• Progress in Medical Physics
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• v.2 no.2
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• pp.109-120
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• 1991

Total body irradiation is operated to irradicate malignant cells of bone marrow of patients to be treated with bone marrow transplantation. Field size of a linear accelerator or cobalt teletherapy unit with normal geometry for routine technique is too small to cover whole body of a patient. So, any special method to cover patient whole body must be developed. Because such environments as room conditions and machine design are not universal, some characteristic method of TBI for each hospital could be developed. At Seoul National University Hospital, at present, only a cobalt unit is available for TBI because source head of the unit could be tilted. When the head is tilted outward by 90$^{\circ}$, beam direction is horizontal and perpendicular to opposite wall. Then, the distance from cobalt source to the wall was 319 cm. Provided that the distance from the wall to midsagittal plane of a patient is 40cm, nominal field size at the plane(SCD 279cm) is 122cm$\times$122cm but field size by measurement of exposure profile was 130cm$\times$129cm and vertical profile was not symmetric. That field size is large enough to cover total body of a patient when he rests on a couch in a squatting posture. Assuming that average lateral width of patients is 30cm, percent depth dose for SSD 264cm and nominal field size 115.5cm$\times$115.5cm was measured with a plane-parallel chamber in a polystyrene phantom and was linear over depth range 10～20cm. An anthropomorphic phantom of size 25cm wide and 30cm deep. Depth of dose maximum, surface dose and depth of 50% dose were 0.3cm, 82% and 16.9cm, respectively. A dose profile on beam axis for two opposing beams was uniform within 10% for mid-depth dose. Tissue phantom ratio with reference depth 15cm for maximum field size at SCD 279cm was measured in a small polystyrene phantom and was linear over depth range 10～20cm. An anthropomorphic phantom with TLD chips inserted in holes on the largest coronal plane was bilaterally irradiated by 15 minute in each direction by cobalt beam aixs in line with the cross line of the coronal plane and contact surface of sections No. 27 and 28. When doses were normalized with dose at mid-depth on beam axis, doses in head/neck, abdomen and lower lung region were close to reference dose within $\pm$ 10% but doses in upper lung, shoulder and pelvis region were lower than 10% from reference dose. Particulaly, doses in shoulder region were lower than 30%. On this result, the conclusion such that under a geometric condition for TBI with cobalt beam as SNUH radiotherapy departement, compensators for head/neck and lung shielding are not required but boost irradiation to shoulder is required could be induced.

• Radiation Oncology Journal
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• v.12 no.2
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• pp.225-232
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• 1994

Purpose : This study was to obtain the basic dosimetric data using the 10 MV X-ray for the total body irradiation. Materials and Methods : A linear accelerator photon beam is planned to be used as a radiation source for total body irradiation (TBI) in Chonnam University Hospital. The planned distance from the target to the midplane of a patient is 360cm and the maximum geometric field size is 144cm x 144cm. Polystyrene phantom sized $30{\times}30{\times}30.2cm^3$ and consisted of several sheets with various thickness, and a parallel plate ionization chamber were used to measure surface dose and percent depth dose (PDD) at 345cm SSD, and dose profiles. To evaluate whether a beam modifier is necessary for TBI, dosimetry in build up region was made first with no modifier and next with an 1cm thick acryl plate 20cm far from the polystyrene phantom surface. For a fixed sourec-chamber distance, output factors were measured for various depth. Results : As any beam modifier was not on the way of radiation of 10MV X-ray, the $d_{max}$ and surface dose was 1.8cm and $61\%$, respectively, for 345cm SSD. When an 1cm thick acryl plate was put 20cm far from polystyrene phantom for the SSD, the $d_{max}$ and surface dose were 0.8cm and $94\%$, respectively. With acryl as a beam spoiler, the PDD at 10cm depth was $78.4\%$ and exit dose was a little higher than expected dose at interface of exit surface. For two-opposing fields for a 30cm phantom thick phantom, the surface dose and maximum dose relative to mid-depth dose in our experiments were $102.5\%$ and $106.3\%$, respectively. The off-axis distance of that point of $95\%$ of beam axis dose were 70cm on principal axis and 80cm on diagonal axis. Conclusion: 1. To increase surface dose for TBI by 10MV X-ray at 360cm SAD, 1cm thick acrylic spoiler was sufficient when distance from phantom surface to spoiler was 20cm. 2. At 345cm SSD, 10MV X-ray beam of full field produced a satisfiable dose uniformity for TBI within $7\%$ in the phantom of 30cm thickness by two-opposing irradiation technique. 3. The uniform dose distribution region was 67cm on principal axis of the beam and 80cm on diagonal axis from beam axis. 4. The output factors at mid-point of various thickness revealed linear relation with depth, and it could be applicable to practical TBI.

