Contrast-enhanced Inversion Recovery Research Articles

Improved inversion time (TI) scout sequence for late gadolinium enhancement MRI of patients with implantable cardiac devices

Background Late gadolinium enhancement (LGE) cardiac MRI is the clinical gold standard for non-invasive characterization of myocardial scar [1]. The LGE technique is a contrast enhanced inversion recovery (IR) FLASH sequence, and requires a priori knowledge of the initial inversion time (TI) to produce optimal contrast between healthy myocardium and scar substrate. The TI is typically assessed using a Look-Locker based TI scout sequence. Recent advances [2,3] have enabled successful application of LGE MRI to patients with cardiac implantable devices at our institution. Presence of cardiac devices, such as implantable cardioverter defibrillators (ICD), gives rise to severe offresonance in the myocardium. This produces banding artifacts in standard TI scout images which cannot be used to estimate the initial TI for LGE imaging. This can result in LGE images with poor contrast and delays in patient scanning. In this abstract, we present a modification to the standard TI scout sequence that prominently reduces artifacts in TI scout images. Methods The TI scout sequence is an inversion prepared cine sequence with TrueFISP readout. Severe off-resonance from an ICD produces severe banding artifacts in TrueFISP images. In addition, in IR sequences, severe off-resonance can prevent inversion of spins in the myocardium, giving rise to hyper-intensity artifacts [2,3]. Recently, we demonstrated that a wideband (3.8 kHz) inversion pulse can overcome this off-resonance effect and invert off-resonant spins sufficiently, thereby eliminating hyper-intensity artifacts [2,3]. We modified the TI scout sequence by replacing the conventional inversion pulse (bandwidth: 1.1 kHz) with a wideband inversion pulse (spectral bandwidth: 3.8 kHz). We also replaced the TrueFISP readout with a FLASH readout. The modified sequence was tested on a group of T1 phantoms and one ICD patient. Results Figure 1 shows phantom images of the modified TI scout sequence. The phantom results show that when a flip angle of 5° is used, the modified TI scout sequence can be used to determine the optimal TI quite accurately. At higher flip angles, larger TIs may be underestimated due to signal burn-off. Figure 2 demonstrates the banding artifacts produced when the standard TI scout sequence is used in an ICD patient. The modified TI scout sequence is able to remove these artifacts completely and allow effective determination of the optimal TI. Conclusions We have modified the TI scout sequence by implementing a wideband inversion pulse and FLASH readout. Phantom results and patient studies demonstrate that the modified sequence has none of the image artifacts that occur with the standard sequence, and produces a reliable estimation of inversion time. We expect that the new TI scout sequence will lead to improved application of LGE MRI in patients with implantable cardiac devices. Funding

3.0-T whole-heart coronary magnetic resonance angiography: comparison of gadobenate dimeglumine and gadofosveset trisodium

Gadolinium enhanced coronary magnetic resonance angiography (MRA) at 3 T appears to be superior to non-contrast methods. Gadofosveset is an intravascular contrast agent that may be well suited to this application. The purpose of this study was to perform an intra-individual comparison of gadofosveset and gadobenate for coronary MRA at 3 T. In this prospective randomized study, 22 study subjects [8 (36%) male; 27.9 ± 6 years; BMI = 22.8 ± 2 kg/m(2)] underwent two studies using a contrast-enhanced inversion recovery three-dimensional fast low angle shot MRA at 3 T. The order of contrast agent administration was varied randomly, separated by an average of 30 ± 5 days, using either gadobenate dimeglumine (Gd-BOPTA; Bracco, 0.1 mmol/Kg) or gadofosveset trisodium (MS-325; Lantheus Med, 0.03 mmol/Kg). Acquisition time, signal-to-noise ratio (SNR) of coronary vessels and contrast-to-noise ratio (CNR) were evaluated. Of 308 coronary arteries and veins segment analyzed, overall SNR of coronary arteries and veins segments were not different for the two contrast agents (132 ± 79 for gadofosveset vs. 135 ± 78 for gadobenate, p = 0.69). Coronary artery CNR was greater for gadofosveset in comparison to gadobenate (73.5 ± 46.9 vs. 59.3 ± 75.7 respectively, p = 0.03). Gadofosveset-enhanced MRA images displayed better image quality than gadobenate-enhanced MRA images (2.77 ± 0.61 for gadofosveset vs. 2.11 ± 0.51, p < .001). Inter- and intra-reader variability was excellent (ICC > 0.90) for both contrast agents. Gadofosveset trisodium appears to show slightly better performance for coronary MRA at 3 T compared to gadobenate.

