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Kevin ODonnell Toshiba Medical Research Institute Michael F. McNitt-Gray, PhD, DABR, FAAPM Professor, Department of Radiology Director, Biomedical Physics Graduate Program David Geffen School of Medicine at UCLA 1

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Disclosures K.O. : Employee, Toshiba Corporation M.M-G: Institutional research agreement, Siemens AG Recipient research support Siemens AG Instructor, Medical Technology Management Institute. 2

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Learning Objectives 1) Understand integration challenges involved in Monitoring Radiation Exposure. 2) Learn about capturing dose information with the DICOM Radiation Dose SR (RDSR) standard. 3) Learn about managing RDSR objects with the IHE Radiation Exposure Monitoring (REM) Profile. 4) Learn how data such as "CT dose screens" from legacy systems can be ported into RDSR. 5) Learn about pre-scan dose pop-ups on the CT console defined by the MITA Dose Check standard and recent AAPM guidance on their use. 6) Learn how to specify the above features when purchasing and integrating Radiology Systems. 7) Learn about components of a dose management program such as protocol optimization, dose QA programs and participation in the ACR Dose Registry. 3

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Outline CT Dose Definitions MMG IHE REM, DICOM RDSR and Standards KO How to use dose information in practice - MMG 4

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CT Specific Dose Definitions Computed Tomography Dose Index (CTDI) & its cousins CTDI 100 CTDI w - weighted CTDI vol Dose Length Product (DLP) Dose Reports

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CTDI CTDI is an Index CTDI is dose in a phantom CTDI has LOTs of good uses: It is a good measure of scanner output It is a good index when comparing protocols and technical parameter settings It is a very good indicator of how scanner output is being adjusted with patient size (think peds protocols) 6

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CTDI But CTDI has some limitations (we said it was an index) Ex: CTDI is not a direct measure of patient dose (more on that later) 7

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CTDI Phantoms Body (32 cm diam), Head (16 cm diam) Holes in center and at 1 cm below surface

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CTDI defined CTDI Does Represent: Average dose in a phantom along the z direction at a given point (x,y) in the scan plane over the central scan of a series of scans when the series consists of a large number of scans separated by the nominal beam width (contiguous scanning)

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CTDI 100 CTDI 100 Measurements are done: In Both Head and Body Phantoms with 100 mm ion chamber At isocenter and at least one peripheral position in each phantom 20 mGy 10 20 Body 60 mGy 60 Head Some typical CTDI 100 values

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CTDI w CTDI w is a weighted average of center and peripheral CTDI 100 to arrive at a single descriptor CTDI w = (1/3)CTDI 100,center + (2/3)CTDI 100,peripheral

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CTDI vol Calculated, not measured directly Based on CTDI w, but accounts for pitch CTDI vol = CTDI w / Pitch

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CTDI vol in Context of AEC When Tube current modulation is used: CTDI vol reported is based on the average mA used throughout the scan

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Scan where Tube Current Modulation was used Blue Curve Represents actual instantaneous mA Red Curve Represents avg mA for each image Yellow Curve Represents avg mA over entire scan Overall avg is used for CTDIvol reported in Dose Report

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DLP defined Dose Length Product is: CTDI vol * length of scan (in mGy*cm) Found in most Dose Reports Includes any overscan (extra scanning for helical scans)

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CTDI vol and DLP CTDI vol is reported on the scanner and in dose reports CTDI vol is Dose to one of two phantoms (16 or 32 cm diameter) CTDI vol is a good descriptor of scanner output And can be a good indicator of how output is adjusted for patient size Think peds protocols here. Larger patients SHOULD have a larger CTDI vol

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Standards & Tools 17

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Headers & Screen Shots Useful but limited Missing details Not machine-readable Duplication issue Size issue 18

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DICOM RDSR 19 Radiation Dose Structured Report Object

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20 DICOM Dose Reports SR Objects DICOM Structured Reports Easily ingested (and regurgitated) by PACS Granularity : Irradiation Event & Accumulated Dose over Study, Series Templates : CT, Projection X-Ray (Mammo, Fluoro) DR/CR (Soon), PET/NM (WIP) Not yet addressed: RT

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21 Key Measurements CT Dose DLP, CTDIvol, kVP, mA, sec Effective Dose [ Optional; Reference estimation method ] Projection X-Ray Dose DAP, Dose@RP, kVP, mA, sec Fluoro Dose, Fluoro Time [CR/DR: Exposure Index, Deviation Index] Mammography Dose AGD, Entrance Exposure@RP, kVP, mA, sec Compression, Half Value Layer ftp://medical.nema.org/medical/dicom/2011/11_16pu.pdf