• The Korean Journal of Physiology
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• v.22 no.2
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• pp.189-206
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• 1988

The effects of ouabain on the contractile and electrical activities were investigated in the isolated preparations of guinea-pig taenia coli, and compared with those of vanadate. Spontaneous contractions were recorded with force transducer, and electrical activites were measured by use of suction electrode, or single sucrose-gap technique. The contractions were induced by the electrical stimulation for 5 seconds every 1 minute with alternating current (60 Hz, 3.0 V/cm) through the platinum electrodes located in parallel with the long axis of the preparation. All experiments were performed in tris-buffered Tyrode solution which was aerated with $100%{\;}O_2$ and kept at $35^{\circ}C$. The results obtained were as follows: 1) Responses of spontaneous contractions to ouabain were concentration-dependent; $10^{-7}M$ ouabain caused a rise of basal tone. Above the concentration of $10^{-6}M$ ouabain, an initial increase followed by a decrease in tension was observed. 2) A continuous spike discharge was induced by the administration of $10^{-7}M$ ouabain. Above $10^{-6}M$ ouabain, a transient initial increase followed by a decrease in spike frequency and amplitude was produced, and finally membrane potential was sustained at a certain level without a spike discharge. 3) The characteristic response to $10^{-7}M$ ouabain was not blocked by the pretreatment with $10^{-7}M$ atropine. 4) The electrically induced contractions were completely suppressed at the concentration of $2{\times}10^{-7}M$ ouabain. These contractions were blocked more rapidly in paralled with the increase in ouabain concentration. 5) Effects of vanadate on the spontaneous activities were quite different from those of ouabain; $10^{-6}M$ vanadate increased the amplitude of contractions and $10^{-5}M$ vanadate increased slightly both amplitude and frequency of spontaneous contractions. $10^{-4}M$ vanadate showed irregular phasic contractions superimposed on the increased basal tone. 6) $10^{-5}M$ vanadate depolarized the membrane potential and shortened the interval between the bursts of spike discharge, whereas $10^{-4}M$ vanadate induced continuous spike discharge with membrane depolarization. 7) Vanadate caused a characteristic inhibitory response to the contractions induced by electrical stimulation; An initial rapid inhibition of tension development and then gradual recovery to a certain level. From the above results, the following conclusions could be made: 1) The rise of basal tone at $10^{-7}M$ ouabain is due to continuous spike discharge without a silent period. The continuous spike discharge is likely to be associated with a slight membrane depolarization caused by the blockage of Na pump. 2) The biphasic response induced by above $10^{-6}M$ ouabain seems to occur by the different mechanisms. The initial increase in tension is associated with depolarization along with an increase in spike frquency, whereas the subsequent relaxation occurs through a non-electrical mechanism. 3) The characteristic response to $10^{-7}M$ ouabain is resulted not from the action on intrinsic nerve terminal, but from its direct action on the membrane of smooth muscle cells. 4) The phasic contractions superimposed on the increased basal tone at the concentration of $10^{-4}M$ vanadate is resulted from the continuous spike discharge with membrane depolarization, of which mechanism remains unknown. 5) The inhibitory action of ouabain on the electrically induced contractions suggests that the increasein intracellular Na in some way inhibits the electrically induced $Ca^{2+}$ influx. The mechanism of vanadate action on the induced contractions remains unknown.

