Software for the radionuclide vertebroplasty
The problem of program maintenance for radionuclide vertebroplasty is considered. Requirements for systems of preoperative preparation and postoperative analysis are described. The object domain (the vertebra being operated on and its vicinity) is modelled with the use of CT scans in two ways, namely, a) precisely, on the basis of voxel representation and b) approximately, for use in on-line interactive calculations. The voxel model is made in two versions: for dose and temperature calculation. The MCNP code is applied for dose calculation. Selection of radionuclides is carried out in serial calculations; the most suitable "candidates" are identified for application in this procedure based on a set of characteristics. A code was developed which allows solving online both the «direct» problem (dose calculation close to the bone cement being entered at a preselected radionuclide activity), and the «inverse» one (calculation of necessary radionuclide activity to be entered in a specific localization near the cement "kernel" which will produce a specified dose). Calculations of the temperature fields caused by polymerization of bone cement are made by means of the thermohydraulic codes applied for nuclear reactor design calculation; these codes are adapted for use in vertebroplasty on the basis of the problem-oriented experiments performed. Using well-established methodologies for assessing synergistic effects of radiation and heating on tissue, "amplifier gains" for beam influence were obtained, and areas of radical and palliative therapeutic effects for specific vertebroplasty conditions are defined. The beta version of the code for radionuclide vertebroplasty planning is created on the basis of combined experimental and computational data.