• 대한방사선치료학회지
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• 제29권2호
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• pp.9-17
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• 2017

목 적: 방사선치료에서 CT number에 의해 나타나는 조직의 묘사 및 전자밀도는 CT(Computed Tomography)기반의 전산화치료계획 정확성을 보장하는데 중요한 역할을 한다. 하지만 체내의 금속 이식물은 CT number의 정확성을 감소시킬 뿐 아니라 조직 묘사에 대한 불확실성을 나타내기 때문에 임상에서는 metal artifact를 감소시킬 수 있는 알고리즘이 개발되었다. 이에 본 연구에서는 본원에서 사용하고 있는 GE사의 SMART MAR의 CT number 정확도를 평가하고 방사선치료에서의 유용성에 대해 평가하고자 한다. 대상 및 방법: 영상평가를 위해 CIRS ED phantom을 이용하여 6개 조직의 rod를 삽입하여 동일한 체적의 ROI를 형성 후 original 영상을 획득하고 의료용 티타늄 rod를 삽입하여 non-SMART MAR 영상과 SMART MAR영상을 획득하여 CT number와 SD값을 비교하였다. Metal artifact로 인해 CT number 변화에 따른 선량변화 확인을 위해 전산화계획시스템 Epclipse를 사용하여 CIRS ED phantom CT 영상에 PTV를 형성하여 original 영상을 획득하고 편측 티타늄 삽입, 양측 티타늄 삽입 영상을 획득하여 non-SMART MAR와 SMART MAR영상에 동일한 치료계획을 수립하여 PTV가 받는 평균처방선량, HI(Homogeneity Index), CI(Conformity Index)를 비교, 분석하였다. 흡수선량 측정은 원통형 아크릴 팬텀과 0.125 cc ionchamber, electrometer를 이용하여 선량변환상수(cCy/nC)를 계산하고 CIRS phantom을 이용하여 편측, 양측 티타늄 rod를 삽입한 영상으로 non-SMART MAR와 SMART MAR 영상을 획득하여 동일한 지점에서의 흡수선량을 측정하여 전산화치료계획상의 point dose와 비교하였다. 결 과: 영상평가 결과 CT number는 non-SMART MAR영상보다 SMART MAR 영상이 original영상에 더 유사한 값이 나왔고 SD값은 SMART MAR영상에서 더 감소되었다. 선량평가 결과 평균처방선량과 HI 및 CI 값은 SMART MAR 영상보다 non-SMART MAR 영상이 original 영상에 더 근접한 결과가 나왔지만 통계적으로 유의하지 않았다. 흡수선량 측정결과 치료계획상의 point dose와 실제 흡수선량과의 차이가 non-SMART MAR의 영상에서는 각각 2.69, 3.63 %의 차이가 있었지만 SMART MAR영상에서는 0.56, 0.68 %로 감소하였다. 결 론: 금속 이식물을 삽입한 환자의 CT 영상에 SMART MAR를 적용했을 때 CT number 정확성 상승 및 SD 감소로 영상의 질이 향상되므로 종양과 정상조직의 윤곽도 생성 및 선량계산 시 유용할 것으로 사료된다.

• IEIE Transactions on Smart Processing and Computing
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• 제4권5호
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• pp.311-317
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• 2015

The aim of this study is to develop a 3D registration algorithm for positron emission tomography/computed tomography (PET/CT) and magnetic resonance (MR) images acquired from independent PET/CT and MR imaging systems. Combined PET/CT images provide anatomic and functional information, and MR images have high resolution for soft tissue. With the registration technique, the strengths of each modality image can be combined to achieve higher performance in diagnosis and radiotherapy planning. The proposed method consists of two stages: normalized mutual information (NMI)-based global matching and independent component analysis (ICA)-based refinement. In global matching, the field of view of the CT and MR images are adjusted to the same size in the preprocessing step. Then, the target image is geometrically transformed, and the similarities between the two images are measured with NMI. The optimization step updates the transformation parameters to efficiently find the best matched parameter set. In the refinement stage, ICA planes from the windowed image slices are extracted and the similarity between the images is measured to determine the transformation parameters of the control points. B-spline. based freeform deformation is performed for the geometric transformation. The results show good agreement between PET/CT and MR images.

