Implementing Dosimetry in the Clinic

Clinical dosimetry is a multistep procedure (see Fig. 11.1); each step is essential to obtain an accurate estimate of the absorbed dose delivered to one or more tumours or normal tissues. The first step in the clinical dosimetry workflow is the calibration procedure (step 1). This is a prerequisite for activity determination and may require phantom image acquisition with a known amount of activity that should ideally be traceable to a standard laboratory. Procedures for obtaining quantitative information on the activity or activity concentration from images were presented in Chapter 4 and will include sensitivity determination and may include partial volume and dead time corrections. The calibration procedure is a key step in accurately determining the activity distribution. The calibration step and patient image/data acquisition step (step 2) are linked; the camera settings used in the quantitative imaging calibration procedure should be used for all patient imaging. For single photon emission computed tomography (SPECT) quantitative imaging this may mean that the acquisition matrix size, the type of collimator or the number and position of energy windows should remain constant between phantom calibration and patient imaging.