1. Monitoring Radiation Exposure (2011 Update): Standards, Tools and IHE REM
Kevin O’Donnell
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

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

3. 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

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

5. CT –Specific Dose Definitions
Computed Tomography Dose Index (CTDI) & its cousins
CTDI100
CTDIw- weighted
CTDIvol
Dose Length Product (DLP)
Dose Reports

6. 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

7. 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

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

9. 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)

10. Some typical CTDI100 values
CTDI100 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
Some typical CTDI100 values
60 mGy 20 10 20 60 60 60 60 20
Head
Body

11. CTDIw CTDIw = (1/3)CTDI100,center + (2/3)CTDI100,peripheral
CTDIw is a weighted average of center and peripheral CTDI100 to arrive at a single descriptor
CTDIw = (1/3)CTDI100,center + (2/3)CTDI100,peripheral

12. CTDI vol Calculated, not measured directly
Based on CTDIw, but accounts for pitch
CTDIvol = CTDIw / Pitch

13. CTDIvol in Context of AEC
When Tube current modulation is used:
CTDIvol reported is based on the average mA used throughout the scan

14. 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

15. DLP – defined Dose Length Product is: Found in most “Dose Reports”
CTDIvol* length of scan (in mGy*cm)
Found in most “Dose Reports”
Includes any overscan (extra scanning for helical scans)

16. CTDIvol and DLP CTDIvol is reported on the scanner and in dose reports
CTDIvol is Dose to one of two phantoms
(16 or 32 cm diameter)
CTDIvol 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 CTDIvol

17. Standards & Tools
You believe managing dose is part of the practice of radiology. What’s your plan? How are you going to get started?
On average, what’s your dose for an adult chest CT without contrast?
You could give your techs a pencil and a dose log sheet. It’s easy. But it’s not scalable or detailed.
Scalable – not just on Friday afternoons
Efficient – want details (CTDI is the gold/silver standard, lets get that and as much else as we can too) 17

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

19. Radiation Dose Structured Report
DICOM RDSR
Radiation Dose Structured Report
Object

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

21. Key Measurements CT Dose Projection X-Ray Dose Mammography Dose
DLP, CTDIvol, kVP, mA, sec
Effective Dose [ Optional; Reference estimation method ]
Projection X-Ray Dose
DAP, kVP, mA, sec
Fluoro Dose, Fluoro Time
[CR/DR: Exposure Index, Deviation Index]
Mammography Dose
AGD, Entrance kVP, mA, sec
Compression, Half Value Layer
Mention work to upgrade the pipeline to address size-compensated dose, organ dose, etc.
ftp://medical.nema.org/medical/dicom/2011/11_16pu.pdf

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

24. Radiation Exposure Monitoring
IHE REM Profile
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Numerical Details
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Radiation Exposure Monitoring
Going to Final Text in 2011

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
Connectathon: one week, 85+ vendors, 400+ engineers, thousands of tests.

26. IHE Radiation Exposure Monitoring Profile
National Registry
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Numerical Details
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Outlier: #
Performing Phys.
Over Target: 12.2%
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Dose Information
Reporter
Archive
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Final Text
RDSR goes into the study record, onto CDs, etc. etc.
Highlight that the Archive can be bypassed if need be, and that various innovative Dose Consumers can be incorporated
And point out Reporting Workstation auto-populating dose field for CA regs.
And it’s a Pipeline. New fields will periodically be added to the RDSR, systems will start populating, and it all follows the same pipeline.
(Spirit of not letting Perfect be the enemy of Good)

27. Using SR Dose Reports Radiation QA Patient Impact Evaluation
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

28. Using SR Dose Reports National Registries Individual Dose Record
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

29. Legacy Dose Extractors
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Numerical Details
Going to Final Text in 2011

30. Legacy Extractor What if you can’t 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
Incomplete - likely to be missing patient weight, procedure details, fine grained information, phantom information, etc. etc.

31. 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)

32. ACR DIR
Dose Index Registry
Going to Final Text in 2011

33. 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
Note: ACR was early collaborator for IHE REM profile 33

34. ACR Activity Tracking practice Procedure Naming Issue
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

35. Predicted DLP (981 mGy-cm)
MITA XR-25
Dose Notification
Predicted DLP (981 mGy-cm)
Exceeds Threshold …
CT Dose Check
Going to Final Text in 2011

36. 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:

37. 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 CTDIvol values for each scan element
e.g. head without contrast
Defined by the clinical site for their patient population

38. Dose Alert Pop-up message
Alerts technologist cumulative dose for current study will exceed a trigger value:
CTDIvol (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 CTDIvol values
System must allow at least one global value
System tracks accumulated CTDIvol at each patient location & accumulated DLP
System checks predicted accumulated dose indices when protocols are saved & when scans are ready
Site can facilitate a variety of policies based on how they activate and distribute password.

