Nobuo Tomizawa

Adaptive Iterative Dose Reduction in coronary CT angiography using 320-row CT: Assessment of radiation dose reduction and image quality

BACKGROUND Several methods have been developed to reduce the radiation dose in coronary computed tomography angiography (CTA). OBJECTIVE The objective of our study was to evaluate the effects of Adaptive Iterative Dose Reduction (AIDR) on objective and subjective image quality as well as the radiation dose, compared with conventional filtered back projection (FBP), in coronary CTA. METHODS We retrospectively reviewed 100 consecutive patients who underwent coronary CTA. In the first 50 patients, a higher tube current was used, and images were reconstructed with FBP. In the last 50 patients, a lower tube current was used, and images were reconstructed with AIDR. Subjective and objective image quality (noise, signal-to-noise ratio, contrast-to-noise ratio) were assessed. RESULTS The median radiation dose of the AIDR group was 22% lower than that of the FBP group (4.2 vs 5.4 mSv; P = 0.0001). No significant difference was found in subjective image quality, noise, signal-to-noise ratio, or contrast-to-noise ratio between the 2 groups. CONCLUSION AIDR reduced the tube current which resulted in reduction of radiation dose in coronary CTA while maintaining subjective and objective image quality compared with coronary CTA reconstructed with FBP.

Influence of hemodynamic parameters on coronary artery attenuation with 320-detector coronary CT angiography.

OBJECTIVES To investigate the relationship between cardiac output, end diastolic volume and the contrast enhancement in coronary CT angiography using 320-detector CT. MATERIALS AND METHODS A total of 38 patients underwent coronary CT angiography by using a 320-detector CT scanner (detector configuration, 320 × 0.5mm). The attenuation value of the ascending aorta at the level of the orifice of the left main trunk was measured. The cardiac output (CO), end diastolic volume (EDV) and stroke volume (SV) were measured by echocardiography. The EDV was normalized to the body surface area (BSA). The total blood volume injected from the left ventricle from the beginning of the contrast agent injection to the time of image acquisition was determined to be the total injected blood volume (TIV), which is a product of SV and the number of heart beats from the initiation of contrast agent injection to the scan. RESULTS There was a negative correlation between the attenuation of the ascending aorta and CO (r = -0.44, P = 0.0053). However, the negative correlation between the attenuation of the ascending aorta and TIV was stronger (r = -0.52, P = 0.0007). There was a negative correlation between the attenuation of the ascending aorta and EDV/BSA (r = -0.45, P = 0.0039). CONCLUSION In 320-detector CT, contrast enhancement in CCTA with a lesser amount of contrast medium decreases when cardiac output is high. Patients with larger EDV/BSA may also show decreased attenuation.

An International Multicenter Comparison of Time-SLIP Unenhanced MR Angiography and Contrast-Enhanced CT Angiography for Assessing Renal Artery Stenosis: The Renal Artery Contrast-Free Trial

OBJECTIVE The unenhanced MR angiography (MRA) technique time-spatial labeling inversion pulse (time-SLIP) may provide a safe alternative for evaluating the renal arteries for stenosis. This international multicenter trial tested the hypothesis that time-SLIP unenhanced MRA is accurate and robust for assessing the renal arteries for stenosis in comparison with contrast-enhanced CT angiography (CTA). SUBJECTS AND METHODS Four centers (United States, Europe, Asia) enrolled 75 patients (average age ± SD, 58 ± 13 years; 41 [55%] men and 34 [45%] women). Each patient underwent abdominal contrast-enhanced CTA and abdominal unenhanced MRA using time-SLIP with balanced steady-state free precession. All images were visually assessed for quality (arterial signal intensity) and for the absence or presence of renal artery stenosis (≤ 50% or > 50% stenosis, respectively). In addition, for arteries with any visible disease, the severity of the stenosis was quantified. Two blinded readers evaluated each study. No arteries were excluded from analysis. RESULTS Unenhanced MRA image quality was excellent for 56 of 75 patients (75%) and good for 16 of 75 patients (21%). CTA was used as the reference standard and showed that 23 of 161 renal arteries (14.3%) had stenosis > 50%. Unenhanced MRA correctly classified 17 of the 23 renal arteries with > 50% stenosis and correctly classified 128 of the 138 renal arteries as not having disease (≤ 50% stenosis) to yield a sensitivity of 74%, specificity of 93%, and accuracy of 90% (χ(2) = 0.56; p = 0.45, no statistically significant difference). Of the 16 misclassified arteries, only three had a clinically relevant misclassification (CTA ≥ 70% stenosis and unenhanced MRA ≤ 50% stenosis or unenhanced MRA ≥ 70% stenosis and CTA ≤ 50% stenosis). On average, measured stenotic severity (n = 28 arteries) was similar for unenhanced MRA (64% ± 17%) and CTA (62% ± 16%) (p = 0.51). CONCLUSION Compared with contrast-enhanced CTA, the unenhanced MRA technique time-SLIP shows promise for assessing the renal arteries for stenosis. The unenhanced MRA technique time-SLIP may provide a safe alternative for evaluating the renal arteries for stenosis.