• 대한방사선기술학회지:방사선기술과학
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• 제32권2호
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• pp.195-203
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• 2009

영상정합 기술은 두 개 이상의 영상을 서로 맞추어, 각각의 영상이 가지고 있는 단점을 보완하여, 새로운 정보를 획득하게 하는 기술이다. 본 논문은 의료 영상간의 2D 영상 정합을 통해 환자의 점진적 병세파악에 도움을 주는 것을 목적으로 하고 있다. 서로 다른 시점과 장비로부터 얻어진 CT와 PET/CT영상을 정합하기 위하여 정확한 해부학적 정보를 제공하는 CT영상간의 정합을 먼저 수행하고 이를 통하여 얻어진 기하학적 정합파라미터들을 PET 영상에 적용하여, 독립 CT영상 위에 PET영상을 중첩하였다. 정합작업을 위해 먼저 각각의 CT영상에 대해 전처리 작업을 실시하였고, 영상의 변형은 affine 좌표변환을 이용하였다. 정합할 영상간의 유사도 평가를 위해 mutual information을 이용하였으며, 빠르고 정확한 정합을 위하여 최적화 알고 리듬인 particle swarm optimization 방법을 이용하였다. 이를 통해 실제 환자의 독립 CT와 PET/CT영상을 이용하여 실험하였고, PET/CT의 영상에서 확인할 수 있었던 병소에 대한 해부학적 위치 정보가 영상정합 과정을 통해 독립 CT 영상에서도 동일한 위치에 표시됨을 확인하였다. 제안된 알고리듬은 PET/CT 뿐만 아니라 향후 도입될 SPECT/CT, MRI/PET 등 다중영상기기와 기존의 독립 CT 영상기기와의 정합에도 폭넓게 사용될 것으로 기대된다.

• 핵의학기술
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• 제16권2호
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• pp.68-80
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• 2012

감쇠 보정법과 산란 보정법은 정량적인 PET검사를 하기 위한 필수적인 방법이다. PET/CT에서는 PET에서 사용하는 소멸방사선과 CT의 X선이 같은 전리 방사선이기 때문에 측정에 의한 CT의 Hounsfield Units를 감쇠 계수로 전환해서 감쇠보정, 산란보정이 가능하다. 그러나 PET/MR에서 MR는 강한 자기장을 걸어 수소밀도와 조직의 이완률차이로 되돌아오는 변화로 신호를 획득하기 때문에 CT처럼 전환하는 것은 불가능하다. Ingenuity TF PET/MR장비는 soft tissue, lung, air로 3구역을 segment하여 MR 감쇠지도를 얻는다. 이에 신호획득원리가 완전히 상이한 PET/MR과 PET/CT에 대한 정량적 평가를 하고자 한다. Phantom study로 uniform cylinder phantom에 증류수 9293 ml와 $^{18}F$-FDG 199.8 MBq를 넣고 magnetic stirrer를 이용하여 균일하게 교반한 후 60 min부터 15분 간격으로 Ingenuity TF PET/MR, Gemini TF 64, Biograph Truepoint 40를 이용하여 각각 single-bed로 2 min씩으로 영상을 얻었다. phantom의 중심부분 10개의 slice에 대한 동일한 관심영역을 그려 SUVs를 측정하고 평균, 표준편차를 구하였다. 그리고 임상적용을 위한 평가로 $^{18}F$-FDG 섭취가 정상인 환자를 대상으로 90 sec/bed씩 Ingenuity TF PET/MR을 시행한 후 Gemini TF 64 PET/CT 검사를 실시하였다. 각각의 data에서 lung, liver, spleen, bone 위치에 동일한 관심영역을 그려 SUVs 최대값과 평균값을 측정하고, %Difference를 구하였다. 또한, PET 장비들 사이에서의 일치도를 평가하기 위해 Bland-Altman plot 분석을 하였다. Phantom study에서 3가지 장비에서 측정한 SUVs 최대값과 평균값은 Biograph Truepoint 40, Gemini TF 64, Ingenuity TF PET/MR 순으로 높은 것을 확인할 수 있었다. patients study에서는 MR과 CT로 감쇠 보정한 PET장비의 SUVs 최대값과 평균값이 서로 유의미한 차이가 없었다.(p<0.05) Lung에서 left middle lobe과 transverse bone을 제외하고는 MR로 감쇠 보정한 PET의 SUVs가 대체로 낮았다. Bland Altman Plot으로 분석한 결과 대부분의 항목에서 95% 신뢰구간의 일치한계선내에서 측정되었다. PET/CT에서는 time of flight 기능을 가진 PET이 SUVs가 낮게 측정되었다. PET/MR과 PET/CT에서 알아본 SUVs차이는 MR을 이용한 분할 감쇠 보정방법이 CT를 사용한 측정 감쇠보정방법보다 SUVs가 낮게 측정되었다. 이러한 다른 감쇠 보정법에 의한 SUVs의 차이는 임상적으로는 용인할 수준에 있었지만, 향후 PET/MR와 PET/CT의 정량적인 값을 비교 분석할 때 PET 장비들간의 특성은 고려할 필요가 있다.

