Quantification of Aortic Valve Stenosis: Head-to-Head Comparison of 64-Slice Spiral Computed Tomography With Transesophageal and Transthoracic Echocardiography and Cardiac Catheterization

Cardiac gated multidetector computed tomography (MDCT) to determine valvular leaflet thrombosis and leaflet restriction

The evaluation of patients following aortic valve replacement has evolved, with multiple imaging modalities available that complement each other and permit better and prompt delineation of specific structural or functional valve complications. Multidetector computed tomography (MDCT) is one of the diagnostic modalities with significant technologic advancements that have made possible to evaluate high detail of the moving heart. The ability to deliver three-dimensional and multiplanar dynamic imaging with fine detail has demonstrated the technique is well suited to investigate valve complications. In this review article, we focus on some of the most contributing roles of MDCT in the diagnosis of complications associated with valvular pathology.

Imaging diagnosis of aortic stenosis

Aortic valve stenosis (AS) is the commonest primary valve disorder with increasing prevalence with age. Trans-thoracic echocardiogram is the main imaging technique used to diagnose AS, but discrepancy in diagnosis has been described in almost one third of cases. Other imaging methods, particularly electrocardiogram (ECG)-gated computed tomography, have now emerged to further clarify the diagnosis of AS by both demonstrating the degree of calcification in the valve as well as aortic valve area. Cardiac magnetic resonance imaging allows accurate quantification of ventricular function and evaluation of the myocardium. This paper provides a comprehensive review of the diagnosis of AS for the radiologist.

Semiautomatic, Quantitative Measurement of Aortic Valve Area Using CTA: Validation and Comparison with Transthoracic Echocardiography

Objective. The aim of this work was to develop a fast and robust (semi)automatic segmentation technique of the aortic valve area (AVA) MDCT datasets. Methods. The algorithm starts with detection and cropping of Sinus of Valsalva on MPR image. The cropped image is then binarized and seed points are manually selected to create an initial contour. The contour moves automatically towards the edge of aortic AVA to obtain a segmentation of the AVA. AVA was segmented semiautomatically and manually by two observers in multiphase cardiac CT scans of 25 patients. Validation of the algorithm was obtained by comparing to Transthoracic Echocardiography (TTE). Intra- and interobserver variability were calculated by relative differences. Differences between TTE and MDCT manual and semiautomatic measurements were assessed by Bland-Altman analysis. Time required for manual and semiautomatic segmentations was recorded. Results. Mean differences from TTE were −0.19 (95% CI: −0.74 to 0.34) cm² for manual and −0.10 (95% CI: −0.45 to 0.25) cm² for semiautomatic measurements. Intra- and interobserver variability were 8.4 ± 7.1% and 27.6 ± 16.0% for manual, and 5.8 ± 4.5% and 16.8 ± 12.7% for semiautomatic measurements, respectively. Conclusion. Newly developed semiautomatic segmentation provides an accurate, more reproducible, and faster AVA segmentation result.

Trends in the utilization of computed tomography and cardiac catheterization among children with congenital heart disease

Background/Purpose

Pediatric cardiac computed tomography (CT) is a noninvasive imaging modality used to clearly demonstrate the anatomical detail of congenital heart diseases. We investigated the impact of cardiac CT on the utilization of cardiac catheterization among children with congenital heart disease.

Methods

The study sample consisted of 2648 cardiac CT and 3814 cardiac catheterization from 1999 to 2009 for congenital heart diseases. Diagnoses were categorized into 11 disease groups. The numbers of examination, according to the different modalities, were compared using temporal trend analyses. The estimated effective radiation doses (mSv) of CT and catheterization were calculated and compared.

Results

The number of CT scans and interventional catheterizations had a slight annual increase of 1.2% and 2.7%, respectively, whereas that of diagnostic catheterization decreased by 6.2% per year. Disease groups fell into two categories according to utilization trend differences between CT and diagnostic catheterization. The increased use of CT reduces the need for diagnostic catheterization in patients with atrioventricular connection disorder, coronary arterial disorder, great vessel disorder, septal disorder, tetralogy of Fallot, and ventriculoarterial connection disorder. Clinicians choose either catheterization or CT, or both examinations, depending on clinical conditions, in patients with semilunar valvular disorder, heterotaxy, myocardial disorder, pericardial disorder, and pulmonary vein disorder. The radiation dose of CT was lower than that of diagnostic cardiac catheterization in all age groups.

