• 대한의용생체공학회:의공학회지
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• 제26권5호
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• pp.295-300
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• 2005

We introduce an x-ray micro tomography system capable of high resolution imaging of a local region inside a small animal. By combining two kinds of projection data, one from a full field-of-view (FOV) scan of the whole body and the other from a limited FOV scan of the region of interest, we have obtained zoomed-in images of the region of interest without any contrast a nomalies. We have integrated a micro tomography system using a micro-focus x-ray source, a $1248\times1248$ flat-panel x-ray detector, and a precision scan mechanism. Using the cross-sectional images taken with the zoom-in micro tomography system, we measured trabecular thicknesses of femur bones in postmortem rats. To compensate the limited spatial resolution in the zoom-in micro tomography images, we used the fuzzy distance transform for the calculation of the trabecular thickness. To validate the trabecular thickness measurement with the zoom-in micro tomography images, we compared the measurement results with the ones obtained from the conventional micro tomography images of the extracted bone samples.

• 대한의용생체공학회:의공학회지
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• 제27권4호
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• pp.189-196
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• 2006

Micro computed tomography (micro-CT) has been used for in vivo animal study owing to its noninvasive and high spatial resolution capability. However, the sizes of existing detectors for micro-CT systems are too small to obtain whole-body images of a small animal object with $\sim$10 micron resolution and a part of its bones or other organs should be extracted. So, we have introduced the zoom-in micro-tomography technique which can obtain high-resolution images of a local region of an live animal object without extracting samples. In order to verify our zoom-in technique, we performed in vivo animal bone study. We prepared some SD (Sprague-Dawley) rats for making osteoporosis models. They were divided into control and ovariectomized groups. Again, the ovariectomized group is divided into two groups fed with normal food and with calcium-free food. And we took 3D tomographic images of their femurs with 20 micron resolution using our zoom-in tomography technique and observed the bone changes for 12 weeks. We selected ROI (region of interest) of a femur image and applied 2D FDT (fuzzy distance transform) to measure the trabecular bone thickness. The measured results showed obvious bone changes and big differences between control and ovariectomized groups. However, we found that the reliability of the measurement depended on the selection of ROI in a bone image for thickness calculation. So, we extended the method to 3D FDT technique. We selected 3D VOI (volume of interest) in the obtained 3D tomographic images and applied 3D FDT algorithm. The results showed that the 3D technique could give more accurate and reliable measurement.

• 대한의용생체공학회:의공학회지
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• 제29권2호
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• pp.107-113
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• 2008

We introduce a rotating-gantry-based x-ray micro-tomography system to be used for small animal imaging studies. It has the zoom-in imaging capability for high resolution imaging of a local region inside the animal subject without any contrast anomalies arising from truncation of the projection data. With the sliding mechanism mounted on the rotating gantry holding the x-ray source and the x-ray detector, we can control the magnification ratio of the x-ray projection data. By combining the projection data from the large field of view (FOV) scan of the whole animal subject and the projection data from the small FOV scan of the region of interest, we can obtain artifact-free zoomed-in images of the region of interest. For the acquisition of x-ray projection data, we use a $1248{\times}1248$ flat-panel x-ray detector with the pixel pitch of 100 mm. It has been experimentally found that the developed system has the spatial resolution of up to 121p/mm when the highest magnification ratio of 5:1 is applied to the zoom-in imaging. We present some in vivo rat femur images to demonstrate utility of the developed system for small animal imaging.

• Imaging Science in Dentistry
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• 제42권1호
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• pp.19-24
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• 2012

Purpose : Field of view and voxel resolution of cone beam computed tomography (CBCT) might affect the diagnostic capability. This study was performed to compare between the standard and HiRes zoom modes in the diagnosis of external root resorption (ERR) using CBCT. Materials and Methods : Sixty three small cavities (0.25 mm depth and 0.5 mm diameter) were simulated on the buccal, lingual, and proximal surfaces at three different levels of 16 roots of teeth. After covering the root with nail varnish, the roots were inserted in the sockets and the model was placed in a water-containing lacuna. CBCT scans were taken in both standard and HiRes zoom modes using NewTom VG (QR srl Company, Verona, Italy). Then, an observer assessed the images to determine the presence or absence of the cavities. This process was repeated by increasing the size and depth of cavities to 0.5 mm depth and 1 mm diameter. Data were analyzed by McNemar test. The sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio in evaluation of the simulated cavities were calculated. Results : There was a significant difference between the two imaging modes in diagnosing the shallow cavities (p=0.02).The sensitivity of the standard zoom in detecting the shallow cavities was lower than that of the HiRes zoom. The likelihood ratio of the HiRes zoom was higher in the diagnosis of both cavity types. Conclusion : This study suggested that a smaller voxel size in the HiRes zoom mode of CBCT is preferred for diagnosis of ERR.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.95-101
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• 2007

Recently, small-animal imaging technology has been rapidly developed for longitudinal screening of laboratory animals such as mice and rats. One of newly developed imaging modalities for small animals is an x-ray micro-CT (computed tomography). We have developed two types of x-ray micro-CT systems for small animal imaging. Both systems use flat-panel x-ray detectors and micro-focus x-ray sources to obtain high spatial resolution of $10{\mu}m$. In spite of the relatively large field-of-view (FOV) of flat-panel detectors, the spatial resolution in the whole-body imaging of rats should be sacrificed down to the order of $100{\mu}m$ due to the limited number of x-ray detector pixels. Though the spatial resolution of cone-beam CTs can be improved by moving an object toward an x-ray source, the FOV should be reduced and the object size is also limited. To overcome the limitation of the object size and resolution, we introduce zoom-in micro-tomography for high-resolution imaging of a local region-of-interest (ROI) inside a large object. For zoom-in imaging, we use two kinds of projection data in combination, one from a full FOV scan of the whole object and the other from a limited FOV scan of the ROI. Both of our micro-CT systems have zoom-in micro-tomography capability. One of both is a micro-CT system with a fixed gantry mounted with an x-ray source and a detector. An imaged object is laid on a rotating table between a source and a detector. The other micro-CT system has a rotating gantry with a fixed object table, which makes whole scans without rotating an object. In this paper, we report the results of in vivo small animal study using the developed micro-CTs.

