Contrast-enhanced Coronary Magnetic Resonance Angiography Research Articles

Quiescent frame, contrast-enhanced coronary magnetic resonance angiography reconstructed using limited number of physiologic frames from 5D free-running acquisitions

Background5D, free-running imaging resolves sets of 3D whole-heart images in both cardiac and respiratory dimensions. In an application such as coronary imaging when a single, static image is of interest, computationally expensive offline iterative reconstruction is still needed to compute the multiple 3D datasets. PurposeEvaluate how the number of physiologic bins included in the reconstruction affects the computational cost and resulting image quality of a single, static volume reconstruction. Study typeRetrospective. Subjects15 pediatric patients following Ferumoxytol infusion (4 mg/kg). Field strength/Sequence1.5 T/Ungated 5D free-running GRE sequence. AssessmentThe raw data of each subject were binned and reconstructed into a 5D (x-y-z-cardiac-respiratory) images. 1, 3, 5, 7, and 9 bins adjacent to both sides of the retrospectively determined cardiac resting phase and 1, 3 bins adjacent to the end-expiration phase are used for limited frame reconstructions. The static volume within each limited reconstruction was compared with the corresponding full 5D reconstruction using the structural similarity index measure (SSIM). A non-linear regression model was used to fit SSIM with the percentage of data used compared to full reconstruction (% data). A linear regression model was used to fit computation time with % raw data used. Coronary artery sharpness is measured on each limited reconstructed images to determine the minimal number of cardiac and respiratory bins needed to preserve image quality. Statistical testsThe coefficient of determination (R2) is computed for each regression model. ResultsThe % of data used in the reconstruction was linearly related to the computational time (R2 = 0.99). The SSIM of the static image from the limited reconstructions is non-linearly related with the % of data used (R2 = 0.80). Over the 15 patients, the model showed SSIM of 0.9 with 18% of data, and SSIM of 0.96 with 30% of data. The coronary artery sharpness of images reconstructed using no less than 5 cardiac and all respiratory phases is not significantly different from the full reconstructed images using all cardiac and respiratory bins. Data conclusionReconstruction using only a limited number of acquired physiological states can linearly reduce the computational cost while preserving similarity to the full reconstruction image. It is suggested to use no less than 5 cardiac and all respiratory phases in the limited reconstruction to best preserve the original quality seen on the full reconstructed images.

Whole-Heart Coronary Magnetic Resonance Angiography at 1.5 Tesla

To evaluate the impact of the blood-pool contrast agent gadofosveset trisodium on diagnostic accuracy of whole-heart coronary magnetic resonance angiography (CMRA) at 1.5 Tesla. Thirty consecutive patients with suspected coronary artery disease underwent free-breathing whole-heart CMRA at 1.5 Tesla. CMRA was performed with a T2-prepared steady-state free precession sequence (unenhanced CMRA) and an inversion-recovery-prepared steady-state free precession sequence after administration of gadofosveset trisodium (contrast-enhanced CMRA). Two readers independently performed a per-segment evaluation of CMRA (8 proximal and mid coronary segments) for detection of significant stenosis (≥50%) using invasive coronary angiography as reference. Disagreement was settled by consensus reading and interobserver variability was assessed using an unweighted kappa statistic. Whole-heart CMRA was successfully performed in 27 patients. The percentage of assessable segments was significantly lower on unenhanced CMRA compared with contrast-enhanced CMRA (Reader 1: 79% [170/216] vs. 89% [192/216], respectively; Reader 2: 73% [157/216] vs. 87% [188/216], respectively; P < 0.001). Intention-to-diagnose analysis of the consensus reading yielded sensitivity, specificity, and diagnostic accuracy of unenhanced versus contrast-enhanced CMRA as follows: 73.1% versus 73.1% (P = 1.0), 68.3% versus 80.2% (P = 0.002), and 68.9% versus 79.3% (P = 0.004), respectively. The kappa value for interobserver agreement was 0.61 (95% confidence interval = 0.50-0.72) for unenhanced CMRA and 0.72 (95% confidence interval = 0.62-0.82) for contrast-enhanced CMRA. The blood-pool contrast agent gadofosveset trisodium increased the number of assessable coronary segments on whole-heart CMRA in comparison to unenhanced whole-heart CMRA. The impact of gadofosveset trisodium on diagnostic accuracy, however, was only minor.

Coronary MRA: Technical Advances and Clinical Applications

Magnetic resonance angiography (MRA) has become a routine clinical tool to evaluate arteries in the head and neck, abdomen, and extremities. However, coronary MRA (CMRA) is a more challenging task. A number of factors have hindered its progress, including: 1) the motion of the heart during cardiac and respiratory cycles; 2) the highly tortuous courses; and 3) the small sizes of coronary arteries. It is important to have an appropriate balance between signal-to-noise ratio (SNR), imaging speed, and spatial resolution when determining imaging parameters of CMRA. Whole heart CMRA at 1.5 T has been successfully introduced as a method of choice that can provide visualization of all three major coronary arteries in a single 3D volume. Recent single and multicenter studies suggest that 1.5 T whole heart CMRA can eliminate the need for diagnostic coronary catheterization in many patients at risk of coronary artery disease. 3.0 T cardiovascular MR has become an area of active research in recent years. Contrast-enhanced coronary MRA at 3.0 T improves SNR and contrast-to-noise ratio and shows high accuracy in the detection of significant coronary artery stenoses.

