“Alarm-corrected” ergonomic armrest use could improve learning curves of novices on robotic simulator

Surgical Endoscopy - In robotic surgery, the professional ergonomic habit of using an armrest reduces operator fatigue and increases the precision of motion. We designed and validated a pressure...     

Synthetic MRI is not yet ready for morphologic and functional assessment of patellar cartilage at 1.5 Tesla

PurposeThe purpose of this study was to compare morphologic assessment and relaxometry of patellar hyaline cartilage between conventional sequences (fast spin-echo [FSE] T2-weighted fat-saturated and T2-mapping) and synthetic T2 short-TI inversion recovery (STIR) and T2 maps at 1.5 T magnetic resonance imaging (MRI).MethodThe MRI examinations of the knee obtained at 1.5 T in 49 consecutive patients were retrospectively studied. There were 21 men and 28 women with a mean age of 45 ± 17.7 (SD) years (range: 18–88 years). Conventional and synthetic acquisitions were performed, including T2-weighted fat-saturated and T2-mapping sequences. Two radiologists independently compared patellar cartilage T2-relaxation time on conventional T2-mapping and synthetic T2-mapping images. A third radiologist evaluated the patellar cartilage morphology on conventional and synthetic T2-weighted images. The presence of artifacts was also assessed. Interobserver agreement for quantitative variables was assessed using intraclass correlation coefficient (ICC).ResultsIn vitro, conventional and synthetic T2 maps yielded similar mean T2 values 58.5 ± 2.3 (SD) ms and 58.8 ± 2.6 (SD) ms, respectively (P = 0.414) and 6% lower than the expected experimental values (P = 0.038). Synthetic images allowed for a 15% reduction in examination time compared to conventional images. On conventional sequences, patellar chondropathy was identified in 35 patients (35/49; 71%) with a mean chondropathy grade of 4.8 ± 4.8 (SD). On synthetic images, 28 patients (28/49; 57%) were diagnosed with patellar chondropathy, with a significant 14% difference (P = 0.009) and lower chondropathy scores (3.7 ± 4.9 [SD]) compared to conventional images. Motion artifacts were more frequently observed on synthetic images (18%) than on conventional ones (6%). The interobserver agreement was excellent for both conventional and synthetic T2 maps (ICC > 0.83). Mean cartilage T2 values were significantly greater on synthetic images (36.2 ± 3.8 [SD] ms; range: 29-46 ms) relative to conventional T2 maps (31.8 ± 4.1 [SD] ms; range: 26-49 ms) (P < 0.0001).ConclusionDespite a decrease in examination duration, synthetic images convey lower diagnostic performance for chondropathy, greater prevalence of motion artifacts, and an overestimation of T2 values compared to conventional MRI sequences.     

Influence of Calcium on Choline Measurements by 1H MR Spectroscopy of Thigh Muscles

Objective

To study the effects of calcium on the choline peak measurements with 1H MR spectroscopy.

Material and methods

The thigh muscles of two cadaveric specimens were prospectively evaluated on a 3 T MR unit before and after the injection of calcium carbonate (up to 0.4322 g). The choline peaks of 147 spectra from 10 different anatomic locations were quantitatively evaluated. The influence of the calcium concentration and its disposition with respect to the main magnetic field were considered. B₀ phase maps were used to evaluate field inhomogeneities.

Results

The presence of calcium led to a 43 % underestimation of the choline peak and the choline concentration (p?=?0.0002 and 0.0036). The mean choline concentrations before and after CaCO3 injection were 3.53?±?1.72 mmol/l and 1.58?±?0.63 mmol/l. The influence of calcium carbonate on the choline peak estimations was proportional to the calcium concentration. There was a significant position-dependent difference in the estimation of the choline peak amplitude (p?<?0.0154). Calcium injection led to a measurable increase in field inhomogeneities.

Conclusion

There was a significant underestimation of the choline peak amplitude and concentration in the presence of calcium, which might cause misinterpretations of MR spectra.

Key Points

? The presence of calcium led to significant underestimation of choline measurements. ? The influence of calcium is dependent on its concentration and distribution. ? Quantitative MR spectroscopy of calcified tumours should be interpreted with caution.     

In vivo characterization of the vestibulo-cochlear nerve motion by MRI

The motion of the vestibulo-cochlear nerve (VCN) was quantified at the level of the cerebello-pontine angle in 28 healthy volunteers enrolled in a prospective study performed on a 3 T MRI scanner. A phase contrast MRI (PCMRI) sequence was used. The VCN was divided into a cisternal part and a meatic part, both of which were measured for motion in the cranio-caudal (CC) and antero-posterior (AP) directions. Motion was cardiac-cycle-dependent in these two directions. The meatic VCN motion was delayed compared to the cisternal VCN motion. In the CC direction, the mean amplitude of the cisternal VCN motion was twice larger than the mean amplitude of the meatic VCN motion (0.37 +/− 0.14 mm versus 0.17 +/− 0.08 mm). In the AP direction, the mean amplitude of the cisternal VCN was 0.19 +/− 0.08 mm versus 0.16 +/− 0.14 mm for the meatic VCN. We used an “oscillating string” to explain the VCN motion. Reproducibility tests have shown small variations in measurements of the CC motion. PCMRI can be used to assess the VCN motion at the level of the cerebello-pontine angle.     

Correlation between tumor growth and hormonal therapy with MR signal characteristics of desmoid-type fibromatosis: A preliminary study

Purpose

To evaluate the impact of hormonal therapy on MRI characteristics of desmoid-type fibromatosis on T1-weighted, T2-weighted fat-saturated and post-contrast sequences.

Temporal epilepsy lesions may be detected by the voxel-based quantitative analysis of brain FDG-PET images using an original block-matching normalization software

Introduction

Statistical parametric mapping (SPM) provides useful voxel-by-voxel analyses of brain images from ¹⁸F-fluorodesoxyglucose positron emission tomography (FDG-PET) after an initial step of spatial normalization through an anatomical template model. In the setting of the preoperative workup of patients with temporal epilepsy, this study aimed at assessing a block-matching (BM) normalization method, where most transformations are computed through small blocks, a principle that minimizes artefacts and overcomes additional image-filtering.

Methods

Brain FDG-PET images from 31 patients with well-characterised temporal lobe epilepsy and among whom 22 had common mesial temporal lobe epilepsy were retrospectively analysed using both BM and conventional SPM normalization methods and with PET images from age-adjusted controls. Different threshold p values corrected for cluster volume were considered (0.01, 0.005, and 0.001).

Results

The use of BM provided equivalent values to those of SPM with regard to the overall volumes of temporal and extra-temporal hypometabolism, as well as similar sensitivity for detecting the involved temporal lobe, reaching 87 and 94 % for SPM and BM, respectively, at a threshold p value of 0.01. However, the ability to more accurately localize brain lesions within the mesial portion of the temporal lobe was a little higher with BM than with SPM with respective sensitivities reaching 78 % for BM and 45 % for SPM (p < 0.05).

Conclusions

BM normalization compares well with conventional SPM for the voxel-based quantitative analysis of the FDG-PET images from temporal epilepsy patients. Further studies in different population are needed to determine whether BM is truly an accurate alternative to SPM in this setting.

     

Magnetic Resonance Elastography for Assessing Fibrosis in Patients with Crohn’s Disease: A Pilot Study

Digestive Diseases and Sciences - Patients with Crohn’s disease can develop intestinal strictures, containing various degrees of inflammation and fibrosis. Differentiation of the main...