Single-source dual energy CT to assess myocardial extracellular volume fraction in aortic stenosis before transcatheter aortic valve implantation (TAVI).

PURPOSE: To assess myocardial extracellular volume fraction (ECV) measurement provided by a single-source dual-energy computed tomography (SSDE-CT) acquisition added at the end of a routine CT examination before transcatether aortic valve implantation (TAVI) compared to cardiac magnetic resonance imaging (MRI). MATERIALS AND METHODS: Twenty-one patients (10 men, 11 women; mean age, 86±4.9 years [SD]; age range: 71-92 years) with severe aortic stenosis underwent standard pre-TAVI CT with additional cardiac SSDE-CT acquisition 7minutes after intravenous administration of iodinated contrast material and myocardial MRI including pre- and post-contrast T1-maps. Myocardial ECV and standard deviation (σECV) were calculated in the 16-segments model. ECV provided by SSDE-CT was compared to ECV provided by MRI, which served as the reference. Analyses were performed on a per-segment basis and on a per-patient involving the mean value of the 16-segments. RESULTS: ECV was slightly overestimated by SSDE-CT (29.9±4.6 [SD] %; range: 20.9%-48.3%) compared to MRI (29.1±3.9 [SD] %; range: 22.0%-50.7%) (P<0.0001) with a bias and limits of agreement of +2.3% (95%CI: -16.1%-+20.6%) and +2.5% (95%CI: -2.1%-+7.1%) for per-segment and per-patient-analyses, respectively. Good (r=0.81 for per-segment-analysis) to excellent (r=0.97 for per-patient-analysis) linear relationships (both P<0.0001) were obtained. The σECV was significantly higher at SSDE-CT (P<0.0001). Additional radiation dose from CT was 1.89±0.38 (SD) mSv (range: 1.48-2.47 mSv). CONCLUSION: A single additional SSDE-CT acquisition added at the end of a standard pre-TAVI CT protocol can provide ECV measurement with good to excellent linear relationship with MRI.

Head-to-head comparison of the diagnostic performance of coronary computed tomography angiography and dobutamine-stress echocardiography in the evaluation of acute chest pain with normal ECG findings and negative troponin tests: A prospective multicenter study.

OBJECTIVE: To perform a head-to-head comparison of coronary CT angiography (CCTA) and dobutamine-stress echocardiography (DSE) in patients presenting recent chest pain when troponin and ECG are negative. METHODS: Two hundred seventeen patients with recent chest pain, normal ECG findings, and negative troponin were prospectively included in this multicenter study and were scheduled for CCTA and DSE. Invasive coronary angiography (ICA), was performed in patients when either DSE or CCTA was considered positive or when both were non-contributive or in case of recurrent chest pain during 6month follow-up. The presence of coronary artery stenosis was defined as a luminal obstruction >50% diameter in any coronary segment at ICA. RESULTS: ICA was performed in 75 (34.6%) patients. Coronary artery stenosis was identified in 37 (17%) patients. For CCTA, the sensitivity was 96.9% (95% CI 83.4-99.9), specificity 48.3% (29.4-67.5), positive likelihood ratio 2.06 (95% CI 1.36-3.11), and negative likelihood ratio 0.07 (95% CI 0.01-0.52). The sensitivity of DSE was 51.6% (95% CI 33.1-69.9), specificity 46.7% (28.3-65.7), positive likelihood ratio 1.03 (95% CI 0.62-1.72), and negative likelihood ratio 1.10 (95% CI 0.63-1.93). The CCTA: DSE ratio of true-positive and false-positive rates was 1.70 (95% CI 1.65-1.75) and 1.00 (95% CI 0.91-1.09), respectively, when non-contributive CCTA and DSE were both considered positive. Only one missed acute coronary syndrome was observed at six months. CONCLUSIONS: CCTA has higher diagnostic performance than DSE in the evaluation of patients with recent chest pain, normal ECG findings, and negative troponine to exclude coronary artery disease.

Comparative assessment of image quality for coronary CT angiography with iobitridol and two contrast agents with higher iodine concentrations: iopromide and iomeprol. A multicentre randomized double-blind trial.

