Technical Note: The development of a multi-physics simulation tool to estimate the background dose by systemic targeted alpha therapy.

PURPOSE: To predict biological effects of targeted alpha therapy (TAT) in preclinical studies, dosimetry calculations based on the micro-level distributions of emitters are essential. Due to the saturation of the tumor antigenic sites and bonding breaks by decay, some of Alpha-immuno-conjugate and decay daughters may inevitably be transported by convection and diffusion along with blood or lymphatic circulation. This results in highly nonuniform and unsteady distributions of irradiation sources. Since the micro-level distribution of emitters cannot be measured and obtained in patients with current technology, a modeling toolset to give more insight of the internal dose could be an alternative. METHODS: A multi-physics model based on a Monte Carlo microdosimetry technique and computational fluid dynamics (CFD) modeling was developed and applied to multiple internal irradiation sources. The CFD model tracks the path of the radionuclides and the dose model is capable of evaluating the time-dependent absorbed dose to the target. RESULTS: The conceptual model is capable of handling complex nonuniform irradiation sources in vasculature. The results from the simulations indicate that the assumption of homogeneous and motionless distribution of the administered activity used in the conventional dose calculation tends to significantly underestimate or overestimate the absorbed dose to the vascular system in various scenarios. CONCLUSION: Modeling the in vivo transport of radionuclides has the potential to improve the accuracy of TAT dose estimates. It could be the first step to develop a simulation tool set for assessing absorbed dose to tumor or normal tissues and predict the corresponding biological responses in the future.

Supracoronary myotomy for myocardial bridges in the setting of hypertrophic cardiomyopathy: off-pump experience.

Myocardial bridges (MB) are rarely observed but well known pathology of the major epicardial coronary arteries which are embedded in the overlying myocardial tissue. It is most frequently found in young patients with hypertrophic cardiomyopathy (HCM). Myocardial bridges are associated with myocardial ischemia and infarction, cardiac arrhythmias and sudden death. The present case series report the outcomes of three symptomatic patients with hypertrophic cardiomyopathy who underwent myocardial muscle debridges. They were operated using beating heart technique without cardiopulmonary bypass. The authors conclude that off-pump supracoronary muscle myotomy is a feasible treatment modality in the young age group with non-obstructive hypertrophic cardiomyopathy.

Radiation-induced coronary artery disease.

Radiation-induced heart disease must be considered in any patient with cardiac symptomatology who had prior mediastinal irradiation. Radiation can affect all the structures in the heart, including the pericardium, the myocardium, the valves and the conduction system. In addition to these pathologies, coronary artery disease following mediastinal radiotherapy is the most actual cardiac pathology as it may cause cardiac emergencies requiring interventional cardiological or surgical interventions. Case A 36-year-old man was admitted to the clinic with unstable angina pectoris of one month duration. The patient had no coronary artery disease risk factor. The history of the patient revealed that he had mediastinal radiotherapy due to Hodgkin's disease at 10-year of age. Coronary arteriography showed total occlusion of the left anterior descending artery and 70% stenosis of the proximal right coronary artery. Both arteries are dilated with placement of two stents. Control coronary arteriography at the end of the first year showed patency of both stents and the patient is free of symptoms. Previous radiotherapy to the mediastinum should be considered as a risk factor for the development of premature coronary artery disease. Percutaneous transluminal coronary angioplasty with stent placement or surgical revascularization are the preferred methods of treatment. Preoperative assessment of internal thoracic arteries should be considered prior to surgery. As the radiation therapy is currently the standard treatment for a number of mediastinal malignancies, routine screening of these patients and optimal cardiac prevention during radiotherapy are the only ways to minimize the incidence of radiation-induced heart disease.