이중에너지 전산화단층촬영술을 이용한 요오드 정량화: 측정 변이에 관한 인자 탐색, 측정 변이의 범위 계산 및 임상적 검증

학위논문 (박사)-- 서울대학교 대학원 : 의과대학 의학과, 2019. 2. 구진모.서론: 이 연구는 이중에너지 전산화단층촬영술을(CT) 통한 요오드 정량화에 이중에너지 CT 스캐너, 영상 획득 파라미터, 그리고 액체 성상이 미치는 영향을 분석하고, 측정 변이의 범위(measurement variability)를 계산 및 임상적으로 검증하고자 하였다. 방법: Part I과 II에서는 종격동 팬텀을 스캔하고, 요오드 밀도를(iodine density) 측정하여, 이중에너지 CT 스캐너와 영상 획득 파라미터, 액체 성상의 영향을 linear-mixed effect model로 분석하였다. 요오드 밀도의 측정 변이 범위 또한 계산하였다. Part III에서는 요오드 정량화의 변이 범위를 통해 얻은 참조영증강 기준값의(cutoff) 임상적 유용성을 가슴샘종과 가슴샘 낭종으로 수술적 치료를 받은 환자-대조군 연구를 통해 후향적으로 검증하였다. 결과: Part I에서 요오드 밀도의 절대오차는 이중에너지 CT 스캐너 또는 액체 성상에 영향을 받지 않았다(P>0.05). 요오드 참값이 0 mg/ml인 경우, 변이 범위는 -0.6 mg/ml에서 0.4 mg/ml였으며, 따라서 참조영증강의 기준값은 0.4 mg/ml로 정의하였다. Part II에서 관전압과(P<0.001) 관전류(P<0.05교호작용 변수에 따라 P 값에 차이가 있음)는 요오드 정량값에 유의한 영향이 있었으나, 그 영향의 크기, 즉, 회귀계수의 절대값은 매우 작았다. 요오드를 희석한 용매의 성상 역시 유의한 영향이 있었으며(P=0.007), 물과 아미노산 용액 간의 최소제곱평균의 차는 ≥5 mg/ml의 농도를 갖는 튜브에 대해서는 0.1에서 0.3 mg/ml였으며, ≤1 mg/ml의 농도를 갖는 튜브에서는 -0.4에서 -0.1 mg/ml였다. 변수 중 스펙트럴 레벨은 측정에 영향을 미치지 않았다 (P=0.647). Part III에서 참조영증강 기준값은(0.4 mg/ml) 환자-대조군 연구에서 가슴샘종과 가슴샘 낭종을 구분하는데 있어 민감도 100%, 특이도 85.7%, 정확도 90.9%, 양성 예측률 80.0%, 음성 예측률 100%를 보였다. 결론: 요오드 밀도는 이종에너지 CT 촬영기계에 영향을 받지 않는 측정값이다. 요오드 밀도는 CT 획득 변수에 유의한 영향을 받으나, 진단적 CT의 범위 내에서 그 영향의 정도는 미미하다. 참조영증강 요오드 밀도 기준값은(0.4 mg/ml) 가슴샘종과 가슴샘 낭종을 정확하게 구분할 수 있는 유용한 파라미터이다.Purpose: To analyze the effect of dual-energy computed tomography (DECT) scanners, acquisition parameters, and fluid characteristics on iodine quantification and to calculate and validate the measurement variability range induced by those variables. Methods: In Part I and II, experimental studies were performed using four mediastinal iodine phantoms. Phantoms were scanned with three different DECT scanners from major vendors using various acquisition parameters and their effects on the measurement of iodine density (IoD) were investigated using linear mixed-effect models. Measurement variability range of IoD was also calculated. In Part III, diagnostic usefulness of the true enhancement cutoff was retrospectively validated in patients who underwent surgical resections for thymic cysts and thymic epithelial tumors. Results: In Part I, absolute error of IoD was not significantly affected by the DECT systems and kind of solvents (P>0.05). Measurement variability range was from -0.6 to 0.4 mg/ml for the true iodine concentration 0 mg/ml. In Part II, tube voltage (P<0.001) and tube current-time product (P<0.05, depending on the interaction terms) had statistically significant effects on IoD. However, the magnitude of their effects was minimal in the range of diagnostic CT scans. Solvents also had significant effects on IoD (P=0.007). Specifically, the difference of least squares means between water and amino acid solution ranged from 0.1 to 0.3 for tubes with iodine concentrations ≥5 mg/ml and from -0.4 to -0.1 mg/ml for tubes with iodine concentrations ≤1 mg/ml. Spectral level was not an affecting factor (P=0.647). In Part III, the true enhancement cutoff for IoD, which was 0.4 mg/ml, exhibited diagnostic sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 100%, 85.7%, 90.9%, 80.0%, and 100%, respectively, for the differentiation of thymic epithelial tumors from thymic cysts. Conclusions: IoD measurement is robust to the DECT scanners from different vendors. IoD is significantly affected by the acquisition parameters, but the magnitude of effects are minimal in the range of diagnostic CT scans. The true enhancement cutoff of 0.4 mg/ml is an accurate parameter for the differentiation of thymic epithelial tumors from thymic cysts.Abstract i Contents iv List of tables and figures v List of Abbreviations vi Introduction 1 Part I. Materials and Methods 4 Part I. Results 14 Part II. Materials and Methods 30 Part II. Results 36 Part III. Materials and Methods 45 Part III. Results 51 Discussion 54 References 65 Abstract in Korean 74Docto

