• Progress in Medical Physics
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• v.10 no.2
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• pp.89-94
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• 1999

We developed a sterotactic radiosurgery system which is comprised of 1) collimators with small circular aperture, 2) an angiographic target localizer, 3) a target localizer used for alignment of planned target position with isocenter of treatment machine, and 4) a treatment planning system named LinaPel. In this study, we performed a series of treatment simulations to specify and analyze geometrical errors contained our in-house radiosurgery system. As results, 1) using Geometrical Phantom(Radionics,USA), the accuracy of target localization by LinaPel was determined as Avg. =(equation omitted) the accuracy of mechanical isocenter was found out to be 0.6 $\pm$ 0.2 mm, 3) the positional difference of target localization which determined by CT and angiography was 0.8 mm, and their size difference was 1.5 mm, and 4) the positional error during whole treatment was found out to be 0.9 $\pm$ 0.3 mm. With these results, we concluded that our in-house radiosurgery system can be used clinically. However, these range of accuracies need periodical quality assurance strongly.

• Radiation Oncology Journal
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• v.20 no.2
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• pp.179-185
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• 2002

Purpose : For the purpose of quality assurance of self-developed stereotactic radiosurgery system, a multi-purpose phantom was fabricated, and accuracy of radiation dose distribution during radiosurgery was measured using this phantom. Materials and Methods : A farmer chamber, a 0.125 cc ion chamber and a diode detector were used for the dosimetry. Six MV x-ray from a linear accelerator (CL2100C, Varian) with stereotactic radiosurgery technique (Green Knife) was used, and multi-purpose phantom was attached to a stereotactic frame (Fisher type). Dosimetry was done by combinations of locations of the detectors in the phantom, fixed or arc beams, gantry angles $(20^{\circ}\~100^{\circ})$, and size of the circular tertiary collimators (inner diameters of $10\~40\;mm$). Results : The measurement error was less than $0.5\%$ by Farmer chamber, $0.5\%$ for 0.125 cc ion chamber, and less than $2\%$ for diode detector for the fixed beam, single arc beam, and 5-arc beam setup. Conclusion : We confirmed the accuracy of dose distribution with the radiosurgery system developed in our institute and the data from this study would be able to be effectively used for the improvement of quality assurance of stereotactic radiosurgery or fractionated stereotactic radiotherapy system.

• Radiation Oncology Journal
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• v.19 no.2
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• pp.87-94
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• 2001

Purpose : To evaluate the role of LINAC-based stereotactic radiosurgery (SRS) in the management of meningiomas, we reviewed clinical response, image response, neurological deficits for patients treated at our institution. Methods and materials : Between February 1995 and December 1999, twenty-six patients were treated with SRS. Seven patients had undergone prior resection. Nineteen patients received SRS as the initial treatment. There were 7 male and 19 female patients. The median age was 51 years (range, $14\~67\;years$). At least one clinical symptom presented at the time of SRS in 17 patients and cranial neuropathy was seen in 7 patients. The median tumor volume was $4.7\;cm^3\;(range,\;0.7\~16.5\;m^3)$. The mean marginal dose was 15 Gy (range, $10\~20\;Gy$), delivered to the $80\%$ isodose surface (range, $46\~90\%$). The median clinical and imaging follow-up periods were 27 months (range, 1-71 months) and 25 months (range, $1\~52\;months$), respectively. Results : Of 14 patients who had clinical follow-up of one year or longer, thirteen patients $(93\%)$ were improved clinically at follow-up examination. Clinical symptom worsened in one patient at 4 months after SRS as a result of intratumoral edema, who underwent surgical resection at 7 months. OF 14 patients who had radiologic follow-up of one year or longer, tumor volume decreased in 7 patients $(50\%)$ at a median of 11 months (range, $6\~25\;months$), remained stable in 6 patients $(43\%)$, and increased in one patient $(7\%)$, who underwent surgical resection at 44 months. New radiation-induced neurological deficits developed in six patients $(23\%)$. Five patients $(19\%)$ had transient neurological deficits, completely resolved by conservative treatment including steroid therapy. Radiation-induced brain necrosis developed in one patient $(3.8\%)$ at 9 months after SRS who followed by surgical resection of tumor and necrotic tissue. Conclusions : LINAC-based SRS proves to be an effective and safe management strategy for small to moderate sized meningiomas, inoperable, residual, and recurrent, but long-term follow-up will be necessary to fully evaluate its efficacy. To reduce the radiation-induced neurological deficit for large size meningioma and/or in the proximity of critical and neural structure, more delicate treatment planning and optimal decision of radiation dose will be necessary.

• Progress in Medical Physics
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• v.12 no.2
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• pp.171-175
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• 2001

We analyze the relation of dose volume histogram, conformity index and homogeneity index based on RTOG9005 for treatment planning result between framed based stereotactic radiosurgery(SRS) system and frameless SRS/T system to verify the difference of two systems in the intracranial target. There is same treatment planning result by two treatment planning systems.