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22 Other Details in Dose SR Full Patient / Order / Study Details Unique ID for each Irradiation Event Equipment ID, Ordering Doc, Performing Tech Patient Size, Orientation, Anatomy Imaged Imaging Geometry X-Ray Filtering & Collimation Details Anode Target Material Calibration, Phantom, Dosimeter, Patient Model

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IHE REM Profile 24 Radiation Exposure Monitoring some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 Numer 12.2 14.5 9.5 10.9

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25 IHE in One Slide IHE helps vendors implement & test functions that span multiple systems Profiles are implementation guides how to use existing standards to address a specific problem scenario Connectathons are test events managed testing of Profile implementations IHE helps users purchase & integrate multi-system solutions list required IHE Profile support in RFPs

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26 IHE Radiation Exposure Monitoring Profile some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 National Registry Archive Dose Information Reporter some text: # Numerical Details 12.2 14.5 11.8 7.6 Outlier: # Performing Phys. Over Target: 12.2% some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 Numer 12.2 14.5 9.5 10.9

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27 Using SR Dose Reports Radiation QA Periodically Query / Retrieve Reports from Archive Set policies/standards and flag deviations Set goals for improvement and track progress Implement protocol changes and compare difference in dose Patient Impact Evaluation e.g. if Patient identified as pregnant post-facto Dose Mapping Store data in realtime from Modality to Mapping Workstation

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28 Using SR Dose Reports National Registries Anonymize and submit Dose Reports to Registry Compile Population Risk Estimations Derive Dose Reference Levels (DRLs) Provide Site-Site Comparisons Individual Dose Record Collect Dose Reports over time Clinical Trials Collect Dose together with Images Demonstrate both improved detection & reduced dose

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Legacy Dose Extractors 29 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9

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Legacy Extractor What if you cant get REM? Extractors create (partial) REM objects Based on OCR of dose screens Based on image header contents Based on MPPS Likely incomplete but still useful Allows use of uniform infrastructure (RDSR) Current focus: CT, some XA

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Example Extractors Open Source Dose Utility - dclunie.com by David Clunie (PixelMed) Radiance - radiancedose.com by Tessa Cook (Hospital of U of Pennsylvania) GROK dose-grok.sourceforge.net by Graham Warden (Brigham and Women's Hospital) Also Valkyrie (considering open source) by George Shih (Weill-Cornell) ACR Triad Site Server (included in ACR participation) by Mythreyi Chatfield (ACR)

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ACR DIR 32 Dose Index Registry

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ACR Dose Index Registry nrdr.acr.org Open to facilities worldwide Anonymized data submission (via IHE REM or legacy extractor) Provides periodic reports Dose statistics Site Comparisons Modest annual participation fee 33

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ACR Activity Tracking practice Understand current dose patterns Provide basis for establishing DRLs Not tracking patient/longitudinal Procedure Naming Issue Comparison requires consistent naming Local consistency vs National consistency ACR maps to Radlex Playbook 34

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MITA XR-25 35 CT Dose Check Dose Notification Predicted DLP (981 mGy-cm ) Exceeds Threshold

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MITA CT Dose Check Initiative Goals Enhance dose awareness (CTDI/DLP) Help to avoid excessive radiation events Provide data to sites for QA MITA has published the standard (XR-25)* Manufacturers worked to ensure Uniformity Speed of implementation Breadth of deployment *Available at: http://www.nema.org/stds/xr25.cfm

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Dose Notification Pop-up message Notifies technologist that dose for the current scan element will exceed a trigger value Tech may: confirm and proceed, or go back and adjust scan parameters System records audit trail Predicted dose, Notification value, Date/time, diagnostic reason, etc. Clinical sites set values that will trigger a notification Can set DLP and/or CTDI vol values for each scan element e.g. head without contrast Defined by the clinical site for their patient population

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Dose Alert Pop-up message Alerts technologist cumulative dose for current study will exceed a trigger value: CTDI vol (summed at each patient location) DLP (summed over the current study) Tech may: enter their name, (& a password if configured), confirm and proceed, or go back and adjust scan parameters Clinical sites set values that will trigger an alert Can set DLP and/or CTDI vol values System must allow at least one global value System tracks accumulated CTDI vol at each patient location & accumulated DLP System checks predicted accumulated dose indices when protocols are saved & when scans are ready

