• 한국방사선학회논문지
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• 제12권7호
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• pp.879-886
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• 2018

3-dimensional(D) 프린터는 컴퓨터로 모델링 한 데이터를 바탕으로 3차원의 입체 물체를 출력할 수 있는 장비이다. 이러한 특징을 방사선과학 분야와 융합하여, CT 데이터를 이용한 뼈 모형 X선 팬텀제작 등에 활용되고 있다. 본 연구는 기존의 Pelvis팬텀을 CT 스캔하고 얻어진 데이터로 Fused Filament Fabrication(FFF) 3D 프린터의 소재인 PLA, Wood, XT-CF20, Glow fill, Steel 필라멘트를 이용하여, 뼈 모형 팬텀을 제작하였다. 기존의 Pelvis 팬텀과 3D 프린터로 제작된 5가지 재질의 팬텀을 동일한 조건으로 CT 스캔 하고 얻어진 영상에서 Hounsfield Unit(HU)을 측정하였으며, 진단용X선 발생장치를 이용하여 SI, SNR을 측정하여 각 팬텀을 비교 분석하였다. 그 결과 사지 X선 검사 조건 내에서 X선 팬텀은 glow fill 필라멘트가 가장 적합하다는 것을 알 수 있었다. 본 연구의 기반으로 필라멘트의 특성들을 알 수 있었으며, X선 팬텀 제작에 대한 실용성을 확인하였다.

• 한국방사선학회논문지
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• 제17권2호
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• pp.207-213
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• 2023

전산화단층촬영(computed tomography, CT) 영상은 양성자 브레그 피크 위치 추정 및 치료 계획 시뮬레이션의 기초로 사용된다. Hounsfield Unit(HU) 기반의 양성자 저지능비(stopping pwer ratio, SPR) 예측 과정에서 환자의 밀도와 원소 구성의 작은 차이로 양성자 빔의 경로를 따라 브레그 피크 위치의 불확실성이 발생한다. 본 연구에서는 브레그 피크 위치 예측 불확실성 감소를 위하여 이중에너지 전산화단층촬영 영상 기반의 양성자 저지능비 예측 정확도의 잠재력을 연구를 하였다. 양성자 빔의 저지능비를 추정하기 위해 전산화단층촬영 시스템(Somatom Definition AS, Siemens Health Care, Forchheim, Germany)을 이용하여 전자밀도팬텀(CIRS Model 062M electron density phantom, CIRS Inc., Norfolk, VA, USA)의 단일에너지 및 이중에너지 영상을 획득하였다. 이를 검증하기 위해 미국 국립 표준기술 연구소(National Institute of Standards and Technology, NIST)에서 제공하는 표준 데이터를 통하여 추정한 실제 저지능비와 비교하였다. 그 결과 잡음이 제거된 이중에너지 영상 기반 방법을 통한 양성자 빔의 저지능비 예측에서 정확도 개선 가능성을 확인할 수 있었으며, 인체의 다양한 밀도와 원소 구성을 가진 대체물을 더욱 다양하게 제작하여 저지능비를 예측 할 경우 더욱 향상된 양성자의 브레그 피크 위치 예측이 가능할 것으로 사료된다.

• Journal of Korean Neurosurgical Society
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• 제56권2호
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• pp.86-90
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• 2014

Objective : The spot sign is related with the risk of hematoma expansion in spontaneous intracerebral hemorrhage (ICH). However, not all spot sign positive patients undergo hematoma expansion. Thus, the present study investigates the specific factors enhancing the spot sign positivity in predicting hematoma expansion. Methods : We retrospectively studied 316 consecutive patients who presented between March 2009 to March 2011 with primary ICH and whose initial computed tomography brain angiography (CTA) was performed at our Emergency Department. Of these patients, 47 primary ICH patients presented spot signs in their CTA. We classified these 47 patients into two groups based on the presence of hematoma expansion then analyzed them with the following factors : gender, age, initial systolic blood pressure, history of anti-platelet therapy, volume and location of hematoma, time interval from symptom onset to initial CTA, spot sign number, axial dimension, and Hounsfield Unit (HU) of spot signs. Results : Of the 47 spot sign positive patients, hematoma expansion occurred in 26 patients (55.3%) while the remaining 21 (44.7%) showed no expansion. The time intervals from symptom onset to initial CTA were $2.42{\pm}1.24$ hours and $3.69{\pm}2.57$ hours for expansion and no expansion, respectively (p=0.031). The HU of spot signs were $192.12{\pm}45.97$ and $151.10{\pm}25.14$ for expansion and no expansion, respectively (p=0.001). Conclusions : The conditions of shorter time from symptom onset to initial CTA and higher HU of spot signs are the emphasizing factors for predicting hematoma expansion in spot sign positive patients.

