Kranion, an open-source environment for planning transcranial focused ultrasound surgery: technical note

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Transcranial focused ultrasound (FUS) ablation is an emerging incision-less treatment for neurological disorders. The factors affecting FUS treatment efficiency are not well understood. Kranion is open-source software that allows the user to simulate the planning stages of FUS treatment and to “replay” previous treatments for off-line analysis. This study aimed to investigate the relationship between skull parameters and treatment efficiency and to create a metric to estimate temperature rise during FUS. CT images from 28 patients were analyzed to validate the use of Kranion. For stereotactic targets within each patient, individual transducer element incident angles, skull density ratio, and skull thickness measurements were recorded. A penetration metric (the “beam index”) was calculated by combining the energy loss from incident angles and the skull thickness. Kranion accurately estimated the patient’s skull and treatment parameters. The authors observed significant changes in incident angles with different targets in the brain. Using the beam index as a predictor of temperature rise in a linear-mixed-effects model, they were able to predict the average temperature rise at the focal point during ablation with < 21% error (55°C ± 3.8°C) in 75% of sonications, and with < 44% (55°C ± 7.9°C) in 97% of sonications. This research suggests that the beam index can improve the prediction of temperature rise during FUS. Additional work is required to study the relationship between temperature rise and lesion shape and clinical outcomes.

ABBREVIATIONS FUS = focused ultrasound; GPi = globus pallidus pars interna; SDR = skull density ratio; VIM = ventral intermediate thalamus.

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  • Supplementary Material (PDF 629 KB)

Article Information

Correspondence Vibhor Krishna: The Ohio State University, Columbus, OH. vibhor.krishna@osumc.edu.

INCLUDE WHEN CITING Published online March 1, 2019; DOI: 10.3171/2018.11.JNS181995.

F.S. and D.W.B. share first authorship of this work.

Disclosures Dr. Krishna reports receiving research grants from the following sources: Focused Ultrasound Foundation, Insightec Inc., National Science Foundation, Medtronic Inc., and Ohio Department of Higher Education.

© AANS, except where prohibited by US copyright law.

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Figures

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    A scene from Kranion replaying an FUS treatment. Kranion is an open-source research platform. © 2016 Focused Ultrasound Foundation. Figure is available in color online only.

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    A: Comparative histogram of the SDR values calculated by the vendor (blue) and SDR values calculated using Kranion (red). Lines are drawn at the SDR value of 0.4, the clinical threshold used to screen patients. Five patients had an SDR < 0.4 with both methods, 21 patients had an SDR ≥ 0.4 with both methods, and 2 patients had an SDR ≥ 0.4 when calculated by the vendor but SDR < 0.4 when calculated with Kranion. B: Box-and-whisker plots comparing the number of active elements in the standard of care (left) and the value calculated by Kranion (right). There is a statistically significant difference between the two data sets. C: Box-and-whisker plots comparing the number of effective elements (incident angle < 20°) in the standard of care (left) and the value calculated by Kranion (right). There is no statistically significant difference between the two data sets. Figure is available in color online only.

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    Scatter plots where the x and y coordinates of a circle indicate the location of an individual transducer element on the array, and the color of each circle indicates the frequency of which the transducer element was effective (incident angle < 20°) for the indicated structure: left nucleus accumbens (A), right nucleus accumbens (B), left anterior thalamic nucleus (C), right anterior thalamic nucleus (D), left GPi (E), right GPi (F), left VIM (G), and right VIM (H). Figure is available in color online only.

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    Filled contour plot that classifies the predicted temperature for each sonication (see Supplementary Material section 7 for details about classification). Figure is available in color online only.

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