Radiation safety and CT dose PARM AUTUMN SYMPOSIUM October 6 & 7, 2011 Radiation safety and CT dose Margaret “Peggy” Blackwood, MS, DABR System Director, Radiation Physics Radiation Safety Officer West Penn Allegheny Health System

Radiation safety…we’ve come a long way

Ct…we’ve come a long way Over 1 hour per head sca 16cm of Z-axis coverage allows an entire CT scan of the head to be performed in a single 0.75 second rotation, perfect for trauma and congenital follow ups in children at 20% lower dose.

CT Growth Single largest source of radiation to US population 80 M CT/yr* 1 in 5 7M ped CT/yr* 10% growth/yr *one phase Single largest source of radiation to US population Brenner D, Hall E. N Engl J Med 2007;357:2277-2284

POPUlation DOSES MEDICAL IMAGING ~ DOUBLED BACKGROUND 1980 2006 Radiology, V 253, #2, Nov 2009

Benefits…. And risks Stochastic Deterministic Cell mutation Cancer No threshold; uncertainties below 100 mGy (10 rads) Linear relationship of risk with dose Deterministic Cell death Skin effects and cataracts Threshold doses ~1-2 Gy (100-200 rads)

Stochastic Risks Review Article Computed Tomography — An Increasing Source of Radiation Exposure David J. Brenner, Ph.D., D.Sc., and Eric J. Hall, D.Phil., D.Sc. N Engl J Med, Volume 357(22):2277-2284, Nov 29, 2007 CT organ doses in range for which there is direct evidence of a statistically significant increase in risk of cancer

DETERMINISTIC EFFECTS Brain perfusion studies 3-7Gy (300-700 rads)

Pediatric CT doses 2001-Society for Pediatric Radiology (SPR) “ALARA Conference Proceedings. The ALARA Concept in Pediatric CT-Intelligent Dose Reduction” 2002-National Council on Radiation Protection and Measurements (NCRP) Conference on CT Dose

Conclusions of early CT conferences Excess cancer incidence in those exposed to radiation doses comparable to CT dose levels Small but statistically significant excess of cancer mortality over an individual’s lifetime Children are more sensitive to radiation than middle-aged adults by factor of 10; girls are more sensitive than boys Small risk per CT multiplied by large number of CT exams is public health issue, particularly in children

Lifetime risk of cancer

Conclusions of early CT conferences CT dose reduction important but must maintain acceptable diagnostic image quality Appropriateness of study Adjust CT doses to patient size (not fixed mA) Automatic dose reduction methods in CT scanners Standardize CT protocols; periodic review Dose reporting information CT exams Develop CT accreditation and QC programs

Ct image quality and dose Contrast-to-noise (CNR) Noisier image as dose reduced Loss of low contrast detectability

Conclusions of early CT conferences No consensus regarding single expression of dose Effective dose Organ dose CT dose index (CTDI) Dose length product Dissemination of information and education regarding risks and need for CT dose reduction

Alliance for Radiation Safety in Pediatric Imaging (“ALLIANCE”) 2008-Founded SPR, AAPM, ACR, ASRT 60+ organizations; 750,000 medical imaging professionals Promotes radiation protection for children Awareness Education Advocacy-based social marketing campaign: Image Gently

Image gently (pedrad.org/associations/5364/ig) Tests/Procedures CT Fluoroscopy Interventional Radiology Nuclear Medicine What can I do? Parents Radiologist Pediatricians Radiologic technologists Medical physicists

Image gently (pedrad.org/associations/5364/ig) What can I do? – Radiologists Comprehensive Background & Guidance Document Review of pediatric CT dose and strategies to manage radiation dose “Medical Radiation in Children”-powerpoint Image-Gently Web-based Practice QI Program Articles and Resources How to Develop CT Protocols for Children

