Validation of an in-house developed therapeutic dosimetric software tool for the treatment of 177Lutetium-DOTATATE peptide receptor radionuclide therapy

Background Computer software for absorbed dose quantification has been used widely in nuclear medicine. Different software tools have been written to improve the dose assessment, especially in therapeutic nuclear medicine. Some software tools focusing on computational phantom models from the international commission of radiation protection and units (ICRP) whilst others on Monte Carlo simulated models. While many studies have investigated therapeutic nuclear medicine dosimetry. The authors have noticed that very few papers compare the therapeutic software tools to each other, hence a doctor of philosophy study was embarked on. The aim of our study was therefore to validate our in-house developed software tool Masterdose using the commercial software OLINDA/EXM 1.0 that was available in our department. Methods Methodology was based on clinical patient data treated for neuroendocrine tumours with (177)Lutetium (Lu)-DOTATATE at a South African hospital. All patients underwent the same SPECT acquisition protocol and were corrected for scatter, partial volume, collimator-detector response, gamma camera calibration and attenuation. Correction factors were applied to images to convert counts to activity. The first cycle of peptide receptor radionuclide therapy (PRRT) for 11 single photon emission computed tomography (SPECT) patients were compared on the Masterdose and OLINDA/EXM 1.0 software tools at 1, 24, 72 and 168 h. Cumulated activity and the absorbed dose were compared for the two software tools. The absorbed dose difference was then compared using statistical Bland-Altman analysis. Results Masterdose and OLINDA/EXM 1.0 had different peptide receptor radionuclide therapy methodologies. This led to different results obtained for the software tools. Cumulated activities of Masterdose and DTK was 10.5% and 10.9% for the kidneys and tumours respectively. On average tumour absorbed doses were nine-times that of the kidneys. Bland-Altman analysis show a non-systematic difference between the two software. Conclusion On average the relative percentage difference between the cumulated activities and absorbed dose of the two software were 10.7%.