• Radiation Oncology Journal
• /
• v.10 no.1
• /
• pp.21-26
• /
• 1992

From July 1988 through November 1991,26 patients with inoperable arteriovenous malformations were treated with 6 MV linear accelerator at the Kangnam St. Mary's Hospital, Catholic University Medical College. There were 5 females and 21 males with median age of 29 years (range: $6\~63$ years) and median follow up times of 15 months (range: $4\~40$ months). The arteriovenous malformation volumes treated ranged from 1 cm diameter to 3.5 cm rectangular size. The prescribed doses at the isocenter varied from 15 to 30 Gy and were given as a single fraction. To date, all patients performed follow-up not only clinically but also through CT or angiography based radiologic modalities every 6 month. A complete obliteration was achieved in 6 ($23\%$) and partial obliteration in 8 ($31\%$) and no change in 1 ($4\%$). We observed 14 ($54\%$) responsiveness of arteriovenous malformations after radiosurgery by 2 years afterward. Whereas, the decision of the remaining 11 ($42\%$) patients was considered too early to expect the therapeutic response following radiosurgery. No complications through treatment related were observed, yet. Our initial outcome in these first 26 patients with arteriovenous malformations is recommended further follow-up.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2003.09a
• /
• pp.63-63
• /
• 2003

Purpose: Planning target volume (PTV) for tumors in abdomen or thorax includes enough margin for breathing-related movement of tumor volumes during treatment. We developed a simple and handy method, which can reduce PTV margins in patients with moving tumors, respiratory motion reduction device system (RMRDs). Materials and Methods: The patients clinical database was structured for moving tumor patients and patient setup error measurement and immobilization device effects were investigated. The system is composed of the respiratory motion reduction device utilized in prone position and abdominal presser (strip device) utilized in the supine position, moving phantom and the analysis program, which enables the analysis on patients setup reproducibility. It was tested for analyzing the diaphragm movement and CT volume differences from patients with RMRDs, the magnitude of PTV margin was determined and dose volume histogram (DVH) was computed using a treatment planning software. Dose to normal tissue between patients with RMRDs and without RMRDs was analyzed by comparing the fraction of the normal liver receiving to 50% of the isocenter dose(TD50). Results: In case of utilizing RMRDs, which was personally developed in our hospital, the value was reduced to $5pm1.4 mm$, and in case of which the belt immobilization device was utilized, the value was reduced to 3$pm$0.9 mm. Also in case of which the strip device was utilized, the value was proven to reduce to $4pm.3 mm$0. As a result of analyzing the TD50 is irradiated in DVH according to the radiation treatment planning, the usage of the respiratory motion reduction device can create the reduce of 30% to the maximum. Also by obtaining the digital image, the function of comparison between the standard image, automated external contour subtraction, and etc were utilized to develop patients setup reproducibility analysis program that can evaluate the change in the patients setup. Conclusion: Internal organ motion due to breathing can be reduced using RMRDs, which is simple and easy to use in clinical setting. It can reduce the organ motion-related PTV margin, thereby decrease volume of the irradiated normal tissue.

• Progress in Medical Physics
• /
• v.8 no.1
• /
• pp.17-24
• /
• 1997

We developed PC-based planning system for linear accelerator based stereotactic radiosurgery. The system was developed under Windows 95 on Pentium Pro$\^$(R) 200 ㎒ IBM PC with 128 MB RAM. It was programed using IDL$\^$(R)/ of Research Systems, Inc. as a programing tool. CT image data obtained with BRW stereotactic frame is transferred to PC through magnetoptical disk. As loading the image, the system automatically recognizes the location of rods and establishes stereotactic coordinates. It accurately calculates and corrects the coordinates, degree of tilting, and magnification rate of axial images. After the coordinates is defined we can delineate and edit the contours of target and organs of interest on axial images. Upon delineating contours of target, isocenter is determined automatically and we can set up the beam configuration for radiosurgery. The system provides beam's eye view and room's eye view for efficient confuguring of beams. The system calculates dose distribution 3-dimensionally. It takes 1 to 2 minutes to calculate dose distribution for 5 arcs. We can verify the dose distribution on serial axial images. We can analyze the dose distribution quantitatively by evaluation of dose-volume histogram of target and organ of interest. This system, PC-based radiosurgery planning system, includes the basic features for radiosurgery planning and calculates dose distribution within reasonable time for clinical application.

