Comparison of Image Quality, Diagnostic Accuracy and Radiation Dose Between Flash Model and Retrospective ECG-Triggered Protocols in Dual Source Computed Tomography (DSCT) in Congenital Heart Diseases

Image quality and radiation dose of dual source high pitch computed tomography in pediatric congenital heart disease

To explore the image quality and radiation dose of dual source high-pitch cardiac computed tomography with tailored contrast injection protocols for pediatric congenital heart disease patients (CHD). In total, 27 infants with CHD (median age 109 days [IQR 6-199]) were retrospectively analyzed regarding dose length product (DLP) and effective dose (ED) after undergoing cardiothoracic CT imaging. Scan parameters were adjusted on a dual source/detector CT (DSCT) to minimize radiation dose while maintaining adequate quality. Image acquisition was performed at 70% of the R-R interval. Dose reducing measures included prospective electrocardiogram gating, utilizing slow injection velocities and foregoing bolus tracking during contrast injection. Image quality was assessed for artefacts, vessel definition, and noise on a 5-point scale (1 non-diagnostic, 5 excellent). Series were scored on a 0-to-3-point scale regarding answered clinical questions (0 non-diagnostic, 3 all clinical questions could be answered). The median DLP was 5.2 mGy*cm (IQR 3.5-7.8) leading to a median ED of 0.20 mSv (IQR 0.14-0.30). On average the acquired images scored 13.3 ± 2.1 (SD) out of a maximum 15 points with an intraclass correlation coefficient (ICC) of 0.94. All acquired series were able to fully answer all clinical questions scoring maximum points (ICC 1.0). Dual source high pitch CT protocols combined with custom contrast agent injection protocols in pediatric patients with CHD delivered sufficiently high diagnostic imaging quality combined with low submilisievert radiation doses. Prospective high pitch imaging is a reliable method for depiction of cardiac anatomy even in very young pediatric CHD patients with elevated heart rates.

Evaluation of ECG-gated and Fast Low-Angle Shot (FLASH) Dual Source Computed Tomography Scanning Protocols for Transcatheter Aortic Valve Replacement

BACKGROUND

Transcatheter aortic valve replacement (TAVR) procedural success relies heavily on volumetric reconstruction imaging, particularly ECG-gated multi-detector row computed tomography. We postulated that single examination using fast low-angle shot (FLASH) dual source CT scanning (DS-CTA) could provide lower dose than ECG-gated CTA while maintaining the image quality.

METHODS

In this single-centre cohort study, all patients who underwent ECG-gated and FLASH DS-CTA were evaluated. Volumetric reconstructions were performed for both ECG-gated and FLASH DS-CTA to obtain nonsagittal views of the structures. ECG-gated cardiac CT was obtained to evaluate the aortic annular size while FLASH DS-CTA was obtained to examine the aortic and iliac vasculature as part of TAVR imaging protocol. We evaluated measures of aortic annulus, coronaries and sinus of Valsalva using ECG-gated and FLASH DS-CTA scanning protocols. Image quality assessments were performed using aortic root region-of-interest signal-to-noise ratio.

RESULTS

A total of 130 patients (mean age 81.5 ± 9.2 years, 46.2% female, and 99.2% white) underwent both ECG-gated CT and FLASH DS-CTA. There were excellent correlations between aortic annular area (R² = 0.934) and aortic annular perimeter (R² = 0.923) measured by the two protocols. Only 2 (1.5%) patients had >10% difference between aortic annular measurements by ECG-gated and FLASH DS-CTA, while none of the patients had a >10% difference between aortic annular perimeter measured by ECG-gated and FLASH DS-CT scans. There was no significant difference in signal-to-noise ratio between the two methods (mean difference 13.4; 95% CI -2.1-28.8, p = 0.09). There was significantly lower radiation dose for FLASH DS-CTA than ECG-gated CT scan (mean dose-length product difference 404.38; 95% CI 328.9-479.87, p <0.001). The measurements by the two scans led to the same transcatheter valve size selection in majority of the 128 (98.5%) patients by balloon expandable valve sizing recommendations and 130 (100%) of patients by self-expanding valve sizing recommendations.

CONCLUSION

Overall, FLASH DS-CTA and ECG-gated CT scans provided comparable image quality and aortic annular dimensions for pre-TAVR evaluation. DS-CTA additionally provided the necessary angiographic imaging of the aorta and peripheral access vessels while still maintaining a lower radiation dose. We propose that a single non-ECG gated FLASH DS-CTA could be utilized to provide all the necessary pre-TAVR imaging information without a gated CT scan.

Computed tomography portography of patients with cirrhosis with normal body mass index: Comparison between low-tube-voltage CT with low contrast agent dose and conventional CT

This study is to investigate the computed tomography (CT) image quality of the low- tube-voltage protocol with low contrast agent dose.CT portography was performed in 118 cirrhosis patients with body mass index (BMI) less than 25 kg/m under 2 protocols: Protocol A, tube voltage of 90 kVp/395 mAs and contrast agent dosage of 1.2 mL/kg, and, Protocol B, tube voltage of 120 kVp/200 mAs and contrast agent dosage of 1.5 mL/kg.The number of patients in each protocol was 59. The CT value noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in portal veins was comparatively analyzed between the 2 protocols. The subjective image quality was further assessed on 5-point scales. Radiation dose was also recorded and statistical analysis was performed.The CT value, CNR, and SNR of the images were higher at 90 kVp than those at 120 kVp (P < .05). There was no significant difference in image noise between the 2 protocols (P > .05). The CT dose index volume, dose-length product, and effective dose at 90 kVp were 18.2%, 16.0%, and 16.0% less than that at 120 kVp, respectively. There was no difference in image quality score between the 2 protocols (P > .05). The average amount of contrast agent was decreased by 17.8% when the 90 kVp protocol was used.CT portography at 90 kVp combined with low-dosage contrast agent leads to a significant reduction in radiation dose and improved SNR and CNR, without deterioration of image quality.

Computed tomography in paediatric heart disease

Cardiovascular CT (CCT) is an important imaging modality in congenital and acquired paediatric heart disease. Technological advances have resulted in marked improvements in spatial and temporal resolution of CCT with a concomitant increase in speed of data acquisition and a decrease in radiation dose. This has elevated CCT from being sparingly used to an essential diagnostic tool in the daily multimodality imaging practice alongside echocardiography, cardiovascular MR and invasive angiography. The application of CCT in paediatric congenital and acquired heart disease can be both technically and diagnostically challenging. This review highlights important considerations for current state of the art CCT across the spectrum of heart disease encountered in children.