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Program Information

CT: Size Specific Dose Estimate (SSDE): Why We Need Another CT Dose Index


Keith Strauss

K Strauss*, Cincinnati Children's Hospital Medical Center, CINCINNATI, OH

SA-B-Salon BCD-2 Saturday 3:30:00 PM - 5:30:00 PM Room: Salon BCD

Historically, two CT Dose Indexes, CTDIvol and Dose Length Product (DLP), have been used to quantify the delivery of radiation dose to standardized phantoms by the CT scanner during a clinical examination. Too many radiologists, technologists, and even some medical physicists do not realize that neither dose index is a reasonable estimation of the patient's radiation dose during the examination. The Size Specific Dose Index (SSDE) was recently developed by AAPM Task Group 204 to address this need for all size patients, from the smallest child to the largest adult.

This lecture will begin by defining CTDIvol, DLP, and Effective Dose (E Dose) and then explore why none of these dose estimates are reasonable estimates of patient dose. SSDE will be defined and explained based on the task group's published report. Sample calculations of estimated patient doses based on SSDE will be provided.

Useful clinical applications of SSDE will be explored such as dose reporting in the patient's medical record, eliminating confusion about CT doses from dissimilar CT scanners, and first estimates of organ doses from SSDE calculations. A method using SSDE will be explained that allows the consulting medical physicist to develop appropriate CT radiographic techniques for any CT scanner in any department from the smallest pediatric patients to the largest bariatric adults. The presentation will conclude with a description of challenges and solutions associated with effectively using the scanner's Automatic Exposure Control feature during pediatric imaging.

Learning Objectives:
1. Understand the inappropriateness of using CTDIvol, DLP or E Dose to estimate patient radiation dose during CT scanning.
2. Understand the strengths and weaknesses of SSDE as an estimate of patient radiation dose during CT scanning.
3. Understand how SSDE can be used in the clinic to develop appropriate CT radiographic techniques for any CT scanner in any clinical department.
4. Understand the basic problems and potential solutions to proper utilization of the Automatic Exposure Control features of a CT scanner for pediatric imaging.


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