Quantitative assessment of right ventricular function and pulmonary regurgitation in surgically repaired tetralogy of Fallot using 256-slice CT: comparison with 3-Tesla MRI.

OBJECTIVES: To compare 256-slice cardiac computed tomography (CCT) with cardiac magnetic resonance (CMR) imaging to assess right ventricular (RV) function and pulmonary regurgitant fraction (PRF) in patients with repaired tetralogy of Fallot (TOF). METHODS: Thirty-three consecutive patients with repaired TOF underwent retrospective ECG-gated CCT and 3-Tesla CMR. RV and left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF) were measured using CCT and CMR. PRF-CCT (%) was defined as (RVSV - LVSV)/RVSV. PRF-CMR (%) was measured by the phase-contrast method. Repeated measurements were performed to determine intra- and interobserver variability. RESULTS: CCT measurements, including PRF, correlated highly with the CMR reference (r = 0.71-0.96). CCT overestimated RVEDV (mean difference, 17.1 ± 2.9 ml), RVESV (12.9 ± 2.1 ml) and RVSV (4.2 ± 2.0 ml), and underestimated RVEF (-2.6 ± 1.0%) and PRF (-9.1 ± 2.0%) compared with CMR. The limits of agreement between CCT and CMR were in a good range for all measurements. The variability in CCT measurements was lower than those in CMR. The estimated effective radiation dose was 7.6 ± 2.6 mSv. CONCLUSIONS: 256-slice CCT can assess RV function and PRF with relatively low dose radiation exposure in patients with repaired TOF, but overestimates RV volume and underestimates PRF. KEY POINTS: 256-slice CT assessment of RV function is highly reproducible in repaired TOF. Pulmonary regurgitation can be evaluated by biventricular systolic volume difference. CT overestimates RV volume and underestimates pulmonary regurgitation, compared with MRI.

Subendocardial contractile impairment in chronic ischemic myocardium: assessment by strain analysis of 3T tagged CMR.

BACKGROUND: The purpose of this study was to quantify myocardial strain on the subendocardial and epicardial layers of the left ventricle (LV) using tagged cardiovascular magnetic resonance (CMR) and to investigate the transmural degree of contractile impairment in the chronic ischemic myocardium. METHODS: 3T tagged CMR was performed at rest in 12 patients with severe coronary artery disease who had been scheduled for coronary artery bypass grafting. Circumferential strain (C-strain) at end-systole on subendocardial and epicardial layers was measured using the short-axis tagged images of the LV and available software (Intag; Osirix). The myocardial segment was divided into stenotic and non-stenotic segments by invasive coronary angiography, and ischemic and non-ischemic segments by stress myocardial perfusion scintigraphy. The difference in C-strain between the two groups was analyzed using the Mann-Whitney U-test. The diagnostic capability of C-strain was analyzed using receiver operating characteristics analysis. RESULTS: The absolute subendocardial C-strain was significantly lower for stenotic (-7.5 ± 12.6%) than non-stenotic segment (-18.8 ± 10.2%, p < 0.0001). There was no difference in epicardial C-strain between the two groups. Use of cutoff thresholds for subendocardial C-strain differentiated stenotic segments from non-stenotic segments with a sensitivity of 77%, a specificity of 70%, and areas under the curve (AUC) of 0.76. The absolute subendocardial C-strain was significantly lower for ischemic (-6.7 ± 13.1%) than non-ischemic segments (-21.6 ± 7.0%, p < 0.0001). The absolute epicardial C-strain was also significantly lower for ischemic (-5.1 ± 7.8%) than non-ischemic segments (-9.6 ± 9.1%, p < 0.05). Use of cutoff thresholds for subendocardial C-strain differentiated ischemic segments from non-ischemic segments with sensitivities of 86%, specificities of 84%, and AUC of 0.86. CONCLUSIONS: Analysis of tagged CMR can non-invasively demonstrate predominant impairment of subendocardial strain in the chronic ischemic myocardium at rest.

[Image quality assessment of Step&Shoot overlap reconstruction (SSOR) for cardiac computed tomography (CT)].

BACKGROUND: Step&Shoot cardiac computed tomography (CT) provides the benefit of significant reduction in radiation dose compared to helical cardiac CT acquisitions. We think that a difference occurs in image quality by presence of overlap reconstruction (fractionated sentence, attempted to clarify). PURPOSE: We studied the utility of Step&Shoot overlap reconstruction (SSOR). METHODS: We evaluated image quality of SSOR by comparing z-axis spatial resolution on various s in scanners that SSOR is possible and for those that are impossible. RESULTS: SSOR indicated better z-axis spatial resolution and less variation over the field of view (FOV) (in z & x-y directions) as compared with Step&Shoot without overlap reconstruction (SS). In addition, SS showed inadequate image reproducibility due to aliasing error in z-direction (lack of sampling interval). CONCLUSIONS: SSOR would contribute to improvement of the image quality of Step&Shoot cardiac CT.