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To provide food security for a growing world population, it will be necessary to increase yields of staple crops such as wheat (Triticum aestivum L.). Yield is a complex, polygenic trait influenced by grain weight and number, which are negatively correlated with one another. Spikelet number is an important determinant of grain number, but allelic variants impacting its expression are often associated with heading date, constraining their use in wheat germplasm that must be adapted for specific environments. Identification and characterization of genetic variants affecting spikelet number will increase selection efficiency through their deployment in breeding programs. In this study, a quantitative trait locus (QTL) on chromosome arm 6BL for spikelet number was identified and validated using an association mapping panel, a recombinant inbred line population, and seven derived heterogeneous inbred families. The superior allele, QSn.csu-6Bb, was associated with an increase of 0.248 to 0.808 spikelets per spike across multiple environments that varied for mean spikelet number. Despite epistatic interactions between QSn.csu-6B and three other loci (WAPO-A1, VRN-D3, and PPD-B1), genotypes with a greater number of superior alleles at these loci consistently exhibit higher spikelet number. The frequency of superior alleles at these loci varies among winter wheat varieties adapted to different latitudes of the US Great Plains, revealing opportunities for breeders to select for increased spikelet number using simple molecular markers. This work lays the foundation for the positional cloning of the genetic variant underlying the QSn.csu-6B QTL to strengthen our understanding of spikelet number determination in wheat.

This study aimed to evaluate image quality and diagnostic performance of a recently developed navigated three-dimensional magnetic resonance cholangiopancreatography (3D-MRCP) with compressed sensing (CS) based on parallel imaging (PI) and conventional 3D-MRCP with PI only in patients with abnormal bile duct dilatation. This institutional review board-approved study included 45 consecutive patients [non-malignant common bile duct lesions (n = 21) and malignant common bile duct lesions (n = 24)] who underwent MRCP of the abdomen to evaluate bile duct dilatation. All patients were imaged at 3T (MR 750, GE Healthcare, Waukesha, WI) including two kinds of 3D-MRCP using 352 × 288 matrices with and without CS based on PI. Two radiologists independently and blindly assessed randomized images. CS acceleration reduced the acquisition time on average 5 min and 6 s to a total of 2 min and 56 s. The all CS cine image quality was significantly higher than standard cine MR image for all quantitative measurements. Diagnostic accuracy for benign and malignant lesions is statistically different between standard and CS 3D-MRCP. Total image quality and diagnostic accuracy at biliary obstruction evaluation demonstrates that CS-accelerated 3D-MRCP sequences can provide superior quality of diagnostic information in 42.5% less time. This has the potential to reduce motion-related artifacts and improve diagnostic efficacy.

The purpose of this work is to evaluate the repeatability of a compressed sensing (CS) accelerated multi-contrast carotid protocol at 3 T. Twelve volunteers and eight patients with carotid disease were scanned on a 3 T MRI scanner using a CS accelerated 3-D black-blood multi-contrast protocol which comprises T 1w, T 2w and PDw without CS, and with a CS factor of 1.5 and 2.0. The volunteers were scanned twice, the lumen/wall area and wall thickness were measured for each scan. Eight patients were scanned once, the inter/intra-observer reproducibility of the measurements was calculated. In the repeated volunteer scans, the interclass correlation coefficient (ICC) for the wall area measurement using a CS factor of 1.5 in PDw, T 1w and T 2w were 0.95, 0.81, and 0.97, respectively. The ICC for lumen area measurement using a CS factor of 1.5 in PDw, T 1w and T 2w were 0.96, 0.92, and 0.96, respectively. In patients, the ICC for inter/intra-observer measurements of lumen/wall area, and wall thickness were all above 0.81 in all sequences. The results show a CS accelerated 3-D black-blood multi-contrast protocol is a robust and reproducible method for carotid imaging. Future protocol design could use CS to reduce the scanning time.

The optimum slice location within the pulmonary root to quantify pulmonary valve haemodynamics was examined using magnetic resonance (MR) phase velocity mapping. MRI was carried out on 15 patients with congenital aortic valve disease. Although the patients had aortic valve disease, all measurements were made on the pulmonary valve. Systolic (QSYS) and diastolic (QDIAS) blood flow volume and cardiac index (CI) were determined at four pulmonary artery locations. The change in diastolic flow volume relative to slice 1, closest to the pulmonary valve, was also calculated. For a change in axial position of 1.5 cm, i.e. from 0.5 to 2 cm from the annulus, there was a change in diastolic flow volume of 4.4 ml. There was a significant increase in the mean diastolic flow from 3.4 to 7.7 ml (p = 0.01) between slice positions 0.5 and 2 cm. However, there was no significant change in CI, 3.4–3.7 l/min/m2 (p = 0.14) over the same distance. We believe that two factors are responsible for these results. The first is that of compliance, whose effects can be minimized by placing the MR slice close to the valve, however, this will not account for the second factor, being that of valve motion, and hence diastolic pulmonary valve flow or regurgitant volume will be underestimated. The degree of underestimation may only be important at mild and moderate levels of regurgitation or if changes in regurgitation are to be temporally measured.