Inversion recovery ultrashort echo time imaging of ultrashort T2 tissue components in ovine brain at 3 T: a sequential D2O exchange study

Inversion recovery ultrashort echo time (IR‐UTE) imaging holds the potential to directly characterize MR signals from ultrashort T₂ tissue components (STCs), such as collagen in cartilage and myelin in brain. The application of IR‐UTE for myelin imaging has been challenging because of the high water content in brain and the possibility that the ultrashort T₂* signals are contaminated by water protons, including those associated with myelin sheaths. This study investigated such a possibility in an ovine brain D₂O exchange model and explored the potential of IR‐UTE imaging for the quantification of ultrashort T₂* signals in both white and gray matter at 3 T. Six specimens were examined before and after sequential immersion in 99.9% D₂O. Long T₂ MR signals were measured using a clinical proton density‐weighted fast spin echo (PD‐FSE) sequence. IR‐UTE images were first acquired with different inversion times to determine the optimal inversion time to null the long T₂ signals (TI_null). Then, at this TI_null, images with echo times (TEs) of 0.01–4 ms were acquired to measure the T₂* values of STCs. The PD‐FSE signal dropped to near zero after 24 h of immersion in D₂O. A wide range of TI_null values were used at different time points (240–330 ms for white matter and 320–350 ms for gray matter at TR = 1000 ms) because the T₁ values of the long T₂ tissue components changed significantly. The T₂* values of STCs were 200–300 μs in both white and gray matter (comparable with the values obtained from myelin powder and its mixture with D₂O or H₂O), and showed minimal changes after sequential immersion. The ultrashort T₂* signals seen on IR‐UTE images are unlikely to be from water protons as they are exchangeable with deuterons in D₂O. The source is more likely to be myelin itself in white matter, and might also be associated with other membranous structures in gray matter.     

The synovial fold of the distal tibiofibular joint: A morphometric study

Impingement of the synovial fold of the distal tibiofibular joint (DTFJ) may contribute to the development of chronic ankle pain and disability after ankle inversion sprain. The morphology of the synovial fold of the DTFJ and recess is poorly understood. The purpose of this study was to describe and quantify the synovial fold and recess of the DTFJ. Thirty‐three pairs of adult embalmed ankle joints were dissected and the presence, disposition, morphology, and dimensions of the synovial fold were determined in relation to the DTFJ and its recess. A synovial fold was present in all specimens examined and extended from the deep posterior tibiofibular ligament along the DTFJ line an average of 15.31 mm [standard deviation (SD), 4.42 mm]. The majority of synovial folds were elongated in shape with smooth borders and occupied more than two thirds of the DTFJ line. In 70% of ankles examined, the synovial folds were found to extend a mean of 20.05 mm (SD, 7.01 mm) from the DTFJ line into the recess where they were loosely attached to the fibular wall. In the remaining ankles, the synovial fold was limited to the DTFJ line leaving the recess devoid of a synovial fold. Intra‐observer and inter‐observer reliability of measurements was good to excellent (intra‐class correlation coefficient, 0.61–0.99). An understanding of the morphology of the DTFJ synovial fold might help to explain ongoing ankle pain after injury, and why arthroscopic removal of the tissue might be therapeutic. Clin. Anat. 26:630–637, 2013. © 2012 Wiley Periodicals, Inc.     

Practical considerations for the application of ear simulators in the calibration of audiometers in the extended high frequency region

Objective: Calibration service providers for audiometric equipment often encounter impracticalities in fully implementing the International Electrotechnical Commission (IEC) guidelines for the extended high frequency region. This report evaluates some of the work-around solutions sometimes employed in practice and the implications these have for audiometer calibration results and uncertainties. Design: The impact of using four different microphone configurations on the ear simulator calibration in the frequency range 125?Hz to 20?kHz, and especially in the extended high frequency range from 10?kHz to 20?kHz, was investigated, at a range of temperatures. Results: Variations in the response of the ear simulator of up to 6?dB were observed with the different microphone configurations. In addition, using the microphone without its protection grid produced a dip in the high frequency response of approximately 15?dB. Conclusion: While deviation from the practices required in IEC standards is not recommended, replacing the microphone protection grid with a specially fabricated collar (essentially a grid with the top removed) was found to constrain deviations in response to within ±2?dB. It was also concluded that simply removing the microphone protection grid resulted in a wholly unsatisfactory performance.     

Genicular Artery Embolization for the Treatment of Knee Pain Secondary to Osteoarthritis

PurposeTo evaluate the efficacy and safety of embolization of hyperemic synovial tissue for the treatment of knee pain secondary to osteoarthritis (OA).Materials and MethodsTwenty patients with radiographic knee OA and moderate-to-severe pain refractory to conservative therapy were enrolled in a prospective, 2-site pilot study. Genicular artery embolization (GAE) was performed with 75- or 100-μm spherical particles. Patients were assessed with magnetic resonance imaging at baseline and at 1 month and with the Visual Analogue Scale (VAS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at baseline and at 1, 3, and 6 months. Adverse events were recorded at all timepoints.ResultsEmbolization of at least 1 genicular artery was achieved in 20/20 (100%) patients. Mean VAS improved from 76 mm ± 14 at baseline to 29 mm ± 27 at 6-month follow-up (P < .01). Mean WOMAC score improved from 61 ± 12 at baseline to 29 ± 27 at 6-month follow-up (P < .01). Self-limiting skin discoloration occurred in 13/20 (65%) patients. Two of 20 (10%) patients developed plantar sensory paresthesia that resolved within 14 days.ConclusionsGAE to treat knee pain secondary to OA can be performed safely and demonstrates potential efficacy. Further randomized comparative studies are needed to determine true treatment effect versus placebo effect.     