ED Visits with CT under age 18

Image gently (pedrad.org/associations/5364/ig) What can I do? – Technologists On-line educational modules CT Practice Standards The Increasing Use of CT and its Risks Patient Dose from CT - Literature Review* ASRT White Paper: Computed Tomography in the 21st Century: Changing Practice for Medical Imaging and Radiation Therapy Professionals*

ASRT White paper: CT in the 21st century 2007-Consensus Conference Increasing use of CT technology is changing practice faster than educational institutions, vendors, medical providers and regulators expected Medical imaging professionals need more education in CT technology, including operation, application and dose optimization to ensure patient safety Challenges: insufficient educational programs, educated RTs in CT, education and training of entry level and experienced CT techs

Image wisely (imagewisely.org) Radiation Safety in Adult Medical Imaging Sponsored by aaom, acr, rsna, asrt

Image wisely (imagewisely.org) Sections for imaging professionals: physicians, RTs and medical physicists; referring practitioners and patients Take the “Image Wisely” pledge Educational sections ACR Appropriateness Criteria Download for mobile devices American Imaging Management Patient Safety: Ask AIMEE (interactive patient exposure calculator) Sponsored by aaom, acr, rsna, asrt

Image wisely (imagewisely.org) Patient Medical Imaging Record Sponsored by aaom, acr, rsna, asrt

Image wisely (imagewisely.org) Education, resources and links to websites CT Equipment: Operation, Performance CT Protocols Design methodologies Protocols from other sites ACR Appropriateness Criteria Online communities for CT tech questions and info Sponsored by aaom, acr, rsna, asrt

CT Protocol development & QA Establish set CT protocols for each indication by scanner, to optimize image quality and dose Vendor protocols are not optimized Begin with most frequently performed exams Include all aspects of exam, e.g. patient positioning, nursing instructions, exam parameters, reconstruction/reformatting instructions, CTDI and DLP reported values Protocol team(s) should include radiologist(s), CT technologist(s), physicist(s) and administrator(s)

CT Protocol development & QA Establish set CT protocols… Benchmark with published protocols and doses Develop consensus among radiologists regarding image quality requirements Establish ONE standard of care Fully understand and utilize automatic dose reduction techniques on CT scanner: Establish criteria for automatic dose reduction parameters, e.g. reference mAs, noise index, etc.

CT Protocol development & QA Develop policy and procedure for use of reviewed and approved CT protocols radiologists should not request and technologists should not manually modify approved CT protocols Develop a process to regularly review CT protocols to ensure they have not been modified and cannot be improved further

How to develop CT protocols for children Abd-baseline kVp=120 mA=200 Time=0.5s Abd Pitch=1 Th Pitch=1 PA thickness (cm) Approximate age Abdomen Thorax mAs RF Est mAs 9 Newborn 0.43 43 0.42 42 12 1 yr 0.51 52 0.49 49 14 5 yr 0.59 59 0.57 57 16 10 yr 0.66 66 0.64 64 19 15 yr 0.76 76 0.73 73 22 Sm adult 0.90 90 0.82 82 25 Med adult Baseline 100 0.91 91 31 Lg adult 1.27 127 1.16 116 RF=Reduction factor; Est mAs = Baseline *RF

Ct dose metrics

Ct dose metrics

Ct dose metrics

ACR CTDIv Pass/Fail & Reference Doses CT dose metrics CTDIv Accounts for beam width, detector configuration and pitch ACR CTDIv Pass/Fail & Reference Doses CT Exam CTDIv (mGy) Pass/Fail Reference Level Adult Head 80 75 Adult Abdomen 30 25 Ped Head (1 y.o.) To be determined Ped Abd (5 y.o., 40-50#) 20

Ct dose metrics CTDIvol is NOT Patient Dose Limitations Reference standard for radiation output of CT Limitations Multi-detector (MDCT) wider beam Phantom shorter than patient torso Underestimation of scattered radiation as much as 40% Not valid when table does not move, e.g. brain perfusion or wide cone-beam systems

