Higher dose dobutamine stress MR imaging in repaired Tetralogy of Fallot: observer variance of volumetric assessment compared with normal volunteers.

PURPOSE: To investigate changes in image quality and observer variance between rest and higher-dose dobutamine stress MR imaging (DS-MR) in tetralogy of Fallot (TOF) patients and in a group of normal healthy volunteers using both axial and short axis orientation for cardiac volumetric assessment. MATERIALS AND METHODS: Eighteen adult patients (age 34 ± 13) with TOF and severe pulmonary regurgitation and 10 healthy volunteers underwent ventricular MR volumetry at baseline and during dobutamine infusion of 10 µg/kg/min and 20 µg/kg/min. Inter-observer and intra-observer agreement was calculated by coefficient of variance (COV). RESULTS: Inter-observer comparison showed good agreement for left ventricle (LV) and right ventricle (RV) end-diastolic volumes at rest and both stress levels in TOF patients (axial geometry) and in normal volunteers (short axis). During dobutamine stress, the COV in TOF patients increased for LV end-systolic volume (LV-ESV) with each level, suggesting less agreement between observers. In contrast, RV-ESV was much more comparable with a COV < 10 at each condition. All volumetric measurements in normal volunteers showed good inter-observer agreement. Excellent intra-observer agreement could be seen for all volumetric parameters with COV levels below 7. CONCLUSION: Volumetric assessment during DS-MR shows excellent inter-observer agreement, except for LV-ESV in the TOF patients at higher doses of dobutamine. The axial geometry appears to be reproducible for assessment of RV parameters, and could be considered superior to short axis imaging in patients with repaired TOF.

Single breath-hold assessment of cardiac function using an accelerated 3D single breath-hold acquisition technique--comparison of an intravascular and extravascular contrast agent.

BACKGROUND: Cardiovascular magnetic resonance (CMR) is the current gold standard for the assessment of left ventricular (LV) function. Repeated breath-holds are needed for standard multi-slice 2D cine steady-state free precession sequences (M2D-SSFP). Accelerated single breath-hold techniques suffer from low contrast between blood pool and myocardium. In this study an intravascular contrast agent was prospectively compared to an extravascular contrast agent for the assessment of LV function using a single-breath-hold 3D-whole-heart cine SSFP sequence (3D-SSFP). METHODS: LV function was assessed in fourteen patients on a 1.5 T MR-scanner (Philips Healthcare) using 32-channel coil technology. Patients were investigated twice using a 3D-SSFP sequence (acquisition time 18-25 s) after Gadopentetate dimeglumine (GdD, day 1) and Gadofosveset trisodium (GdT, day 2) administration. Image acquisition was accelerated using sensitivity encoding in both phase encoding directions (4xSENSE). CNR and BMC were both measured between blood and myocardium. The CNR incorporated noise measurements, while the BMC represented the coeffiancy between the signal from blood and myocardium [1]. Contrast to noise ratio (CNR), blood to myocardium contrast (BMC), image quality, LV functional parameters and intra-/interobserver variability were compared. A M2D-SSFP sequence was used as a reference standard on both days. RESULTS: All 3D-SSFP sequences were successfully acquired within one breath-hold after GdD and GdT administration. CNR and BMC were significantly (p < 0.05) higher using GdT compared to GdD, resulting in an improved endocardial definition. Using 3D-SSFP with GdT, Bland-Altman plots showed a smaller bias (95% confidence interval LVEF: 9.0 vs. 23.7) and regression analysis showed a stronger correlation to the reference standard (R2 = 0.92 vs. R2 = 0.71), compared to 3D-SSFP with GdD. CONCLUSIONS: A single-breath-hold 3D-whole-heart cine SSFP sequence in combination with 32-channel technology and an intravascular contrast agent allows for the accurate and fast assessment of LV function.

Assessment of left ventricular volumes and mass with fast 3D cine steady-state free precession k-t space broad-use linear acquisition speed-up technique (k-t BLAST).

PURPOSE: To compare left ventricular (LV) volume and mass assessment using two-dimensional (2D) cine steady-state free precession (SSFP) and k-t space broad-use linear acquisition speed-up technique (k-t BLAST) accelerated 3D magnetic resonance imaging (MRI). MATERIALS AND METHODS: On a commercially available 1.5T MR scanner, 2D cine SSFP, six- and eight-fold accelerated 3D k-t BLAST were performed to evaluate LV volumes and mass in 17 volunteers. After semiautomatic segmentation of the different MR data sets, the resulting volumes and mass were compared according to the mean difference, 95% confidence interval, standard deviation (SD), Pearson's correlation coefficient, Bland-Altman analysis, and the Pitman-Morgan test. RESULTS: Data acquisition was successful in all subjects. The number of required breathholds was reduced from a maximal of five for the 2D cine SSFP sequence to two for 3D k-t BLAST sequences. Comparing LV volumes, there was excellent agreement between 2D and 3D cine 8x k-t BLAST SSFP volumes (mean difference +/- 2SD end-diastolic volume [EDV] = 5 +/- 8 mL, end-systolic volume [ESV] = 1 +/-12 mL, and stroke volume [SV] = 3 +/- 8 mL), and mass (-1.8 +/- 9 g). CONCLUSION: k-t BLAST-accelerated 3D sequences allow accurate assessment of LV volumes and mass compared to 2D cine SSFP. This method may reduce costs and increase patient comfort due to shortened data acquisition time and reduced number of breathholds.

Quantitative assessment of ventricular function using three-dimensional SSFP magnetic resonance angiography.

PURPOSE: To evaluate three-dimensional (3D), free-breathing, steady-state free precession (SSFP) magnetic resonance angiography (MRA) for volumetric assessment of ventricular function. MATERIALS AND METHODS: In 18 subjects (mean age = 21.5 years) 3D datasets of the heart and great vessels were acquired using an ECG-triggered, free-breathing SSFP technique with a T2-preparation prepulse. Data were acquired during end-systole (ES) and end-diastole (ED) for assessment of stroke volumes (SVs). Through-plane flow measurements of the great arteries were performed as well as 2D-cine SSFP imaging for comparison. For image analysis of the 3D SSFP datasets a simplex mesh model was used. Papillary muscles were excluded from ventricular volumes using thresholds. Intra- and interobserver variability (Bland-Altman analysis) and correlations (Pearson's coefficient) between volumetric and flow measurements were assessed. RESULTS: ES and ED datasets were acquired successfully in all subjects. The best correlation was observed between flow vs. 3D SSFP SV for the LV (r = 0.85, mean difference = -1.0 mL) and the RV (r = 0.89, mean difference = -2.2 mL) with high intra- (LV: r = 0.93; RV: r = 0.94) and interobserver (LV: r = 0.91; RV: r = 0.93) reproducibility. CONCLUSION: 3D SSFP datasets combined with semiautomatic segmentation algorithms allow highly accurate and reproducible assessment of left (LV) and right ventricular (RV) SVs in free-breathing subjects.