Three-dimensional breathhold magnetization-prepared TrueFISP: a pilot study for magnetic resonance imaging of the coronary artery disease.

PURPOSE: X-ray angiography is currently the standard test for the assessment of coronary artery disease. A substantial minority of patients referred for coronary angiography have no significant coronary artery disease. The purpose of this work was the evaluation of the accuracy of a three-dimensional (3D) breathhold coronary magnetic resonance angiography (MRA) technique in detecting hemodynamically significant coronary artery stenoses in a patient population with x-ray angiographic correlation. MATERIALS AND METHODS: Sequential subjects (n = 33, M/F = 22/11, average age = 57) who were referred for conventional coronary angiography were enrolled in the study. The study protocol was approved by our institutional review board. Each subject gave written informed consent. Volume-targeted 3D breathhold coronary artery scans with ECG-triggered, segmented True Fast Imaging with Steady-state Precession (TrueFISP) were acquired for the left main (LM), left anterior descending (LAD), and right coronary arteries (RCAs). Coronary MRA was evaluated with conventional angiography as the gold standard. RESULTS: The overall sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) for diagnosing any hemodynamically significant coronary artery disease (> or =50% diameter reduction) with coronary MRA was 87%, 57%, 72%, 68%, and 80%, respectively. The sensitivity of the technique in the LM, LAD, and RCA was 100%, 83%, and 100%, respectively. The NPV of the technique in the LM, LAD, and RCA was 100%, 82%, and 100%, respectively. CONCLUSIONS: Three-dimensional breathhold True Fast Imaging with Steady-state Precession is a promising technique for coronary artery imaging. It has a relatively high sensitivity and NPV. Results of this study warrant further technical improvements and clinical evaluation of the technique.

Accuracy of stepping-table lower extremity MR angiography with dual-level bolus timing and separate calf acquisition: hybrid peripheral MR angiography.

PURPOSE: To retrospectively evaluate the accuracy of hybrid peripheral magnetic resonance (MR) angiography by using conventional digital subtraction angiography (DSA) as the reference standard. MATERIALS AND METHODS: This retrospective study protocol received approval from the Office of Sponsored Research at Northwestern University, which included review by the Office for the Protection of Research Subjects. Informed consent was waived for this HIPAA-compliant study. One hundred twenty-one consecutive patients (67 men: mean age, 66 years +/- 12 [standard deviation]; 54 women: mean age, 69 years +/- 14), who were referred for evaluation of peripheral vascular disease, underwent peripheral contrast material-enhanced MR angiography. By using a hybrid technique, two independent timing measurements were performed in the pelvis and calves followed by MR angiography of the calves and, subsequently, a pelvis-thigh stepping-table acquisition. Images were evaluated for extent of disease, on the basis of degree of stenosis; for venous contamination, on the basis of venous signal intensity; and for diagnostic quality, on the basis of diagnostic confidence of the observer. DSA correlation of the extent of vascular disease was available in 45 of these patients, which was used to evaluate the diagnostic power of the hybrid technique. RESULTS: For detection of stenosis greater than 50%, the hybrid technique had 95% sensitivity (P < .05), 95% specificity (P < .05), and 95% accuracy (P < .05). There was no significant venous contamination in any of the examinations performed with this technique. CONCLUSION: The hybrid peripheral MR angiography technique provides diagnostic-quality examinations and virtually eliminates venous contamination.

Method for improving the accuracy of quantitative cerebral perfusion imaging.

