A potential risk of overestimating apparent diffusion coefficient in parotid glands

Objectives: To investigate transient signal loss on diffusion weighted images (DWI) and overestimation of apparent diffusion coefficient (ADC) in parotid glands using single shot echoplanar DWI (EPDWI). Materials and Methods: This study enrolled 6 healthy subjects and 7 patients receiving radiotherapy. All participants received dynamic EPDWI with a total of 8 repetitions. Imaging quality of DWI was evaluated. Probability of severe overestimation of ADC (soADC), defined by an ADC ratio more than 1.2, was calculated. Error on T2WI, DWI, and ADC was computed. Statistical analysis included paired Student t testing and Mann-Whitney U test. A P value less than 0.05 was considered statistically significant. Results: Transient signal loss was visually detected on some excitations of DWI but not on T2WI or mean DWI. soADC occurred randomly among 8 excitations and 3 directions of diffusion encoding gradients. Probability of soADC was significantly higher in radiotherapy group (42.86%) than in healthy group (24.39%). The mean error percentage decreased as the number of excitations increased on all images, and, it was smallest on T2WI, followed by DWI and ADC in an increasing order. Conclusions: Transient signal loss on DWI was successfully detected by dynamic EPDWI. The signal loss on DWI and overestimation of ADC could be partially remedied by increasing the number of excitations. © 2015 Liu et al.published_or_final_versio

Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy

Background A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets. Methods Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis. Results A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001). Conclusion We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty

Population‐based cohort study of outcomes following cholecystectomy for benign gallbladder diseases

Background The aim was to describe the management of benign gallbladder disease and identify characteristics associated with all‐cause 30‐day readmissions and complications in a prospective population‐based cohort. Methods Data were collected on consecutive patients undergoing cholecystectomy in acute UK and Irish hospitals between 1 March and 1 May 2014. Potential explanatory variables influencing all‐cause 30‐day readmissions and complications were analysed by means of multilevel, multivariable logistic regression modelling using a two‐level hierarchical structure with patients (level 1) nested within hospitals (level 2). Results Data were collected on 8909 patients undergoing cholecystectomy from 167 hospitals. Some 1451 cholecystectomies (16·3 per cent) were performed as an emergency, 4165 (46·8 per cent) as elective operations, and 3293 patients (37·0 per cent) had had at least one previous emergency admission, but had surgery on a delayed basis. The readmission and complication rates at 30 days were 7·1 per cent (633 of 8909) and 10·8 per cent (962 of 8909) respectively. Both readmissions and complications were independently associated with increasing ASA fitness grade, duration of surgery, and increasing numbers of emergency admissions with gallbladder disease before cholecystectomy. No identifiable hospital characteristics were linked to readmissions and complications. Conclusion Readmissions and complications following cholecystectomy are common and associated with patient and disease characteristics

Joint reconstruction of high-SNR multiple b-values diffusion-weighted images using projection onto convex sets based multiplexed sensitivity-encoding (POCSMUSE)

Electronic Poster Session: Diffusion

Interleaved diffusion-weighted improved by adaptive partial-Fourier and multiband multiplexed sensitivity-encoding reconstruction

Purpose We report a series of techniques to reliably eliminate artifacts in interleaved echo-planar imaging (EPI) based diffusion-weighted imaging (DWI). Methods First, we integrate the previously reported multiplexed sensitivity encoding (MUSE) algorithm with a new adaptive Homodyne partial-Fourier reconstruction algorithm, so that images reconstructed from interleaved partial-Fourier DWI data are free from artifacts even in the presence of either (a) motion-induced k-space energy peak displacement, or (b) susceptibility field gradient induced fast phase changes. Second, we generalize the previously reported single-band MUSE framework to multiband MUSE, so that both through-plane and in-plane aliasing artifacts in multiband multishot interleaved DWI data can be effectively eliminated. Results The new adaptive Homodyne-MUSE reconstruction algorithm reliably produces high-quality and high-resolution DWI, eliminating residual artifacts in images reconstructed with previously reported methods. Furthermore, the generalized MUSE algorithm is compatible with multiband and high-throughput DWI. Conclusion The integration of the multiband and adaptive Homodyne-MUSE algorithms significantly improves the spatial-resolution, image quality, and scan throughput of interleaved DWI. We expect that the reported reconstruction framework will play an important role in enabling high-resolution DWI for both neuroscience research and clinical uses. Magn Reson Med 73:1872-1884, 2015. © 2014 Wiley Periodicals, Inc

Reconstruction of under-sampled Propeller gradient-echo image using projection onto convex sets based multiplexed sensitivity-encoding (POCSMUSE)

Electronic Poster Session: Acquisition, Reconstruction & Analysis 2 - Motion Correction: no. 4248The Propeller technique is a useful acquisition scheme and reconstruction method to reduce motion artifact. However, the higher specific absorption rate (SAR) of RF pulse at high-field magnetic strength can limit the number of multiple slices for a given TR, which in turn reduces the efficiency of acquisition, especially for Propeller-FSE sequence. A possible solution is to reduce the echo-train-length with under-sampling of data of each blade. In this study, we propose to apply POCSMUSE instead of SENSE reconstruction and Propeller reconstruction, to reconstruct the image from all under-sampled blade data with reduced noise amplification. The data acquired from brain and liver using Propeller-GRE will be used to test purposed POCSMUSE algorithm

3D Multi-Band, Multi-Slab, and Multi-Shot High-Resolution Diffusion MRI

When diffusion MRI data is acquired with 3D multi-slab and/or multi-shot imaging techniques, scan times are often lengthy and phase variations between the acquired shots and/or slice-encoding planes of 3D slabs introduce severe motion artifacts in slice images. To accelerate the acquisition of high spatial resolution diffusion MRI volumes with high SNR and fidelity, we outline a 3D image reconstruction model that simultaneously accounts for both in-plane and through-plane motion artifacts in 3D multi-band, multi-slab and multi-shot diffusion data. Diffusion data acquired and reconstructed in this fashion can be acquired at sub-millimeter spatial resolution with high SNR in ~1-2min

Ultrafast T2 mapping using echo-split GRASE acquisition and parametric POCSMUSE reconstruction

Our novel ultrafast T2 mapping framework, which uniquely integrates echo-split GRASE acquisition and parametric POCSMUSE reconstruction, has the following major advantages. First, parametric T2 map and high-quality multi-contrast images can be derived from a single set of single-shot GRASE data, with inherently low susceptibility to motion artifacts. Second, contamination of stimulated and other high order echoes is minimized in the echo-split GRASE scans. Third, T2 relaxation times can be accurately measured by the parametric POCSMUSE algorithm, which incorporates multiplexed parallel MR reconstruction and multi-echo-pathway signal modeling into a unified procedure