Yibin Xie

In vivo contrast free chronic myocardial infarction characterization using diffusion-weighted cardiovascular magnetic resonance

BackgroundDespite the established role of late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) in characterizing chronic myocardial infarction (MI), a significant portion of chronic MI patients are contraindicative for the use of contrast agents. One promising alternative contrast free technique is diffusion weighted CMR (dwCMR), which has been shown ex vivo to be sensitive to myocardial fibrosis. We used a recently developed in vivo dwCMR in chronic MI pigs to compare apparent diffusion coefficient (ADC) maps with LGE imaging for infarct characterization.MethodsIn eleven mini pigs, chronic MI was induced by complete occlusion of the left anterior descending artery for 150 minutes. LGE, cine, and dwCMR imaging was performed 8 weeks post MI. ADC maps were derived from three orthogonal diffusion directions (b = 400 s/mm2) and one non-diffusion weighted image. Two semi-automatic infarct classification methods, threshold and full width half max (FWHM), were performed in both LGE and ADC maps. Regional wall motion (RWM) analysis was performed and compared to ADC maps to determine if any observed ADC change was significantly influenced by bulk motion.ResultsADC of chronic MI territories was significantly increased (threshold: 2.4 ± 0.3 μm2/ms, FWHM: 2.4 ± 0.2 μm2/ms) compared to remote myocardium (1.4 ± 0.3 μm2/ms). RWM was significantly reduced (threshold: 1.0 ± 0.4 mm, FWHM: 0.9 ± 0.4 mm) in infarcted regions delineated by ADC compared to remote myocardium (8.3 ± 0.1 mm). ADC-derived infarct volume and location had excellent agreement with LGE. Both LGE and ADC were in complete agreement when identifying transmural infarcts. Additionally, ADC was able to detect LGE-delineated infarcted segments with high sensitivity, specificity, PPV, and NPV. (threshold: 0.88, 0.93, 0.87, and 0.94, FWHM: 0.98, 0.97, 0.93, and 0.99, respectively).ConclusionsIn vivo diffusion weighted CMR has potential as a contrast free alternative for LGE in characterizing chronic MI.

Improved black‐blood imaging using DANTE‐SPACE for simultaneous carotid and intracranial vessel wall evaluation

The purpose of this study was to develop a three‐dimensional black blood imaging method for simultaneously evaluating the carotid and intracranial arterial vessel walls with high spatial resolution and excellent blood suppression with and without contrast enhancement.

Early Detection and Quantification of Cerebral Venous Thrombosis by Magnetic Resonance Black-Blood Thrombus Imaging

Background and Purpose— Early diagnosis of cerebral venous thrombosis (CVT) is currently a major clinical challenge. We proposed a novel magnetic resonance black-blood thrombus imaging technique (MRBTI) for detection and quantification of CVT. Methods— MRBTI was performed on 23 patients with proven CVT and 24 patients with negative CVT confirmed by conventional imaging techniques. Patients were divided into 2 groups based on the duration of clinical onset: ⩽7 days (group 1) and between 7 and 30 days (group 2). Signal/noise ratio was calculated for the detected thrombus, and contrast/noise ratio was measured between thrombus and lumen and also between thrombus and brain tissue. The feasibility of using MRBTI for thrombus volume measurement was explored, and total thrombus volume was calculated for each patient. Results— In 23 patients with proven CVT, MRBTI correctly identified 113 of 116 segments with a sensitivity of 97.4%. Thrombus signal/noise ratio was 153±57 and 261±95 for group 1 (n=10) and group 2 (n=13), respectively (P<0.01). Thrombus to lumen contrast/noise ratio was 149±57 and 256±94 for group 1 and group 2, respectively. Thrombus to brain tissue contrast/noise ratio was 41±36 and 120±63 (P<0.01), respectively. Quantification of thrombus volume was successfully conducted in all patients with CVT, and mean volume of thrombus was 10.5±6.9 mL. Conclusions— The current findings support that with effectively suppressed blood signal, MRBTI allows selective visualization of thrombus as opposed to indirect detection of venous flow perturbation and can be used as a promising first-line diagnostic imaging tool.

