Sungkoo Cho

The first private-hospital based proton therapy center in Korea; status of the Proton Therapy Center at Samsung Medical Center

Purpose The purpose of this report is to describe the proton therapy system at Samsung Medical Center (SMC-PTS) including the proton beam generator, irradiation system, patient positioning system, patient position verification system, respiratory gating system, and operating and safety control system, and review the current status of the SMC-PTS. Materials and Methods The SMC-PTS has a cyclotron (230 MeV) and two treatment rooms: one treatment room is equipped with a multi-purpose nozzle and the other treatment room is equipped with a dedicated pencil beam scanning nozzle. The proton beam generator including the cyclotron and the energy selection system can lower the energy of protons down to 70 MeV from the maximum 230 MeV. Results The multi-purpose nozzle can deliver both wobbling proton beam and active scanning proton beam, and a multi-leaf collimator has been installed in the downstream of the nozzle. The dedicated scanning nozzle can deliver active scanning proton beam with a helium gas filled pipe minimizing unnecessary interactions with the air in the beam path. The equipment was provided by Sumitomo Heavy Industries Ltd., RayStation from RaySearch Laboratories AB is the selected treatment planning system, and data management will be handled by the MOSAIQ system from Elekta AB. Conclusion The SMC-PTS located in Seoul, Korea, is scheduled to begin treating cancer patients in 2015.

Development of a 3D optical scanning-based automatic quality assurance system for proton range compensators

PURPOSEnA new automatic quality assurance (AutoRCQA) system using a three-dimensional scanner (3DS) with system automation was developed to improve the accuracy and efficiency of the quality assurance (QA) procedure for proton range compensators (RCs). The system performance was evaluated for clinical implementation.nnnMETHODSnThe AutoRCQA system consists of a three-dimensional measurement system (3DMS) based on 3DS and in-house developed verification software (3DVS). To verify the geometrical accuracy, the planned RC data (PRC), calculated with the treatment planning system (TPS), were reconstructed and coregistered with the measured RC data (MRC) based on the beam isocenter. The PRC and MRC inner surfaces were compared with composite analysis (CA) using 3DVS, using the CA pass rate for quantitative analysis. To evaluate the detection accuracy of the system, the authors designed a fake PRC by artificially adding small cubic islands with side lengths of 1.5, 2.5, and 3.5 mm on the inner surface of the PRC and performed CA with the depth difference and distance-to-agreement tolerances of [1 mm, 1 mm], [2 mm, 2 mm], and [3 mm, 3 mm]. In addition, the authors performed clinical tests using seven RCs [computerized milling machine (CMM)-RCs] manufactured by CMM, which were designed for treating various disease sites. The systematic offsets of the seven CMM-RCs were evaluated through the automatic registration function of AutoRCQA. For comparison with conventional technique, the authors measured the thickness at three points in each of the seven CMM-RCs using a manual depth measurement device and calculated thickness difference based on the TPS data (TPS-manual measurement). These results were compared with data obtained from 3DVS. The geometrical accuracy of each CMM-RC inner surface was investigated using the TPS data by performing CA with the same criteria. The authors also measured the net processing time, including the scan and analysis time.nnnRESULTSnThe AutoRCQA system accurately detected all fake objects in accordance with the given criteria. The median systematic offset of the seven CMM-RCs was 0.08 mm (interquartile range: -0.25 to 0.37 mm) and -0.08 mm (-0.58 to 0.01 mm) in the X- and Y-directions, respectively, while the median distance difference was 0.37 mm (0.23-0.94 mm). The median thickness difference of the TPS-manual measurement at points 1, 2, and 3 was -0.4 mm (-0.4 to -0.2 mm), -0.2 mm (-0.3 to 0.0 mm), and -0.3 mm (-0.6 to -0.1 mm), respectively, while the median difference of 3DMS was 0.0 mm (-0.1 to 0.2 mm), 0.0 mm (-0.1 to 0.3 mm), and 0.1 mm (-0.1 to 0.2 mm), respectively. Thus, 3DMS showed slightly better values compared to the manual measurements for points 1 and 3 in statistical analysis (p < 0.05). The average pass rate of the seven CMM-RCs was 97.97% ± 1.68% for 1-mm CA conditions, increasing to 99.98% ± 0.03% and 100% ± 0.00% for 2- and 3-mm CA conditions, respectively. The average net analysis time was 18.01 ± 1.65 min.nnnCONCLUSIONSnThe authors have developed an automated 3DS-based proton RC QA system and verified its performance. The AutoRCQA system may improve the accuracy and efficiency of QA for RCs.