OBJECTIVES: To demonstrate non-inferiority of iobitridol 350 for coronary CT angiography (CTA) compared to higher iodine content contrast media regarding rate of patients evaluable for the presence of coronary artery stenoses. METHODS: In this multicentre trial, 452 patients were randomized to receive iobitridol 350, iopromide 370 or iomeprol 400 and underwent coronary CTA using CT systems with 64-detector rows or more. Two core lab readers assessed 18 coronary segments per patient regarding image quality (score 0 = non diagnostic to 4 = excellent quality), vascular attenuation, signal and contrast to noise ratio (SNR, CNR). Patients were considered evaluable if no segment had a score of 0. RESULTS: Per-patient, the rate of fully evaluable CT scans was 92.1, 95.4 and 94.6 % for iobitridol, iopromide and iomeprol, respectively. Non-inferiority of iobitridol over the best comparator was demonstrated with a 95 % CI of the difference of [-8.8 to 2.1], with a pre-specified non-inferiority margin of -10 %. Although average attenuation increased with higher iodine concentrations, average SNR and CNR did not differ between groups. CONCLUSIONS: With current CT technology, iobitridol 350 mg iodine/ml is not inferior to contrast media with higher iodine concentrations in terms of image quality for coronary stenosis assessment. KEY POINTS: • Iodine concentration is an important parameter for image quality in coronary CTA. • Contrast enhancement must be balanced against the amount of iodine injected. • Iobitridol 350 is non-inferior compared to CM with higher iodine concentrations. • Higher attenuation with higher iodine concentrations, but no SNR or CNR differences.

Right ventricle segmentation from cardiac MRI: a collation study.

Magnetic Resonance Imaging (MRI), a reference examination for cardiac morphology and function in humans, allows to image the cardiac right ventricle (RV) with high spatial resolution. The segmentation of the RV is a difficult task due to the variable shape of the RV and its ill-defined borders in these images. The aim of this paper is to evaluate several RV segmentation algorithms on common data. More precisely, we report here the results of the Right Ventricle Segmentation Challenge (RVSC), concretized during the MICCAI'12 Conference with an on-site competition. Seven automated and semi-automated methods have been considered, along them three atlas-based methods, two prior based methods, and two prior-free, image-driven methods that make use of cardiac motion. The obtained contours were compared against a manual tracing by an expert cardiac radiologist, taken as a reference, using Dice metric and Hausdorff distance. We herein describe the cardiac data composed of 48 patients, the evaluation protocol and the results. Best results show that an average 80% Dice accuracy and a 1cm Hausdorff distance can be expected from semi-automated algorithms for this challenging task on the datasets, and that an automated algorithm can reach similar performance, at the expense of a high computational burden. Data are now publicly available and the website remains open for new submissions (http://www.litislab.eu/rvsc/).

Single-source dual-energy CT angiography with reduced iodine load in patients referred for aortoiliofemoral evaluation before transcatheter aortic valve implantation: impact on image quality and radiation dose.

OBJECTIVES: To compare image quality and radiation dose of pre-transcatheter aortic valve implantation (TAVI) aortoiliofemoral CT angiography (AICTA) provided by standard vs. dual-energy mode with reduced iodine load protocols. METHODS: One hundred and sixty-one patients underwent a two-step CTA protocol before TAVI including cardiac CTA with injection of 65 mL of iodinated contrast agent (ICA), immediately followed by AICTA. From this second acquisition, the following three different patient groups were identified: Group 1: 52 patients with standard AICTA (60 mL ICA, 100 kVp, mA automodulation); Group 2: 48 patients with dual-energy AICTA with 50 % iodine load reduction (30 mL ICA, fast kVp switching, 600 mA); Group 3: 61 patients with an identical protocol to Group 2, but exposed to 375 mA. The qualitative/subjective image quality (13-point score) and quantitative/objective image quality (contrast attenuation and image noise) were evaluated. The radiation dose was recorded. RESULTS: There was no significant difference in non-diagnostic images between the three protocols. Contrast attenuation, signal-to-noise ratio and contrast-to-noise ratio were significantly higher, whereas noise was significantly lower in the standard protocol (all P < 0.05). The radiation dose was lower in the dual-energy protocol at 375 mA (P < 0.05). CONCLUSIONS: Dual-energy AICTA before TAVI results in a reduction of iodine load while maintaining sufficient diagnostic information despite increased noise. KEY POINTS: • Dual-energy AICTA before TAVI results in a 50 % reduction of iodine load. •The reduction of iodine load maintains sufficient image quality despite increased noise. • Using 375 mA in dual-energy mode results in a reduction of radiation dose. • A high tube current setting (600 mA) should be used in overweight patients.

Supranormal differential renal function in unilateral hydronephrotic kidney: insights from functional MR urography.

