Radiation Dose Reduction of Chest CT with Iterative Reconstruction in Image Space - Part I: Studies on Image Quality Using Dual Source CT

황혜전,서준범,이진성,송재우,김성수,이현주,임채훈 대한영상의학회 2012 Korean Journal of Radiology Vol.13 No.6

Objective: To determine whether the image quality (IQ) is improved with iterative reconstruction in image space (IRIS), and whether IRIS can be used for radiation reduction in chest CT. Materials and Methods: Standard dose chest CT (SDCT) in 50 patients and low dose chest CT (LDCT) in another 50 patients were performed, using a dual-source CT, with 120 kVp and same reference mAs (50 mAs for SDCT and 25 mAs for LDCT) employed to both tubes by modifying a dual-energy scan mode. Full-dose data were obtained by combining the data from both tubes and half-dose data were separated from a single tube. These were reconstructed by using a filtered back projection (FBP) and IRIS: full-dose FBP (F-FBP); full-dose IRIS (F-IRIS); half-dose FBP (H-FBP) and half-dose IRIS (H-IRIS). Objective noise was measured. The subjective IQ was evaluated by radiologists for the followings: noise, contrast and sharpness of mediastinum and lung. Results: Objective noise was significantly lower in H-IRIS than in F-FBP (p < 0.01). In both SDCT and LDCT, the IQ scores were highest in F-IRIS, followed by F-FBP, H-IRIS and H-FBP, except those for sharpness of mediastinum, which tended to be higher in FBP. When comparing CT images between the same dose and different reconstruction (F-IRIS/F-FBP and H-IRIS/H-FBP) algorithms, scores tended to be higher in IRIS than in FBP, being more distinct in half-dose images. However, despite the use of IRIS, the scores were lower in H-IRIS than in F-FBP. Conclusion: IRIS generally helps improve the IQ, being more distinct at the reduced radiation. However, reduced radiation by half results in IQ decrease even when using IRIS in chest CT. Objective: To determine whether the image quality (IQ) is improved with iterative reconstruction in image space (IRIS), and whether IRIS can be used for radiation reduction in chest CT. Materials and Methods: Standard dose chest CT (SDCT) in 50 patients and low dose chest CT (LDCT) in another 50 patients were performed, using a dual-source CT, with 120 kVp and same reference mAs (50 mAs for SDCT and 25 mAs for LDCT) employed to both tubes by modifying a dual-energy scan mode. Full-dose data were obtained by combining the data from both tubes and half-dose data were separated from a single tube. These were reconstructed by using a filtered back projection (FBP) and IRIS: full-dose FBP (F-FBP); full-dose IRIS (F-IRIS); half-dose FBP (H-FBP) and half-dose IRIS (H-IRIS). Objective noise was measured. The subjective IQ was evaluated by radiologists for the followings: noise, contrast and sharpness of mediastinum and lung. Results: Objective noise was significantly lower in H-IRIS than in F-FBP (p < 0.01). In both SDCT and LDCT, the IQ scores were highest in F-IRIS, followed by F-FBP, H-IRIS and H-FBP, except those for sharpness of mediastinum, which tended to be higher in FBP. When comparing CT images between the same dose and different reconstruction (F-IRIS/F-FBP and H-IRIS/H-FBP) algorithms, scores tended to be higher in IRIS than in FBP, being more distinct in half-dose images. However, despite the use of IRIS, the scores were lower in H-IRIS than in F-FBP. Conclusion: IRIS generally helps improve the IQ, being more distinct at the reduced radiation. However, reduced radiation by half results in IQ decrease even when using IRIS in chest CT.

Quantitative analysis of image quality and radiation dose of ultra low dose chest CT using AI-based deep learning reconstruction algorithm ‘AiCE’

고동희(Dong-Hee Ko),이수영(Soo-Young Lee),심학준(Hak-Joon Shim)전필현(Pil-Hyeon Jeon) 대한CT영상기술학회 2021 대한CT영상기술학회지 Vol.23 No.2

