Integration of high-resolution data for temporal bone surgical simulations

Further Validity Evidence for Patient-Specific Virtual Reality Temporal Bone Surgical Simulation

OBJECTIVE

Patient-specific virtual reality (VR) simulation of cochlear implant (CI) surgery potentially enables preoperative rehearsal and planning. We aim to gather supporting validity evidence for patient-specific simulation through the analysis of virtual performance and comparison with postoperative imaging.

METHODS

Prospective, multi-institutional study. Pre- and postoperative cone-beam CT scans of CI surgical patients were obtained and processed for patient-specific VR simulation. The virtual performances of five trainees and four attendings were recorded and (1) compared with volumes removed during actual surgery as determined in postoperative imaging, and (2) assessed using the Copenhagen Cochlear Implant Surgery Assessment Tool (CISAT) by two blinded raters. The volumes compared were cortical mastoidectomy, facial recess, and round window (RW) cochleostomy as well as violation of the facial nerve and chorda.

RESULTS

Trainees drilled more volume in the cortical mastoidectomy and facial recess, whereas attendings drilled more volume for the RW cochleostomy and made more violations. Except for the cochleostomy, attendings removed volumes closer to that determined in postoperative imaging. Trainees achieved a higher CISAT performance score compared with attendings (22.0 vs. 18.4 points) most likely due to lack of certain visual cues.

CONCLUSION

We found that there were differences in performance of trainees and attendings in patient-specific VR simulation of CI surgery as assessed by raters and in comparison with actual drilled volumes. The presented approach of volume comparison is novel and might be used for further validation of patient-specific VR simulation before clinical implementation for preoperative rehearsal in temporal bone surgery.

LEVEL OF EVIDENCE

n/a Laryngoscope, 134:1403-1409, 2024.

High-Resolution CT Imaging of the Temporal Bone: A Cadaveric Specimen Study

Objective  Super-high and ultra-high spatial resolution computed tomography (CT) imaging can be advantageous for detecting temporal bone pathology and guiding treatment strategies. Methods  Six temporal bone cadaveric specimens were used to evaluate the temporal bone microanatomic structures utilizing the following CT reconstruction modes: normal resolution (NR, 0.5-mm slice thickness, 512 ² matrix), high resolution (HR, 0.5-mm slice thickness, 1,024 ² matrix), super-high resolution (SHR, 0.25-mm slice thickness, 1,024 ² matrix), and ultra-high resolution (UHR, 0.25-mm slice thickness, 2,048 ² matrix). Noise and signal-to-noise ratio (SNR) for bone and air were measured at each reconstruction mode. Two observers assessed visualization of seven small anatomic structures using a 4-point scale at each reconstruction mode. Results  Noise was significantly higher and SNR significantly lower with increases in spatial resolution (NR, HR, and SHR). There was no statistical difference between SHR and UHR imaging with regard to noise and SNR. There was significantly improved visibility of all temporal bone osseous structures of interest with SHR and UHR imaging relative to NR imaging ( p  < 0.001) and most of the temporal bone osseous structures relative to HR imaging. There was no statistical difference in the subjective image quality between SHR and UHR imaging of the temporal bone ( p  ≥ 0.085). Conclusion  Super-high-resolution and ultra-high-resolution CT imaging results in significant improvement in image quality compared with normal-resolution and high-resolution CT imaging of the temporal bone. This preliminary study also demonstrates equivalency between super-high and ultra-high spatial resolution temporal bone CT imaging protocols for clinical use.

Patient-specific Virtual Temporal Bone Simulation Based on Clinical Cone-beam Computed Tomography

OBJECTIVES

Patient-specific surgical simulation allows presurgical planning through three-dimensional (3D) visualization and virtual rehearsal. Virtual reality simulation for otologic surgery can be based on high-resolution cone-beam computed tomography (CBCT). This study aimed to evaluate clinicians' experience with patient-specific simulation of mastoid surgery.

METHODS

Prospective, multi-institutional study. Preoperative temporal bone CBCT scans of patients undergoing cochlear implantation (CI) were retrospectively obtained. Automated processing and segmentation routines were used. Otologic surgeons performed a complete mastoidectomy with facial recess approach on the patient-specific virtual cases in the institution's temporal bone simulator. Participants completed surveys regarding the perceived accuracy and utility of the simulation.

RESULTS

Twenty-two clinical CBCTs were obtained. Four attending otologic surgeons and 5 otolaryngology trainees enrolled in the study. The mean number of simulations completed by each participant was 16.5 (range 3-22). "Overall experience" and "usefulness for presurgical planning" were rated as "good," "very good," or "excellent" in 84.6% and 71.6% of the simulations, respectively. In 10.7% of simulations, the surgeon reported to have gained a significantly greater understanding of the patient's anatomy compared to standard imaging. Participants were able to better appreciate subtle anatomic findings after using the simulator for 60.4% of cases. Variable CBCT acquisition quality was the most reported limitation.

CONCLUSION

Patient-specific simulation using preoperative CBCT is feasible and may provide valuable insights prior to otologic surgery. Establishing a CBCT acquisition protocol that allows for consistent segmentation will be essential for reliable surgical simulation.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:1855-1862, 2021.