A practical guideline for the release of patients treated by I-131 based on Monte Carlo dose calculations for family members

Abstract

We recently published effective doses per time-integrated activity (mSv MBq(-1) s(-1)) for paediatric and adult family members exposed to an adult patient released from hospital following I-131 therapy. In the present study, we intend to provide medical physicists with a methodology to estimate family member effective dose in daily clinical practice because the duration of post-radiation precautions for the patient-family member exposure scenario has not been explicitly delineated based on the effective dose. Four different exposure scenarios are considered in this study including (1) a patient and a family member standing face to face, (2) a patient and a family member lying side by side, (3) an adult female patient holding a newborn child to her chest and (4) a one-year-old child standing on the lap of an adult female patient following her I-131 therapy. The results of this study suggest that an adult female hyperthyroidism (HT) patient who was administered with 740 MBq should keep a distance of 100 cm from a 15-year-old child for six days and the same distance from other adults for seven days. The HT female patient should avoid holding a newborn against her chest for at least 16 days following hospital discharge, and a female patient treated with 5550 MBq for differentiated thyroid cancer should not hold her newborn child for at least 15 days following hospital discharge. This study also gives dose coefficients allowing one to predict age-specific effective doses to family members given the measured dose rate (mSv h(-1)) of the patient. In conclusion, effective dose-based patient release criteria with a modified NRC two-component model provide a site medical physicist with less restrictive and age-specific radiation precaution guidance as they fully consider a patient's iodine biokinetics and photon attenuation within both the patient and the exposed family members.

Estimation of patient attenuation factor for iodine-131 based on direct dose rate measurements from radioiodine therapy patients

“…The gamma exposure rate constant used was 59.5 μSv/h/GBq or 2.2 R/h/mCi [2]. The ion chamber response was within 4% of the expected calculated dose rate using the point source method.…”

Guidelines on the Release of Patients Treated with Iodine – 131 for Thyroid Cancer in Nuclear Medicine: Case of Madagascar

“…Some Researchers [24] suggested that a female patient treated with 5550 MBq for thyroid cancer should not hold her newborn child for at least 15 days following hospital discharge. The South African Department of Health [25] gave conditions for using radioactive nuclides.…”

Tumor dosimetry for I-131 trastuzumab therapy in a Her2+ NCI N87 xenograft mouse model using the Siemens SYMBIA E gamma camera with a pinhole collimator

“…Pretreatment dosimetry prior to I-131 treatment for patients with differentiated thyroid cancer has been shown to optimize the dosing regimen in terms of the effectiveness and safety [20]. Further, patient-specific dosimetry using I-124 mIBG PET/computed tomography (CT) imaging and the Monte Carlo method has been reported for treatment planning [21], and the effective doses per time-integrated activity for pediatric and adult family members exposed to an adult patient released from hospital following I-131 therapy [22], as well as the appropriate guidelines, have also been previously reported [23]. Furthermore, radiation dosimetry and preliminary therapy results using an I-124/I-131 small molecule (MIP-1095) targeting prostatespecific membrane antigen for prostate cancer therapy have also been described [24].…”