Ct dose metrics CTDIvol Displayed on scanner console PRIOR to scan Allows operator to confirm proper protocol in use Included in DICOM “dose report” or “patient dose report”; reinforcing incorrect belief that CTDI is a measure of patient dose Patient dose is directly dependent of size and shape of the patient

Ct dose metrics CTDIvol Displayed on scanner console PRIOR to scan Allows operator to confirm proper protocol in use Included in DICOM “dose report” or “patient dose report”; reinforcing incorrect belief that CTDI is a measure of patient dose Patient dose is directly dependent of size and shape of the patient

Ct dose metrics Size-specific dose estimate Conversion factor based on patient size to estimate patient dose (mGy) Organ dose estimation not possible with this method Effective dose (mSv) cannot be estimated

Ct dose metrics Effective diameter Calculated Lateral + AP Lateral or AP only Eff dia = (APxLAT)1/2 Look up tables by effective diameter method and CTDI phantom utilized

Ct dose metrics 32 cm PMMA phantom ACR report 2004

Ct dose metrics Effective dose (mSv) Absorbed dose to each organ Tissue-weighting factor-accounts for radiosensitivity of each tissue irradiated Whole body effective dose equivalent Effective dose=S(wT*organ equivalent dose) wT = tissue weighting factor

Tissue Weighting Factors ICRP 26 (1977) ICRP 60 (1991) ICRP 103 (2007) Gonads 0.25 0.20 0.08 Red bone marrow 0.12 Lung Colon Stomach Breast 0.15 0.05 Bladder 0.04 Liver Esophagus Thyroid 0.03 Skin 0.01 Bone surface Brain Salivary glands Remainder 0.30

Stochastic Risk Estimates Statistically significant increase in cancer at doses > 10 mSv Radiation risk: 1/1000 per 10 mSv Averaged across all ages and genders Normal background risk of cancer:400/1000 Total increased risk: 401/1000

NEJM, Aug 2009, Fazel et al

Highmark Radiology Management Program https://prc.highmark.com/rscprc/hbcbs/pub Highmark Radiology Management Program Radiation Safety Awareness Program Highmark/NIA identify “at-risk” patients Dose Limit Threshold, equal to or greater than 50 mSv, patient’s cumulative radiation exposure based on Highmark claims data “a level that has been identified as causing a statistically (epidemiologically) significant increased risk of developing radiation-associated cancers

Radiation safety Awareness Program Goals Raise awareness regarding radiation exposure Risk v benefit Alternative studies How results of study will impact on patient management Identification of patient’s prior imaging studies Evaluate necessity of repeat studies Consider discussing information with patient

Radiation safety Awareness Program Physicians notified when preauthorization requested Offered NIA peer discussion Dose Limit Threshold Notification sent with authorization or adverse determination letter “Important Note: The patient’s level of radiation exposure does not impact the preauthorization or decision-making process for requested imaging studies.” Does not apply to patients with cancer diagnosis

TJC Sentinel Event Alert, Issue 47 (8/23/11) Radiation Risks of Diagnostic Imaging Right test Right dose Effective processes Safe technology Safety culture

TJC Sentinel Event Alert, Issue 47 (8/23/11) Alert focused on diagnostic imaging, NOT therapeutic radiation or fluoroscopy (i.e. CT) Addressing contributing factors to eliminate avoidable radiation dosing Activities that can help eliminate avoidable radiation doses 11 recommendations with 21 specific actions

TJC Sentinel Event Alert, Issue 47 (8/23/11) Comprehensive patient safety program, including education about dosing in imaging departments Training on how to use complex new technology Knowledge regarding typical doses Clear protocols that identify the maximum dose for each type of study 7 other recommendations…education, communication, equipment checks,…

TJC Sentinel Event Alert, Issue 47 (8/23/11) Right test Use of alternative non-ionizing tests Create and implement processes that enable radiologists to provide guidance to and dialogue with referring physicians regarding the appropriate use of diagnostic imaging using the ACR Appropriateness Criteria

