• Progress in Medical Physics
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• v.9 no.3
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• pp.175-184
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• 1998

The dose distribution evaluation program for the stereotactic radiosurgery treatment planning system using a gamma knife has been built in order to work on PC. And this custom-made dose distribution is compared with that of commercial treatment planning program. 201 source position of a radiation unit were determined manually using a gamma knife collimator draft and geometrical coordinates. Dose evaluation algorithm was modified for our purpose from the original KULA, a commercial treatment planning program. With the composed program, dose distribution at the center of a spherical phantom, 80 mm in diameter, was evaluated into axial, coronal and sagittal image per each collimator. Along with this evaluated data, the dose distribution at a arbitrary point of inside the phantom was compared with those from KULA. Radiochromic film was set up at the center of the phantom and was irradiated by gamma knife, for the verification of dose distribution. In result, the deviation of the dose distribution from that of KULA is less than ${\pm}$3%, which is equivalent to ${\pm}$0.3 mm in 50% isodose distribution for all examined coordinates and film verification. The custom-made program, GPl is proven to be a good tool for the stereotactic radiosurgery treatment planning program.

• Progress in Medical Physics
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• v.3 no.1
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• pp.53-62
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• 1992

Stereotactic implantation of intracranial lesions, and the development of stereotactic convergent irradiation, radiosurgery, techniques have to obtain the accurate coordinates of the tumor locations and that of critical organ. Computed tomography(CT) provides relatively precise imformations of tumor localization and surround the normal organs for conventional radiotherapy. This CT image use to extend for stereotactic radiosurgery procedures. Since the convergent irradiation technique in linear accelerator requires the target center coincident with gantry isocenter or radosurgery frame, the target coordinates must be described in accurately. We used the BRW stereotactic system for describing the target position in CT images This algorithm provides the coordinate conversions for orthogonal or non-orthogonal CT scan image. In this experiments, the target positions have shown the small discripancy within :to.3mm uncertanty in several known target positions in the phantom through the provided programs and it compared to that of BRW stereotactic systems.

• Progress in Medical Physics
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• v.18 no.2
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• pp.93-97
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• 2007

This study was designed to evaluate radiosurgery technique using multiple noncoplanar arc therapy with intensity modulated fine MLC shaped photon beam. The stereotactic radiosurgery was performed with 6-MV X-ray beams from a Clinac 21EX LINAC (Varian, Palo Alto, CA, USA) with a MLC-120, which features a full $40{\times}40cm$ field and is the first MLC for general use that offers 0.5 cm resolution for high precision treatment of small and irregular fields. We used a single isocenter and five gantry-couch combinations with a set of intensity modulated arc therapy. We investigated dosimetric characteristics of 2 cm sized spherical target volume with film (X-OMAT V2 film, Kodak Inc, Rochester NY, USA) dosimetry within $25{\times}25cm$ acrylic phantom. A simulated single isocentric treatment using inversely Planned 3D radiotherapy planning system demonstrated the ability to conform the dose distribution to an spherical target volume. The 80% dose level was adequate to encompass the target volume in frontal, sagittal, and transverse planes, and the region between the 40% and 80% isodose lines was $4.0{\sim}4.5mm$ and comparable to the dose distribution of the Boston Arcs. We expect that our radiosurgery technique could be a treatment option for irregular-shaped large intracranial target.

• Investigative Magnetic Resonance Imaging
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• v.4 no.1
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• pp.7-13
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• 2000

Purpose : To assess the distortion of MRI with the Leksell stereotactic radiosurgery system in variable pulse sequence and imaging plane through phantom study, to find most adequate imaging plane and pulse sequence for stereotactic radiosurgery system. Materials and methods : We made the phantoms for MRI and get images in variable conditions and analyzed the image distortion using image analysis program, and statistically using paired student t-test. Results : The transeverse plane images had acceptable error ranges bless than 1.5mm) in all pulse sequence in both the analysis of fiducial marker in stereotactic G-frame and the phantom study. The coronal plane images had unacceptable large errors (more than 1.7mm) in the analysis of fiducial marker in the stereotactic G-frame, but had corrected small errors (less than 1.5mm) in the phantom study. Conclusion : We find from the phantom study that the present MR machines are adequate for stereotactic surgery system in frequently used pulse sequences, and imaging planes.

