomical programming of state-of-the-art X-ray generator controls. the technologist
can simply select the radiological examination and patient size at the beginning of an examination. If
the technologists uses these techniques programs, the facility is assured of the very likely to use of
standard appropriate radiographic technique factors with the appropriate level of and standard
radiation exposure. Consistent and optimal AEC performance is critical to radiation dose
management and image quality. Qualified Medical Physicists should perform appropriate tests to
ensure the expected performance of AEC modules whether the examination is performed with
automatic exposure control (AEC) or manual techniques [11].
4. Radiographic technique considerations for digital radiography
a. Determining proper exposure factor technique charts for standard examinations
Exposure (technique) charts are part of the standard of care expected by the Joint Commission and
are required by law in many states. It is necessary to check state and/or local regulations for any
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specific requirements. Computation of estimates for entrance skin exposures for these charts may
also be required.
Because of the wide latitude of digital image receptors and the availability of image processing to
alter the brightness and contrast of images, the visual appearance of images can be made similar
over a wide range of acquisition techniques. The primary effects of modifying an acquisition
technique are changes in:
i.
The appearance level of noise in the image
ii.
The exposure duration and potential for patient motion artifacts
iii.
Patient radiation exposure
iv.
Potential artifacts (in DR) related to detector saturation and image lag
Baseline or initial exposure technique charts are typically provided by equipment manufacturers,
either as prescriptions for manual radiographic technique or programmed examination-specific
options in the X-ray generator.
Exposure technique charts must be tailored for each digital radiography X-ray system and
generation detector and processing combination as well as patient population and size [12]. There is
considerable variability in image receptor response owing to varying scatter sensitivity, the use of
grids with different grid ratios, collimation, beam filtration, the choice of kilovoltage, source-toimage distance, and image receptor size.
Exposure technique charts are typically provided by equipment manufacturers, either as
prescriptions for manual radiographic technique or programmed examination specific options in the
X-ray generator. Many digital radiography systems also permit the choice of several speed
(exposure) classes. Technique factors for each clinically used speed class should be constructed. In
addition, exposure charts should be designed to function over a wide range of adult and pediatric
patient sizes [11]. and over the even wider range of pediatric patient sizes This task of building
optimized technique charts is a team effort involving the technologist, radiologist,
administrative leadership, and the Qualified Medical Physicist, and is a continuous process
requiring collaborative efforts of each member of the team [13].
Techniques can be modified to suit particular clinical needs or patient subgroups, and this process is
best done in collaboration between a Qualified Medical Physicist and radiologists. The aim of
modifying a radiographic technique for a particular clinical purpose would be to:
Decrease the appearance of noise in an image to better suit the intended diagnostic task.
Reduce patient exposure for images where higher noise levels are acceptable.
Reduce patient motion artifacts.
b. Automatic exposure control
AEC systems are designed to turn off the X-ray generator when the desired dose has been
received at the image receptor. This dose may vary as a function of X-ray beam energy, with
the presence or absence of an anti-scatter grid, or with the sensitivity (often misstated as
“speed”) setting of the AEC. AEC works well when the AEC system is properly calibrated
and the body part being imaged is centered over the active AEC region(s). AEC may fail to
deliver the desired receptor dose if the desired anatomy is not centered over the active
region(s), if the incorrect region(s) is selected, or if an object within the active region(s) of the
AEC system is of a markedly different density than tissue (eg, a prosthesis in the hip of a
patient or gonadal shielding) [12,14]. If the AEC system is covered by such an object (eg,
gonadal shielding), the backup timer should terminate the exposure prior to the regulatory
maximum mAs being delivered [15].
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In CR, AEC is frequently used with wall and under table Bucky devices in emergency, inpatient,
and outpatient radiology department settings. AEC units are designed to turn off the X-ray
generator when an appropriate exposure level has been received at the image receptor. They work
well when the device is properly calibrated and the body part being imaged is positioned properly
over the active AEC region. AEC may fail if positioning is poor or if material contained within the
sensitive area of the AEC device is of a different density than tissue, for example a prosthesis in the
hip of a patient In
AEC devices are energy dependent and may require calibration at multiple tube potential values to
function properly over a wide range of patient sizes. Some X-ray generators have preprogrammed
energy response curves and may not work as well with CR as with conventional SF receptors if
they were manufactured to be matched to typical SF energy and scatter characteristics. In this
situation, the AEC device should be recalibrated for use with CR [16,17].
In DR, the AEC device is typically built into the image receptor assembly and it works in a manner
similar to the systems used in SF radiography. Proper calibration should still be verified by a
Qualified Medical Physicist. Also, the selection of the appropriate sensitivity setting by
examination should be verified
c. Image repeat for improper Assessing appropriateness exposure
As described in section III.B.2, the DI should be reviewed for each clinical exposure and compared
to the desired range for the specific body part and view acquired. These ranges can be used to
develop radiographic technique charts or to monitor for dose creep in a practice. For absolute DI
values to be clinically meaningful, the target exposure indicator (EIT) must be set appropriately. In
typical clinical practice, wide distributions of the DI are observed. It is important that each practice
review DI data to establish recommended limits and targets for quality improvement (QI). Clinical
radiographs can be acceptable across a wide range of receptor doses, and a DI value that is extreme
should not be cause for immediately repeating an image without careful review and a potential
consult with a radiologist. Extreme DI values should be logged for review at periodic QI committee
meetings.
As described in section III.B.2, vendors should provide exposure indicators with images. These can
be used to provide an expected range of exposure indices for a given examination type. These
ranges can be used to develop exposure technique charts or to monitor for exposure creep in a
practice. However, an exposure indicator that is higher or lower than what is typical or expected
should not be cause for immediately repeating an image without careful review of the image.
