Comparison of sequential and high-pitch-spiral coronary CT-angiography: image quality and radiation exposure

Atherosclerosis evaluation and cardiovascular risk estimation using coronary computed tomography angiography

Clinical risk scores based on traditional risk factors of atherosclerosis correlate imprecisely to an individual's complex pathophysiological predisposition to atherosclerosis and provide limited accuracy for predicting major adverse cardiovascular events (MACE). Over the past two decades, computed tomography scanners and techniques for coronary computed tomography angiography (CCTA) analysis have substantially improved, enabling more precise atherosclerotic plaque quantification and characterization. The accuracy of CCTA for quantifying stenosis and atherosclerosis has been validated in numerous multicentre studies and has shown consistent incremental prognostic value for MACE over the clinical risk spectrum in different populations. Serial CCTA studies have advanced our understanding of vascular biology and atherosclerotic disease progression. The direct disease visualization of CCTA has the potential to be used synergistically with indirect markers of risk to significantly improve prevention of MACE, pending large-scale randomized evaluation.

Optimization of Kernel Type and Sharpness Level Improves Objective and Subjective Image Quality for High-Pitch Photon Counting Coronary CT Angiography

(1) Background: Photon-counting detector (PCD) CT offers a wide variety of kernels and sharpness levels for image reconstruction. The aim of this retrospective study was to determine optimal settings for coronary CT angiography (CCTA). (2) Methods: Thirty patients (eight female, mean age 63 ± 13 years) underwent PCD-CCTA in a high-pitch mode. Images were reconstructed using three different kernels and four sharpness levels (Br36/40/44/48, Bv36/40/44/48, and Qr36/40/44/48). To analyze objective image quality, the attenuation, image noise, contrast-to-noise ratio (CNR), and vessel sharpness were quantified in proximal and distal coronaries. For subjective image quality, two blinded readers assessed image noise, visually sharp reproduction of coronaries, and the overall image quality using a five-point Likert scale. (3) Results: Attenuation, image noise, CNR, and vessel sharpness significantly differed across kernels (all p < 0.001), with the Br-kernel reaching the highest attenuation. With increasing kernel sharpness, image noise and vessel sharpness increased, whereas CNR continuously decreased. Reconstruction with Br-kernel generally had the highest CNR (Br > Bv > Qr), except Bv-kernel had a superior CNR at sharpness level 40. Bv-kernel had significantly higher vessel sharpness than Br- and Qr-kernel (p < 0.001). Subjective image quality was rated best for kernels Bv40 and Bv36, followed by Br36 and Qr36. (4) Conclusion: Reconstructions with kernel Bv40 are beneficial to achieve optimal image quality in spectral high-pitch CCTA using PCD-CT.

Influence of heart rate and heart rate variability on the feasibility of ultra-fast, high-pitch coronary photon-counting computed tomography angiography

Coronary computed tomography angiography has become a mainstay in diagnosing coronary artery disease and is increasingly used in screening symptomatic patients. Recently, photon-counting computed tomography (PCCT) has been introduced into clinical practice, offering higher spatial and temporal resolution. As the applied radiation dose is highly dependent on the choice of scan mode and is lowest using the ultra-fast high-pitch (FLASH) mode, guidelines for their application are needed. From a retrospective study investigating the properties of a novel photon-counting computed tomography, all patients who underwent FLASH-mode PCCT angiography were selected between January and April 2022. This resulted in a study population of 46 men and 27 women. We recorded pre- and intrascan ECG readings and calculated heart rate (maximum heart rate 73 bpm) as well heart rate variability (maximum HRV 37 bpm) as measured by the standard deviation of the heart rate. Diagnostic quality and motion artifacts scores were recorded for each coronary artery segment by consensus between two readers. We found a highly significant association between heart rate variability and image quality (p < 0.001). The heart rate itself was not independently associated with image quality. Both heart rate and heart rate variability were significantly associated with the presence of motion artifacts in a combined model. Scan heart rate variability-but not heart rate itself-is a highly significant predictor of reduced image quality on high-pitch coronary photon-counting computed tomography angiography. This may be due to better scanner architecture and an increased temporal resolution compared to conventional energy-integrating detector computed tomography, which has to be addressed in a comparison study in the future.

Is There Any Improvement in Image Quality in Obese Patients When Using a New X-ray Tube and Deep Learning Image Reconstruction in Coronary Computed Tomography Angiography?

