Martin, David;
Xu, Rui;
Dressler, Max;
O’Reilly, Meaghan A;
(2024)
Ex vivo validation of non-invasive phase correction for transspine focused ultrasound: model performance and target feasibility.
Physics in Medicine & Biology
, 69
(23)
, Article 235001. 10.1088/1361-6560/ad8fed.
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Abstract
Objective. To evaluate the feasibility of transspine focused ultrasound using simulation-based phase corrections from a CT-derived ray acoustics model. Approach. Bilateral transspine focusing was performed in ex vivo human vertebrae with a spine-specific ultrasound array. Ray acoustics-derived phase correction was compared to geometric focusing and a hydrophone-corrected gold standard. Planar hydrophone scans were recorded in the spinal canal and three metrics were calculated: target pressure, coronal and sagittal focal shift, and coronal and sagittal Sørensen–Dice similarity to the free-field. Post hoc analysis was performed in silico to assess the impact of windows between vertebrae on focal shift. Main results. Hydrophone correction reduced mean sagittal plane shift from 1.74 ± 0.82 mm to 1.40 ± 0.82 mm and mean coronal plane shift from 1.07 ± 0.63 mm to 0.54 ± 0.49 mm. Ray acoustics correction reduced mean sagittal plane and coronal plane shift to 1.63 ± 0.83 mm and 0.83 ± 0.60 mm, respectively. Hydrophone correction increased mean sagittal similarity from 0.48 ± 0.22 to 0.68 ± 0.19 and mean coronal similarity from 0.48 ± 0.23 to 0.70 ± 0.19. Ray acoustics correction increased mean sagittal and coronal similarity to 0.53 ± 0.25 and 0.55 ± 0.26, respectively. Target pressure was relatively unchanged across beamforming methods. In silico analysis found that, for some targets, unoccluded paths may have increased focal shift. Significance. Gold standard phase correction significantly reduced coronal shift and significantly increased sagittal and coronal Sørensen–Dice similarity (p < 0.05). Ray acoustics-derived phase correction reduced sagittal and coronal shift and increased sagittal and coronal similarity but did not achieve statistical significance. Across beamforming methods, mean focal shift was comparable to MRI resolution, suggesting that transspine focusing is possible with minimal correction in favourable targets. Future work will explore the mitigation of acoustic windows with anti-focus control points.
| Type: | Article |
|---|---|
| Title: | Ex vivo validation of non-invasive phase correction for transspine focused ultrasound: model performance and target feasibility |
| Location: | England |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1088/1361-6560/ad8fed |
| Publisher version: | https://doi.org/10.1088/1361-6560/ad8fed |
| Language: | English |
| Additional information: | Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 license, https://creativecommons.org/licenses/by/4.0/. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10201454 |
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