Considerations on the Practical Application of the Size-specific Dose Estimation (SSDE) Method of AAPM Report 204

Computed tomography (CT) is responsible for much of the radiation exposure to the population for medical purposes. The technique requires high doses that vary widely from center to center, and for different scanners and radiologists as well. In order to monitor doses to patients, the American Association of Physicists in Medicine has developed the size-specific dose estimate (SSDE), which consists of the determination of patient size dependent coefficients for converting the standard dosimetric index, CTDIvol, into an estimate of the dose actually absorbed by the patient. The present work deals with issues concerning the use of SSDE in the clinical practice. First the issue regarding how much SSDE varies when, for a given CT protocol, the scan covers slightly different volumes is addressed. Then, the differences among SSDE values derived from different patient size descriptors are investigated. For these purposes, data from a clinical archive are analyzed by an automatic procedure specifically developed for SSDE.