• Radiation Oncology Journal
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• v.27 no.3
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• pp.163-168
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• 2009

Purpose: This study was a retrospective evaluation of the efficacy of stereotactic radiosurgery (SRS) in patients with >4 metastases to the brain. Materials and Methods: Between January 2004 and December 2006, 68 patients with $\geq$4 multiple brain metastases were included and reviewed retrospectively. Twenty-nine patients received SRS and 39 patients received whole brain radiotherapy (WBRT). Patients with small cell lung cancers and melanomas were excluded. The primary lesions were non-small cell lung cancer (69.0%) and breast cancer (13.8%) in the SRS group and non-small cell lung cancer (64.1%), breast cancer (15.4%), colorectal cancer (12.8%), esophageal cancer (5.1%) in the WBRT group. SRS involved gamma-knife radiosurgery and delivered 10~20 Gy (median, 16 Gy) in a single fraction with a 50% marginal dose. WBRT was delivered daily in 3 Gy fractions, for a total of 30 Gy. After completion of treatment, a follow-up brain MRI or a contrast-enhanced brain CT was reviewed. The overall survival and intracranial progression-free survival were compared in each group. Results: The median follow-up period was 5 months (range, 2~19 months) in the SRS group and 6 months (range, 4~23 months) in the WBRT group. The mean number of metastatic lesions in the SRS and WBRT groups was 6 and 5, respectively. The intracranial progression-free survival and overall survival in the SRS group was 5.1 and 5.6 months, respectively, in comparison to 6.1 and 7.2 months, respectively, in the WBRT group. Conclusion: SRS was less effective than WBRT in the treatment of patients with >4 metastases to the brain.

• Progress in Medical Physics
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• v.13 no.4
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• pp.218-223
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• 2002

Stereotactic radiosurgery for intracranial lesion is well established since the Lars Leksell first introduced radiosurgery concept in 1951 Its use in the treatment of spinal lesion has been limited by the availability of effective immobilization devices. The first clinical experience of the spinal stereotactic radiosurgery technique was reported by Hamilton AJ. in 1995. Recently, Optic-guided patient positioning technique for extracranial stereotactic radiosurgery was developed and reported. This study is for assess the target positioning accuracy of the optic guided patient positioning system Exactrac (BrainLab., Inc, Germany). We have designed phantom for assess the accuracy of spinal stereotactic radiosurgery The infrared reflective body markers attached to the relatively immobile part of the body and a series of 2 mm CT images was taken. The image sets were transferred to the planning computer. During the radiosurgery treatment, we measure the real-time display showing the positioning values from Exactrac computer. And we compare the isocenter deviation from irradiated center point of the film which was mounted on the lesion site of the phantom and pin hole site of that film. The accuracy of the ExacTrac system in positioning a target point shows enough for the clinical applications.

• 대한방사선방어학회:학술대회논문집
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• 2010.04a
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• pp.150-151
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• 2010

• Radiation Oncology Journal
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• v.20 no.4
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• pp.391-395
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• 2002

Purpose : To confirm the accuracy of the radiation dose at the isocenter by the standard linear accelerator-based stereotactic radiosurgery technique which was developed at Seoul National University Hospital. Materials and Methods : Radiation dosimetry was undertaken during standard 5-arc radiosurgery using 6 MV X-ray beam from CL2100C linac. The treatment head was attached with circular tertiary collimators of 10 and 20 mm diameter. We measured the absorbed dose at the isocenter of a multi-purpose phantom using two kinds of detector : a 0.125 co ionization chamber and a silicon diode detector. Results : The dose differences at each arc plane between the planned dose and the measured dose at the isocenter raged from $-0.73\%\;to\;-2.69\%$ with the 0.125 cc ion chamber, and from $-1.29\%\;to\;-2.91\%$ with the diode detector during radiosurgery with the tertiary collimator of 20 mm diameter. Those with the 10-mm tertiary collimator ranged from $-2.39\%\;to\;-4.25\%$ with the diode. Conclusion : The dose accuracy at the isocenter was ${\pm}3\%$. Therefore, further efforts such ws modification in processing of the archived image through DICOM3.0 format are required to lessen the dose difference.

• Progress in Medical Physics
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• v.13 no.3
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• pp.135-138
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• 2002

Fractionated stereotactic radiosurguy (FSRS) requires precise and reproducible patient set up. For these reasons non-invasive mask fixation methods have been used in Linac based FSRS. In this study, we measured and assessed the isocenter reproducibility using a commercial head mask fixation system based on thermoplastic materials. For the verification and the measurement of isocenter deviation a special acrylic brain phantom was designed. The designed phantom has 22 vertical rods and each rod has different lengths. At the end of the 8 rods, the monochromic film is attached and irradiated due to planned target position. Deviations of isocenter were measured separately for each direction. The mean deviation showed 0.4 mm in longitudinal direction, 0.1 mm in the lateral direction, 0.1 mm in the anterior-posterior direction of the treatment couch. The data demonstrates the high accuracy and reproducibility. This study reinforces previous literature published.

• Radiation Oncology Journal
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• v.21 no.2
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• pp.107-111
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• 2003

Purpose: To establish the role of stereoactic radiosurgery using a linear accelerator for the treatment of patients with cavernous angloma. Materials and Methods: Between February 1995 and May 1997, 11 patients with cavernous angioma were treated with stereotactic radiosurgery using a linear accelerator. Diagnoses were based on the magnetic resonance imaging in 8 patients, and the histological in 3. The vascular lesions were located on the brainstem (5 cases), cerebellum (2 cases) thalamus (1 case) and cerebrum (3 cases). The clinical presentation at onset included previous intracerebral hemorrhages (9 cases) and seizures (2 cases). All patients were treated with a a linac-based radiosurgery. The median dose of radiation delivered was 16 Gy ranging from 14 to 24 Gy, which was typically proscribed to the 80$\%$ isodose surface (range 50 $\~$ 80$\%$), corresponding to the periphery of the lesion with a single isocenter. Ten patients were followed-up. Results: The median follow-up was 49 months ranging from 8 to 73 months, during which time two patients developed an intracerebral hemorrhage, 1 at 8 months, with the other at 64 months post radiosurgery. One patient developed neurological deficit after radiosurgery, and two developed an edema on the T2 weighted images of the MRI surrounding the radiosurgical target. Conclusion: The use of stereotactic radiosurgery in the treatment of a cavernous angioma may be effective in the prevention of rebleedlng, and can be safely delivered. However, a longer follow-up period will be required.