Clinical Study Of Cardiac And Thoracic Vascular CT Angiography:Technology And Application

Part I The technology feasibility studies and image quality evaluation of computed tomographic pulmonary angiography using dual-energy subtractionObjectives:To assess quantitative and subjective image quality in computed tomography pulmonary angiography(CTPA) with three kinds of dual-energy subtraction methods compared to the monochromatic images with two kinds of optimal contrast-to-noise ratio (OCNR) and the routine polychromatic images (RPI), and to select the best dual-energy subtraction method.Material and methods:This prospective study was approved by the institutional review board and each participant provided informed consent.30 consecutive patients underwent CTPA using a single tube, fast dual tube voltage switching technique. The routine poly-chromatic images (RPI) were generated automatically. Three sets of dual-energy subtraction images (DESI) and two sets of monochromatic images with different optimal contrast-to-noise ratios (OCNR) were obtained with a dedicated workstation with dual-energy software (AW4.5 Advantage WS; GE Healthcare). For all the six sets of images, the signal intensity and noise in three central and two segmental pulmonary arteries were measured; signal-to-noise ratio (SNR) and CNR were calculated. The sharpness of pulmonary artery margins, branch visualization and noise were subjectively rated on five scale points. Then the global subjective image quality was calculated.Results:DESI 3 got the highest CNR and DESI 1 got the second highest CNR, though there was no significant difference with OCNR 1. The three image sets are the top three in each quantitative parameter. In global subjective image quality, DESI 1 got the highest score. However, when compared with DESI 2, no significant difference was found. Both DESI 1 and DESI 2 were significantly better than other image sets. The three subtraction image sets got the highest score in visualization of pulmonary artery branches.Conclusions:CTPA with dual-energy subtraction technique is feasible. DESI1 afforded the best balance between quantitative analysis and subjective evaluation compared with other sets of images, and has the potential to prompt the diagnostic accuracy of PE and other pulmonary vascular diseases.Part Ⅱ The clinical utility of Low-Dose and wide range restrospective ECG-gated cardiac CTA in adults with congenital heart disease.Objectives:To evaluate the feasibility and clinical utility of low-dose and wide range restrospective ECG-gated cardiac CTA in adults with congenital heart disease.Materiel and methods:this prospective study included 150 adult patients who underwent low-dose and wide range restrospective ECG-gated cardiac CTA and transthoracic echocardiography (TTE).The effective radiation dose was calculated and the imaging quality was assessed by quantitative measurements and subjective evaluation. The diagnostic accuracy was calculated and compared based on surgery, thoracoscopic surgery, cardiac interventional procedure and/or conventional cardiac angiography.40 patients randomly selected underwent left ventricle function analysis using cardiac CTA. These results were compared with those obtained by echocardiography.Results:the calculated effective radiation dose was 5.95±0.28mSv. The attenuation of pulmonary artery was 243.18±48.25Hu(≥200Hu in 84% of patients).The attenuation of aortic artery was 263.93±71.51Hu(≥200Hu in 89% of patients).The calculated SNR(signal to noise ratio) and CNR (contrast to noise ratio) of cardiac cavity were 11.31±2.92,8.26±2.68 respectively. The imaging quality of cardiac cavity was subjectively evaluated as excellent in 80.7% of patients. The diagnosable rate of each segment of coronary arteries was greater than or equal to 81%. The diagnostic accuracy of cardiac CTA and TTE in intra cardiac anomalies was 90.4% and 96.8%(p=0.152) respectively and in cardiac-arterial connection anomalies was 94.1% and 80.4%(p=0.022) respectively and in extra cardiac anomalies was 100% and 68.7%(p=0.000) respectively. The ejection fraction of left ventricle obtained by cardiac CTA and TTE was 51.91±10.08% and 53.97±11.75%(p=0.058) respectively. The spearman correlation coefficient was 0.84.Conclusions:wide range retrospective ECG-gated cardiac CTA can be performed using a low-dose protocol. The image quality has the ability to meet the requirements of morphological diagnosis and functional analysis in adult patients with congenital heart disease. Compared with TTE, the Cardiac CTA has unique advantages.Part Ⅲ The anatomical evaluation of periocardiophrenic neurovascular bundle (PNB) using conventional CT coronary artery angiographyObjectives:To observe and measure the PNBs and their relationship with cardiac structure using conventional CT coronary artery angiography (CTCA).Methods and materials:A total of 108 consecutive patients who underwent conventional CT coronary artery angiography were included in this study. The characteristics of subjects for whom the PNB was identified were analysed. Bilateral PNBs were identified by comparing VR images and axial images. The attenuation of bilateral PNBs, the shortest distance between the left atrial appendage and the left PNS, the shortest distance between the ostium of right upper pulmonary vein and the shortest distance between the ostium of right lower pulmonary vein were measured. The structures of heart crossed by left PNB were recorded.Result:The left PNB was identified in 75% of patients (n=81). Much more left PNBs were identified in male patients with higher body mass index and lower heart rate. The shortest distance between the left atrial appendage and the left PNS was 5.9±3. lmm. Mean Hounsfield units (HUs) of the left PNB was 76.9 ±15.4HU. It crossed the lateral wall of the left atrial appendage (n=57,70.4%), anterior interventricular vein(n=11,13.6%), great cardiac vein(n=49,60.5%), marginal vein of the left ventricle (n=61,75.3%), posterior vein of the left ventricle(n=16,19.8%) and posterior interventricular vein(n=7,8.6%). The right PNB was identified in 65.7% of patients (n=71). The shortest distance between the ostium of right upper pulmonary vein and the shortest distance between the ostium of right lower pulmonary vein were 14.1±7.3mm and 16.9 ±8.8mm respectively. Mean HUs of the right phrenic nerve were 81.9±19Hu. No related factor was found to affect the identification of the right PNB. Conlusion:Conventional CTCA was a useful tool to elucidate the anatomy of bilateral PNBs and their relationship with cardiac structures.