PURPOSE: To retrospectively assess supranormal differential renal function (DRF) in unilateral hydronephrotic kidney by functional MR urography (fMRU). MATERIALS AND METHODS: The ethics committees granted exempt status for this study and also waived the need for informed consent. A retrospective analysis was performed of all patients undergoing fMRU from January 2008 to November 2011. DRF was measured by both the area under the curve method and Rutland-Patlak plot. Glomerular DRF per unit of volume and kidney volumes were analyzed. Kidney volumes were compared with nomograms. RESULTS: Of 170 children, 3 patients (2, 12, and 14 years) with a left ureteropelvic junction obstruction were included. Glomerular DRF per unit of volume was slightly higher on the dilated side but remained within normal range (<55%). Dilated kidney volumes were higher on the dilated side (≥55%). The volumes of nondilated kidneys were within normal range. CONCLUSION: The data support the fact that the dilated kidney was not hyperfunctioning and that the nondilated kidney was not hypofunctioning. Based on these three patients, it could be assumed that supranormal DRF on the dilated side might be explained by a slight kidney volume asymmetry, in association with higher DRF per unit of volume, remaining within normal physiological range. J. Magn. Reson. Imaging 2014;40:577-582. © 2013 Wiley Periodicals, Inc.

Effect of the ellipsoid shape of the left ventricular outflow tract on the echocardiographic assessment of aortic valve area in aortic stenosis.

BACKGROUND: Previous studies showed discrepancies between echocardiographic and multidector row CT (MDCT) measurements of aortic valve area (AVA). OBJECTIVE: Our aim was to evaluate the effect of the ellipsoid shape of the left ventricular outflow tract (LVOT), as shown and measured by MDCT, on the assessment of AVA by transthoracic echocardiography (TTE) in patients with severe aortic stenosis. METHODS: This retrospective single-center study involved 49 patients with severe aortic stenosis referred before transcatheter aortic valve implantation. The AVA was deduced from the continuity equation on TTE and from planimetry on cardiac MDCT. Area of the LVOT was calculated as follows: on TTE, from the measurement of LVOT diameter on parasternal long-axis view; on MDCT, from manual planimetry by using multiplanar reconstruction perpendicular to LVOT. RESULTS: At baseline, correlation of TTE vs MDCT AVA measurements was moderate (R = 0.622; P < .001). TTE underestimated AVA compared with MDCT (0.66 ± 0.15 cm2 vs. 0.87 ± 0.15 cm2; P < .001). After correcting the continuity equation with the LVOT area as measured by MDCT, mean AVA drawn from TTE did not differ from MDCT (0.86 ± 0.2 cm2) and correlation between TTE and MDCT measurements increased (R = 0.704; P < .001). CONCLUSION: Assuming that LVOT area is circular with TTE results in constant underestimation of the AVA with the continuity equation compared with MDCT planimetry. The elliptical not circular shape of LVOT largely explains these discrepancies.

MRI and suspected acute pyelonephritis in children: comparison of diffusion-weighted imaging with gadolinium-enhanced T1-weighted imaging.

OBJECTIVES: To evaluate the performance of diffusion-weighted imaging (DWI) against the reference standard of gadolinium-enhanced T1-weighted imaging (Gd-T1-WI) in children. METHODS: Thirty-nine consecutive patients (mean age 5.7 years) with suspected acute pyelonephritis underwent magnetic resonance imaging (MRI) including DWI and (the reference standard) Gd-T1-WI. Each study was read in double-blinded fashion by two radiologists. Each kidney was graded as normal or abnormal. Sensitivity and specificity of DWI were computed. Agreement between sequences and interobserver reproducibility were calculated (Cohen κ statistic and the McNemar tests). RESULTS: Thirty-two kidneys (41 %) had hypo-enhancing areas on Gd-T1-W images. The sensitivity and specificity of DWI were 100 % (32/32) and 93.5 % (43/46). DWI demonstrated excellent agreement (κ = 0.92,) with Gd-T1-W, with no significant difference (P = 0.25) in detection of abnormal lesions. Interobserver reproducibility was excellent with DWI (κ = 0.79). CONCLUSION: DWI enabled similar detection of abnormal areas to Gd-T1-WI and may provide an injection-free means of evaluation of acute pyelonephritis. KEY POINTS: • Diffusion weighted magnetic resonance imaging (DWI) can confirm acute pyelonepritis. • DWI provided comparable results to gadolinium enhanced T1-W MRI in acute pyelonepritis. • Contrast medium injection could be avoided for diagnosing acute pyelonephritis by MRI. • MRI with T2-WI and DWI provide a fast and comprehensive diagnostic tool.

