Factors related to successful energy transmission of focused ultrasound through a skull: A study in human cadavers and its comparison with clinical experiences

Na Young Jung, Itay Rachmilevitch, Ohad Sibiger, Talia Amar, Eyal Zadicario, Jin Woo Chang

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


Objective: Although magnetic resonance guided focused ultrasound (MRgFUS) has been used as minimally invasive and effective neurosurgical treatment, it exhibits some limitations, mainly related to acoustic properties of the skull barrier. This study was undertaken to identify skull characteristics that contribute to optimal ultrasonic energy transmission for MRgFUS procedures. Methods: For ex vivo skull experiments, various acoustic fields were measured under different conditions, using five non-embalmed cadaver skulls. For clinical skull analyses, brain computed tomography data of 46 patients who underwent MRgFUS ablations (18 unilateral thalamotomy, nine unilateral pallidotomy, and 19 bilateral capsulotomy) were retrospectively reviewed. Patients' skull factors and sonication parameters were comparatively analyzed with respect to the cadaveric skulls. Results: Skull experiments identified three important factors related skull penetration of ultrasound, including skull density ratio (SDR), skull volume, and incidence angle of the acoustic rays against the skull surface. In clinical results, SDR and skull volume correlated with maximal temperature (Tmax) and energy requirement to achieve Tmax (p<0.05). In addition, considering the incidence angle determined by brain target location, less energy was required to reach Tmax in the central, rather than lateral targets particularly when compared between thalamotomy and capsulotomy (p<0.05). Conclusion: This study reconfirmed previously identified skull factors, including SDR and skull volume, for successful MRgFUS; it identified an additional factor, incidence angle of acoustic rays against the skull surface. To guarantee successful transcranial MRgFUS treatment without suffering these various skull issues, further technical improvements are required.

Original languageEnglish
Pages (from-to)712-722
Number of pages11
JournalJournal of Korean Neurosurgical Society
Issue number6
Publication statusPublished - 2019 Nov

Bibliographical note

Funding Information:
Dr. Chang reports grants from the Michael J. Fox Foundation (New York, USA) and the Focused Ultrasound Surgery Foundation (Virginia, USA), during the conduct of the clinical study. Other authors have no conflict of interest to declare.

Publisher Copyright:
© 2019 The Korean Neurosurgical Society.

All Science Journal Classification (ASJC) codes

  • Surgery
  • Neuroscience(all)
  • Clinical Neurology


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