• Progress in Medical Physics
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• v.6 no.1
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• pp.59-64
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• 1995

The aim of presentation is to obtain the beam parameters for tratment planning of steretactic radiosurgery. The dosimerical parameters such as TMR, scatter factor, and OAR was measured using diode, film, micro ion chamber, and thimble chanber for water phantom scanning. The results were compared each other. As a result, we determined OAR from film and scatter factor and TMR from diode as a basic data for treatment planning.

• Radiation Oncology Journal
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• v.16 no.4
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• pp.517-529
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• 1998

Purpose : Although many studies have investigated the dosimetric aspects of stereotactic radiosurgery in terms of target volume, the absorbed doses at extracranial sites: especially the lens or thyroid - which are sensitive to radiation for deterministic or stochastic effect -have infrequently been reported. The aim of this study is to evaluate what effects the parameters of radiosurgery have on the absorbed doses of the lens and thyroid in patients treated by stereotactic radiosurgery, using a systematic plan in a humanoid phantom. Materials and Methods : Six isocenters were selected and radiosurgery was planned using the stereotactic radiosurgery system which the Department of Therapeutic Radiology at Seoul National University College of Medicine developed. The experimental radiosurgery plan consisted of 6 arc planes per one isocenter, 100 degrees for each arc range and an accessory collimator diameter size of 2 cm. After 250 cGy of irradiation from each arc, the doses absorbed at the lens and thyroid were measured by thermoluminescence dosimetry. Results : The lens dose was 0.23$\pm$0.08$\%$ of the maximum dose for each isocenter when the exit beam did not pass through the lens and was 0.76$\pm$0.12$\%$ of the maximum dose for each isocenter when the exit beam passed through the lens. The thyroid dose was 0.18$\pm$0.05$\%$ of the maximum dose for each isocenter when the exit beam did not pass through the thyroid and was 0.41$\pm$0.04$\%$ of the maximum dose for each isocenter when the exit beam Passed through the thyroid. The passing of the exit beam is the most significant factor of organ dose and the absorbed dose by an arc crossing organ decides 80$\%$ of the total dose. The absorbed doses of the lens and thyroid were larger as the isocenter sites and arc planes were closer to each organ. There were no differences in the doses at the surface and 5 mm depth from the surface in the eyelid and thyroid areas. Conclusion : As the isocenter and arc plane were placed closer to the lens and thyroid, the doses increased. Whether the exit beams passed through the lens or thyroid greatly influenced the lens and thyroid dose. The surface dose of the lens and thyroid consistently represent the tissue dose. Even when the exit beam passes through the lens and thyroid, the doses are less than 1$\%$ of the maximum dose and therefore, are too low to evoke late complications, but nevertheless, we should try to minimize the thyroid dose in children, whenever possible.

• Progress in Medical Physics
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• v.23 no.3
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• pp.169-176
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• 2012

Frameless method in brain radiosurgery has advantages relative to rigid head-frame method in terms of patient friendly and flexible application of multi-fractionation. However, it has also disadvantages and the most negative point is that it cannot control the patient motion during treatment as lowly as the level of the frame-based radiosurgery, which could affect to the treatment accuracy. In the present study, we analyzed the geometric uncertainty of the intra-fraction motion using the actual treatment records of 294-CyberKnife treatments for brain tumors. Based on the analysis, we statistically presented the magnitude of intra-fraction motion in frameless radiosurgy. The result could provide the quantitative information to determine the adequate treatment margins to compensate the intra-fraction movements.

• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.389-395
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• 2014

The research was carried out to develop a animal model of malignant brain tumor for the researches in glioblastoma multiform (GBM) diagnosis and therapy. C6 cells were transplanted into the right striatum of SD rat using stereotactic instrument for the development. The developed animal model was verified by MRI and H&E stain assay of anatomicohistological examination. The MRI observations showed that the tumor developed at the injection site at the 7 days after glioblastoma inoculation. At 14 days post inoculation, the tumor grew to a large volume occupying almost a half of the right cerebral hemisphere. It was confirmed that the expression of excessive mitosis and pleomorphism in anatomicohistological examination. The developed animal model must be necessary and useful tool for the in vivo level research in the development of the new modality for the diagnosis and therapy of brain cancer.

• The Journal of Korean Society for Radiation Therapy
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• v.16 no.2
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• pp.1-8
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• 2004

Purpose : What confirm a patient's set-up precisely is an important factor in stereotactic radiosurgery Especially, the tumor is moved by respiration in case of lung cancer. So it is difficult to confirm a exact location by L-gram or EPID. I will verify a exact patient's set-up about this sort of problem by verification system(exactrac 3.0) Materials and Methods : The patient that had lung cancer operated on stereotactic radiosurgery is composed of 6 people. The 5 patients use an ABC tool and 1 patient doesn't use it. I got such a patient's L-gram and EPID image by Body frame(elekta, sweden), compared Ant. image with Lat. one, and then confirmed a set-up. I fused DRR image of CT and X-ray image of Verification system(exactrac 3.0) 3 dimensional, analyzed the coordinate value(vertical, longitudinal, lateral), and then confirmed a difference of existing method. Results : In case of L-gram and EPID, we judge an exact of the patient's set-up subjectively, and on we could treat the patient with radiation. As a result of using Verification system(exactrac 3.0), coordinate value(vertical, longitudinal, lateral) of patient's set-up was comprised within 5mm. We could estimate a difference of the coordinate value visually and objectively. Consequently, Verification system(exactrac 3.0) was useful in judging an exact patient's set-up. Conclusion : In case of Verification system(exactrac 3.0), we can confirm an exact patient's set-up at any time whenever, However, there are several kinds of the demerit. First, it is a complex process of confirmation than the existing process. Second, thickness of CT scan slice is within 3mm. The last, X-ray image has to have shown itself clearly. If we solve this problem. stereotactic radiosurgery will be useful in treating patients why we can confirm an exact patient's positioning easily.

• Progress in Medical Physics
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• v.18 no.1
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• pp.1-6
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• 2007

A system to non-invasively fix and monitor eye by a head mounted display (HMD) with a CCD camera for stereotactic radiotherapy (SRS) of uveal melanoma has been developed and implemented clinically. The eye fixing and monitoring system consists of a HMD showing patient a screen for fixing eyeball, a CCD camera monitoring patient's eyeball, and an immobilization mask. At flrst, patient's head was immobilized with a mask. Then, patient was Instructed to wear HMD, to which CCD camera was attached, on the mask and see the given reference point on its screen. While patient stared at the given point in order to fix eyeball, the camera monitored Its motion. Four volunteers and one patient of uveal melanoma for SRS came into this study. For the volunteers, setup errors and the motion of eyeball were analyzed. For the patient, CT scans were peformed, with patient's wearing HMD and fixing the eye to the given point. To treat patient under the same condition, daily CT scans were also peformed before every treatment and the motion of lens was compared to the planning CT Setup errors for four volunteers were within 1mm and the motion of eyeball was fixed within the clinically acceptable ranges. For the patient with uveal melanoma, the motion of lens was fixed within 2mm from daily CT scans. An eye fixing and monitoring system allowed Immobilizing patient as well as monitoring eyeball and was successfully implemented in the treatment of uveal melanoma for SRS.