• Radiation Oncology Journal
• /
• v.10 no.2
• /
• pp.137-145
• /
• 1992

Three-dimensional dose calculations based on CT images are fundamental to stereotactic radiosurgery for small intracranial tumor. In our stereotactic radiosurgery program, irradiations have been performed using the 6 MV photon beam of linear accelerator after stereotactic CT investigations of the target center through the beam's-eye view and the coordinates of BRW frame converted to that of radiosurgery. Also we can describe the tumor diameter and the shape in three dimensional configuration. Non-coplanar irradiation technique was developed that it consists of a combination of a moving field with a gantry angle of $140^{\circ}$, and a horizontal couch angle of $200^{\circ}C$ around the isocenter. In this radiosurgery technique, we provide the patient head setup in the base-ring holder and rotate around body axis. The total gantry moving range shows angle of 2520 degrees via two different types of gantry movement in a plane perpendicular to the axis of patient. The 3-D isodose curves overlapped to the tumor contours in screen and analytic dose profiles in calculation area were provided to calculate the thickness of $80\%$ of tumor center dose to $20\%$ of that. Furtheremore we provided the 3-D dose profiles in entire calculation plane. In this experiments, measured isodose curves in phantom irradiation have shown very similiar to that of computer generations.

• Journal of Korean Neurosurgical Society
• /
• v.30 no.5
• /
• pp.567-574
• /
• 2001

Objective : As for growth hormone(GH) secreting pituitary adenoma, it's remission should be declared on the basis of satisfactory controlling of the tumor, normalization of hormonal level, and symptomatic improvement of the patient. Several modalities of treatment have been applied and administered, and yet, this disease still remains as inveterate one to be fully treated. The purpose of this study is to evaluate the outcome of gamma knife radiosurgery(GKRS) for GH secreting pituitary adenoma, and to identify various factors affecting the outcome of the treatment. Method : A group of 24 out of 35 patients, treated by Leksell gamma knife unit during the period of March of 1992 through October of 1997, had been observed for more than two years. The mean target volume of microadenoma was $449.3mm^3(range 216-880mm^3)$, and that of macroadenoma was $3183.1mm^3(range 1456-13125mm^3)$. The tumor margin was covered with 50% isodose profile, and mean marginal dose was 25.2Gy(range 15-32.4Gy). The mean number of isocenter was 4.3(range 1-6). The exposed dose to the optic apparatus was less than 8Gy. The mean follow-up period was 37.8months(range 24-102months). Result : No patients showed any increase in the tumor volume during the follow-up period. And definite shrinkage of tumor volume(tumor volume reduction rate, TVRR : more than 50%) was obtained in 10 patients(41.7%). Twenty one patients(87.5%) had reduced hormonal level compared than pre-treatment level. Among them, normalization of the hormonal level was achieved in 12 patients(50%). Clinicoendocrinological remission was seen in 3 patients (12.5%). According to the results of statistical analysis, tumor volume(p=0.016),duration of symptoms(p=0.046), initial GH level(p=0.017), and the invasion of cavernous sinus(p=0.036) were significantly favorable to post-radiosurgical outcome. The TVRR was significantly related to post-radiosurgical reduction of serum GH level. Permanent complication was not seen. Conclusion : The authors concluded that GKRS is a safe and effective treatment modality for acromegaly. To otain the better outcome of GKRS in GH secreting pituitary adenoma, more careful and sophisticated treatment-planning is recommended.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2004.11a
• /
• pp.126-129
• /
• 2004

We compared intensity-modulated radiotherapy (IMRT) treatment plans with commercially available multileaf collimators (MLCs) of different leaf width for intracranial lesions. Twelve cases previously treated with micro-MLCs(mMLCs) were replanned using the Varian 120 and 80 MLCs. These collimators have minimum leaf width of 3mm, 5 mm and 10 mm at isocenter, respectively. These three plans were compared with respect to the uniformity and the conformity indices, doses to normal tissue. For the uniformity index of planning target volume (PTV),there was no statistically significant difference between mMLCs with 120 MLCs (p = 0.06). However, there was a little difference between mMLCs with 80 MLCs (p = 0.001). Maximum target dose to the PTV showedno dependency with respect to the leaf width. On the contrary, there were statistically significant differences in the conformity indices between mMLCs and 120 MLCs (p = 0.003) and between mMLCs and 80 MLCs (p = 0.003).The volumetric increments for MLCs with leaf widths of 5 mm and 10 mm were 6.3% and 23.2% for the normal tissue Irradiated to = 50% dose, and 8.7% and 32.7% for the normal tissue Irradiated to = 70% dose, respectively, compared to the volume for MLCs with leaf width of 3 mm. This shows that for the sparing of normal tissue, MLCs with leaf width of 3 mm are more effective, compared to MLCs with leaf widths of 5 mm and 10 mm.

