Feasibility of Dual-Energy Computed Tomography in Radiation Therapy Planning

신희순,신한백,조성구,조준상,한영이 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.12

In this study, the noise level, effective atomic number (Zeff ), accuracy of the computed tomography (CT) number, and the CT number to the relative electron density EDconversion curve were estimated for virtual monochromatic energy and polychromatic energy. These values were compared to the theoretically predicted values to investigate the feasibility of the use of dual-energy CT in routine radiation therapy planning. The accuracies of the parameters were within the range of acceptability. These results can serve as a stepping stone toward the routine use of dual-energy CT in radiotherapy planning.

A Simulation Study for Radiation Treatment Planning Based on the Atomic Physics of the Proton-Boron Fusion Reaction

김선미,윤도건,신한백,정주영,김무섭,김경현,장홍석,서태석 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.6

The purpose of this research is to demonstrate, based on a Monte Carlo simulation code, the procedure of radiation treatment planning for proton-boron fusion therapy (PBFT). A discrete proton beam (60 - 120 MeV) relevant to the Bragg peak was simulated using a Monte Carlo nparticle extended (MCNPX, Ver. 2.6.0, National Laboratory, Los Alamos NM, USA) simulation code. After computed tomography (CT) scanning of a virtual water phantom including air cavities, the acquired CT images were converted using the simulation source code. We set the boron uptake regions (BURs) in the simulated water phantom to achieve the proton-boron fusion reaction. Proton sources irradiated the BUR, in the phantom. The acquired dose maps were overlapped with the original CT image of the phantom to analyze the dose volume histogram (DVH). We successfully confirmed amplifications of the proton doses (average: 130%) at the target regions. From the DVH result for each simulation, we acquired a relatively accurate dose map for the treatment. A simulation was conducted to characterize the dose distribution and verify the feasibility of protonboron fusion therapy (PBFT). We observed a variation in proton range and developed a tumortargeting technique for treatment that was more accurate and powerful than both conventional proton therapy and boron-neutron capture therapy.

Feasibility study of multiplexing method using digital signal encoding technique

김규범,임현태,정용현,신한백 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10

Radiation imaging systems consisting of a large number of channels greatly benefit from multiplexing methods to reduce the number of channels with minimizing the system complexity and development cost. In conventional pixelated radiation detector modules, such as anger logic, is used to reduce a large number of channels that transmit signals to a data acquisition system. However, these methods have limitations of electrical noise and distortion at the detector edge. To solve these problems, a multiplexing concept using a digital signal encoding technique based on a time delay method for signals from detectors was developed in this study. The digital encoding multiplexing (DEM) method was developed based on the time-over-threshold (ToT) method to provide more information including the activation time, position, and energy in one-bit line. This is the major advantage of the DEM method as compared with the traditional ToT method providing only energy information. The energy was measured and calibrated by the ToT method. The energy resolution and coincidence time resolution were observed as 16% and 2.4 ns, respectively, with DEM. The position was successfully distributed on each channel. This study demonstrated the feasibility that DEM was useful to reduce the number of detector channels

The First Step Towards a Respiratory Motion Prediction for Natural-Breathing by Using a Motion Generator

김무섭,정주영,윤도건,신한백,서태석,정재홍 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.6

Respiratory gated radiation therapy (RGRT) gives accurate results when a patient’s breathing is stable and regular. Thus, the patient should be acutely aware during respiratory pattern training before undergoing the RGRT treatment. To bypass the process of respiratory pattern training, we propose a tumor location prediction system for RGRT that uses only the natural respiratory volume, and we confirm its application. In order to verify the proposed tumor location prediction system, we used an in-house phantom set. The set involved a chest phantom with target, external markers and a motion generator. Natural respiratory volume signals were generated using the random function in the MATLAB code. In the chest phantom, the target undergoes linear motion based on the respiratory signal. After a four-dimensional computed tomography (4DCT) scan of the inhouse phantom, the motion trajectory was derived as a linear equation. The accuracy of the linear equation was compared with that of the motion algorithm used by the operating motion generator. In addition, we attempted to predict the tumor’s location by using the random respiratory volume values. The correspondence rate of the linear equation derived from the 4DCT images with the motion algorithm of the motion generator was 99.41% (p > 0.05). Also, the average error rate of the tumor-location prediction was 1.23% for 26 cases. We confirmed the applicability of our proposed tumor location prediction system using the natural respiratory volume for RGRT. If additional clinical studies can be conducted, a more accurate prediction that would not require respiratory pattern training can be realized.