Conclusion

The use of noninvasive CT in children with selected heart conditions might reduce the use of diagnostic cardiac catheterization. This may release time and facilities within the catheterization laboratory to meet the increasing demand for cardiac interventions.

Automatic vs semi-automatic global cardiac function assessment using 64-row CT

OBJECTIVE

Global cardiac function assessment using multidetector CT (MDCT) is time-consuming. Therefore we sought to compare an automatic software tool with an established semi-automatic method.

METHODS

A total of 36 patients underwent CT with 64 × 0.5 mm detector collimation, and global left ventricular function was subsequently assessed by two independent blinded readers using both an automatic region-growing-based software tool (with and without manual adjustment) and an established semi-automatic software tool. We also analysed automatic motion mapping to identify end-systole.

RESULTS

The time needed for assessment using the semi-automatic approach (12:12 ± 6:19 min) was reduced by 75-85% with the automatic software tool (unadjusted, 01:34 ± 0:29 min, adjusted, 02:53 ± 1:19 min; both p<0.001). There was good correlation (r=0.89; p<0.001) for the ejection fraction (EF) between the adjusted automatic (58.6 ± 14.9%) and the semi-automatic (58.0 ± 15.3%) approaches. Also the manually adjusted automatic approach led to significantly smaller limits of agreement than the unadjusted automatic approach for end-diastolic volume (±36.4 ml vs ±58.5 ml, p>0.05). Using motion mapping to automatically identify end-systole reduced analysis time by 95% compared with the semi-automatic approach, but showed inferior precision for EF and end-systolic volume.

CONCLUSION

Automatic function assessment using MDCT with manual adjustment shows good agreement with an established semi-automatic approach, while reducing the analysis by 75% to less than 3 min. This suggests that automatic CT function assessment with manual correction may be used for fast, comfortable and reliable evaluation of global left ventricular function.

Magnetic resonance evaluation of brain metastases from systemic malignances with two doses of gadobutrol 1.0 m compared with gadoteridol: a multicenter, phase ii/iii study in patients with known or suspected brain metastases

OBJECTIVES

To determine the efficacy and safety of 2 doses of gadobutrol 1.0 M (0.1 and 0.2 mmol/kg body weight [BW]), compared with gadoteridol 0.5 M (0.2 mmol/kg BW), in contrast-enhanced magnetic resonance imaging (CE-MRI) of brain metastases in patients with known or suspected brain metastases from systemic malignancies. The study also compared the usefulness of gadobutrol in treatment planning for stereotactic radiosurgery (SRS).

MATERIALS AND METHODS

This was a Phase II/III, multicenter, single-blind, randomized, controlled, crossover, intraindividual comparison study. Each patient underwent one MRI study examination with gadobutrol and the other with gadoteridol, each at a dose of 0.1 mmol/kg BW, administered twice, for a total dose of 0.2 mmol/kg BW. Image acquisition was carried out after the first and second doses of gadobutrol, but only after the second dose of gadoteridol. Contrast agents were assigned in a randomized order and their administration separated by an interval of 1 to 14 days. Images were evaluated through blinded readings by 3 independent experienced radiologists. Treatment planning for SRS was assessed in a blinded manner, as a consensus between a diagnostic neuroradiologist and a radiation oncologist, in addition to the clinical investigator's assessment. The safety and tolerability of gadobutrol and gadoteridol were evaluated in all patients who received the study drugs. The primary efficacy variable was the number of lesions detected in CE-MRI images; the secondary efficacy variables were the degree of contrast enhancement and border delineation of lesions, and experts' confidence in treatment planning for SRS.

