The need for ECG gating presents many difficulties in cardiac magnetic resonance imaging (CMRI). Real-time imaging techniques eliminate the need for ECG gating in cine CMRI, but they cannot offer the spatial and temporal resolution provided by segmented acquisition techniques. Previous MR signal-based techniques have demonstrated an ability to provide cardiac gating information; however, these techniques result in decreased imaging efficiency. The purpose of this work was to develop a new "self-gated" (SG) acquisition technique that eliminates these efficiency deficits by extracting the motion synchronization signal directly from the same MR signals used for image reconstruction. Three separate strategies are proposed for deriving the SG signal from data acquired using radial k-space sampling: echo peak magnitude, kymogram, and 2D correlation. The SG techniques were performed on seven normal volunteers. A comparison of the results showed that they provided cine image series with no significant differences in image quality compared to that obtained with conventional ECG gating techniques. SG techniques represent an important practical advance in clinical MRI because they enable the acquisition of high temporal and spatial resolution cardiac cine images without the need for ECG gating and with no loss in imaging efficiency.

Quantitative cardiovascular magnetic resonance (CMR) imaging can be used to characterize fibrosis, oedema, ischaemia, inflammation and other disease conditions. However, the need to reduce artefacts arising from body motion through a combination of electrocardiography (ECG) control, respiration control, and contrast-weighting selection makes CMR exams lengthy. Here, we show that physiological motions and other dynamic processes can be conceptualized as multiple time dimensions that can be resolved via low-rank tensor imaging, allowing for motion-resolved quantitative imaging with up to four time dimensions. This continuous-acquisition approach, which we name cardiovascular MR multitasking, captures — rather than avoids — motion, relaxation and other dynamics to efficiently perform quantitative CMR without the use of ECG triggering or breath holds. We demonstrate that CMR multitasking allows for T1 mapping, T1-T2 mapping and time-resolved T1 mapping of myocardial perfusion without ECG information and/or in free-breathing conditions. CMR multitasking may provide a foundation for the development of setup-free CMR imaging for the quantitative evaluation of cardiovascular health.

Pancreatic ductal adenocarcinoma (PDAC) is most frequently detected at an advanced stage. This limits treatment options and contributes to a dismal 5-year survival rate of 3 to 15%. PDAC is relatively uncommon and with current modalities, screening of the asymptomatic adult population is not feasible or recommended. However, screening of individuals in highrisk groups is undertaken. Here we review high-risk groups for PDAC, including individuals with inherited predisposition and patients with pancreatic cystic lesions. We discuss new studies aimed at finding ways of identifying PDAC in high-risk groups, such as individuals with new-onset diabetes mellitus and those attending primary and secondary care practices with suggestive symptoms. We review early detection biomarkers, explore the potential of exploiting social media for PDAC detection, appraise prediction models developed using electronic health records and research data, and examine the application of artificial intelligence to imaging for the purposes of early PDAC detection.

In five healthy subjects and 18 patients, cine magnetic resonance (MR) imaging of the heart was performed with a true fast imaging with steady-state precession (FISP) sequence. Results were compared both quantitatively and qualitatively with those at cine fast low-angle shot (FLASH) MR imaging. The blood-myocardial contrast-to-noise ratio (CNR) was 2.0 times higher and the normalized (for measurement time and pixel size) blood-myocardial CNR was 4.0 times higher for true FISP compared with FLASH MR imaging. Qualitative scores for image quality were significantly higher with true FISP MR imaging. Segmented cine true FISP MR imaging generated high-contrast MR images of the heart in healthy subjects and in patients with heart disease and produced image quality superior to that with cine FLASH MR imaging.

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 trains and inferences quickly, and the GAN promotes realistic output hardly distinguishable from original HR images. Our results from experiments on a dataset with 1,113 subjects shows that our new architecture outperforms other popular deep learning methods in recovering 4x resolutiondowngraded images and runs 6x faster.