The Assessment of Area at Risk and Myocardial Salvage After Coronary Revascularization in Acute Myocardial Infarction: Comparison Between CMR and SPECT

This study sought to compare cardiac magnetic resonance (CMR) and single-photon emission computed tomography (SPECT) for assessment of area at risk, scar size, and salvage area after coronary reperfusion in acute myocardial infarction. Myocardial salvage is an important surrogate endpoint assessing the success of coronary reperfusion in acute myocardial infarction. SPECT, the established modality for assessment of myocardial salvage, requires radiopharmaceutical injection before revascularization and 2 examinations. The combination of T2 and late enhancement imaging in CMR can assess myocardial salvage in 1 examination, but up to now, data comparing both modalities are very limited. We analyzed 207 patients who were treated by primary revascularization in acute myocardial infarction and who underwent both SPECT and CMR for assessment of myocardial salvage. In CMR, T2-weighted turbo spin echo sequences for area at risk and contrast-enhanced inversion recovery gradient echo sequences were performed. Image quality was insufficient in 27 patients (13%). In the remaining 180 patients, mean area at risk was 29.4 ± 18.7% of the left ventricle (LV), and infarct size was 14.7 ± 16.9% LV, resulting in a mean salvage area of 14.9 ± 15.1% LV in SPECT, whereas in CMR, mean area at risk was 28.0 ± 14.5% LV, and infarct size was 16.0 ± 13.5% LV, resulting in a mean salvage area of 11.9 ± 12.3%. Results of both modalities correlated well for area at risk (r = 0.80), scar size (r = 0.87), and salvage area (r = 0.66, all p < 0.0001). Assessment of the salvage area by CMR using T2 and late enhancement imaging correlates well with the established modality of SPECT. CMR therefore may be an alternative to paired SPECT imaging for myocardial salvage assessment, but the contraindications of the modality and limitations in the established T2 imaging sequences currently cause a considerable rate of data loss.

Contrast enhancement imaging in coronary arteries in patients with systemic lupus erythematosus

Summary Patients with SLE suffer from accelerated atherosclerosis due to systemic inflammation. We examined subclinical coronary artery involvement in patients with systemic lupus erythematous (SLE) by contrast enhanced inversion recovery (CE-IR) coronary magnetic resonance imaging. Background Vessel wall inflammation plays a key role in the initiation and progression of atherosclerosis, from endothelial injury to remodeling and plaque formation. Cardiovascular (CV) magnetic resonance (CMR) provides noninvasive visualization and characterization of arterial remodeling both in the great vessels, and also the coronary arteries. Contrast-enhanced inversion-recovery (CEIR) prepared coronary imaging allows detection of vessel wall enhancement by visualization of contrast agent uptake. We examined subclinical coronary artery involvement in patients with systemic lupus erythematous (SLE) by contrast enhanced inversion recovery (CE-IR) coronary magnetic resonance imaging. Methods

Paradoxical embolism in a patient with a large tricuspid myxoma and patent foramen ovale