RESULTS

A total of 175 patients were enrolled and randomized, with 164 (93.7%) included in the safety analysis set, and 151 (86.2%) evaluable in the efficacy analysis. The mean number of detected lesions per patient using the average of the 3 blinded readers was 6.28, 6.92, and 6.87 for gadobutrol 0.1 and 0.2 mmol/kg BW, and gadoteridol 0.2 mmol/kg BW, respectively. Noninferiority of gadobutrol (both doses) to gadoteridol 0.2 mmol/kg BW was demonstrated. The degree of contrast enhancement and the border delineation of each lesion were categorized as "good" or "excellent" for most lesions for both agents. Almost all enhanced images were rated as "confident" in treatment planning for SRS. Sixty-five (43%) and 62 (41%) patients in the gadobutrol 0.1 and 0.2 mmol/kg BW groups, respectively, were selected as eligible for SRS treatment. The percentage of images assessed as "gadobutrol was better than gadoteridol" was higher than that assessed as "gadoteridol was better than gadobutrol" for both doses of gadobutrol. Eight adverse events were reported as being related to the study drug in 7 patients (4.3%) in each group.

CONCLUSION

In this study, a single dose of gadobutrol was shown to be noninferior to a double dose of gadoteridol at detecting brain metastases, and could be effectively used for treatment planning in patients eligible for SRS. A dose of gadobutrol 0.1 mmol/kg BW is recommended as the clinical dose for the detection of brain metastases.

Preoperative quantification of aortic valve stenosis: comparison of 64-slice computed tomography with transesophageal and transthoracic echocardiography and size of implanted prosthesis

Precise measurements of aortic complex diameters are essential for preoperative examinations of patients with aortic stenosis (AS) scheduled for aortic valve (AV) replacement. We aimed to prospectively compare the accuracy of transthoracic echocardiography (TTE), transoesophageal echocardiography (TEE) and multi-slice computed tomography (MSCT) measurements of the AV complex and to analyze the role of the multi-modality aortic annulus diameter (AAd) assessment in the selection of the optimal prosthesis to be implanted in patients surgically treated for degenerative AS. 20 patients (F/M: 3/17; age: 69 ± 6.5 years) with severe degenerative AS were enrolled into the study. TTE, TEE and MSCT including AV calcium score (AVCS) assessment were performed in all patients. The values of AAd obtained in the long AV complex axis (TTE, TEE, MSCT) and in multiplanar perpendicular imaging (MSCT) were compared to the size of implanted prosthesis. The mean AAd was 24 ± 3.6 mm using TTE, 26 ± 4.2 mm using TEE, and 26.9 ± 3.2 in MSCT (P = 0.04 vs. TTE). The mean diameter of the left ventricle out-flow tract in TTE (19.9 ± 2.7 mm) and TEE (19.5 ± 2.7 mm) were smaller than in MSCT (24.9 ± 3.3 mm, P < 0.001 for both). The mean size of implanted prosthesis (22.2 ± 2.3 mm) was significantly smaller than the mean AAd measured by TTE (P = 0.0039), TEE (P = 0.0004), and MSCT (P < 0.0001). The implanted prosthesis size correlated significantly to the AAd: r = 0.603, P = 0.005 for TTE, r = 0.592, P = 0.006 for TEE, and r = 0.791, P < 0.001 for MSCT. Obesity and extensive valve calcification (AV calcium score ≥ 3177Ag.U.) were identified as potent factors that caused a deterioration of both TTE and MSCT performance. The accuracy of AAd measurements in TEE was only limited by AV calcification. In multivariate regression analysis the mean value of the minimum and maximum AAd obtained in MSCT-multiplanar perpendicular imaging was an independent factor (r = 0.802, P < 0.0001) predicting the size of implanted prosthesis. In patients with AS echocardiography remains the main diagnostics tool in clinical practice. MSCT as a 3-dimentional modality allows for accurate measurement of entire AV complex and facilitates optimal matching of prosthesis size.

Computed tomography of the coronary arteries in diagnosis

IMPORTANCE OF THE FIELD

Cardiac computed tomography (CT) has recently emerged as a non-invasive alternative to catheter angiography for the assessment of coronary artery disease. Rapid technological advances have rendered coronary CT angiography to a robust, accurate and fast imaging modality to assess coronary artery disease in selected patients. The list of further indications in which cardiac CT is an appropriate test remains a topic of discussion.

AREAS COVERED IN THIS REVIEW

This review discusses the main literature available on the use of cardiac CT in the indications considered appropriate in the 2006 Appropriateness Criteria by the American College of Radiology with special emphasis on the temporal trends in the utilization of cardiac CT in clinical practice and in the opinion of the experts, and provides an outlook on how cardiac CT might evolve in the future.

