Richard M. McCarthy

Method for Improving the Accuracy of Quantitative Cerebral Perfusion Imaging

To improve the accuracy of dynamic susceptibility contrast (DSC) measurements of cerebral blood flow (CBF) and volume (CBV).

Preoperative evaluation of the entire hepatic vasculature in living liver donors with use of contrast-enhanced MR angiography and true fast imaging with steady-state precession.

PURPOSE To preoperatively assess the entire hepatic vasculature in living related liver donors with use of a combination of contrast material-enhanced magnetic resonance (MR) angiography and true fast imaging with steady-state precession (FISP). MATERIALS AND METHODS Twenty-five living potential liver donors were examined preoperatively on a 1.5T Siemens Sonata system. Twenty-four underwent surgery and two had catheter angiography performed to delineate complex anatomy. Contiguous 5-mm-thick, sub-second true FISP images of the liver were initially obtained during breath-holding in axial and coronal planes (repetition time [TR]/echo time [TE], 3.2/1.6; flip angle, 70 degrees ). MR angiography was performed with use of a three-dimensional (3D) gradient-echo fast low-angle shot (FLASH) pulse sequence (TR/TE, 3.0/1.2; flip angle, 25 degrees ), with 40 mL of Gadolinium DTPA injected at a rate of 2 mL/sec. One precontrast and two postcontrast coronal 3D volumes were acquired, each in a 20-second breath-hold, and two subtracted 3D sets were calculated. Arterial anatomy was assessed with use of maximum-intensity projection, volume rendering, and multiplanar reformatting algorithms. Hepatic and portal venous anatomy was evaluated with use of the true FISP images and the venous phase of the MR angiogram. Visualization of hepatic arterial branches was noted. Visualization of portal vein branches was scored on a scale of 0-5. The presence of anatomic variants was noted. Vascular anatomy was confirmed at the time of surgery and at catheter angiography. RESULTS Segmental branch vessels were visualized on MR angiography in the majority of cases. The segment four branch was identified in 96% patients. Variant arterial anatomy was seen in 50% of patients. MR angiography detected 10 of 11 arterial variants found at surgery and angiography. Visualization of portal vein branches was generally higher with true FISP compared to MR angiography. Twenty-four percent of patients had variant portal venous anatomy. Caudal hepatic veins were identified in 60% of patients, of which eight were significant (>5 mm). Hepatic and portal venous anatomy was accurately predicted by true FISP and MR angiography in all patients who went on to undergo surgery. CONCLUSION Preoperative imaging with use of a combination of contrast-enhanced MR angiography and true FISP provides a comprehensive assessment of the entire hepatic vasculature in living liver donors.

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

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.

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 (≥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.

Feasibility and Performance of Breath-Hold 3D TRUE-FISP Coronary MRA Using Self-Calibrating Parallel Acquisition

Spatial resolution in 3D breath‐hold coronary MR angiography (MRA) is limited by imaging time. The purpose of this work was to investigate the feasibility of improving the spatial resolution of coronary MRA using generalized autocalibrating partially parallel acquisition (GRAPPA) and fast imaging with steady state precession (True‐FISP) data acquisition. Coronary data were acquired in 10 healthy volunteers. In five volunteers, the data were fully acquired in k‐space and decimated for GRAPPA with an outer reduction factor (ORF) of 2. The coil calibration in GRAPPA was improved by segmented least‐squares fitting along the frequency‐encoding direction. More than 5% of the total k‐space lines were required for the calibration to achieve acceptable artifact suppression despite slightly lower signal‐to‐noise ratio (SNR). In another five volunteers, coronary data were obtained with both conventional and accelerated data acquisitions in the same imaging time. GRAPPA allowed a submillimeter in‐plane resolution, and improved coronary artery definition with an acceptable loss of SNR. In conclusion, 3D breath‐hold coronary MRA by GRAPPA and True‐FISP is highly feasible. Magn Reson Med 52:7–13, 2004.

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. Magn Reson Med 52:699–703, 2004.

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.

Coronary Artery Imaging Using Three-Dimensional Breath-Hold Steady-State Free Precession With Two-Dimensional Iterative Partial Fourier Reconstruction

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.