• 한국임상수의학회지
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• 제37권1호
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• pp.28-33
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• 2020

The aims of this study were to obtain the normal ranges of enhancement parameters for salivary gland in dynamic CT and to investigate the effects of fasting time on contrast enhancement in clinically normal beagle dogs. With five healthy beagle dogs, dynamic CT examination was performed according to fasting times (as fasting times, 12hours, 0 min, 20 min, 40 min, 1 hours, 6 hours, 24 hours). In normal beagles with 12hours fasting, enhancement parameters through the preliminary study were as follows: ImaxA - 472 .49 ± 19.01 HU; ImaxS - 138.95 ± 6.2 5 HU; TmaxA - 25.8 ± 1.79 sec; TmaxS - 69.0 ± 23.11 sec; Teq - 80.5 ± 6.61 sec; T-Aeq - 54.5 ± 5.51 sec (Imax - peak enhancement; Tmax - time to peak enhancement; Teq - time to equilibrium phase; T-Aeq - time between peak enhancement in the common carotid artery and onset of the equilibrium phase; A - common carotid; S - submandibular gland; HU - Hounsfield unit). Additionally, ImaxA and ImaxS were significantly increased in 40 min after eating. Because these results associated with postprandial hemodynamic changes can make the diagnosis of salivary gland diseases more difficult, sufficient fasting time is important for accurate diagnosis.

• 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.

• 대한방사선기술학회지:방사선기술과학
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• 제44권3호
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• pp.211-218
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• 2021

The purpose of this study was to investigate the effect of sex and menopausal age on the thickness and density of squamous portion of the temporal bone as the membranous bone. Patients who visited a general hospital in Chungnam and had a computed tomography (CT) examination of the head. A retrospective study was conducted with 120 subjects (30 men under 55 years old, 30 men over 56 years old, 30 women under 55 years old, and 30 women over 56 years old). Axial images of the squamous portion in the temporal bone were obtained from CT of the head. For this image, a slice sensitive profile (SSP) was acquired with an image analysis program and these were evaluated. The thickness was measured by using a digital ruler to measure the full width at half maximum (FWHM) of the SSP, and the density was measured in hounsfield unit (HU). These by gender were measured to be about 0.5 mm thinner in the temporal bone in men than in women, and there was a significant difference. The density was measured to be about 200 HU higher in women than in men of it, and there was a significant difference. As a result, it in women was thicker and had a lower density. The thickness of it in men and women over 56 years of age was 0.8 mm or more thicker in women and less than 400 HU in density. As a result, the women group over the age of 56 showed a distinct increase in thickness and decrease in density, different from other target groups. It is expected that the results of this study could be used as basic data for a new bone density measurement site study.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.92-98
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• 2021

Purpose: This study automatically discriminates homogeneous and structure edge regions on computed tomography (CT) images, and it evaluates the noise level and edge preservation ratio (EPR) according to the different types of iterative reconstruction (IR). Methods: The dataset consisted of CT scans of 10 patients reconstructed with filtered back projection (FBP), statistical IR (iDose⁴), and iterative model-based reconstruction (IMR). Using the 10th and 85th percentiles of the structure coherence feature, homogeneous and structure edge regions were localized. The noise level was estimated using the averages of the standard deviations for five regions of interests (ROIs), and the EPR was calculated as the ratio of standard deviations between homogeneous and structural edge regions on subtraction CT between the FBP and IR. Results: The noise levels were 20.86±1.77 Hounsfield unit (HU), 13.50±1.14 HU, and 7.70±0.46 HU for FBP, iDose⁴, and IMR, respectively, which indicates that iDose⁴ and IMR could achieve noise reductions of approximately 35.17% and 62.97%, respectively. The EPR had values of 1.14±0.48 and 1.22±0.51 for iDose⁴ and IMR, respectively. Conclusions: The iDose⁴ and IMR algorithms can effectively reduce noise levels while maintaining the anatomical structure. This study suggested automated evaluation measurements of noise levels and EPRs, which are important aspects in CT image quality with patients' cases of FBP, iDose⁴, and IMR. We expect that the inclusion of other important image quality indices with a greater number of patients' cases will enable the establishment of integrated platforms for monitoring both CT image quality and radiation dose.