Applications of Medical Physics

Applications of Medical Physics” is a Special Issue of Applied Sciences that has collected original research manuscripts describing cutting-edge physics developments in medicine and their translational applications. Reviews providing updates on the latest progresses in this field are also included. The collection includes a total of 20 contributions by authors from 9 different countries, which cover several areas of medical physics, spanning from radiation therapy, nuclear medicine, radiology, dosimetry, radiation protection, and radiobiology

Case series of breast fillers and how things may go wrong: radiology point of view

INTRODUCTION: Breast augmentation is a procedure opted by women to overcome sagging breast due to breastfeeding or aging as well as small breast size. Recent years have shown the emergence of a variety of injectable materials on market as breast fillers. These injectable breast fillers have swiftly gained popularity among women, considering the minimal invasiveness of the procedure, nullifying the need for terrifying surgery. Little do they know that the procedure may pose detrimental complications, while visualization of breast parenchyma infiltrated by these fillers is also deemed substandard; posing diagnostic challenges. We present a case series of three patients with prior history of hyaluronic acid and collagen breast injections. REPORT: The first patient is a 37-year-old lady who presented to casualty with worsening shortness of breath, non-productive cough, central chest pain; associated with fever and chills for 2-weeks duration. The second patient is a 34-year-old lady who complained of cough, fever and haemoptysis; associated with shortness of breath for 1-week duration. CT in these cases revealed non thrombotic wedge-shaped peripheral air-space densities. The third patient is a 37‐year‐old female with right breast pain, swelling and redness for 2- weeks duration. Previous collagen breast injection performed 1 year ago had impeded sonographic visualization of the breast parenchyma. MRI breasts showed multiple non- enhancing round and oval shaped lesions exhibiting fat intensity. CONCLUSION: Radiologists should be familiar with the potential risks and hazards as well as limitations of imaging posed by breast fillers such that MRI is required as problem-solving tool

Characterization of alar ligament on 3.0T MRI: a cross-sectional study in IIUM Medical Centre, Kuantan

INTRODUCTION: The main purpose of the study is to compare the normal anatomy of alar ligament on MRI between male and female. The specific objectives are to assess the prevalence of alar ligament visualized on MRI, to describe its characteristics in term of its course, shape and signal homogeneity and to find differences in alar ligament signal intensity between male and female. This study also aims to determine the association between the heights of respondents with alar ligament signal intensity and dimensions. MATERIALS & METHODS: 50 healthy volunteers were studied on 3.0T MR scanner Siemens Magnetom Spectra using 2-mm proton density, T2 and fat-suppression sequences. Alar ligament is depicted in 3 planes and the visualization and variability of the ligament courses, shapes and signal intensity characteristics were determined. The alar ligament dimensions were also measured. RESULTS: Alar ligament was best depicted in coronal plane, followed by sagittal and axial planes. The orientations were laterally ascending in most of the subjects (60%), predominantly oval in shaped (54%) and 67% showed inhomogenous signal. No significant difference of alar ligament signal intensity between male and female respondents. No significant association was found between the heights of the respondents with alar ligament signal intensity and dimensions. CONCLUSION: Employing a 3.0T MR scanner, the alar ligament is best portrayed on coronal plane, followed by sagittal and axial planes. However, tremendous variability of alar ligament as depicted in our data shows that caution needs to be exercised when evaluating alar ligament, especially during circumstances of injury