Download Scott D. Steenburg, MD - Indiana Institute for Biomedical Imaging

Effect of Iterative Reconstruction Techniques
on Trauma Computed Tomography Image
Quality
Scott D. Steenburg, MD
Methodist Hospital, Department of Radiology
1701 Senate Blvd Room AG-176
Indianapolis, IN 46202
1.27.2012
Table of Contents:
Study Schema
1.0
Background
2.0
Rationale and Specific Aims
3.0
Inclusion/Exclusion Criteria
4.0
Enrollment/Randomization
5.0
Study Procedures
6.0
Reporting of Adverse Events or Unanticipated Problems involving Risk
to Participants or Others
7.0
Study Withdrawal/Discontinuation
8.0
Statistical Considerations
9.0
Privacy/Confidentiality Issues
10.0 Follow-up and Record Retention
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1.0
Background
Multi-detector computed tomography (MDCT) technology has evolved
significantly over the past 10 years. MDCT can be used to generate high
resolution images of the entire body in seconds and has been shown to decrease
mortality, has high sensitivity, specificity and negative predictive value (Poletti
2004, Miller 2005) and has been shown to increase survival when integrated into
the comprehensive evaluation of the acutely injured patient (Huber-Wagner
2009). There has been a recent shift towards the non-operative management
(NOM) of patients with internal abdominal injuries (Fakhry 2000, Rutledge 1995,
Hunt 1996) with the desire to avoid non-therapeutic surgery. Thus evaluation of
hemodynamically stable blunt abdominal trauma patients with MDCT is the
currently accepted standard of evaluation and has been shown to identify
unexpected internal injuries (Salim 2006). Evaluation of trauma patients with
MDCT is typically initiated within minutes upon arrival in the trauma center. The
value of MDCT in the comprehensive evaluation of the acutely injured patient
cannot be overstated.
The high value of MDCT in the evaluation of acutely ill and injured patients has
resulting in its increased utilization. This increased use has led to growing public
concern about radiation exposure (Brenner 2007, McCollough 2009). There have
been recent significant efforts on the part of physicians and radiology governing
bodies to reduce radiation dose used in CT. The reduction of radiation dose in
MDCT however comes at a cost of decreased image quality due to increased
image noise. Thus, the goal is to reduce radiation dose by as much as possible
without affecting image quality. Several studies have demonstrated that
radiation dose can be decreased by as much as 50% without significantly
affecting diagnostic image quality (Prasad 2002, Ravenel 2001, Mayo 1995,
Nickoloff 2001).
One novel approach to improving image quality has been developed by Philips
Healthcare using a reconstruction technique called “iterative reconstruction”.
The software name is called iDose (Scibelli 2011). iDose is a reconstruction
technique to reduce image noise and thus improve image quality. It is intuitive
that radiation dose could therefore be lowered with preservation of image quality
with the application of iDose. Philips Healthcare claims that by using iDose
techniques, radiation dose can be lowered by up to 80% with improved
resolution by up to 68% (Scibelli 2011). However, the application of iDose to
CT images results in an image quality that has been described by some as
“smooth”, “plastic appearing”, “unnatural” and “artificial”, with some radiologists
at our institution suggesting that the application of iDose may reduce the ability
to detect small lesions, including low grade solid organ injuries. There are no
data to neither support nor refute these claims. Thus the purpose of this study
1.27.2012
is to investigate the affect of iDose on MDCT image quality in the setting of
trauma and radiologists’ ability to diagnose solid organ injuries.
2.0
Rationale and Specific Aims
MDCT has high sensitivity, specificity, accuracy and negative predictive value in
the setting of solid organ injuries, thus resulting in increased reliance and
utilization in the setting of acute trauma. Efforts have been made to reduce
radiation exposure from MDCT, however this comes at the expense of deceased
image quality. Application of iterative reconstruction techniques (iDose, Philips
HealthCare) may reduce image noise in dose reduced images, thus improving
image quality. However there is fear that the character of these images may
mask subtle lesions or injuries. To our knowledge, there have been no studies
investigating the effect of iDose on the ability of radiologists to diagnose solid
organ injuries. Methodist Hospital is a Level 1 trauma center in the Indiana
University Health System seeing approximately 3500 trauma patients each year.
iDose has recently been employed in the Radiology Department at Methodist
Hospital in an attempt to improve image quality, however the effect of iDose
application to trauma MDCT images has not been objectively measured. We are
thus well positioned to make significant contributions in this area of trauma and
radiology research.
