A Novel Tissue-Free Method to Estimate Tumor-Derived Cell-Free DNA Quantity Using Tumor Methylation Patterns.

Estimating the abundance of cell-free DNA (cfDNA) fragments shed from a tumor (i.e., circulating tumor DNA (ctDNA)) can approximate tumor burden, which has numerous clinical applications.

Fat-based registration of breast dynamic contrast enhanced water images.

Purpose: In this study, a 3D fat-based deformable registration algorithm was developed for registering dynamic contrast-enhanced breast images.

Methods: The mutual information similarity measure with free-form deformation motion correction in rapidly enhancing lesions can introduce motion. However, in Dixon-based fat-water separated acquisitions, the nonenhancing fat signal can directly be used to estimate deformable motion, which can be later used to deform the water images.

Free-breathing variable flip angle balanced SSFP cardiac cine imaging with reduced SAR at 3T.

Purpose: To develop a free-breathing variable flip angle (VFA) balanced steady-state free precession (bSSFP) cardiac cine imaging technique with reduced specific absorption rate (SAR) at 3 Tesla.

Methods: Free-breathing VFA (FB-VFA) images in the short-axis and four-chamber views were acquired using an optimal VFA scheme, then compared with conventional breath-hold constant flip angle (BH-CFA) acquisitions. Two cardiac MRI experts used a 5-point scale to score images from healthy subjects (N = 10).

Fast 3D T2 -weighted imaging using variable flip angle transition into driven equilibrium (3D T2 -TIDE) balanced SSFP for prostate imaging at 3T.

Purpose: Three-dimensional (3D) T2 -weighted fast spin echo (FSE) imaging of the prostate currently requires long acquisition times. Our objective was to develop a fast 3D T2 -weighted sequence for prostate imaging at 3T using a variable flip angle transition into driven equilibrium (T2 -TIDE) scheme.

Methods: 3D T2 -TIDE uses interleaved spiral-out phase encode ordering to efficiently sample the ky -kz phase encodes and also uses the transient balanced steady-state free precession signal to acquire the center of k-space for T2 -weighted imaging.

Complementary radial tagging for improved myocardial tagging contrast.

Purpose: To develop and evaluate complementary radial tagging (CRT) for improved myocardial tagging contrast.

Methods: We sought to develop and evaluate CRT, which aims to preserve the radial tag contrast throughout the cardiac cycle. Similar to complementary spatial modulation of magnetization, CRT acquires two sets of images with a phase shift in the tag pattern.

Optimal flip angle for high contrast balanced SSFP cardiac cine imaging.

Purpose: To determine the optimal flip angle (FA) for cardiac cine imaging that maximizes myocardial signal and blood-myocardium contrast.

Methods: Bloch equation simulations of stationary myocardium and flowing blood with an imperfect slice profile were compared to in vivo measurements of blood and myocardium signal-to-noise ratio (SNR) and blood-myocardium contrast-to-noise ratio (CNR) in healthy subjects (N = 10) in the short-axis and four-chamber views and in patients (N = 7) in the three-chamber imaging plane.

Results: Left ventricular (LV) and right ventricular (RV) blood SNR and blood-myocardium CNR increases with increasing FA up to ≈105° in the short-axis view.

Modeling and incorporating cardiac-induced lung tissue motion in a breathing motion model.

Purpose: The purpose of this work is to develop a cardiac-induced lung motion model to be integrated into an existing breathing motion model.

Methods: The authors' proposed cardiac-induced lung motion model represents the lung tissue's specific response to the subject's cardiac cycle. The model is mathematically defined as a product of a converging polynomial function h of the cardiac phase (c) and the maximum displacement y(X0) of each voxel (X0) among all the cardiac phases.

Noncontrast enhanced four-dimensional dynamic MRA with golden angle radial acquisition and K-space weighted image contrast (KWIC) reconstruction.

Purpose: To explore the feasibility of 2D and 3D golden-angle radial acquisition strategies in conjunction with k-space weighted image contrast (KWIC) temporal filtering to achieve noncontrast enhanced dynamic MRA (dMRA) with high spatial resolution, low streaking artifacts and high temporal fidelity.

Methods: Simulations and in vivo examinations in eight normal volunteers and an arteriovenous malformation patient were carried out. Both 2D and 3D golden angle radial sequences, preceded by spin tagging, were used for dMRA of the brain.

Variable flip angle balanced steady-state free precession for lower SAR or higher contrast cardiac cine imaging.

Purpose: Cardiac cine balanced steady-state free precession (bSSFP) imaging uses a high flip angle (FA) to obtain high blood-myocardium signal-to-noise and contrast-to-noise ratios (CNR). Use of high FAs, however, results in substantially increased SAR. Our objective was to develop a variable FA bSSFP cardiac cine imaging technique with: (1) low SAR and blood-myocardium CNR similar to conventional constant FA bSSFP (CFA-bSSFP) or (2) increased blood-myocardium CNR compared to CFA-bSSFP with similar SAR.

Free-breathing 3D whole-heart black-blood imaging with motion sensitized driven equilibrium.

Purpose: To assess the efficacy and robustness of motion sensitized driven equilibrium (MSDE) for blood suppression in volumetric 3D whole-heart cardiac MR.

Materials And Methods: To investigate the efficacy of MSDE on blood suppression and myocardial signal-to-noise ratio (SNR) loss on different imaging sequences, seven healthy adult subjects were imaged using 3D electrocardiogram (ECG)-triggered MSDE-prep T(1) -weighted turbo spin echo (TSE), and spoiled gradient echo (GRE), after optimization of MSDE parameters in a pilot study of five subjects. Imaging artifacts, myocardial and blood SNR were assessed.