• Progress in Medical Physics
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• v.14 no.4
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• pp.225-233
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• 2003

The goal of a radiation treatment plan is to deliver a homogeneous dose to a target with minimal irradiation of the adjacent normal tissues. Dose uniformity is especially important for stereotactic radiosurgery using a linear accelerator. The dose uniformity and high dose delivery of a single spherical dose distribution exceed 70％. This also results with a similar stereotactic radiosurgical plan using a Gamma Knife. The dose distribution produced in a stereotactic radiosurgical plan using a Gamma Knife and Linear accelerator is spherical, and the application of the sphere packing arrangement in a real radiosurgical plan requires much time and skill. In this study, we found a characteristic of dose distribution with transformation of beam parameters that must be considered in a radiosurgical plan for effective radiosurgery. First, we assumed a cylinder type tumor model and a cube type tumor model. Secondly, the results of the tumor models were compared and analyzed with dose profiles and DVH_(Dose Volume Histogram) representative dose distribution. We found the optimal composition of beam parameters_(i.e. collimator size, number of isocenter, gap of isocenters etc.), which allowed the tumor models to be involved in the isodose curve at a high level. In conclusion, the characteristics found in this study are helpful for improving the effectiveness and speed of a radiosurgical plan for stereotactic radiosurgery.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2005.04a
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• pp.47-50
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• 2005

The aim of radiosurgery cures a patient to deliver the lower dose at the normal organ and the higher dose at the tumor. Therefore accuracy of the dose is required to gain effect of radiosurgery in surgical planning. In this paper, we developed the methods of target approximation for a fast treatment planning. Nominally, the stereotactic radiosurgery(SRS) using Linac and Gamma knife produces spherical dose distribution through circular collimators using multiple arcs and 201 holes on semi-spherical helmet by $^{60}Co$. We developed an automatic radiosurgical plan about spherical packing arrangement. To automatically plan the SRS, new planning methods based on cylinder and cube structure for target shaping was developed. This approach using heuristic and stochastic algorithm is a useful radiosurgical plan without restrictions in the various tumor shapes and the different modalities.

• Progress in Medical Physics
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• v.16 no.1
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• pp.24-31
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• 2005

The stereotactic radiosurgery (SRS) describes a method of delivering a high dose of radiation to a small tar-get volume in the brain, generally in a single fraction, while the dose delivered to the surrounding normal tissue should be minimized. To perform automatic plan of the SRS, a new method of multi-isocenter/shot linear accelerator (linac) and gamma knife (GK) radiosurgery treatment plan was developed, based on a physical lattice structure in target. The optimal radiosurgical plan had been constructed by many beam parameters in a linear accelerator or gamma knife-based radiation therapy. In this work, an isocenter/shot was modeled as a sphere, which is equal to the circular collimator/helmet hole size because the dimension of the 50% isodose level in the dose profile is similar to its size. In a computer-aided system, it accomplished first an automatic arrangement of multi-isocenter/shot considering two parameters such as positions and collimator/helmet sizes for each isocenter/shot. Simultaneously, an irregularly shaped target was approximated by cubic structures through computation of voxel units. The treatment planning method by the technique was evaluated as a dose distribution by dose volume histograms, dose conformity, and dose homogeneity to targets. For irregularly shaped targets, the new method performed optimal multi-isocenter packing, and it only took a few seconds in a computer-aided system. The targets were included in a more than 50% isodose curve. The dose conformity was ordinarily acceptable levels and the dose homogeneity was always less than 2.0, satisfying for various targets referred to Radiation Therapy Oncology Group (RTOG) SRS criteria. In conclusion, this approach by physical lattice structure could be a useful radiosurgical plan without restrictions in the various tumor shapes and the different modality techniques such as linac and GK for SRS.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.75-77
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• 2004

Stereotactic radiosurgery(SRS) is a technique to deliver a high dose to a particular target region and a low dose to the critical organ using only one or a few irradiations while the patient is fixed with a stereotactic frame. The optimized plan is decided by repetitive work to combine the beam parameters and identify prescribed doses level in a tumor, which is usually called a trial and error method. This requires a great deal of time, effort, and experience. Therefore, we developed the automatic arrangement of multi-isocenter within irregularly shaped tumor. At the arbitrary targets, which is this method based on the voxel unit of the space, well satisfies the dose conformity and dose homogeneity to the targets relative to the RTOG radiosurgery plan guidelines