• Radiation Oncology Journal
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• v.10 no.1
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• pp.95-100
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• 1992

Since LINAC-based stereotactic radiosurgery uses multiple noncoplanar arcs, three-dimensional dose evaluation and many beam parameters, a lengthy computation time is required to optimize even the simplest case by a trial and error. The basic approach presented in this paper is to show promising methods using an experimental optimization and an analytic optimization The purpose of this paper is not to describe the detailed methods, but introduce briefly, proceeding research done currently or in near future. A more detailed description will be shown in ongoing published papers. Experimental optimization is based on two approaches. One is shaping the target volumes through the use of multiple isocenters determined from dose experience and testing. The other method is conformal therapy using a beam's eye view technique and field shaping. The analytic approach is to adapt computer-aided design optimization in finding optimum irradiation parameters automatically.

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

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.189-191
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• 2002

In the proton therapy using a gantry system, periodical verification of iso-center position is very important to assure precision of patient positioning system at any gantry angles in proton treatment. In the gantry system, there are three different types of iso-center; 1) in a geometrical view, 2) in an X-ray beam's eye view, 3) in a proton beam's eye view. Idealistically, they would be an identical point. They could, however, be different points. It may be a source of errors in patient positioning. At PMRC, we have established a system of verification for iso-center positions using a stainless ball of 2-cm in diameter and an imaging plate. This system provides the relation among a center of a patient target position, a center of proton irradiation field, and/or a center of X-ray field in accuracy of 50$\square$m in the 2) and 3) views, as images of a center of the stainless ball and a center of a 100 mm${\times}$100 mm-aperture brass collimator recorded on the imaging plate, which is setup at 1-cm behind the ball. In addition, it provides simultaneously the images of the ball and the collimator on an imaging intensifier (II), which is setup downstream of the proton or X-ray beam. We present a method of quality assurance (QA) for calibration of iso-center position in a rotation gantry system at PMRC and the performance of this system. A proton beam position on the 1$\^$st/ scatterer in the nozzle of the gantry affects less sensitive (reduced by a factor of 1/5) to the results of the iso-center position. The effect is systematically correctable. The effect of the nozzle (or the collimator) position is less than 0.5 mm at the maximum extraction (390 mm).

• Radiation Oncology Journal
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• v.11 no.2
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• pp.431-437
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• 1993

An important problem in radiosurgery is the utilization of the proper beam parameters, to which dose shape is sensitive. Streotactic radiosurgery techniques for a linear accelerator typically, use circular radiation fields with multiple arcs to produce an spherical radiation distribution. Target volumes are irregular in shape for a certain case, and spherical distributions can irradiate normal tissues to high dose as well as the target region. The current improvement to dose distribution utilizes treating multiple isocenters or weighting various arcs to change treatment volume shape. in this paper another promising study relies upon dynamically shaping the treatment beam to fit the beam's eye view of the target. This conformal irradiation technique was evaluated by means of visual three dimensional dose distribution, dose volume histograms to the target volume and surrounding normal brain. It is shown that using even less arcs than multiple isocenter irradiation technique, the conformal therapy yields comparable dose gradients and superior homogeneity of dose within the target volume.

• Progress in Medical Physics
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• v.11 no.1
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• pp.49-57
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• 2000

New method about the dose optimization problem in radiation treatment was researched. Since all conditions are more complex and there are more relevant variables, the solution of three-dimensional treatment planning is much more complicate than that of current two-dimensional one. There(ore, in this study, as a method to solve three-dimensional dose optimization problem, the considered variables was minized and researched by reducing the domain that solutions can exist and pre-determining the important beam parameters. First, the dangerous beam range that passes critical organ was found by coordinate transformation between linear accelerator coordinate and patient coordinate. And the beam size and rotation angle for rectangular collimator that conform tumor at arbitrary beam position was also determined. As a result, the available beam position could be reduced and the dependency on beam size and rotation angle, that is very important parameter in treatment planning, totally removed. Therefore, the resultant combinations of relevant variables could be greatly reduced and the dose optimization by objective function can be done with minimum variables. From the above results, the dose optimization problem was solved for the two-dimensional radiation treatment planning useful in clinic. The objective function was made by combination of dose gradient, critical organ dose and dose homogeniety. And the optimum variables were determined by applying step search method to objective function. From the dose distributions by optimum variables, the merit of new dose optimization method was verified and it can be implemented on commercial radiation treatment planning system with further research.

