Simultaneous Assessment of Left Ventricular Function and Coronary Artery Anatomy by Third-generation Dual-source Computed Tomography Using a Low Radiation Dose

Potential for Dose Reduction in CT-Derived Left Ventricular Ejection Fraction: A Simulation Study

BACKGROUND

Measuring left ventricular ejection fraction (LVEF) is important for detecting heart failure, e.g., in treatment with potentially cardiotoxic chemotherapy. MRI is considered the reference standard for LVEF, but availability may be limited and claustrophobia or metal implants still present challenges. CT has been shown to be accurate and would be advantageous, as LVEF could be measured in conjunction with routine chest-abdomen-pelvis oncology CT. However, the use of CT is not recommended due to the excessive radiation dose. This study aimed to explore the potential for dose reduction using simulation. Using an anthropomorphic heart phantom scanned at 13 dose levels, a noise simulation algorithm was developed to introduce controlled Poisson noise. Filtered backprojection parameters were iteratively tested to minimise differences in myocardium-to-ventricle contrast/noise ratio, as well as structural similarity index (SSIM) differences between real and simulated images at all dose levels. Fifty-one clinical CT coronary angiographies, scanned with full dose through end-systolic and -diastolic phases, were located retrospectively. Using the developed algorithm, noise was introduced corresponding to 25, 10, 5 and 2% of the original dose level. LVEF was measured using clinical software (Syngo.via VB50) with papillary muscles in and excluded from the LV volume. At each dose level, LVEF was compared to the 100% dose level, using Bland-Altman analysis. The effective dose was calculated from DLP using a conversion factor of 0.026 mSv/mGycm.

RESULTS

In the clinical images, mean CTDIvol and DLP were 47.1 mGy and 771.9 mGycm, respectively (effective dose 20.0 mSv). Measurements with papillary muscles excluded did not exhibit statistically significant LVEF bias to full-dose images at 25, 10 and 5% simulated dose. At 2% dose, a significant bias of 4.4% was found. With papillary muscles included, small but significant biases were found at all simulated dose levels.

CONCLUSION

Provided that measurements are performed with papillary muscles excluded from the LV volume, the dose can be reduced by a factor of 20 without significantly affecting LVEF measurements. This corresponds to an effective dose of 1 mSv. CT can potentially be used for LVEF measurement with minimal excessive radiation.

CT coronary angiography as an alternative imaging method to ascertain cardiac output and its correlation with echocardiography

AIM

To assess the feasibility and accuracy of cardiac output (CO) obtained using a test bolus in patients scanned with single-source prospective-gated cardiac computed tomography (CT), and comparing it with CO obtained from unenhanced two-dimensional (2D) echocardiography using biplane Simpson's method.

MATERIALS AND METHODS

In the present study, 100 patients with a mean age of 55 ± 12 years who underwent coronary CT angiography with prospective electrocardiogram (ECG)-gated CT in which the scan delay was evaluated using a test bolus. The time-attenuation curves obtained from the test bolus were used to calculate the CO of the patients. The CO obtained was then compared with that obtained after follow-up 2D echocardiography using biplane modified Simpson method.

RESULTS

Linear regression was calculated between the CO and contrast enhancement: CO = -0.16(HUmax) + 7.65. The study showed good correlation between the two methods with r=0.77, p<0.001. On Bland-Altman analysis, no significant difference was noted between the two methods.

CONCLUSION

This less researched method for CO estimation appears feasible; however, the clinical usefulness of this parameter is uncertain in absence of further clinical and reference standard validation.

Cyclothymic affective temperament is independently associated with left ventricular hypertrophy in chronic hypertensive patients

OBJECTIVE

Affective temperaments (depressive, anxious, irritable, hyperthymic, and cyclothymic) are regarded as the stable core of personality and when present in their dominant form, are considered subclinical manifestations and high-risk states for various affective disorders. Furthermore, cumulating evidence supports their relationship with cardiovascular diseases. Our aim was to assess the association between affective temperaments and left ventricular hypertrophy (LVH) in chronic hypertensive patients.

