• 대한디지털의료영상학회논문지
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• 제15권1호
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• pp.33-38
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• 2013

Bone is so crucial anatomy for human body. Many researchers study deep into a subject about bone regeneration. There is no standard analysis for quantitative Neo-bone regeneration on calvarial defected model. Micro CT is so useful method to quantitative analysis of Neo-bone regeneration. This study was show that how to quantitative analysis of Neo-bone regeneration with ${\mu}-CT$ Micro CT was possible to quantitative analysis for Neo-bone regeneration on Calvarial defected model. futhermore Not only was Micro CT possible for qualitative analysis but quantitative analysis on the mouse calvarial model. This study will provide bone biology researchers with accurate quantitative analysis.

• Nuclear Medicine and Molecular Imaging
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• 제42권2호
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• pp.172-180
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• 2008

PET/CT fused image with anatomical and functional information have improved medical diagnosis and interpretation. This fusion has resulted in more precise localization and characterization of sites of radio-tracer uptake. However, a motion during whole-body imaging has been recognized as a source of image quality degradation and reduced the quantitative accuracy of PET/CT study. The respiratory motion problem is more challenging in combined PET/CT imaging. In combined PET/CT, CT is used to localize tumors and to correct for attenuation in the PET images. An accurate spatial registration of PET and CT image sets is a prerequisite for accurate diagnosis and SUV measurement. Correcting for the spatial mismatch caused by motion represents a particular challenge for the requisite registration accuracy as a result of differences in PET/CT image. This paper provides a brief summary of the materials and methods involved in multiple investigations of the correction for respiratory motion in PET/CT imaging, with the goal of improving image quality and quantitative accuracy.

• Imaging Science in Dentistry
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• 제44권3호
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• pp.177-183
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• 2014

Recent research in endodontics has highlighted the need for three-dimensional imaging in the clinical arena as well as in research. Three-dimensional imaging using computed tomography (CT) has been used in endodontics over the past decade. Three types of CT scans have been studied in endodontics, namely cone-beam CT, spiral CT, and peripheral quantitative CT. Contemporary endodontics places an emphasis on the use of cone-beam CT for an accurate diagnosis of parameters that cannot be visualized on a two-dimensional image. This review discusses the role of CT in endodontics, pertaining to its importance in the diagnosis of root canal anatomy, detection of periradicular lesions, diagnosis of trauma and resorption, presurgical assessment, and evaluation of the treatment outcome.

• Investigative Magnetic Resonance Imaging
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• 제25권2호
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• pp.109-117
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• 2021

Purpose: To investigate the reliability of CT and MRI for quantitative and qualitative analyses of lumbar paraspinal muscle fatty infiltration (PSFI) and correlation of PSFI with intervertebral disc pathology. Materials and Methods: Lumbar spine CT and MRI of 36 subjects were reviewed retrospectively. Two observers independently outlined lumbar paraspinal muscles at each mid-intervertebral disc level. Paraspinal muscles on CT and MRI were graded according to the Goutallier grading system (GGS). The area, mean value, and standard deviation (SD) of the Hounsfield unit (HU) were obtained. Intervertebral discs were assessed on axial image of T2WI at each level. Correlations between qualitative and quantitative data and intervertebral disc pathology, age, and sex were evaluated. Results: Inter- and intra-observer agreements for results of GGS on MRI were substantial (κ = 0.79) and moderate (κ = 0.59), respectively. Inter- and intra-observer agreements for results of GGS on CT were almost perfect (κ = 0.88) and substantial (κ = 0.66), respectively. Quantitative measurements of HU showed almost perfect inter- and intra-observer reliabilities (κ = 0.82 and κ = 0.99, respectively). There were statistically significant correlations between intervertebral disc pathology and PSFI at L1-2, L2-3, and L4-5 levels on MRI and at L1-2 and L3-4 levels on CT. Age showed significant correlation with results of GGS at all levels on CT and MRI. Conclusion: This study showed that GGS results and HU measurements could be useful for evaluating PSFI because they showed correlations with intervertebral disc pathology results at certain levels.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.506-508
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• 2002