초저선량 흉부 CT(ultra low dose chest CT; ULDCT)는 영상 재구성 기술의 발전으로 기존의 저선량 흉부 CT(low dose chest CT; LDCT)보다 낮은 선량을 사용하더라도 적절한 품질의 영상 획득이 가능하다. 최근 인공지능 기반의 영상 재구성 알고리즘인 AiCE(Advanced Intelligent Clear-IQ Engine)가 상용화가 되었다. 본 연구는 ULDCT에 최신 기술인 AiCE를 적용하여 팬텀 실험과 실제 환자 실험을 실시하여 영상 화질 및 방사선 선량을 정량적으로 분석해 보고자 하였다. Lung man 팬텀에 LDCT, ULDCT프로토콜로 검사하고, Noise, SNR, DLP 값을 구해 기존의 영상 재구성 방식과 이미지 품질 차이를 정량적으로 분석했다. 또한 60명의 인원을 30명씩 두 그룹으로 나누어 AiCE가 적용된 LDCT와 ULDCT 프로토콜을 사용해 검사했다. 팬텀 연구에서 방사선량은 49% 감소했고, AiCE가 적용된 ULDCT 영상이 제일 SNR값이 높고 Noise가 적었다. 환자 실험에서 방사선량은 55% 감소했다. AiCE가 적용된 ULDCT 영상은 체적이 두꺼운 upper lobe 부분에서 약 2%의 SNR 저하와 0.5%의 Noise가 증가했다. 적절한 환자의 체적 범위 내에서 선별하여 사용하는 ULDCT는 피폭 위험도를 절반 이하로 낮춰 주고 환자의 불안감을 해소하면서 최적의 영상을 획득하는 좋은 방안이 될 것으로 판단된다. With the development of new image reconstruction techniques, ultra-low-dose chest computed tomography (ULDCT) can acquire adequate image quality even in lower does than conventional low-dose chest CT (LDCT). Recently, advanced intelligent clear-IQ engine (AiCE), an artificial intelligence-based image reconstruction algorithm, has been commercialized in the medical field. In this study, AiCE, a state-of-the-art technology, was applied to ULDCT to reconstruct both phantom and human image. The lungman phantom was examined by using LDCT and ULDCT protocols. The difference in image quality which applied existing and AiCE reconstruction methods was quantitatively analyzed by computing signal to noise ratio (SNR), noise, and dose length product values. Also, under the application of same AiCE reconstruction methods, 30 patients were tested by using LDCT protocols and another 30 patients were tested by using ULDCT protocols.I n the phantom study, the radiation dose of ULDCT was reduced by 49% compared to LDCT and ULDCT images with AiCE exhibited the highest SNR value and the lowest noise. In the patient study, the radiation dose of ULDCT was reduced by 55% compared to LDCT. In ULDCT images of thick upper lobe with AiCE, the SNR increases by about 2% and the noise decreased by 0.5% compared to LDCT. The selective usage of ULDCT within appropriate body mass index range might provide the reduction of exposure risk and the optimal images while relieving patient anxiety.

Radiation Dose Reduction of Chest CT with Iterative Reconstruction in Image Space - Part II: Assessment of Radiologists’ Preferences Using Dual Source CT