PURPOSE: To improve the accuracy of dynamic susceptibility contrast (DSC) measurements of cerebral blood flow (CBF) and volume (CBV). MATERIALS AND METHODS: In eight volunteers, steady-state CBV (CBV(SS)) was measured using TrueFISP readout of inversion recovery (IR) before and after injection of a bolus of contrast. A standard DSC (STD) perfusion measurement was performed by echo-planar imaging (EPI) during passage of the bolus and subsequently used to calculate the CBF (CBF(DSC)) and CBV (CBV(DSC)). The ratio of CBV(SS) to CBV(DSC) was used to calibrate measurements of CBV and CBF on a subject-by-subject basis. RESULTS: Agreement of values of CBV (1.77 +/- 0.27 mL/100 g in white matter (WM), 3.65 +/- 1.04 mL/100 g in gray matter (GM)), and CBF (23.6 +/- 2.4 mL/(100 g min) in WM, 57.3 +/- 18.2 mL/(100 g min) in GM) with published gold-standard values shows improvement after calibration. An F-test comparison of the coefficients of variation of the CBV and CBF showed a significant reduction, with calibration, of the variability of CBV in WM (P < 0.001) and GM (P < 0.03), and of CBF in WM (P < 0.0001). CONCLUSION: The addition of a CBV(SS) measurement to an STD measurement of cerebral perfusion improves the accuracy of CBV and CBF measurements. The method may prove useful for assessing patients suffering from acute stroke.

Non-invasive cardiac evaluation in heart failure patients using magnetic resonance imaging: a feasibility study.

BACKGROUND: To assess the feasibility of a fast, flow-insensitive magnetic resonance imaging (MRI) protocol in heart failure patients for the evaluation of cardiac function, cardiovascular anatomy, and myocardial viability. METHODS AND RESULTS: Thirty-two consecutive patients with left ventricular (LV) systolic dysfunction and 13 control subjects were prospectively evaluated with MRI. The exam consisted of cine imaging with a steady-state free precession sequence, followed by time-resolved, three-dimensional angiography and delayed, contrast-enhanced imaging. Multiple LV parameters were evaluated, and the heart failure and control results were compared. In 12 patients, MRI-determined ejection fractions were compared to echocardiographic values. Additionally, a qualitative analysis of the cine images was performed. The cardiac MR evaluation yielded diagnostic-quality images in all subjects. Mean imaging time was 37 min. MRI demonstrated significant differences between the heart failure and control subjects in all parameters assessed (p < 0.05). MRI-determined ejection fractions correlated strongly with echocardiographic values (R = 0.75), although the limits of agreement were wide (-17.3%-18.3%). CONCLUSIONS: Using fast, flow-insensitive imaging techniques, MRI is feasible in heart failure for the derivation of more independent indices of cardiac status than any other non-invasive test. Although further investigation is warranted, MRI may prove uniquely helpful in heart failure diagnosis and management.

Breath-hold three-dimensional true-FISP imaging of coronary arteries using asymmetric sampling.

PURPOSE: To evaluate the feasibility of using asymmetric sampling in a three-dimensional, magnetization-prepared, segmented true-FISP (fast imaging with steady-state precession) sequence in order to reduce the sensitivity to resonance offsets, while simultaneously improving imaging speed. MATERIALS AND METHODS: Asymmetric sampling reduces the repetition time, leading to reduced resonance offset effects and improved resolution in a fixed imaging time. However, it introduces additional phase terms due to blood flow, which can cause image artifacts. Computer simulations were performed to study the off-resonance and flow effects of asymmetric sampling in true-FISP. Coronary artery imaging was performed in healthy volunteers. RESULTS: Simulations and volunteer studies show that image artifacts due to flow-induced phase variations may be acceptable at low velocities. Volunteer studies demonstrate that relatively high-resolution coronary artery images can then be acquired within a single breath-hold with segmented three-dimensional true-FISP imaging using data asymmetry in the readout direction. CONCLUSION: Asymmetric sampling is a useful modification to true-FISP for reducing the off-resonance artifacts and improving imaging speed when the flow velocities are small.

Projection imaging of the right coronary artery with an intravenous injection of contrast agent.