GATE Monte Carlo Simulation of GE Discovery 600 and a Uniformity Phantom

신희순,Ki Chun Im,최용,신한백,한영이,정광주,조준상,Sang Hee Ahn 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.11

GATE (Geant4 Application Tomography Emission) Monte Carlo simulations have been successfulin the application of emission tomography for precise modeling of various physical processes. Mostprevious studies on Monte Carlo simulations have only involved performance assessments usingvirtual phantoms. Although that allows the performance of simulated positron emission tomography(PET) to be evaluated, it does not reflect the reality of practical conditions. This restriction causessubstantial drawbacks in GATE simulations of real situations. To overcome the described limitationand to provide a method to enable simulation research relevant to clinically important issues,we conducted a GATE simulation using real data from a scanner rather than a virtual phantomand evaluated the scanner is performance. For that purpose, the system and the geometry of acommercial GE PET/ CT (computed tomography) scanner, BGO-based Discovery 600 (D600),was developed for the first time. The performance of the modeled PET system was evaluated byusing the National Electrical Manufacturers Association NEMA NU 2-2007 protocols and resultswere compared with those of the reference data. The sensitivity, scatter fraction, noise-equivalentcount rate (NECR), and resolution were estimated by using the protocol of the NEMA NU2-2007. Sensitivities were 9.01 cps/kBq at 0 cm and 9.43 cps/kBq at 10 cm. Scatter fractions were 39.5%. The NECR peak was 89.7 kcps @ 14.7 kBq/cc. Resolutions were 4.8 mm in the transaxial planeand 5.9 mm in the axial plane at 1 cm, and 6.2 mm in the transaxial plane and 6.4 mm in theaxial plane at 10 cm. The resolutions exceeded the limited value provided by the manufacturer. The uniformity phantom was simulated using the CT and the PET data. The output data in aROOT format were converted and then reconstructed by using the C program and STIR (Softwarefor Tomographic Image Reconstruction). The reconstructed images of the simulated uniformityphantom data had comparable quality even though improvement in the quality is still required. Inconclusion, we have demonstrated a successful simulation of a PET system by using scanned data. In future studies, the parameters that alter the imaging conditions, such as patient movement andphysiological change, need to be studied.

Daily adaptive proton therapy: Feasibility study of detection of tumor variations based on tomographic imaging of prompt gamma emission from proton–boron fusion reaction

최민건,Law Martin,Djeng Shin-Kien,김무섭,신한백,채보영,윤도군,서태석 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8

In this study, the images of specific prompt gamma (PG)-rays of 719 keV emitted from protoneboron reactions were analyzed using single-photon emission computed tomography (SPECT). Quantitative evaluation of the images verified the detection of anatomical changes in tumors, one of the important factors in daily adaptive proton therapy (DAPT) and verified the possibility of application of the PG-ray images to DAPT. Six scenarios were considered based on various sizes and locations compared to the reference virtual tumor to observe the anatomical alterations in the virtual tumor. Subsequently, PG-rays SPECT images were acquired using the modified ordered subset expectation-maximization algorithm, and these were evaluated using quantitative analysis methods. The results confirmed that the pixel range and location of the highest value of the normalized pixel in the PG-rays SPECT image profile changed according to the size and location of the virtual tumor. Moreover, the alterations in the virtual tumor size and location in the PG-rays SPECT images were similar to the true size and location alterations set in the phantom. Based on the above results, the tumor anatomical alterations in DAPT could be adequately detected and verified through SPECT imaging using the 719 keV PG-rays acquired during treatment