황혜전,서준범,이진성,송재우,김성수,이현주,임채훈 대한영상의학회 2012 Korean Journal of Radiology Vol.13 No.6

Objective: To evaluate the impact of radiation dose and reconstruction algorithms on radiologists’ preferences, and whether an iterative reconstruction in image space (IRIS) can be used for dose reduction in chest CT. Materials and Methods: Standard dose chest CT (SDCT) in 50 patients and low dose chest CT (LDCT) in another 50 patients were performed, using a dual-source CT, with 120 kVp and same reference mAs (50 mAs for SDCT and 25 mAs for LDCT) employed to both tubes by modifying the dual-energy scan mode. Full-dose data were obtained by combining the data from both tubes and half-dose data were separated from one tube. These were reconstructed by using a filtered back projection (FBP) and IRIS: full-dose FBP (F-FBP); full-dose IRIS (F-IRIS); half-dose FBP (H-FBP) and half-dose IRIS (H-IRIS). Ten H-IRIS/F-IRIS, 10 H-FBP/H-IRIS, 40 F-FBP/F-IRIS and 40 F-FBP/H-IRIS pairs of each SDCT and LDCT were randomized. The preference for clinical usage was determined by two radiologists with a 5-point-scale system for the followings: noise, contrast, and sharpness of mediastinum and lung. Results: Radiologists preferred IRIS over FBP images in the same radiation dose for the evaluation of the lungs in both SDCT (p = 0.035) and LDCT (p < 0.001). When comparing between H-IRIS and F-IRIS, decreased radiation resulted in decreased preference. Observers preferred H-IRIS over F-FBP for the lungs in both SDCT and LDCT, even with reduced radiation dose by half in IRIS image (p < 0.05). Conclusion: Radiologists’ preference may be influenced by both radiation dose and reconstruction algorithm. According to our preliminary results, dose reduction at 50% with IRIS may be feasible for lung parenchymal evaluation. Objective: To evaluate the impact of radiation dose and reconstruction algorithms on radiologists’ preferences, and whether an iterative reconstruction in image space (IRIS) can be used for dose reduction in chest CT. Materials and Methods: Standard dose chest CT (SDCT) in 50 patients and low dose chest CT (LDCT) in another 50 patients were performed, using a dual-source CT, with 120 kVp and same reference mAs (50 mAs for SDCT and 25 mAs for LDCT) employed to both tubes by modifying the dual-energy scan mode. Full-dose data were obtained by combining the data from both tubes and half-dose data were separated from one tube. These were reconstructed by using a filtered back projection (FBP) and IRIS: full-dose FBP (F-FBP); full-dose IRIS (F-IRIS); half-dose FBP (H-FBP) and half-dose IRIS (H-IRIS). Ten H-IRIS/F-IRIS, 10 H-FBP/H-IRIS, 40 F-FBP/F-IRIS and 40 F-FBP/H-IRIS pairs of each SDCT and LDCT were randomized. The preference for clinical usage was determined by two radiologists with a 5-point-scale system for the followings: noise, contrast, and sharpness of mediastinum and lung. Results: Radiologists preferred IRIS over FBP images in the same radiation dose for the evaluation of the lungs in both SDCT (p = 0.035) and LDCT (p < 0.001). When comparing between H-IRIS and F-IRIS, decreased radiation resulted in decreased preference. Observers preferred H-IRIS over F-FBP for the lungs in both SDCT and LDCT, even with reduced radiation dose by half in IRIS image (p < 0.05). Conclusion: Radiologists’ preference may be influenced by both radiation dose and reconstruction algorithm. According to our preliminary results, dose reduction at 50% with IRIS may be feasible for lung parenchymal evaluation.

Radiation Dose Reduction of Chest CT with Iterative Reconstruction in Image Space - Part I: Studies on Image Quality Using Dual Source CT

Hwang, Hye Jeon,Seo, Joon Beom,Lee, Jin Seong,Song, Jae-Woo,Kim, Song Soo,Lee, Hyun Joo,Lim, Chae Hun The Korean Society of Radiology 2012 KOREAN JOURNAL OF RADIOLOGY Vol.13 No.6

<P><B>Objective</B></P><P>To determine whether the image quality (IQ) is improved with iterative reconstruction in image space (IRIS), and whether IRIS can be used for radiation reduction in chest CT.</P><P><B>Materials and Methods</B></P><P>Standard dose chest CT (SDCT) in 50 patients and low dose chest CT (LDCT) in another 50 patients were performed, using a dual-source CT, with 120 kVp and same reference mAs (50 mAs for SDCT and 25 mAs for LDCT) employed to both tubes by modifying a dual-energy scan mode. Full-dose data were obtained by combining the data from both tubes and half-dose data were separated from a single tube. These were reconstructed by using a filtered back projection (FBP) and IRIS: full-dose FBP (F-FBP); full-dose IRIS (F-IRIS); half-dose FBP (H-FBP) and half-dose IRIS (H-IRIS). Objective noise was measured. The subjective IQ was evaluated by radiologists for the followings: noise, contrast and sharpness of mediastinum and lung.</P><P><B>Results</B></P><P>Objective noise was significantly lower in H-IRIS than in F-FBP (p < 0.01). In both SDCT and LDCT, the IQ scores were highest in F-IRIS, followed by F-FBP, H-IRIS and H-FBP, except those for sharpness of mediastinum, which tended to be higher in FBP. When comparing CT images between the same dose and different reconstruction (F-IRIS/F-FBP and H-IRIS/H-FBP) algorithms, scores tended to be higher in IRIS than in FBP, being more distinct in half-dose images. However, despite the use of IRIS, the scores were lower in H-IRIS than in F-FBP.</P><P><B>Conclusion</B></P><P>IRIS generally helps improve the IQ, being more distinct at the reduced radiation. However, reduced radiation by half results in IQ decrease even when using IRIS in chest CT.</P>