Prepancreatic postduodenal portal vein: a new hypothesis for the development of the portal venous system

The prepancreatic postduodenal portal vein (PPPV) is an unusual anomaly, having been reported in only 11 cases including ours. Although its incidence is rare, this anomaly can cause intraoperative complications such as hemorrhage from the abnormal vein. Radiologists therefore need to be aware of this anomaly and, when identifi ed, report it to surgeons before surgery. Here we report two cases of PPPV and present a new hypothesis for development of the portal venous system.

A clinical model to identify patients with high-risk plaque by coronary computed tomography angiography

OBJECTIVES Current clinical models predict the pre-test probability of obstructive coronary artery disease, but these models do not predict the presence of high-risk plaques. Thus the objective of this study was to propose a model to predict high-risk plaque assessed by coronary computed tomography (CT) angiography. METHODS This study was a retrospective cross-sectional study. A clinical model was derived from 2392 patients and verified by 733 patients who underwent coronary CT suspected of coronary artery disease. High-risk plaque was defined as a plaque with positive remodeling (remodeling index>1.1), low attenuation (<30Hounsfield units) and napkin-ring sign. The risk score was calculated from the following 6 variables with a maximum of 24 points: age, sex, hemoglobin A1c, systolic blood pressure, high-density lipoprotein and smoking status. RESULTS The proportion of patients with high-risk plaque was 11% and 17% in the derivation and validation cohort, respectively. The area under the receiver operation characteristic curve was 0.71 (95% confidence interval (CI): 0.68 to 0.74) in the derivation cohort and 0.75 (95% CI: 0.70 to 0.79) in the validation cohort. The frequency of high-risk plaques was 4% in the low-risk group (≤8 points) while it was 53% in the high-risk group (≥17 points) of the derivation cohort. CONCLUSIONS We propose a scoring system to detect high-risk plaque assessed by coronary CT. Patients in the high-risk group have a high prevalence of high-risk plaque and might benefit from lipid lowering therapy.

Improving the diagnostic performance of the real world coronary computed tomography angiography including uninterpretable segments.

OBJECTIVES The purpose was to investigate the diagnostic performance of coronary computed tomography angiography (CTA) when non-calcified uninterpretable segments were determined as either obstructive or patent. We also investigated the factors that could improve the diagnosis of CTA. METHODS A total of 268 patients without known coronary artery disease who were clinically indicated for coronary angiogram (CAG) within 50days of coronary CTA were retrospectively included. The diagnostic performance of CTA was assessed with CAG as a reference, whereas stenosis of ≥50% was considered obstructive. We compared the results when non-calcified uninterpretable segments were determined as obstructive or patent. Coronary risk factors as well as contrast medium arrival time adjusted by heart rate (CATHR) were investigated for improvement of CTA diagnosis. RESULTS Area under the receiver operating characteristic curve (AUC) improved when uninterpretable segments were determined as patent rather than obstructive (0.79 vs 0.73, p=0.02). Multivariate analysis showed that CATHR was a predictor of CAG stenosis (odds ratio 1.13, p=0.046) while other risk factors were not. Adding CATHR further improved the AUC to 0.82 (p=0.003). The accuracy, sensitivity, specificity, positive predictive value and negative predictive value of CTA stenosis (uninterpretable segments as obstructive) were 72%, 99%, 32%, 68% and 95%. The values were 78%, 89%, 61%, 77% and 80% when CATHR was added and uninterpretable segments determined as patent. CONCLUSIONS The diagnostic performance of coronary CTA improved when non-calcified uninterpretable segments were determined as patent rather than obstructive. Adding CATHR could further improve the specificity.