3.0
Inclusion/Exclusion Criteria
Inclusion:
 Age > 18 years
 Blunt and/or penetrating trauma
 Hemodynamically stable patients
 No peritoneal signs on exam as determined by the attending trauma
surgeon
 No indications for immediate surgery as determined by the attending
trauma surgeon
Exclusions
 Age< 18 years
 Pregnant patients
 Hemodynamically unstable patients
 Positive peritoneal signs on exam as determined by the attending trauma
surgeon
 Indications for immediate surgery as determined by the attending trauma
surgeon
1.27.2012
4.0
Enrollment/Randomization
With a waiver of consent will be in place for patients that will be imaged with
MDCT as determined by the attending trauma surgeon using existing standard of
care. This waiver will be present because the scanner only holds images up to
48 hours and the severity of the patients. There will be no change to accepted
patient management as a part of this study. Thus all trauma patients who
undergo imaging with MDCT will be automatically enrolled.
5.0
Study Procedures
We will retrospectively apply iDose reconstruction algorithm to trauma chest,
abdomen and pelvis CT scans that are acquired during the routine imaging
evaluation of acute trauma patients at IU Methodist Hospital. Patient selection
for imaging and to what extent will be determined by the attending trauma
surgeon based on their clinical assessment. iDose of various levels (i2, i4, i6 and
i7) will be applied to the standard image reconstruction technique (Filtered Back
Projection or FBP) with all other routine image reconstruction parameters
remaining constant as per routine. The FBP, i2, i4, i6 and i7 images will then be
sent to Research Picture Archiving and Communication System (PACS) where the
images will be anonymized and randomized. Images sent to Research PACS will
be separate from routine clinical workflow. Patients with and without solid organ
injuries will be identified by the Principle Investigator (PI). Cases with various
levels of iDose with or without internal injuries will be anonymized and
randomized. Radiologists will then review the images, blinded to the
reconstruction parameters and presence or absence of an internal injury, to
assess image. The radiologist diagnostic confidence will be measured on a 5
point Likert scale (1 – definitely no injury, 2 – unlikely to have injury, 3 –
indeterminate for injury, 4 – likely to have injury, 5 – definite injury). If an injury
is determined to be present, the radiologist will assign an injury grade using the
American Association of Surgery in Trauma (AAST) Solid Organ Injury Scale
(Moore 1989, Moore 1994).
6.0
Reporting of Adverse Events or Unanticipated Problems involving
Risk to Participants or Others
iDose will be applied retrospectively to images created in the process of routine
clinical management. Standard of care will not be altered. Potential adverse
events include known adverse events that may occur in the process of acquiring
CT images, such as intravenous (IV) contrast infiltration at the IV insertion site
and IV contrast allergic reaction. These are well known potential risks of MDCT.
This study will not alter these inherent risks in any way.
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7.0
Study Withdrawal/Discontinuation
The study will be concluded when least 500 cases patients are evaluated.
8.0
Statistical Considerations
Data will be collected on a spreadsheet and analyzed using the appropriate
statistical analysis software to determine the sensitivity, specificity, negative
predictive value, positive predictive value, and accuracy of MDCT in the detection
of internal injuries using the final radiology attending report as the reference
standard, and operative findings when available. The differences in the ability to
detect solid organ injuries using the different iDose levels will be calculated.
Other analyses may be performed dependent on the results and in consultation
with biostatistics personnel.
9.0
Privacy/Confidentiality Issues
The research database generated will be accessible only to the Principle
Investigator (PI) and will be stored on a password protected computer and
stored in a room under lock and key.
10.0 Follow-up and Record Retention
The study will be considered active until data analysis is complete and any
manuscripts are accepted for publication, if any.
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