† People involved in the organization of the challenge. ‡ People contributing data from their institutions.§ Equal senior authors.

A new system for catheter steering is presented that allows large deflections through the use of an integrated array of steering coils. Additionally, two imaging techniques for tracking the catheter tip and visualization of surrounding areas, without interference from the active catheter, were shown. Together the demonstrated steerable catheter, control system and the imaging techniques will ultimately contribute to the development of a steerable system for interventional MRI procedures.

Quantifying the extent and evolution of cerebral edema developing after stroke is an important but challenging goal. Lesional net water uptake (NWU) is a promising CT-based biomarker of edema, but its measurement requires manually delineating infarcted tissue and mirrored regions in the contralateral hemisphere. We implement an imaging pipeline capable of automatically segmenting the infarct region and calculating NWU from both baseline and follow-up CTs of large-vessel occlusion (LVO) patients. Infarct core is extracted from CT perfusion images using a deconvolution algorithm while infarcts on follow-up CTs were segmented from non-contrast CT (NCCT) using a deep-learning algorithm. These infarct masks were flipped along the brain midline to generate mirrored regions in the contralateral hemisphere of NCCT; NWU was calculated as one minus the ratio of densities between regions, removing voxels segmented as CSF and with HU outside thresholds of 20–80 (normal hemisphere and baseline CT) and 0–40 (infarct region on follow-up). Automated results were compared with those obtained using manually-drawn infarcts and an ASPECTS region-of-interest based method that samples densities within the infarct and normal hemisphere, using intraclass correlation coefficient (ρ). This was tested on serial CTs from 55 patients with anterior circulation LVO (including 66 follow-up CTs). Baseline NWU using automated core was 4.3% (IQR 2.6–7.3) and correlated with manual measurement (ρ = 0.80, p < 0.0001) and ASPECTS (r = −0.60, p = 0.0001). Automatically segmented infarct volumes (median 110-ml) correlated to manually-drawn volumes (ρ = 0.96, p < 0.0001) with median Dice similarity coefficient of 0.83 (IQR 0.72–0.90). Automated NWU was 24.6% (IQR 20–27) and highly correlated to NWU from manually-drawn infarcts (ρ = 0.98) and the sampling-based method (ρ = 0.68, both p < 0.0001). We conclude that this automated imaging pipeline is able to accurately quantify region of infarction and NWU from serial CTs and could be leveraged to study the evolution and impact of edema in large cohorts of stroke patients.

Resolution Enhanced TOSSI is a new MRI pulse sequence for the generation of rapid T2 contrast with high spatial resolution. TOSSI provides T2 contrast by using non-equally spaced inversion pulses throughout a bSSFP acquisition. In RE-TOSSI, these energy and time intensive adiabatic inversion pulses and associated magnetization preparation are removed from TOSSI after acquisition of the data around the center of k-space. Magnetization evolution simulations demonstrate T2 contrast in TOSSI as well as reduction in the widening of the point spread function width (by up to a factor of 4) to a near ideal case for RE-TOSSI. Phantom experimentation is used to characterize and compare the contrast and spatial resolution properties of TOSSI, RE-TOSSI, bSSFP, HASTE and TSE and to optimize the fraction of k-space acquired using TOSSI. Comparison images in the abdomen and brain demonstrate similar contrast and improved spatial resolution in RE-TOSSI compared to TOSSI. Comparison bSSFP, HASTE and TSE images are provided. RE-TOSSI is capable of providing high spatial resolution T2-weighted images in 1 second or less per image.

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Acute kidney injury (AKI) in premature neonates is common due to the administration of life‐saving therapies. The impact of AKI on renal morphology and susceptibility to further renal damage is poorly understood. Recent advances in radiological imaging have allowed integration of soft tissue morphology in the intact organ, facilitating a more complete understanding of changes in tissue microstructure associated with pathology. Here, we applied magnetic resonance imaging (MRI) to detect both glomerular and vascular changes in a rabbit model of neonatal AKI, induced by indomethacin and gentamicin. Using combined spin‐echo MRI and cationic ferritin enhanced gradient‐echo MRI (CFE‐MRI), we observed (a) an increased cortical arterial diameter in the AKI cohort compared to healthy controls, and (b) focal loss of vascular density and glomerular loss in a circumferential band ~1 mm from the cortical surface. This combined use of vascular and glomerular imaging may give insight into the etiology of AKI and its impact on renal health later in life.

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Positron emission mammography (PEM) has promise as an effective method for the detection of breast lesions. Perhaps the most significant design feature of a PEM system is the choice of scintillator material. In this investigation we compared three scintillators for use in PEM: NaI(Tl), gadolinium oxyorthosilicate (GSO), and lutetium-gadolinium oxyorthosilicate (LGSO). The PEM systems consisted of two 30 30 arrays of pixelated scintillators (3 3 10 mm 3 for GSO and LGSO and 3 3 19 mm 3 for NaI(Tl)) coupled to arrays of square position-sensitive photomultiplier tubes. The Compton scatter fraction, system energy resolution, spatial resolution, spatial resolution uniformity, and detection sensitivity were compared.Compton scatter fractions for the systems were comparable, between 8% and 9%. The NaI(Tl) system produced the best system energy resolution (18.2%), the GSO system had the worst system energy resolution (28.7%). Spatial resolution for each system was relatively uniform across the face of the detectors, though the magnitude was dependent upon scintillator material. The NaI(Tl) system produced the lowest mean resolution (3.54 0.05 mm for horizontal profiles and 3.51 0.04 mm for vertical profiles), while the LGSO system produced the greatest mean spatial resolution (3.19 0.04 mm for horizontal profiles and 3.20 0.03 mm for vertical profiles). Detection sensitivity varied among the three systems: NaI(Tl) = 217 7 c/s/kBq/ml, GSO = 383 9 c/s/kBq/ml and LGSO = 646 9 c/s/kBq/ml. Imaging of a simulated breast containing various sized spheres demonstrated that the LGSO system produced the greatest detectability for small spheres (as gauged by the contrast-to-noise ratio), while the NaI(Tl) system had the worst detectability. These differences were due mainly to the lower sensitivity of the NaI(Tl) system compared to the LGSO and GSO imagers. This investigation demonstrated the very important connection between scintillator selection and performance of PEM systems.