• 구강회복응용과학지
• /
• 제23권4호
• /
• pp.313-326
• /
• 2007

With rising prevalency of mouth breathing children caused by developing civilization and increasing pollution, there are many maxillary transverse discrepancy patients with undergrowth of maxilla. For improving this, maxillary mid-palatal suture splitting was often performed. The purpose of this study was to analyse the stress distribution on the craniofacial suture and cranium after rapid maxillary expansion by finite element model. The boy(13Y6M) was chosen for taking computed-tomography for finite element model. Three-dimensional model of maxilla, first premolar, first molar, buccal and lingual part of rapid maxillary expansion were constructed. 1. The alveolar bone adjacent to the first molar and the first premolar that was affected directly by rapid maxillary expansion was displaced laterally approximately 4.04mm at maximum. The force decreased toward anterior region and frontal alveolar bone displaced laterally about 3.18mm. 2. A forward maximum displacement was exhibited at zygomatic process middle region. 3. At maximum, maxillary median part experienced 0.973mm downward repositioning and 0.65mm upward repositioning at lateral alveolar bone. 4. Von mises stress was observed the largest stress distribution around teeth and zygomatic buttress. 5. The largest tensile force was observed around alveolar bone of teeth, while compression force was observed at zygomatic buttress.

• Imaging Science in Dentistry
• /
• 제35권2호
• /
• pp.77-82
• /
• 2005

Purpose : To reveal what is the distinct differential diagnostic differences between unicystic ameloblastoma and solid or multicystic ameloblastoma. Materials and Methods : 56 cases of ameloblastoma were retrospectively reviewed and evaluated among the patients who had taken CT scans at the department of Oral & Maxillofacial Radiology in Yonsei University Dental Hospital from January 1996 to December 2003. Results : In 56 cases, 21 cases $(37.5\%)$ were unicystic ameloblastoma, 35 cases $(62.5\%)$ were solid or multicystic ameloblastoma. Only 1 case $(4.8\%)$ of unicystic ameloblastoma and 4 cases $(11.4\%)$ of solid or multicystic ameloblastoma were occurred in maxilla. 13 cases $(61.9\%)$ of unicystic ameloblastoma were observed as unilocular, and 8 cases $(38.1\%)$ as lobulated. 5 cases $(14.3\%)$ of solid or multicystic ameloblastoma were observed as unilocular, 13 cases $(37.1\%)$ as lobulated, and 17 cases $(48.6\%)$ as multilocular. Tn the results from the measurements after correction of the buccolingual widths and heights to the mesiodistal lengths, there is a statistically significant difference between unicystic ameloblastoma and solid or multicystic ameloblastoma in ANCOVA test (p<0.05). Hounsfield units in the lesion were $24.9{\pm}8.8\;HU$ in unicystic ameloblastoma, $31.2{\pm}11.5\;HU$ in solid or multicystic ameloblastoma. There is no statistically significant difference (p>0.05). Conclusion : Characteristic differences between unicystic ameloblastoma and solid or multicystic ameloblastoma is that there is higher prevalence of solid or multicystic ameloblastoma that have lobulated or multilocular patterns. To measure the Hounsfield units in the lesion is helpful, but it is not a differential diagnostic point between unicystic ameloblastoma and solid or multicystic ameloblastoma.

• Imaging Science in Dentistry
• /
• 제48권1호
• /
• pp.31-39
• /
• 2018

Purpose: This study aimed to evaluate the effect of field-of-view (FOV) size on the gray values derived from cone-beam computed tomography (CBCT) compared with the Hounsfield unit values from multidetector computed tomography (MDCT) scans as the gold standard. Materials and Methods: A radiographic phantom was designed with 4 acrylic cylinders. One cylinder was filled with distilled water, and the other 3 were filled with 3 types of bone substitute: namely, Nanobone, Cenobone, and Cerabone. The phantom was scanned with 2 CBCT systems using 2 different FOV sizes, and 1 MDCT system was used as the gold standard. The mean gray values(MGVs) of each cylinder were calculated in each imaging protocol. Results: In both CBCT systems, significant differences were noted in the MGVs of all materials between the 2 FOV sizes(P<.05) except for Cerabone in the Cranex3D system. Significant differences were found in the MGVs of each material compared with the others in both FOV sizes for each CBCT system. No significant difference was seen between the Cranex3D CBCT system and the MDCT system in the MGVs of bone substitutes on images obtained with a small FOV. Conclusion: The size of the FOV significantly changed the MGVs of all bone substitutes, except for Cerabone in the Cranex3D system. Both CBCT systems had the ability to distinguish the 3 types of bone substitutes based on a comparison of their MGVs. The Cranex3D CBCT system used with a small FOV had a significant correlation with MDCT results.