Gamma electron vertex imaging for in-vivo beam-range measurement in proton therapy: Experimental results

Proton therapy, thanks to the dose characteristics of the Bragg peak, according to which most of the radiation energy is delivered at the end of the beam with a very high dose gradient at the distal edge, can deliver a highly conformal radiation dose to the treatment volume. Currently, however, the benefit of this high dose gradient is not fully utilized in clinical practice due mainly to the dose-distribution uncertainty in the beam direction (i.e., the uncertainty of the beam range in the patient). In this paper, we present an imaging system based on gamma electron vertex imaging (GEVI), which is suitable for high-energy (1–30u2009MeV) gammas, and test its performance for therapeutic proton beams. GEVI images prompt gamma vertices, which are closely correlated with the dose distribution at the distal edge, by converting prompt gammas to electrons via Compton scattering and then tracking the recoiled electrons. Our experimental results show that the GEVI system can image the 2D vertices of the prompt gammas and, thus, can be utilized for the measurement of proton-beam ranges in patients. We believe, indeed, that GEVI makes possible real-time monitoring of in-vivo proton-beam ranges, whose utility significantly improves treatment effectiveness and enhances patient safety. We also expect that the GEVI system will find applications in other fields (e.g., gamma-ray astronomy, nuclear engineering, and high-energy physics) requiring high-energy-gamma (1–30u2009MeV) imaging.

MEASUREMENT OF NEUTRON AMBIENT DOSE EQUIVALENT IN PROTON RADIOTHERAPY WITH LINE-SCANNING AND WOBBLING MODE TREATMENT SYSTEM

Abstract The primary objective of this study was to measure secondary neutron dose during proton therapy using a detector that covers the entire neutron energy range produced in proton therapy. We analyzed and compared the neutron dose during proton treatment with passive scattering and line scanning. The neutron ambient dose equivalents were measured with a 190 MeV wobbling and line‐scanning proton beam. The center of a plastic water phantom (30 × 30 × 60 cm3) was placed at the isocenter. A Wide‐Energy Neutron Detection Instrument (WENDI‐2) was located 1m from the isocenter at four different angles (0°, 45°, 90° and 135°). Both wobbling and line‐scanning modes of a multipurpose and pencil beam scanning dedicated nozzles were used to obtain a spread‐out Bragg peak with 10‐cm‐width for the measurements. The ambient dose equivalent H*(10) value was normalized by the proton therapeutic dose at the isocenter. For wobbling mode and line‐scanning mode, the highest H*(10) values were 1.972 and 0.099 mSv/Gy, respectively. We successfully measured the neutron ambient dose equivalents at six positions generated by a 190 MeV proton beam using wobbling and line‐scanning mode with the WENDI‐2. These reference data could be used for neutron dose reduction methods and other analysis for advanced proton treatment in the near future.

SU-E-T-569: Neutron Shielding Calculation Using Analytical and Multi-Monte Carlo Method for Proton Therapy Facility

Purpose: To evaluate the shielding wall design to protect patients, staff and member of the general public for secondary neutron using a simply analytic solution, multi-Monte Carlo code MCNPX, ANISN and FLUKA. Methods: An analytical and multi-Monte Carlo method were calculated for proton facility (Sumitomo Heavy Industry Ltd.) at Samsung Medical Center in Korea. The NCRP-144 analytical evaluation methods, which produced conservative estimates on the dose equivalent values for the shielding, were used for analytical evaluations. Then, the radiation transport was simulated with the multi-Monte Carlo code. The neutron dose at evaluation point is got by the value using the production of the simulation value and the neutron dose coefficient introduced in ICRP-74. Results: The evaluation points of accelerator control room and control room entrance are mainly influenced by the point of the proton beam loss. So the neutron dose equivalent of accelerator control room for evaluation point is 0.651, 1.530, 0.912, 0.943 mSv/yr and the entrance of cyclotron room is 0.465, 0.790, 0.522, 0.453 mSv/yr with calculation by the method of NCRP-144 formalism, ANISN, FLUKA and MCNP, respectively. The most of Result of MCNPX and FLUKA using the complicated geometry showed smaller values than Result of ANISN. Conclusion: Themorexa0» neutron shielding for a proton therapy facility has been evaluated by the analytic model and multi-Monte Carlo methods. We confirmed that the setting of shielding was located in well accessible area to people when the proton facility is operated.«xa0less