MR relaxometry and perfusion of the myocardium in spontaneously hypertensive rat: correlation with histopathology and effect of anti-hypertensive therapy.

OBJECTIVES: To investigate myocardial relaxation times and perfusion values in spontaneously hypertensive rats (SHRs) at various stages of the disease, with or without anti-fibrotic therapy, and to correlate magnetic resonance imaging (MRI) findings with histopathological myocardial fibrosis and capillary density. METHODS: Five groups of rats underwent MRI at 4.7 T. They were either untreated or treated with an aldosterone-synthase inhibitor. T1, T2 and T2 relaxation times were determined and myocardial perfusion was quantified from an arterial spin labelling sequence. MR relaxation times and perfusion values were compared with the fibrotic content and capillary density of the myocardium obtained at histology after euthanasia. RESULTS: T1 values significantly increased during the course of hypertensive disease, and correlated with myocardial fibrosis (R = 0.71, P < 0.001); T2 values also increased but were weakly correlated with myocardial fibrosis (R = 0.27,P = 0.047). Myocardial perfusion and capillary density significantly decreased with hypertensive disease but they did not correlate. Following prolonged treatment, we observed a trend associating T1 decrease and improved perfusion compared with untreated SHRs. CONCLUSIONS: Myocardial T1 and T2 values increase with hypertensive disease, whereas myocardial perfusion decreases. The correlation between T1 values and collagen density suggests that the former could be considered as a non-invasive marker of myocardial fibrosis. KEY POINTS: • MR is increasingly used to assess alteration in myocardial tissue content. • MR relaxometry and perfusion can be assessed in rats without exogenous contrast agents. • Myocardial T1 and T2 values significantly increase during the course of hypertensive heart disease. • T1 values correlate significantly with myocardial collagen content. • Myocardial perfusion values decrease with hypertensive disease.

Cardiac MRI assessment of right ventricular function in acquired heart disease: factors of variability.

RATIONALE AND OBJECTIVES: To evaluate intra- and inter-observer variability of right ventricular (RV) functional parameters as evaluated by cardiac magnetic resonance imaging (MRI) in patients with acquired heart disease (AHD), and to identify factors associated with an increased variability. MATERIALS AND METHODS: Sixty consecutive patients were enrolled. Right and left ventricular (LV) volumes, ejection fraction, and mass were determined from short-axis cine sequences. All analyzes were performed twice by three observers with various training-degree in cardiac MRI. Intra- and inter-observer variability was evaluated. The impact on variability of each of the following parameters was assessed: observer's experience, basal and apical slices selection, end-systolic phase selection, and delineation. RESULTS: Mean segmentation time ranged 9.8-19.0 minutes for RV and 6.4-9.2 minutes for LV. Variability of RV functional parameters measurement was strongly influenced by previous observer's experience: it was two to three times superior to that of LV, even for the most experienced observer. High variability in the measurement of RV mass was observed. For both ventricles, selection of the basal slice and delineation were major determinants of variability. CONCLUSION: As compared to LV, RV function assessment with cardiac MRI in AHD patients is much more variable and time-consuming. Observer's experience, selection of basal slice, and delineation are determinant.

Transapical aortic valve implantation in Rouen: four years' experience with the Edwards transcatheter prosthesis.

BACKGROUND: The first French transapical transcatheter aortic valve implantation (TAVI) was performed in July 2007 in our department. AIMS: To report 4-year outcomes of transapical implantation with the Edwards transcatheter bioprosthesis. METHODS: We prospectively evaluated consecutive patients who underwent transapical implantation with an Edwards transcatheter bioprosthesis between July 2007 and October 2011. Patients were not suitable for conventional surgery (due to severe comorbidities) or transfemoral implantation (due to poor femoral access). RESULTS: Among 61 patients (59.0% men), mean logistic EuroSCORE was 27.5 ± 14.9% and mean age was 81.0 ± 6.8 years. Successful valve implantation was achieved in 59/61 patients (96.7%) of patients. The other two patients required conversion to conventional surgery due to prosthesis embolization and died. Six additional patients died in the postoperative period. Causes of perioperative death were two septic shocks (one of peritonitis), two multi-organ failure, one ventricular fibrillation and one respiratory insufficiency. Intraprocedural stroke was not observed in any patient. The actuarial survival rates at 1, 2 and 4 years were 73.8%, 67.2% and 41.0%. During this 4-year period, four patients died of cardiovascular events, but no impairment of transprosthesis gradient was observed. CONCLUSION: Our series of 61 patients who underwent transapical implantation of the Edwards transcatheter bioprosthesis shows satisfactory results, similar to other reports, considering the high level of severity of patients referred for this method. Transapical access is a reliable alternative method for patients that cannot benefit from a transfemoral approach.

