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Registration of contours generated on 2D endoscopic images to 3D planning space is feasible, with accuracy smaller than typical set-up margins. Used in addition to standard 3D contouring methods in radiation planning, the technology may improve gross tumour volume (GTV) delineation for superficial tumors in luminal sites that are only visible in endoscopy.

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BackgroundWe set out to determine the accuracy of 3D-navigated mandibular and maxillary osteotomies with the ultimate aim to integrate virtual cutting guides and 3D-navigation into ablative and reconstructive head and neck surgery.MethodsFour surgeons (two attending, two clinical fellows) completed 224 unnavigated and 224 3D-navigated osteotomies on anatomical models according to preoperative 3D plans. The osteotomized bones were scanned and analyzed.ResultsMedian distance from the virtual plan was 2.1 mm unnavigated (IQR 2.6 mm, ≥3 mm in 33%) and 1.2 mm 3D-navigated (IQR 1.1 mm, ≥3 mm in 6%) (P<0.0001); median pitch was 4.5° unnavigated (IQR 7.1°) and 3.5° 3D-navigated (IQR 4.0°) (P<0.0001); median roll was 7.4° unnavigated (IQR 8.5°) and 2.6° 3D-navigated (IQR 3.8°) (P<0.0001).Conclusion3D-rendering enables osteotomy navigation. 3 mm is an appropriate planning distance. The next steps are translating virtual cutting guides to free bone flap reconstruction and clinical use.

Objectives: Surgical navigation systems based on preoperative imaging are now increasingly used for guidance of head and neck resection and reconstruction. The primary aim of this study was to quantify osteotomy cutting accuracy using an image-guidance system for intraoperative cone-beam computed tomography (CBCT) imaging and surgical saw navigation. To enable clinical translation of this CBCT-guided navigation system, a secondary aim of the study was to design and fabricate a patient reference tracker suitable for clinical use on a mobile mandible.Methods: First, a preclinical cadaveric study was performed to quantify navigation accuracy with the use of clinically suitable patient reference trackers. Second, a proof-of-principle patient study was conducted to evaluate this technique under clinical conditions.Results: In both preclinical (5 cadavers) and clinical (5 patients) experiments, the mean cutting accuracy was less than 2 mm. In all preclinical specimens, bilateral mandibulectomies and bilateral maxillectomies were performed, for a total of 20 cut planes for analysis. The mean (standard deviation [SD]) values for distance, pitch, and roll were 1.4 mm (1.1 mm), 4.2 (3.5 ), and 2.9 (2.5 ) mm, respectively. Five mandibulectomies were performed on five patients, for a total of 10 cut planes for analysis. The mean (SD) values for distance, pitch, and roll were 1.7 mm (0.8 mm), 5.4 (1.5 ), and 6.7 (4.6 ) mm, respectively.Conclusions: The overall performance in comparison to alternative approaches warrants further consideration. In terms of accuracy, the results presented here are comparable to recent systematic reviews assessing CAD-CAM cutting guides that cite accuracies of~2 to 2.5 mm.

We have developed a method to register and display 3D parametric data, in particular radiation dose, on two-dimensional endoscopic images. This registration of radiation dose to endoscopic or optical imaging may be valuable in assessment of normal tissue response to radiation, and visualization of radiated tissues in patients receiving post-radiation surgery. Electromagnetic sensors embedded in a flexible endoscope were used to track the position and orientation of the endoscope allowing registration of 2D endoscopic images to CT volumetric images and radiation doses planned with respect to these images. A surface was rendered from the CT image based on the air/tissue threshold, creating a virtual endoscopic view analogous to the real endoscopic view. Radiation dose at the surface or at known depth below the surface was assigned to each segment of the virtual surface. Dose could be displayed as either a colorwash on this surface or surface isodose lines. By assigning transparency levels to each surface segment based on dose or isoline location, the virtual dose display was overlaid onto the real endoscope image. Spatial accuracy of the dose display was tested using a cylindrical phantom with a treatment plan created for the phantom that matched dose levels with grid lines on the phantom surface. The accuracy of the dose display in these phantoms was 0.8-0.99 mm. To demonstrate clinical feasibility of this approach, the dose display was also tested on clinical data of a patient with laryngeal cancer treated with radiation therapy, with estimated display accuracy of ∼2-3 mm. The utility of the dose display for registration of radiation dose information to the surgical field was further demonstrated in a mock sarcoma case using a leg phantom. With direct overlay of radiation dose on endoscopic imaging, tissue toxicities and tumor response in endoluminal organs can be directly correlated with the actual tissue dose, offering a more nuanced assessment of normal tissue toxicities following radiation therapy and accurate registration of radiation dose to the surgical field.