Comparative evaluation of tractography-based direct targeting and atlas-based indirect targeting of the ventral intermediate (Vim) nucleus in MRgFUS thalamotomy.

To analyze and compare direct and indirect targeting of the Vim for MRgFUS thalamotomy. We retrospectively evaluated 21 patients who underwent unilateral MRgFUS Vim ablation and required targeting repositioning during the procedures. For each patient, in the three spatial coordinates, we recorded: (i) indirect coordinates; (ii) the coordinates where we clinically observed tremor reduction during the verification stage sonications; (iii) direct coordinates, measured on the dentatorubrothalamic tract (DRTT) at the after postprocessing of DTI data. The agreement between direct and indirect coordinates compared to clinically effective coordinates was evaluated through the Bland-Altman test and intraclass correlation coefficient. The median absolute percentage error was also calculated. Compared to indirect targeting, direct targeting showed inferior error values on the RL and AP coordinates (0.019 vs. 0.079 and 0.207 vs. 0.221, respectively) and higher error values on the SI coordinates (0.263 vs. 0.021). The agreement between measurements was higher for tractography along the AP and SI planes and lower along the RL planes. Indirect atlas-based targeting represents a valid approach for MRgFUS thalamotomy. The direct tractography approach is a valuable aid in assessing the possible deviation of the error in cases where no immediate clinical response is achieved.

Visible T1-hyperintensity of the dentate nucleus after multiple administrations of macrocyclic gadolinium-based contrast agents: yes or no?

OBJECTIVES: To investigate the appearance of visible dentate nucleus (DN) T1-hyperintensity and quantify changes in DN/pons (DN/P) signal intensity (SI) ratio in MS patients after the exclusive administration of macrocyclic GBCAs. MATERIALS AND METHODS: One hundred forty-nine patients with confirmed MS were evaluated. Patients received at least two administrations of gadobutrol (n = 63), gadoterate (n = 57), or both (n = 29). Two experienced neuroradiologists in consensus evaluated unenhanced T1-weighted MR images from all examinations in each patient for evidence of visible DN hyperintensity. Thereafter, SI measurements were made in the left and right DN and pons on unenhanced T1-weighted images from the first and last scans. A two-sample t test compared the DN/P SI ratios for patients with and without visible T1-hyperintensity. RESULTS: Visible T1-hyperintensity was observed in 42/149 (28.2%) patients (19 after gadobutrol only, 15 after gadoterate only, 8 after both), typically at the 4th or 5th follow-up exam at 3-4 years after the initial examination. Significant increases in DN/P SI ratio from first to last examination were determined for patients with visible T1-hyperintensity (0.998 ± 0.002 to 1.153 ± 0.016, p < 0.0001 for gadobutrol; 1.003 ± 0.004 to 1.110 ± 0.014, p < 0.0001 for gadoterate; 1.004 ± 0.011 to 1.163 ± 0.032, p = 0.0004 for both) but not for patients without visible T1-hyperintensity (p > 0.05; all groups). CONCLUSION: Multiple injections of gadobutrol and/or gadoterate can lead to visible and quantifiable increases in DN/P SI ratio in some patients with MS.

Dynamic MRI in the evaluation of the spine: state of the art.

INTRODUCTION: Degenerative disease of the spine is a generic term encompassing a wide range of different disease processes, which leads to spinal instability; traumatic/neoplastic events can accelerate this aging process. Therefore, the dynamic nature of the spine and its mobility across multiple segments is difficult to depict with any single imaging modality. METHODS: A review of PubMed databases for articles published about kMRI in patients with cervical and lumbar spinal desease was performed. We focused on the physiopathological changes in the transition from supine to upright position in spine instability. DISCUSSION: Until a few years ago, X-ray was the only imaging modality for the spine in the upright position. Of the imaging techniques currently available, MRI provides the greatest range of information and the most accurate delineation of soft-tissue and osseous structures. Conventional MRI examinations of the spine usually are performed in supine position, in functional rest, but the lumbar spine instability is often shown only by upright standing. This can result in negative findings, even in the presence of symptoms. Regardless, the final result is distorted. To overcome this limitation, Kinetic MRI (kMRI) can image patients in a weight-bearing position and in flexed and extended positions, thus revealing abnormalities that are missed by traditional MRI studies. CONCLUSION: Despite some limitations, the upright MRI can be a complementary investigation to the traditional methods when there are negative results in conventional MRI in symptomatic patients or when surgical therapy is scheduled.

Is size an essential criterion to define tumefactive plaque? MR features and clinical correlation in multiple sclerosis.

Tumefactive multiple sclerosis is an inflammatory demyelinating disease of the central nervous system. It has recently been described as a rare subtype of multiple sclerosis (MS) characterised by the appearance of solitary or multiple space-occupying lesions associated with imaging characteristics mimicking neoplasm. Atypical features include plaque size >2 cm with mass effect, oedema, and/or ring enhancement on magnetic resonance (MR) images.This study is a retrospective review designed to evaluate the prevalence of tumefactive plaques in a selected population of 440 MS patients referred to our MS centre in Southern Italy between 2005 and 2014. We analysed the radiographic features of lesions ranging in size from 0.5 to 2 cm to establish whether smaller plaques with MR characteristics similar to tumefactive plaques present different symptoms, disease evolution and prognosis. We also aimed to ascertain if MR features suggestive of biological aggressiveness could be useful prognostic criteria for a correct diagnosis of the disease and subsequent treatment. Our data suggest that lesions 0.5-2 cm and >2 cm have similar MR features and clinical evolution.