The Distribution of Skull Score and Skull Density Ratio in Tremor Patients for MR-Guided Focused Ultrasound Thalamotomy

Kevin Wen-Kai Tsai; Jui-Cheng Chen; Hui-Chin Lai; Wei-Chieh Chang; Takaomi Taira; Jin Woo Chang; Cheng-Yu Wei

doi:10.3389/fnins.2021.612940

The Distribution of Skull Score and Skull Density Ratio in Tremor Patients for MR-Guided Focused Ultrasound Thalamotomy

Front Neurosci. 2021 May 17:15:612940. doi: 10.3389/fnins.2021.612940. eCollection 2021.

Authors

Kevin Wen-Kai Tsai¹, Jui-Cheng Chen^{2

3

4}, Hui-Chin Lai¹, Wei-Chieh Chang^{1

5}, Takaomi Taira⁶, Jin Woo Chang⁷, Cheng-Yu Wei^{8

9}

Affiliations

¹ MR-guided Focused Ultrasound Center, Chang Bing Show Chwan Memorial Hospital, Changhua City, Taiwan.
² Neuroscience Laboratory, Department of Neurology, China Medical University Hospital, Taichung City, Taiwan.
³ School of Medicine, College of Medicine, China Medical University, Taichung City, Taiwan.
⁴ Department of Neurology, China Medical University Hsinchu Hospital, Hsinchu, Taiwan.
⁵ Department of Neurosurgery, Chang Bing Show Chwan Memorial Hospital, Changhua City, Taiwan.
⁶ Department of Neurosurgery, Tokyo Women's Medical University, Tokyo, Japan.
⁷ Department of Neurosurgery, Yonsei University College of Medicine, Seoul, South Korea.
⁸ Department of Exercise and Health Promotion, College of Kinesiology and Health, Chinese Culture University, Taipei, Taiwan.
⁹ Department of Neurology, Chang Bing Show Chwan Memorial Hospital, Changhua City, Taiwan.

Abstract

Objective: Magnetic resonance-guided focused ultrasound (MRgFUS) is a minimum-invasive surgical approach to non-incisionally cause the thermos-coagulation inside the human brain. The skull score (SS) has already been approved as one of the most dominant factors related to a successful MRgFUS treatment. In this study, we first reveal the SS distribution of the tremor patients, and correlate the SS with the image feature from customized skull density ratio (cSDR). This correlation might give a direction to future clinical studies for improving the SS.

Methods: Two hundred and forty-six patients received a computed tomography (CT) scan of the brain, and a bone-enhanced filter was applied and reconstructed to a high spatial resolution CT images. The SS of all patients would be estimated by the MRgFUS system after importing the reconstructed CT images into the MRgFUS system. The histogram and the cumulative distribution of the SS from all the patients were calculated to show the percentage of the patients whose SS lower than 0.3 and 0.4. The same CT images of all patients were utilized to calculated the cSDR by first segmented the trabecular bone and the cortical bone from the CT images and divided the average trabecular bone intensity (aTBI) by the average cortical bone intensity (aCBI). The Pearson's correlations between the SS and the cSDR, aTBI, and the aCBI were calculated, respectively.

Results: There were 19.19 and 50% of the patient who had the SS lower than the empirical threshold 0.3 and 0.4, respectively. The Pearson's correlation between the SS and the cSDR, aCBI, and the aTBI were R = 0.8145, 0.5723, and 0.8842.

Conclusion: Half of the patients were eligible for the MRgFUS thalamotomy based on the SS, and nearly 20% of patients were empirically difficult to achieve a therapeutic temperature during MRgFUS. The SS and our cSDR are highly correlated, and the SS had a higher correlation with aTBI than with aCBI. This is the first report to explicitly reveal the SS population and indicate a potential way to increase the chance to achieve a therapeutic temperature for those who originally have low SS.

Keywords: MR-guided focused ultrasound thalamotomy; essential tremor; skull density ratio; skull score; tremor.