Optimal set of grid size and angular increment for practical dose calculation using the dynamic conformal arc technique: a systematic evaluation of the dosimetric effects in lung stereotactic body radiation therapy

Purpose To recommend the optimal plan parameter set of grid size and angular increment for dose calculations in treatment planning for lung stereotactic body radiation therapy (SBRT) using dynamic conformal arc therapy (DCAT) considering both accuracy and computational efficiency. Materials and methods Dose variations with varying grid sizes (2, 3, and 4 mm) and angular increments (2°, 4°, 6°, and 10°) were analyzed in a thorax phantom for 3 spherical target volumes and in 9 patient cases. A 2-mm grid size and 2° angular increment are assumed sufficient to serve as reference values. The dosimetric effect was evaluated using dose–volume histograms, monitor units (MUs), and dose to organs at risk (OARs) for a definite volume corresponding to the dose–volume constraint in lung SBRT. The times required for dose calculations using each parameter set were compared for clinical practicality. Results Larger grid sizes caused a dose increase to the structures and required higher MUs to achieve the target coverage. The discrete beam arrangements at each angular increment led to over- and under-estimated OARs doses due to the undulating dose distribution. When a 2° angular increment was used in both studies, a 4-mm grid size changed the dose variation by up to 3–4% (50 cGy) for the heart and the spinal cord, while a 3-mm grid size produced a dose difference of \u3c1% (12 cGy) in all tested OARs. When a 3-mm grid size was employed, angular increments of 6° and 10° caused maximum dose variations of 3% (23 cGy) and 10% (61 cGy) in the spinal cord, respectively, while a 4° increment resulted in a dose difference of \u3c1% (8 cGy) in all cases except for that of one patient. The 3-mm grid size and 4° angular increment enabled a 78% savings in computation time without making any critical sacrifices to dose accuracy. Conclusions A parameter set with a 3-mm grid size and a 4° angular increment is found to be appropriate for predicting patient dose distributions with a dose difference below 1% while reducing the computation time by more than half for lung SBRT using DCAT

Angiosarcoma of the Retroperitoneum: Report on a Patient Treated with Sunitinib

A 52 year-old woman presented with an incidentally detected retroperitoneal angiosarcoma and multiple hepatic metastases. After chemotherapy with weekly paclitaxel and doxorubicin, angiosarcoma had progressed rapidly. Because few chemotherapeutic options were available for her, sunitinib (37.5 mg/day, daily) as a salvage regimen was administered. Although sunitinib was interrupted after two weeks due to hematologic abnormalities, some metastatic nodules were regressed. Therefore, sunitinib was recommenced at a reduced dose (25 mg/day, daily). Serial computed tomography scans showed variable response in each tumor, however, sunitinib at least delayed tumor progression, compared to previous chemotherapy. With this case report, we suggest sunitinib may be effective against angiosarcomas. When sunitinib is administered to patients with angiosarcomas, hematologic abnormalities should be monitored frequently as severe hematologic toxicity may be caused either by sunitinib per se or angiosarcoma

Claude's Syndrome Associated with Neurocysticercosis

Claude's syndrome is a distinctive brainstem syndrome characterized by ipsilateral third cranial nerve palsy with contralateral hemiataxia and is due to an intrinsic or extrinsic lesion in the midbrain. We report a case of Claude's syndrome caused by neurocysticercosis infection. A 68 year-old Asian man was admitted to our hospital because of ataxia, left ptosis, and diplopia. Brain magnetic resonance imaging (MRI) showed a cystic lesion in the midbrain, which was surrounded by ring enhancement and peripheral edema. Neurocysticercosis infection was diagnosed by the cerebral spinal fluid study. The patient was treated with albendazole and steroids. A follow-up brain MRI three months later demonstrated the disappearance of a surrounding brain edema and rim enhancement. The most common cause of Claude's syndrome is cerebrovascular disease and malignancy. However, there is no report caused by neurocysticercosis infection. Therefore, if we encounter Claude's syndrome, we should consider neurocysticercosis infection as one of the etiologic factors

Transcortical Alterations in Na+-K+ ATPase and Microtubule-Associated Proteins Immunoreactivity in the Rat Cortical Atrophy Model Induced by Hypoxic Ischemia

To identify the chronological transcortical change in the contralateral hemisphere following ischemic insults, we investigated the changes in microtubule associated protein (MAP) and Na+-K+ ATPase expressions in the peri-infarct zone and contralateral hemisphere, including the hippocampus. Two days after hypoxic ischemia, Na+-K+ ATPase immunoreactivity was significantly enhanced in the contralateral cortex and was maintained up to 7 days after ischemia, whereas Na+-K+ ATPase immunoreactivity in the peri- and infarct zones was unaffected by hypoxic ischemia. In contrast, 2 to 7 days after ischemia, MAP1A and MAP2 immunoreactivity in the ipsi- and contralateral cortex significantly decreased, whereas in layer V, MAP1 immunoreactivity obviously accumulated in the neurons and their processes. In the hippocampus, 2 days after insults both MAP1A and MAP2 immunoreactivity was significantly reduced within the ipsi- and contralateral hippocampus. In the contralateral hippocampus, however, the distribution of MAP2 immunoreactivity recovered to the sham level 7 days after ischemia, whereas MAP1A immunoreactive axons remained 2 months after ischemia. The results suggest that the unilateral elevation of Na+-K+ ATPase immunoreactivity reflects elevated neuronal activity. In addition, this asymmetric hyperexcitability might play an important role in the recovery or the reorganization of the brain, accompanied by transcortical changes in MAPs expression