It is important for the radiologist and technologist to review improperly exposed radiographs to
develop an understanding for which radiographs should be repeated. Technologists may need to be
provided with the appropriate image viewing resources (see section III.D.5) and training to
determine if a radiograph needs to be repeated on the basis of image noise or receptor saturation.
For the different classes of rejected images, it is useful to provide guidance to the technologist on
how to correct an improperly exposed radiograph, either through processing or by modifying
exposure technique
d. Pediatric imaging considerations
As with all imaging examinations involving ionizing radiation, digital radiography should be
performed using the lowest possible radiation exposure to the patient that is consistent with image
quality requirements. This is especially important when imaging pediatric patients, who are
believed to be up to 10 times more sensitive to ionizing radiation than adults [14,18]. However,
reducing exposure without assessing image quality increases the possibility of unacceptably high
quantum noise. Also, the appropriate reduction in exposure to the image receptor depends on how
well the digital system is optimized for pediatric imaging, and on the nature of the particular
condition being diagnosed [19].
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Commitment and effort on the part of staff are required the technologist to achieve exposure
reduction in pediatric imaging consistently is of paramount importance. First, the multiple X-ray
machines of a given type in a department require validation, calibration, and matching to ensure the
same exposure for similar radiographic technique parameters. The actual exposure required to
produce clinically acceptable images for a given digital receptor is a function of the digital
receptor’s detective quantum efficiency (DQE). The goal is to produce similar image quality in all
images regardless of the device chosen and regardless of the size of the pediatric patient. Second,
all CR readers and/or DR image receptors should be adjusted to provide a uniform response to the
recorded X-ray image pattern in space. Third, all monitors on all diagnostic display workstations
should be tested and calibrated to provide a uniform appearance of displayed images. These
Optimization issues in pediatric imaging and relevant topics are addressed in more detail
elsewhere [17].
Pediatric patients present unique challenges when imaged with digital radiography. Patients range
in size from the neonate to the young adult, requiring a wide range of radiographic technique
factors. Spatial resolution demands are higher in pediatric imaging owing to the smaller body
parts. Clinical use of AEC with children offers additional challenges since the pediatric
organs being small may result in partial coverage of AEC cells, resulting in artificially
shortening of the radiographic exposure. and a digital image receptor that properly processes an
X-ray pattern in space that may or may not cover the entire image receptor
Judicious consideration of gonadal shielding is warranted, providing shielding does not
compromise clinical objectives of the study. The ICRP tissue-weighting factor for gonads has
substantially decreased, from 0.25 in Publication 26 in 1977 to 0.20 in Publication 60 in 1990
and most recently to 0.08 in Publication 103 in 2007. Gonadal shields cannot protect against
internal scatter, may be positioned incorrectly, may obscure the area of interest, and, if they
cover the AEC chamber(s), may increase radiation exposure. The decision to use an antiscatter
grid must be carefully considered as a function of patient size. If a grid is employed, use of a
source-to-image distance consistent with grid focus is recommended to optimize image quality
and dose [20,21]. Use of additional filtration, such as 0.1-mm copper or more, is
recommended to reduce entrance skin air kerma at the patient surface for pediatric patients.
The use of additional filtration may require optimizing the image processing parameters to
account for a different x-ray energy spectrum incident upon the image receptor. A clinical
team composed of a diagnostic Qualified Medical Physicist, an application specialist from the
equipment manufacturer, an experienced technologist, and a radiologist will help achieve this
objective in an efficient fashion.
Standard positioning aids used to immobilize pediatric patients may generate unacceptable artifacts
when used with digital image receptors. Because the X-ray pattern resulting from a pediatric chest
has a different dynamic range and other characteristics [18] compared with an adult chest, image
processing and display parameters used by the digital acquisition device to properly display the
digital image may need to be configured as a function of patient size. Image processing and display
parameters may require further alteration if gonadal shielding or orthopedic implants appear in the
displayed image. Finally, because scoliosis examinations are common in children, the digital image
receptor must provide an efficient method to generate images up to 36 inches in length without
doubly exposing some sections of the patient’s anatomy. Use of newer technology, such as slot
scan units for orthopedic imaging, may further reduce dose associated with these
examinations. Additional information regarding pediatric imaging protocols best practices can be
found at the Image Gently website: www.imagegently.org.
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C.
Image Processing
For digital imaging, image processing can be divided into 2 parts.
Preprocessing is performed on the raw output of the digital detector and accounts for various performance
and engineering deficiencies of the image receptor.
Postprocessing is used to optimize the contrast, sharpness, and latitude of the image to be displayed at the
radiologist review work station [22]. (which is often proprietary to the device manufacturer and not under the
control of the radiologist) is used to determine display contrast by establishing the relationship between raw pixel
values and grayscale levels. This results in the final “For Presentation” image for interpretation on either hardcopy
film or softcopy displays.
1. Preprocessing
The image receptor on most digital radiography systems stores an electronic charge that is
monotonically related to the amount of radiation energy absorbed. At this stage, the signal (charge) is a
linear function of the incident radiation exposure. Preamplifiers and an analog-to-digital converter
transform the charge from each detector element to an integer representing the raw data image value.
The detector output with no processing applied is referred to as a raw image. This image is
typically not accessible to physicists. Several corrections are applied to the raw image values to obtain
values suitable for image processing. These corrections include interpolating account for bad pixels,
and to adjusting adjustments for nonuniformity of response of the image receptor in the form of
gain correction, and offset corrections to account for dark signal.
DR system users should ask the supplier for information indicating the number and type of bad pixels
that are being corrected. QC programs should include a process to report any new bad pixels that may
develop during the lifetime of the system. Nonuniformity corrections generally require running a
system utility program periodically, during which uniform exposures are acquired. Users should
identify the required procedure for each type of system being used and ensure that the procedures are
being followed. Some manufacturers require calibration to be performed by the technologist,
whereas for others it is the service engineer’s responsibility [23,24]. The calibration process
establishes a relationship between the pixel values and the deposited X-ray energy. Depending on
the equipment manufacturer, this relationship may be linear or logarithmic. The type of
calibration, number of calibration exposures, and bit depth available varies between different
vendors. The output of preprocessing a raw image is an image referred to as For Processing or
Original image [8]. This image should be available to the Qualified Medical Physicist for
quantitative image quality assessment.