Deep learning image reconstruction (DLIR) is a technique that should reduce noise and improve image quality. This study assessed the impact of using both higher tube currents as well as DLIR on the image quality and diagnostic accuracy. The study consisted of 51 symptomatic obese (BMI > 30 kg/m2) patients with low to moderate risk of coronary artery disease (CAD). All patients underwent coronary computed tomography angiography (CCTA) twice, first with the Revolution CT scanner and then with the upgraded Revolution Apex scanner with the ability to increase tube current. Images were reconstructed using ASiR-V 50% and DLIR. The image quality was evaluated by an observer using a Likert score and by ROI measurements in aorta and the myocardium. Image quality was significantly improved with the Revolution Apex scanner and reconstruction with DLIR resulting in an odds ratio of 1.23 (p = 0.017), and noise was reduced by 41%. A total of 88% of the image sets performed with Revolution Apex + DLIR were assessed as good enough for diagnosis compared to 69% of the image sets performed with Revolution Apex/CT + ASiR-V. In obese patients, the combination of higher tube current and DLIR significantly improves the subjective image quality and diagnostic utility and reduces noise.

Coronary computed tomography angiography (CCTA): effect of bolus-tracking ROI positioning on image quality

Objectives

The aim of the study was to evaluate the effect of bolus-tracking ROI positioning on coronary computed tomography angiography (CCTA) image quality.

Methods

In this retrospective monocentric study, all patients had undergone CCTA by step-and-shoot mode to rule out coronary artery disease within a cohort at intermediate risk. Two groups were formed, depending on ROI positioning (left atrium (LA) or ascending aorta (AA)). Each group contained 96 patients. To select pairs of patients, propensity score matching was used. Image quality with regard to coronary arteries as well as pulmonary arteries was evaluated using quantitative and qualitative scores.

Results

In terms of the coronary arteries, there was no significant difference between both groups using quantitative (SNR AA 14.92 vs. 15.46; p = 0.619 | SNR LM 19.80 vs. 20.30; p = 0.661 | SNR RCA 24.34 vs. 24.30; p = 0.767) or qualitative scores (4.25 vs. 4.29; p = 0.672), respectively. With regard to pulmonary arteries, we found significantly higher quantitative (SNR RPA 8.70 vs. 5.89; p < 0.001 | SNR LPA 9.06 vs. 6.25; p < 0.001) and qualitative scores (3.97 vs. 2.24; p < 0.001) for ROI positioning in the LA than for ROI positioning in the AA.

Conclusions

ROI positioning in the LA or the AA results in comparable image quality of CT coronary arteriography, while positioning in the LA leads to significantly higher image quality of the pulmonary arteries. These results support ROI positioning in the LA, which also facilitates triple-rule-out CT scanning.

Key Points

• ROI positioning in the left atrium or the ascending aorta leads to comparable image quality of the coronary arteries.

• ROI positioning in the left atrium results in significantly higher image quality of the pulmonary arteries.

• ROI positioning in the left atrium is feasible to perform triple-rule-out CTA.

In vivo radiation dosimetry and image quality of turbo-flash and retrospective dual-source CT coronary angiography

PURPOSE

To compare measured radiation dose (MD), estimated radiation dose (ED) and image quality in coronary computed tomography between turbo-flash (TFP) and retrospective protocol (RP) and correlate MD with size-specific dose estimates (SSDE).

MATERIALS AND METHODS

In this prospective study, we selected 68 patients (mean age, 59.2 ± 9.7 years) undergoing 192 × 2 dual-source CT (SOMATOM Force, Siemens) to rule out coronary artery disease. Thirty-one underwent TFP and 37 RP. To evaluate in vivo MD, thermoluminescent dosimeters were placed, superficially, at thyroid and heart level, left breast areola and left hemi-thorax. MD in each site, and ED parameters, such as volume CT dose index (CTDI_vol), SSDE, dose length product (DLP), effective dose (E), were compared between two protocols with a t test. Image quality was compared between two protocols. Inter-observer agreement was evaluated with a kappa coefficient (k). In each protocol, MD was correlated with SSDE using a Pearson coefficient (r).

RESULTS

Comparing TFP and RP, MD at thyroid (1.43 vs. 2.58 mGy; p = 0.0408), heart (3.58 vs. 28.72 mGy; p < 0.0001), left breast areola (3.00 vs. 24.21 mGy; p < 0.0001) and left hemi-thorax (2.68 vs. 24.03 mGy; p < 0.0001), CTDI_vol, SSDE, DLP and E were significantly lower. Differences in image quality were not statistically significant. Inter-observer agreement was good (k = 0.796) in TFP and very good (k = 0.817) in RP. MD and SSDE excellently correlated with TFP (r = 0.9298, p < 0.0001) and RP (r = 0.9753, p < 0.0001).

CONCLUSIONS

With TFP, MD, CTDI_vol, SSDE, DLP and E were significantly lower, than with RP. Image quality was similar between two protocols. MD correlated excellently with SSDE in each protocol.