Improvement with the Multi-material Decomposition Framework in Dual-energy Computed Tomography: A Phantom Study

Haenghwa Lee,Hee-Joung Kim,Donghoon Lee,Dohyeon Kim,Seungyeon Choi,Minjae Lee 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.6

Dual energy computed tomography (DECT) enhances tissue characterization by obtaining two or three material images from two measurements with different X-ray spectra. Recently, multi-material decomposition (MMD) in DECT has been studied to obtain decomposed material images for more than three basis materials. However, the MMD method is highly sensitive to noise fluctuation due to the direct inversion and the material triplet selection for each pixel. Although several studies have reported to reduce the noise resulting from direct inversion, no studies have researched reduction in the image quality degradation caused by material triplet selection. We proposed a MMD framework for DECT that includes pre-decomposition and post-decomposition stages to reduce image quality degradation due to material triplet selection and direct inversion. The total variation denoising method was applied to the pre-decomposition and the post-decomposition stages as a noise suppression algorithm. The digital phantom, tissue characterization phantom, and Catphan phantom were employed as test objects in this study. The volume fraction accuracy (VFA) and the standard deviation (STD) were quantitatively calculated to evaluate the quality of the decomposed images. The results of the proposed method were compared to those of the direct MMD (DMMD) and the MMD with total variation denoising (MMD-TVD) methods. Compared to the DMMD method, the proposed method improved average the VFA value by 11.40%, 17.31%, and 19.13% in the digital phantom, the tissue characterization phantom, and the Catphan phantom studies, respectively. The STD values for the proposed method are better than those of the DMMD method, and are similar to those of the MMD-TVD method. Our method successfully improved quantification accuracy and suppressed noise. In conclusion, the proposed method resulted in quantitatively better multi-material images for DECT.

Investigation to design of ultra-high-resolution parallel-hole collimator with CdTe photon counting detector

Youngjin Lee(이영진),Hee-Joung Kim(김희중),Yong-Gu Lee(이용구),Haenghwa Lee(이행화),Sunghoon Choi(최성훈),Byungdu Jo(조병두),Jong Seok Kim(김종석),Se Young Bae(배세영),Mi Hee Lee(이미희),Se Hee Han(한세희) 대한전자공학회 2015 대한전자공학회 학술대회 Vol.2015 No.6

Comparison study of image quality and effective dose in dual energy chest digital tomosynthesis

Lee, Donghoon,Choi, Sunghoon,Lee, Haenghwa,Kim, Dohyeon,Choi, Seungyeon,Kim, Hee-Joung Elsevier 2018 Radiation physics and chemistry Vol.148 No.-

<P>The present study aimed to introduce a recently developed digital tomosynthesis system for the chest and describe the procedure for acquiring dual energy bone decomposed tomosynthesis images. Various beam quality and reconstruction algorithms were evaluated for acquiring dual energy chest digital tomosynthesis (CDT) images and the effective dose was calculated with ion chamber and Monte Carlo simulations. The results demonstrated that dual energy CDT improved visualization of the lung field by eliminating the bony structures. In addition, qualitative and quantitative image quality of dual energy CDT using iterative reconstruction was better than that with filtered backprojection (FBP) algorithm. The contrast-to-noise ratio and figure of merit values of dual energy CDT acquired with iterative reconstruction were three times better than those acquired with FBP reconstruction. The difference in the image quality according to the acquisition conditions was not noticeable, but the effective dose was significantly affected by the acquisition condition. The high energy acquisition condition using 130 kVp recorded a relatively high effective dose. We conclude that dual energy CDT has the potential to compensate for major problems in CDT due to decomposed bony structures, which induce significant artifacts. Although there are many variables in the clinical practice, our results regarding reconstruction algorithms and acquisition conditions may be used as the basis for clinical use of dual energy CDT imaging.</P>

Comparison study of various beam modulation schemes on image quality in chest digital tomosynthesis (CDT) system

Kim, Dohyeon,Lee, Donghoon,Lee, Haenghwa,Kim, Hyemi,Chao, Zhen,Lee, Minjae,Kim, Hee-Joung Pergamon 2018 Radiation physics and chemistry Vol.152 No.-

<P><B>Abstract</B></P> <P>Recently, digital tomosynthesis systems have been actively investigated to reduce radiation dose in medical imaging. In this work, we present various beam modulation schemes for low-dose digital tomosynthesis; we compared the effects of the various acquisition schemes on image quality. A prototype chest digital tomosynthesis (CDT) system (LISTEM, Korea) and the LUNGMAN phantom (Kyoto Kagaku, Japan) with lung nodules were used in this study. A total of 81 projection data obtained through various beam modulation schemes over a 40° angular range were reconstructed using the filtered back projection (FBP) algorithm. The contrast noise ratio (CNR), structural similarity index (SSIM), and peak signal-to-noise ratio (PSNR) of the lung nodules were calculated to evaluate the image quality depending on the acquisition scheme. The reconstructed images obtained based on the proposed beam modulation schemes showed enhanced contrast in addition to a reduction of the area dose. It was determined that the beam modulation schemes affect the image quality. Among beam modulation schemes we investigated, the bunched view acquisition (outer focused) showed promising results within the region of interest (ROI). The reconstructed image obtained using the bunched view showed an increase of the CNR value by 63% compared to the conventional acquisition method. In addition, shutter scan acquisition showed promising results for the restoration information for the outside ROI. We determined that the beam modulation schemes in the prototype CDT system affect the image quality. It is also expected that the patient exposure dose can be reduced by modulating the beam size in the prototype CDT system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have proposed three beam modulation schemes in a prototype chest digital tomosynthesis (CDT) system. </LI> <LI> We found that beam modulation schemes in the prototype CDT system affect the image quality. </LI> <LI> Patient exposure dose can be reduced by modulating the beam size in the prototype CDT system. </LI> </UL> </P>