39. 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

40. 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
75th percentile -> popups on 25% of scans
See AAPM guidance
Affect/constrain behavior vs alert fatigue

41. Implementation Progress
IHE REM
Testing: IHE Connectathon
Product: IHE Integration Statement
DICOM RDSR
Product: DICOM Conformance Statement
NEMA XR-25
Vendors commitment; some products already released 41

42. Takeaway Data Collection New/recent Modalities Legacy strategies
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
BUT this is not a radiation safety program in a box. These are tools.
You need to understand the metrics for what they are (and aren’t), and implement a program to record/analyze/apply them sensibly

43. 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)
MITA’s Dose Check (also may require software upgrade)
Consider joining ACR’s Dose Index Registry 43

44. 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<5kg, peds 6-16 kg, peds> 16kg)
Some combination of these two 44

45. 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

46. ACR CT Dose Reference Values
Based Solely on CTDIvol (not DLP)
Two levels:
Reference level and Pass/Fail level
Exam Ref Level Pass/Fail Level
Adult Head* 75 mGy 80 mGy
Adult Abdomen* 25 mGy 30 mGy
Pediatric (5 y/o) Abd* 20 mGy 25 mGy
Pediatric Head* 45 mGy None (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

47. 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

48. 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

49. 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)?
It’s “the right thing to do”? 49

50. Limitations of CTDIvol
Some things you should know before you start reporting dose in patient records
CTDIvol is Dose to one of two phantoms
(16 or 32 cm diameter)
CTDIvol 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 CTDIvol 50

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

52. CTDIvol 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 CTDIvol
This is not a bad thing, it reflects proper adjustments in tube output 52

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

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

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

56. Limitations to CTDI CTDIvol 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)

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

58. CTDIvol and Peak Dose (Perfusion Scans)
CTDIvol 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 Jan-Feb;28(1):245-53

59. CTDIvol and Peak Dose (Perfusion Scans)
CTDIvol 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).

60. CTDIvol and DLP
Need other information such as patient size, body region, clinical indication to determine if scan was done “correctly” or “Alara”

61. CTDIvol 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 CTDIvol 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”

62. Still want/need to Report Dose?
Let’s look at what is available to report 62

63. Which Phantom Was Used for CTDI
Currently:
ALL HEADS (Adult/Peds) – 16 cm phantom
ALL ADULT BODY – 32 cm phantom
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)
CTDIvols differ by a factor of approx 2.5
So, previous example, CTDIvol,32 = 1.71 mGy
If report used 16 cm phantom, CTDIvol,16 ~ 4.1 mGy
PLEASE BE AWARE (this affects DLP, too)

64. California State Law ( SB 1237) – Important Clauses
(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 patient’s 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.

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

66. When Does It Make Sense to Add 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

67. When Does It NOT Make Sense to Add CTDIvols
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

68. When Does It Make Sense to Add DLPs
Similar to CTDIvol’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

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

70. 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: ????

71. 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

72. Effective Dose E = T(wT*DT,R) wT= tissue weighting factor (next page)
DT,R= average absorbed dose to tissue T
Units are: SI - Sieverts (Sv); English -rem
1 rem = 10 mSv; 1 Sv = 100 rem
Looks simple, doesn’t it?

73. Effective Dose Tissue ICRP 60 Tissue weights ICRP 103 tissue weights
Gonads (avg male/female)
Red Bone Marrow
Colon (wall, not contents)
Lung
Stomach (wall, not contents)
Bladder (wall, not contents)
Breast (glandular)
Liver
Esophagus
Thyroid
Skin
Bone Surface
Brain (part of remainder) 0.01
Remainder

74. DLP*k Method to Estimate Effective Dose
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 = mSv/mGy*cm for adult head
k = .014 mSv/mGy*cm for adult chest
k = .015 mSv/mGy*cm for adult abdomen/trunk

75. DLP*k Method to Estimate Effective Dose
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, 5’7” tall
With both male and female organs
k values are based on ICRP 60 organ weights

76. 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

77. Summary (1) – Dose Metrics
CTDIvol is reported on the scanner and in dose reports
CTDIvol is Dose to one of two phantoms
(16 or 32 cm diameter)
CTDIvol 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 CTDIvol

78. 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

79. 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

80. Summary (4) Reporting Patient Dose
CTDIvol
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)