Photoacoustic imaging of a human vertebra: implications for guiding spinal fusion surgeries

Abstract

It is well known that there are structural differences between cortical and cancellous bone. However, spinal surgeons currently have no reliable method to non-invasively determine these differences in real-time when choosing the optimal starting point and trajectory to insert pedicle screws and avoid surgical complications associated with breached or weakened bone. This paper explores 3D photoacoustic imaging of a human vertebra to noninvasively differentiate cortical from cancellous bone for this surgical task. We observed that signals from the cortical bone tend to appear as compact, high-amplitude signals, while signals from the cancellous bone have lower amplitudes and are more diffuse. In addition, we discovered that the location of the light source for photoacoustic imaging is a critical parameter that can be adjusted to non-invasively determine the optimal entry point into the pedicle. Once inside the pedicle, statistically significant differences in the contrast and SNR of signals originating from the cancellous core of the pedicle (when compared to signals originating from the surrounding cortical bone) were obtained with laser energies of 0.23-2.08 mJ (p < 0.05). Similar quantitative differences were observed with an energy of 1.57 mJ at distances ⩾6 mm from the cortical bone of the pedicle. These quantifiable differences between cortical and cancellous bone (when imaging with an ultrasound probe in direct contact with each bone type) can potentially be used to ensure an optimal trajectory during surgery. Our results are promising for the introduction and development of photoacoustic imaging systems to overcome a wide range of longstanding challenges with spinal surgeries, including challenges with the occurrence of bone breaches due to misplaced pedicle screws.

Feasibility Study of Precise Balloon Catheter Tracking and Visualization with Fast Photoacoustic Microscopy

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Photoacoustic imaging in the second near-infrared window: a review

“…However, it is often difficult to deliver miniature probes to the surgical site without sacrificing the image quality. PAI has the potential to enable real-time visualization of regions of interest during surgery [159][160][161][162] and biopsy. 163,164 A 1064-nm side-firing fiber prototype for transurethral PAI of prostates with a dual-array (4-8 MHz/linear and 5-9 MHz/curvilinear) is reported.…”

In vivo photoacoustic guidance of stem cell injection and delivery for regenerative spinal cord therapies

“…Previous ex vivo studies using PA imaging in the spine demonstrate the capabilities of new imaging tools to guide surgery and therapies. 3,4,13,23,24 Current in vivo findings on intraoperative US/PA guidance are vital to supporting further development of the trimodal US/PA/MR imaging approach to monitor stem cell therapies in the spinal cord. Results may extend to other research and clinical spine-related applications in intra-and postoperative settings.…”