• Korean Journal of Radiology
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• 제22권6호
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• pp.951-958
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• 2021

Objective: To evaluate the usefulness of virtual monochromatic images (VMIs) obtained using dual-layer dual-energy CT (DL-DECT) for evaluating brain tumors. Materials and Methods: This retrospective study included 32 patients with brain tumors who had undergone non-contrast head CT using DL-DECT. Among them, 15 had glioblastoma (GBM), 7 had malignant lymphoma, 5 had high-grade glioma other than GBM, 3 had low-grade glioma, and 2 had metastatic tumors. Conventional polychromatic images and VMIs (40-200 keV at 10 keV intervals) were generated. We compared CT attenuation, image noise, contrast, and contrast-to-noise ratio (CNR) between tumor and white matter (WM) or grey matter (GM) between VMIs showing the highest CNR (optimized VMI) and conventional CT images using the paired t test. Two radiologists subjectively assessed the contrast, margin, noise, artifact, and diagnostic confidence of optimized VMIs and conventional images on a 4-point scale. Results: The image noise of VMIs at all energy levels tested was significantly lower than that of conventional CT images (p < 0.05). The 40-keV VMIs yielded the best CNR. Furthermore, both contrast and CNR between the tumor and WM were significantly higher in the 40 keV images than in the conventional CT images (p < 0.001); however, the contrast and CNR between tumor and GM were not significantly different (p = 0.47 and p = 0.31, respectively). The subjective scores assigned to contrast, margin, and diagnostic confidence were significantly higher for 40 keV images than for conventional CT images (p < 0.01). Conclusion: In head CT for patients with brain tumors, compared with conventional CT images, 40 keV VMIs from DL-DECT yielded superior tumor contrast and diagnostic confidence, especially for brain tumors located in the WM.

• 한국지능시스템학회:학술대회논문집
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• 한국지능시스템학회 2008년도 춘계학술대회 학술발표회 논문집
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• pp.255-258
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• 2008

For rapidly increasing amount of medical images, it is difficult for radiologist to interpretate the medical images fastly and for sufficient time. We investigated whether liver CT image has good features to be analyzed by computer algorithm, We examed the CT images of liver tumors (Hepetocellular carcinomas; HCCs) and searched any potential morphologic characteristics to be analyzed by computer algorithms. On unenhanced CT, HCCs appeared hypodense After enhancement, most HCCs were hyperdense, and then. as a consequence of rapid washout, HCCS became hypodense compared with the liver parenchyma. Most CT images of HCCs showed synchronous phase-specific.morphologic features. We applied various edge detection filters to these images and some filters showed favorable performance in the detection of tile edge of liver and HCC. Therefore, theses features seems to be analyzed by computer algorithms effectively.Further studies may be warranted.

• Journal of Trauma and Injury
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• 제22권2호
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• pp.206-211
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• 2009