As an advancement of medical imaging modalities and analyzing software with multi-function, active researches to acquire high contrast and high resolution image being done. In recently, development of medical imaging modalities like as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) is aiming to display anatomical structure more accuracy and faster. Thus, one of the important areas in CT today is the use of CT scanner for the quantitative evaluation of 3-D reconstruction images from 2-D tomographic images. In CT system, the effective slice thickness and the quality of 3-D reconstructed image will be influenced by imaging acquisition parameters (e.g. pitch and scan mode). In diagnosis and surgical planning, the accurate distance measurements of 3-D anatomical structures play an important role and the accuracy of distance measurements will depend on the acquisition parameters such as slice thickness, pitch, and scan mode. The skull phantom was scanned with SDCT for various acquisition parameters and acquisition slice thicknesses were 3 and 5 mm, and reconstruction intervals were 1, 2, and 3 mm to each pitch. 3-D visualizations and distance measurements were performed with PC based 3-D rendering and analyzing software. Results showed that the image quality and the measurement accuracy of 3-D SDCT images are independent to the reconstruction intervals and pitches.

• 대한방사성의약품학회지
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• 제1권2호
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• pp.130-136
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• 2015

We evaluate the influence of MR contrast agent on positron emission tomography (PET) image using phantom, animal and human studies. Phantom consisted of 15 solutions with the mixture of various concentrations of Gd-based MR contrast agent and fixed activity of [$^{18}F$]FDG. Animal study was performed using rabbit and two kinds of MR contrast agents. After injecting contrast agent, CT or MRI scanning was performed at 1, 2, 5, 10, and 20 minutes. PET image was obtained using clinical PET/CT scan, and attenuation correction was performed using the all CT images. The values of HU, PET activity and MRI intensity were obtained from ROIs in each phantom and organ regions. In clinical study, patients (n=20) with breast cancer underwent sequential acquisitions of early [$^{18}F$]FDG PET/CT, MRI and delayed PET/CT. In phantom study, as the concentration increased, the CT attenuation and PET activity also increased. However, there was no relationship between the PET activity and the concentration in the clinical dose range of contrast agent. In animal study, change of PET activity was not significant at all time point of CT scan both MR contrast agents. There was no significant change of HU between early and delayed CT, except for kidney. Early and delayed SUV in tumor and liver showed significant increase and decrease, respectively (P<0.05). Under the condition of most clinical study (< 0.2 mM), MR contrast agent did not influence on PET image quantitation.

• Nuclear Medicine and Molecular Imaging
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• 제42권1호
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• pp.1-7
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• 2008

PET allows non-invasive, quantitative and repetitive imaging of biological function in living animals. Small animal PET imaging with $[^{18}F]$FDG has been successfully applied to investigation of metabolism, receptor-ligand interactions, gene expression, adoptive cell therapy and somatic gene therapy. Experimental condition of animal handling impacts on the biodistribution of $[^{18}F]$FDG in small animal study. The small animal PET and CT images were registered using the hardware fiducial markers and small animal contour point. Tumor imaging in small animal with small animal $[^{18}F]$FDG PET should be considered fasting, warming, and isoflurane anesthesia level. Registered imaging with small animal PET and CT image could be useful for the detection of tumor. Small animal experimental condition of animal handling and registration method will be of most importance for small lesion detection of metastases tumor model.

• Imaging Science in Dentistry
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• 제31권2호
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• pp.85-91
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• 2001

Purpose: To evaluate the effect of the slice thickness and the size of region of interest (ROI) on CT number using quantitative CT phantom Materials and Methods: The phantom containing 150 mg/cc, 75 mg/cc and 0 mg/cc calcium hydroxyapatite was scanned with 1, 3, 5 and 10 mm slice thicknesses by single energy quantitative computed tomography (QCT). CT numbers were measured on center position of the phantom. Shape of ROI was circular and sizes were 1, 3, 5, 11, 16, 21, 26 and 33 mm². ANOVA and Tukey's multiple comparison method were performed for statistical comparison of CT numbers according to different slice thicknesses. Coefficient of variation of CT number measured in each size of ROI was evaluated in same slice thickness. Results : CT numbers had statistically significant difference according to slice thicknesses (p<0.05). As the slice thickness increased, CT number also increased. As the density of phantom became lower and the size of ROI became smaller, the coefficient of variation of CT number increased. When the size of ROI was more than 11 mm² in 1 mm slice thickness, 5 mm² in 3 mm slice thickness and 3 mm² in 5 mm slice thickness, the coefficient of variation became consistent. In 10 mm slice thickness, the size of ROI had little effect on the coefficient of variation. Conclusion: CT number had variation according to the slice thickness and the size of ROI although the object was homogeneous. The slice thickness and the size of ROI are critical factors in precision of the CT number measurements.

