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Digital Tomosynthesis for Patient Alignment System Using Half-fan Mode CBCT Projection Images.

Justin C PARK ; Sung Ho PARK ; Jin Sung KIM ; Yongyih HAN ; Sang Gyu JU ; Eunhyuk SHIN ; Jung Suk SHIN ; Hee Chul PARK ; Yong Chan AHN ; Willian Y SONG

Korean Journal of Medical Physics.2010;21(4):360-366.

To generate on-board digital tomosynthesis (DTS) for three-dimensionalimage-guided radiation therapy (IGRT) as an alternative to conventional portal imaging or on-board cone-beam computed tomography (CBCT), two clinical cases (liver and bladder) were selected to illustrate the capabilities of on-board DTS for IGRT. DTS images were generated from subsets of CBCT projection data (45, 162 projections) using half-fan mode scanning with a Feldkamp-type reconstruction algorithm. Digital tomosynthesis slices appeared similar to coincident CBCT planes and yielded substantially more anatomic information. Improved bony and soft-tissue visibility in DTS images is likely to improve target localization compared with radiographic verification techniques and might allow for daily localization of a soft-tissue target. Digital tomosynthesis might allow targeting of the treatment volume on the basis of daily localization.
Cone-Beam Computed Tomography ; Humans ; Patient Positioning

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The Dosimetric Effect on Real PTV and OARs at Various Image Fusion Protocol for Pituitary Adenomas.

Kyung Nam LEE ; Dong Joon LEE ; Tae Suk SUH

Korean Journal of Medical Physics.2010;21(4):354-359.

The purpose of this study is to verify the dosimetric effect on real PTV (planning target volume) coverage and safety of OARs (organs at risk) at various image fusion protocol-based radiosurgery plan for pituitary adenomas. Real PTV coverage and its variation was acquired and maximum dose and the volume absorbing above threshold dose were also measured for verifying the safety of optic pathway and brainstem. The protocol that can reduce superior-inferior uncertainty by using both axial and coronal MR (magnetic resonance) image sets shows relatively lower values than that of case using only axial image sets. As a result, the image fusion protocol with both axial and coronal image sets can be beneficial to generate OAR-weighted radiosurgery plan.
Brain Stem ; Pituitary Neoplasms ; Radiosurgery ; Uncertainty

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A Study of Drug Content and Cell Cytotoxicity of Paclitaxel-eluting Stents Coated with Various Biopolymer.

Dong Gon KIM ; Il Gyun SHIN ; Gi Han KIM ; Seong Hyeon KIM ; Ju Ho LEE ; Byoyng Yun KI ; Jae Woon NAH ; Tae Suk SUH ; Sang Ho KIM

Korean Journal of Medical Physics.2009;20(3):125-131.

In this study, the paclitaxel eluting stent (PES) was prepared by coating a biliary stent with paclitaxel using various biopolymer such as poly (vinyl acetate) (PVAc), poly (lactic-co-glycolic acid) (PLGA), Silicone rubber for restenosis prevention in gastrointestinal disease by a dip-coating method. Drug contents of PES were increased as surface area of stent, concentration and molecular weight of coating polymer increase. In 1H-NMR specta, we know that drug did not change by confirming specific peaks of paclitaxel in PES. As shown in SEM image, PES prepared using various biopolymer is coated clearly and regularly except Silicone rubber coating polymer. In in vitro cell cytotoxicity test, bare stent showed low cytotoxic effect against CT-26 colon carcinoma cell line on 3 day. However, PES coated with PLGA 502H showed the highest cytotoxicity because PLGA 502H is biodegradable polymer and has less molecular weight than other coating polymer. These results suggest that PES coated various biopolymer can be prevented restenosis in gastrointestinal disease.
Biopolymers ; Cell Line ; Colon ; Gastrointestinal Diseases ; Lactic Acid ; Molecular Weight ; Paclitaxel ; Polyglycolic Acid ; Polymers ; Silicone Elastomers ; Stents

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A Study on Fatigue Characteristic of Stent Using Finite Element Analysis.

Han Ki KIM ; Il Gyun SHIN ; Dong Gon KIM ; Seong Hyeon KIM ; Ju Ho LEE ; Byoyng Yun KI ; Tae Suk SUH ; Sang Ho KIM

Korean Journal of Medical Physics.2009;20(3):119-124.

