Radiation exposure assessment of nuclear medicine staff administering [177Lu]Lu-DOTA-TATE with active and passive dosimetry

BACKGROUND

The use of lutetium-177 (177Lu)-based radiopharmaceuticals in peptide receptor nuclear therapy is increasing, but so is the number of nuclear medicine workers exposed to higher levels of radiation. In recent years, [177Lu]Lu-DOTA-TATE has begun to be widely used for the treatment of neuroendocrine tumours. However, there are few studies evaluating the occupational radiation exposure during its administration, and there are still some challenges that can result in higher doses to the staff, such as a lack of trained personnel or fully standardised procedures. In response, this study aims to provide a comprehensive analysis of occupational doses to the staff involved in the administration of [177Lu]Lu-DOTA-TATE.

RESULTS

A total of 32 administrations of [177Lu]Lu-DOTA-TATE (7.4 GBq/session) carried out by a physician and a nurse, were studied. In total, two physicians and four nurses were independently monitored with cumulative (passive) and/or real-time (active) dosemeters. Extremity, eye lens and whole-body doses were evaluated in terms of the dosimetric quantities Hp(0.07), Hp(3) and Hp(10), respectively. It was obtained that lead aprons reduced dose rates and whole-body doses by 71% and 69% for the physicians, respectively, and by 56% and 68% for the nurses. On average, normalised Hp(10) values of 0.65 ± 0.18 µSv/GBq were obtained with active dosimetry, which is generally consistent with passive dosemeters. For physicians, the median of the maximum normalised Hp(0.07) values was 41.5 µSv/GBq on the non-dominant hand and 45.2 µSv/GBq on the dominant hand. For nurses 15.4 µSv/GBq on the non-dominant and 13.9 µSv/GBq on the dominant hand. The ratio or correction factor between the maximum dose measured on the hand and the dose measured on the base of the middle/ring finger of the non-dominant hand resulted in a factor of 5/6 for the physicians and 3/4 for the nurses. Finally, maximum normalised Hp(3) doses resulted in 2.02 µSv/GBq for physicians and 1.76 µSv/GBq for nurses.

CONCLUSIONS

If appropriate safety measures are taken, the administration of [177Lu]Lu-DOTA-TATE is a safe procedure for workers. However, regular monitoring is recommended to ensure that the annual dose limits are not exceeded.

(111)In-octreotide SPECT-CT in head and neck paragangliomas

Head and neck paragangliomas are rare neuroendocrine tumors expressing somatostatin receptors on their cell surface, particularly subtype 2. Due to this distinctive feature, images can be obtained in Nuclear Medicine using synthetic analogues of somatostatin, mainly octreotide, which allow selective display by planar scintigraphy, SPECT-CT or PET-CT imaging after radiolabeling with (111)In or (68)Ga. Three cases have been selected and presented from a series of patients that illustrate the utility of SPECT-CT studies with (111)In-octreotide in the diagnosis and monitoring of this type of tumor. These are characterization at initial diagnosis, staging, and detection of local recurrence or metastasis, with added value with respect to anatomical images (nuclear magnetic resonance, computed axial tomography, angiography), for example in the differentiation between functional tissue or scar in patients who had previously undergone surgery.

[Brain perfusion SPECT in the prognostic assessment of stroke]

PURPOSE

To compare the diagnostic yield of CT scan and perfusion SPECT on admission and its prognostic value in clinical outcome.

METHODS

25 ischemic stroke cases were studied on admission (<24 h) and at 30-60 days by CT scan, 99mTc-HMPAO-SPECT and neurological scales. Infarct size and severity on SPECT were assessed: visually "Total Weighted Score," added value in 22 areas, and by several semiquantitative count-based indices.

RESULTS

Sensitivity: the first CT scan was positive in 24% patients, initial SPECT in 75% (73% of pure subcortical infarcts and 91% of those with cortical involvement). Localization: kappa: 0.725 between SPECT findings on admission and those in control-CT at 5 days. Extent and severity: correlations between count-based and visual indices (r: >0.719), the latter correlated slightly better with clinical scales. Both predicted similarly (Rho>0.739) infarct size in CT diagnostic scan. Early Outcome: There were statistical differences between deceased and survivors in SPECT (<24h) indices and CT-infarct size (mean 5 days), but not in neurological scores on admission. Long term Outcome: Correlation of initial SPECT indices with follow-up functional scores (SNSLP, Barthel index; mean 37 days) was only significant for visual SPECT indices (Rho:0.560 to 0.620). Nevertheless the best predictor of functional status on discharge was the Barthel Index on admission.

CONCLUSIONS

1) Early SPECT has good sensitivity and accurate infarct size prediction so it can be a useful tool for deciding thrombolytic therapy; 2) Visual scores perform as well as more complex indices; 3) Infarct volume seems to be a critical determinant in vital outcome; other factors (strategic localization, etc.) might influence long term functional status.