• Journal of Medicine and Life Science
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• 제20권2호
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• pp.83-88
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• 2023

Metal artifacts cause inaccuracies in target delineation, radiation treatment planning, and delivery when computed tomography images of a radiotherapy patient implanted with a high-density material in the body are acquired. In this study, we investigated the possibility of obtaining improved images in clinical trials through metal artifact reduction using silicon impression materials without the need for a specific metal artifact reduction algorithm. A silicon impression material exhibiting a constant Hounsfield unit (HU) value according to the mixing ratio of the catalysts and bases was selected. The material did not exhibit any change in weight or shape over time. For both the instances of inserting the metal material and applying the silicon impression material, the HU value and dose were compared with homogeneous cases filled with water-equivalent materials. When the silicon impression material was applied to the region where the high-density material was located, the HU value was within 5% and the dose was within 3% compared with those of the homogeneous cases. In this study, the silicon impression materials reduced metal artifacts. However, because the composition, shape, size, and location of high-density materials differ, further studies are required to consider these factors in clinical applications.

• Korean Journal of Radiology
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• 제22권4호
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• pp.624-633
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• 2021

Objective: To evaluate the reliability of CT measurements of muscle quantity and quality using variable CT parameters. Materials and Methods: A phantom, simulating the L2-4 vertebral levels, was used for this study. CT images were repeatedly acquired with modulation of tube voltage, tube current, slice thickness, and the image reconstruction algorithm. Reference standard muscle compartments were obtained from the reference maps of the phantom. Cross-sectional area based on the Hounsfield unit (HU) thresholds of muscle and its components, and the mean density of the reference standard muscle compartment, were used to measure the muscle quantity and quality using different CT protocols. Signal-to-noise ratios (SNRs) were calculated in the images acquired with different settings. Results: The skeletal muscle area (threshold, -29 to 150 HU) was constant, regardless of the protocol, occupying at least 91.7% of the reference standard muscle compartment. Conversely, normal attenuation muscle area (30-150 HU) was not constant in the different protocols, varying between 59.7% and 81.7% of the reference standard muscle compartment. The mean density was lower than the target density stated by the manufacturer (45 HU) in all cases (range, 39.0-44.9 HU). The SNR decreased with low tube voltage, low tube current, and in sections with thin slices, whereas it increased when the iterative reconstruction algorithm was used. Conclusion: Measurement of muscle quantity using HU threshold was reliable, regardless of the CT protocol used. Conversely, the measurement of muscle quality using the mean density and narrow HU thresholds were inconsistent and inaccurate across different CT protocols. Therefore, further studies are warranted in future to determine the optimal CT protocols for reliable measurements of muscle quality.

• 한국의학물리학회지:의학물리
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• 제23권4호
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• pp.269-278
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• 2012

두경부암 방사선치료 시 공동 경계면 및 주변 치료 부위의 선량 균일도 향상을 위하여 조직 등가의 thermoplastic 구강 보상체를 개발하였다. Thermoplastic의 유용성 평가를 위해, 기존에 사용해 오던 치과용 인상재료인 paraffin, alginate, 그리고 putty로 제작한 각 구강 보상체의 물성 및 선량 분포 향상도를 비교하였다. 물성 평가에는 강도 평가(압축 실험, 낙하 실험)와 자연변형도(시간에 따른 체적 변화) 평가를 수행하였으며, 개발한 선량 검증용 팬톰에 삽입한 유리선량계와 Gafchromic EBT2 필름을 이용하여 표면선량, 공동 경계면 선량 및 빔 측면도를 측정하여 전달 선량을 평가하였다. 두 달간 각 구강 보상체의 자연변형도 평가하였을 때, alginate는 수분증발로 최대 80% 체적 변화를 보였으나, thermoplastic을 포함한 나머지 조직 등가 물질은 체적 변화가 3% 미만으로 나타났다. 강도 평가 중 5회 반복한 1.5 m 높이의 자유 낙하실험에서 paraffin은 충격에 의하여 파손이 발생되었으나, thermoplastic은 낙하에 의한 파손이 발생되지 않았으며, 압축 강도 실험에서도 paraffin에 비하여 8배 이상의 높은 힘에서도 파손되지 않았다. 유리선량계를 이용한 선량 검증 결과, 1문 조사 시 조직등가[약 80 HU (Hounsfield Unit)]의 thermoplastic은 동일한 처방 선량 전달 시 약 1,000 HU 이상의 값을 나타내는 putty에 비해 4% 낮은 출력계수(monitor unit) 전달로 약 4.9%의 낮은 표면 선량을 전달하였다. 또한 빔 입사 방향을 기준으로 할 때, 구강 통과 후 경계면의 빔 측면도에서 선량 균일도 평가를 위해 측정한 조사영역 편평도는 air, thermoplastic, putty에서 각각 11.41, 3.98, 4.30으로 나타났다. Thermoplastic 구강 보상체는 조직 등가 물질로 기존에 사용해오던 구강 보상체에 비하여 강도가 높고 물질 변형 확률이 적으며, 구강을 포함을 경계면 및 주변 부위에 균일한 선량 분포를 형성할 수 있으므로 균일한 처방 선량 전달 및 피부 선량 감소가 가능하다.