• Nuclear Engineering and Technology
• /
• 제53권12호
• /
• pp.4158-4165
• /
• 2021

In this study, tissue equivalency (TE) of a newly developed epoxy-based phantom to 3-5 years child's tissue was investigated in paediatric energy range. Epoxy-based TE-phantoms were produced at different glandular/adipose (G/A) ratios of 17/83%, 31/69%, 36/64% and 10/90%. A procedure was developed in which specific amounts of boron, calcium, magnesium, sulphur compounds are mixed with epoxy resin, together with other minor substitutes. In paediatric energy range of 40-60 kV_p half-value layer (HVL) values were measured and then Hounsfield Units (HU) were determined from Computed Tomography(CT) scans taken in the X-ray energy range of 80-120kV_p. It is found that radiation absorption properties of these phantoms in terms of the measured HVL values related to linear attenuation coefficients (µ) are very well mimicking a 3 years child's soft tissue in case a ratio of 10/90%G/A. Additionally, the HU values of phantoms were determined from the CT scans. The HU = 47.8 ± 4.8 value was found for the epoxy-based phantom produced at a ratio of 10/90%G/A. The obtained HVL and HU values also support the suitability of the new epoxy based-phantom produced at a ratio of 10/90%G/A for a satisfactory mimicking a 3 years child's soft tissue by 5%. Thus they can have a potential use to perform the quality controls of medical X-ray systems and dose optimization studies.

• Imaging Science in Dentistry
• /
• 제52권2호
• /
• pp.133-140
• /
• 2022

Purpose: The aim of this review was to systematically analyze the available literature on the correlation between the gray values (GVs) of cone-beam computed tomography (CBCT) and the Hounsfield units (HUs) of computed tomography (CT) for assessing bone mineral density. Materials and Methods: A literature search was carried out in PubMed, Cochrane Library, Google Scholar, Scopus, and LILACS for studies published through September 2021. In vitro, in vivo, and animal studies that analyzed the correlations GVs of CBCT and HUs of CT were included in this review. The review was prepared according to the PRISMA checklist for systematic reviews, and the risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool. A quantitative analysis was performed using a fixed-effects model. Results: The literature search identified a total of 5,955 studies, of which 14 studies were included for the qualitative analysis and 2 studies for the quantitative analysis. A positive correlation was observed between the GVs of CBCT and HUs of CT. Out of the 14 studies, 100% had low risks of bias for the domains of patient selection, index test, and reference standards, while 95% of studies had a low risk of bias for the domain of flow and timing. The fixed-effects meta-analysis performed for Pearson correlation coefficients between CBCT and CT showed a moderate positive correlation (r=0.669; 95% CI, 0.388 to 0.836; P<0.05). Conclusion: The available evidence showed a positive correlation between the GVs of CBCT and HUs of CT.

• Journal of Veterinary Science
• /
• 제23권5호
• /
• pp.65.1-65.10
• /
• 2022

Background: Persistent uroliths after a cystotomy in dogs are a common cause of surgical failure. Objectives: This study examined the following: the success rate of retrograde urohydropropulsion in male dogs using non-enhanced computed tomography (CT), whether the CT mean beam attenuation values in Hounsfield Units (mHU) measured in vivo could predict the urolithiasis composition and whether the selected reconstruction kernel may influence the measured mHU. Methods: All dogs and cats that presented with lower urinary tract uroliths and had a non-enhanced CT preceding surgery were included. In male dogs, CT was performed after retrograde urohydropropulsion to detect the remaining urethral calculi. The percentage and location of persistent calculi were recorded. The images were reconstructed using three kernels, from smooth to ultrasharp, and the calculi mHU were measured. Results: Sixty-five patients were included in the study. The success rate of retrograde urohydropropulsion in the 45 male dogs was 55.6% and 86.7% at the first and second attempts, respectively. The predominant components of the calculi were cystine (20), struvite (15), calcium oxalate (8), and urate (7). The convolution kernel influenced the mHU values (p < 0.05). The difference in mHU regarding the calculus composition was better assessed using the smoother kernel. A mHU greater than 1,000 HU was predictive of calcium oxalate calculi. Conclusions: Non-enhanced CT is useful for controlling the success of retrograde urohydropropulsion. The mHU could allow a prediction of the calculus composition, particularly for calcium oxalate, which may help determine the therapeutic strategy.