SU-E-I-37: Low-Dose Real-Time Region-Of-Interest X-Ray Fluoroscopic Imaging with a GPU-Accelerated Spatially Different Bilateral Filtering

PURPOSEnThe purpose of our study is to reduce imaging radiation dose while maintaining image quality of region of interest (ROI) in X-ray fluoroscopy. A low-dose real-time ROI fluoroscopic imaging technique which includes graphics-processing-unit- (GPU-) accelerated image processing for brightness compensation and noise filtering was developed in this study.nnnMETHODSnIn our ROI fluoroscopic imaging, a copper filter is placed in front of the X-ray tube. The filter contains a round aperture to reduce radiation dose to outside of the aperture. To equalize the brightness difference between inner and outer ROI regions, brightness compensation was performed by use of a simple weighting method that applies selectively to the inner ROI, the outer ROI, and the boundary zone. A bilateral filtering was applied to the images to reduce relatively high noise in the outer ROI images. To speed up the calculation of our technique for real-time application, the GPU-acceleration was applied to the image processing algorithm. We performed a dosimetric measurement using an ion-chamber dosimeter to evaluate the amount of radiation dose reduction. The reduction of calculation time compared to a CPU-only computation was also measured, and the assessment of image quality in terms of image noise and spatial resolution was conducted.nnnRESULTSnMore than 80% of dose was reduced by use of the ROI filter. The reduction rate depended on the thickness of the filter and the size of ROI aperture. The image noise outside the ROI was remarkably reduced by the bilateral filtering technique. The computation time for processing each frame image was reduced from 3.43 seconds with single CPU to 9.85 milliseconds with GPU-acceleration.nnnCONCLUSIONnThe proposed technique for X-ray fluoroscopy can substantially reduce imaging radiation dose to the patient while maintaining image quality particularly in the ROI region in real-time.

SU‐E‐T‐112: Dose Distribution Verification of Proton Beam Using Light Output On Scintillation Plate

PURPOSEnTo verify dose distribution of proton beam using CCD camera scintillation screen system.nnnMETHODSnCCD camera scintillation screen system was developed to verify dose distribution at National Cancer Center in Korea. In this study, we used a high sensitivity scintillation plate to measure visible light acquired by CCD camera. The light output on scintillation plate was measured while changing the irradiation time and beam current in proton beam. Then, the results were analyzed to obtain the depth dose distribution and dose profile. The measured dose distributions in double scattering delivery mode were compared with those in ionization chamber.nnnRESULTSnThe relationship between the light output and beam current showed good linearity. Also, the light output increased linearly with the increase of irradiation time. For the proton beam for double scattering mode, light output response on scintillation plate was compared with the dose distribution from ionization chamber and showed the good agreement.nnnCONCLUSIONnWe evaluated the dosimetry characteristic of proton beam using CCD camera scintillation screen system. Also, we verified the dos - e distribution of proton beam for double scattering delivery mode. This work was supported by a research grant from the Ministry of Education, Science and Technology in Korea (No. 2010-0026071) and a fund from research project of the Korea National Cancer Center (No. NCC-0910110).

SU‐E‐I‐98: Novel Method for Proton Radiography Using Plastic Scintillation Plate and Beam Energy Modulation Water Phantom

PURPOSEnThe purpose of this study is to present the experimental evaluation and quantification of proton radiography using plastic scintillation plate and beam energy modulation (BEM) water phantom.nnnMETHODSnUsing the newly designed water phantom, proton beam energy was modulated by controlling water depth horizontally. Modulated proton beam which passed through water phantom was measured by dose-measurement system which consists of a plastic scintillation plate, a mirror and a CCD camera in a dark box. A range compensator (RC) was positioned between BEM water phantom and scintillation plate for proton radiography. While a proton beam which has 15 cm range in water was being irradiated on RC, water depth is controlled from 71 to 170 mm in 1 mm increment and radiographs of RC on a scintillation plate were saved in every 1 mm increment using a dose-measurement system. One hundred images were stacked and the position of Bragg peak was found along the stack order. The same radiograph procedure was performed without RC in order to calculate the depth of RC by subtracting the position index of Bragg peak between radiograph of RC and background. This difference was divided by water equivalent thickness value of RC material and then measured depth of RC was compared to plan data, quantifying the precision with the mean absolute depth difference (MADD) and the standard deviation (SD).nnnRESULTSnThe MADD and the SD over the entire areas of RC was calculated as 0.62 mm and 0.67 mm respectively. MADD and SD precisions over chosen flat regions were less than 0.54 mm and 0.25 mm.nnnCONCLUSIONnGood image quality with high precision of depth measurement was observed by our proton radiography system. These system can also be used as a 3D dosimetry tool. This study was supported by funds from research projects of the National Cancer Center of Korea (nos. NCC 1210210) and National Research Foundation of Korea (K1A3A1A21 2010 0026071).

