• 대한방사선치료학회:학술대회논문집
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• 2000.04a
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• pp.14-14
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• 2000

• Progress in Medical Physics
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• v.24 no.3
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• pp.145-153
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• 2013

Stereotactic body radiation therapy (SBRT) is increasingly used to treat spinal metastases. To achieve the highest steep dose gradients and conformal dose distributions of target tumors, intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques are essential to spine radiosurgery. The purpose of the study was to qualitatively compare IMRT and VMAT techniques with International Spine Radiosurgery Consortium (ISRC) contoured consensus guidelines for target volume definition. Planning target volume (PTV) was categorized as TB, $T_{BPT}$ and $T_{ST}$ depending on sectors involved; $T_B$ (vertebral body only), $T_{BPT}$ (vertebral body+pedicle+transverse process), and $T_{ST}$ (spinous process+transverse process). Three patients treated for spinal tumor in the cervical, thoracic, and lumbar region were selected. Eacg tumor was contoured by the definition from the ISRC guideline. Maximum spinal cord dose were 12.46 Gy, 12.17 Gy and 11.36 Gy for $T_B$, $T_{BPT}$ and $T_{ST}$ sites, and 11.81 Gy, 12.19 Gy and 11.99 Gy for the IMRT, RA1 and RA2 techniques, respectively. Average fall-off dose distance from 90% to 50% isodose line for $T_B$, $T_{BPT}$, and $T_{ST}$ sites were 3.5 mm, 3.3 mm and 3.9 mm and 3.7 mm, 3.7 mm and 3.3 mm for the IMRT, RA1 and RA2 techniques, respectively. For the most complicated target $T_{BPT}$ sites in the cervical, thoracic and lumbar regions, the conformity index of the IMRT, RA1 and RA2 is 0.621, 0.761 and 0.817 and 0.755, 0.796 and 0.824 for rDHI. Both IMRT and VMAT techniques delivered high conformal dose distributions in spine stereotactic radiosurgery. However, if the target volume includes the vertebral body, pedicle, and transverse process, IMRT planning resulted in insufficient conformity index, compared to VMAT planning. Nevertheless, IMRT technique was more effective in reducing the maximum spinal cord dose compared to RA1 and RA2 techniques at most sites.

• Radiation Oncology Journal
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• v.14 no.2
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• pp.149-158
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• 1996

Purpose : To get an accute steepness of dose gradients at outside the target volume in intracranial lesion and a less limitation of beam selection avoiding the high dose at normal brain tissue, this Photon Knife Radiosurgery System was developed in order to provide the three-dimensional dose distribution through the reconstruction of CT scan and the combined stereotactic trans-multiarc beam mode based on linear accelerator photon beam. Materials and methods : This stereotactic radiosurgery, Photon Knife based on linear accelerator photon beam was provided the non-coplanar multiarc and trans-multiarc irradiations. The stereotactic trans-multiarc beam mode can be obtained from the patient position in decubitus. This study has provided the 3-dimensional isodose curve and anatomical structures with the surface rendering technique. The dose distribution from the combined two trans-multiarcs (2M 2TM) was compared to that of four non-coplanar multiarcs (4M) with same collimator size of 25 mm in a diameter and total gantry movements. Results : In this study, it shows that the dose distributions of stereotactic beam mode are significantly depended on the selected couch and gantry angle in same collimator size. Practical dose distribution of combined stereotactic trans-multiarc beam has shown a more small rim thickness than that of the non-coplanar multiarc beam mode in axial, sagittal and coronal plane in our study. 3-Dimensional dose line displayed with surface rendering of irregular target shape is helpful to determine the target dose and to predict the prognosis in follow-up radiosurgery. Conclusions : 3-Dimensional dose line displayed with surface rendering of irregular target shape is essential in stereotactic radiosurgery. This combined stereotactic trans-multiarc beam has shown a less limitation of the selection couch and gantry beam angles for the target surrounding critical organs. It has shown that the dose distribution of combined trans-multiarc beam greatly depended on the couch and gantry angles. In our experiments, the absorbed dose has been decreased to $27%$ / mm in maximum at the interval of $50\%$ to $80\%$ of isodose line.

