• Imaging Science in Dentistry
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• 제38권1호
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• pp.7-15
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• 2008

Purpose: This study provides comparative measurements of absorbed and effective doses for newly developed cone beam computed tomography (CT) in comparison with these doses for conventional CT. Materials and Methods: Thermoluminescent dosimeter rods (TLD rod: GR-200, Thermo Fisher Scientific Inc., Waltham, MA, USA) were placed at 25 sites throughout the layers of Male ART Head and Neck Phantom (Radiology Support Devices Inc., Long Beach, USA) for dosimetry. Implagraphy, DCT Pro (Vatech Co., Hwasung, Korea) units, SCT-6800TXL (Shimadzu Corp., Kyoto, Japan), and Crane x 3+(Soredex Orion Corp., Helsinki, Finland) were used for radiation exposures. Absorption doses were measured with Harshaw 3500TLD reader (Thermo Fisher Scientific Inc., Waltham, MA, USA). Radiation weighted doses and effective doses were measured and calculated by 2005 ICRP tissue weighting factors. Results: Absorbed doses in Rt. submandibular gland were 110.57 mGy for SCT 6800TXL (Implant), 24.56 mGy for SCT 6800TXL (3D), 22.39 mGy for Implagraphy 3, 7.19 mGy for DCT Pro, 5.96 mGy for Implagraphy 1, 0.70 mGy for Cranex 3+. Effective doses $(E_{2005draft)$ were 2.551 mSv for SCT 6800TXL (Implant), 1.272 mSv for SCT 6800TXL (3D), 0.598 mSv for Implagraphy 3, 0.428 mSv for DCT Pro and 0.146 mSv for Implagraphy 1. These are 108.6, 54.1, 25.5, 18.2 and 6.2 times greater than panoramic examination (Cranex 3+) doses (0.023mSv). Conclusion: Cone beam CT machines recently developed in Korea, showed lower effective doses than conventional CT. Cone beam CT provides a lower dose and cost alternative to conventional CT, promising to revolutionize the practice of oral and maxillofacial radiology.

• Radiation Oncology Journal
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• 제35권4호
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• pp.340-348
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• 2017

Purpose: To evaluate the diagnostic accuracy of computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT) in predicting pelvic lymph node (LN) metastases in patients with cervical cancer. Materials and Methods: From January 2009 to March 2015, 114 patients with FIGO stage IA1-IIB uterine cervical cancer who underwent hysterectomy with pelvic lymphadenectomy and took CT, MRI, and PET/CT before surgery were enrolled in this study. The criteria for LN metastases were a LN diameter ${\geq}1.0cm$ and/or the presence of central necrosis on CT, a LN diameter ${\geq}1.0cm$ on MRI, and a focally increased FDG uptake on PET/CT. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for pelvic LN metastases were estimated. Results: The sensitivity, specificity, PPV, NPV, and accuracy for detection of pelvic LN metastases were 51.4%, 85.9%, 41.3%, 90.1%, and 80.3% for CT; 24.3%, 96.3%, 56.3%, 86.8%, and 84.6% for MRI; and 48.6%, 89.5%, 47.4%, 90.0%, and 82.9% for PET/CT, respectively. The sensitivity of PET/CT and CT was higher than that of MRI (p=0.004 and p= 0.013, respectively). The specificity of MRI was higher than those of PET/CT and CT (p=0.002 and p=0.001, respectively). The difference of specificity between PET/CT and CT was not statistically significant (p=0.167). Conclusion: These results indicate that preoperative CT, MRI, and PET/CT showed low to moderate sensitivity and PPV, and moderate to high specificity, NPV, and accuracy. More efforts are necessary to improve sensitivity of imaging modalities in order to predict pelvic LN metastases.

• 대한방사선치료학회지
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• 제28권2호
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• pp.123-130
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• 2016

목 적 : Computerized imaging reference systems 동적팬텀을이용한 cone-beamcomputed tomography(CBCT) 영상과 four-dimensionalcomputed tomography(4DCT) 영상의 체적을 비교분석 하고자 한다. 대상 및 방법 : 동적팬텀 내에 직경 1, 2, 3 cm 노드를 각각 삽입하고, CT simulator와 TruebeamSTx X-ray Imaging system을 이용하여 4DCT 영상과 CBCT 영상을 얻었다. 4DCT 영상은 maximum intensity projection(MIP), minimum intensity projection(MinIP), 그리고 average intensity projection(AVG)영상으로 재구성 하고 노드의 체적은 Eclipse system의 CT ranger tool로 CT number를 설정하여 측정하였다. 결 과 : CBCT를 기준으로 노드1, 2, 3 cm의 체적을 비교하였을 때 4DCT의 MIP는 0.54~2.33, 5.16~8.06, 9.03~20.11 ml, MinIP는 0.00~1.48, 0.00~8.47, 1.42~24.85 ml, AVG는 0.00~1.17, 0.00~2.19, 0.04~3.35 ml의 차이를 보였다. 결 론 : 노드의 체적을 비교한 결과 CBCT 영상은 4DCT의 AVG 영상과 유사한 것으로 확인되었다.