A 61-year-old man with an uneventful medical history presented with two transient ischaemic attacks (TIA) with bulbar and peripheral deficit. Transthoracal and transoesophageal echocardiography revealed a patent foramen ovale (PFO) and a large, lobulated, pedunculated, non-calcified, and heterogenic mass attached to the septal tricuspid leaflet ( Panels 1–3 ) with important mobility. MRI suggested a myxoma, being isointense on T1-weighted turbo spin echo (TSE), iso-hyperintense on T2-weighted TSE, and hypointense on spoiled gradient echo. First-pass perfusion showed a heterogeneous and hypoperfused enhancement pattern, while contrast-enhanced inversion recovery images showed diffuse hyperenhancement ( Panels 4 and 5 ). Carotid echo-Doppler, Holter monitoring, and a …

Contrast-Enhanced Whole-Heart Coronary MRA using Gadofosveset: 3.0 T versus 1.5 T

To compare contrast-enhanced coronary magnetic resonance angiography (MRA) at 3.0 T with the same technique performed at 1.5 T using the contrast agent gadofosveset. In this prospective randomized study, 19 healthy male volunteers (mean age 28 years, mean weight 79.8 kg), after signing informed consents, underwent contrast-enhanced inversion recovery three-dimensional fast low angle shot (FLASH) MRA at 1.5 and at 3.0 T. Prospective electrocardiogram-triggering was combined with adaptive respiratory gating. For contrast-enhanced images, the intravascular contrast agent gadofosveset was used. Acquisition time, signal-to-noise ratio (SNR) of coronary blood, contrast-to-noise ratio (CNR) between coronaries and adjacent myocardium or epicardial fat and image quality were analyzed for statistical differences by using a two-tailed paired-sample t-test. The ratio calculations were based on measurements performed on the raw data and the image quality was blinded and independently evaluated by two experienced radiologists using a five-point scale. The mean values for the acquisition time were 14.58 +/- 0.1 minutes at 1.5 T and 16.40 +/- 0.2 minutes at 3.0 T. Overall SNR of all evaluated coronary segments proved higher at 3.0 T compared to 1.5 T (74.0 +/- 42.1 at 3.0 T vs. 50.2 +/- 20.2 at 1.5 T, P = .04). Overall CNR between coronaries and myocardium was significantly increased at 3.0 T in comparison to 1.5 T (40.1 +/- 21.9 at 3.0 T vs. 24.4 +/- 17.2 at 1.5 T, P = .01). Between the two methods, no significant difference in overall CNR between coronaries and epicardial fat was observed (P = .08, NS). The 3.0 T MRA demonstrated superior overall image quality with respect to 1.5 T (2.28 +/- 0.71 at 3.0 T vs. 1.92 +/- 0.38 at 1.5T, P = .004). The use of higher field strength, 3.0 T instead of 1.5 T, resulted in similar CNR between coronaries and epicardial fat, higher SNR values and CNR between blood and myocardium, as well as an improved overall image quality, when gadofosveset in combination with electrocardiogram and respiratory triggering for coronary MRA was used.

Magnetic resonance coronary angiography: Comparison between a Gd-BOPTA- and a Gd-DTPA-enhanced spoiled gradient-echo sequence and a non-contrast-enhanced steady-state free-precession sequence