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

• 한국임상수의학회지
• /
• 제31권6호
• /
• pp.495-501
• /
• 2014

본 연구는 다양한 전산화단층촬영기기와 촬영 프로토콜의 차이에 따른 모형물의 부피와 Hounsfield unit (HU) 수치의 차이를 평가하고 이 후 전산화단층촬영술을 이용하여 결석의 부피와 HU 수치를 포함한 다양한 인자들을 평가하고 이 중 체외충격파쇄석술에 의한 결석의 분쇄를 예측할 수 있는 인자를 찾고자 하였다. 다양한 직경의 100 HU 인공종양 5개를 (직경 3.0-12.0 mm) 이용하여 모형물을 만들었으며, 이 모형물의 부피와 HU 수치를 Siemens사의 2채널, GE사의 4채널과 64채널, 그리고 Philips사의 64채널 전산화단층촬영기기를 사용하여 평가하였다. 또한 각각의 전산화단층촬영기기에서 동일한 조건으로 collimation만 thin collimation과 thick collimation으로 변화를 주어 모형물을 촬영한 후 모형물의 부피와 HU 수치를 평가하였다. 평가자간 (inter-observer) 재현성을 평가하기 위해 3명의 수의영상의학 전공의가 연구에 참여하였으며 이중 한 명의 수의사가 평가자내 (intra-observer) 재현성을 평가하기 위해 모형물의 부피와 HU 수치를 2주 간격으로 총 3번 측정하였다. 부피의 평가자간 재현성과 평가자내 재현성은 k=0.9994, k=0.9969로 아주 우수하였으며, HU 수치의 평가자간 재현성과 평가자내 재현성 역시 k=0.9984, k=0.9655로 아주 우수하였다. 다양한 전산화단층촬영기기와 collimation 차이에 따른 부피와 HU 수치의 차이는 모두 통계학적으로 유의적인 차이를 나타내지 않았다. 그러나 부피의 경우 collimation이 얇을수록 부피의 정확도가 증가하는 경향을 보였다. 본 연구 결과를 토대로 향후 진행될 결석의 부피 및 HU 수치의 평가 시 전산화단층촬영기기의 차이에 따른 영향을 받지 않으리라 판단되어 Siemens사의 2채널 전산화단층촬영기기만을 사용하였으며, 비록 통계학적으로 유의적인 차이는 없었지만 부피의 정확도를 더 높이기 위하여 얇은 collimation을 사용하였다.

• 한국방사선학회논문지
• /
• 제17권4호
• /
• pp.541-549
• /
• 2023

본 연구는 CT 촬영 시 금속으로 인해 발생한 금속 인공물 감소를 위한 알고리즘 적용에 따른 영상 화질에 대한 정량적 비교를 하고자 한다. Spectral detected-based CT와 CT ACR 464 팬톰을 이용하여 일반적인 필터보정역투영 알고리즘을 적용한 기준 영상을 10장 획득하고, 동일 팬톰에 금속 인공물을 발생시켜 일반적인 필터보정역투영 알고리즘을 적용한 영상을 10장 획득하였다. 금속 인공물을 발생시켜 획득한 영상의 원시 데이터에 metal artifact reduction 알고리즘, 가상 단일 에너지 알고리즘, metal artifact reduction 알고리즘 적용 후 추가로 가상 단일 에너지 알고리즘을 적용한 영상을 각각 10장씩 획득하였다. 알고리즘 적용에 따른 hounsfield unit 비교를 위해 CT ACR 464 팬톰 module 1에 위치한 폴리에틸렌, 뼈, 아크릴, 공기, 물에 관심영역을 설정하고, 전체 영상 화질 평가를 위해 평균 제곱근 오차, 평균 절대 오차, 신호 대 잡음비, 최대 신호 대 잡음비, 구조적 유사도 지수 지표를 통해 알고리즘 별 비교하였다. 알고리즘 적용 영상 별 hounsfield unit 비교 결과 알고리즘 적용 영상 간 유의한 차이를 보였으며(p < .05), 아크릴을 제외한 관심영역에서 가상 단일 에너지 알고리즘 적용 영상에서 큰 변화를 나타냈다. 영상 화질 평가 지표 결과 metal artifact reduction 알고리즘 적용 영상 화질이 가장 높았으나, 구조적 유사도 지수는 metal artifact reduction 알고리즘 적용 후 추가로 가상 단일 에너지 알고리즘이 동시에 적용된 영상이 가장 높았다. CT 촬영 시 금속 인공물 감소에 metal artifact reduction 알고리즘이 가상 단일 에너지 알고리즘에 비해 효과적이었지만, 양질의 CT 영상 획득을 위해 알고리즘 적용에 따른 이점과 영상 화질 변화를 파악하고 효율적인 활용이 필요하다고 사료된다.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제35권5호
• /
• pp.310-315
• /
• 2013

Micromorphometric and histological examinations were conducted with a collected tissue specimen nine months after sinus bone graft using autogenous tooth bone graft material (AutoBT). As a result of micro-computed tomographic analysis, the total bone volume (graft material+new bone) was 76.45%, and the proportion of new bone was 45.4%. The bone mineral density and the average Hounsfield Unit of new bone were 0.26 and 1,164.69, respectively. The histological examination showed that AutoBT particles were united well with new bone. AutoBT was considered to have excellent bone healing ability after sinus graft and bone density that can resist repneumatization.