[Effect of Relative Electron Density and Physical Density Adjustment in Patient-specific Quality Assurance Using PMMA Phantom].

PURPOSE: The purpose of this study was to improve the accuracy of dose-distribution calculations by understanding how the calculated dose varies with the change in the relative electron density replacing polymethyl methacrylate (PMMA) in patient-specific quality assurance. METHOD: We calculated the relative electron density at which dose attenuation in each dose calculation algorithm coincides with the measured value of the dose attenuation of single-field irradiation. Next, the dose change was calculated by changing the relative electron density or physical electron density for substituting PMMA for each X-ray energy and calculation algorithm. Furthermore, using clinical plans, changes in point-dose verification and dose-distribution verification that occurred when the relative electron density or physical electron density was varied were investigated. RESULTS: The dose attenuation varies depending on the dose-calculation algorithm, and the optimum value of the electron density is different for each. After the electron density optimization, the point dose verification using the 97.1% to 98.3% (3%/3 mm), 90.0% to 94.3% (2%/3 mm) and gained a dominant improvement tendency (P<0.001). CONCLUSIONS: We clarified dose change accompanying relative electron density or physical electron density change. We concluded that the accuracy of dose-distribution calculation for verification improves by replacing PMMA with optimal relative electron density or physical electron density.

Two cases of acute myocardial infarction during combined chemotherapy in young patients with testicular cancer.

The two patients were males aged over 30 years. To treat testicular tumors, combination chemotherapy with bleomycin, etoposide, and cisplatin (BEP) had been employed. In case 1, during the 4th course of BEP therapy, thoracic pain suddenly appeared. Emergency coronary angiography revealed thrombus formation. Under a diagnosis of thrombus-related acute myocardial infarction, thrombus aspiration was conducted, and stent implantation was performed because mild stenosis and residual thrombus were observed. In case 2, during the 2nd course of BEP therapy, thoracic pain suddenly appeared. Emergency coronary angiography revealed thrombus formation. Intracoronary infusion of pro-urokinase was performed, and additional balloon dilatation was conducted because mild stenosis and residual thrombus were observed. In both cases, the courses were favorable, and the levels of coagulation markers on admission were high. When selecting combination chemotherapy in patients with coronary risk factors, such as obesity and smoking, despite a young age, as demonstrated in these two patients, it may be important to consider combination therapy with anticoagulants or switching to anticancer drugs that do not show vascular toxicity. .