• Korean Journal of Radiology
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• 제20권4호
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• pp.599-608
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• 2019

Objective: To evaluate the effectiveness of computed tomography (CT) Hounsfield unit histogram analysis (HUHA) in postoperative pancreatic fistula (PF) prediction. Materials and Methods: Fifty-four patients (33 males and 21 females; mean age, 65.6 years; age range, 37-89 years) who had undergone preoperative CT and pancreaticoduodenectomy were included in this retrospective study. Two radiologists measured mean CT Hounsfield unit (CTHU) values by drawing regions of interest (ROIs) at the level of the pancreaticojejunostomy site on preoperative pre-contrast images. The HUHA values were arbitrarily divided into three categories, comprising HUHA-A ≤ 0 HU, 0 HU < HUHA-B < 30 HU, and HUHA-C ≥ 30 HU. Each HUHA value within the ROI was calculated as a percentage of the entire area using commercial 3-dimensional analysis software. Pancreas texture was evaluated as soft or hard by manual palpation. Results: Fifteen patients (27.8%) had clinically relevant PFs. The PF group had significantly higher HUHA-A (p < 0.01) and significantly lower mean CTHU (p < 0.01) values than those of the non-PF group. The HUHA-A value had a moderately strong correlation with PF occurrence (r = 0.60, p < 0.01), whereas the mean CTHU had a weak negative correlation with PF occurrence (r = -0.27, p < 0.01). The HUHA-A and mean CTHU areas under the curve (AUCs) for predicting PF occurrence were 0.86 and 0.65, respectively, with significant difference (p < 0.01). The HUHA-A and mean CTHU AUCs for predicting pancreatic softness were 0.86 and 0.64, respectively, with significant difference (p < 0.01). Conclusion: The HUHA-A values on preoperative pre-contrast CT images demonstrate a strong correlation with PF occurrence.

• Nuclear Engineering and Technology
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• 제56권9호
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• pp.3758-3763
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• 2024

The current study aimed to evaluate the suitability of polyester resin as an alternative material to polymethyl methacrylate (PMMA) for computed tomography (CT) dosimetry phantoms using the GEANT4/GATE Monte Carlo simulation platform. Cylindrical phantoms (32 cm diameter) constructed of polyester resin and PMMA were simulated and compared in terms of atomic composition, effective atomic number, electron density, mass density, and photon interaction mechanisms. Weighted CT dose index (CTDIw) values were calculated for each phantom at 80, 110, and 130 kVp tube voltages based on measurements of CTDI_100,c and CTDI_100,p. Results demonstrated that the physical properties of polyester closely matched those of PMMA, and the polyester phantom displayed equivalent dosimetric behavior to the PMMA phantom at all tube voltages tested. CTDIw values from the polyester phantom were within 1.4 % of the PMMA phantom across all tube voltages. Conversion coefficients were derived to equate polyester CTDIw values to PMMA dose equivalents. This study found that a polyester resin phantom exhibited radiation dosimetry commensurate with the standard PMMA phantom for CT dose assessment. Consequently, polyester resin represents a viable substitute material when PMMA is unavailable for construction of CT dosimetry phantoms.

• 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.

• International Journal of CAD/CAM
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• 제6권1호
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• pp.81-87
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• 2006

This paper describes a method for extracting surfaces from multi-material CT (Computed Tomography) data. Most contouring methods such as Marching Cubes algorithm assume that CT data are composed of only two materials. Some extended methods such as [3, 6] can extract surfaces from the multi-material (non-manifold) implicit representation. However, these methods are not directly applicable to CT data that are composed of three or more materials. There are two major problems that arise from fundamentals of CT. The first problem is that we have to use n(n-1)/2 threshold values for CT data contains n materials and select appropriately one threshold value for each boundary area. The second is that we cannot reconstruct only from CT data in which area three or more materials are adjacent each other. In this paper, we propose a method to solve the problems by using image analysis and demonstrate the effectiveness of the method with application examples construct polygon models from CT data of machine parts.

• Archives of Plastic Surgery
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• 제35권5호
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• pp.495-500
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• 2008

Purpose: Adequate tissue oxygenation is considered as an essential factor for wound healing. In the non-diabetic population, an uncompromised macrocirculation generally leads to adequate tissue oxygenation. On the contrary, the macrocirculation in diabetic patients may not correlate with tissue oxygenation because of structural changes in the capillary basement membrane. Nevertheless, many medical professionals in Korea rely on macrocirculation evaluation when predicting wound healing potential of the diabetic ulcers. The purpose of this study is to compare reliability of two common macrocirculation assessment methods, Doppler probing and CT angiography, on tissue oxygenation in diabetic foot patients. Methods: Doppler and CT angiography scores were given according to the patency of the anterior and posterior tibial arteries. Tissue oxygenation was measured by transcutaneous partial oxygen tension($TcpO_2$). Doppler and CT angiography scores were statistically analyzed against $TcpO_2$ values. Sixty-eight diabetic foot ulcer patients were included in this study. Results: The test was carried out on Doppler score and $TcpO_2$ variables displayed a p-value of 0.0202, and concluded that the two variables were statistically dependent. The test used to determine for linear trends between Doppler scores and $TcpO_2$ variables displayed a p-value of 0.0149, displaying statistical linear trend between the two variables. On the contrary, the tests between CT angiography scores and $TcpO_2$ variables showed p-values of 0.1242 and 0.6590, that means no correlation between CT angiography and $TcpO_2$ scores. Conclusion: Doppler probing is more reliable than CT angiography in predicting tissue oxygenation of diabetic foot ulcers.