• Journal of radiological science and technology
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• v.21 no.1
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• pp.24-28
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• 1998

A conventional treatment machine shapes x-ray fields by a set of dense metal collimators(jaws) built into the machine. These collimators are positioned by the therapist using hand controls in the treatment room, and usually remain stationary during treatment. The collimator jaws of treatment machines produce rectangular beams. Conventional beam shaping is accomplished through the use of a combination of these collimator jaws and secondary custom beam blocks attached to the accelerator beyond the collimator Jaws. The jaw positions for a particular field can be retrieved from a computer. One application of this increased capability is replacement of beam blocks for field-shaping with the MLC. There are three basic applications of the MLC. The first application is to replace conventional blocking. A second function of the MLC is related to conformal therapy, adjusting the field shape to match the beam's eye view projection of a planning target volume during treatment. The third application is the use of the MLC to achieve beam intensity modulation. The aim of this paper is to provide basic principle and to state fundamental concepts needed to implement the use of a multileaf collimator in the conventional clinical setting. The use of MLC field shaping is likely to save time and to incur a lower operating cost when compared to the use of beam blocks.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.5
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• pp.297-304
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• 2015

A multilayer gaseous detector has been developed for fast dose-verification measurements of raster-scan-mode therapeutic beams in particle therapy. The detector, which was constructed with eight thin parallel-plate ionization chambers (PPICs) and polymethyl methacrylate (PMMA) absorber plates, is closely tissue-equivalent in a beam's eye view. The gas-electron signals, collected on the strips and pad arrays of each PPIC, were amplified and processed with a continuous charge.integration mode. The detector was tested with 190-MeV raster-scan-mode beams that were provided by the Proton Therapy Facility at Samsung Medical Center, Seoul, South Korea. The detector responses of the PPICs for a 190-MeV raster-scan-mode proton beam agreed well with the dose data, measured using a 2D ionization chamber array (Octavius model, PTW). Furthermore, in this study it was confirmed that the detector simultaneously tracked the doses induced at the PPICs by the fast-oscillating beam, with a scanning speed of 2 m s-1. Thus, it is anticipated that the present detector, composed of thin PPICs and operating in charge.integration mode, will allow medical scientists to perform reliable fast dose-verification measurements for typical dynamic mode therapeutic beams.

• Journal of radiological science and technology
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• v.20 no.2
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• pp.79-82
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• 1997

Image-based three dimensional radiation treatment planning(3D RTP) has a potential of generating superior treatment plans. Advances in computer technology and software developments quickly make 3D RTP a feasible choice for routine clinical use. However, it has become clear that an evaluation of a 3D plan is more difficult than a 2D plan. A number of tools have been developed to facilitate the evaluation of 3D RTP both qualitatively and quantitatively. For example, beam's eye view(BEV) is one of the most powerful and time-saving method as a qualitative tools. Dose-volume histogram(DVH) has been proven to be one of the most valuable methods for a quantitative tools. But it has a limitation to evaluate several different plans for biological effects of the tissue and critical organ. Therefore, there is a strong interest in developing quantitative models which would predict the likely biological response of irradiated organs and tissues, such as tumor control probability(TCP) and normal tissue complication probability(NTCP). DVH and NTCP of hepatoma were evaluated for three dimensional conformal radiotherapy(3D CRT). Also, 3D RTP was analysed as a dose optimization based on beam arrangement and beam modulation.

• Progress in Medical Physics
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• v.3 no.1
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• pp.63-69
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• 1992

Recently, stereotactic radiosurgery plan is required with the information of 3-D image and dose distribution. The purpose of this research is to develop 3-D radiosurgery planning system using personal computer. The procedure of this research is based on three steps. The first step is to input the image information of the patient obtained from CT or MR scan into personal computer through on-line or digitizer. The position and shape of target are also transferred into computer using Angio or CT localization. The second step is to compute dose distribution on image plane, which is transformed into stereotactic frame coordinate. and to optimize dose distribution through the selection of optimal treatment parameters. The third step is to display both isodose distribution and patient image simultaneously using superimpose technique. This prototype of radiosurgery planning system was applied recently for several clinical cases. It was shown that our planning system is fast, accurate and efficient while making it possible to handle various kinds of image modelities such as angio, CT and MRI. It is also possible to develop 3-D planning system in radiation therapy using beam's eye view or CT simulation in future.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.8
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• pp.1-11
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• 1998

One of the desired features for the realizations of high quality Information and Telecommunication services in future is "the Sensation of Reality". This will be achieved only with the visual communication based on the 3- dimensional (3-D) moving images. The main difficulties in realizing 3-D moving image communication are that there is no developed data transmission technology for the hugh amount of data involved in 3-D images and no established technologies for 3-D image recording and displaying in real time. The currently known stereoscopic imaging technologies can only present depth, no moving parallax, so they are not effective in creating the sensation of the reality without taking eye glasses. The more effective 3-D imaging technologies for achieving the sensation of reality are those based on the multiview 3-D images which provides the object image changes as the eyes move to different directions. In this paper, a multiview 3-D imaging system composed of 8 CCD cameras in a case, a RGB(Red, Green, Blue) beam projector, and a holographic screen is introduced. In this system, the 8 view images are recorded by the 8 CCD cameras and the images are transmitted to the beam projector in sequence by a signal converter. This signal converter converts each camera signal into 3 different color signals, i.e., RGB signals, combines each color signal from the 8 cameras into a serial signal train by multiplexing and drives the corresponding color channel of the beam projector to 480Hz frame rate. The beam projector projects images to the holographic screen through a LCD shutter. The LCD shutter consists of 8 LCD strips. The image of each LCD strip, created by the holographic screen, forms as sub-viewing zone. Since the ON period and sequence of the LCD strips are synchronized with those of the camera image sampling adn the beam projector image projection, the multiview 3-D moving images are viewed at the viewing zone.