Effect of saline flush on enhancement of proximal and distal segments using 320-row coronary CT angiography

OBJECTIVE To investigate the effect of saline flush on coronary CT angiography of proximal, middle, and distal coronary artery segments, using 320-row CT, and to compare two injection duration protocols as to amount of contrast in the right heart chambers. METHODS This retrospective study was approved by the local ethics committee, and the requirement for informed consent to participate in this study was waived. The final study group included 108 patients who underwent coronary CT angiography. The first 36 patients received contrast medium without saline flush (group 1); the next 36 patients received contrast medium for 14s and saline flush (group 2); the last 36 patients received contrast medium for 12s and saline flush (group 3). The CT number, noise, contrast-to-noise ratio (CNR), and number of segments with a CT number greater than 325 Hounsfield units (HU) were recorded for proximal, middle, and distal segments. RESULTS The CT numbers and the CNR in groups 2 and 3 were significantly higher than that in group 1 (p<0.005); the difference between groups 2 and 3 was not significant. The proportion of segments greater than 325HU improved with saline flush (p<0.05), with a larger improvement in the distal segments. CONCLUSIONS Saline flush improves enhancement and CNR of coronary arteries, particularly of distal segments, in coronary CT angiography using 320-row CT. An average contrast medium injection of 44mL was feasible using a saline flush.

Clinical utility of landiolol for use in coronary CT angiography

License. The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. Permissions beyond the scope of the License are administered by Dove Medical Press Limited. Information on how to request permission may be found at: http://www.dovepress.com/permissions.php Research Reports in Clinical Cardiology 2015:6 145–152 Research Reports in Clinical Cardiology Dovepress

High prevalence of coronary artery events and non-coronary events in patients with coronary artery aneurysm in the observational group

Background Coronary artery aneurysm (CAA) is occasionally detected on a small percentage of coronary angiography or multi-detector computed tomography (MDCT). CAA itself is considered benign entity despite the potential risks of rupture, thromboembolism, and compression of surrounding structures. However, the optimal management including other vascular comorbidity has yet to be fully clarified. Objective The aim of this study was to evaluate cardiovascular events in the patients with CAA in the observational group. Methods Between January 2010 and August 2015, 48 CAAs were identified in 37 patients out of consecutive 10,010 patients (0.37%) by MDCT. Twenty-eight patients treated conservatively were included in this study. Their major adverse cardiovascular events (MACE) were evaluated retrospectively: death, non-fatal myocardial infarction (MI), revascularizations; coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI), and other vascular events. Results The average age was 62.0 ± 15.5 year sold, and median follow-up period was 49.6 months (IQR 23.6 to 78.1). Mean CAA diameter was 7.5 ± 2.8 mm. Twenty-two MACE occurred in 15 patients (53.6%): 1 sudden death, 4 MI, 1 CABG for CAA, 3 PCI for CAA, 7 PCI for non-CAA lesions, and 6 other vascular treatments for aorta and cerebral and peripheral artery. Follow-up MDCT was performed for 22 CAAs in 16 patients. In 9 CAAs of them, the maximal diameter increased significantly (Δ diameter: 1.5 ± 1.1 mm). Conclusions Presence of CAA may be associated with adverse vascular events including non-coronary diseases. This study could suggest the management for CAA should include the evaluation of not only CAA itself but also other vascular diseases.

SIGNIFICANCE OF 123I-BMIPP-SCINTIGRAPHY IN THE RECOVERY OF LEFT VENTRICULAR SYSTOLIC DYSFUNCTION IN TAKOTSUBO CARDIOMYOPATHY: INSIGHT FROM THE NEW TAKOTSUBO BMIPP REGISTRY

Background: Takotsubo cardiomyopathy (TCM) is notable for reversible left ventricular (LV) systolic dysfunction in a short-term whereas it is well-known long-duration or persistent wall-motion abnormality is observed in some cases. However, its prevalence and predictor have yet to be fully-clarified