Several studies have demonstrated that the administration of contrast agents is advantageous in magnetic resonance coronary angiography (MRCA). To compare a non-contrast-enhanced steady-state free-precession (SSFP) with a contrast-enhanced inversion recovery spoiled gradient-echo (IR-GE) sequence using two different contrast agents for MRCA. Eight healthy volunteers were examined on a 1.5T MR scanner. For non-contrast-enhanced MRCA, a breath-hold three-dimensional (3D) SSFP sequence (repetition/echo time [TR/TE] 3.9/1.7 ms, flip angle [FA] 65 degrees) was used. Contrast-enhanced MRCA was performed repetitively in two imaging sessions over 30 min after injection of 0.2 mmol/kg body weight gadobenate dimeglumine (Gd-BOPTA) or gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) using a breath-hold 3D IR-GE sequence (TR/TE 4.1/1.7 ms, FA 15 degrees). The signal-to-noise ratios (SNR) of the coronary arteries, as well as the contrast-to-noise ratios (CNR) between coronary arteries and perivascular tissue, were calculated for all images. Blood T (1) values were repetitively estimated over 30 min using an SSFP sequence with incrementally increasing inversion times (TR/TE 2.4/1.0 ms, FA 50 degrees). Gd-BOPTA-enhanced images showed significantly (P<0.05) higher SNR and CNR compared to Gd-DTPA-enhanced images for all times after contrast injection (SNR: 1 min post injection [PI] 26.4+/-4.2 vs. 16.2+/-3.1; CNR: 1 min PI 21.4+/-3.7 vs. 13.2+/-2.6). Compared to the SSFP images, the Gd-BOPTA-enhanced images showed higher CNR values for all times after injection (1 min PI 21.4+/-3.7 vs. 13.8+/-5.5; P<0.05), whereas the Gd-DTPA-enhanced images did not (1 min PI 13.2+/-2.6 vs. 13.8+/-5.5; P>0.05). Blood T (1) estimates were not significantly different for either agent 1 min after administration (P>0.05), but they were significantly lower for Gd-BOPTA (P<0.05) from 7 to 25 min after injection. Compared to non-contrast-enhanced SSFP images, only Gd-BOPTA-enhanced images show a significantly improved contrast between the coronary arteries and the surrounding tissue.

Acute Pericarditis Assessed With Magnetic Resonance Imaging

A 19-year-old man with the diagnosis of acute pericarditis based on the classic clinical syndrome and an ECG (Figure 1A) was referred to our cardiac magnetic resonance (CMR) unit 1 month after his hospital admission because of suspected associated acute myocarditis. A follow-up ECG within the time frame of referral showed essentially significant regression of ST elevation (Figure 1B). An echocardiogram performed at the referring hospital on the same day (Figure 2A and 2B) was reported as showing mild concentric left ventricular (LV) hypertrophy with good LV systolic function (ejection fraction 75%). Figure 1. A, 12-Lead ECG showing sinus rhythm and widespread saddle-shaped ST elevation in the inferolateral leads. B, 12-Lead ECG showing sinus rhythm, PR-segment depression, and elevated ST-segment uptake in the inferior and septal leads. Figure 2. Transthoracic echocardiographic images during end diastole showing normal LV and right ventricular size and mild LV hypertrophy. Left parasternal short-axis view (A) and apical 4-chamber view (B) at the time of the initial MRI scan. …

Differences in null points between the left and right ventricles in contrast-enhanced inversion recovery MR imaging in patients with cardiac diseases

Delayed contrast-enhanced inversion recovery (IR) gradient-echo MR imaging has been applied to several cardiac diseases, including myocarditis, sarcoidosis, hypertrophic cardiomyopathy, and myocardial damages induced by medical procedures. Although a preliminary study has indicated the usefulness of this imaging for the detection of right ventricular (RV) myocardial damage associated with arrhythmogenic right ventricular cardiomyopathy, the null points of the RV myocardium have not been assessed on contrast-enhanced IR MR imaging. In this study, the null points of the RV and left ventricular (LV) myocardia were evaluated using an IR fast multi-shot echo-planar imaging (Look–Locker sequence) in 26 patients with various cardiac diseases. In nine of the 26 patients, the null points of the RV myocardium were shorter than those of the LV myocardium in the Look–Locker sequence. The RV myocardial signals were significantly higher than the LV myocardial signals in delayed contrast-enhanced MR images. Thus, more attention should be paid to evaluation of the late enhancement of the RV myocardium, and delayed contrast-enhanced MR imaging with a shorter inversion time may be required in some cases.

Detection and characterization of intracardiac thrombi on MR imaging.