WHAT THE READER WILL GAIN

The reader will gain insight into the strengths and shortcomings of CT of the coronary arteries in coronary artery diagnosis and will learn why cardiac CT is appropriate in some indications but not in others.

TAKE HOME MESSAGE

Recent research in cardiac CT has substantially improved the evaluation of the coronary arteries with CT, and the list of indications cardiac CT is appropriate for might expand further in the coming years.

Comparison of dual-source computed tomography for the quantification of the aortic valve area in patients with aortic stenosis versus transthoracic echocardiography and invasive hemodynamic assessment

We compared the measurements of the aortic valve area (AVA) using dual-source computed tomography (DSCT) in patients with mid to severe aortic stenosis to measurements using transthoracic echocardiography (TTE) and invasive hemodynamic assessment. A total of 50 patients (mean age 73 +/- 10 years) with suspected aortic stenosis were included. The computed tomographic data were acquired using DSCT with standardized scan parameters (2 x 64 x 0.6 mm collimation, 330-ms rotation, 120-kV tube voltage, 560 mA/rot tube current). After injection of 35 ml contrast agent (flow rate 5 ml/s), a targeted volume data set, ranging from the top of the leaflets to the infundibulum, was acquired. Ten cross-sectional data sets (slice thickness 1 mm, no overlap, increment 0.6 mm) were reconstructed during systole in 5% increments of the R-R interval. The AVA determined in systole by planimetry was compared to the calculated AVA values using the continuity equation on TTE and the Gorlin formula on catheterization. DSCT allowed the planimetry of the AVA in all patients. The mean AVA using DSCT was 1.16 +/- 0.47 cm(2) compared to a mean AVA of 1.04 +/- 0.45 cm(2) using TTE and 1.06 +/- 0.45 cm(2) using catheterization, with a significant correlation between DSCT/TTE (r = 0.93, p <0.001) and DSCT/cardiac catheterization (r = 0.97, p <0.001). However, DSCT demonstrated a slight, but significant, overestimation of the AVA compared to TTE (+0.12 +/- 0.17 cm) and catheterization (+0.10 +/- 0.12 cm(2)). In conclusion, DSCT permits one to assess the AVA with a high-image quality and diagnostic accuracy compared to TTE and invasive determination.

Comparison of cardiac computed tomographic angiography to transesophageal echocardiography for evaluation of patients with native valvular heart disease

Retrospectively gated helical cardiac computed tomographic angiography (CCTA) has been reported accurate in the evaluation of isolated valvular abnormalities, but its ability to provide comprehensive assessment of common valvular lesions is not established. We evaluated 56 consecutive patients undergoing 64-detector retrospective electrocardiogram-gated CCTA and transesophageal echocardiography for the presence of aortic and mitral stenoses, aortic and mitral regurgitations, mitral valve prolapse, and tricuspid regurgitation. Two cardiac computed tomographic angiographic readers measured maximum aortic and mitral valve opening areas, assessed for aortic or mitral valve regurgitant area, and evaluated for mitral valve prolapse. Tricuspid regurgitation was assessed by the contrast ratio of the inferior vena cava to the right heart. After excluding nondiagnostic valves on CCTA (mitral valve n = 4, aortic valve n = 2), the sensitivity, specificity, positive predictive values, and negative predictive values of CCTA compared to transesophageal echocardiography were 100%, 96%, 50%, and 100% for aortic stenosis, 44%, 96%, 67%, and 90% for aortic regurgitation, 100% each for mitral stenosis, 13%, 95%, 80%, and 45% for mitral regurgitation, and 50%, 98%, 80%, and 91% for mitral valve prolapse. There was no relation between tricuspid regurgitation grade and contrast ratio (p = 0.53). There was excellent interobserver agreement for aortic and mitral stenoses (kappa = 1.0 for each), and good agreement for aortic regurgitation, mitral regurgitation, and mitral valve prolapse (kappa = 0.81, 0.78, and 0.88, respectively). In conclusion, CCTA exhibited high diagnostic performance for detection of aortic and mitral stenoses and limited diagnostic performance for aortic regurgitation, mitral regurgitation, and mitral valve prolapse; tricuspid regurgitation could not be evaluated. The ability of CCTA to provide comprehensive assessment of valvular function is variable.

