• 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.

• Progress in Medical Physics
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• v.9 no.2
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• pp.89-94
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• 1998

To make practical application of the MR image for stereotactic radiosurgery, the target point-achieved by acquisition of MR image in stereotactic radiosurgery planning system must agree with the actual isocenter of irradiation in real treatment. And the amount of distortion of the MR image must be known to make a correction for the agreement. A radish containing abundant water content was chosen as a homogeneous phantom for the purpose of verification of the agreement in this experiment. A dosimetric film was firmly attached to the small specially fabricated acryl plate and needle puncture was made through the film just into the acryl plate and a drop of oil was dropped into the hole of the film. The acryl plate with film was inserted into the radish and the dorp of oil represented the target point in MR image. After the image acquisition by stereotatic radiosurgery planning system, we achieved stereotactic coordinate of the target point represented by the oil drop. And we proceeded to actual irradiation to the target point according to the procedure of stereotactic radiosurgery. After the irradiation, the film in the radish was developed and processed and the degree of coincidence between the center of the radiation distribution and the target point represented by the hole in the film was measured. The discrepancy between two points was under 0.5 mm. so we could confirm good coincidence in homogeneous phantom such as radish. On the other hand, authors tried to use our home-made device for estimation of distortion of MR image.

• The Journal of Korean Society for Radiation Therapy
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• v.23 no.1
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• pp.1-6
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• 2011

Purpose: Immobilizations used in order to maintain the reproducibility of a patient set-up and the stable posture for a long period are important more than anything else for the accurate treatment when the stereotactic body radiotherapy is underway. So the purpose of this study is to adapt the optimum immobilizations for the stereotactic body radiotherapy by comparing two commercial immobilizations with the self-manufactured immobilizations. Materials and Methods: Five people were selected for the experiment and three different immobilizations (A: Wing-board, B: BodyFix system, C: Arm up holder with vac-lock) were used to each target. After deciding on the target's most stable respiratory cycles, the targets were asked to wear a goggle monitor and maintain their respiration regularly for thirty minutes to obtain the respiratory signals. To analyze the respiratory signal, the standard deviation and the variation value of the peak value and the valley value of the respiratory signal were separated by time zone with the self-developed program at the hospital and each tie-downs were compared for the estimation by calculating a comparative index using the above. Results: The stability of each immobilizations were measured in consideration of deviation changes studied in each respiratory time lapse. Comparative indexes of each immobilizations of each experimenter are shown to be A: 11.20, B: 4.87, C: 1.63 / A: 3.94, B: 0.67, C: 0.13 / A: 2.41, B: 0.29, C: 0.04 / A: 0.16, B: 0.19, C: 0.007 / A: 35.70, B: 2.37, C: 1.86. And when all five experimenters wore the immobilizations C, the test proved the most stable value while four people wearing A and one man wearing D expressed relatively the most unstable respiratory outcomes. Conclusion: The self-developed immobilizations, so called the arm up holder vac-lock for the stereotactic body radiotherapy is expected to improve the effect of the treatment by decreasing the intra-fraction organ motions because it keeps the respiration more stable than other two immobilizations. Particularly in case of the stereotactic body therapy which requires the maintenance of set-up state for a long time, the self-developed immobilizations is thought to more useful for stereotactic body radiotherapy rather than the rest two immobilizations with instable respiratory cycle as time passes.

• The Journal of Korean Society for Radiation Therapy
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• v.20 no.2
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• pp.109-113
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• 2008

Purpose: To evaluate the detector dependency in the various collimator size for Stereotactic Radiosugery (SRS). Materials and Methods: This study was performed with 6 MV photon beam (Varian 21EX, Varian, US) and the measurement detectors are used by ion chamber CC01, CC13 (Wellhofer, Germany) and stereotactic diode detector (SFD, Wellhofer, Germany). SRS collimator size was used by ${\varphi}$5, 10, 20, 30 mm (Brain Lab, Germany). Percentage depth dose (PDD) was measured at SSD 100 cm and field size 10×10 cm from individual detectors. Ouput factor was measured by using same setup of PDD and with maximum dose depth. Data was normalized at field size $10{\times}10\;cm$. Beam profile was measured at SSD 100 cm in SRS collimator ${\varphi}$10, 30 mm and field $10{\times}10\;cm$ and a comparison of FWHM (full width half maximum), penumbra width (20~80%). Results: The CC13 detector was overestimated 16% than other detectors from the PDD in the 5 mm collimator. Output factors were underestimated CC01 28%, CC13 72% in the 5 mm collimator and CC01 9.6%, CC13 25% in the 10 mm collimator than the SFD. Maximum difference was 3% at the FWHM of the dose profile in the 10 mm collimator and difference of the 30 mm collimator was 0% at the FWHM. Penumbra width was increased CC01 122%, CC13 194% in the 10 mm collimator and CC01 68%, CC13 185% in the 30 mm collimator than the SFD. Conclusion: It is very important for accurate dosimetry to select a detector in small field. The SFD was considered with the most accurate dosimeter for small collimator dosimetry in this study.

