Improved geometric accuracy of whole body diffusion-weighted imaging at 1.5T and 3T using reverse polarity gradients

Whole body diffusion-weighted imaging (WB-DWI) is increasingly used in oncological applications, but suffers from misalignments due to susceptibility-induced geometric distortion. As such, DWI and structural images acquired in the same scan session are not geometrically aligned, leading to difficulties in e.g. lesion detection and segmentation. In this work we assess the performance of the reverse polarity gradient (RPG) method for correction of WB-DWI geometric distortion. Multi-station DWI and structural magnetic resonance imaging (MRI) data of healthy controls were acquired at 1.5T (n = 20) and 3T (n = 20). DWI data was distortion corrected using the RPG method based on b = 0 s/mm² (b0) and b = 50 s/mm² (b50) DWI acquisitions. Mutual information  (MI) between low b-value DWI and structural data increased with distortion correction (P < 0.05), while improvements in region of interest (ROI) based similarity metrics, comparing the position of incidental findings on DWI and structural data, were location dependent. Small numerical differences between non-corrected and distortion corrected apparent diffusion coefficient (ADC) values were measured. Visually, the distortion correction improved spine alignment at station borders, but introduced registration-based artefacts mainly for the spleen and kidneys. Overall, the RPG distortion correction gave an improved geometric accuracy for WB-DWI data acquired at 1.5T and 3T. The b0- and b50-based distortion corrections had a very similar performance.

Validation of automated whole-body analysis of metabolic and morphological parameters from an integrated FDG-PET/MRI acquisition

Automated quantification of tissue morphology and tracer uptake in PET/MR images could streamline the analysis compared to traditional manual methods. To validate a single atlas image segmentation approach for automated assessment of tissue volume, fat content (FF) and glucose uptake (GU) from whole-body [18F]FDG-PET/MR images. Twelve subjects underwent whole-body [18F]FDG-PET/MRI during hyperinsulinemic-euglycemic clamp. Automated analysis of tissue volumes, FF and GU were achieved using image registration to a single atlas image with reference segmentations of 18 volume of interests (VOIs). Manual segmentations by an experienced radiologist were used as reference. Quantification accuracy was assessed with Dice scores, group comparisons and correlations. VOI Dice scores ranged from 0.93 to 0.32. Muscles, brain, VAT and liver showed the highest scores. Pancreas, large and small intestines demonstrated lower segmentation accuracy and poor correlations. Estimated tissue volumes differed significantly in 8 cases. Tissue FFs were often slightly but significantly overestimated. Satisfactory agreements were observed in most tissue GUs. Automated tissue identification and characterization using a single atlas segmentation performs well compared to manual segmentation in most tissues and will be valuable in future studies. In certain tissues, alternative quantification methods or improvements to the current approach is needed.

Outcomes of epidural morphine treatment in cancer pain: nine years of clinical experience

The outcome of epidural morphine therapy is described in 146 consecutive cancer patients who were treated by a community hospital-based pain service. The routine procedure used a standard epidural catheter that was tunneled subcutaneously. One hundred and twenty-one patients improved and stayed on lifelong or chronic epidural opioids. Mean treatment time was 92 days (median, 47; range, 2-2040); 49% of the time was spent as outpatients. Twenty-five patients failed to respond to the treatment. The oral daily morphine-equivalent dose prior to inclusion was 164 mg. The mean daily epidural start dose of morphine was 18 mg (range, 6-120), and the mean daily dose at termination was 69 mg (range, 2-540). The dose escalations, described as the ratio of the maximum dose to the minimum maintenance start dose, were moderate, with a mean of 4.1 (median, 2.5), which corresponded to a percent increase of 5.1 (median, 2.7) per patient per day. Lack of effect due to the character of the original symptoms or progression of pain was the main reason for withdrawal from epidural opioid therapy (N = 27), followed by catheter-related problems (N = 9) and drug-related complications (N = 5). Also due to drug-related complications, epidural morphine therapy was changed to buprenorphine or methadone in 19 patients. Adjuvant systemic opioids were given to ten patients and epidural local anesthetics were administered to 17 of the subjects. Neuropathic pain, certain visceral pain types, incident pain on movement, and pain from cutaneous ulcerations were characteristics of poor responders.(ABSTRACT TRUNCATED AT 250 WORDS)