[Selection of patients for transcatheter aortic valve implantation]. / Implantation de valve aortique percutanée : sélection des patients.

A good selection of patients is a crucial step before transcatheter aortic valve implantation (TAVI) in order to select the good indications and choose the access route. TAVI should be considered only in patients with symptomatic severe aortic stenosis and either contraindication or high surgical risk. Indication for TAVI should be discussed in a multidisciplinary team meeting. Echocardiography and/or CT scan are mandatory to evaluate the aortic annulus size and select the good prosthesis size. The possibility of transfemoral implantation is evaluated by angiography and CT scan, and based on the arterial diameters, but also on the presence of tortuosities and arterial calcifications.

Evaluation of multislice computed tomography early after transcatheter aortic valve implantation with the Edwards SAPIEN bioprosthesis.

Currently, imaging assessment of patients who undergo transcatheter aortic valve implantation is based mainly on echocardiography and angiography, both limited to provide a 3-dimensional evaluation of the prosthesis within the native valve. This study involved 34 patients who underwent multislice computed tomography (MSCT) after transcatheter aortic valve implantation. Prosthesis expansion and circularity, depth of implantation, apposition degree at the ventriculoaortic junction, and positioning in relation to coronary artery ostia were evaluated. Early clinical events such as aortic regurgitation and periprocedural conduction abnormalities were recorded and correlated with multislice computed tomographic findings. MSCT provided comprehensive 3-dimensional assessments of the prostheses in 31 of 34 of patients (91%). Expansion was excellent (mean expansion ratio 100.0 ± 10.4%) and increased significantly from the ventricular side to the aortic side of the prosthesis. Circular deployment was achieved in most patients and increased from the ventricular to the aortic side. Mean implantation depth was -2.4 ± 2.5 mm, associated with a low rate (12%) of permanent pacemaker implantation. Patients with a new conduction abnormalities had the deepest prosthesis implantation, associated with lesser expansion and circularity. Perfect apposition on MSCT was associated with a low rate of significant aortic regurgitation. In conclusion, MSCT is able to provide an accurate 3-dimensional evaluation of prosthesis deployment and positioning after transcatheter aortic valve implantation. Moreover, these anatomic findings correlate with the most frequent early complications (i.e., the occurrence of aortic regurgitation and conduction abnormalities).

Diagnostic accuracy and variability of three semi-quantitative methods for assessing right ventricular systolic function from cardiac MRI in patients with acquired heart disease.

OBJECTIVES: To evaluate the diagnostic accuracy and variability of 3 semi-quantitative (SQt) methods for assessing right ventricular (RV) systolic function from cardiac MRI in patients with acquired heart disease: tricuspid annular plane systolic excursion (TAPSE), RV fractional-shortening (RVFS) and RV fractional area change (RVFAC). METHODS: Sixty consecutive patients were enrolled. Reference RV ejection fraction (RVEF) was determined from short axis cine sequences. TAPSE, RVFS and RVFAC were measured on a 4-chamber cine sequence. All SQt analyses were performed twice by 3 observers with various degrees of training in cardiac MRI. Correlation with RVEF, intra- and inter-observer variability, and receiver operating characteristic (ROC) curve analysis were performed for each SQt method. RESULTS: Correlation between RVFAC and RVEF was good for all observers and did not depend on previous cardiac MRI experience (R range = 0.716-0.741). Conversely, RVFS (R range = 0.534-0.720) and TAPSE (R range = 0.482-0.646) correlated less with RVEF and depended on previous experience. Intra- and inter-observer variability was much lower for RVFAC than for RVFS and TAPSE. ROC analysis demonstrated that RVFAC <41% could predict a RVEF <45% with 90% sensitivity and 94% specificity. CONCLUSIONS: RVFAC appears to be more accurate and reproducible than RVFS and TAPSE for SQt assessment of RV function by cardiac MRI.