Do regions of interest location and type influence liver stiffness measurement using magnetic resonance elastography?

PurposeTo assess the variability of liver stiffness measurements using magnetic resonance elastography (MRE) at 1.5 T, depending on different approaches of regions of interest (ROIs) drawing.Material and methodsFifty consecutive patients with successful liver MRE were included. There were 32 men and 18 women with a mean age of 52 ± 14 (SD) years (range: 20–85 years). MRE was acquired using a gradient recalled-echo MRE sequence. At the level of the portal bifurcation, one observer drawn in the right liver first 3 elliptical ROI and then one free-hand ROI, as large as possible based on the confidence map and the anatomy. Three additional elliptical ROIs were further drawn on the slice above and 3 other on the slice below, for a total of 9 elliptical ROIs. The average value of liver stiffness in the 3 elliptical ROIs of the central slice and the one from the 9 elliptical ROIs were computed. Three liver stiffness values were obtained for each patient from the 3 measurement methods (one free-hand ROI, 3 elliptical ROIs and 9 elliptical ROIs). Inter-method variability was assessed using the intra-class correlation coefficient (ICC) and Bland-Altman analysis.ResultsThe variability between the 3 methods was excellent with ICC > 0.978 (P < 0.0001). The Bland-Altman analysis revealed high agreement between the 3 methods with bias < 0.45 kPa and limits of agreement < ±1.13 kPa. The variability was lower when comparing a large free-hand ROI and the 3-elliptical ROIs, than when comparing the 9-elliptical ROIs to one of the other methods.ConclusionOur results show that the variability between the 3 methods of ROI drawing and placement is very low.     

Re-examination of the potential step chronoamperometry method through numerical inversion of Laplace transforms. II. Application examples

In the first part of this work, we proposed the so-called GS-, FE- and FT-PSCA algorithms to investigate a wide range of electrode geometry and chemical, electrochemical and one-dimensional mass-transport processes by the potential-step chronoamperometry (PSCA) method. Each algorithm provides a full explicit formulation of Faradaic current with respect to time, applied potential and electrochemical parameters (initial concentrations, geometrical parameter(s), standard potential, electrochemical and chemical rate constants and diffusion coefficients). Application examples relative to diffusion equations with spherical electrode geometry are presented in this second article by way of illustration of the potentialities of GS- and FT-PSCA algorithms. First, the case of one-step electrochemical reactions at spherical and hemispherical electrodes of any radius is investigated when both implicated species are soluble in the electrolytic solution. The numerical solution obtained from GS-PSCA algorithm is favourably compared to previous results in the electrochemical literature. Next, we use the FT-PSCA algorithm for investigating spherical diffusion with amalgamation reaction. Finally, the characteristic features of chronoamperograms and sampled-current voltammograms pertaining to the above reaction are examined and discussed.     

Analysis of K-<Emphasis Type="Italic">ras</Emphasis> Codon 12 Mutation in Flat and Nodular Variants of Serrated Adenoma in the Colon

PURPOSE: The developmental process of serrated adenomas is obscure, and the importance of genetic alterations has not been elucidated clearly. The possibility that the developmental process and genetic alterations of serrated adenomas could differ from those of ordinary tubular adenomas was explored in this work. METHODS: Serrated adenomas were obtained by endoscopic resection (n = 57) and divided into two groups: flat (n = 10) and nodular (n = 47). Mutation of the K-ras gene was analyzed by enriched polymerase chain reaction–enzyme-linked mini-sequence assay, which can detect not only the presence of a mutation but also the mutation type of K-ras codon 12 with high sensitivity. Methylation-specific polymerase chain reaction was performed with specific primers for the DNA repair gene O6-methylguanine-DNA methyltransferase. RESULTS: Serrated adenomas located in the rectum were more likely to have a K-ras mutation (9/12, 75 percent), whereas serrated adenomas of the flat type were less likely to have one (1/10, 10 percent). Furthermore, nodular serrated adenomas that occurred in the rectum possessed a high frequency of K-ras gene codon 12 point mutation (8/10, 80 percent) despite an overall frequency of 46.8 percent (22/47). A mutation of the K-ras codon 12 gene was detected in 23 (40.4 percent) of 57 serrated adenomas. Three types of point mutations of codon 12 were detected, with the mutation of GAT being observed most frequently. CONCLUSIONS: This study shows that development of nodular serrated adenomas may depend on the mutation of the K-ras codon 12 gene, whereas development of flat serrated adenomas may not. Additionally, serrated adenomas that occur in the rectum are closely related to the mutation of the K-ras codon 12 gene. K-ras mutations in serrated adenomas may be unaffected by the epigenetic silencing of O6-methylguanine-DNA methyltransferase by promoter hypermethylation.