For Processing images
Most DR systems transform the preprocessed value to a value proportional to the logarithm of the input
exposure. Logarithmic signals have the property that a fractional change in signal, due to the contrast
of adjacent structures, produces a fixed change in the raw image value independent of subject
penetration and input exposure. These values are the For Processing images values and may be stored
in DICOM image objects. The AAPM further recommends specific units for normalized For
Processing image values [8].
In some operations, users may archive For Processing images so that they may be processed at a later
date. For example, when reading a current digital mammography image it may be desirable for a prior
mammogram to be processed using the same method. Another use case involves CAD systems that
require For Processing images.
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2. Postprocessing DR image processing operations
a. Histogram analysis
The objective of histogram analysis is to determine the span of original image pixel values
that correspond to anatomical image information. The histogram shapes vary significantly
depending upon the anatomy under consideration. An important aspect of histogram analysis
is the identification and segmentation of the background and collimated regions, which have
no anatomical information. These useful pixel values are passed on to the postprocessing
algorithm for contrast and edge enhancement. The IEC exposure index is based on measures
of the clinically relevant histogram in the original image.
b. Contrast and frequency enhancement
Image processing operations are performed on For Processing/Original images to obtain For
Presentation images with values suitable for interpretation. display on a workstation monitor. All
Suppliers of DR digital imaging equipment may provide image processing software that can
restore the sharpness of edges, enhance detail contrast for images with a wide range of input
exposures, and reduce noise [25]. When properly implemented, image processing can restore the
sharpness of edges without introducing artifacts. Detail contrast can be enhanced by multifrequency
processing that equalizes image brightness over broad areas by operating on low spatial
frequencies. Most recently, methods have been introduced to reduce high frequency image noise
without adversely effecting image resolution. In general, the image processing from different
systems can be adjusted to give similar presentation appearance for images of the same body part,
as the desired appearance may be different in different facilities. The user should anticipate working
with the applications specialists of their equipment manufacturer to configure the desired image
processing looks.
The parameters used to process images need to be specifically determined for all body parts and
views that will be encountered. This also may vary with radiologist preference. Consequently,
close cooperation between the equipment manufacturer’s installation engineer, application
specialist, site technologist, radiologist, administrator, and the Qualified Medical Physicist is
critical to optimization of the image postprocessing process for various examinations in an
efficient fashion. In the past, this required significant effort by the user to establish the desired
appearance for all views. Currently, most systems make these adjustments internally, with the user
determining the generic characteristics of the presented image. For example, users may differ with
respect to the amount of detail contrast enhancement that is desired.
DR image grayscale
As a part of the operations that transform For Processing images to For Presentation images, the
image values in the anatomical regions of interest, referred to as the values of interest (VOI), are
identified and used to compute a look-up table (LUT) used to display the For Presentation values.
Earlier systems applied the VOI-LUT in the DR systems and sent these image values within the
DICOM object. As described in section A above, it is preferable that the VOI-LUT be sent and that
the image display software transform the values at the workstation. This allows the user at the
workstation to make further adjustment in the grayscale of the image. The VOI are also used to
calculate the EI and DI associated that are used as indicators of proper radiographic technique (see
section B.2). The edges of the collimated regions of the image should be recognized by the system
and the regions outside of the collimators masked to prevent presentation of large bright regions to
the radiologist, and to ensure accurate computation of the EI. It is preferable that this mask be
encoded in the DICOM image as an overlay so that if needed it can be removed to see information
that might be near the collimated edge, such as a marker.
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3. Electronic Collimation
Electronic collimation is used to electronically mask areas of the digital image prior to being sent for
interpretation or archiving. Although there is controversy regarding the use of electronic collimation,
there are situations in which it is necessary and appropriate.
Depending upon the image histogram, the segmentation of the collimated or background regions may
not be accomplished properly by the automated algorithm. In such circumstances the technologist may
need to electronically collimate to exclude these areas to improve the grayscale rendering and reduce
possible veiling glare from areas that appear very bright. It is desirable to visualize the penumbra of the
physical collimators to verify appropriate X-ray beam collimation. This is visualized by a thin, bright
band around the image [26]. This millimeter-wide white margin around the image appears bright on the
radiographic image because no X-rays hit the detector beyond the edges of the collimated beam.
Electronic collimation can be used for inappropriate purposes, such as to hide poor X-ray beam
limitation (eg, using too large a field-of-view for a given protocol). Such uses are contrary to good
radiation safety practices and pose ethical challenges. Electronic collimation should never be used to
mask areas of the image having anatomical information.
D.
Image Data Integrity and Transmission
1. Compression
Data compression may be performed to facilitate image transmission and storage. The type of medical
image, the modality, and the objective of the study will determine the degree of acceptable
compression. For more information on image compression, see the ACR–AAPM–SIIM Technical
Standard for Electronic Practice of Medical Imaging [4].
2. Data transmission
The environment in which imaging studies are to be transmitted will determine the types and
specifications of the transmission devices used. In all cases, for official interpretation, the digital data
received at the end of any transmission must have minimal loss of clinically significant information.
The transmission system must also have adequate error-checking capability.
Additional consideration should be given for devices that rely on wireless networking capabilities. Such
systems are increasingly common in digital radiography, especially those used for bedside radiography.