The purpose of this work was to develop an ECG-triggered, segmented 3D true-FISP (fast imaging with steady-state precession) technique to improve the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of breath-hold coronary artery imaging. The major task was to optimize an appropriate magnetization preparation scheme to permit saturation of the epicardial fat signal. An ␣/2 preparation pulse was used to speed up the approach to steady-state following a frequencyselective fat-saturation pulse in each heartbeat. The application of dummy cycles was found to reduce the oscillation of the magnetization during data acquisition. The fat saturation and magnetization preparation scheme was validated with simulations and phantom studies. Volunteer studies demonstrated substantially increased SNR (55%) and CNR (178%) for coronary arteries compared to FLASH (fast low-angle shot) with the same imaging time. Volume-targeted breath-hold imaging (VCATS) has recently been described for MR angiography of the coronary arteries (1). VCATS employs a 3D steady-state incoherent gradient-echo sequence, FLASH (fast low-angle shot), for data acquisition. In such a sequence, the transverse magnetization is spoiled at the end of each repetition time (TR) to create T 1 -weighted contrast. As TR is shortened and bandwidth increased to speed up data acquisition, the available signal-to-noise ratio (SNR) becomes a limiting factor with FLASH. Injection of contrast media is necessary to shorten the blood T 1 to improve SNR and contrastto-noise ratio (CNR) (2-6).True-FISP (fast imaging with steady-state precession) has recently found important applications in cardiac cine imaging (7,8) for the evaluation of left ventricular function. Significant improvements in blood SNR and blood-myocardium CNR were obtained as compared to FLASH. In true-FISP, the transverse magnetization is maintained between successive RF pulses because the net gradient moments are zero in all three directions and no RF spoiling is implemented. Coherent transverse magnetization continues to contribute to the signal in successive TRs, resulting in a higher SNR than in magnetization-spoiled techniques such as FLASH. For the same reason, large flip angles close to 90°can be used in true-FISP because there are no saturation effects and the magnetization is restored and reused. Analysis using the Bloch equations predicts that the signal intensity in true-FISP is T 2 /T 1 -weighted. The contrast between blood and myocardium is therefore enhanced because blood has a much higher T 2 /T 1 than myocardium.The concept of true-FISP (9) and its applications in brain and spine imaging (10) were proposed years ago. However, because of the zero net applied gradients, there was no averaging of the resonant offsets and, with relatively long minimum TRs achievable at the time, the technique was extremely sensitive to field inhomogeneities and was not used in cardiac imaging. With recent improvements in gradient capabilities, short TRs on the order of 3-4 msec have been achieved. Comb...

Segmented cine MRI generally requires breath-holding, which can be problematic for many patients. Navigator echo techniques, particularly successful for free-breathing coronary MRA, are incompatible with the acquisition strategies and SSFP pulse sequences commonly used for cine MRI. The purpose of this work is to introduce a new self-gating technique deriving respiratory gating information directly from the raw imaging data acquired for segmented cine MRI. The respiratory selfgating technique uses interleaved radial k-space sampling to provide low-resolution images in real time during the freebreathing acquisition that are compared to target expiration images. Only the raw data-producing images with high correlation to the target images are included in the final high-resolution reconstruction. The self-gating technique produced cine series with no significant differences in quantitative image sharpness to series produced using comparable breath-held techniques. Because of the difficulties associated with breathholding, the respiratory self-gating technique represents an important practical advance for cardiac MRI.

Purpose To develop a cardiac and respiratory self-gated 4D coronary MRA technique for simultaneous cardiac anatomy and function visualization. Methods A contrast-enhanced, ungated spoiled gradient echo sequence with self-gating (SG) and 3DPR trajectory was used for image acquisition. Data was retrospectively binned into different cardiac and respiratory phases based on information extracted from SG projections using principal component analysis. Each cardiac phase was reconstructed using a respiratory motion-corrected self-calibrating SENSE framework, and those belong to the quiescent period were retrospectively combined for coronary visualization. Healthy volunteer studies were conducted to evaluate the efficacy of the SG method, the accuracy of the left ventricle (LV) function parameters and the quality of coronary artery visualization. Results SG performed reliably for all subjects including one with poor ECG. The LV function parameters showed excellent agreement with those from a conventional cine protocol. For coronary imaging, the proposed method yielded comparable apparent SNR and coronary sharpness and lower apparent CNR on three subjects compared with an ECG and navigator-gated Cartesian protocol and an ECG-gated, respiratory motion-corrected 3DPR protocol. Conclusion A fully self-gated 4D whole-heart imaging technique was developed, potentially allowing cardiac anatomy and function assessment from a single measurement.