Saturation recovery single-shot acquisition (SASHA) for myocardial T(1) mapping.

Purpose: To validate a new saturation recovery single-shot acquisition (SASHA) pulse sequence for T1 mapping and to compare SASHA T1 values in heart failure patients and healthy controls.

Theory: The SASHA sequence consists of 10 electrocardiogram-triggered single-shot balanced steady-state free precession images in a breath-hold. The first image is acquired without magnetization preparation and the remaining nine images follow saturation pulses with variable saturation recovery times.

Detection and quantification of myocardial reperfusion hemorrhage using T2*-weighted CMR.

Objectives: The purpose of this study was to validate T2*-weighted cardiac magnetic resonance (T2*-CMR) for the detection and quantification of reperfusion hemorrhage in vivo against an ex vivo gold standard, and to investigate the relationship of hemorrhage to microvascular obstruction, infarct size, and left ventricular (LV) functional parameters.

Background: Hemorrhage can contribute to reperfusion injury in myocardial infarction and may have significant implications for patient management. There is currently no validated imaging method to assess reperfusion hemorrhage in vivo.

Cerebral and myocardial blood flow responses to hypercapnia and hypoxia in humans.

In humans, cerebrovascular responses to alterations in arterial Pco(2) and Po(2) are well documented. However, few studies have investigated human coronary vascular responses to alterations in blood gases. This study investigated the extent to which the cerebral and coronary vasculatures differ in their responses to euoxic hypercapnia and isocapnic hypoxia in healthy volunteers.

Oxygenation-sensitive CMR for assessing vasodilator-induced changes of myocardial oxygenation.

Background: As myocardial oxygenation may serve as a marker for ischemia and microvascular dysfunction, it could be clinically useful to have a non-invasive measure of changes in myocardial oxygenation. However, the impact of induced blood flow changes on oxygenation is not well understood. We used oxygenation-sensitive CMR to assess the relations between myocardial oxygenation and coronary sinus blood oxygen saturation (SvO2) and coronary blood flow in a dog model in which hyperemia was induced by intracoronary administration of vasodilators.

Single-shot steady-state free precession can detect myocardial edema in patients: a feasibility study.

Purpose: To demonstrate the ability of single-shot, T(2)/T(1) weighted steady-state free precession (SSFP) to detect myocardial edema in patients with an acute myocardial infarction.

Materials And Methods: This study was performed in a series of patients (n = 10) referred for the assessment of acute myocardial infarcts (AMI). Localizers were used to obtain true short axis views of the left ventricle (LV).

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.

MR imaging- versus conventional X-ray fluoroscopy-guided renal angioplasty in swine: prospective randomized comparison.

Purpose: To test the hypothesis that the technical success rates, complication rates, and procedural times for magnetic resonance (MR) imaging-guided percutaneous transluminal angioplasty (PTA) and conventional (x-ray) fluoroscopy-guided PTA for treatment of renal artery stenosis are similar.

Materials And Methods: The study was animal care and use committee approved. After surgically inducing bilateral renal artery stenosis in 11 swine, the authors performed baseline digital subtraction angiography.

Comparison of X-ray fluoroscopy and interventional magnetic resonance imaging for the assessment of coronary artery stenoses in swine.

The accuracy of a two-step interventional MRI protocol to quantify coronary artery disease was compared to the clinical gold standard, X-ray angiography. Studies were conducted in nine swine with a surgically induced stenosis in the proximal left circumflex coronary artery. The two-step protocol consisted of catheter-directed magnetic resonance angiography (MRA), which was first used to localize the stenosis, followed by MRI cross-sectional images to quantify the degree of stenosis without the use of contrast agent.

Three-dimensional contrast-enhanced steady-state free precession for improved catheter-directed coronary magnetic resonance angiography.

Purpose: To demonstrate the feasibility of three-dimensional thick-partition, contrast-enhanced, catheter-directed coronary artery magnetic resonance angiography (MRA) and test the hypothesis that three-dimensional imaging improves coronary artery background contrast-to-noise ratio (CNR) compared to two-dimensional imaging.

