Computational dosimetry evaluation in vertebral models using a radioactive bone cement with Sm-153, Ho-166 and Y-90

Abstract

Background: Breast cancer is a disease that affects a large part of the Brazilian female population. Especially, those metastases developed in the spinal column can produce potential fractures with neurological compromise or reduction of the life’s quality of the patient due to chronic pain. Objective: The development of a computational dosimetry in vertebral models simulating bone metastasis applying a radioactive bone cement with Sm-153, Ho-166 and Y-90. Methods: 1. Based on radiological images of animal vertebrae was constructed in the code MCNPx. Absorbed doses were evaluated in the axial plane (XY) of the implant of the radioactive bone cement in the metastasis. The nearest organ of risk (OAR) was the spinal cord and the implant itself on the vertebras was the prescribed tumor volume (PTV). The Sm-153, Ho-166 and Y-90 radionuclides were considered. 2. The fluency of the electrons along the symmetrical axis of the vertebra x = 0 in the z = 0 planes was also studied. Results: The therapeutic absorbed dose obtained in the implant plane by radioactive bone cement reaches levels above 70 Gy for specific activities close to 3 GBq.mg-1 with suitable values for the Y-90 coupled to the cement. Exposure to Ho-166 produces a lower dose than in Y-90 but higher than in Sm-153. The doses obtained by radionuclide implants are better spatial distributed than IMRT, with a significant dose reduction in the spinal cord. Beta emitting from Y-90 found a greater range. Conclusions: The radioactive cement in an implant may potentially favor optimal tumor control and lower side effects in organs at risk.