• Radiation Oncology Journal
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• v.18 no.2
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• pp.150-156
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• 2000

Purpose : Stereotactic radiation therapy (SRT) can deliver highly focused radiation to a small and spherical target lesion with very high degree of mechanical accuracy. For non-spherical and large lesions, however, inclusion of the neighboring normal structures within the high dose radiation volume is inevitable in SRT This is to report the beam shaping using the partial closure of the independent jaw in SRT and the verification of dose calculation and the dose display using a home-made soft ware. Materials and Methods : Authors adopted the idea to partially close one or more independent collimator jaw(5) in addition to the circular collimator cones to shield the neighboring normal structures while keeping the target lesion within the radiation beam field at all angles along the arc trajectory. The output factors (OF's) and the tissue-maximum ratios (TMR's) were measured using the micro ion chamber in the water phantom dosimetry system, and were compared with the theoretical calculations. A film dosimetry procedure was peformed to obtain the depth dose profiles at 5 cm, and they were also compared with the theoretical calculations, where the radiation dose would depend on the actual area of irradiation. Authors incorporated this algorithm into the home-made SRT software for the isodose calculation and display, and was tried on an example case with single brain metastasis. The dose-volume histograms (DVH's) of the planning target volume (PTV) and the normal brain derived by the control plan were reciprocally compared with those derived by the plan using the same arc arrangement plus the independent collimator jaw closure. Results : When using 5.0 cm diameter collimator, the measurements of the OF's and the TMR's with one independent jaw set at 30 mm (unblocked), 15.5 mm, 8.6 mm, and 0 mm from th central beam axis showed good correlation to the theoretical calculation within 0.5% and 0.3% error range. The dose profiles at 5 cm depth obtained by the film dosimetry also showed very good correlation to the theoretical calculations. The isodose profiles obtained on the home-made software demonstrated a slightly more conformal dose distribution around the target lesion by using the independent jaw closure, where the DVH's of the PTV were almost equivalent on the two plans, while the DVH's for the normal brain showed that less volume of the normal brain receiving high radiation dose by using this modification than the control plan employing the circular collimator cone only. Conclusions : With the beam shaping modification using the independent jaw closure, authors have realized wider clinical application of SRT with more conformal dose planning. Authors believe that SRT, with beam shaping ideas and efforts, should no longer be limited to the small spherical lesions, but be more widely applied to rather irregularly shaped tumors in the intracranial and the head and neck regions.

• Radiation Oncology Journal
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• v.18 no.4
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• pp.251-256
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• 2000

Purpose : To evaluate efficacy and complication of stereotactic radiosurgery using stereotactic body frame. Methods and Materials :From December 1997 to June 1999, 11 patients with primary and metastatic tumors were treated with stereotactic radiosurgery using stereotactic body frame(Precision TherapyTu). Three patients were treated with primary hepatoma and seven with metastatic tumor from liver, lung, breast, trachea and one with arteriovenous malformation on neck. We used vacuum pillow for immobilization and made skin marker on sternum and tibia area with chest marker and leg marker. Diaphragm control was used for reducing movement by respiration. CT-simulation and treatment planning were peformed. Set-up error was checked by CT-Simulator before each treatment. Dose were calculated on the 80$\~$90$\%$ isodose of isocenter dose and given consecutive 3 fractions for total dose of 30 Gy (10 Gy/fraction). Results :Median follow-up was 12 months. One patient (9$\%$) showed complete response and four Patients (36$\%$) showed partial response and others showed stable disease. Planning target volumes (PTV) ranged from 3 to 111 cc (mean 18.4 n). Set-up error was within 5 mm in all directions (X, Y, Z axis). There was no complication in all patients. Conclusion :In Primary and metastatic tumors, stereotactic body frame is very safe, accurate and effective treatment modality.

• The Journal of Korean Society for Radiation Therapy
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• v.12 no.1
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• pp.58-62
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• 2000

• The Journal of Korean Society for Radiation Therapy
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• v.13 no.1
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• pp.64-67
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• 2001

• The Science & Technology
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• no.9 s.460
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• pp.102-103
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• 2007

• Journal of The Korean Radiological Technologist Association
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• v.25 no.1
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• pp.65.1-65.1
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• 1999