• Imaging Science in Dentistry
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• 제32권2호
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• pp.89-97
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• 2002

Purpose: The objective of this study is to find the differentiating characteristics of ameloblastomas and odontogenic keratocysts of the jaw by analyzing computed tomography (CT) images of the lesions, clarify radiological characteristics associated with jaw lesions, and to make a diagnsis based on these findings. Materials and Methods : Test subjects were chosen among the patients who were diagnosed as having an odontogenic keratocyst or ameloblastoma at the Yonsei University Dental Hospital from January 1996 to December 2000 and had CT scans taken preoperatively. The subject pool was comprised of 51 cases of odontogenic keratocyst and 37 cases of ameloblastoma. The following measures were used for image analysis of the lesion: the anatomic location, CT pattern, mesiodistal width, buccolingual width, the ratios between mesiodistal width and buccolingual width, height, CT number, homogeneity of radiodensity, the appearance of a sclerotic rim, continuity of adjacent cortical bone, and displacement and resorption of adjacent teeth. Results: Comparing the CT patten, mesiodistal width, buccolingual width, height, CT number, homogeneity, appearance of sclerotic rim, continuity of adjacent cortical bone, there were statistically significant differences between ameloblastoma and odontogenic keratocyst test subjects (p<0.05). Comparing the ratios between mesiodistal width and buccolingual width, displacement and resorption of adjacent teeth, there were no statistically significant differences (p>0.05). Conclusion: We compared odontogenic keratocysts and ameloblastomas in CT scans. They occurred most frequently in the posterior to the ramus of the mandible. The findings of patterns of the CT images showed that size and border of lesions were more aggressive in ameloblastomas than in odontogenic keratocysts. The internal contents represented an increased attenuation area (IAA) in odontopenic keratocyst. Odontogenic keratocysts were shown to have higher CT numbers than ameloblastomas.

• Journal of Radiation Protection and Research
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• 제46권3호
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• pp.98-105
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• 2021

Background: In recent events of the coronavirus disease 2019 (COVID-19) pandemic, computed tomography (CT) scans are being globally used as a complement to the reverse-transcription polymerase chain reaction (RT-PCR) tests. It will be important to be aware of major organ dose levels, which are more relevant quantity to derive potential long-term adverse effect, for Korean pediatric and adult patients undergoing CT for COVID-19. Materials and Methods: We calculated organ dose conversion coefficients for Korean pediatric and adult CT patients directly from Korean pediatric and adult computational phantoms combined with Monte Carlo radiation transport techniques. We then estimated major organ doses delivered to the Korean child and adult patients undergoing CT for COVID-19 combining the dose conversion coefficients and the international survey data. We also compared our Korean dose conversion coefficients with those from Caucasian reference pediatric and adult phantoms. Results and Discussion: Based on the dose conversion coefficients we established in this study and the international survey data of COVID-19-related CT scans, we found that Korean 7-year-old child and adult males may receive about 4-32 mGy and 3-21 mGy of lung dose, respectively. We learned that the lung dose conversion coefficient for the Korean child phantom was up to 1.5-fold greater than that for the Korean adult phantom. We also found no substantial difference in dose conversion coefficients between Korean and Caucasian phantoms. Conclusion: We estimated radiation dose delivered to the Korean child and adult phantoms undergoing COVID-19-related CT examinations. The dose conversion coefficients derived for different CT scan types can be also used universally for other dosimetry studies concerning Korean CT scans. We also confirmed that the Caucasian-based CT organ dose calculation tools may be used for the Korean population with reasonable accuracy.

• Korean Journal of Radiology
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• 제24권9호
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• pp.890-902
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• 2023

Objective: The clinical impact of artificial intelligence-based computer-aided detection (AI-CAD) beyond diagnostic accuracy remains uncertain. We aimed to investigate the influence of the clinical implementation of AI-CAD for chest radiograph (CR) interpretation in daily practice on the rate of referral for chest computed tomography (CT). Materials and Methods: AI-CAD was implemented in clinical practice at the Seoul National University Hospital. CRs obtained from patients who visited the pulmonology outpatient clinics before (January-December 2019) and after (January-December 2020) implementation were included in this study. After implementation, the referring pulmonologist requested CRs with or without AI-CAD analysis. We conducted multivariable logistic regression analyses to evaluate the associations between using AI-CAD and the following study outcomes: the rate of chest CT referral, defined as request and actual acquisition of chest CT within 30 days after CR acquisition, and the CT referral rates separately for subsequent positive and negative CT results. Multivariable analyses included various covariates such as patient age and sex, time of CR acquisition (before versus after AI-CAD implementation), referring pulmonologist, nature of the CR examination (baseline versus follow-up examination), and radiology reports presence at the time of the pulmonology visit. Results: A total of 28546 CRs from 14565 patients (mean age: 67 years; 7130 males) and 25888 CRs from 12929 patients (mean age: 67 years; 6435 males) before and after AI-CAD implementation were included. The use of AI-CAD was independently associated with increased chest CT referrals (odds ratio [OR], 1.33; P = 0.008) and referrals with subsequent negative chest CT results (OR, 1.46; P = 0.005). Meanwhile, referrals with positive chest CT results were not significantly associated with AI-CAD use (OR, 1.08; P = 0.647). Conclusion: The use of AI-CAD for CR interpretation in pulmonology outpatients was independently associated with an increased frequency of overall referrals for chest CT scans and referrals with subsequent negative results.