The wireless transmission of information may be between the digital detector and the acquisition
workstation (ie, wireless DR detectors) or between the acquisition workstation and the institutional
PACS (ie, bedside imaging) or both. Provisions should be made for:
a. The prevention of signal interference and corruption between different systems communicating on
the same wireless network
b. Appropriate signal encryption to protect patient health information (PHI)
c. A strategy for loss-prevention and image recovery for images that have interrupted transmission or
corrupted transmission, especially for the communication between the detector and acquisition
workstation, which is less likely to use a DICOM standard transaction with storage-commitment
functionality.
d. A strategy to protect PHI if mobile viewing devices are lost (eg, remote data wipe)
For further details refer to the ACR–AAPM–SIIM Practice Parameter for Electronic Medical
Information Privacy and Security and the ACR–AAPM–SIIM Technical Standard for Electronic
Practice of Medical Imaging [4,27].
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3. Security
See the ACR–AAPM–SIIM Practice Parameter for Electronic Medical Information Privacy and
Security [27].
4. Archiving and retrieval, reliability and redundancy, and work and room environmental and ergonomic
considerations
See the ACR–AAPM–SIIM Technical Standard for Electronic Practice of Medical Imaging [4].
5. Display capabilities
The consistent presentation of images across different workstation display monitors is essential for a
quality imaging practice. Image quality is influenced by workstation software, graphic controllers, and
display devices, which vary substantially across a range of parameters and display characteristics as
described in the ACR–AAPM–SIIM Technical Standard for Electronic Practice of Medical Imaging
[4]. The preferred method to achieve similar display characteristics and consistent image appearance is
to implement the DICOM Part 14 Grayscale Standard Display Function (GSDF) [28] calibration
procedure for all image display monitors in order to preserve the perceptual variations in pixel values of
an image as perceived by a human viewer, even when viewing monitors with different luminance
values. Although GSDF calibration is typically a standard practice for primary diagnosis display
monitors on medical-grade PACS workstations, manufacturers of radiography devices and technologist
quality control imaging workstations should also provide calibration procedures and demonstration of
quantitative conformance to the DICOM GSDF as part of acceptance testing and periodic quality
control procedures for their displays. At a minimum, third-party GSDF calibration software should be
made available and implemented for all radiography display devices and QC workstations.
Images are viewed by technologists during acquisition, by radiologists during interpretation, and by
referring physicians as a part of patient care and should have a similar appearance for all viewers. The
following uses emphasize the importance of choosing appropriate display equipment and settings, as
well as the importance of regular calibration and maintenance as part of a QC program.
a. Image modifications are most often made by the technologist at the acquisition workstation.
Technologists may modify image processing to try to match the appearance desired by radiologists.
If the acquisition display does not meet the specifications for consistent presentation of images (as
described in the ACR–AAPM–SIIM Technical Standard for Electronic Practice of Medical Imaging
[4]) or is not calibrated or maintained properly, this image modification process is particularly
challenging.
b. A primary method for a radiology technologist to discern whether a low-exposure image acquisition
needs to be repeated is by comparison of the noise levels in the image with the desired diagnostic
appearance. Visualizing image noise may be difficult on poor performing displays. Noise
evaluation can be accomplished visually using the TG 18-AFC test pattern and following the
methods described in the AAPM Task Group Report 18 document [29].
c. Owing to the nature of use of point-of-care digital radiographic devices (ie, DR mobile X-ray
systems), they are often used for primary diagnostic tasks. Digital Given that digital images are
available for immediate review, it is not uncommon for digital radiographic devices to be used
at the point of care, such as in mobile imaging. If images are to be interpreted at the device
rather than on a diagnostic interpretation workstation, digital radiography manufacturers
should provide high interpretation-quality display options as outlined in the ACR–AAPM–SIIM
Technical Standard for Electronic Practice of Medical Imaging for displays on these devices which
diagnostic or primary interpretation tasks might be performed or one which images are modified
[4].
d. If the technologists are using QC stations for post-acquisition image analysis prior to sending the
images to PACS, then appropriate display monitors should be provided at the technologist QC
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station. Ideally these monitors should satisfy the minimum specifications as outlined in the ACR–
AAPM–SIIM Technical Standard for Electronic Practice of Medical Imaging [4].
Guidelines for viewing digital radiography images can be found in the ACR–AAPM–SIIM Technical
Standard for Electronic Practice of Medical Imaging and for mammography in the ACR–AAPM–SIIM
Practice Parameter for Determinants of Image Quality in Digital Mammography [4,30].
IV.
DOCUMENTATION
Physicians officially interpreting examinations3 using digital image data management systems should render
reports in accordance with the ACR Practice Parameter for Communication of Diagnostic Imaging Findings [31].
If reports are incorporated into the data management system, they should be retrievable with the same timeliness
and security as the imaging data.
V.
RADIATION SAFETY IN IMAGING
Radiologists, medical physicists, registered radiologist assistants, radiologic technologists, and all supervising
physicians have a responsibility for safety in the workplace by keeping radiation exposure to staff, and to society
as a whole, “as low as reasonably achievable” (ALARA) and to assure that radiation doses to individual patients
are appropriate, taking into account the possible risk from radiation exposure and the diagnostic image quality
necessary to achieve the clinical objective. All personnel that work with ionizing radiation must understand the
key principles of occupational and public radiation protection (justification, optimization of protection and
application of dose limits) and the principles of proper management of radiation dose to patients (justification,
optimization
and
the
use
of
dose
reference
levels)
http://wwwpub.iaea.org/MTCD/Publications/PDF/Pub1578_web-57265295.pdf.
Nationally developed guidelines, such as the ACR’s Appropriateness Criteria®, should be used to help choose the
most appropriate imaging procedures to prevent unwarranted radiation exposure.
Facilities should have and adhere to policies and procedures that require varying ionizing radiation examination
protocols (plain radiography, fluoroscopy, interventional radiology, CT) to take into account patient body habitus
(such as patient dimensions, weight, or body mass index) to optimize the relationship between minimal radiation
dose and adequate image quality. Automated dose reduction technologies available on imaging equipment should
be used whenever appropriate. If such technology is not available, appropriate manual techniques should be used.