• The Journal of Korean Society for Radiation Therapy
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• v.11 no.1
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• pp.43-48
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• 1999

Purpose : For practical application of the MR image for stereotactic radiosurgery, the target point achieved by acquisition of MR image in a relatively homogeneous phantom has to agree with the actual isocenter of irradiation in real radiosurgery and the amount of distortion of the MR image should be known. Materials and Methods : A dosimetric film with a random target point was inserted into a radish vertically and horizontally on axis Z and they were fixed with a headring. After image acquisition by stereotactic radiosurgery planning system, we achieved stereotactic coordinate of the target point and examined irradiation using the coordinate acquired as isocenter. After the irradiation, the film in the radish was developed and processed and the degree of coincidence between the target point marked on the film and the center of the radiation distribution. In order to measure the degree of distortion of the MR image in a different way, an acryl phantom was made and punctures were made at intervals of 1 cm and a drop of oil was dropped into it. Then, it was inserted into the radish vertically and horizontally on axis Z to acquire the MR image. Each coordinate was achieved and the estimation of distortion of MR image was made both in vertical and horizontal directions Results : The film from the radio was developed and for the one inserted vertically on axis Z, there was a good coincidence in the discrepancy between the target point marked on the film and the center of the radiation distribution. For the one inserted horizontally, the discrepancy between them was under 0.5 mm. As a result of estimating distortion of MR image using acryl, the discrepancy was under 0.45 mm in the case of the phantom inserted vertically on axis Z, and that of the one inserted horizontally was 1.4 mm. Conclusion : We were able to confirm good coincidence in homogeneous phantom in actual treatment position of radiosurgery using the MR image and the discrepancy measured in the analysis of distortion of the MR image did not exceed the permissible level. Therefore, it was evident the system of the hospital is suitable for radiosurgery using MR image.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.30 no.1
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• pp.65-68
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• 2004

CyberKnife is a stereotactic radiosurgery system which could be used to treat many tumors and lesions. It provides the surgeon unparalleled flexibility in targeting using a compact light linear accelerator mounted on a robotic arm. Advanced image guidance technology tracks patient and target position during treatment, ensuring accuracy without the use of an invasive head frame. CyberKnife with Dynamic Tracking Software is cleared to provide radiosurgery for lesions anywhere in the body when radiation treatment is indicated. It has often been used to radiosurgically treat otherwise untreatable tumors and malformations. Moreover, this instrument treats tumors at body sites, most of which are unreachable by other stereotactic systems. Compared with conventional radiotherapy, it is fundamentally different that using non-invasive, frameless, no excessive radiation exposure to normal tissue. In oral malignant neoplasm, surgical excision and radiation therapy should be tried first, additionally chemotherapy could be considered. However, after failure of conventional therapies, patients had poor systemic condition and surgical limitation. So, CyberKnife could be a suitable therapy. A 49 years man was referred in recurred mandibular cancer treated by radiotherapy. The tumor was considered inoperable, because of extensive invasion and was not expected to good response to conventional therapies. We experienced a case of CyberKnife after 4 cycle chemotherapies, so we report it with review of literature.

• Journal of Korean Neurosurgical Society
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• v.58 no.4
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• pp.379-384
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• 2015

