Evaluation of a radiation transport modeling method for radioactive bone cement

Abstract

Spinal metastases are a common and serious manifestation of cancer, and are often treated with vertebroplasty/kyphoplasty followed by external beam radiation therapy (EBRT). As an alternative, we have introduced radioactive bone cement, i.e. bone cement incorporated with a radionuclide. In this study, we present a Monte Carlo radiation transport modeling method to calculate dose distributions within vertebrae containing radioactive cement. Model accuracy was evaluated by comparing model-predicted depth-dose curves to those measured experimentally in eight cadaveric vertebrae using radiochromic film. The high-gradient regions of the depth-dose curves differed by radial distances of 0.3-0.9 mm, an improvement over EBRT dosimetry accuracy. The low-gradient regions differed by 0.033-0.055 Gy/h/mCi, which may be important in situations involving prior spinal cord irradiation. Using a more rigorous evaluation of model accuracy, four models predicted the measured dose distribution within the experimental uncertainty, as represented by the 95% confidence interval of the measured log-linear depth-dose curve. The remaining four models required modification to account for marrow lost from the vertebrae during specimen preparation. However, the accuracy of the modified model results indicated that, when this source of uncertainty is accounted for, this modeling method can be used to predict dose distributions in vertebrae containing radioactive cement.

Radioactive bone cement for the treatment of spinal metastases: a dosimetric analysis of simulated clinical scenarios

“…To assist in the development of this technology, we previously presented a method for automatically generating anatomically correct, patient-specific, CT scan-based Monte Carlo radiation transport models of vertebrae containing radioactive bone cement. Model accuracy was experimentally evaluated and demonstrated that the models accurately predicted experimental dose distributions from cylindrical volumes of radioactive bone cement (Kaneko et al 2010). Thus, this modeling method provides a useful analytical tool with which to evaluate the clinical usefulness of radioactive bone cement, where clinical implantations involve radiation delivery over the life of the radioisotope, varying levels of implanted activity and more complex bone cement deposition patterns than the simplistic cylindrical volumes studied previously (Kaneko et al 2010).…”

“…A silicone mold of the posterior elements of each vertebra was created and used to hold the specimens in place, and CT scans were obtained with the vertebra immersed in water to All bone in the model was assigned a material number according to the ρ QCT value of the corresponding CT voxel, as described previously (Kaneko et al 2010). Each bone material was defined by its density and atomic composition and represented one of 30 possible complementary volume fractions of solid cortical bone and marrow (Bouchet et al 1999, Kvinnsland et al 2001, with the atomic composition of each constituent provided by Kramer et al (2006).…”

“…As a more convenient alternative, it may be possible to integrate radiation therapy into the percutaneous strength restoration procedure using radioactive bone cement, i.e. bone cement incorporated with a uniform distribution of a radionuclide (Marcus et al 2007, Hirsch et al 2008, Kaneko et al 2010. If effective, this combined approach could eliminate the need for separate radiation therapy and as many as 10-15 visits to the hospital (in the case of EBRT) for a patient whose quality of life has already been compromised.…”

“…Model accuracy was experimentally evaluated and demonstrated that the models accurately predicted experimental dose distributions from cylindrical volumes of radioactive bone cement (Kaneko et al 2010). Thus, this modeling method provides a useful analytical tool with which to evaluate the clinical usefulness of radioactive bone cement, where clinical implantations involve radiation delivery over the life of the radioisotope, varying levels of implanted activity and more complex bone cement deposition patterns than the simplistic cylindrical volumes studied previously (Kaneko et al 2010). Although the modeling method was shown to predict dose distributions from radioactive bone cement, the clinical usefulness of those dose distributions has not yet been studied, and is one of a number of critical factors that will determine whether radioactive bone cement can be used to effectively treat spinal metastases.…”

Estudo E Implementação De Microcontroladores Na Automação De Shopping Center

“…One solution to this undesirable event is the decompression of the vertebra by re-intervention by surgery (CHEN;LUO;ZHANG;NALAJALA et al, 2013;GERSZTEN, 2007;HENDRICKSON;SHEHATA;KIRCHNER, 1976). These percutaneous procedures are complementary to therapeutic treatments within tumor control (KANEKO; SEHGAL; SKINNER; AL-GHAZI et al, 2010). In most cases patients have advanced metastatic disease stage and the radiation therapy is palliative.…”