Additional information regarding patient radiation safety in imaging is available at the Image Gently® for
children (www.imagegently.org) and Image Wisely® for adults (www.imagewisely.org) websites. These
advocacy and awareness campaigns provide free educational materials for all stakeholders involved in imaging
(patients, technologists, referring providers, medical physicists, and radiologists).
Radiation exposures or other dose indices should be measured and patient radiation dose estimated for
representative examinations and types of patients by a Qualified Medical Physicist in accordance with the
applicable ACR technical standards. Regular auditing of patient dose indices should be performed by comparing
the facility’s dose information with national benchmarks, such as the ACR Dose Index Registry, the NCRP
Report No. 172, Reference Levels and Achievable Doses in Medical and Dental Imaging: Recommendations for
the United States or the Conference of Radiation Control Program Director’s National Evaluation of X-ray
Trends. (ACR Resolution 17 adopted in 2006 – revised in 2009, 2013, Resolution 52).
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3The ACR Medical Legal Committee defines official interpretation as that written report (and any supplements or amendments thereto) that attach to the
patient’s permanent record. In health care facilities with a privilege delineation system, such a written report is prepared only by a qualified physician who
has been granted specific delineated clinical privileges for that purpose by the facility’s governing body upon the recommendation of the medical staff.
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VI.
QUALITY CONTROL AND IMPROVEMENT, SAFETY, INFECTION CONTROL, AND
PATIENT EDUCATION
Policies and procedures related to quality control and improvement, patient education, infection control, and
safety should be developed and implemented in accordance with the ACR Policy on Quality Control and
Improvement, Safety, Infection Control, and Patient Education appearing under the heading Position Statement on
QC & Improvement, Safety, Infection Control, and Patient Education on the ACR website
(http://www.acr.org/guidelines).
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Any facility using a digital image data management system must have documented policies and procedures for
monitoring and evaluating the effective management, safety, and proper performance of acquisition, digitization,
processing, compression, transmission, display, archiving, and retrieval functions of the system. The QC program
should be designed to maximize the quality and accessibility of diagnostic information.
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Equipment performance monitoring should be in accordance with the ACR–AAPM Technical Standard for
Diagnostic Medical Physics Performance Monitoring of Radiographic Equipment [2].
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A. Quality Control Program
A continuous QC program must be established for all digital radiography under the guidance of a Qualified
Medical Physicist. The Qualified Medical Physicist, in consultation and accordance with the equipment
manufacturer, applicable industry guidelines, published standards, and with state and federal regulations, should
determine the methodology and frequency of each test to be performed. An on-site radiologic technologist must
be identified to be responsible for conducting routine QC.
1. Performance testing and monitoring of CR and DR equipment should include the recommendations for
QC testing methods and frequencies contained in report of the AAPM Task Group No. 10. Acceptance
Testing and Quality Control of Photostimulable Storage Phosphor Imaging Systems [32].
2. Guidance on performance testing and monitoring of official or primary interpretation display devices is
available in the ACR–AAPM–SIIM Technical Standard for Electronic Practice of Medical Imaging [4].
B. Key Aspects of Ongoing Quality Control
The key aspects of ongoing QC include, but are not limited to:
1. Exposure analysis: Data relating to patient exposures, including DAP or exposure indicators, should be
collected and analyzed on a regular basis. Such data can be compared to published reference levels to
identify areas for improvement. SF imaging is largely self-policing in terms of receptor exposure, and
under and overexposed films are included in the rejected image analysis process.
2. Rejected image analysis: Rejected image analysis is commonly performed in SF imaging departments but
has been abandoned in many digital imaging departments, likely owing to the fact that physical images
are not collected and digital images are easily deleted. While the number of images rejected owing to
under and overexposure has been reduced in digital imaging, rejected image analysis is still critical, as
positioning errors continue to be the most common reason for repeating images. Rejected image data
should be collected and analyzed on a regular basis and corrective action taken when necessary [33].
1. Artifact identification: Artifacts are not eliminated when changing from SF to digital imaging, and the
types of artifacts that occur in digital radiography are different than those seen in SF imaging. Therefore,
it is important that radiologic technologists and radiologists be taught to identify common digital imaging
artifacts. In addition, radiologic technologists should carefully analyze each digital image for artifacts so
that corrective action, including restriction of equipment use, can be taken to eliminate the artifact. For
this reason, it is critical that the monitors used by the radiologic technologist to review images be suitable
for this task [33].
The results of the QC program must be monitored annually by the Qualified Medical Physicist. If measured
values of QC parameters fall outside the control limits, the Qualified Medical Physicist must initiate appropriate
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investigative or corrective actions. A Qualified Medical Physicist should be available to assist in prescribing
corrective actions for unresolved problems.
VII.
ACCEPTANCE TESTING
Initial performance testing of imaging equipment must be performed by a Qualified Medical Physicist upon
installation and should be completed before first clinical use. This testing may be more comprehensive than
periodic performance and compliance testing and should be consistent with current acceptance testing practices
for digital radiography. Specific tests to be performed depend on the type of equipment and the manufacturer’s
recommendations. The AAPM has a document (AAPM Task Group Report No. 10) available that describes
pertinent acceptance tests for photostimulable storage phosphor systems (computed radiography acquisition
devices) [32], many of which are applicable to other digital radiography acquisition devices (charge-coupled
device [CCD] and flat panel systems).
VIII. FOLLOW-UP PROCEDURES AND WRITTEN SURVEY REPORTS
The Qualified Medical Physicist should report the findings to the physician(s), to the responsible professional(s)
in charge of obtaining or providing necessary service to the equipment, and, in the case of the consulting
physicist(s), to the representative of the hiring party, and, if appropriate, initiate the required service. Action must
be taken immediately by verbal communication if there is imminent danger to patients or staff using the
equipment due to unsafe conditions. Written survey reports should be provided in a timely manner consistent with
the importance of any adverse findings.