Objective : To investigate the risks and pattern of evolution of peritumoral brain edema (PTE) after stereotactic radiosurgery (SRS) for asymptomatic intracranial meningiomas. Methods : A retrospective study was conducted on 320 patients (median age 56 years, range 24-87 years) who underwent primary Gamma Knife radiosurgery for asymptomatic meningiomas between 1998 and 2012. The median tumor volume was 2.7 cc (range 0.2-10.5 cc) and the median follow-up was 48 months (range 24-168 months). Volumetric data sets for tumors and PTE on serial MRIs were analyzed. The edema index (EI) was defined as the ratio of the volume of PTE including tumor to the tumor volume, and the relative edema indices (rEIs) were calculated from serial EIs normalized against the baseline EI. Risk factors for PTE were analyzed using logistic regression. Results : Newly developed or increased PTE was noted in 49 patients (15.3%), among whom it was symptomatic in 28 patients (8.8%). Tumor volume larger than 4.2 cc (p<0.001), hemispheric tumor location (p=0.005), and pre-treatment PTE (p<0.001) were associated with an increased risk of PTE. rEI reached its maximum value at 11 months after SRS and decreased thereafter, and symptoms resolved within 24 months in most patients (85.7%). Conclusion : Caution should be exercised in decision-making on SRS for asymptomatic meningiomas of large volume (>4.2 cc), of hemispheric location, or with pre-treatment PTE. PTE usually develops within months, reaches its maximum degree until a year, and resolves within 2 years after SRS.

• Radiation Oncology Journal
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• v.31 no.4
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• pp.234-238
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• 2013

Purpose: Esophageal tolerance is needed to guide the safe administration of stereotactic radiosurgery (SRS). We evaluated comprehensive dose-volume parameters of acute esophageal toxicity in patients with spinal metastasis treated with SRS. Materials and Methods: From May 2008 to May 2011, 30 cases in 27 patients with spinal metastasis received single fraction SRS to targets neighboring esophagus. Endpoints evaluated include length (mm), volume (mL), maximal dose (Gy), and series of dose-volume thresholds from the dose-volume histogram (volume of the organ treated beyond a threshold dose). Results: The median time from the start of irradiation to development of esophageal toxicity was 2 weeks (range, 1 to 12 weeks). Six events of grade 1 esophageal toxicity occurred. No grade 2 or higher events were observed. $V_{15}$ of external surface of esophagus was found to predict acute esophageal toxicity revealed by multivariate analysis (odds radio = 1.272, p = 0.047). Conclusion: In patients with spinal metastasis who received SRS for palliation of symptoms, the threshold dose-volume parameter associated with acute esophageal toxicity was found to be $V_{15}$ of external surface of esophagus. Restrict $V_{15}$ to external surface of esophagus as low as possible might be safe and feasible in radiosurgery.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.13
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• pp.5279-5284
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• 2015

Background: The study analyzed the long term clinical outcomes of pituitary adenoma cases treated with the first Thailand installation of a dedicated Linac-based stereotactic radiation machine (X-Knife). Materials and Methods: A retrospective review of 115 consecutive pituitary adenoma patients treated with X-Knife at the Faculty of Medicine, Ramathibodi Hospital, Bangkok, Thailand from 1997 to 2003 was performed. Stereotactic radiosurgery (SRS) was selected for 21 patients (18%) including those with small tumors (${\leq}3cm$) located ${\geq}5mm$. from the optic apparatus, whereas the remaining 94 patients (82%) were treated with fractionated stereotactic radiotherapy (FSRT). Results: With a median follow-up time of 62 months (range, 21-179), the six-year progression free survival was 95% (93% for SRS and 95% for FSRT). The overall hormone normalization at 3 and 5 years was 20% and 30%, respectively, with average time required for normalization of approximately 16 months for SRS and 20 months for FSRT. The incidence of new hypopituitarism was 10% in the SRS group and 9% in the FSRT group. Four patients (5%) developed optic neuropathy (1 in the SRS group and 3 in the FSRT group). Conclusions: Linac-based SRS and FSRT achieved similar high local control rates with few complications in pituitary adenoma cases. However, further well designed, randomized comparative studies between SRS versus FSRT particularly focusing on hormone normalization rates are required.

• The Journal of Korean Society for Radiation Therapy
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• v.8 no.1
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• pp.7-12
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• 1996

• 대한방사선치료학회:학술대회논문집
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• 2004.06a
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• pp.15-15
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• 2004