• Progress in Medical Physics
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• v.24 no.3
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• pp.154-161
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• 2013

This study assessed compared photon and proton treatment techniques, such as intensity modulated radiation therapy (IMRT), uniform scanning proton therapy (USPT), and intensity modulated proton therapy (IMPT), for a total of 10 prostate cancers. All treatment plans delivered 70 Gy to 95% of the planned target volume in 28 fractions. IMRT plans had 7 fields for the step and shoot technique, while USPT and IMPT plans employed two equally weighted, parallel-opposed lateral fields to deliver the prescribed dose to the planned target. Inverse planning was then incorporated to optimize IMPT. The homogeneity index (HI) and conformity index (CI) for the target and the normal tissue complication probability (NTCP) for organ at risk (OAR) were calculated. Although the mean HI and CI for target were not significantly different for each treatment techniques, the NTCP of the rectum was 2.233, 3.326, and 1.707 for IMRT, USPT, and IMPT, respectively. The NTCP of the bladder was 0.008, 0.003, and 0.002 respectively. The NTCP values at the rectum and bladder were significantly lower using IMPT. Our study shows that using proton therapy, particularly IMPT, to treat prostate cancer could be beneficial compared to 7-field IMRT with similar target coverage. Given these results, radiotherapy using protons, particularly optimized IMPT, is a worthwhile treatment option for prostate cancer.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.975-976
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• 1993

This talk presents the overview of the author's research and development activities on fuzzy inference hardware. We involved it with two distinct approaches. The first approach is to use application specific integrated circuits (ASIC) technology. The fuzzy inference method is directly implemented in silicon. The second approach, which is in its preliminary stage, is to use more conventional microprocessor architecture. Here, we use a quantitative technique used by designer of reduced instruction set computer (RISC) to modify an architecture of a microprocessor. In the ASIC approach, we implemented the most widely used fuzzy inference mechanism directly on silicon. The mechanism is beaded on a max-min compositional rule of inference, and Mandami's method of fuzzy implication. The two VLSI fuzzy inference chips are designed, fabricated, and fully tested. Both used a full-custom CMOS technology. The second and more claborate chip was designed at the University of North Carolina(U C) in cooperation with MCNC. Both VLSI chips had muliple datapaths for rule digital fuzzy inference chips had multiple datapaths for rule evaluation, and they executed multiple fuzzy if-then rules in parallel. The AT & T chip is the first digital fuzzy inference chip in the world. It ran with a 20 MHz clock cycle and achieved an approximately 80.000 Fuzzy Logical inferences Per Second (FLIPS). It stored and executed 16 fuzzy if-then rules. Since it was designed as a proof of concept prototype chip, it had minimal amount of peripheral logic for system integration. UNC/MCNC chip consists of 688,131 transistors of which 476,160 are used for RAM memory. It ran with a 10 MHz clock cycle. The chip has a 3-staged pipeline and initiates a computation of new inference every 64 cycle. This chip achieved an approximately 160,000 FLIPS. The new architecture have the following important improvements from the AT & T chip: Programmable rule set memory (RAM). On-chip fuzzification operation by a table lookup method. On-chip defuzzification operation by a centroid method. Reconfigurable architecture for processing two rule formats. RAM/datapath redundancy for higher yield It can store and execute 51 if-then rule of the following format: IF A and B and C and D Then Do E, and Then Do F. With this format, the chip takes four inputs and produces two outputs. By software reconfiguration, it can store and execute 102 if-then rules of the following simpler format using the same datapath: IF A and B Then Do E. With this format the chip takes two inputs and produces one outputs. We have built two VME-bus board systems based on this chip for Oak Ridge National Laboratory (ORNL). The board is now installed in a robot at ORNL. Researchers uses this board for experiment in autonomous robot navigation. The Fuzzy Logic system board places the Fuzzy chip into a VMEbus environment. High level C language functions hide the operational details of the board from the applications programme . The programmer treats rule memories and fuzzification function memories as local structures passed as parameters to the C functions. ASIC fuzzy inference hardware is extremely fast, but they are limited in generality. Many aspects of the design are limited or fixed. We have proposed to designing a are limited or fixed. We have proposed to designing a fuzzy information processor as an application specific processor using a quantitative approach. The quantitative approach was developed by RISC designers. In effect, we are interested in evaluating the effectiveness of a specialized RISC processor for fuzzy information processing. As the first step, we measured the possible speed-up of a fuzzy inference program based on if-then rules by an introduction of specialized instructions, i.e., min and max instructions. The minimum and maximum operations are heavily used in fuzzy logic applications as fuzzy intersection and union. We performed measurements using a MIPS R3000 as a base micropro essor. The initial result is encouraging. We can achieve as high as a 2.5 increase in inference speed if the R3000 had min and max instructions. Also, they are useful for speeding up other fuzzy operations such as bounded product and bounded sum. The embedded processor's main task is to control some device or process. It usually runs a single or a embedded processer to create an embedded processor for fuzzy control is very effective. Table I shows the measured speed of the inference by a MIPS R3000 microprocessor, a fictitious MIPS R3000 microprocessor with min and max instructions, and a UNC/MCNC ASIC fuzzy inference chip. The software that used on microprocessors is a simulator of the ASIC chip. The first row is the computation time in seconds of 6000 inferences using 51 rules where each fuzzy set is represented by an array of 64 elements. The second row is the time required to perform a single inference. The last row is the fuzzy logical inferences per second (FLIPS) measured for ach device. There is a large gap in run time between the ASIC and software approaches even if we resort to a specialized fuzzy microprocessor. As for design time and cost, these two approaches represent two extremes. An ASIC approach is extremely expensive. It is, therefore, an important research topic to design a specialized computing architecture for fuzzy applications that falls between these two extremes both in run time and design time/cost. TABLEI INFERENCE TIME BY 51 RULES {{{{Time }}{{MIPS R3000 }}{{ASIC }}{{Regular }}{{With min/mix }}{{6000 inference 1 inference FLIPS }}{{125s 20.8ms 48 }}{{49s 8.2ms 122 }}{{0.0038s 6.4㎲ 156,250 }} }}