ACKNOWLEDGEMENTS
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This practice parameter was revised according to the process described under the heading The Process for
Developing ACR Practice Parameters and Technical Standards on the ACR website
(http://www.acr.org/guidelines) by the Committee on Practice Parameters and Technical Standards – Medical
Physics of the ACR Commission on Medical Physics, the Committee on Practice Parameters – General, Small,
and Rural Practice of the ACR Commission on General, Small, Emergency and/or Rural Practice, and the
Committee on Practice Parameters – Pediatric Radiology of the ACR Commission on Pediatric Radiology in
collaboration with the AAPM, the SIIM, and the SPR.
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Collaborative Committee – members represent their societies in the initial and final revision of this practice
parameter.
ACR
Ishtiaq H. Bercha, MSc, Co-Chair
Ralph P. Lieto, MS, FACR, FAAPM, Co-Chair
Steven Don, MD
Douglas E. Pfeiffer, MS, FACR, FAAPM
Padmaja A. Jonnalagadda, MD
AAPM
Nicholas B. Bevins, PhD
A. Kyle Jones, PhD
SIIM
Katherine P. Andriole, PhD
Elizabeth Krupinski, PhD
J. Anthony Seibert, PhD, FACR
Alexander J. Towbin, MD
Srini Tridandapani, MD
SPR
John B. Amodio, MD, FACR
Evelyn Y. Anthony, MD
John A. Cassese, MD
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Committee on Practice Parameters and Technical Standards – Medical Physics
(ACR Committee responsible for sponsoring the draft through the process)
Maxwell R. Amurao, PhD, MBA, Chair
Charles M. Able, MS
PRACTICE PARAMETER
Lijun Ma, PhD, FAAPM
Jonathon A. Nye, PhD
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2017 Resolution No. 40
NOT FOR PUBLICATION, QUOTATION, OR CITATION
Committee on Practice Parameters and Technical Standards – Medical Physics
(ACR Committee responsible for sponsoring the draft through the process)
Ishtiaq H. Bercha, MSc
Caridad Borrás, DSc, FACR, FAAPM, FIOMP
Chee-Wai Cheng, PhD, FAAPM
William R. Geiser, MS
Mary Ann Keenan, DMP
Ralph P. Lieto, MS, FACR, FAAPM
Matthew A. Pacella, MS, FACR
William Pavlicek, PhD
Douglas E. Pfeiffer, MS, FACR, FAAPM
Premavathy Rassiah, PhD
Thomas G. Ruckdeschel, MS
Christopher J. Watchman, PhD
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Committee on Practice Parameters – General, Small, Emergency and/or Rural Practice
(ACR Committee responsible for sponsoring the draft through the process)
Sayed Ali, MD, Chair
Marco A. Amendola, MD, FACR
Gory Ballester, MD
Lonnie J. Bargo, MD
Christopher M. Brennan, MD, PhD
Resmi A. Charalel, MD
Charles E. Johnson, MD
Candice A. Johnstone, MD
Padmaja A. Jonnalagadda, MD
Pil S. Kang, MD
Jason B. Katzen, MD
Serena McClam Liebengood, MD
Steven E. Liston, MD, MBA, FACR
Gagandeep S. Mangat, MD
Tammam N. Nehme, MD
Jennifer L. Tomich, MD
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Committee on Practice Parameters – Pediatric Radiology
(ACR Committee responsible for sponsoring the draft through the process)
Beverley Newman, MB, BCh, BSc, FACR, Chair
Lorna P. Browne, MB, BCh
Timothy J. Carmody, MD, FACR
Brian D. Coley, MD, FACR
Lee K. Collins, MD
Monica S. Epelman, MD
Lynn Ansley Fordham, MD, FACR
Kerri A. Highmore, MD
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Sue C. Kaste, DO
Tal Laor, MD
Terry L. Levin, MD
Marguerite T. Parisi, MD, MS
Sumit Pruthi, MBBS
Nancy K. Rollins, MD
Pallavi Sagar, MD
Richard A. Geise, PhD, FACR, FAAPM, Chair, Commission on Medical Physics
Robert S. Pyatt, Jr., MD, FACR, Chair, Commission on General, Small, Emergency and/or Rural Practice
Marta Hernanz-Schulman, MD, FACR, Chair, Commission on Pediatric Radiology
Jacqueline A. Bello, MD, FACR, Chair, Commission on Quality and Safety
Matthew S. Pollack, MD, FACR, Chair, Committee on Practice Parameters and Technical Standards
Comments Reconciliation Committee
Richard B. Gunderman, MD, PhD, FACR, Chair
Beth A. Schueler, PhD, FACR, FAAPM, Co-Chair
Sayed Ali, MD
John B. Amodio, MD, FACR
Maxwell R. Amurao, PhD, MBA
Katherine P. Andriole, PhD
Evelyn Y. Anthony, MD
Kimberly E. Applegate, MD, MS, FACR
Jacqueline A. Bello, MD, FACR
Ishtiaq H. Bercha, MSc
Nicholas B. Bevins, PhD
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2017 Resolution No. 40
Marta Hernanz-Schulman, MD, FACR
William T. Herrington, MD, FACR
A. Kyle Jones, PhD
Padmaja A. Jonnalagadda, MD
Beth M. Kline-Fath, MD
Elizabeth Krupinski, PhD
Ralph P. Lieto, MS, FACR, FAAPM
Beverley Newman, MB, BCh, BSc, FACR
Douglas E. Pfeiffer, MS, FACR, FAAPM
Matthew S. Pollack, MD, FACR
Robert S. Pyatt Jr., MD, FACR
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NOT FOR PUBLICATION, QUOTATION, OR CITATION
Comments Reconciliation Committee
Caridad Borrás, DSc, FACR, FAAPM, FIOMP
John A. Cassese, MD
Steven Don, MD
Kate A. Feinstein, MD, FACR
Richard A. Geise, PhD, FACR, FAAPM
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J. Anthony Seibert, PhD, FACR
Timothy L. Swan, MD, FACR, FSIR
Alexander J. Towbin, MD
Srini Tridandapani, MD
REFERENCES
1. American College of Radiology. ACR-SPR practice parameter for general radiography. Available at:
http://www.acr.org/~/media/95AB63131AD64CC6BB54BFE008DBA30C.pdf. Accessed March 2, 2016.