Development of a prototype chest digital tomosynthesis (CDT) R/F system with fast image reconstruction using graphics processing unit (GPU) programming

Choi, Sunghoon,Lee, Seungwan,Lee, Haenghwa,Lee, Donghoon,Choi, Seungyeon,Shin, Jungwook,Seo, Chang-Woo,Kim, Hee-Joung Elsevier 2017 Nuclear Instruments & Methods in Physics Research. Vol.848 No.-

<P><B>Abstract</B></P> <P>Digital tomosynthesis offers the advantage of low radiation doses compared to conventional computed tomography (CT) by utilizing small numbers of projections (~80) acquired over a limited angular range. It produces 3D volumetric data, although there are artifacts due to incomplete sampling. Based upon these characteristics, we developed a prototype digital tomosynthesis R/F system for applications in chest imaging. Our prototype chest digital tomosynthesis (CDT) R/F system contains an X-ray tube with high power R/F pulse generator, flat-panel detector, R/F table, electromechanical radiographic subsystems including a precise motor controller, and a reconstruction server. For image reconstruction, users select between analytic and iterative reconstruction methods. Our reconstructed images of Catphan700 and LUNGMAN phantoms clearly and rapidly described the internal structures of phantoms using graphics processing unit (GPU) programming. Contrast-to-noise ratio (CNR) values of the CTP682 module of Catphan700 were higher in images using a simultaneous algebraic reconstruction technique (SART) than in those using filtered back-projection (FBP) for all materials by factors of 2.60, 3.78, 5.50, 2.30, 3.70, and 2.52 for air, lung foam, low density polyethylene (LDPE), Delrin<SUP>®</SUP> (acetal homopolymer resin), bone 50% (hydroxyapatite), and Teflon, respectively. Total elapsed times for producing 3D volume were 2.92s and 86.29s on average for FBP and SART (20 iterations), respectively. The times required for reconstruction were clinically feasible. Moreover, the total radiation dose from our system (5.68mGy) was lower than that of conventional chest CT scan. Consequently, our prototype tomosynthesis R/F system represents an important advance in digital tomosynthesis applications.</P>

Development of a chest digital tomosynthesis r/f system and implementation of low‐dose gpu‐accelerated compressed sensing (cs) image reconstruction

Choi, Sunghoon,Lee, Haenghwa,Lee, Donghoon,Choi, Seungyeon,Lee, Chang‐,Lae,Kwon, Woocheol,Shin, Jungwook,Seo, Chang‐,Woo,Kim, Hee‐,Joung Published for the American Association of Physicis 2018 Medical physics Vol.45 No.5

In-House Developed Surface-Guided Repositioning and Monitoring System to Complement In-Room Patient Positioning System for Spine Radiosurgery

Kim, Kwang Hyeon,Lee, Haenghwa,Sohn, Moon-Jun,Mun, Chi-Woong Korean Society of Medical Physics 2021 의학물리 Vol.32 No.2

Purpose: This study aimed to develop a surface-guided radiosurgery system customized for a neurosurgery clinic that could be used as an auxiliary system for improving the accuracy, monitoring the movements of patients while performing hypofractionated radiosurgery, and minimizing the geometric misses. Methods: RGB-D cameras were installed in the treatment room and a monitoring system was constructed to perform a three-dimensional (3D) scan of the body surface of the patient and to express it as a point cloud. This could be used to confirm the exact position of the body of the patient and monitor their movements during radiosurgery. The image from the system was matched with the computed tomography (CT) image, and the positional accuracy was compared and analyzed in relation to the existing system to evaluate the accuracy of the setup. Results: The user interface was configured to register the patient and display the setup image to position the setup location by matching the 3D points on the body of the patient with the CT image. The error rate for the position difference was within 1-mm distance (min, -0.21 mm; max, 0.63 mm). Compared with the existing system, the differences were found to be as follows: x=0.08 mm, y=0.13 mm, and z=0.26 mm. Conclusions: We developed a surface-guided repositioning and monitoring system that can be customized and applied in a radiation surgery environment with an existing linear accelerator. It was confirmed that this system could be easily applied for accurate patient repositioning and inter-treatment motion monitoring.

