Abstract
Aim Peptide receptor radionuclide therapy (PRRT) with (177) Lu-HA-DOTATATE has evolved as a new path in the treatment of somatostatin-receptor-expressing neuroendocrine tumors. The kidneys are proven as organs at risk and should be evaluated dosimetrically. Overlap with other organs will make dosimetry based on planar scintigraphy inaccurate. Aim of this study was to approximate the contribution ...
Abstract
Aim Peptide receptor radionuclide therapy (PRRT) with (177) Lu-HA-DOTATATE has evolved as a new path in the treatment of somatostatin-receptor-expressing neuroendocrine tumors. The kidneys are proven as organs at risk and should be evaluated dosimetrically. Overlap with other organs will make dosimetry based on planar scintigraphy inaccurate. Aim of this study was to approximate the contribution of the kidneys to conjugated planar views without the use of a SPECT/CT. Material and Method An algorithm was developed to determine the kidney dose using an EXCEL (Microsoft) based program. Dosimetric data were drawn and merged from three modalities: an individually calibrated gamma probe, a whole-body scintigraphy (WBS) and SPECT-acquisitions. The method was evaluated for 85 kidneys. Kidney masses were obtained via CT volumetry. Results The developed algorithm combines data from the three modalities. The ratio of the events within a kidney-VOI and the events from the summed coronary SPECT views (kidney ROI) represents the contribution of the kidney to the whole-body kidney ROI. This fraction was calculated to 49 % (17 % - 78 %) and 45 % (18 % - 75 %) for the left and the right kidney, respectively. Quantification of activity was deduced from equalizing the WBS count with the concurrent gamma probe measurement. Monoexponential curves were fitted to the obtained kidney activities, with resulting doses of 0,13 to 0,77 Gy/GBq (average 0,36 and 0,39 Gy/GBq for the left and the right kidney). Conclusion The presented method is suitable to perform kidney dosimetry by using a gamma probe and a gamma camera, without using SPECT/CT.
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