• 한국방사선학회논문지
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• 제16권3호
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• pp.295-302
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• 2022

희박뷰 전산화단층촬영(computed tomography; CT) 영상화 기술은 피폭 방사선량을 감소시킬 수 있을 뿐만 아니라 획득한 투영상의 균일성을 유지하고 잡음을 감소시킬 수 있는 장점이 있다. 하지만 재구성 영상 내 인공물 발생으로 인하여 화질 및 피사체 구조가 왜곡되는 단점이 있다. 본 연구에서는 희박뷰 CT 영상의 인공물 감소를 위해 wavelet 변환과 잔차 학습(residual learning)을 적용한 콘볼루션 신경망(convolutional neural network; CNN) 기반 영상화 모델을 개발하고, 개발한 모델을 통한 희박뷰 CT 영상의 인공물 감소 정도를 정량적으로 분석하였다. CNN은 wavelet 변환 층, 콘볼루션 층 및 역 wavelet 변환 층으로 구성하였으며, 희박뷰 CT 영상과 잔차 영상을 각각 입출력 영상으로 설정하여 영상화 모델 학습을 진행하였다. 영상화 모델 학습을 위해 평균제곱오차(mean squared error; MSE)를 손실함수로, Adam 함수를 최적화 함수로 사용하였다. 학습된 모델을 통해 입력 희박뷰 CT 영상에 대한 예측 잔차 영상을 획득하고, 두 영상간의 감산을 통해 최종 결과 영상을 획득하였다. 또한 최종 결과 영상에 대한 시각적 특성, 최대신호대잡음비(peak signal-to- noise ratio; PSNR) 및 구조적유사성지수(structural similarity; SSIM)를 측정하였다. 연구결과 본 연구에서 개발한 영상화 모델을 통해 희박뷰 CT 영상의 인공물이 효과적으로 제거되며, 공간분해능이 향상되는 결과를 확인하였다. 또한 wavelet 변환과 잔차 학습을 미적용한 영상화 모델에 비해 본 연구에서 개발한 영상화 모델은 결과 영상의 PSNR 및 SSIM을 각각 8.18% 및 19.71% 향상시킬 수 있음을 확인하였다. 따라서 본 연구에서 개발한 영상화 모델을 이용하여 희박뷰 CT 영상의 인공물 제거는 물론 공간분해능 향상 및 정량적 정확도 향상 효과를 획득할 수 있다.

• 한국임상수의학회지
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• 제25권3호
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• pp.176-181
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• 2008

Fluid accumulation within the tympanic bulla is an important diagnostic indicator of canine otitis media although its identification can be a challenge using currently available imaging techniques. The purpose of this study was to compare radiography, computed tomography (CT) and magnetic resonance imaging (MRI) in the identification of fluid accumulation within canine tympanic bulla. Unilateral tympanic bulla in 10 beagles were experimentally filled with blood or saline. Quantitative analysis of CT images were obtained by using Hounsfield unit (HU). MR signal intensity was obtained by using region of interesting (ROI) and compared with those of gray matter. On the CT image, the presence of blood or saline produced a fluid opacity occupying the tympanic bulla. On the MR image, the appearance of blood in the tympanic bulla was isointense in T1-weighted images and hyperintense in T2-weighted images. However, the appearance of saline in the tympanic bulla was hypointense in T1-weighted images and hyperintense in T2-weighted images. This study suggest that CT and MR imaging are useful methods for detection and differentiation of fluid in canine tympanic bulla.