Materials And Methods: Catheters were advanced into the coronary arteries of swine (N = 6) under MR guidance. Three-dimensional coronary MRA was performed after intracoronary injection of a small dose of contrast media using magnetization-prepared steady-state free precession (SSFP) with two thick partitions.

Determination of optimal gadolinium concentration using SSFP for catheter-directed contrast-enhanced coronary MR angiography.

Rationale And Objectives: To determine the optimal gadolinium concentration for catheter-directed coronary magnetic resonance angiography (MRA) using magnetization-prepared steady-state free-precession (SSFP) in swine.

Materials And Methods: In six pigs, we performed real-time MR imaging-guided coronary artery catheterization using a 1.5 T MR scanner.

Catheter-directed MR angiography and cross-sectional imaging for the assessment of renal artery stenosis.

Purpose: Catheter-directed intraarterial (IA) gadolinium (Gd)-enhanced gradient-echo (GRE) imaging has been used in the setting of magnetic resonance (MR) imaging-guided endovascular procedures for two-dimensional (2D) or three-dimensional (3D) depiction of blood vessels. In a swine model, the hypothesis was tested that the combination of 2D IA GRE and 2D cross-sectional steady-state free precession (SSFP) imaging improves assessment of renal artery stenosis (RAS) compared with 3D IA GRE imaging alone.

Materials And Methods: Bilateral RAS was surgically induced in seven pigs.

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.

Catheter-directed contrast-enhanced coronary MR angiography in swine using magnetization-prepared True-FISP.

Contrast-enhanced (CE) coronary magnetic resonance angiography (MRA) following intraarterial (IA) injection of contrast agent was compared using two sequences in swine: magnetization-prepared fast imaging with steady-state precession (True-FISP), and magnetization-prepared fast low-angle shot (FLASH). Thick-slice projection images were acquired with submillimeter in-plane spatial resolution (0.9 x 0.

Real-time magnetic resonance imaging-guided coronary catheterization in swine.

Background: We tested the hypothesis that real-time magnetic resonance imaging (MRI) can guide coronary artery catheterization in swine via a percutaneous femoral artery approach.

Methods And Results: In 12 pigs, we accessed femoral arteries percutaneously. We used 6- or 7-French coronary Judkins catheters filled with dilute 4% gadolinium (Gd) contrast agent and coaxially inserted 0.

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.

Use of internal coils for independent and direct MR imaging-guided endovascular device tracking.

Purpose: To test the hypotheses that a single internal guide wire coil (i) permits independent and direct depiction of guide wires and catheters and (ii) improves catheter-tracking accuracy and depiction compared to external receiver coils.

Materials And Methods: Standard 5-6-F angiographic catheters were filled with dilute 4% gadolinium chelate. A single 0.

Two- and three-dimensional MR coronary angiography with intraarterial injections of contrast agent in dogs: a feasibility study.

Magnetic resonance (MR) images of coronary arteries were acquired with an inversion recovery-prepared technique after intraarterial injection of contrast material in five dogs. Real-time two-dimensional projection images were obtained with a temporal resolution of 3 frames per second. Three-dimensional electrocardiographically triggered high-spatial-resolution images were obtained with a fraction of the contrast agent required for intravenous injections.

Passive catheter tracking using MRI: comparison of conventional and magnetization-prepared FLASH.

Purpose: To compare a magnetization-prepared gradient-echo (GRE) sequence with a conventional GRE sequence for visualizing contrast agent-filled catheters.

Materials And Methods: Passive visualization of endovascular catheters using MRI was compared between two imaging sequences: 1) inversion recovery (IR)-fast low angle shot (FLASH), and 2) conventional FLASH. Two-dimensional projection images of the catheters filled with 4% diluted contrast agent in a phantom and the aorta of swine were obtained with each sequence with a temporal resolution of two frames per second.

Minimizing contrast agent dose during intraarterial gadolinium-enhanced MR angiography: in vitro assessment.

Purpose: To minimize contrast agent dosage for intra-arterial (IA) contrast-enhanced magnetic resonance angiography (CE-MRA) by examining the effects of encoding order (elliptical vs. sequential) and injection duration (100% to 30% of the acquisition time).

Materials And Methods: Catheter-based IA gadolinium (Gd) injections were performed in an arterial flow phantom.