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.69-76
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• 2017

Purpose: The purpose of this study was to verify dosimetric results and reproducibility of position during craniospinal irradiation (CSI) using tomotherapy (Accuray Incorporated, USA). Also, by comparing with conventional CSI Technique, we confirmed the efficiency of using a Tomotherapy. Materials and Methods: 10 CSI patients who get tomotherapy participate. Patient-specific quality assurances (QA) for each patient are conducted before treatment. When treating, we took Megavoltage Computed Tomography (MVCT) that range of head and neck before treatment, L spine area after treatment. Also we conducted in-vivo dosimetry to check a scalp dose. Finally, we made a 3D conventional radiation therapy(3D-CRT) of those patients to compare dosimetric differences with tomotherapy treatment planning. Results: V107, V95 of brain is 0 %, 97.2 % in tomotherapy, and 0.3 %, 95.1 % in 3D-CRT. In spine, value of V107, V95 is 0.2 %, 18.6 % in tomotherapy and 89.6 %, 69.9 % in 3D-CRT. Except kidney and lung, tomotherapy reduced normal organ doses than 3D-CRT. The maximum positioning error value of X, Y, Z was 10.2 mm, -8.9 mm, -11.9 mm. Through in-vivo dosimetry, the average of scalp dose was 67.8 % of prescription dose. All patient-specific QA were passed by tolerance value. Conclusion: CSI using tomotherapy had a risk of parallel organ such as lung and kidney because of integral dose in low dose area. However, it demonstrated dosimetric superiority at a target and saved normal organ to reduce high dose. Also results of reproducibility were not exceeded margins that estimated treatment planning and invivo dosimetry showed to reduce scalp dose. Therefore, CSI using tomotherapy is considered to efficient method to make up for 3D-CRT.

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.324-332
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• 2009

The purpose of this study was to investigate the effect of rigidity of post core systems on stress distribution by the theoretical technique, finite element stress-analysis method. Three-dimensional finite element models simulating an endodontically treated maxillary central incisor restored with a zirconia ceramic crown were prepared and 1.5 mm ferrule height was provided. Each model contained cortical bone, trabecular bone, periodontal ligament, 4 mm apical root canal filling, and post-and-core. Six combinations of three parallel type post (zirconia ceramic, glass fiber, and stainless steel) and two core (Paracore and Tetric ceram) materials were evaluated, respectively. A 50 N static occlusal load was applied to the palatal surface of the crown with a $60^{\circ}$angle to the long axis of the tooth. The differences in stress transfer characteristics of the models were analyzed. von Mises stresses were chosen for presentation of results and maximum displacement and hydrostatic pressure were also calculated. An increase of the elastic modulus of the post material increased the stress, but shifted the maximum stress location from the dentin surface to the post material. Buccal side of cervical region (junction of core and crown) of the glass fiber post restored tooth was subjected to the highest stress concentration. Maximum von Mises stress in the remaining radicular tooth structure for low elastic modulus resin core (29.21 MPa) was slightly higher than that for high elastic modulus resin core (29.14 MPa) in case of glass fiber post. Maximum displacement of glass fiber post restored tooth was higher than that of zirconia ceramic or stainless steel post restored tooth.

