A magnetic resonance imaging, histological, and dose modeling comparison of focused ultrasound, radiofrequency, and Gamma Knife radiosurgery lesions in swine thalamus

Abstract

Object The purpose of this study was to use MRI and histology to compare stereotactic lesioning modalities in a large brain model of thalamotomy. Methods A unilateral thalamotomy was performed in piglets utilizing one of 3 stereotactic lesioning modalities: focused ultrasound (FUS), radiofrequency, and radiosurgery. Standard clinical lesioning parameters were used for each treatment; and clinical, MRI, and histological assessments were made at early (< 72 hours), subacute (1 week), and later (1–3 months) time intervals. Results Histological and MRI assessment showed similar development for FUS and radiofrequency lesions. T2-weighted MRI revealed 3 concentric lesional zones at 48 hours with resolution of perilesional edema by 1 week. Acute ischemic infarction with macrophage infiltration was most prominent at 72 hours, with subsequent resolution of the inflammatory reaction and coalescence of the necrotic zone. There was no apparent difference in ischemic penumbra or “sharpness” between FUS or radiofrequency lesions. The radiosurgery lesions presented differently, with latent effects, less circumscribed lesions at 3 months, and apparent histological changes seen in white matter beyond the thalamic target. Additionally, thermal and radiation lesioning gradients were compared with modeling by dose to examine the theoretical penumbra. Conclusions In swine thalamus, FUS and radiosurgery lesions evolve similarly as determined by MRI, histological examination, and theoretical modeling. Radiosurgery produces lesions with more delayed effects and seemed to result in changes in the white matter beyond the thalamic target.

Imaging Findings in MR Imaging-Guided Focused Ultrasound Treatment for Patients with Essential Tremor

“…This appearance of lesions and their evolution with time was similar to the imaging findings observed for stereotactic radiofrequency thalamotomies but quite different from those observed with gamma knife radiosurgery. 28 Direct comparison between the different treatment modalities in terms of imaging is available in pigs, 29 and further studies comparing MR imaging-guided focused sonogra- phy with radiofrequency ablation should be conducted in humans. Zones I and II showed restricted diffusion at 24 hours that pseudonormalized by 1 week or 1 month, when the cavity developing in the location of zones I and II collapsed.…”

Predicting lesion size during focused ultrasound thalamotomy: a review of 63 lesions over 3 clinical trials

“…Lesions were assessed based on the 3 concentric zones that occur on MRI during the thermal ablation process. 4,10 Zone 1 represents the hypointense central necrotic core, zone 2 is the surrounding T2 hyperintense cytotoxic edema region, and zone 3 is the less hyperintense T2 region corresponding to perilesional edema that resolves rapidly over time. The AC-PC length, lesion center relative to the PC, and the lateral and AP diameter of regions 1 and 2 were recorded in the AC-PC plane.…”

Intracranial Applications of Magnetic Resonance-guided Focused Ultrasound

“…However, lesions following radiosurgery evolved differently, with little radiographic evidence of a lesion at 3 months, and with histologic examination demonstrating a relatively less circumscribed lesion. There was also evidence for effects beyond the treated zone with radiosurgery, such as edema and macrophage infiltration, that were not seen with RF and MRgFUS lesions [23]. The spatial and temporal resolution of MR thermometry coupled to focused ultrasound has also been demonstrated in animal models, which have shown high degrees of precision, ensuring that temperature rises are tightly restricted to the volume of interest [24][25][26][27].…”