2. American College of Radiology. ACR-AAPM technical standard for diagnostic medical physics
performance monitoring of radiographic equipment. Available at:
http://www.acr.org/~/media/994DDAC06DAA44619874EB85313A554A.pdf. Accessed June 27, 2016.
3. American College of Radiology. ACR practice parameter for continuing medical education (CME).
Available: http://www.acr.org/~/media/FBCDC94E0E25448DAD5EE9147370A8D1.pdf. Accessed
March 2, 2016.
4. American College of Radiology. ACR-AAPM-SIIM technical standard for electronic practice of
medical imaging. Available at:
http://www.acr.org/~/media/AF1480B0F95842E7B163F09F1CE00977.pdf. Accessed March 2, 2016.
5. Grayscale softcopy presentation state storage. Rosslyn, Va: Digital Imaging and Communications in
Medicine; 1999. Supplement 33.
6. Clunie DA. Designing and implementing a PACS aware DICOM image object for digital X-ray,
mammography, and intraoral applications. Proceedings of SPIE. In: Blaine GJ, Horii SC, ed. Medical
Imaging 1999: PACS Design and Evaluation: Engineering and Clinical Issues. Bellingham, WA: SPIE;
1999:83-89.
7. Fritz S, Jones AK. Guidelines for anti-scatter grid use in pediatric digital radiography. Pediatr Radiol
2014; 44:313-321.
8. Shepard SJ, Wang J, Flynn M, et al. An exposure indicator for digital radiography: AAPM Task Group 116
(executive summary). Med Phys 2009; 36:2898-2914.
9. Medical electrical equipment - Exposure index of digital X-ray imaging systems - Part 1: Definitions and
requirements for general radiography. Geneva, Switzerland: International Electrotechnical Commission;
2008. IEC 62494-1 ed1.0.
10. Seibert JA, Shelton DK, Moore EH. Computed radiography X-ray exposure trends. Acad Radiol 1996; 3:313318.
11. Goldman LW. Speed values, AEC performance evaluation, and quality control with digital receptors. In:
Goldman LW, Yester MV, ed. Specifications, performance evaluations, and quality assurance of
radiographic and fluoroscopic systems in the digital era. 1st ed: Medical Physics Publishing; 2004:272-297.
12. Carroll OB. Fuch's Radiographic Exposure and Quality Control. 7th ed. Springfield, Ill: Charles C. Thomas
Publisher; 2003.
13. Shah C, Jones AK, Willis CE. Consequences of modern anthropometric dimensions for radiographic
techniques and patient radiation exposures. Med Phys 2008; 35:3616-3625.
14. Hall EJ. Lessons we have learned from our children: cancer risks from diagnostic radiology. Pediatr Radiol
2002; 32:700-706.
15. U.S. Food and Drug Administration. CFR - code of federal regulations title 21, vol 8: 21CFR1020.31.
Available at: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=1020.31.
Accessed July 25, 2016.
16. Ballinger PW, Frank ED. Merrill's Atlas of Radiographic Positions and Radiologic Procedures. Vol I-III.
10th ed. St. Louis, MO: Mosby; 2003.
17. Willis CE, Slovis TL. The ALARA concept in pediatric CR/DR - dose reduction in pediatric radiographic
exams. Pediatri Radiol 2004; 34 (Suppl 3):S162-S164.
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18. Strauss KJ, Poznauskis L. Practical applications of CR in pediatric imaging. App Radiol 2005; (suppl):S12S18.
19. Hufton AP, Doyle SM, Carty HM. Digital radiography in paediatrics: radiation dose considerations and
magnitude of possible dose reduction. Br J Radiol 1998; 71:186-199.
20. Khong PL, Ringertz H, Donoghue V, et al. ICRP publication 121: radiological protection in paediatric
diagnostic and interventional radiology. Ann ICRP 2013; 42:1-63.
21. Frantzen MJ, Robben S, Postma AA, Zoetelief J, Wildberger JE, Kemerink GJ. Gonad shielding in
paediatric pelvic radiography: disadvantages prevail over benefit. Insights Imaging 2012; 3:23-32.
22. Wolbarst AB, Karellas A, Krupinski EA, Hendee WR. Advances in Medical Physics. Vol 3; ; 2010.
23. Kwan AL, Seibert JA, Boone JM. An improved method for flat-field correction of flat panel x-ray
detector. Med Phys 2006; 33:391-393.
24. Seibert JA, Boone J, Lindfors KK. Flat-field correction techniques for digital detectors, Proc. SPIE
3336. Medical Imaging 1998; 348.
25. Prokop M, Neitzel U, Schaefer-Prokop C. Principles of image processing in digital chest radiography. J
Thorac Imaging 2003; 18:148-164.
26. Bomer J, Wiersma-Deijl L, Holscher HC. Electronic collimation and radiation protection in paediatric
digital radiography: revival of the silver lining. Insights Imaging 2013; 4:723-727.
27. American College of Radiology. ACR-AAPM-SIIM practice parameter for electronic medical
information privacy and security. Available at:
http://www.acr.org/~/media/419A8512DBDB4FDE99EC75B3C68B01CF.pdf. Accessed March 2, 2016.