Contrast-enhanced (CE) MR angiography of the right coronary artery (RCA) was performed using 2D thick-slice projection imaging with a small (8 mL) intravenous injection of contrast agent in six volunteers. With a tight contrast bolus injection, the RCA was enhanced for a few seconds after the contrast bolus was washed out of the right ventricle. This allowed data to be acquired when only the RCA was enhanced. Using 2D thick-slice magnetization prepared steady-state free precession (SSFP) imaging, background signal was suppressed and a complete data set was acquired in three heartbeats. A mean vessel length of 7.1 +/- 0.9 cm was depicted with a signal-to-noise ratio of 11.8 +/- 0.7 and contrast-to-noise ratio of 6.1 +/- 0.6. Thick-slice 2D projection CE SSFP is a promising method to depict the RCA.

Thoracic aortic dissection and aneurysm: evaluation with nonenhanced true FISP MR angiography in less than 4 minutes.

Comprehensive aortic magnetic resonance (MR) examinations currently include multiple nonenhanced and contrast material-enhanced sequences. The authors hypothesized that the nonenhanced true fast imaging with steady-state precession (FISP) portion alone of their comprehensive imaging protocol would be adequate to confidently confirm or exclude dissection or aneurysm of the aorta. In a retrospective review of 29 comprehensive thoracic aortic MR examinations, nonenhanced true FISP MR imaging alone was 100% accurate for determining the presence or absence of dissection or aneurysm.

Coronary artery imaging using three-dimensional breath-hold steady-state free precession with two-dimensional iterative partial fourier reconstruction.

PURPOSE: To assess the feasibility of using a two-dimensional partial Fourier (PF) reconstruction scheme to reduce the acquisition time of magnetic resonance imaging (MRI) of coronary arteries. MATERIALS AND METHODS: Symmetric k-space data sets of coronary arteries were collected in seven volunteers using a three-dimensional breath-hold steady-state free precession (SSFP) sequence. Partial, asymmetric k-space data sets were generated by removing 25% of the data in the readout direction and 25% of the data in the phase encoding direction. The missing data were then estimated using a two-dimensional projection-onto-convex-sets (POCS) algorithm or filled with zeroes. Images were reconstructed from the full data set, the PF data set, and the zero-filled (ZF) data set, respectively. Coronary artery sharpness was evaluated quantitatively and qualitatively. RESULTS: Coronary artery sharpness in PF images was comparable to that in full k-space images and significantly better than that in ZF images. CONCLUSION: Two-dimensional POCS PF reconstruction is a potentially useful technique for reducing acquisition time or improving spatial resolution for breath-hold coronary MR angiography.

Thorax: low-dose contrast-enhanced three-dimensional MR angiography with subsecond temporal resolution--initial results.

The purpose of the study was to implement a three-dimensional (3D) magnetic resonance (MR) angiographic technique with acquisition times on the order of 800 msec with use of a spoiled gradient-echo pulse sequence (repetition time, 1.60 msec; echo time, 0.65 msec) and bolus intravenous injection of contrast material doses as small as 6 mL. High-spatial-resolution conventional MR angiography performed with 30 mL of gadopentetate dimeglumine was the reference standard. As implemented, subsecond 3D MR angiography allowed temporal sampling that was rapid enough to depict short-lived processes, as illustrated in patients with shunts and dissections. With small contrast material doses and subsecond frame rates, it is also possible to measure pulmonary arteriovenous circulation times with this 3D MR angiographic technique.

Coronary MR angiography: true FISP imaging improved by prolonging breath holds with preoxygenation in healthy volunteers.

In 15 healthy volunteers undergoing coronary magnetic resonance (MR) angiography, the breath-hold duration with and without preoxygenation was measured. The effect of preoxygenation on coronary artery imaging was also evaluated. A three-dimensional magnetization-prepared true fast imaging with steady-state precession sequence was employed for coronary MR angiography. All subjects showed an increase in comfortable breath-hold duration with preoxygenation. This extra imaging time allowed coronary artery imaging with increased spatial resolution.