Planimetry of the aortic valve orifice area: comparison of multislice spiral computed tomography and magnetic resonance imaging

OBJECTIVE

We sought to determine the comparability of multislice computed tomography (MSCT) and magnetic resonance imaging (MRI) for measuring the aortic valve orifice area (AVA) and grading aortic valve stenosis.

MATERIALS AND METHODS

Twenty-seven individuals, among them 18 patients with valvular stenosis, underwent AVA planimetry by both MSCT and MRI. In the subset of patients with valvular stenosis, AVA was also calculated from transthoracic Doppler echocardiography (TTE) using the continuity equation.

RESULTS

There was excellent correlation between MSCT and MRI (r = 0.99) and limits of agreement were in an acceptable range (± 0.42 cm(2)) although MSCT yielded a slightly smaller mean AVA than MRI (1.57 ± 0.83 cm(2) vs. 1.67 ± 0.98 cm(2), p < 0.05). However, in the subset of patients with valvular stenosis, the mean AVA was not different between MSCT and MRI (1.05 ± 0.30 cm(2) vs. 1.04 ± 0.39 cm(2); p > 0.05). The mean AVAs on both MSCT and MRI were systematically larger than on TTE (0.88 ± 0.28 cm(2), p < 0.001 each). Using an AVA of 1.0 cm(2) on TTE as reference, the best threshold for detecting severe-to-critical stenosis on MSCT and MRI was an AVA of 1.25 cm(2) and 1.30 cm(2), respectively, resulting in an accuracy of 96% each.

CONCLUSION

Our study specifies recent reports on the suitability of MSCT for quantifying AVA. The data presented here suggest that certain methodical discrepancies of AVA measurements exist between MSCT, MRI and TTE. However, MSCT and MRI have shown excellent correlation in AVA planimetry and similar accuracy in grading aortic valve stenosis.

Mitral annular shape, size, and motion in normals and in patients with cardiomyopathy: evaluation with computed tomography

OBJECTIVE

To assess prospectively, in healthy subjects and in patients with dilated cardiomyopathy (DCM) and hypertrophic obstructive cardiomyopathy (HOCM), the 3-dimensional (3D) shape, size, and motion of the mitral annulus (MA) using computed tomography (CT).

MATERIALS AND METHODS

Twenty patients with no cardiac abnormalities (referred to as normals), 15 with DCM, and 15 with HOCM as determined by echocardiography underwent contrast-enhanced, retrospectively electrocardiography (ECG)-gated 64-slice CT of the heart. The MA was manually segmented in 10% steps of the RR interval with dedicated 3D software employing the point-wrap algorithm. The MA shape, area size, change of the MA area, and apicobasal MA motion throughout the cardiac cycle was determined and compared between the groups. Intercommissural distances were measured with CT and compared with findings during surgery in 9 patients undergoing ring annuloplasty.

RESULTS

The MA was nonplanar in all phases and subjects, being largest in diastole and smallest in systole. The MA area was significantly (P < 0.001) larger in patients with DCM (11.5 +/- 4.1 cm/m) as compared with normals (5.5 +/- 0.9 cm/m) and HOCM (4.7 +/- 0.9 cm/m). The change of MA area throughout the cardiac cycle was significantly (P < 0.017) smaller in patients with DCM (12.2 +/- 3.3%/m) as compared with normals (20.0 +/- 7.9%/m) and HOCM (20.5 +/- 7.7%/m). The mean apicobasal motion was significantly (P < 0.017) smaller in patients with DCM (2.2 +/- 1.0 mm/m) as compared with normals (3.6 +/- 0.8 mm/m) and HOCM (2.7 +/- 0.7 mm/m). Intercommissural distances as determined by CT showed a good correlation (r = 0.68, P < 0.05) with intraoperative measurements (mean difference, 0.44 mm; limits of agreement, -2.73-3.62 mm).

CONCLUSION

Our study provides in vivo human data on the 3D shape, size, and motion of the MA in healthy subjects. Significant changes in size and motion of the MA were noted in patients with HOCM.