28. National Electrical Manufacturers Association. Digital imaging and communications in medicine
(DICOM) Part 14: grayscale standard display function. Available at:
http://dicom.nema.org/Dicom/2011/11_14PU.PDF. Accessed June 27, 2016.
29. American Association of Physicists in Medicine. Assessment of display performance for medical
imaging systems. AAPM On-Line Report No. 3, Task Group 18 Report. Available at:
http://www.aapm.org/pubs/reports/OR_03.pdf. Accessed August 10, 2016.
30. American College of Radiology. ACR-AAPM-SIIM practice parameter for determinants of image
quality in digital mammography. Available at:
http://www.acr.org/~/media/5D883E5F6A694C8B8186378B76398837.pdf. Accessed March 2, 2016.
31. American College of Radiology. ACR practice parameter for communication of diagnostic imaging
findings. Available at: http://www.acr.org/~/media/C5D1443C9EA4424AA12477D1AD1D927D.pdf.
Accessed March 2, 2016.
32. Acceptance Testing and Quality Control of Photostimulable Storage Phosphor Imaging Systems. College
Park, Md: American Association of Physicists in Medicine; 2006. AAPM Report 93; Task Group 10.
33. Jones AK, Heintz P, Geiser W, et al. Ongoing quality control in digital radiography: Report of AAPM
Imaging Physics Committee Task Group 151. Med Phys 2015; 42:6658-6670.
*Practice parameters and technical standards are published annually with an effective date of October 1 in the
year in which amended, revised or approved by the ACR Council. For practice parameters and technical standards
published before 1999, the effective date was January 1 following the year in which the practice parameter or
technical standard was amended, revised or approved by the ACR Council.
Development Chronology for this Practice Parameter
2007 (Resolution 42)
Amended 2009 (Resolution 11)
Revised 2012 (Resolution 37)
Amended 2014 (Resolution 39)
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APPENDIX A
Glossary
For additional definitions, see the ACR–AAPM–SIIM Technical Standard for Electronic Practice of Medical
Imaging [4].
1. Analog signal - a form of information transmission in which the signal varies in a continuous manner and is
not limited to discrete steps
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2. Bit (binary bit) - the smallest unit of digital information that a computing device handles. It represents off or
on (0 or 1). All data in computing devices are processed as bits or strings of bits.
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3. Bit depth - the number of bits used to encode the signal intensity of each pixel of the image
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4. Charge-coupled device (CCD) - a photoelectric device that converts light information into electronic
information. CCDs are commonly used in television cameras and image scanners and consist of an array of
sensors that collect and store light as a buildup of electrical charge. The resulting electrical signal can be
converted into digital values and processed in a computer to form an image.
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5. Digital signal - a form of information transmission in which the signal varies in discrete steps, not in a
continuous manner
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6. Exposure class - similar to the term “speed” used with SF systems. Exposure class is used to describe the
nominal radiation exposure required to obtain a proper radiograph. The new term is used instead of speed to
reflect the significantly different energy response that digital detectors have when compared to SF systems.
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7. Exposure indicators - a quantitative method to estimate the nominal incident radiation exposure required to
obtain a proper radiograph. This is a manufacturer-dependent value. Fuji CR uses the sensitivity number (S
number), a value that is similar to SF speed and inversely related to incident exposure. Agfa CR uses lgM, the
log of the median exposure determined from the segmented area on the imaging plate, which increases
logarithmically with the incident exposure. Kodak CR uses exposure index, a value that represents the relative
measure of the X-ray exposure in the segmented, anatomical regions of the image and increases
logarithmically with the digital values in the image. Konica CR uses S value, a value similar to the S number
with similar relationships to incident exposure, but estimated and calculated in a different manner compared
with Fuji. Imaging Dynamics (a DR company) uses f-number, a relative value based upon the same concept
as photography in describing relative light intensity ranges, where in this situation, negative values represent
lower exposures and positive values represent higher exposures than the desired “nominal” exposure. Other
manufacturers have their own unique exposure value estimates. Users of a particular digital system must
understand the meaning of the incident exposure index in order to determine that the exposure was
appropriate. The manner in which the vendor identifies the parts of the image that have received direct X-ray
exposure or are collimated has an effect on the calculated exposure index and may lead to errors.
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8. Exposure latitude - the range between the minimum and maximum exposures that will produce an acceptable
range of densities for diagnostic purposes. Furthermore, it is considered the “margin for error in setting a
proper technique.” Exposure latitude is distinguished from the term “latitude” which is defined similarly as
“the range of X-ray exposures that deliver ODs in the usable range.” Thus, for the same screen-film detector,
the exposure latitude is necessarily a smaller ratio than the latitude, because the exposure latitude takes into
account the full extent of X-ray exposures and corresponding densities within the range. Similarities in these
2 terms lead to errors in communication between technologists, medical physicists, and radiologists.
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9. Fill-factor - the ratio of the active charge collection area to the total physical space occupied by the detector
element. Digital flat-panel detectors with better resolution (smaller del dimension) often have a lower fillfactor and poorer charge collection efficiency.
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10. Lookup table (LUT) - a table used to map image index numbers to output display values on a digital device
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11. Speed class - the concept of conventional screen-film speed (eg, 100, 200, 400, 600, 800) applied to the
incident exposure that a digital radiography device operates to produce an image of “acceptable” clinical
image quality. The speed class for a digital radiography device depends on the device itself (how efficiently
X-rays are absorbed and converted into a useful signal), the system gain adjustment (how much amplification
is applied to the signals prior to digitization), and the examination requirements (how much exposure is
required to achieve appropriate image quality; eg, extremity radiographs are typically acquired with a 100
speed class setting, whereas chest x-rays are typically acquired with a 200 to 400 speed class setting).
Operation of a system at a higher speed class requires less exposure to the patient but produces higher
quantum mottle (noise) and lower SNR in the image. (Also see “exposure indicators”)
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