Cranial MRgFUS intraprocedural diffusion and T2 imaging and comparison with postablation lesion size and location.

OBJECTIVE: The ability to predict final lesion characteristics during magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy for the treatment of essential tremor remains technically challenging, yet it is essential in order to avoid off-target ablation and to ensure adequate treatment. The authors sought to evaluate the technical feasibility and utility of intraprocedural diffusion-weighted imaging (DWI) in the prediction of final lesion size and location. METHODS: Lesion diameter and distance from the midline were measured on both intraprocedural and immediate postprocedural diffusion and T2-weighted sequences. Bland-Altman analysis was utilized to determine differences in measurement between intraprocedural and immediate postprocedural images with both sequences. RESULTS: Lesion size increased on both the postprocedural diffusion and T2-weighted sequences, although the difference was smaller on the T2-weighted sequence. There was only a small difference in intraprocedural and postprocedural lesion distance from the midline on both the diffusion and T2-weighted sequences. CONCLUSIONS: Intraprocedural DWI is both feasible and useful with regard to predicting final lesion size and providing an early indication of lesion location. Further research should determine the value of intraprocedural DWI in predicting delayed clinical outcomes.

Imaging Glioblastoma Posttreatment: Progression, Pseudoprogression, Pseudoresponse, Radiation Necrosis.

Radiographic monitoring of posttreatment glioblastoma is important for clinical trials and determining next steps in management. Evaluation for tumor progression is confounded by the presence of treatment-related radiographic changes, making a definitive determination less straight-forward. The purpose of this article was to describe imaging tools available for assessing treatment response in glioblastoma, as well as to highlight the definitions, pathophysiology, and imaging features typical of true progression, pseudoprogression, pseudoresponse, and radiation necrosis.

Improved targeting of the globus pallidus interna using quantitative susceptibility mapping prior to MR-guided focused ultrasound ablation in Parkinson's disease.

PURPOSE: Magnetic resonance guided focused ultrasound (MRgFUS) of the globus pallidus interna (GPi) has shown promise in the treatment of drug-resistant Parkinson's disease, though direct visualization of the GPi remains challenging with MRI. The purpose of this study was to compare various preoperative MR imaging techniques and to evaluate the utility of quantitative susceptibility imaging (QSM) in the depiction of the GPi prior to MRgFUS ablation. MATERIALS AND METHODS: Six patients with medication refractory advanced idiopathic Parkinson's disease were referred for preoperative MR imaging prior to MRgFUS pallidotomy. Axial T1WI and T2WI, Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR), and QSM sequences were acquired. DTI tractography was performed to delineate the corticospinal tracts. Qualitative visualization scores and contrast to noise ratios (CNR) were recorded and measured on all images. RESULTS: QSM had significantly higher median qualitative visualization scores (3.00) compared with the T1WI (1.00), T2WI (1.50), and FGATIR sequences (1.50) (p < 0.05). QSM provided superior CNR for GPi depiction in each category (GPi-GPe and GPi-IC), respectively. For GPi-GPe, median CNR for T1WI, T2WI, FGATIR, and QSM was 1.13, 1.68, 0.79, and 10.78. For GPi-IC, median CNR for T1WI, T2WI, FGATIR, and QSM was 1.48, 4.63, 4.24, and 40.26, respectively (p < 0.05). CONCLUSION: QSM offers improved visualization of the GPi compared with the traditional and currently recommended MR sequences prior to MRgFUS ablation in patients with Parkinson's disease. These results suggest that QSM should be considered as part of all preoperative imaging protocols prior to MRgFUS pallidotomy.

Imaging Glioblastoma Posttreatment: Progression, Pseudoprogression, Pseudoresponse, Radiation Necrosis.

Radiographic monitoring of posttreatment glioblastoma is important for clinical trials and determining next steps in management. Evaluation for tumor progression is confounded by the presence of treatment-related radiographic changes, making a definitive determination less straight-forward. The purpose of this article was to describe imaging tools available for assessing treatment response in glioblastoma, as well as to highlight the definitions, pathophysiology, and imaging features typical of true progression, pseudoprogression, pseudoresponse, and radiation necrosis.