Prediction of 1 cm dose-equivalent rate on the day after administration of Lu-DOTATATE from In-somatostatine receptor scintigraphy prior to treatment.

OBJECTIVE

When patients administered Lu-DOTATATE are released or discharged from rooms where radiopharmaceuticals are used, the time required for release or discharge varies across patients. This study investigated whether the amount of radioactivity accumulated on In-somatostatine receptor scintigraphy (In-SRS) performed prior to treatment can predict the 1 cm dose-equivalent rate at a distance of 1 m from the patient on the day after Lu-DOTATATE administration.

METHODS

Whole-body planar In-SRS images were acquired for 21 patients. Pixel values within whole-body and abdominal (35 × 25 cm) regions of interest (ROIs) were converted to radioactivity dose (MBq). The 1 cm dose-equivalent rate (µSv/h) at a distance of 1 m from the patient 18.3 ± 0.5 h after administration of Lu-DOTATATE was measured using an ionization survey meter.

RESULTS

The following relationships were observed between the radioactivity on In-SRS and the 1 cm dose-equivalent rate on the day after administration of Lu-DOTATATE: whole-body ROI: y = 0.16x + 5.01 (r = 0.56, p = 0.009), abdominal ROI: y = 0.27x + 5.13 (r = 0.63, p = 0.002). The regression equations indicate that patients cannot be released or discharged from the radiopharmaceutical room the day after Lu-DOTATATE administration if the whole-body and abdominal ROI doses are greater than 81 and 48 MBq, respectively, on In-SRS.

CONCLUSIONS

The amount of radioactivity accumulated on In-SRS may be a predictor of release criteria for patients receiving Lu-DOTATATE.