Feasibility of aortic valve assessment with low dose prospectively triggered adaptive systolic (PTAS) cardiac computed tomography angiography

Principles and applications of dual source CT

This article describes the technical principles and clinical applications of dual source CT. A dual source CT (DSCT) is a CT system with two x-ray tubes and two detectors at an angle of approximately 90°. Both measurement systems acquire CT scan data simultaneously at the same anatomical level of the patient (same z-position). DSCT provides temporal resolution of approximately a quarter of the gantry rotation time for cardiac, cardio-thoracic and pediatric imaging. Successful imaging of the heart and the coronary arteries at high and variable heart rates has been demonstrated. DSCT systems can be operated at twice the spiral pitch of single source CT systems (up to pitch 3.2). The resulting high table speed is beneficial for pediatric applications and fast CT angiographic scans, e. g. of the aorta or the extremities. Operating both X-ray tubes at different tube potential (kV) enables the acquisition of dual energy data and the corresponding applications such as monoenergetic imaging and computation of material maps. Spectral separation can be improved by different filtration of the X-ray beams of both X-ray tubes. As a downside, DSCT systems have to cope with some challenges, among them the limited size of the second measurement system, and cross-scattered radiation.

Potential impact of dynamic automated CT aortic annular measurements on outcomes for transcatheter aortic valve replacement sizing

To determine the potential impact of automated computed tomography (CT) software used for aortic annular sizing for transcatheter aortic valve replacement (TAVR) on paravalvular leak (PVL) and major adverse cardiovascular events (MACE) as compared to standard CT manual measurement. In 60 TAVR patients (84 ± 7 years, 60% male), we evaluated the preprocedural CT scans. For the standard manual measurement, we measured the perimeter and area from a single cardiac phase deemed to be of maximum systolic opening. Valve type and size were determined by a multidisciplinary TAVR team per clinical routine. From the dynamic automated software, we determined the aortic annular perimeter and area as the maximum value from an entire cardiac cycle. Valve size was readjudicated by a blinded interventional cardiologist who was provided with valve type and automated values. Clinical endpoints were adjudicated for presence of at least mild PVL and MACE at 30 days. There were 16 (28%) patients with PVL and 4 (7%) with 30-day MACE. When reclassifying valve size using dynamic automated values, 12 (20%) patients were undersized and 3 (5%) patients were oversized. Undersized patients were more likely to have mild-to-moderate PVL at 30 days (27% vs 4%, p = 0.04) than those not undersized. Of the 5 (45%) undersized patients with at least mild PVL, all were balloon-expandable valves. Automated dynamic CT annular measurements have the potential to reclassify patients with PVL with larger TAVR valve size, particularly balloon-expandable valves.

Performance of Dynamic Automated CT Annular Measurements Compared to Standard Manual Measurements for Transcatheter Aortic Valve Replacement Sizing

Purpose

We sought to determine the performance of an automated computed tomography (CT) software that provides dynamic annular measurements of all available cardiac phases for transcatheter aortic valve replacement (TAVR) sizing as compared to the standard single manual measurement.

Materials and Methods

In 60 TAVR patients (84±7 years, 60% male) who underwent pre-procedural CT scans, we measured the aortic annular diameters, perimeter, and area using (1) the dynamic automated CT measurements and (2) standard single manual measurement from the cardiac phase of maximum systolic opening by visual estimate.

Results

The automated software was successful in providing annular measurements in 43/60 (72%) of cases, with the remainder requiring semi-automated contours. The maximum dynamic automated values were predominantly in systole (46/60[77%] for diameter, 44/60[73%] for perimeter, 48/60[80%] for area), and was a different phase from the standard manual phase in 46/60 (77%) cases. The maximum dynamic automated annular values were larger than the standard manual values measured (Δdiameter 0.35 mm, p=0.04; Δperimeter 1.71 mm, p<0.001; Δarea 15.6 mm², p<0.001). When comparing standard manual to the same phase by automated measurements, while there was no difference in annular mean diameter (p=0.80), perimeter and area were larger with the automated measurements (Δperimeter 0.95 mm, p=0.002; Δarea 10.8 mm², p=0.03). However, the maximum automated measurements were consistently larger than the same phase automated measurements (Δdiameter 0.13 mm, p<0.001; Δperimeter 0.42 mm, p<0.001; Δarea 4.4 mm², p<0.001).