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Default Values The FDA has suggested an alert value for CTDIvol of 1000 mGy, AAPM suggested notification values Can be changed at local site 39

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Audit Trails Pop-up Overridden? System must record: Dose Notification Predicted dose, Notification value, Date/time, Diagnostic reason Dose Alert Predicted dose, Alert value, Date/time, Diagnostic reason, Operator name RDSR has fields to record all these details May choose to record even if not overridden Triggers vs DRLs 75 th percentile -> popups on 25% of scans See AAPM guidance

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Implementation Progress IHE REM Testing: IHE Connectathon http://connectathon-results.ihe.net Product: IHE Integration Statement http://product-registry.ihe.net DICOM RDSR Product: DICOM Conformance Statement NEMA XR-25 Vendors commitment; some products already released 41

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Takeaway Data Collection New/recent Modalities IHE REM / DICOM RDSR to capture dose data Legacy strategies Dose extractors to generate RDSR data Analysis IHE REM Dose Information Reporter for local analysis ACR Dose Registry to compare to benchmarks Prevention CT Dose Check for configurable pre-scan alerts

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Things to Implement in Practice Turn On/Upgrade to get these Informatics Tools Make sure CTDIvol is displayed on all of your CT scanners Can be turned off, so make sure Make sure Patient Protocol pages are sent to PACS Not always automatically sent to PACS, so make sure RDSR (may require software upgrade, so check) MITAs Dose Check (also may require software upgrade) Consider joining ACRs Dose Index Registry 43

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Things to Implement in Practice Review CT protocols All if possible, but at least top 10 highest dose and/or usage One key question Fewer Protocols? Or More Protocols?: Build a basic protocol that is inclusive and ask techs to adapt (in real time) at scanner Build protocols for each possible situation and have them listed separately on the scanner (e.g. peds 16kg) Some combination of these two 44

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Things to Implement in Practice What to review Review Indications and Requirements for Exam What do you need to see? What amount of noise can you tolerate? Technical parameters (kVp, mAs, pitch, etc.) Examine CTDIvol and DLP values for protocols Determine number of phases necessary for indication Are both pre- and post-contrast necessary on all patients? Are different enhancement phases necessary (arterial/venous)? 45

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ACR CT Dose Reference Values Based Solely on CTDI vol (not DLP) Two levels: Reference level and Pass/Fail level Exam Ref Level Pass/Fail Level Adult Head*75 mGy80 mGy Adult Abdomen*25 mGy30 mGy Pediatric (5 y/o) Abd*20 mGy25 mGy Pediatric Head*45 mGyNone (yet) All values pertain to a single phase, NOT cumulative from multi-phase exams Adult Head, peds abd and peds head are based on 16 cm phantom

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AAPM Protocols For All Manufacturers Brain Perfusion already posted on AAPM public website Coming Soon Routine Head Routine Chest Routine Abdomen Routine Cardiac Not Meant to be optimal, but a good starting point 47

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Things to Implement in Practice Review Usage Ex.: Summary Statistics from ACR Dose Index Registry Use tools to help identify high dose exams and outliers Understand reasons for high dose values Large Patient (for Body exams) Multiple Phases Ensure Compliance with Protocols 48

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Things to Implement in Practice Reporting Dose in Patient Record and Radiology Reports? Why are you going to do this? Required by State Law (e.g. CA)? Its the right thing to do? 49

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Limitations of CTDI vol Some things you should know before you start reporting dose in patient records CTDI vol is Dose to one of two phantoms (16 or 32 cm diameter) CTDI vol is a good descriptor of scanner output And can be a good indicator of how output is adjusted for patient size Think peds protocols here. Larger patients SHOULD have a larger CTDI vol 50

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Limitations of CTDI vol CTDI is not a direct measure of patient dose See McCollough et al, Radiology. 2011 May;259(2):311-6. PMCID: PMC3079120 Need other information (such as patient size) to provide accurate estimate of individual patient dose

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CTDI vol and Patient Size For most body exams, it is proper to adjust scanner output for patient size Larger output for larger patients Lower output for smaller patients Larger patients will typically have a larger CTDI vol This is not a bad thing, it reflects proper adjustments in tube output 52

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Scenario 1: No adjustment for patient size 32 cm phantom CTDI vol = 20 mGy The CTDI vol (dose to phantom) for these two would be the same 100 mAs

