Standardizing Methods of Calculating and Reporting CT Dose

CT DOSE Some data suggests that CT procedures account for 16% of all radiologic procedures performed, but contribute 65% of the dose delivered to patients.

NEXT Does It Again In 2001, Hawaii used the 2000 NEXT CT Dose protocol on all 25 of its registered CT scanners and compared its findings to the 2000 NEXT results. –This revealed that Hawaiis mean CT Dose was 24% higher than NEXT. Prior to NJs QA rule, the BRH used NEXT data and found that NJ exceeded NEXT mean ESEs for AP Lumbar Spine and PA Chest.

CT Patient Dose Is part of a Medical Physicist QC CT Survey using either MSAD or CTDI and CT Equipment manufacturers specifications or patient scan protocol PROBLEM Inconsistent methods has resulted in inconsistent data regarding CT dose

Hawaiis Study Prompted the BRH to Look at CT Dose in NJ Original plan was to measure CT dose on 50 CT units using NEXT protocol. Instead, in June 2003, the BRH mailed a questionnaire to all CT facilities asking questions relating to dose. –62% of the facilities responded which accounted for 104 of the 305 registered CT units Survey reveals a need for standardizing the method by which CT dose is calculated.

Survey Revealed Inconsistency In: The method used: MSAD vs CTDI CTDI (FDA) vs CTDI (100) vs CTDI (w) vs CTDI (vol) The technique factors used: CT Equipment Manufacturers Specifications vs Patient Scan Protocol

Other Survey Results The 62% of the facilities who responded accounted for only 34% of all CT scanners registered. Type of CT Scanners: –34% Axial –44% Single Slice Helical –22% Multi-Slice Helical

Other Results Combined MSAD/CTDI Dose Data (R)

BRHs CT Dose Project To determine the current CT dose for both adult and pediatric patients. Mail CT dose letters to inform facilities of their CT dose and provide a comparison with other facilities. (See next slide) To track CT dose and encourage facilities with high doses to decrease their dose while maintaining image quality.

ACR: The Possible Fix 2002 CT Accreditation Program: –Requires Medical Physicists to calculate CT Dose for Adult Head, Adult Abdomen and Pediatric Abdomen (5 yrs of age). –Provides for downloadable Dose Calculator Spreadsheets for each procedure in either Exposure or Air Kerma. –Lists Dose Reference Levels in CTDI (w) for the above procedures. Dose Calculator Spreadsheets are now copyright protected. (Update)

Acknowledgement Statement The following two ACR forms in this presentation have been reprinted with the permission of the American College of Radiology, Reston, Virginia. No other representation of this material is authorized without express, written permission from the American College of Radiology.

Your input is needed with this project ! Discussion Item #1: As part of your Medical Physicist CT QC Survey, can one standardized method be used to calculate dose?

Discussion Item #2: If a standardized method can be used, which method should be used? – Is ACRs method and set up protocol acceptable?

Discussion Item #3: What techniques should be used? –The BRH recommends that the Patient Scan Protocol be used.

Discussion Item #4: How should dose be reported? –Should dose be reported in CTDI (w) or CTDI (vol) to account for pitch from helical scanning? –Should ACR forms be used? (If permission is granted) –Should BRH develop its own forms?

Discussion Item #5: What CT procedures should be monitored? –Adult Head, Adult Abdomen and Pediatric Abdomen

Discussion Item #6: How to report CT dose data to the BRH? -Are you willing to mail a copy of your report to the BRH shortly after the CT QC Survey is completed? – If you are currently using ACRs method would you submit dose calculations for the past year?

NEXT STEPS BRH to provide a summary of todays meeting to all medical physicists. BRH to collect and analyze CT dose data and present results to medical physicists as a future update.