• Progress in Medical Physics
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• v.14 no.2
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• pp.90-98
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• 2003

Purpose : A new virtual simulation technique for craniospinal irradiation (CSI) that uses a CT-simulator was developed to improve the accuracy of field and shielding placement as well as patient positioning. Materials and Methods : A CT simulator (CT-SIM) and a 3-D conformal radiation treatment planning system (3D-CRT) were used to develop CSI. The head and neck were immobilized with a thermoplastic mask while the rest of the body was immobilized with a Vac-Loc. A volumetric image was then obtained with the CT simulator. In order to improve the reproducibility of the setup, datum lines and points were marked on the head and body. Virtual fluoroscopy was performed with the removal of visual obstacles, such as the treatment table or immobilization devices. After virtual simulation, the treatment isocenters of each field were marked on the body and on the immobilization devices at the conventional simulation room. Each treatment fields was confirmed by comparing the fluoroscopy images with the digitally reconstructed radiography (DRR) and digitally composited radiography (DCR) images from virtual simulation. Port verification films from the first treatment were also compared with the DRR/DCR images for geometric verification. Results : We successfully performed virtual simulations on 11 CSI patients by CT-SIM. It took less than 20 minutes to affix the immobilization devices and to obtain the volumetric images of the entire body. In the absence of the patient, virtual simulation of all fields took 20 min. The DRRs were in agreement with simulation films to within 5 mm. This not only reducee inconveniences to the patients, but also eliminated position-shift variables attendant during the long conventional simulation process. In addition, by obtaining CT volumetric image, critical organs, such as the eyes and the spinal cord, were better defined, and the accuracy of the port designs and shielding was improved. Differences between the DRRs and the portal films were less than 3 m in the vertebral contour. Conclusion : Our analysis showed that CT simulation of craniospinal fields was accurate. In addition, CT simulation reduced the duration of the patient's immobility. During the planning process. This technique can improve accuracy in field placement and shielding by using three-dimensional CT-aided localization of critical and target structures. Overall, it has improved staff efficiency and resource utilization by standard protocol for craniospinal irradiation.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.225-228
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• 2018

Plasticizers added to thermoplastic polymers are known to shorten the life of products due to the elution to outside, and some of them are harmful to our environment and human body. Since the use of phthalate plasticizers suspected of being carcinogens has been gradually prohibited, there is a need for environmentally friendly plasticizers that can replace them. Most of the substances have a low compatibility with resin, high cost and lack of safety verification. Therefore, in this study, four kinds of norbornene dialkyl ester compounds possessing excellent physical properties, which are also reported as safe compounds from the toxicity evaluation, were added to PVC resin to evaluate the possibility of human exposure by leaching, and also the potential usage as plasticizer candidates alternative to commercial ones including DEHP, DINCH and DOTP. The test was carried out according to the American standard test method (ASTM). The results showed that di-2-ethylhexyl-5-norbornene-2,3-dicarboxylate (DEHN) in aqueous solvents and diisopentyl-5-norbornene-2,3-dicarboxylate (DIPN) compounds in oil solvents were superior or equivalent to DEHP. In addition, all four norbornene compounds showed lower values than 100 ppm, which is considered to have an influence on the environment, indicating that the polar norbornene structure affects the elution.