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.

Time-resolved contrast-enhanced coronary magnetic resonance angiography with highly constrained projection reconstruction

Contrast-enhanced magnetic resonance angiography (MRA) is a promising technique for coronary artery imaging. The blood signal changes during the contrast injection will result in image artifacts, blurring and relatively low signal-to-noise ratio, when the k-space segments from different cardiac cycles are combined to reconstruct the final image as "time averaged." Thus, it is important to acquire data during maximal blood signal enhancement for first-pass, contrast-enhanced MRA, and relatively high temporal resolution is required. This work demonstrated the feasibility of highly constrained backprojection reconstruction for time-resolved, contrast-enhanced coronary MRA. With this method, the temporal resolution can be increased. In addition, coronary artery images around blood signal enhancement peak have significantly improved contrast-to-noise ratio and suppressed artifacts compared to the composite images which were collected during a much longer acquisition time during substantial blood signal changes.

Whole-heart contrast-enhanced coronary magnetic resonance angiography in less than 5 minutes using gradient echo interleaved EPI

Whole-heart contrast-enhanced coronary magnetic resonance angiography in less than 5 minutes using gradient echo interleaved EPI

Subacute Thrombotic Occlusion and Spontaneous Recanalization of the Right Coronary Artery After Percutaneous Coronary Intervention for ST-Elevation Myocardial Infarction Visualized by Coronary Angiography and Cardiac Magnetic Resonance Imaging

A 58-year-old male was admitted to the emergency room with an acute inferior ST-elevation myocardial infarction (Figure 1). His coronary risk factors included arterial hypertension and hypercholesterolemia. Emergency percutaneous coronary intervention (PCI) was performed with stenting of the occluded right posterolateral branch with a 2.5×18 mm Zotarolimus-eluting stent (Medtronic, Minneapolis, Minn.) (Figure 1A and 1B). The left ventricular ejection fraction was 41% and the postinterventional TIMI flow was grade II with reduced flow of the entire right coronary artery (RCA) and persistent ST elevation within the inferior leads. The maximum creatine kinase level was 1863 U/L and peaked 36 hours after PCI. 99mTechnetium-sestamibi scans to assess coronary perfusion immediately before and 6 days after intervention (Figure 2) revealed no myocardial salvage subsequent to PCI within the inferior wall. Contrast-enhanced coronary magnetic resonance angiography with the use of 0.2 mmol/kg gadolinium-DTPA of the RCA 8 days after PCI revealed a signal void along …

Determination of Optimal Gadolinium Concentration Using SSFP for Catheter-directed Contrast-enhanced Coronary MR Angiography 1

To determine the optimal gadolinium concentration for catheter-directed coronary magnetic resonance angiography (MRA) using magnetization-prepared steady-state free-precession (SSFP) in swine. In six pigs, we performed real-time MR imaging-guided coronary artery catheterization using a 1.5 T MR scanner. For catheter-directed coronary MRA, we injected 3-4 mL of dilute Gd at 1 mL/second for each tested concentration (4%, 8%, 10%, and 12% Gd). Eleven images per concentration were acquired using electrocardiographic-triggered, magnetization-prepared two-dimensional (2D) projection SSFP. We compared mean relative signal-to-noise ratio (SNR) values for each concentration using two-way analysis of variance. The targeted coronary artery was catheterized under real-time MR guidance in all pigs. Magnetization-prepared 2D projection SSFP successfully depicted the coronary arteries in all 44 injections. Mean relative SNR (+/- standard error) was 7.2 +/- 0.49 for 4%, 8.8 +/- 0.47 for 8%, 9.5 +/- 0.38 for 10%, and 8.8 +/- 0.41 for 12%. Injections of 4% dilute gadolinium yielded significantly less relative SNR than the other tested concentrations (P < .05). There were no statistically significant differences between the remaining concentrations. For catheter-directed contrast-enhanced coronary MRA, the ideal gadolinium concentration should maximize relative SNR and limit the total gadolinium dose. Using these criteria, of those concentrations we tested in the swine model, 8% injected gadolinium was superior for catheter-directed SSFP coronary MRA.

Coronary arteries at 3.0 T: Contrast‐enhanced magnetization‐prepared three‐dimensional breathhold MR angiography

To evaluate the efficacy of contrast-enhanced coronary magnetic resonance angiography (MRA) at 3.0 T. Nine healthy human volunteers were studied on a 3.0-T whole-body MR system. A three-dimensional, breathhold, magnetization-prepared, segmented, gradient-echo sequence was used, with injection of 20 mL gadopentetate dimeglumine for each three-dimensional slab. Imaging parameters were optimized based on computer simulations. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), depicted coronary artery length, lumen diameter, and imaging sharpness with contrast agent were evaluated. SNR and CNR were compared to the results from a previous 1.5-T study. A 53% increment in SNR and a 305% enhancement in CNR were measured with contrast. Vessel length and sharpness depicted were higher and the lumen diameter was lower (all P values < 0.05) in postcontrast images. Compared to previous results from 1.5-T, the SNR, CNR, and vessel sharpness were enhanced at 3.0 T with higher spatial resolution. Contrast-enhanced, three-dimensional, coronary MRA at 3.0 T is a promising technique for diagnosing coronary artery diseases. Patient studies are necessary to evaluate its clinical utility.