TJC Sentinel Event Alert, Issue 47 (8/23/11) Right dose Adhere to ALARA Adhere to Image Gently and Image Wisely guidelines Provide reference doses, with ranges, to MDs and techs, based on anatomy, study purpose and pt size Radiologists should ensure that the proper dosing is in place for the patient being treated Annual or bi-annual protocol review Track doses from repeat exams; address & resolve Record dose/exposure in summary report of findings

TJC Sentinel Event Alert, Issue 47 (8/23/11) Effective processes Policies and procedures delineating staff responsible for approving changes to password protected protocols; for monitoring new developments; control of password by RS “group” P & P delineating physical RS measures; e.g. lead Expand RSO role to explicitly include patient safety and involve RSO in Patient Safety Committee

TJC Sentinel Event Alert, Issue 47 (8/23/11) Safe technology Organization-wide audit survey of rad equip; centralize quality and safety performance under physicist, RSO, RS group Qualified medical physicist to test all diagnostic equipment annually and review scanning protocols and doses Ensure QC and PM testing done; delineate responsibilities in writing Invest in technologies that optimize or reduce dose.

TJC Sentinel Event Alert, Issue 47 (8/23/11) Safety culture Promote safety culture for safe use of diagnostic radiation Additional recommendations Endorse national radiation dose tracking registry Encourage manufacturers to incorporate dosage safeguards into EMR and national dose registry Support stricter regulations to eliminate avoidable imaging and monitor the appropriateness of self-referred imaging studies

DOSE REDUCTION TECHNOLOGIES Detector advancements Axial Helical Multi-detector CT (MDCT) Automatic exposure control Z-axis modulation Angular and Z-axis modulation Dual source Iterative reconstruction methods (e.g. ASIR)

Graph shows typical scanner output level (expressed as volume CT dose index [CTDIvol]) for a routine abdominal CT examination from the 1980s, when xenon detectors were used, to 2004, when 64–detector row CT systems were introduced. Graph shows typical scanner output level (expressed as volume CT dose index [CTDIvol]) for a routine abdominal CT examination from the 1980s, when xenon detectors were used, to 2004, when 64–detector row CT systems were introduced. Data from the 1980s represent different scanner models in use during that period. Solid-state detectors were used on the systems represented here from 1988 onward. Until the mid-1990s, the typical image represented a 10-mm section of anatomy, and scans required several minutes to acquire. Much improved image quality is now obtained by using 3–5-mm section widths and scan times of 10–20 seconds. Hricak H et al. Radiology 2011;258:889-905 ©2011 by Radiological Society of North America

Automatic exposure control

DOSE REDUCTIONS IN CT ANGIOGRAPHY Graph shows dose reductions in cardiac CT angiography. Cardiac spiral CT was introduced into clinical practice around 2000 after the introduction of the four-section scanner. Electrocardiographically controlled milliampere (mA) modulation was introduced to clinical practice in about 2002, the step-and-shoot mode for cardiac imaging was introduced in about 2006, and dual-source spiral CT with high pitch was introduced in around 2009. For cardiac examinations that do not require images of the heart throughout the entire cardiac cycle, the radiation can be turned down with the use of tube current (milliampere) modulation, or off in the case of nonspiral scans. This is often done for phases of the cardiac cycle where the heart is moving fastest, when motion blurring or artifact would be most severe. (Image from reference 68). Hricak H et al. Radiology 2011;258:889-905 ©2011 by Radiological Society of North America

GOALS Medically necessary Least invasive modality Discussion of options between radiologist and referring MD Minimize study as appropriate “Right size” radiation dose Education for patients and medical personnel SIGN THE IMAGE GENTLY AND IMAGE WISELY PLEDGES! Radiation Safety in Adult Medical Imaging

PROGESS… CT doses 1/3 lower than a decade ago Expect 10-fold+ or more reduction in next few years ACR National Dose Registry-collect data on all CT exams