Conclusions

Automated maximum dynamic CT annular measurements provide larger values than standard manual and same phase automated measurements.

Performance of Dynamic Automated CT Annular Measurements Compared to Standard Manual Measurements for Transcatheter Aortic Valve Replacement Sizing

PURPOSE

We sought to determine the performance of an automated computed tomography (CT) software that provides dynamic annular measurements of all available cardiac phases for transcatheter aortic valve replacement (TAVR) sizing as compared to the standard single manual measurement.

MATERIALS AND METHODS

In 60 TAVR patients (84±7 years, 60% male) who underwent pre-procedural CT scans, we measured the aortic annular diameters, perimeter, and area using (1) the dynamic automated CT measurements and (2) standard single manual measurement from the cardiac phase of maximum systolic opening by visual estimate.

RESULTS

The automated software was successful in providing annular measurements in 43/60 (72%) of cases, with the remainder requiring semi-automated contours. The maximum dynamic automated values were predominantly in systole (46/60[77%] for diameter, 44/60[73%] for perimeter, 48/60[80%] for area), and was a different phase from the standard manual phase in 46/60 (77%) cases. The maximum dynamic automated annular values were larger than the standard manual values measured (Δdiameter 0.35 mm, p=0.04; Δperimeter 1.71 mm, p<0.001; Δarea 15.6 mm², p<0.001). When comparing standard manual to the same phase by automated measurements, while there was no difference in annular mean diameter (p=0.80), perimeter and area were larger with the automated measurements (Δperimeter 0.95 mm, p=0.002; Δarea 10.8 mm², p=0.03). However, the maximum automated measurements were consistently larger than the same phase automated measurements (Δdiameter 0.13 mm, p<0.001; Δperimeter 0.42 mm, p<0.001; Δarea 4.4 mm², p<0.001).

CONCLUSIONS

Automated maximum dynamic CT annular measurements provide larger values than standard manual and same phase automated measurements.

Organ Doses and Radiation Risk of Computed Tomographic Coronary Angiography in a Clinical Patient Population: How Do Low-Dose Acquisition Modes Compare?

OBJECTIVE

To compare the organ doses and lifetime-attributable risk of cancer for electrocardiogram-triggered sequential and high-pitch helical scanning in a clinical patient population.

METHODS

Phantom thermoluminiscence dosimeter measurements were used as a model for the organ dose assessment of 314 individual patients who underwent coronary computed tomographic angiography. Patient-specific lifetime-attributable cancer risks were calculated.

RESULTS

Phantom measurements showed that heart rate had a significant influence on the delivered radiation exposure in sequential mode, and calcium scoring and contrast bolus tracking scans make a nonnegligible contribution to patients' dose. Therefore, they should be taken into account for patients' organ dose estimations. Median cancer induction risks are low, with 0.008% (0.0016%) and 0.022% (0.056%) for high-pitch and sequential scanning for men (women), respectively.

CONCLUSIONS

The use of high-pitch helical scanning leads to 65% and 72% lower lifetime-attributable risk values for men and women, respectively, compared with sequential scanning.

Imaging of cardiac valves by computed tomography

This paper describes "how to" examine cardiac valves with computed tomography, the normal, diseased valves, and prosthetic valves. A review of current scientific literature is provided. Firstly, technical basics, "how to" perform and optimize a multislice CT scan and "how to" interpret valves on CT images are outlined. Then, diagnostic imaging of the entire spectrum of specific valvular disease by CT, including prosthetic heart valves, is highlighted. The last part gives a guide "how to" use CT for planning of transcatheter aortic valve implantation (TAVI), an emerging effective treatment option for patients with severe aortic stenosis. A special focus is placed on clinical applications of cardiac CT in the context of valvular disease.