28 research outputs found
Correction for non-uniform k-space data weighting effects in first-pass cardiac perfusion imaging with TurboFLASH readout
Rapid T1 quantification based on 3D phase sensitive inversion recovery
<p>Abstract</p> <p>Background</p> <p>In Contrast Enhanced Magnetic Resonance Imaging fibrotic myocardium can be distinguished from healthy tissue using the difference in the longitudinal <it>T</it><sub>1 </sub>relaxation after administration of Gadolinium, the so-called Late Gd Enhancement. The purpose of this work was to measure the myocardial absolute <it>T</it><sub>1 </sub>post-Gd from a single breath-hold 3D Phase Sensitivity Inversion Recovery sequence (PSIR). Equations were derived to take the acquisition and saturation effects on the magnetization into account.</p> <p>Methods</p> <p>The accuracy of the method was investigated on phantoms and using simulations. The method was applied to a group of patients with suspected myocardial infarction where the absolute difference in relaxation of healthy and fibrotic myocardium was measured at about 15 minutes post-contrast. The evolution of the absolute <it>R</it><sub>1 </sub>relaxation rate (1/<it>T</it><sub>1</sub>) over time after contrast injection was followed for one patient and compared to <it>T</it><sub>1 </sub>mapping using Look-Locker. Based on the <it>T</it><sub>1 </sub>maps synthetic LGE images were reconstructed and compared to the conventional LGE images.</p> <p>Results</p> <p>The fitting algorithm is robust against variation in acquisition flip angle, the inversion delay time and cardiac arrhythmia. The observed relaxation rate of the myocardium is 1.2 s<sup>-1</sup>, increasing to 6 - 7 s<sup>-1 </sup>after contrast injection and decreasing to 2 - 2.5 s<sup>-1 </sup>for healthy myocardium and to 3.5 - 4 s<sup>-1 </sup>for fibrotic myocardium. Synthesized images based on the <it>T</it><sub>1 </sub>maps correspond very well to actual LGE images.</p> <p>Conclusions</p> <p>The method provides a robust quantification of post-Gd <it>T</it><sub>1 </sub>relaxation for a complete cardiac volume within a single breath-hold.</p
FLASH proton density imaging for improved surface coil intensity correction in quantitative and semi-quantitative SSFP perfusion cardiovascular magnetic resonance
Optimization of dual-saturation single bolus acquisition for quantitative cardiac perfusion and myocardial blood flow maps
BACKGROUND: In-vivo quantification of cardiac perfusion is of great research and clinical value. The dual-bolus strategy is universally used in clinical protocols but has known limitations. The dual-saturation acquisition strategy has been proposed as a more accurate alternative, but has not been validated across the wide range of perfusion rates encountered clinically. Dual-saturation acquisition also lacks a clinically-applicable procedure for optimizing parameter selection. Here we present a comprehensive validation study of dual-saturation strategy in vitro and in vivo. METHODS: The impact of saturation time and profile ordering in acquisitions was systematically analyzed in a phantom consisting of 15 tubes containing different concentrations of contrast agent. In-vivo experiments in healthy pigs were conducted to evaluate the effect of R2* on the definition of the arterial input function (AIF) and to evaluate the relationship between R2* and R1 variations during first-pass of the contrast agent. Quantification by dual-saturation perfusion was compared with the reference-standard dual-bolus strategy in 11 pigs with different grades of myocardial perfusion. RESULTS: Adequate flow estimation by the dual-saturation strategy is achieved with myocardial tissue saturation times around 100 ms (always <30 ms of AIF), with the lowest echo time, and following a signal model for contrast conversion that takes into account the residual R2* effect and profile ordering. There was a good correlation and agreement between myocardial perfusion quantitation by dual-saturation and dual-bolus techniques (R(2) = 0.92, mean difference of 0.1 ml/min/g; myocardial perfusion ranges between 0.18 and 3.93 ml/min/g). CONCLUSIONS: The dual-saturation acquisition strategy produces accurate estimates of absolute myocardial perfusion in vivo. The procedure presented here can be applied with minimal interference in standard clinical procedures
Measurement of myocardial blood flow by cardiovascular magnetic resonance perfusion: comparison of distributed parameter and Fermi models with single and dual bolus
Carotid plaque high-resolution MRI at 3 T: evaluation of a new imaging score for symptomatic plaque assessment
[DOI:\hrefhttps://dx.doi.org/10.1016/j.mri.2012.04.02410.1016/j.mri.2012.04.024] [PubMed:\hrefhttps://www.ncbi.nlm.nih.gov/pubmed/2283594022835940]To assess the sensitivity and specificity of intra-plaque hemorrhage (IPH), large lipid-rich necrotic core (LR-NC) and ulceration or cap rupture (UCR) for symptomatic carotid plaque characterization and to evaluate a new imaging score [Hemorrhage, Ulceration or cap rupture, Lipid-rich necrotic Core (HULC) score based on the sum of presence/absence of IPH, UCR and LR-NC; range 0-3] for assessment of recently symptomatic carotid plaques.\ Twenty-seven recently symptomatic (<8 weeks) and 36 asymptomatic patients with a carotid plaque thicker than 2 mm were prospectively imaged on a 3-T magnetic resonance (MR) system using high-resolution, multi-contrast MR sequences. Prior to analysis, all images were reviewed to assess image quality of each sequence. Sensitivity and specificity of IPH, LR-NC, UCR and HULC scores were calculated.\ Fifty-one patients were analyzed (26 symptomatic carotids and 67 asymptomatic carotids) after exclusion of studies with poor image quality. Sensitivity and specificity for symptomatic carotid plaque was, respectively, 46.1% and 97% for IPH, 84.6% and 73.1% for UCR and 80.7% and 76.1% for LR-NC. A HULC score of 2 or more showed a sensitivity of 73% and a specificity of 92.5%.\ At 3 T, intra-plaque hemorrhage is the most specific criterion to characterize symptomatic carotid plaque. The HULC score offers the best compromise between sensitivity and specificity
4D time-resolved magnetic resonance angiography for noninvasive assessment of pulmonary arteriovenous malformations patency
[DOI:\hrefhttps://dx.doi.org/10.1002/jmri.2238410.1002/jmri.22384] [PubMed:\hrefhttps://www.ncbi.nlm.nih.gov/pubmed/2103151621031516]International audienceTo assess the capability of four-dimensional (4D) time-resolved magnetic resonance angiography (MRA) to assess pulmonary arteriovenous malformations (PAVMs) patency by analyzing pulmonary arterial and venous enhancement kinetics.\ Seven patients with eight documented patent PAVMs underwent a 4D-MRA with keyhole and viewsharing compression at 3T with the following parameters: spatial resolution 0.87 × 0.87 × 1.4 mm(3); field of view 500 × 350 × 238 mm(3); dynamic scan time (temporal resolution) 1.2 seconds; total acquisition time 18.1 seconds for six dynamic datasets (6 × 1.2 sec + reference scan: 10.9 sec). All images were reviewed by two experienced radiologists. Image quality was rated on a qualitative 5-point scale (1: not assessable to 5: excellent). Signal value was measured on cross-sectional planes for the afferent arteries and efferent veins of the PAVM, and for normal reference healthy arteries and veins. The difference in time to peak for each coupled artery/vein (dTTPav) was calculated and compared with a Mann-Whitney test between PAVMs and reference vessels.\ Mean image quality was 3.2 ± 0.9. dTTPav was significantly smaller in PAVMs (0.15 ± 0.76 sec) than in reference vessels (3.75 ± 1.62 sec), P < 0.001.\ 4D-MRA is a promising tool for noninvasive assessment of PAVM patency