Four-Dimensional Thoracic CT in Free-Breathing Children

Hyun Woo Goo 대한영상의학회 2019 Korean Journal of Radiology Vol.20 No.1

In pediatric thoracic CT, respiratory motion is generally treated as a motion artifact degrading the image quality. Conversely, respiratory motion in the thorax can be used to answer important clinical questions, that cannot be assessed adequately via conventional static thoracic CT, by utilizing four-dimensional (4D) CT. However, clinical experiences of 4D thoracic CT are quite limited. In order to use 4D thoracic CT properly, imagers should understand imaging techniques, radiation dose optimization methods, and normal as well as typical abnormal imaging appearances. In this article, the imaging techniques of pediatric thoracic 4D CT are reviewed with an emphasis on radiation dose. In addition, several clinical applications of pediatric 4D thoracic CT are addressed in various thoracic functional abnormalities, including upper airway obstruction, tracheobronchomalacia, pulmonary air trapping, abnormal diaphragmatic motion, and tumor invasion. One may further explore the clinical usefulness of 4D thoracic CT in free-breathing children, which can enrich one’s clinical practice.

An Improved Texture Feature Extraction Method for Recognizing Emphysema in CT Images

펭샤후,남현도 한국조명.전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.11

In this study we propose a new texture feature extraction method based on an estimation of the brightness and structural uniformity of CT images representing the important characteristics for emphysema recognition. The Center-Symmetric Local Binary Pattern (CS-LBP) is first used to combine gray level in order to describe the brightness uniformity characteristics of the CT image. Then the gradient orientation difference is proposed to generate another CS-LBP code combining with gray level to represent the structural uniformity characteristics of the CT image. The usage of the gray level, CS-LBP and gradient orientation differences enables the proposed method to extract rich and distinctive information from the CT images in multiple directions. Experimental results showed that the performance of the proposed method is more stable with respect to sensitivity and specificity when compared with the SGLDM, GLRLM and GLDM. The proposed method outperformed these three conventional methods (SGLDM, GLRLM, and GLDM) 7.85[%], 22.87[%], and 16.67[%] respectively, according to the diagnosis of average accuracy, demonstrated by the Receiver Operating Characteristic (ROC) curves.

An Improved Texture Feature Extraction Method for Recognizing Emphysema in CT Images

Peng, Shao-Hu,Nam, Hyun-Do The Korean Institute of IIIuminating and Electrica 2010 조명·전기설비학회논문지 Vol.24 No.11

In this study we propose a new texture feature extraction method based on an estimation of the brightness and structural uniformity of CT images representing the important characteristics for emphysema recognition. The Center-Symmetric Local Binary Pattern (CS-LBP) is first used to combine gray level in order to describe the brightness uniformity characteristics of the CT image. Then the gradient orientation difference is proposed to generate another CS-LBP code combining with gray level to represent the structural uniformity characteristics of the CT image. The usage of the gray level, CS-LBP and gradient orientation differences enables the proposed method to extract rich and distinctive information from the CT images in multiple directions. Experimental results showed that the performance of the proposed method is more stable with respect to sensitivity and specificity when compared with the SGLDM, GLRLM and GLDM. The proposed method outperformed these three conventional methods (SGLDM, GLRLM, and GLDM) 7.85[%], 22.87[%], and 16.67[%] respectively, according to the diagnosis of average accuracy, demonstrated by the Receiver Operating Characteristic (ROC) curves.