• Progress in Medical Physics
• /
• v.21 no.1
• /
• pp.99-112
• /
• 2010

In Republic of Korea, there are many Quality Assurance protocol for general radiation treatment machine such as linac. However, Quality Assurance protocol for radiosurgery treatment system is not ready perfectly. One of the radiation treatment machine for radiosurgery, novalis system needs to suitable Quality Assurance protocol for using it right way during radiation treatment and maintaining suitable accuracy for daily, weekly, monthly and annually periods. Therefore, in this article, we develop Quality Assurance protocol for novalis system. We collected and analysed domestic and foreign novalis Quality Assurance protocol. After that, we selected essential QA items and each tolerance range for developing proper QA protocol, and we made anatomical phantom for execution of selected QA items and evaluation of overall state of QA, and then, we use this measured value as a reference. Quality Assurance items are consisted of Mechanical accuracy QA part and Radiation delivery QA part. Mechanical accuracy QA part is comprised of radiation generation machine part, assistive devices part and multi-leaf collimator part. Radiation delivery QA part is divided into radiation isocenter accuracy and dosimetric evaluation. After that, developed novalis QA tables are made by using these QA items. These novalis QA tables would be used to good standard in order to maintain apt accuracy for radiosurgery in daily, weekly, monthly and annually periods.

• Journal of Korean Neurosurgical Society
• /
• v.29 no.9
• /
• pp.1228-1232
• /
• 2000

Objective : This study was undertaken to analysis gamma knife radiosurgery(GKR) effect for trigeminal neuralgia after long term follow-up. Methods : There were 11 trigeminal neuralgia patients. The authors irradiated 67-85 Gy maximally to the nerve root entry zone(NREZ) using single 4mm collimator, just 1-6mm lateral side from the junction of the trigeminal nerve and pons. For the first 3 cases, we targeted the junction between the nerve and the pons. In theses cases, the pons was irradiated 56 or 60 gray in the surface. In the later 8 cases, the isocenter is positioned more distal side so that the brain stem surface would receive less than the 20% isodose. Results : The average follow-up duration was 25 months(13-50 months). Pain relief was noticed within a week to 5 months. In 3 patients, pain was relieved completely and in other 3 patients, mark improvement was achieved(80-90%). Remaining 4 patients showed significant improvement(30-50%). There was recurrence in only one case and she complained with similar intensity of pain at the last follow-up. There was no significant complication related to GKR. Conclusion : GKR is considered effective for trigeminal neuralgia based on the long term follow-up evaluation, but more clinical experience is needed to evaluate the efficacy of GKR for trigeminal neuralgia as a primary treatment modality.

• Progress in Medical Physics
• /
• v.22 no.2
• /
• pp.67-71
• /
• 2011

We evaluated the overall setup accuracy for the On-Board Imager (OBI, Varian Medical Systems Inc., Palo Alto, CA, USA), with attention to the laser, the gantry, and operator performance. We let experienced technicians place the marker block on the couch using a lock bar system, with alignment to the isocenter of the laser, every morning. A pair of radiographic images of the marker block was acquired at $0^{\circ}$ and $270^{\circ}$ angles to the kV arm to correct the position using a 2D/2D matching technique. Once the desired match was achieved, the couch was moved remotely to correct the setup error and the parameters were saved. The average for the vertical and the longitudinal displacements were 0.65 mm and 0.66 mm, and 0.01 mm for the lateral displacement. The average for the vertical and longitudinal displacements were statistically significant at the 0.05 level (p value=0.000 for both), while the p value for the lateral direction was 0.829. These results show that the tendencies to displacement in vertical and longitudinal directions occur through systematic error, while systematic error was not found in the lateral displacement. This daily overall evaluation is practical and easy to find the systematic and random errors in the setup system; however, a daily QA for laser and OBI alignment is still needed to minimize the systematic error in aligning patients.

• Progress in Medical Physics
• /
• v.20 no.1
• /
• pp.43-50
• /
• 2009

The 4 bank mico-MLC (mMLC; Acculeaf, Direx, Isral) has been commissioned for clinical use of linac based stereotactic radiosurgery. The geometrical parameters to control the leaves were determined and comparisons between measured and calculated by the calculation model were performed in terms of absolute dose (cGy/100 MU). As a result of evaluating calculated dose for various field sizes and depths of 5 and 10 cm in water in the geometric condition of fixed SSD (source to surface distance) and fixed SCD (source to chamber distance), most of differences were within 1% for 6 MV and 15 MV x-rays. The penumbral widths at the isocenter were approximately evaluated to 0.29~0.43 cm depending on the field size for 6 MV and 0.36~0.51 cm for 15 MV x-rays. The average transmission and leakage for 6 MV and 15 MV x-rays were 6.6% and 7.4% respectively in single level of leaves fully closed. In case of dual level of leaves fully closed the measured transmission is approximately 0.5% for both 6 MV and 15 MV x-rays. Through the commissiong procedure we could verify the dose characteristics of mMLC and approximately evaluate the error ranges for treatment planning system.