Purpose: Abdominal CT (computed tomography) is a principal diagnostic imaging modality for torso trauma at the Emergency Department (ED). When acute osseous pelvic injuries are detected by abdominal CT, additional three-dimensional (3D) reconstruction pelvic CT is often performed. We compared abdominal CT with pelvic CT to provide information about acute osseous pelvic injuries. Methods: A retrospective investigation of patients'electronic medical records during the five year period between January 1, 2004 and December 31, 2008 among Korean soldiers who underwent pelvic CT after abdominal CT at the ED was conducted. Axial images of abdominal CT were compared with axial images and 3D reconstruction images of pelvic CT. Results: Sixteen patients underwent subsequent pelvic CT after abdominal CT. Axial images of abdominal CT showed the same results in terms of fracture detection and classification when compared to axial images and 3D reconstruction images of pelvic CT. Pelvic CT (including 3D reconstruction images) followed by abdominal CT neither detected additional fracture nor changed the fracture type. Conclusion: This study has failed to show any superiority of pelvic CT (including 3D reconstruction images) over abdominal CT in detecting acute osseous pelvic injury. When 3D information is deemed be mandatory, 3D reconstructions of abdominal CT can be requested rather than obtaining an additional pelvic CT for 3D reconstruction.

• Asian Pacific Journal of Cancer Prevention
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• 제16권6호
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• pp.2521-2526
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• 2015

Objective: The purpose of this study was to evaluate computed tomography (CT) virtual non-contrast (VNC) spectral imaging for gastric carcinoma. Materials and Methods: Fifty-two patients with histologically proven gastric carcinomas underwent gemstone spectral imaging (GSI) including non-contrast and contrast-enhanced hepatic arterial, portal venous, and equilibrium phase acquisitions prior to surgery. VNC arterial phase (VNCa), VNC venous phase (VNCv), and VNC equilibrium phase (VNCe) images were obtained by subtracting iodine from iodine/water images. Images were analyzed with respect to image quality, gastric carcinoma-intragastric water contrast-to-noise ratio (CNR), gastric carcinoma-perigastric fat CNR, serosal invasion, and enlarged lymph nodes around the lesions. Results: Carcinoma-water CNR values were significantly higher in VNCa, VNCv, and VNCe images than in normal CT images (2.72, 2.60, 2.61, respectively, vs 2.35, $p{\leq}0.008$). Carcinoma-perigastric fat CNR values were significantly lower in VNCa, VNCv, and VNCe images than in normal CT images (7.63, 7.49, 7.32, respectively, vs 8.48, p< 0.001). There were no significant differences of carcinoma-water CNR and carcinoma-perigastric fat CNR among VNCa, VNCv, and VNCe images. There was no difference in the determination of invasion or enlarged lymph nodes between normal CT and VNCa images. Conclusions: VNC arterial phase images may be a surrogate for conventional non-contrast CT images in gastric carcinoma evaluation.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.279-280
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• 1998

A new algorithm is developed that can reduce the metal artifact on CT caused by pedicle screws. Metal artifact has been recognized as a major problem in precise reading of CT images. In particular, spine surgeons have been bothered with the artifact appearing on CT taken after pedicle screw insertion. To reduce the artifact, our new algorithm first finds the center line from CT images, and then overlays an exact size screw image on the CT. The exact screw is obtained from an actual design specifications of screw, and the CT images are processed to maximize bone margins while minimizing screw images through adjusting the window width and level. 실험 결과 단순한 Window W/L 조절로는 해결되지 않는군요. This algorithm provides spine surgeons with more accurate CT images and thus better interpretation of CT to ascertain the success or failure of pedicle screw insertion.

• 대한방사선치료학회지
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• 제12권1호
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• pp.20-25
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• 2000

The accuracy of the target localization was evaluated by conventional and spiral CT in stereotactic radiosurgerv. Conventional and spiral CT images were obtained with geometrical phantom, which was designed to produce exact three-dimensional coordinates of several objects within 0.1mm error range. Geometrical phantom was attached by BRW headframe, intermediate head ring, and CT localizer. Twentv-seven slices of conventional CT image were scanned at 3 mm slice thickness. Spiral CT images were scanned at 3 mm slice thickness from the pitch value 1 to 3, and twenty-seven slices of image were obtained per each the pitch value. These CT images were transferred to a treatment planning system(X-knife, Radionics) by ethernet, Three-dimensional coordinates of these images measured from the treatment planning system were compared to known values of geometrical phantom. The mean localization error of the target localization of conventional CT was 1.4mm. In case of spiral CT, the error of the target localization was within 1.6mm from the pitch value 1 to 1.3, but was more than 30mm above the pitch value 1.5. In conclusion, as the localization error of spiral CT was increased in high pitch value compared to conventional CT, the application of spiral CT will be with caution in stereotactic radiosurgery.