Radiation emission from patients treated with selective hepatic radioembolization using yttrium-90 microspheres: are contact restrictions necessary?

PURPOSE: To estimate the possible radiation dose to other individuals from patients treated with yttrium-90 ((90)Y). MATERIALS AND METHODS: Dosimetry data were analyzed after 143 consecutive administrations of (90)Y (124 resin, 19 glass) in 86 patients. External radiation exposure levels from patients were measured immediately after infusion. Total effective dose equivalent (TEDE) to maximally exposed individuals was calculated based on total body residence time and measured dose rate. These values were compared to Nuclear Regulatory Commission (NRC) regulations (maximum, 1 mSv) and other potential guidelines for caregivers, extensive caregivers, or pregnant contacts. RESULTS: Mean administered activity for resin microspheres was 0.71 GBq ± 0.35 (range, 0.07-1.6GBq). Mean TEDE dose to the maximally exposed contact was 0.03 mSv (range, 0.0005-0.16 mSv). For glass microspheres, mean administered activity was 2.8 GBq ± 1.5 (range, 0.37-5.14 GBq). Mean TEDE dose to the maximally exposed contact was 0.06 mSv (range, 0.0023-0.23 mSv). All (90)Y treatments were within current NRC regulations for release without instructions. One, three, and one infusion were beyond potential thresholds for caregivers, extensive caregivers, or pregnant contacts, respectively. For any contact scenario, release without instruction was appropriate when administered activity was less than 3 GBq. CONCLUSIONS: All patients treated with (90)Y hepatic radioembolization to a maximum administered activity of 5.14 GBq and maximum dose rate of 10 uSv/h were releasable without contact restrictions according to the NRC contact scenario. Patients who receive more than 3 GBq during infusion may require dose rate measurement if more restrictive contact scenarios are considered.

Quantifying the Increase in Radiation Exposure Associated with SPECT/CT Compared to SPECT Alone for Routine Nuclear Medicine Examinations.

Purpose. We quantify the additional radiation exposure in terms of effective dose incurred by patients in the CT portion of SPECT/CT examinations. Methods. The effective dose from a variety of common nuclear medicine procedures is calculated and summarized. The extra exposure from the CT portion of the examination is summarized by examination and body part. Two hundred forty-eight scans from 221 patients are included in this study. The effective dose from the CT examination is also compared to average background radiation. Results. We found that the extra effective dose is not sufficient to cause deterministic effects. However, the stochastic effects may be significant, especially in patients undergoing numerous follow-up studies. The cumulative effect might increase the radiation exposure compared to patient management with SPECT alone. Conclusions. While the relative increase in radiation exposure associated with SPECT/CT is generally considered acceptable when compared with the benefits to the patient, physicians should make every effort to minimize this effect by using proper technical procedures and educating patients about the exposure they will receive.