Feasibility study of shutter scan acquisition for region of interest ( ROI ) digital tomosynthesis

Kim, Dohyeon,Jo, Byungdu,Lee, Donghoon,Lee, Haenghwa,Choi, Sunghoon,Kim, Hyemi,Chao, Zhen,Choi, Seungyeon,Kim, Hee‐,Joung unknown 2018 Journal of applied clinical medical physics Vol.19 No.3

<P><B>Abstract</B></P><P>Dose reduction techniques have been studied in medical imaging. We propose shutter scan acquisition for region of interest (ROI) imaging to reduce the patient exposure dose received from a digital tomosynthesis system. A prototype chest digital tomosynthesis (CDT) system (LISTEM, Wonju, Korea) and the LUNGMAN phantom (Kyoto Kagaku, Japan) with lung nodules 8, 10, and 12 mm in size were used for this study. A total of 41 projections with shutter scan acquisition consisted of 21 truncated projections and 20 non‐truncated projections. For comparison, 41 projections using conventional full view scan acquisition were also acquired. Truncated projections obtained by shutter scan acquisition were corrected by proposed image processing procedure to remove the truncation artifacts. The image quality was evaluated using the contrast to noise ratio (CNR), coefficient of variation (COV), and figure of merit (FOM). We measured the dose area product (DAP) value to verify the dose reduction using shutter scan acquisition. The ROI of the reconstructed image from shutter scan acquisition showed enhanced contrast. The results showed that CNR values of 8 and 12 mm lung nodules increased by 6.38% and 21.21%, respectively, and the CNR value of 10 mm lung nodule decreased by 3.63%. COV values of the lung nodules were lower in a shutter scan image than in a full view scan image. FOM values of 8, 10, and 12 mm lung nodules increased by 3.06, 2.25, and 2.33 times, respectively. This study compared the proposed shutter scan and conventional full view scan acquisition. In conclusion, using a shutter scan acquisition method resulted in enhanced contrast images within the ROI and higher FOM values. The patient exposure dose of the proposed shutter scan acquisition method can be reduced by limiting the field of view (FOV) to focus on the ROI.</P>

Accuracy evaluation of real-time body surface imaging guided system in spinal stereotactic radiosurgery: a phantom study

Park Jeong-Mee,Lee Haenghwa,Sohn Moon-Jun,Kim Kwang Hyeon,Koo Hae-Won,Yoon Sang-Won,Moon Chi-Woong 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.1

Accuracy of position setup and monitoring is a key element in the success of spinal stereotactic radiosurgery. We investigated the reposition and target accuracies of a proposed complementary surface imaging guided (SIG) application to infrared (IR) fiducial marker system for patient setup in the spinal radiosurgery. Among the iterative closest point (ICP) and normal distribution transformation (NDT) algorithm, the appropriate method for SIG system was selected by measuring the reposition accuracy. To evaluate the performance of SIG and marker systems, the reposition and target accuracies was measured by dividing into three groups; Group 1 (infrared (IR)-fiducial marker system alone), Group 2 (SIG alone), and Group 3 (combination of Group1 and 2). Overall, six degrees of freedom (DOF) and the root-mean-square (RMS) values were calculated to evaluate the performance of reposition and target accuracies. The RMS value of ICP and NDT was 3.18 ± 1.80 mm and 0.88 ± 0.71 mm, respectively. The real-time reposition accuracy using NDT algorithm were 0.29 ± 0.50 mm in Group 1, 0.79 ± 0.62 mm in Group 2 and 0.13 ± 0.05 mm in Group 3. Target accuracy of Group 3 (RMS of 0.90 ± 0.62 mm) was superior to that of Group 1and 2 (1.23 ± 0.81 mm and 1.93 ± 1.26 mm, respectively). The positioning and target accuracy were statistically significantly improved by implementing real-time SIG system complementary to conventional IR—fiducial marker-guided system in stereotactic body radiosurgery.

Feasibility study of block-matching and 3D filtering denoising algorithm in multi-material decomposition technique for dual-energy computed tomography

Heo Seo-Yeong,An Byungheon,Kim Dohyeon,Park Minji,Lee Haenghwa,Lee Youngjin 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.3

AS a medical imaging technology, dual-energy computed tomography (DECT) has attracted attention owing to its higher accuracy in terms of material separation compared with conventional single-energy CT imaging. A multi-material decomposition (MMD) technique that can separate two or more materials from DECT images has recently been developed. Although a highly accurate material separation can be obtained when MMD technology is applied to CT images, the inevitable addition of noise to the image is a disadvantage. Thus, block-matching and 3D fltering (BM3D) denoising algorithm was modeled to evaluate its applicability to CT images of materials separated using MMD technology. The simulation results confrmed that when the BM3D denoising algorithm was applied to CT images separated from the material using MMD technology, the root mean square (RMS), structural similarity index, and coefcient of variation (COV) were improved by 92.44%, 16.44%, and 92.82%, respectively, compared to when only MMD was applied. In addition, the experimental results showed the same tendencies as the simulations, and volume fraction accuracy (VFA) along with the RMS and COV evaluation parameters showed the best results when BM3D was applied to CT images. Improved results were obtained using the BM3D denoising algorithm when applying the MMD technique to DECT images.