The optimum infusion timing and k-space ordering for obtaining gadolinium-enhanced three-dimensional MR angiograms was determined through computer modeling using temporal contrast characteristics obtained from patient gadolinium infusion data. The effects of bolus timing were evaluated by varying the relationship between peak intravascular gadolinium concentration and the time at which the center of k space was acquired (tck) for sequential and centric acquisition techniques. Flow phantom experiments were performed to validate the theoretical computations. Gadolinium concentration at the time of central k-space acquisition determines intravascular signal intensity. Artifacts, including vessel broadening and edge ringing, depend on the order in which k space is collected and on how rapidly the gadolinium concentration changes. Artifacts are greatest when the center of k space is acquired before the intravascular gadolinium peak. Application of the optimal infusion timing results in preferential arterial enhancement with a minimum of artifacts in patients undergoing MR angiography.

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Computed tomographic angiography and MRA are not reproducible or sensitive enough to rule out renal artery stenosis in hypertensive patients. Therefore, DSA remains the diagnostic method of choice. *For a list of the other investigators and research coordinators who participated in RADISH, see the Appendix.

T ransthoracic echocardiography (TTE) is the standard clinical tool for initial assessment and longitudinal evaluation of patients with valvular heart disease.1 Current clinical guidelines for the management of adults with chronic valve regurgitation include clear recommendations for measuring regurgitant severity.1,2 Quantification is recommended as a tool to identify patients at risk of adverse long-term physiological consequences, including irreversible left ventricular (LV) contractile dysfunction, and to prevent adverse clinical outcomes, including heart failure, sudden death, and cardiovascular mortality. Clinical Perspective on p 57TTE allows measurement of regurgitant volume (RVol), fraction, and orifice area and has been well validated in both experimental and clinical studies. 2 In addition, regurgitant orifice area (ROA) has been shown to be predictive of clinical outcome for both aortic regurgitation (AR) and mitral regurgitation (MR). 3 However, echocardiographic quantification of valve regurgitation can be challenging because of poor acoustic windows, dynamic or eccentric jets, and geometric assumptions. 2,4,5 Cardiovascular magnetic resonance (CMR) is an alternative modality for assessing patients with chronic valve regurgitation based on measurement of LV volumes and phase-contrast velocity mapping.6-8 CMR has several potential advantages compared with TTE, including improved endocardial definition, fewer geometric assumptions, and less angle dependence for flow measurements. However there are few data on direct systematic comparisons, including reproducibility, between TTE and CMR for quantitation of AR and MR. Thus, we hypothesized that CMR has less interobserver variability when quantifying chronic AR and MR and thus may be preferable for longitudinal follow-up in individual patients.Background-Both transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) imaging allow quantification of chronic aortic regurgitation (AR) and mitral regurgitation (MR). We hypothesized that CMR measurement of regurgitant volume (RVol) is more reproducible than TTE.Methods and Results-TTE and CMR performed on the same day in 57 prospectively enrolled adults (31 with AR, 26 with MR) were measured by 2 independent physicians. TTE RVol AR was calculated as Doppler left ventricular outflow minus inflow stroke volume. RVol MR was calculated by both the proximal isovelocity surface area method and Doppler volume flow at 2 sites. CMR RVol AR was calculated by phase-contrast velocity mapping at the aortic sinuses and RVol MR as total left ventricular minus forward stroke volume. Intraobserver and interobserver variabilities were similar. For AR, the Bland-Altman mean interobserver difference in RVol was −0.7 mL (95% confidence interval [CI], −5 to 4) for CMR and −9 mL (95% CI, −53 to −36) for TTE. The Pearson correlation was higher (P=0.001) between CMR (0.99) than TTE readers (0.89). For MR, the Bland-Altman mean difference in RVol between observers was −4 mL (95% CI, −21 to 13) for CMR compared with 0....