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Scenario 2: Adjustment for patient size 32 cm phantom CTDI vol = 10 mGy CTDI vol = 20 mGy The CTDI vol (dose to phantom) indicates larger patient received 2X dose 50 mAs 100 mAs

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Did Patient Dose Really Increase ? For same technical factors, smaller patient absorbs more dose Scenario 1: CTDI is same but smaller patients dose is higher Scenario 2: CTDI is smaller for smaller patient, but patient dose is closer to equal for both

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Limitations to CTDI CTDI vol does not account for patient size Even though you may see different values for patients of different size; this is because scanner output is being (usually properly) adjusted for patient size AAPM Report 204 describes a method to take into account patient size The Size Specific Dose Estimate (SSDE)

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AAPM Report 204 Report also describes coefficients based on Lateral Width (from PA CT radiograph) and AP thickness (from Lat CT radiograph)

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CTDI vol and Peak Dose (Perfusion Scans) CTDI vol is a weighted average of measurements made at periphery and center of cylindrical phantom Defined to reflect dose from a series of scans performed w/table movement From Bauhs et al, Radiographics. 2008 Jan-Feb;28(1):245-53

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CTDI vol and Peak Dose (Perfusion Scans) CTDI vol is a weighted average of measurements made at periphery and center of cylindrical phantom Defined to reflect dose from a series of scans performed w/table movement Is not patient dose (not even skin dose) Typically OVERestimates skin dose in cases where scan is performed with no table movement (e.g. perfusion scans) See article by Zhang et al, AJR Feb 2012 (in press).

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CTDI vol and DLP Need other information such as patient size, body region, clinical indication to determine if scan was done correctly or Alara

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CTDI vol Not patient dose and by itself can be misleading Should be recorded with: Description of phantom size (clarify 16 or 32 cm diameter) Description of patient size (Lat. Width, Water Eq. Diam) Description of anatomic region If CTDI vol is recorded without any patient size information, then some disclaimer could be added: The dose values reported here are an estimate and represent dose to a standard phantom; they do not take into account patient factors such as patient size

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Still want/need to Report Dose? Lets look at what is available to report 62

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Which Phantom Was Used for CTDI Currently: ALL HEADS (Adult/Peds) 16 cm phantom ALL ADULT BODY 32 cm phantom PEDS BODY (CAUTION!!!!): PEDS BODY (CAUTION!!!!): Siemens, Philips: report based on 32 cm phantom Toshiba and GE**: report 16 OR 32 cm (depends on SFOV or patient size) CTDI vol s differ by a factor of approx 2.5 So, previous example, CTDI vol,32 = 1.71 mGy If report used 16 cm phantom, CTDI vol,16 ~ 4.1 mGy PLEASE BE AWARE (this affects DLP, too)

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California State Law ( SB 1237) Important Clauses 115111. (a) Commencing July 1, 2012.. (b) The facility conducting the study shall electronically send each CT study and protocol page that lists the technical factors and dose of radiation to the electronic picture archiving and communications system. Patient Protocol page or DICOM RDSR fulfills this requirement (d) Subject to subdivision (e), the radiology report of a CT study shall include the dose of radiation by either recording the dose within the patients radiology report or attaching the protocol page that includes the dose of radiation to the radiology report. Not all scanners are capable of CT RDSR Would be nice to electronically integrate with radiology report (f) For the purposes of this section, dose of radiation shall be defined as one of the following: (1) The computed tomography index volume (CTDI vol) and dose length product (DLP), as defined by the International Electrotechnical Commission (IEC) and recognized by the federal Food and Drug Administration (FDA). (2) The dose unit as recommended by the American Association of Physicists in Medicine.

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To Comply With State Law We only need to report CTDI and DLPs But which ones? Individual CTDI/DLPs? Totals? Both?

