RT Journal Article SR Electronic T1 Prediction of Absorbed Dose to Normal Organs in Thyroid Cancer Patients Treated with 131I by Use of 124I PET and 3-Dimensional Internal Dosimetry Software JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 143 OP 149 VO 48 IS 1 A1 Katherine S. Kolbert A1 Keith S. Pentlow A1 Joel R. Pearson A1 Arif Sheikh A1 Ronald D. Finn A1 John L. Humm A1 Steven M. Larson YR 2007 UL http://jnm.snmjournals.org/content/48/1/143.abstract AB The objective of this work was to determine normal organ 131I dosimetry in patients undergoing radioiodide therapy for thyroid cancer by use of serial scanning with 124I PET. Methods: A total of 26 patients who had papillary and follicular metastatic thyroid cancer and who were already enrolled in a Memorial Sloan-Kettering Cancer Center 131I thyroid cancer protocol were selected for this study. Imaging before 131I therapy consisted of multiple, whole-body 124I PET studies over a period of 2–8 d, an 18F-FDG PET scan and, for some, a diagnostic CT scan. With a set of in-house–developed software tools (3-dimensional internal dosimetry [3D-ID] and Multiple Image Analysis Utility [MIAU]), the following procedures were performed: all PET emission and transmission and CT image sets were aligned; half-life–corrected tomographic images of 131I activity were integrated voxel by voxel to produce cumulated 131I activity images; and the latter images were, in turn, convolved with a 131I electron–photon point kernel to produce images of 131I dose distribution. Cumulated activity values and calculated residence times obtained from our patient-specific dosimetry software (3D-ID) were used as inputs to OLINDA, and volume difference–adjusted comparisons were made between the mean dose estimates. Results: With 3D-ID, dose volume histograms and mean doses were calculated for 14 organs, and results were expressed in Gy/GBq. The highest mean dose, 0.26 Gy/GBq, was seen in the right submandibular gland, whereas the lowest mean dose, 0.029 Gy/GBq, was seen in the brain. Conclusion: This is the first comprehensive study of normal organ dosimetry in patients by use of a quantitative tomographic imaging modality.