Stents are frequently used throughout the human body. They keep pathways open in vascular or nonvascular duct for a long time. Therefore its stability is very important factor. In recent years, aconsiderable amount of research has been carried out in order to estimate mechanical properties of the stent such as expansion pressure behavior, radial recoil and longitudinal recoil using FEM (Finite element analyses). However, published works on simulation of stent fatigue behavior using FEM are relatively rare. In this paper, a nonlinear finite-element method was employed to analyses the compression of a stent using external pressure and fatigue behavior. Finite element analyses for the stent system were performed using NASTRAN FX. In conclusion this paper shows how the stent is behaved in the body, and its fatigue behavior.
Fatigue ; Finite Element Analysis ; Human Body ; Stents

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Evaluation of the Output Dose of a Linear Accelerator Photon Beams by Using the Ionization Chamber TM31010 Series through TG-51 Protocol to Postal Monitoring Output of RPC for 5 Years.

Tae Jin CHOI ; Ok Bae KIM

Korean Journal of Medical Physics.2011;22(2):92-98.

This study is to keep the accuracy and stability of the output dose evaluations for linear accelerator photon beams by using the air ionization chambers (TM31010, 0.125 cc, PTW) through the Task Group 51 protocol. The absorbed dose to water calibration factor NdwCo-60 was delivered from the air kerma calibration factor Nk which was provided from manufacture through SSDL calibration for determination of output factor. The ionization chamber of TM31010 series was reviewed the calibration factor and other parameters for reduce the uncertainty within +/-2% discrepancy and we found the supplied NdwCo-60 which was derived from Nk has shown a -2.8% uncertainty compare to that of PSDL. The authors provided the program to perform the output dosimetry with TG-51 protocol as it is composed same screen of TG-51 worksheets. The evaluated dose by determination of output factor delivered to postal TLD block for comparison the output dose to that of MDACC (RPC) in postal monitoring program. The results have shown the 1.001+/-0.013 for 6 MV and 0.997+/-0.012 discrepancy for 15 MV X rays for 5 years followed. This study shows the evaluated outputs for linear accelerate photon beams are very close to that of international output monitor with small discrepancy of +/-1.3% with high reliability and showing the gradually stability after 2010.
Air Ionization ; Calibration ; Organothiophosphorus Compounds ; Particle Accelerators ; Phenylpropionates ; Uncertainty ; Water

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Calculation of Energy Spectra for Electron Beam of Medical Linear Accelerator Using GEANT4.

Young Gull JOH ; Hyung Dong KIM ; Byung Young KIM ; Sung Jin KIM ; Se An OH ; Jeong Ku KANG ; Sung Kyu KIM

Korean Journal of Medical Physics.2011;22(2):85-91.

The energy spectra for electron beam of medical linear accelerator were calculated using a GEANT4 Medical Linac 2 example code. The incident electron mean energy were 6, 9, 12, 16, 20 MeV. This code was designed to calculate electron beam energy spectra according to material, thickness and location of electron scattering foil affecting electron beam characteristic. Lead, Copper, Aluminum and Gold were used for scattering foil. The energy distribution for electron and photon were analyzed by changing position of scattering foil in the head of linear accelerator. The effect of electron scattering foil on energy spectra which is basic data of simulation for medical linear accelerator were presented. The calculated results would be used in design of medical accelerator head.
Aluminum ; Copper ; Electrons ; Head ; Particle Accelerators

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Study on the 6 MV Photon Beam Characteristics and Analysis Method from Medical Linear Accelerators Using Geant4 Medical Linac2 Example.

Byung Yong KIM ; Hyung Dong KIM ; Sung Jin KIM ; Se An OH ; Jung Gu KANG ; Sung Kyu KIM

Korean Journal of Medical Physics.2011;22(2):79-84.

In this study, Geant4 based Monte Carlo simulations were carried out for medical linear accelerator. Modified Medical Linac2 toolkit was used for calculation. The energy spectrum, most probable energy and the photon mean energy compared with the published results using the EGS4 code. The results well agreed with published results. The calculated results of photon fluence, energy fluence and mean energy according to the radius from the centre of the beam were analyzed. Monte Carlo simulation using Medical Linac2 code is considered to be useful for analysis of medical linear accelerator. Because the calculated results varies depending on Physics List model for same head structure. It it important to choose the right model for research purpose. Monte Carlo simulation using GEANT4 Medical Linac2 is a valuable for any novice to adopt this code to the study related to 6 MV photon fluence from medical linear accelerator.
Head ; Particle Accelerators ; Radius

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Evaluation of Setup Errors for Tomotherapy Using Differently Applied Vacuum Compression with the Bodyfix Immobilization System.

