Abstract
Background: MR-guided focused ultrasound (MRgFUS) offers the possibility of safe and accurate lesioning inside the brain. Until now, most MRgFUS thermal applications have been based on temperature or energy protocols. Experimental studies support however an approach centered on thermal dose control.Objective: To show the technical feasibility and lesion size predictability of a thermal dose approach during MRgFUS pallidothalamic tractotomy (PTT) against chronic therapy-resistant Parkinson's disease (PD).Methods: MR and thermal dose data were analyzed in 31 MRgFUS interventions between January and December 2017 in patients suffering from chronic therapy-resistant Parkinson's disease (PD) using a standardized PTT target covered by 5 to 7 target lesion sub-units.Results: Good correlations were found between (1) the mean axial T2 lesion diameter intraoperatively and the mean 240 cumulative equivalent min at 43°C (240 CEM) thermal dose diameter (r = 0.52), (2) the mean axial T2 diameter 48 h post-treatment and the mean 18 CEM thermal dose diameter (r = 0.62), and (3) the mean axial T2 diameter intraoperatively and 48 h post-treatment (r = 0.62).Conclusion: Our current approach using a thermal dose steering for multiple target lesion sub-units could be reproduced in 31 interventions with a good lesion size predictability.
Highlights
Our previous experience of lesioning the pallidothalamic tract on its way to the thalamus in Parkinson’s disease (PD) [1] has led us, after analysis of recurrences or partial symptom control, to develop a targeting protocol aiming at improved spatial lesion coverage of the target
Each sonication had the shortest possible duration and the corresponding power in order to provide a thermal dose of 240 cumulative equivalent min at 43◦C (CEM) at each focal point
Targeted thresholds of 18 and 240 cumulative equivalent min at 43◦C (240 CEM) are based on experimental data in the rabbit and primate brain summarized by MacDannold and co-workers [3, 4]
Summary
Our previous experience of lesioning the pallidothalamic tract on its way to the thalamus in PD [1] has led us, after analysis of recurrences or partial symptom control, to develop a targeting protocol aiming at improved spatial lesion coverage of the target. Our current approach, served by a histological reappraisal of the pallidothalamic tract, adopts the strategy of applying a set of small thermolesions with shortest possible sonication durations, under thermal dose control and moving the focal point of the MRgFUS system onto preplanned coordinates [2]. This is a study of thermal dose and imaging correlations aiming to show the technical feasibility and lesion size predictability applying a thermal dose approach, and to compare it with currently used approaches. Experimental studies support an approach centered on thermal dose control
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