• Journal of Trauma and Injury
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• 제22권1호
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• pp.24-28
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• 2009

Purpose: This was conducted to assess the need for conventional radiographs of the thoracolumbar spine for routine screening of trauma patients who revealed no spinal trauma on chest and abdominal computed tomography (CT). Methods: We performed a retrospective review of the medical records of trauma patients who underwent conventional radiographs of the thoracolumbar spine following a chest and abdominal CT that revealed no spinal trauma. Results: Two hundred seventy-five trauma patients underwent conventional radiographs of the thoracolumbar spine following a chest and abdominal CT that revealed no spinal trauma. In 274 of the cases, the thoracolumbar spine series was also negative. Conclusion: CT of the chest and abdomen is an adequate evaluation of the thoracolumbar spine in trauma patients who require routine thoracolumbar spine screening, making subsequent conventional radiographs of the thoracolumbar spine unnecessary.

• Korean Journal of Radiology
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• 제24권10호
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• pp.1006-1016
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• 2023

Objective: Computed tomography (CT) is an established method for the diagnosis, staging, and treatment of multiple myeloma. Here, we investigated the potential of photon-counting detector computed tomography (PCD-CT) in terms of image quality, diagnostic confidence, and radiation dose compared with energy-integrating detector CT (EID-CT). Materials and Methods: In this prospective study, patients with known multiple myeloma underwent clinically indicated whole-body PCD-CT. The image quality of PCD-CT was assessed qualitatively by three independent radiologists for overall image quality, edge sharpness, image noise, lesion conspicuity, and diagnostic confidence using a 5-point Likert scale (5 = excellent), and quantitatively for signal homogeneity using the coefficient of variation (CV) of Hounsfield Units (HU) values and modulation transfer function (MTF) via the full width at half maximum (FWHM) in the frequency space. The results were compared with those of the current clinical standard EID-CT protocols as controls. Additionally, the radiation dose (CTDIvol) was determined. Results: We enrolled 35 patients with multiple myeloma (mean age 69.8 ± 9.1 years; 18 [51%] males). Qualitative image analysis revealed superior scores (median [interquartile range]) for PCD-CT regarding overall image quality (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), edge sharpness (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), image noise (4.0 [4.0-4.0] vs. 3.0 [3.0-4.0]), lesion conspicuity (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), and diagnostic confidence (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]) compared with EID-CT (P ≤ 0.004). In quantitative image analyses, PCD-CT compared with EID-CT revealed a substantially lower FWHM (2.89 vs. 25.68 cy/pixel) and a significantly more homogeneous signal (mean CV ± standard deviation [SD], 0.99 ± 0.65 vs. 1.66 ± 0.5; P < 0.001) at a significantly lower radiation dose (mean CTDIvol ± SD, 3.33 ± 0.82 vs. 7.19 ± 3.57 mGy; P < 0.001). Conclusion: Whole-body PCD-CT provides significantly higher subjective and objective image quality at significantly reduced radiation doses than the current clinical standard EID-CT protocols, along with readily available multi-spectral data, facilitating the potential for further advanced post-processing.

• 대한수의학회지
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• 제51권2호
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• pp.165-169
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• 2011

Barium suspension, oral iodine contrast medium and water were applied in eight dogs to evaluate (1) distension of gastrointestinal tract, (2) the effect of the oral contrast media on the identification of the pancreas from surrounding organs, and (3) image quality and the presence of artifacts in canine pancreas computed tomography (CT) images. Oral iodine contrast medium, gastrografin, produced significant artifacts that deteriorated the CT images of the pancreas. The use of water did not provide the fullness of the gastrointestinal lumens. Barium suspension was effective for the identification of the pancreas from the surrounding gastrointestinal tract, without significantly increasing image noise. Barium suspension can be used as an optimal contrast medium that will not cause an adverse effect on the pancreatic density and image quality.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제47권1호
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• pp.51-56
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• 2021

Due to their rarity and the lack of associated dental symptoms, odontogenic cutaneous sinus tracts (OCSTs) are often misdiagnosed and confused with cutaneous lesions or non-odontogenic infections. It has been estimated that 50% of individuals affected by OCSTs are subjected to inappropriate treatments before the correct diagnosis is established. We describe the diagnosis and treatment of two cases of OCSTs. By using a computed tomography (CT) with soft tissue window setting, the extent of cortical bone destruction and the path of the sinus tract in the soft tissue was easily identified. Thus, we recommend the use of imaging techniques such as CT, which can confirm the odontogenic origin and the exact location of the OCST.