흉부 CT 영상에서 결절의 밝기값, 재질 및 형상 증강 영상 기반의 GGN-Net을 이용한 간유리음영 결절 자동 분류

변소현(So Hyun Byun),정주립(Julip Jung),홍헬렌(Helen Hong),송용섭(Yong Sub Song),김형진(Hyungjin Kim),박창민(Chang Min Park) 한국컴퓨터그래픽스학회 2018 컴퓨터그래픽스학회논문지 Vol.24 No.5

본 논문에서는 흉부 CT 영상에서 결절의 밝기값, 재질 및 형상 증강 영상 기반의 GGN-Net을 이용해 간유리음영 결절 자동 분류 방법을 제안한다, 첫째, 입력 영상에 결절 내부의 고형 성분의 유무 및 크기 정보가 포함될 수 있도록 밝기값, 재질 및 형상 증강 영상의 활용을 제안한다. 둘째, 다양한 입력 영상을 여러 개의 컨볼루션 모듈을 통해 획득한 특징맵을 내부 네트워크에서 통합하여 훈련하는 GGN-Net를 제안한다. 제안 방법의 분류 정확성 평가를 위해 순수 간유리음영 결절 90개와 고형 성분의 크기가 5mm 미만인 혼합 간유리음영 결절 38개, 5mm 이상 고형 성분의 크기를 가지는 혼합 간유리음영 결절 23개의 데이터를 사용하였으며, 입력 영상이 간유리음영 결절 분류 결과에 미치는 영향을 비교하기 위해 다양한 입력 영상을 구성하여 결과를 비교하였다. 실험 결과, 밝기값, 재질 및 형상 정보가 함께 고려된 입력 영상을 사용한 제안 방법이 정확도가 82.75%로 가장 좋은 결과를 보였다. In this paper, we propose an automated method for the ground-glass nodule(GGN) classification using GGN-Net based on intensity, texture, and shape-enhanced images in chest CT images. First, we propose the utilization of image that enhances the intensity, texture, and shape information so that the input image includes the presence and size information of the solid component in GGN. Second, we propose GGN-Net which integrates and trains feature maps obtained from various input images through multiple convolution modules on the internal network. To evaluate the classification accuracy of the proposed method, we used 90 pure GGNs, 38 part-solid GGNs less than 5mm with solid component, and 23 part-solid GGNs larger than 5mm with solid component. To evaluate the effect of input image, various input image set is composed and classification results were compared. The results showed that the proposed method using the composition of intensity, texture and shape-enhanced images showed the best result with 82.75% accuracy.

An Improved Texture Feature Extraction Method for Recognizing Emphysema in CT Images

Shao-Hu Peng,Hyun-Do Nam 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.11

In this study we propose a new texture feature extraction method based on an estimation of the brightness and structural uniformity of CT images representing the important characteristics for emphysema recognition. The Center-Symmetric Local Binary Pattern (CS-LBP) is first used to combine gray level in order to describe the brightness uniformity characteristics of the CT image. Then the gradient orientation difference is proposed to generate another CS-LBP code combining with gray level to represent the structural uniformity characteristics of the CT image. The usage of the gray level, CS-LBP and gradient orientation differences enables the proposed method to extract rich and distinctive information from the CT images in multiple directions. Experimental results showed that the performance of the proposed method is more stable with respect to sensitivity and specificity when compared with the SGLDM, GLRLM and GLDM The proposed method outperformed these three conventional methods (SGLDM, GLRLM, and GLDM) 7.85[%], 22.87[%], and 16.67[%] respectively, according to the diagnosis of average accuracy, demonstrated by the Receiver Operating Characteristic (ROC) curves.

A Temporal Subtraction Method for Thoracic CT Images Using Non Rigid Warping Technique

Takumi Tokisa,Hyoungseop Kim,Joo Kooi Tan,Seiji Ishikawa,Young Lae Moon,Sung Ho Yoon,Wontae Kim 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

A temporal subtraction technique which is subtracted from previous image to current one is introduced as powerful tools in medical fields to diagnose abnormalities. It provided a computer aided diagnosis (CAD) tools on visual screening. Radiologist can detect lesions on image by compare the two images. It is because the subtraction image can enhance the temporal changes, such as shaped of new lesions and/or the temporal changes in existing abnormalities by removing most of the normal background structures by subtraction of a previous image from a current one. There are some technical reports to register the different images until now. But subtraction artifacts are still remained which are caused by mis-registration. In this paper, we propose a new method for temporal subtraction method on thoracic MDCT images using non-rigid image warping techniques based on free form deformation (FFD). We applied our method to two clinical cases of chest CT image sets and compare to conventional methods in terms of computational cost and accuracy.