• Journal of the Korean Geotechnical Society
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• v.22 no.6
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• pp.71-82
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• 2006

One of the most popular pre-reinforcement methods of tunnel heading in cohesionless soils would be the fore-polling of grouted pipes, known as RPUM (reinforced protective umbrella method) or UAM (umbrella arch method). This technique allows safe excavation even in poor ground conditions by creating longitudinal arch parallel to the tunnel axis as the tunnel advances. Some previous studies on the reinforcing effects have been performed using numerical methods and/or laboratory-based small scale model tests. The complexity of boundary conditions imposes difficulties in representing the tunnelling procedure in laboratory tests and theoretical approaches. Full-scale study to identify reinforcing effects of the tunnel heading has rarely been carried out so far. In this study, a large scale model testing for a tunnel in granular soils was performed. Reinforcing patterns considered are four cases, Non-Reinforced, Crown-Reinforced, Crown & Face-Reinforced, and Face-Reinforced. The behavior of ground and pipes as reinforcing member were fully measured as the surcharge pressure applied. The influences of reinforcing pattern, pipe length, and face reinforcement were investigated in terms of stress and displacement. It is revealed that only the Face-Reinforced has decreased sufficiently both vertical settlement in tunnel heading and horizontal displacement on the face. Vertical stresses along the tunnel axis were concentrated in tunnel heading from the test results, so the heading should be reinforced before tunnel advancing. Most of maximum axial forces and bending moments for Crown-reinforced were measured at 0.75D from the face. Also it should be recommended that the minimum length of the pipe is more than l.0D for crown reinforcement.

• Radiation Oncology Journal
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• v.23 no.1
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• pp.22-31
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• 2005

Purpose : To conduct a nationwide survey on the principals in radiotherapy for rectal cancer, and produce a database of Korean Patterns of Care Study. Materials and Methods : We developed web-based Patterns of Care Study system and a national survey was conducted using random sampling based on power allocation methods. Eligible patients were who had postoperative radiotherapy for rectal cancer without gross residual tumor after surgical resection and without previous history of other cancer and radiotherapy to pelvis. Data of patients were Inputted to the web based PCS system by each investigators in 19 institutions. Results : Informations on 309 patients with rectal cancer who received radiotherapy between 1998 and 1999 were collected. Male to female ratio was 59 : 41, and the most common location of tumor was lower rectum ($46\%$). Preoperative CEA was checked in $79\%$ of cases and its value was higher than 6 ng/ml in $32\%$. Pathologic stage were I in $1.5\%$, II in $32\%$, III in $53\%$, and IV in $1.6\%$. Low anterior resection was the most common type of surgery and complete resection was peformed in $95\%$ of cases. Distal resection margin was less than 2 cm in $30\%$, and number of lymph node dissected was less than 12 in $31\%$. Chemotherapy was peformed in $91\%$ and most common regimen was 5-FU and leucovorine ($59\%$). The most common type of field arrangement used for the initial pelvic field was the four field box (Posterior-Right-Left) technique ($65.0\%$), and there was no AP-PA parallel opposing field used. Patient position was prone in $81.2\%$, and the boost field was used in $61.8\%$. To displace bowel outward, pressure modulating devices or bladder filling was used in $40.1\%$. Radiation dose was prescribed to isocenter in $45.3\%$ and to isodose line in 123 cases ($39.8\%$). Percent delivered dose over $90\%$ was achieved in $92.9\%$. Conclusion : We could find the Patterns of Care for the radiotherapy in Korean rectal cancer patients was similar to that of US national survey. The type of surgery and the regimen of chemotherapy were variable according to institutions and the variations of radiation dose and field arrangement were within acceptable range.