The authors compared prospective (n = 20) and retrospective (n = 20) electrocardiography (ECG)-assisted multi-detector row computed tomography (CT) with non-ECG-assisted multi-detector row CT (n = 20) of the thoracic aorta with regard to reduction of motion-related artifacts. Image quality was rated for transverse source and sagittal oblique images of the thoracic aorta, including the aortic valve. ECG-assisted multi-detector row CT compared with non-ECG-assisted multi-detector row CT showed a significant reduction in motion artifacts for the entire thoracic aorta.

Although xenon is classically taught to be a "perfusion-limited" gas, (129)Xe in its hyperpolarized (HP) form, when detected by magnetic resonance (MR), can probe diffusion limitation. Inhaled HP (129)Xe diffuses across the pulmonary blood-gas barrier, and, depending on its tissue environment, shifts its resonant frequency relative to the gas-phase reference (0 ppm) by 198 ppm in tissue/plasma barrier and 217 ppm in red blood cells (RBCs). In this work, we hypothesized that in patients with idiopathic pulmonary fibrosis (IPF), the ratio of (129)Xe spectroscopic signal in the RBCs vs. barrier would diminish as diffusion-limitation delayed replenishment of (129)Xe magnetization in RBCs. To test this hypothesis, (129)Xe spectra were acquired in 6 IPF subjects as well as 11 healthy volunteers to establish a normal range. The RBC:barrier ratio was 0.55 ± 0.13 in healthy volunteers but was 3.3-fold lower in IPF subjects (0.16 ± 0.03, P = 0.0002). This was caused by a 52% reduction in the RBC signal (P = 0.02) and a 58% increase in the barrier signal (P = 0.01). Furthermore, the RBC:barrier ratio strongly correlated with lung diffusing capacity for carbon monoxide (DLCO) (r = 0.89, P < 0.0001). It exhibited a moderate interscan variability (8.25%), and in healthy volunteers it decreased with greater lung inflation (r = -0.78, P = 0.005). This spectroscopic technique provides a noninvasive, global probe of diffusion limitation and gas-transfer impairment and forms the basis for developing 3D MR imaging of gas exchange.

Purpose We sought to develop and test a clinically feasible 1-point Dixon, 3D radial acquisition strategy to create isotropic 3D MR images of 129Xe in the airspaces, barrier, and red blood cells (RBCs) in a single breath. The approach was evaluated in healthy volunteers and subjects with idiopathic pulmonary fibrosis (IPF). Methods A calibration scan determined the TE at which 129Xe in RBCs and barrier were 90° out of phase. At this TE, interleaved dissolved and gas-phase images were acquired using a 3D radial acquisition and were reconstructed separately using the NUFFT algorithm. The dissolved-phase image was phase-shifted to cast RBC and barrier signal into the real and imaginary channels such that the image-derived RBC:barrier ratio matched that from spectroscopy. The RBC and barrier images were further corrected for regional field inhomogeneity using a phase map created from the gas-phase 129Xe image. Results Healthy volunteers exhibited largely uniform 129Xe-barrier and 129Xe-RBC images. By contrast, 129Xe-RBC images in IPF subjects exhibited significant signal voids. These voids correlated qualitatively with regions of fibrosis visible on CT. Conclusions This study illustrates the feasibility of acquiring single-breath, 3D isotropic images of 129Xe in the airspaces, barrier, and RBCs using a 1-point Dixon 3D radial acquisition.

Purpose We sought to develop and test a clinically feasible 1‐point Dixon, three‐dimensional (3D) radial acquisition strategy to create isotropic 3D MR images of 129Xe in the airspaces, barrier, and red blood cells (RBCs) in a single breath. The approach was evaluated in healthy volunteers and subjects with idiopathic pulmonary fibrosis (IPF). Methods A calibration scan determined the echo time at which 129Xe in RBCs and barrier were 90° out of phase. At this TE, interleaved dissolved and gas‐phase images were acquired using a 3D radial acquisition and were reconstructed separately using the NUFFT algorithm. The dissolved‐phase image was phase‐shifted to cast RBC and barrier signal into the real and imaginary channels such that the image‐derived RBC:barrier ratio matched that from spectroscopy. The RBC and barrier images were further corrected for regional field inhomogeneity using a phase map created from the gas‐phase 129Xe image. Results Healthy volunteers exhibited largely uniform 129Xe‐barrier and 129Xe‐RBC images. By contrast, 129Xe‐RBC images in IPF subjects exhibited significant signal voids. These voids correlated qualitatively with regions of fibrosis visible on CT. Conclusions This study illustrates the feasibility of acquiring single‐breath, 3D isotropic images of 129Xe in the airspaces, barrier, and RBCs using a 1‐point Dixon 3D radial acquisition. Magn Reson Med 75:1434–1443, 2016. © 2015 Wiley Periodicals, Inc.

Segmentation of the lungs in chest computed tomography (CT) is often performed as a preprocessing step in lung imaging. This task is complicated especially in presence of disease. This paper presents a lung segmentation algorithm called Adaptive Border Marching (ABM). Its novelty lies in the fact that it smoothes the lung border in a geometric way and can be used to reliably include juxtapleural nodules while minimizing oversegmentation of adjacent regions such as the abdomen and mediastinum. Our experiments using 20 datasets demonstrate that this computational geometry algorithm can re-include all juxtapleural nodules and achieve an average oversegmentation ratio of 0.43% and an average undersegmentation ratio of 1.63% relative to an expert determined reference standard. The segmentation time of a typical case is under 1 minute on a typical PC. As compared to other available methods, ABM is more robust, more efficient and more straightforward to implement, and once the chest CT images are input, there is no further interaction needed from users. The clinical impact of this method is in potentially avoiding false negative CAD findings due to juxtapleural nodules and improving volumetry and doubling time accuracy.

Relationships between reader search, recognition and acceptance, and overall lung nodule detection rate can be studied with eye tracking. Radiologists appear to actively search less than half of the lung parenchyma, with substantial interreader variation in volume searched, fraction of nodules included within the search volume, sensitivity for nodules within the search volume, and overall detection rate.

Active hemorrhage in patients after blunt abdominal trauma is most frequently visible as a jet of extravasated contrast agent on multidetector CT. When extravasation is detected, immediate surgical or angiographic therapy is required.

Contrast-enhanced retrospectively ECG-gated multi-detector row CT allows determination of aortic valve morphology, measurement of the diameter of the aortic valve annulus, and assessment of the degree of aortic valve calcification in patients with aortic stenosis.