METHODS

In the present cross-sectional study, 296 patients referred to coronary computed tomography angiography (CCTA) due to suspected coronary artery disease were analyzed. All patients completed the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego Autoquestionnaire (TEMPS-A). Left ventricular mass was quantified by CCTA and indexed to the body surface area (LVMi). Logistic regression analysis was used to identify predictors of LVH (men: ≥67.2 g/m² and women: ≥54.7 g/m²).

RESULTS

Among our patient cohort (mean age: 59.4 ± 10.6, 44.9% female), the median LVM and LVMi were 115.5 [88.4-140.7] g and 58.4 [47.4-64.2] g/m², respectively. Elevated BMI (OR = 1.04 CI: 1.01-1.10, p = 0.04) and cyclothymic affective temperament scores (OR = 1.06 CI: 1.00-1.12, p = 0.04) significantly increased the odds of LVH in multivariate logistic regression analysis.

CONCLUSION

Assessment of affective temperaments may allow for the identification of chronic hypertensive patients with elevated risk for LVH as a potential target for earlier primary intervention.

Anomalous Origin of the Coronary Artery from the Pulmonary Artery in Children and Adults: A Pictorial Review of Cardiac Imaging Findings

Anomalous origin of the coronary artery from the pulmonary artery is a rare and potentially fatal congenital heart defect. Up to 90% of infants with an anomaly involving the left coronary artery die within the first year of life if left untreated. Patients who survive beyond infancy are at risk of sudden cardiac death. Cardiac CT and MRI are increasingly being used for the accurate diagnosis of this anomaly for prompt surgical restoration of the dual coronary artery system. Moreover, life-long imaging surveillance after surgery is necessary for these patients. In this pictorial review, multimodal cardiac imaging findings of this rare and potentially fatal coronary artery anomaly are comprehensively discussed, and representative images are provided to facilitate the understanding of this anomaly.

Radiation dose, contrast enhancement, image noise and heart rate variability of ECG-gated CT volumetry using 3D threshold-based segmentation: Comparison between conventional single scan and dual focused scan methods

OBJECTIVE

To compare radiation dose, contrast enhancement, image noise and heart rate variability in electrocardiography (ECG)-gated computed tomography (CT) ventricular volumetry using a three-dimensional (3D) threshold-based segmentation between the conventional single scan and dual focused scan methods in patients with congenital heart disease.

METHODS

After matching for age, sex, heart rate during the CT examination, and tube voltage, 96 patients (age range, 7 - 36 years; male:female = 63:33) who underwent ECG-gated CT volumetry using a 3D threshold-based segmentation, were divided into 32 patients who underwent a conventional single scan (group 1) and 64 who underwent dual focused scans (group 2). CT radiation dose, contrast enhancement, image noise, and heart rate variability were compared between the two groups.

RESULTS

Volume CT dose index, dose-length product, and effective dose estimates, in group 1 were significantly higher than those in group 2 (28.4 ± 24.6 mGy vs. 9.7 ± 4.5 mGy, 636.5 ± 572.9 mGy cm vs. 379.5 ± 192.4 mGy cm, 8.9 ± 8.0 mSv vs. 5.3 ± 2.7 mSv, 8.2 ± 6.4 mSv vs. 5.0 ± 2.2 mSv, respectively; p values < 0.019). No significant differences in right and left ventricular contrast enhancement were found between the two groups (470.2 ± 152.4 HU vs. 481.0 ± 139.2 HU and 428.6 ± 97.8 HU vs. 429.3 ± 106.7 HU, respectively; p values > 0.05). Image noise measured in the air showed no significant differences between groups 1 and 2 (5.6 ± 1.9 HU vs. 5.5 ± 1.1 HU; p >  0.05). The proportion of heart rate variability ≥ 20 beats per minute in group 1 (15.6 %, 5/32) was significantly higher than that in group 2 (3.1 %, 2/64; p <  0.040).

CONCLUSION

Compared with the conventional single scan method, the dual focused scan method can provide a lower radiation dose with comparable contrast enhancement and image noise for ECG-gated CT ventricular volumetry using a 3D threshold-based segmentation in patients with congenital heart disease.