Jae Hong JUNG ; Kwang Hwan CHO ; Jeong Woo LEE ; Min Joo KIM ; Kwang Chae LIM ; Seong Kwon MOON ; Yong Ho KIM ; Tae Suk SUH

Korean Journal of Medical Physics.2011;22(2):72-78.

The aim of this study is to evaluate the patient's setup errors in TomoTherapy (Hi-Art II, TomoTherapy, USA) Bodyfix system (Medical Intelligence, Ele-kta, Schwabmuchen, Germany) pressure in the vacuum compression, depending on and were evaluated. Bodyfix immobilization system and vacuum pressure was compression applied to the patients who received Tomotherapy thoracic and abdominal area, 21 patients were selected and TomoTehpay treatment total 477 of MVCT images were obtained. The translational (medial-lateral: ML, anterior-posterior: AP, superior-inferior: SI directions) and rolling were recorded and analyzed statistically. Using Pearson's product-moment coefficient and One-way ANOVA, the degree of correlation depending on the different vacuum pressure levels were statistically analyzed for setup errors from five groups (p<0.05). The largest average and standard deviation of systematic errors were 6.00, 5.95 mm in the AP and SI directions, respectively. The largest average of random errors were 4.72 mm in the SI directions. The correlation coefficients were 0.485, 0.244, and 0.637 for the ML-Roll, AP-Vector, and SI-Vector, respectively. SI-Vector direction showed the best relationship. In the results of the different degree of vacuum pressure in five groups (Pressure range: 30~70 mbar), the setup errors between the ML, SI in both directions and Roll p=0.00 (p<0.05) were shown significant differences. The average errors of SI direction in the vacuum pressure of 40 mbar and 70 mbar group were 4.78 mm and -0.74 mm, respectively. In this study, the correlation between the vacuum pressure and the setup-errors were statistically analyzed. The fact that setup-errors in SI direction is dependent in vacuum pressure considerly setup-errors and movement of interal organs was identified. Finally, setup-errors, and it, based on the movement of internal organs in Bodyfix system we should apply more than 50 mbar vacuum pressure. Based on the results of this study, it is suggested that accuracy of the vacuum pressure and the quantitative analysis of movement of internal organs and the tumor should be studied.
Analysis of Variance ; Humans ; Immobilization ; Intelligence ; Vacuum

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Analysis of Overall Setup Accuracy Using On-Board Imager(R).

Sun Young MA ; Sangwook LIM ; Sooman KANG ; Tae Sig JEUNG

Korean Journal of Medical Physics.2011;22(2):67-71.

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 0degrees and 270degrees 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.
Arm ; Displacement (Psychology) ; Humans ; Hypogonadism ; Linear Energy Transfer ; Mitochondrial Diseases ; Ophthalmoplegia

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Efficiency Study of 2D Diode Array Detector for IMRT Quality Assurance.

Tae Ho KIM ; Seungjong OH ; Min Joo KIM ; Won Gyun JUNG ; Jin Beom CHUNG ; Jae Sung KIM ; Siyong KIM ; Tae Suk SUH

Korean Journal of Medical Physics.2011;22(2):61-66.

In this study, we evaluated the effect of grid size on dose calculation accuracy using 2 head & neck and 2 prostate IMRT cases and based on this study's findings, we also evaluated the efficiency of a 2D diode array detector for IMRT quality assurance. Dose distributions of four IMRT plan data were calculated at four calculation grid sizes (1.25, 2.5, 5, and 10 mm) and the calculated dose distributions were compared with measured dose distributions using 2D diode array detector. Although there was no obvious difference in pass rate of gamma analysis with 3 mm/3% acceptance criteria for the others except 10 mm grid size, we found that the pass rates of 2.5, 5 and 10 mm grid size were decreased 5%, 20% and 31.53% respectively according to the application of the fine acceptance criteria, 3 mm/3%, 2 mm/2% and 1 mm/1%. The calculation time were about 11.5 min, 4.77 min, 2.95 min, and 11.5 min at 1.25, 2.5, 5, and 10 mm, respectively and as the grid size increased to double, the calculation time decreased about one-half. The grid size effect was observed more clearly in the high gradient area than the low gradient area. In conclusion, 2.5 mm grid size is considered acceptable for most IMRT plans but at least in the high gradient area, 1.25 mm grid size is required to accurately predict the dose distribution. These results are exactly same as the precious studies' results and theory. So we confirmed that 2D array diode detector was suitable for the IMRT QA.
Head ; Neck ; Prostate

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