[Diagnostic reference value. Critical evaluation of the term with the example of nuclear medicine studies in Austria]

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.

POPULATION RADIATION EXPOSURE FROM DIAGNOSTIC NUCLEAR MEDICINE PROCEDURES IN TEHRAN 2011-14; TRENDS IN THE LAST 3 DECADES

This study represents an update of Tehran population exposure from the diagnostic nuclear medicine procedures and the annual collective effective dose during 2011-14. The diagnostic nuclear medicine procedures data were collected from 58 out of 60 nuclear medicine centers in Tehran and were composed of the type and frequency of diagnostic examinations, radiopharmaceuticals used, administered activities, and age distribution of the patients. The annual number of examinations per 1000 population increased from 13.73 in 2011 to 22.59 in 2014 with an increase of 64.53% during 4 years. Most frequent examinations were cardiac (71.05%), bone (9.80%) and thyroid (7.26%) averaged over the 5 years. The collective effective dose increased from 807.74 person-Sv in 2011 to 1413.81 person-Sv in 2014. The effective dose per capita increased from 44.06 μSv in 2011 to 120.91 μSv in 2014, could be because of 70% increase of examinations, but ~3.42% increase in the population of Tehran.

Extraordinary Lymph Drainage in Cutaneous Malignant Melanoma and the Value of Hybrid Imaging: A Case Report

In melanoma patients, preoperative lymphoscintigraphy has become a gold standard. The role of single-photon emission computed tomography (SPECT) or its combination with computed tomography (SPECT-CT) as part of the standard sentinel scintigraphy protocol has yet to be determined. A 46-year-old female patient with melanoma of the trunk received preoperative lymphoscintigraphy and subsequent surgical excision. Planar imaging displayed two hot spots in the region of the primary lesion. No other lymphatic flow pathways could be appreciated. Two focal hot spots, one dorsal to the primary lesion near the left latissimus dorsi muscle and one just lateral to the primary lesion in the subcutaneous tissue, were appreciated with SPECT-CT imaging. The primary melanoma lesion, as well as the two additional lesions, which were detected by SPECT-CT, were excised and sent for histopathological examination. While the primary lesion was a superficial spreading melanoma, the lesions appreciated in SPECT-CT revealed four sentinel lymph nodes, each of which was negative for tumor cells. Melanomas, especially of the trunk, can demonstrate multiple lymphatic drain basins in a large percentage of patients. Given that without the detailed anatomical information provided by SPECT-CT it would be very difficult to locate the diverse lymphatic drain basins and their lymph nodes, we would suggest routinely implementing SPECT-CT in the standard planar sentinel imaging protocol.