• Imaging Science in Dentistry
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• 제43권3호
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• pp.171-177
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• 2013

Purpose: The purpose of this study was to compare the efficacy of two imaging modes in a cone beam computed tomography (CBCT) system in detecting root fracture in endodontically-treated teeth with fiber posts or screw posts by selecting two fields of view. Materials and Methods: In this study, 78 endodontically-treated single canal premolars were included. A post space was created in all of them. Then the teeth were randomly set in one of 6 artificial dental arches. In 39 of the 78 teeth set in the 6 dental arches, a root fracture was intentionally created. Next, a fiber post and a screw post were cemented into 26 teeth having equal the root fractures. High resolution (HiRes) and standard zoom images were provided by a CBCT device. Upon considering the reconstructed images, two observers in agreement with each other confirmed the presence or absence of root fracture. A McNemar test was used for comparing the results of the two modes. Results: The frequency of making a correct diagnosis using the HiRes zoom imaging mode was 71.8% and in standard zoom was 59%. The overall sensitivity and specificity in diagnosing root fracture in the HiRes mode were 71.79% and 46.15% and in the standard zoom modes were 58.97% and 33.33%, respectively. Conclusion: There were no significant differences between the diagnostic values of the two imaging modes used in the diagnosis of root fracture or in the presence of root canal restorations. In both modes, the most true-positive results were reported in the post space group.

• Journal of Oral Medicine and Pain
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• 제41권3호
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• pp.85-90
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• 2016

Purpose: The aim of this study was to develop an automated software to extract tooth and pulpal area from sectional cone-beam computed tomography (CBCT) images, which can guarantee more reproducible, objective and time-saving way to measure pulp/tooth volume ratio. Methods: The software program was developed using MATLAB (MathWorks). To determine the optimal threshold for the region of interest (ROI) extraction, user interface to adjust the threshold for extraction algorithm was added. Default threshold was determined after several trials to make the outline of extracted ROI fitting to the tooth and pulpal outlines. To test the effect of starting point location selected initially in the pulpal area on the final result, pulp/tooth volume ratio was calculated 5 times with different 5 starting points. Results: Navigation interface is composed of image loading, zoom-in, zoom-out, and move tool. ROI extraction process can be shown by check in the option box. Default threshold is adjusted for the extracted tooth area to cover whole tooth including dentin, cementum, and enamel. Of course, the result can be corrected, if necessary, by the examiner as well as by changing the threshold of density of hard tissue. Extracted tooth and pulp area are reconstructed three-dimensional (3D) and pulp/tooth volume ratio is calculated by voxel counting on reconstructed model. The difference between the pulp/tooth volume ratio results from the 5 different extraction starting points was not significant. Conclusions: In further studies based on a large-scale sample, the most proper threshold to present the most significant relationship between age and pulp/tooth volume ratio and the tooth correlated with age the most will be explored. If the software can be improved to use whole CBCT data set rather than just sectional images and to detect pulp canal in the original 3D images generated by CBCT software itself, it will be more promising in practical uses.

• Journal of Chest Surgery
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• 제37권7호
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• pp.570-577
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• 2004

관상동맥우회술 후 이식편의 조기 열림을 판정하기 위한 CT 조영술은 비침습적이고 간단하며 안전한 방법으로 알려져 있다. 저자들은 관상동백 우회술 환자들에서 수술 후 퇴원 전에 CT 조영술을 시행하여 이식편의 조기 열림의 판정에 대한 여부와 영상에 미치는 인자들을 조사하였다. 대상 및 방법: 관상동맥 우회술을 받은 50예에서 수술 후 퇴원 전에 4개의 검출기를 가진 CT기로 조영술을 시행하고 내흉동맥 이식편(50편), 요골동맥편(18편), 대퇴정맥편(56편)의 조영상해로 이식편의 열림을 조사하고 이식편의 조영상태와 문합혈관의 직경, 부행혈류 및 협착정도와의 관계를 분석하였다. 결과: 좌관상동맥계에 문합되는 정맥편(24편, 32문합부)은 모두 잘 조영되었으나, 우관상동백계에 문합된 정맥편(30편, 35문합부) 중 3편 (4.7%)은 CT 조영술에서 조영되지 않았고 대퇴동맥을 통한 침습적인 관상동맥 조영술에서도 폐쇄된 소견을 보였다. 내흉동맥편 중 39편(78%)은 CT 조영술에서 잘 조영되었고 8편(16%)은 일부 좁아지거나 끊기는 불완전한 조영을 보였으며 3편(6%)은 조영되지 않았으나 동맥을 통한 침습적인 관상동맥 조영술에서는 모두 정상적인 열림 소견을 보였다. 결론: 관상동맥조영술 후 CT 조영술에서 조영되지 않는 정맥편은 페쇄를 의미하나, CT조영술에서 조영되지 않는 동맥편은 폐쇄가 아닌 관상동맥과 이식편 사이의 상경혈류 때문에 일어날 수 있으므로 조영이 안 되는 동맥편의 열림을 확인하기 위해서는 침습적인 관상동맥조영술이 필요할 것으로 생각된다.