• Progress in Medical Physics
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• v.15 no.3
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• pp.167-172
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• 2004

A Siemens HD-270 MLC$^{TM}$, a virtual-micro MLC, allows to the application of a smooth field edge method due to the finite leaf-width of MLC. This technique was implemented into a Pinnacle planning system in order to evaluate the dose distributions during the planning stage. The necessary dosimetric aspects, such as undulation and effective penumbra, were investigated with variations in the resolutions of a virtual-micro MLC and field edge angle. The positional accuracy of the couch movement was also assessed for clinical implementation. The overhead time for planning and treatment was confirmed as negligible.e.

• Progress in Medical Physics
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• v.13 no.1
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• pp.32-36
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• 2002

For Intensity Modulated Radiation Therapy(IMRT), the spatial resolution of intensity map(IM) is limited by the width of multi-leaf collimator, which would make an effect on the conformity of the target, as well as organs at risk. Several Methods are suggested to increase the spatial resolution, which can be categorized by the hardware-dependent technique and the software-based technique. However the best solution might be to make the width of MLC finer. it has several obstacles in the respects of technical difficulty and cost. This preliminary study is designed to investigate the clinical effectiveness of the virtual-micro IMRT(VMIMRT) technique, one of the software-based technique. A particular intensity map was created, which has 42$\times$54 pixel dimension ,0.5cm pixel size and 15 intensity levels. Using this intensity map, segment fields of IMRT were generated with 1$\times$lcm, 0.5$\times$1cm, 0.5$\times$0.5cm(VMIM) beamlet size, respectively As results, we found that there was no evidence of improvement for VMIMRT, compared with the 0.5$\times$lcm beamlet size which can be delivered by 1cm width MLC. The reason seems to be due to the constraint of VMIMRT. Further study is required to prove the benefit of the VIMRT in clinical case like head and neck cancer, where is expected that higher resolution than 1cm is necessary.