SU‐E‐J‐63: Feasibility Study of Proton Digital Tomosynthesis in Proton Beam Therapy

PURPOSEnWe investigated the feasibility of proton tomosynthesis as daily positioning of patients and compared the results with photon tomosynthesis as an alternative to conventional portal imaging or on-board cone-beam computed tomography.nnnMETHODSnDedicated photon-like proton beam using the passively scattered proton beams by the cyclotron was generated for proton imaging. The eleven projections were acquired over 30 degree with 3 degree increment in order to investigate the performance of proton tomosynthesis. The cylinder blocks and resolution phantom were used to evaluate imaging performance. Resolution phantom of a cylinder of diameter 12 cm was used to investigate the reconstructed imaging characteristics. Electron density cylinder blocks with diameter of 28 mm and height of 70 mm were employed to assess the imaging quality. The solid water, breast, bone, adipose, lung, muscle, and liver, which were tissue equivalent inserts, were positioned around the resolution phantom. The images were reconstructed by projection onto convex sets (POCS) algorithm and total variation minimization (TVM) methods. The Gafchromic EBT films were utilized for measuring the photon-like proton beams as a proton detector. In addition, the photon tomosynthesis images were obtained for a comparison with proton tomosynthesis images. The same angular sampling data were acquired for both proton and photon tomosynthesis.nnnRESULTSnIn the resolution phantom image obtained proton tomosynthesis, down to 1.6 mm diameter rods were resolved visually, although the separation between adjacent rods was less distinct. In contrast, down to 1.2 mm diameter rods were resolved visually in the reconstructed image obtained photon tomosynthesis. Both proton and photon tomosynthesis images were similar in intensities of different density blocks.nnnCONCLUSIONSnOur results demonstrated that proton tomosynthesis could make it possible to provide comparable tomography imaging to photon tomosynthesis for positioning as determined by manual registration of high density materials.

SU‐E‐T‐234: LET Measurement Using Nuclear Emulsion and Monte Carlo Simulation for Proton Beam

PURPOSEnThe significant issue of particle therapy such as proton and carbon ion biological effect on tumors and normal tissue. This effect closely connected with linear-energy-transfer (LET). This work presents a Monte Carlo study using GEANT4 and the verification using Nuclear Emulsion to show LET for proton beam.nnnMETHODSnNational Cancer Center (NCC) has IBA Beam Nozzle and cyclotron for proton therapy. We use proton beam bragg peak range 14cm. Also, we already developed the simulation using GEANT4 and finished validation for scattering proton beam. In our simulation, we make same condition with experimental setup.Nuclear emulsion films interleaved with tissue equivalent absorbers can be fruitfully used to reconstruct proton tracks with very high precision. This Nuclear emulsion film has been supported from Nagoya University, analyzed in Pusan University, was irradiated with a therapeutic proton beam at NCC. The Emulsion packs was located at entrance and bragg peak region of proton. This position means low and high LET region. The scanning of the emulsions has been performed at Nagoya University, where a fully automated microscopic scanning technology has been developed for the OPERA experiment on neutrino oscillations.nnnRESULTSnWe could see the reconstructed track of proton scanning emulsion. From film scanning, we got the LET distribution at low and high LET region for several proton tracks. Simulation results was similar distribution within standard deviation in acceptance level. Also we got the RBE distribution using LET measurement for proton beam.nnnCONCLUSIONSnWe measured LET at entrance and bragg peak region using Monte Carlo study and Nuclear Emulsion film, for NCC proton beam. This results means the good observation of LET using the nuclear emulsion. And this method can be used successfully in medical field.