* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Learning objectives
Survey
Document related concepts
History of radiation therapy wikipedia , lookup
Medical imaging wikipedia , lookup
Brachytherapy wikipedia , lookup
Proton therapy wikipedia , lookup
Neutron capture therapy of cancer wikipedia , lookup
Nuclear medicine wikipedia , lookup
Backscatter X-ray wikipedia , lookup
Radiation therapy wikipedia , lookup
Radiosurgery wikipedia , lookup
Industrial radiography wikipedia , lookup
Radiation burn wikipedia , lookup
Center for Radiological Research wikipedia , lookup
Transcript
Image Gently, Pause and Pulse: Practice of ALARA in Pediatric Fluoroscopy Sue C. Kaste, DO1, 2 Marta Hernanz-Schulman, MD3 Ishtiaq H. Bercha, M.Sc. 4 St. Jude Children’s Research Hospital 2 University of Tennessee Health Science Center 3 Monroe Carell Jr. Children’s Hospital at Vanderbilt 4 The Children’s Hospital, Aurora, Colorado. 1 1 ALARA “As Low As Reasonably Achievable” General principle guiding radiation exposure Keep exposure to radiation dose as low as is possible for each procedure, while obtaining needed clinical information = Image Optimization 2 Primary Learning Objective Review pediatric fluoroscopic procedures understand the source of radiation understand methods to reduce radiation effect on image quality 3 Other Learning Objectives Fluoroscopy radiation units. Scope of pediatric fluoroscopic procedures Methods available for dose reduction clinical settings to apply dose reduction 4 Fluoroscopy Radiation Units Basic Radiation Quantities : Exposure & Exposure Rate Air Kerma & Air Kerma Rate 5 Fluoroscopy Radiation Units Radiation Measurement Quantities: Incident Air Kerma & Rate Entrance Surface Air Kerma & Rate 6 Fluoroscopy Radiation Units Risk Related Quantities: Absorbed dose Equivalent Dose Effective dose 7 Basic Radiation Quantities Exposure – expresses intensity of x-ray energy per unit mass of air. Units: Coulomb per kilogram (C/kg). Commonly used units are Roentgen or milli Roentgen, expressed as R or mR, respectively. 1 R = 2.58 x 10-4 C/kg Exposure rate identifies x-ray intensity per unit time. Commonly used units are R/min or mR/min. 8 Basic Radiation Quantities Air Kerma (K) – sum of initial kinetic energies of all charged particles generated by uncharged particles such as x-ray photons released per unit mass of air. Unit = Joule per kilogram, Commonly referred to as Gray/milli Gray (Gy or mGy). 1 Roentgen of exposure 8.7 mGy air kerma Air Kerma Rate quantifies air kerma per unit time and is written as, dK/dt, that is, incremental kerma per unit increment of time. 9 Measurement Quantities Incident Air Kerma (Ka,i)– is the air kerma from the incident beam along the central x-ray beam axis at the skin entrance plane. Only the primary beam is considered and the effect of back scattered radiation is excluded. Unit = Joule per kilogram, Commonly referred to as Gray/milli Gray (Gy or mGy). Incident Air Kerma Rate quantifies air kerma per unit time. It is usually measured as mGy/min. 10 Measurement Quantities Entrance Surface Air Kerma (Ka,e) – It is the air kerma from the incident beam along the central x-ray beam axis at the point where radiation enters the patient and the effect of back scattered radiation is included. Given as Ka,e = Ka,i x B B = Back Scatter Factor. Unit = Joule per kilogram, Commonly referred to as Gray & milli Gray (Gy or mGy). Incident Air Kerma Rate quantifies air kerma per unit time. 11 Risk Related Quantities Absorbed dose – energy deposited per unit mass of a material, in our case, within tissue. Initially measured as rads Current unit based on Systeme Internationale (SI unit) SI Unit of Absorbed Dose = Gray 1Gray (Gy) = 100 rad 1rad = 10 mGy 12 Risk Related Quantities Dose Equivalent – accounts for biological effect of type of radiation For example, difference in biological effect between , and radiation Radiation Weighting factor (wR) – scaling factor used , Xray wR = 1 (wR) = 20 SI Unit is Sievert 1 Sievert (Sv) = 100 rem 1 rem = 10 mSv 13 Risk Related Quantities Effective dose – accounts for radio-sensitivity of specific organs Includes A tissue weighting factor (wT) for each sensitive organ Each tissue included in the clinical examination (HT) Effective dose = wT x HT, () summed over all exposed organs. SI Unit is Sievert 1 Sievert (Sv) = 100 rem 1 rem = 10 mSv 14 Background Radiation Exposure Non-Medical Radiation Source Radiation Dose Estimate Equivalent Amount Background Radiation Natural background radiation 3 mSv Airline passenger (cross- 0.04 mSv country) 3mSv/year* 4 days * = estimate at sea level in US 15 Medical Radiation Exposures Medical Radiation Source Radiation Dose Estimate Chest x-ray 0.1 mSv Equivalent Amount Background Radiation 10 days Urinary tract fluoroscopy (VCUG) Continuous Mode* 0.45 – 0.59 mSv 2 months 0.05 – 0.07 mSv 1 week Optimized fluoroscope* * Ward et al Radiology 2008;249:1002 16 Practical Methods to Reduce Radiation Dose to Fluoroscopy Staff & Patients 17 Staff Protection 18 Reduce Radiation Dose: Staff Staff dose is due to scattered radiation Scattered radiation is directly proportional to Patient Dose Patient Dose Staff Dose 19 Staff Protection Well fitted lead apron (knees) Leaded glasses (with sides) Thyroid shield Lead gloves 20 Staff protection: Hands Keep hands out of the beam Collimate 21 Staff protection: Shields Lead shield on tower Do not turn your back to Xray beam if wearing front apron only 22 In summary: Have we…. … left our hands in the beam? … sacrificed personal safety for expediency? … turned our unshielded backs to the X-ray source? … unnecessarily prolonged exposure? … pushed away a protective barrier? 23 Patient Protection 24 Patient Protection Radiation dose is optimized when we use Least amount of radiation That delivers clinically adequate image quality Patient Positioning Proper patient positioning Make use of Inverse square law! Maximize distance between x-ray tube & patient Minimize distance between patient & Image Intensifier 26 Control Fluoroscopic Exposures Choose pulsed fluoroscopy Choose as short a pulse width as possible Typically 5 – 10 msec pulse width 27 Control Fluoroscopic Exposures Continuous fluoroscopy 30 pulses per second 33 msec pulse width Grid-controlled fluoroscopy e.g. 15 pulses / sec 10 msec pulse width 28 Control Fluoroscopic Exposures Increase filtration to reduce patient radiation dose Balanced by need for shorter pulse widths to freeze motion Interposition of Aluminum and variable thickness of Copper Removes low energy radiation that does not reach the image intensifier scattered within the patient adds radiation dose does not contribute to image 29 Control Fluoroscopic Exposures Remove anti-scatter grid whenever possible Removes scattered radiation Increased radiation dose Not necessary in small patients Avoid unnecessary magnification 30 Control Fluoroscopic Exposures Collimate to area of interest No need to radiate tissue that is not clinically pertinent 31 Control Fluoroscopic Exposures Use “last image hold” Whenever you need to inspect the anatomy, and do not need to observe motion or changes with time Use Fluoroscopy Store (FS) this method is ideal to convey and record motion, such as peristalsis, or show viscus distensibility, as in esophagram when you need information without excessive detail Fluoro-grab Exposure 32 Control Number of Images Choose appropriate, patient-specific technique Limit acquisition to what is essential for diagnosis and documentation PAUSE– Plan study ahead PAUSE- think # frames / second PAUSE – think magnification PAUSE – think Last Image Hold PAUSE – think Image Grab 33 Control Fluoroscopic Use Use fluoroscopic examination when there is a clear medical benefit. Use alternative imaging methods whenever possible US MRI 34 Special Pediatric Considerations Pediatric patient management more critical Increased radio-sensitivity, small size, longevity. Pediatric size Smaller patient leads to less scattered radiation There is an increased need for magnification 35 Institutional Strategies to Optimize Radiation Exposure Fluoroscopy 36 To Start: An in-house diagnostic medical physicist in pediatric hospitals is optimal. The physicist must have proper training and background in Medical Physics, such as CAMPEP accredited graduate and residency programs. Proper training is key 37 To Start: An Image Management committee, comprised of radiologists, technologists, administrators and medical physicists, under the direction of the department Chair, can be very helpful. • Responsible for optimizing radiation procedures. • Oversee the departmental QA/QC program. • Meet criteria for accreditation, e.g. ACR 38 To Start: Oversee purchase of capital equipment and periodic hardware and software upgrades. Staff training on state of the art technologies. Technologists, radiologists Equipment, safety, physics, radiation biology Compliance with applicable state and federal regulations. 39 Dosimetry Records Manage fluoroscopy parameters e.g., pulsed fluoroscopy, pulse rate, removable grid Record information related to patient radiation dose as displayed by the equipment: Cumulative Dose Area Product. Cumulative Air kerma/Skin Dose. 40 Summary PAUSE to properly plan and prepare for study Activate dose saving features of equipment No image exposures unless necessary Download image grab instead PULSE at lowest possible rate 41 References -Gelfand, D.W., D.J. Ott, and Y.M. Chen, Decreasing numbers of gastrointestinal studies: report of data from 69 radiologic practices. AJR Am J Roentgenol, 1987. 148(6): p. 1133-6. -Margulis, A.R., The present status and the future of gastrointestinal radiology. Abdom Imaging, 1994. 19(4): p. 291-2. -Page, M. and H. Jeffery, The role of gastro-oesophageal reflux in the aetiology of SIDS. Early Hum Dev, 2000. 59(2): p. 127-49. -Strauss KJ, Kaste SC. The ALARA (as low as reasonably achievable) concept in pediatric interventional and fluoroscopic imaging: striving to keep radiation doses as low as possible during fluoroscopy of pediatric patients—a white paper executive summary. Radiology 2006 240(3):621-622. -Ward VL, Strauss KJ, Barnewolt CE, Zurakowski D, Venkatakrishnan V, Fahey FH, Lebowitz RL, Taylor GA. Pediatric radiation exposure reduction and effective dose reduction during voiding cystourethrography. Radiology 2008 249:1002-1009. -Hall, E. and J. Amato, Radiobiology for the Radiologist. 2005: Williams & Wilkins. -Lederman, H.M., et al., Dose reduction fluoroscopy in pediatrics. Pediatr Radiol, 2002. 32(12): p. 844-8. -Ward, V., et al., Radiation exposure reduction during voiding cystourethrography in a pediatric porcine model of vesicoureteral reflux. Radiology, 2005. 235. -Boland, G.W.L., et al., Dose Reduction in Gastrointestinal and Genitourinary Fluoroscopy: Use of Grid-Controlled Pulsed Fluoroscopy. Am. J. Roentgenol., 2000. 175(5): p. 1453-1457. -Brown, P.H., et al., A multihospital survey of radiation exposure and image quality in pediatric fluoroscopy. Pediatr Radiol, 2000. 30(4): p. 236-42. -Strauss KJ. Pediatric interventional radiography equipment: safety considerations. Pediatr Radiol (2006) 36 (Suppl 2):126-135. -Hernanz-Schulman M, Emmons M, Price R. Radiation dose reduction and image quality considerations in pediatric patients. Radiology RSNA syllabus, November, 2006 42