Multi-contrast atherosclerosis characterization (MATCH) of carotid plaque with a single 5-min scan: technical development and clinical feasibility

BackgroundMulti-contrast weighted imaging is a commonly used cardiovascular magnetic resonance (CMR) protocol for characterization of carotid plaque composition. However, this approach is limited in several aspects including low slice resolution, long scan time, image mis-registration, and complex image interpretation. In this work, a 3D CMR technique, named Multi-contrast Atherosclerosis Characterization (MATCH), was developed to mitigate the above limitations.MethodsMATCH employs a 3D spoiled segmented fast low angle shot readout to acquire data with three different contrast weightings in an interleaved fashion. The inherently co-registered image sets, hyper T1-weighting, gray blood, and T2-weighting, are used to detect intra-plaque hemorrhage (IPH), calcification (CA), lipid-rich necrotic core (LRNC), and loose-matrix (LM). The MATCH sequence was optimized by computer simulations and testing on four healthy volunteers and then evaluated in a pilot study of six patients with carotid plaque, using the conventional multi-contrast protocol as a reference.ResultsOn MATCH images, the major plaque components were easy to identify. Spatial co-registration between the three image sets with MATCH was particularly helpful for the reviewer to discern co-existent components in an image and appreciate their spatial relation. Based on Cohen’s kappa tests, moderate to excellent agreement in the image-based or artery-based component detection between the two protocols was obtained for LRNC, IPH, CA, and LM, respectively. Compared with the conventional multi-contrast protocol, the MATCH protocol yield significantly higher signal contrast ratio for IPH (3.1 ± 1.3 vs. 0.4 ± 0.3, p < 0.001) and CA (1.6 ± 1.5 vs. 0.7 ± 0.6, p = 0.012) with respect to the vessel wall.ConclusionsTo the best of our knowledge, the proposed MATCH sequence is the first 3D CMR technique that acquires spatially co-registered multi-contrast image sets in a single scan for characterization of carotid plaque composition. Our pilot clinical study suggests that the MATCH-based protocol may outperform the conventional multi-contrast protocol in several respects. With further technical improvements and large-scale clinical validation, MATCH has the potential to become a CMR method for assessing the risk of plaque disruption in a clinical workup.

High resolution 3D diffusion cardiovascular magnetic resonance of carotid vessel wall to detect lipid core without contrast media

BackgroundWithout the need of contrast media, diffusion-weighted imaging (DWI) has shown great promise for accurate detection of lipid-rich necrotic core (LRNC), a well-known feature of vulnerable plaques. However, limited resolution and poor image quality in vivo with conventional single-shot diffusion-weighted echo planar imaging (SS-DWEPI) has hindered its clinical application. The aim of this work is to develop a diffusion-prepared turbo-spin-echo (DP-TSE) technique for carotid plaque characterization with 3D high resolution and improved image quality.MethodsUnlike SS-DWEPI where the diffusion encoding is integrated in the EPI framework, DP-TSE uses a diffusion encoding module separated from the TSE framework, allowing for segmented acquisition without the sensitivity to phase errors. The interleaved, motion-compensated sequence was designed to enable 3D black-blood DWI of carotid arteries with sub-millimeter resolution. The sequence was tested on 12 healthy subjects and compared with SS-DWEPI for image quality, vessel wall visibility, and vessel wall thickness measurements. A pilot study was performed on 6 patients with carotid plaques using this sequence and compared with conventional contrast-enhanced multi-contrast 2D TSE as the reference.ResultsDP-TSE demonstrated advantages over SS-DWEPI for resolution and image quality. In the healthy subjects, vessel wall visibility was significantly higher with diffusion-prepared TSE (p < 0.001). Vessel wall thicknesses measured from diffusion-prepared TSE were on average 35% thinner than those from the EPI images due to less distortion and partial volume effect (p < 0.001). ADC measurements of healthy carotid vessel wall are 1.53 ± 0.23 × 10−3 mm2/s. In patients the mean ADC measurements in the LRNC area were significantly lower (0.60 ± 0.16×10−3 mm2/s) than those of the fibrous plaque tissue (1.27 ± 0.29 × 10−3 mm2/s, p < 0.01).ConclusionsDiffusion-prepared CMR allows, for the first time, 3D DWI of the carotid arterial wall in vivo with high spatial resolution and improved image quality over SS-DWEPI. It can potentially detect LRNC without the use of contrast agents, allowing plaque characterization in patients with renal insufficiency.