The aim of our study was to compare the diagnostic accuracy achieved using different MR techniques with the diagnostic accuracy achieved using transthoracic and transesophageal echocardiography to detect intracardiac thrombi. Twenty-four patients with known or suspected intracardiac thrombi were examined using MR imaging and echocardiography. All MR examinations were performed on a 1.5-T MR scanner using dark-blood-prepared half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences, fast imaging steady-state free precession (trueFISP) cine sequences, and inversion recovery gradient-echo fast low-angle-shot (inversion recovery turbo FLASH) sequences after injection of 0.2 mmol/kg of gadolinium diethylene triamine pentaacetic acid. MR imaging and echocardiography revealed 12 thrombi-two in the right atrium, one in the right ventricle, three in the left atrium, and six in the left ventricle. Compared with echocardiography, MR imaging revealed three additional thrombi in the left ventricle; these thrombi were confirmed at surgery. All 15 thrombi appeared as filling defects on early contrast-enhanced inversion recovery turbo FLASH MR images. Only seven thrombi were detected on HASTE images, and 10 thrombi were seen on trueFISP images. Four thrombi showed enhancement 10-20 min after contrast material injection and were characterized as organized clots. Contrast-enhanced inversion recovery turbo FLASH sequences were superior to dark-blood-prepared HASTE and trueFISP cine MR images in revealing intracardiac thrombi. Compared with transthoracic echocardiography, MR imaging was more sensitive for the detection of left ventricular thrombi. The characterization of thrombi may be used to predict the risk of embolism, which is higher for subacute clots than for organized thrombi.

Evaluation of software for registration of contrast-enhanced brain MR images in patients with glioblastoma multiforme.

We evaluated commercially available software that rapidly and automatically registers brain MR images on a clinical workstation, and we studied the accuracy of these registrations. Ten patients with a diagnosis of glioblastoma multiforme underwent contrast-enhanced inversion recovery prepared three-dimensional (3D) volumetric spoiled gradient-recalled acquisition in the steady state (SPGR) MR imaging (contiguous 1.5-mm slice thickness, 96-104 slices). After this imaging sequence, each patient was brought out of the head coil into a sitting position and then repositioned in the coil. The inversion recovery prepared 3D SPGR sequence was then repeated. A commercially available software program operating on a clinical workstation was used to automatically register the second inversion recovery prepared SPGR series to the first. The speed of registration was recorded. The accuracy of each registration was estimated by recording the coordinates of eight anatomic landmarks on the registered and reference series and by calculating the mean error among matching landmarks. In nine of 10 patients, the registration software produced a visually satisfactory registration. In one patient, a second registration was necessary to produce a satisfactory registration. The processing time for each iteration was 48.3 +/- 3.8 sec (mean +/- SD). The mean error in aligning matching anatomic landmarks ranged from 0.67 to 1.41 mm, with an overall mean of 1.18 mm. The largest error among matching landmarks was 2.3 mm. Commercially available registration software can automatically register 3D imaging volumes in less than 1 min. The mean error in registration was approximately equivalent to the dimensions of a single voxel.

Evaluation of myocardial function and perfusion in ischemic heart disease

Ischemic heart disease is the most frequently encountered cardiac disease. Magnetic resonance imaging (MRI) can be used to investigate several facets of this disease. A number of studies over the past several years have shown the capability of cine MRI for quantifying regional myocardial function and for identifying abnormalities of regional myocardial wall thickening in the basal or vasodilated states due to ischemia. Contrast-enhanced inversion recovery fast gradient echo and echo-planar imaging have been applied for monitoring the first passage of contrast media through the myocardium. This technique has depicted regional perfusion deficits in the basal state or in the vasodilated states induced by vasodilators. Recent studies have also disclosed the feasibility of using MR techniques for displaying the morphology of the major coronary arteries and for measuring blood flow velocity in the coronary arteries and coronary bypass grafts. Thus, MRI has the capability for evaluation of morphology and flow in the coronary arteries and for assessment of function and perfusion of the myocardium.