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When Does It Make Sense to Add CTDI vol s When same anatomic region is scanned repeatedly and assumptions of CTDI apply (table movement, large anatomic region such as head, chest, abdomen, etc.) Examples: Non-con chest followed by post-contrast chest

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When Does It NOT Make Sense to Add CTDI vol s Different anatomic regions No table motion (perfusion scan)** Examples: chest followed by abdomen/pelvis ** CTDIvol OVER estimates Peak Dose (e.g. Skin or Eye Lens in Neuroperfusion scans) Adding these CTDIvols may be the best we can currently do, but the sum ONLY Pertains to limited area of perfusion scan

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When Does It Make Sense to Add DLPs Similar to CTDIvols When same anatomic region is scanned repeatedly and assumptions of CTDI apply (table movement, large anatomic region such as head, chest, abdomen, etc.) Examples: Non-con chest followed by post-contrast chest

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When Does It NOT Make Sense to Add DLPs Again, Similar to CTDIvols Different anatomic regions No table motion (perfusion scan) Examples: Head followed by C/A/P Even Chest followed by abdomen/pelvis

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Reporting Dose: How To Do It Right? Phase 0 (We Are Currently Here): Patient Protocol Page, Info. Manually Dictated into Radiology Report Phase 1 (We are Part of the Way Here): DICOM SR, Still Manually Dictated into Radiology Report Some scanners create DICOM SR, not easy to read and dictate Phase 2 (We WANT to be Here before July 1, 2012) DICOM SR, Auto-insert into Radiology Report Phase 3: DICOM SR, Body Region and Size Adjusted, Auto-insert into Radiology Report Phase 4: DICOM SR, Body Size Adjusted, Organ Doses; Auto-Insert into Radiology Report Phase 5: ????

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A Final Word - Effective Dose Effective Dose is a concept borrowed from health physics (people who work in radiation industry including nuclear power plants, radiologists, rad. Techs, med. Physicists). Effective Dose was never intended for dose to an individual; intended for populations

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Effective Dose E = T (w T *D T,R ) w T = tissue weighting factor (next page) D T,R = average absorbed dose to tissue T Units are: SI - Sieverts (Sv); English -rem 1 rem = 10 mSv; 1 Sv = 100 rem Looks simple, doesnt it?

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Effective Dose Tissue ICRP 60 Tissue weightsICRP 103 tissue weights Gonads (avg male/female)0.200.08 Red Bone Marrow 0.120.12 Colon (wall, not contents)0.120.12 Lung0.120.12 Stomach (wall, not contents)0.120.12 Bladder (wall, not contents)0.050.04 Breast (glandular)0.050.12 Liver0.050.04 Esophagus0.050.04 Thyroid0.050.04 Skin0.010.01 Bone Surface0.010.01 Brain(part of remainder)0.01 Remainder0.050.12

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One approximation: E= DLP * k, where E = Effective Dose in mSv DLP = Dose Length Product in mGy*cm k = conversion coefficient in mSv/mGy*cm k =.0021 mSv/mGy*cm for adult head k =.014 mSv/mGy*cm for adult chest k =.015 mSv/mGy*cm for adult abdomen/trunk DLP*k Method to Estimate Effective Dose

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Formula is based on approximation of a curve fit for several scanners (circa 1990) between E and DLP based on Monte Carlo simulations Patient model was standard man size 20-30 year old MALE, 70 kg, 57 tall With both male and female organs k values are based on ICRP 60 organ weights

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Effective Dose Again, effective Dose was never intended for dose to an individual; intended for populations Simple method (DLP*k) has several limitations Does not adjust for patient size Not designed for Tube Current Modulation methods

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Summary (1) Dose Metrics CTDI vol is reported on the scanner and in dose reports CTDI vol is Dose to one of two phantoms (16 or 32 cm diameter) CTDI vol is a good descriptor of scanner output And can be a good indicator of how output is adjusted for patient size (e.g. peds protocols). Larger patients SHOULD have a larger CTDI vol

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Summary (2) Reporting Tools Data Collection New/recent Modalities IHE REM / DICOM RDSR to capture dose data Legacy strategies Dose extractors to generate RDSR data Analysis IHE REM Dose Information Reporter for local analysis ACR Dose Registry to compare to benchmarks Prevention CT Dose Check for configurable pre-scan alerts 78

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Summary (3) Implementation Hints Turn On/Upgrade to get these Informatics Tools Review CT protocols Review Technical parameters, CTDIvol and DLP values Determine number of phases necessary for indication Review ACR CT Accreditation Program Guidelines Review AAPM protocols Review Usage ACR Dose Index Registry Use tools to help identify high dose exams and outliers

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Summary (4) Reporting Patient Dose CTDI vol Is not patient dose Is not skin dose overestimates skin dose for perfusion scans Is dose to a reference sized phantom Reference can vary from Peds to Adult or it might be same Will vary with patient size.and that is ok. Needs to be adjusted for patient size (SSDE) Need methods to determine when to add CTDIs and when not to (especially in automated fashion)