In vivo diffusion-tensor MRI of the human heart on a 3 tesla clinical scanner: An optimized second order (M2) motion compensated diffusion-preparation approach.

To optimize a diffusion‐prepared balanced steady‐state free precession cardiac MRI (CMR) technique to perform diffusion‐tensor CMR (DT‐CMR) in humans on a 3 Tesla clinical scanner

3D high-resolution diffusion-weighted MRI at 3T: Preliminary application in prostate cancer patients undergoing active surveillance protocol for low-risk prostate cancer

To improve spatial resolution and image quality of diffusion‐weighted (DW) MRI in detecting low‐risk prostate cancer (lrPC) in patients undergoing active surveillance protocol (AS‐PC), we propose the application of a diffusion‐prepared balanced steady‐state free precession (bSSFP) technique capable of multishot acquisition.

DANTE-prepared three-dimensional FLASH: A fast isotropic-resolution MR approach to morphological evaluation of the peripheral arterial wall at 3 Tesla.

To develop and assess a sequence using DANTE dark‐blood preparation combined with FLASH readout (DANTE‐FLASH) for rapid isotropic‐resolution three‐dimensional (3D) peripheral vessel wall imaging at 3 Tesla (T).

Efficient and Accurate MRI Super-Resolution Using a Generative Adversarial Network and 3D Multi-level Densely Connected Network

High-resolution (HR) magnetic resonance images (MRI) provide detailed anatomical information important for clinical application and quantitative image analysis. However, HR MRI conventionally comes at the cost of longer scan time, smaller spatial coverage, and lower signal-to-noise ratio (SNR). Recent studies have shown that single image super-resolution (SISR), a technique to recover HR details from one single low-resolution (LR) input image, could provide high-quality image details with the help of advanced deep convolutional neural networks (CNN). However, deep neural networks consume memory heavily and run slowly, especially in 3D settings. In this paper, we propose a novel 3D neural network design, namely a multi-level densely connected super-resolution network (mDCSRN) with generative adversarial network (GAN)-guided training. The mDCSRN quickly trains and inferences and the GAN promotes realistic output hardly distinguishable from original HR images. Our results from experiments on a dataset with 1,113 subjects show that our new architecture beats other popular deep learning methods in recovering 4x resolution-downgraded im-ages and runs 6x faster.

Motion-corrected imaging of the aortic valve with (18)F-NaF PET/CT and PET/MR: a feasibility study

We investigated whether motion correction of gated 18F-fluoride PET/CT and PET/MRI of the aortic valve could improve PET quantitation and image quality. Methods: A diffeomorphic, mass-preserving, anatomy-guided registration algorithm was used to align the PET images from 4 cardiac gates, preserving all counts, and apply them to the PET/MRI and PET/CT data of 6 patients with aortic stenosis. Measured signal-to-noise ratios (SNRs) and target-to-background ratios (TBRs) were compared with the standard method of using only the diastolic gate. Results: High-intensity aortic valve 18F-fluoride uptake was observed in all patients. After motion correction, SNR and TBR increased compared with the median diastolic gate (SNR, 51.61 vs. 21.0; TBR, 2.85 vs. 2.22) and the median summed data (SNR, 51.61 vs. 34.10; TBR, 2.85 vs. 1.95) (P = 0.028 for all). Furthermore, noise decreased from 0.105 (median, diastolic) to 0.042 (median, motion-corrected) (P = 0.028). Conclusion: Motion correction of hybrid 18F-fluoride PET markedly improves SNR, resulting in improved image quality.