Diagnostic Reference Levels for nuclear medicine imaging in Austria: A nationwide survey of used dose levels for adult patients.

PURPOSE: To assess dose levels in routine nuclear medicine (NUC) procedures in Austria as a prior to a legislative update of the National Diagnostic Reference Levels (NDRL). METHOD: As part of a nationwide survey of common NUC-examinations between June 2019 and November 2019, data sets were collected from 33 Austrian hospitals with NUC equipment. All hospitals were asked to report the NUC imaging devices in use (model, type, year of manufacture, detector material, collimators), the standard protocol parameters for selected examinations (standard activity, collimator, average acquisition time, reconstruction type, use of time-of-flight) and to report data from 10 representative examinations (e.g. injected activity, weight), incl. the most common NUC-examinations for planar imaging/SPECT and PET. Median/mean values for injected activity were calculated and compared to current Austrian and international NDRL. A Pearson correlation coefficient was computed comparing different variables. RESULTS: In total, all 33 hospitals (100% response rate) reported data for this study for 60 SPECT devices, 21 PET/CT devices and 23 scintigraphy devices. Fixed activity values for scintigraphy/SPECT and PET were employed by about 90% and 56% of the hospitals, respectively. The most widely performed examinations for scintigraphy/SPECT are bone imaging, thyroid imaging, renal imaging (with MAG3/EC) and lung perfusion imaging (in 88% of the hospitals) and F-18 FDG-PET studies for oncology indications (in 100% of the hospitals). Significant correlations were found for patient weight and injected activity (scintigraphy/SPECT), use of iterative reconstruction and injected activity (PET) as well as size of field-of-view and injected activity (PET). CONCLUSIONS: The reported injected activity levels were comparable to those in other countries. However, for procedures for which NDRL exist, deviations in injected activities of >20% compared to the NDRL were found. These deviations are assumed to result mainly from advances in technology but also from deviations between NDRL and prescribed activities as given in the information leaflets of the radiopharmaceuticals.

Comparison of 111In-DOTA-DPhe1-Tyr3-octreotide and 111In-DOTA-lanreotide scintigraphy and dosimetry in patients with neuroendocrine tumours.

PURPOSE: Somatostatin receptor scintigraphy with (111)In-DOTA-D: Phe(1)-Tyr(3)-octreotide ((111)In-DOTA-TOC) and (111)In-DOTA-lanreotide ((111)In-DOTA-LAN) has been used for staging of neuroendocrine tumours (NETs). However, the comparative diagnostic value of these radioligands on a lesion basis has not yet been established. The aim of this study was to compare the diagnostic capacity of (111)In-DOTA-TOC and (111)In-DOTA-LAN scintigraphy in patients with NETs, evaluating whether significant differences exist in lesion imaging with these radioligands. Furthermore, dosimetric data were compared. METHODS: Forty-five patients with NETs were investigated with (111)In-DOTA-TOC and (111)In-DOTA-LAN scintigraphy. Scintigraphic results were compared with those of conventional imaging and/or surgery in each patient, and also (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in 20 patients. RESULTS: (111)In-DOTA-TOC and (111)In-DOTA-LAN scintigraphy were true positive in 42/45 (93%) and 39/45 (87%) patients, and imaged 74/91 (81%) and 73/91 (80%) tumour lesions, respectively. (111)In-DOTA-TOC and (111)In-DOTA-LAN detected liver metastases in 21 and 14 patients, mediastinal metastases in seven and 11 patients, and bone metastases in two and seven patients, respectively. These radioligands revealed lesions not seen by conventional imaging in seven and eight patients, respectively, or by (18)F-FDG-PET in eight and seven patients, respectively. The estimated tumour absorbed doses for (90)Y-DOTA-TOC were higher than those for (90)Y-DOTA-LAN in 14 patients, whereas the opposite was true in 12 patients. CONCLUSION: Both (111)In-DOTA-TOC and (111)In-DOTA-LAN are suitable for imaging tumour lesions in patients with NETs and can detect lesions that may not be seen by conventional imaging and (18)F-FDG-PET. Compared with (111)In-DOTA-LAN, (111)In-DOTA-TOC has a superior diagnostic capacity for liver metastases, but a lower diagnostic capacity for metastatic lesions in mediastinum and bone.