• Imaging Science in Dentistry
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• 제37권1호
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• pp.27-33
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• 2007

Purpose : The research was done to investigate the effectiveness of 2D bony morphometry and microstructure of micro-computed tomography (micro-CT) on the osteoporotic bony change. We performed the bone morphometric analysis of proximal femur in ovariectomized rabbits with BMD and micro-CT examination. Materials and Methods : Twenty-one female (Newzealand, about 16 weeks old, 2.9-3.4kg) rabbits were used. Three rabbits were sacrificed on the day when experiment began (Baseline). The remaining 18 rabbits were divided into two groups. One group was ovariectomized bilaterally (OVX) and the other animals were subjected to sham operation (Sham). Bone specimens were obtained from the right and left femur of sacrificed rabbits. At intervals of 1, 2, 3, 5, 6 months respectively, BMD tests were performed on the proximal femur by using PIXlmus 2 (GE Lunar Co. USA), 2-dimensional bone morphometric analysis by custome computer program and 2D/3D bone structure analysis by micro-CT (Skyscan 1072, Antwerpen, Belgium). Statistical analysis was carried out for the correlation between bone morphometry, micro-CT and BMD Result : BV/TV, Tb.Th, Tb.N of micro-CT parameters showed higher values in sham group than OVX group. N.Nd/Ar.RI, N.NdNd, N.NdTm, N. TmTm, PmB/Ar.RI, 3-D BoxSlope of 2D morphometric parameters showed higher values in Sham group than OVX group. The micro-CT parameters of Tb.Sp, Tb.N were statistically significant correlated with BMD respectively. Several 2D morphometric parameters were statistically significant correlated with BMD respectively. Conclusion : Several parameters of 2D bony morphometry and micro-CT showed effective aspects on the osteoporotic bony change.

• 한국방사선학회논문지
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• 제15권2호
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• pp.117-123
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• 2021

본 논문에서는 흉부 저선량 CT와 복부 비조영 CT에서 선량기록을 바탕으로 환자선량에 영향을 줄 수 있는 요인과 상관관계를 확인하여 실질적인 선량 감소 방안의 근거를 마련하고자 하였다. 흉부 저선량 CT와 복부 비조영 CT 검사 시 불필요하게 피폭이 발생하는 원인을 찾기 위해 7가지 요인(나이, 성별, 키, 몸무게, BMI, 환자 상태 (입원, 외래), dose modulation 활성화 유무)과 CT 선량과의 상관관계를 확인하였다. 상관관계 확인을 위해 사용된 통계기법으로는 로지스틱 회귀분석을 사용하였다. 흉부 저선량 CT 검사에서는 키가 클수록, BMI 가 높을수록, dose modulation을 비활성화한 경우에 진단참고수준 (diagnostic reference levels, DRL) 기준치의 초과 위험률이 낮아졌다 (odds ration<1; p<0.05). 또한 여성의 경우와 몸무게가 클수록 DRL 기준치의 초과 위험률이 높아졌다 (odds ration>1; p<0.05). 복부 비조영 CT 검사에서는 몸무게가 클수록, dose modulation을 비활성화한 경우에 DRL 기준치의 초과 위험률이 낮아졌다 (odds ration<1; p<0.05). 이처럼 방사선 피폭에 영향을 주는 다양한 요인에 대한 연구를 수행하여 환자 선량과의 연관성을 찾고 이에 따른 선량을 낮추는 노력이 필요할 것으로 사료된다.

