Purpose Heating of gradient coils and passive shim components is a common cause of instability in the B 0 field, especially when gradient intensive sequences are used. The aim of the study was to set a benchmark for typical drift encountered during MR spectroscopy (MRS) to assess the need for real-time field-frequency locking on MRI scanners by comparing field drift data from a large number of sites. Method A standardized protocol was developed for 80 participating sites using 99 3T MR scanners from 3 major vendors. Phantom water signals were acquired before and after an EPI sequence. The protocol consisted of: minimal preparatory imaging; a short pre-fMRI PRESS; a ten-minute fMRI acquisition; and a long post-fMRI PRESS acquisition. Both pre- and post-fMRI PRESS were non-water suppressed. Real-time frequency stabilization/adjustment was switched off when appropriate. Sixty scanners repeated the protocol for a second dataset. In addition, a three-hour post-fMRI MRS acquisition was performed at one site to observe change of gradient temperature and drift rate. Spectral analysis was performed using MATLAB. Frequency drift in pre-fMRI PRESS data were compared with the first 5:20 minutes and the full 30:00 minutes of data after fMRI. Median (interquartile range) drifts were measured and showed in violin plot. Paired t-tests were performed to compare frequency drift pre- and post-fMRI. A simulated in vivo spectrum was generated using FID-A to visualize the effect of the observed frequency drifts. The simulated spectrum was convolved with the frequency trace for the most extreme cases. Impacts of frequency drifts on NAA and GABA were also simulated as a function of linear drift. Data from the repeated protocol were compared with the corresponding first dataset using Pearson's and intraclass correlation coefficients (ICC). Results Of the data collected from 99 scanners, 4 were excluded due to various reasons. Thus, data from 95 scanners were ultimately analyzed. For the first 5:20 min (64 transients), median (interquartile range) drift was 0.44 (1.29) Hz before fMRI and 0.83 (1.29) Hz after. This increased to 3.15 (4.02) Hz for the full 30 min (360 transients) run. Average drift rates were 0.29 Hz/min before fMRI and 0.43 Hz/min after. Paired t-tests indicated that drift increased after fMRI, as expected (p < 0.05). Simulated spectra convolved with the frequency drift showed that the intensity of the NAA singlet was reduced by up to 26%, 44 % and 18% for GE, Philips and Siemens scanners after fMRI, respectively. ICCs indicated good agreement between datasets acquired on separate days. The single site long acquisition showed drift rate was reduced to 0.03 Hz/min approximately three hours after fMRI. Discussion This study analyzed frequency drift data from 95 3T MRI scanners. Median levels of drift were relatively low (5-min average under 1 Hz), but the most extreme cases suffered from higher ...

Background and PurposeSurgery is an alternative treatment of drug-resistant epilepsy. Positive attitude of medical personnel towards epilepsy surgery is essential. This study assessed general knowledge of and attitude towards epilepsy surgery among medical students. The aim of this study was to assess general knowledge of and attitude towards epilepsy surgery among medical students.MethodsQuestionnaire was distributed to medical students. Questionnaire consisted of two questions of general knowledge of drug-resistant epilepsy, questions of students’ attitude towards epilepsy surgery and questions of referral of patients. The Chi-square test was utilized.ResultsThe terms “drug-resistant epilepsy” and “mesial temporal sclerosis” were known in 72.3 and 14.2 percent, respectively. Awareness and support of epilepsy surgery were recorded in 74.5 and 48.9 percent, respectively. A drug resistant patient would have been referred to a qualified centre in 19.4 percent. General knowledge and awareness of epilepsy surgery were better in higher levels of study (p < 0.001).ConclusionsMedical students have a positive attitude towards epilepsy surgery. Students are aware of drug resistance in epilepsy. Knowledge and awareness are better among students in higher levels, after neurology is introduced to the curriculum. We conclude that highlighting the importance of epilepsy surgery should be continued. Moreover, additional educational effort should be invested in expressing the importance of efficient referral of a patient to a qualified centre.

In Parkinson’s disease (PD), there is a reduction of neuromelanin (NM) in the substantia nigra (SN). Manual quantification of the NM volume in the SN is unpractical and time-consuming; therefore, we aimed to quantify NM in the SN with a novel semi-automatic segmentation method. Twenty patients with PD and twelve healthy subjects (HC) were included in this study. T1-weighted spectral pre-saturation with inversion recovery (SPIR) images were acquired on a 3T scanner. Manual and semi-automatic atlas-free local statistics signature-based segmentations measured the surface and volume of SN, respectively. Midbrain volume (MV) was calculated to normalize the data. Receiver operating characteristic (ROC) analysis was performed to determine the sensitivity and specificity of both methods. PD patients had significantly lower SN mean surface (37.7 ± 8.0 vs. 56.9 ± 6.6 mm2) and volume (235.1 ± 45.4 vs. 382.9 ± 100.5 mm3) than HC. After normalization with MV, the difference remained significant. For surface, sensitivity and specificity were 91.7 and 95 percent, respectively. For volume, sensitivity and specificity were 91.7 and 90 percent, respectively. Manual and semi-automatic segmentation methods of the SN reliably distinguished between PD patients and HC. ROC analysis shows the high sensitivity and specificity of both methods.

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INTRODUCTION: Liver cirrhosis (LC) is a worldwide public health problemthat represents an important cause of death in adults. One of the complications of LC is hepatic encephalopathy (HE). HE is sometimes challenging to detect as it can present as subtle cognitive impairment. Alterations of gamma-aminobutyric acid (GABA) levels in various brain regions were demonstrated in HE (1–3), however, changes of GABA levels in the striatum, a critical element of the motor, reward and executive systems, have not been yet reported. This pilot study focuses on the detection of GABA in the striata in LC patients with various degrees of cognitive impairment. METHODS: Six patients (2 females, mean age: 59.6 ± 8.4) with clinically diagnosed LC (all due to alcohol overconsumption) and seven (6 females, mean age: 53.9 ± 9.3) healthy subjects (HC) were included in this study. T1- and T2-weighted images were acquired to place two 35 × 25 × 25 mm voxels for MEGA-PRESS (4) MR spectroscopy in the left and right striatum. Data processing and quantitative analysis was performed in Gannet 3.0 (www.gabamrs.com). GABA levels were calculated with respect to the tissue water signal and corrected for tissue composition. Stroop test scores, psychometric hepatic encephalopathy score (PHES), Mini-Mental State Exam (MMSE) scores and venous blood ammonia levels were determined on the day of MR scanning. RESULTS: In left striatum, mean GABA levels were 3.5 ± 1.0 i.u. and 5.3 ± 0.8 i.u. in LC and HC group, respectively (P < 0.05). In right striatum, mean GABA levels were 4.8 ± 1.4 i.u. and 4.6 ± 0.81 i.u. in LC and HC group, respectively (P > 0.05). A negative correlation between the overall time needed for PHES completion and GABA levels in left striatum was demonstrated (r = -0.7, P < 0.05). No statistically significant correlations between response time of Stroop test, ammonia and GABA levels were noted for either voxel. MMSE did not significantly differ between groups. CONCLUSION: In this pilot study, decreased left striatal GABA levels were demonstrated in LC vs. HC group. This study was limited with number of enrolled subjects: continuation of this study and further stratification of patients in subgroups (accordingly to cognitive impairment) could potentially result in a model of predicting development of cognitive impairment in LC before presence of evident clinical signs.