Red Marrow Absorbed Dose Calculation in Thyroid Cancer Patient Using a Simplified Excel Spreadsheet/Tiroid Kanseri Hastasinda Basitlestirilmis Bir Excel Elektronik Tablosu Kullanilarak Kirmizi Iligin Absorbe Ettigi Dozun Hesaplamasi

Objectives: Absorbed dose to red marrow ([D.sub.rm]) can be calculated using blood dosimetry. However, this method is laborious and invasive. Therefore, image-based dosimetry is the method of choice. Nonetheless, the commercial software is expensive. The goal of this work was to develop a simplified excel spreadsheet for image-based radioiodine red marrow dosimetry. Methods: The serial whole-body images (acquired at 2nd, 6th, 24th, 48th, and 72th hours) of 29 patients from the routine pretherapeutic dosimetry protocol were retrospectively reanalyzed. The commercial OLINDA/EXM image-based dosimetry software was used to calculate the whole-body time-integrated activity coefficient ([TIAC.sub.WB]) and [D.sub.rm] [in terms of absorbed dose coefficient ([d.sub.rm])]. For the simplified excel spreadsheet, the whole-body count was obtained from the vendor-supplied software. Then, the [TIAC.sub.WB] was computed by a fitting time-activity curve using an Excel function. S factor was taken from other publications and scaled according to the patient-specific mass. A comparison of the [TIAC.sub.WB] and [d.sub.rm] from both methods was done using a non-inferiority test using a paired t-test or the Wilcoxon signed-rank test. Results: The [TIAC.sub.WB] showed no significant difference between both methods (p=0.243). The calculated [D.sub.rm] from a simplified Excel spreadsheet was assumed to be statistically non-inferior to the commercial OLINDA/EXM image-based dosimetry software with the non-inferiority margin of 0.02 (p