• Korean Journal of Radiology
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• 제22권12호
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• pp.1964-1973
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• 2021

Objective: To investigate the diagnostic performance of CT fractional flow reserve (CT-FFR) for myocardial bridging-related ischemia using dynamic CT myocardial perfusion imaging (CT-MPI) as a reference standard. Materials and Methods: Dynamic CT-MPI and coronary CT angiography (CCTA) data obtained from 498 symptomatic patients were retrospectively reviewed. Seventy-five patients (mean age ± standard deviation, 62.7 ± 13.2 years; 48 males) who showed myocardial bridging in the left anterior descending artery without concomitant obstructive stenosis on the imaging were included. The change in CT-FFR across myocardial bridging (ΔCT-FFR, defined as the difference in CT-FFR values between the proximal and distal ends of the myocardial bridging) in different cardiac phases, as well as other anatomical parameters, were measured to evaluate their performance for diagnosing myocardial bridging-related myocardial ischemia using dynamic CT-MPI as the reference standard (myocardial blood flow < 100 mL/100 mL/min or myocardial blood flow ratio ≤ 0.8). Results: ΔCT-FFR_systolic (ΔCT-FFR calculated in the best systolic phase) was higher in patients with vs. without myocardial bridging-related myocardial ischemia (median [interquartile range], 0.12 [0.08-0.17] vs. 0.04 [0.01-0.07], p < 0.001), while CT-FFR_systolic (CT-FFR distal to the myocardial bridging calculated in the best systolic phase) was lower (0.85 [0.81-0.89] vs. 0.91 [0.88-0.96], p = 0.043). In contrast, ΔCT-FFR_diastolic (ΔCT-FFR calculated in the best diastolic phase) and CT-FFR_diastolic (CT-FFR distal to the myocardial bridging calculated in the best diastolic phase) did not differ significantly. Receiver operating characteristic curve analysis showed that ΔCT-FFR_systolic had largest area under the curve (0.822; 95% confidence interval, 0.717-0.901) for identifying myocardial bridging-related ischemia. ΔCT-FFR_systolic had the highest sensitivity (91.7%) and negative predictive value (NPV) (97.8%). ΔCT-FFR_diastolic had the highest specificity (85.7%) for diagnosing myocardial bridging-related ischemia. The positive predictive values of all CT-related parameters were low. Conclusion: ΔCT-FFR_systolic reliably excluded myocardial bridging-related ischemia with high sensitivity and NPV. Myocardial bridging showing positive CT-FFR results requires further evaluation.

• 한국의학물리학회지:의학물리
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• 제21권3호
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• pp.246-252
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• 2010

환자가 두부, 흉부, 복부 MDCT 검사에서 피폭되는 선량을 평가하였다. 선량의 지표는 CTDIvol, DLP, 유효선량을 평가하여 환자의 체중과 선량과의 상관관계를 분석하였다. CT 검사에서 검사 조건을 동일하게 하여 연속적으로 두부(520명), 흉부(531명), 복부(724명) 환자를 대상으로 하였다. CTDIvol과 DLP 평균선량은 두부검사에서 CTDIvol (48.6 mGy), DLP (1,604 $mGy{\cdot}cm$), 흉부검사에서 CTDIvol (6.9 mGy), DLP (250 $mGy{\cdot}cm$), 복부는 CTDIvol (10.5 mGy), DLP (575 $mGy{\cdot}cm$), 유효선량은 두부, 흉부, 복부에서 3.6, 4.2, 8.6 mSv로 분석되었다. 환자의 체중과 선량과의 상관분석에서 두부, 흉부, 복부에서, 두부는 상관관계가가 보이지 않았고, 흉부는 CTDIvol ($r^2$=0.62), DLP ($r^2$=0.694), 복부는 CTDIvol ($r^2$=0.691), DLP ($r^2$=0.741)와 양의 상관관계를 나타내냈다. 검사에 따른 체중과의 상관관계를 이해하고 검사 하면 방사선 피폭에 의한 선량을 평가하고 관리하는데 기여 할 수 있을 것이다.

• 한국방사선학회논문지
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• 제17권6호
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• pp.843-849
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• 2023

본 연구는 임플란트 시술한 환자에 대한 두경부 CT 영상을 4개의 알고리즘(Standard, Soft, Bone, Detail)을 재구성하여 Noise, SNR, CNR 측정값을 정량적으로 분석한 후 최적의 알고리즘을 알아보고자 하였다. 분석방법으로는 Image J 프로그램을 이용하여 재구성한 영상에 관심영역(Region of interest)을 통하여 픽셀값을 계산하였다. Noise, SNR, CNR은 측정부위를 영상에서 인두, 깨물근, 귀밑샘이 있는 지점에 관심영역을 측정하고 mean값과 SD값을 구하였다. SNR과 CNR의 값은 주어진 식에 의거하여 산출하였다. 결과적으로 Standard 알고리즘에서 노이즈는 가장 낮게 나타났으며 SNR 또한 가장 높게 나타났다. CNR은 Soft 알고리즘에서 가장 높게 나타났으나 Standard 알고리즘과는 별 차이가 없는 것으로 나타났다. 따라서 두경부 CT검사에서 구강내 임플란트 착용한 환자 검사에서 Standard 알고리즘이 최적의 알고리즘이라고 사료되며 이 연구의 자료가 두경부 CT검사에서 영상 평가하는데 기초자료로 사용되기를 바라며 다양한 알고리즘 변화로 영상의 질을 더 높일 수 있는 계기가 될 것으로 판단된다.