3D Rapid Prototyping for Otolaryngology—Head and Neck Surgery: Applications in Image-Guidance, Surgical Simulation and Patient-Specific Modeling

<div><p>The aim of this study was to demonstrate the role of advanced fabrication technology across a broad spectrum of head and neck surgical procedures, including applications in endoscopic sinus surgery, skull base surgery, and maxillofacial reconstruction. The initial case studies demonstrated three applications of rapid prototyping technology are in head and neck surgery: i) a mono-material paranasal sinus phantom for endoscopy training ii) a multi-material skull base simulator and iii) 3D patient-specific mandible templates. Digital processing of these phantoms is based on real patient or cadaveric 3D images such as CT or MRI data. Three endoscopic sinus surgeons examined the realism of the endoscopist training phantom. One experienced endoscopic skull base surgeon conducted advanced sinus procedures on the high-fidelity multi-material skull base simulator. Ten patients participated in a prospective clinical study examining patient-specific modeling for mandibular reconstructive surgery. Qualitative feedback to assess the realism of the endoscopy training phantom and high-fidelity multi-material phantom was acquired. Conformance comparisons using assessments from the blinded reconstructive surgeons measured the geometric performance between intra-operative and pre-operative reconstruction mandible plates. Both the endoscopy training phantom and the high-fidelity multi-material phantom received positive feedback on the realistic structure of the phantom models. Results suggested further improvement on the soft tissue structure of the phantom models is necessary. In the patient-specific mandible template study, the pre-operative plates were judged by two blinded surgeons as providing optimal conformance in 7 out of 10 cases. No statistical differences were found in plate fabrication time and conformance, with pre-operative plating providing the advantage of reducing time spent in the operation room. The applicability of common model design and fabrication techniques across a variety of otolaryngological sub-specialties suggests an emerging role for rapid prototyping technology in surgical education, procedure simulation, and clinical practice.</p></div

Illustration of a high-fidelity sinus and skull base phantom for surgical simulation.

<p>(a) Bone module with realistic sinus structures. (b) Soft-tissue module printed with flexible material that imitates cartilaginous structures. (c) Assembly of bone and soft-tissue with designed joints. (d) CT images of the phantom show appropriate X-ray attenuation number.</p

Illustration of the endoscopic navigation head and neck phantom.

<p>(a) Computer model of the final phantom design. (b) Semi-transparent view showing fiducial marker locations in the phantom. (c) Section view showing possible trajectories for surgical instruments.</p

Illustration of patient-specific mandible 3D printing for reconstructive surgery.

<p>(a) Mesh wireframe computer model of the mandible. (b) Photograph of the printed mandible with the titanium plate. (c) Pre-operative moulded plate with mandible template, and (d) its use for mandible reconstruction following surgical ablation of a segment of the mandible.</p

Custom 3D visualization software application illustrating CBCT-endoscopy fusion in the head and neck phantom.

<p>(a)-(c) Triplanar CBCT views with surgical contour and tracked tool overlays; (d) endoscopic video with real-time correction of lens distortion; (e) virtual and (f) augmented endoscopic views of semi-transparent CBCT surface renderings (e.g., wiremesh, partial opacity) generated from the perspective of tracked endoscope enable direct visualization of critical structures (e.g., optic nerve, carotid artery) behind surface anatomy.</p

Photographs of 3D endoscopic phantom for the development of real-time tracking/navigation and image fusion methods.

<p>(a) The resulting phantom printed with ABS material. Endoscopic images of: (b) the fiducial marker on right cribriform plate; (c) the fiducial marker at the posterior aspect of the sphenoid sinus; d) the peg feature in the frontal recess; and (e) a view of the nasopharynx.</p

Confidence intervals (95% CIs) for best-fit model parameter values.

<p>Confidence intervals (95% CIs) for best-fit model parameter values.</p

Effect of catalase on CIR resistance.

<p><b>a</b>: Growth of DR and DR<i>kat</i>^- under 36 Gy/h, or without CIR. Dilutions of DR and DR<i>kat</i>^- are indicated. <b>b</b>: Growth restoration of DR<i>kat</i>^- under 36 Gy/h by catalase, added to the central area of a TGY plate that was pre-inoculated with DR<i>kat</i>^- cells. Dilutions (log₁₀ based) of inoculated DR<i>kat</i>^- are indicated.</p

Comparison of observed and model-predicted growth-inhibitory critical CIR dose rates for microorganisms grown under aerobic conditions.

<p><b>a</b>: Bacteria. <b>b</b>: Fungi. Green diamonds: <i>highest</i> tested dose rate at which <i>any</i> growth was observed. Red squares: <i>lowest</i> tested dose rate at which <i>no</i> growth was observed. Blue curves: best-fit model predictions. Black points: uncertainty range of model predictions. Model-based predictions at cell concentrations higher than those tested had very large uncertainties for EC2 and SC and, therefore, the prediction curves were truncated at cell concentrations slightly above 0 dilution for these organisms.</p

A schematic representation of the effects of cell concentration on microbial resistance to CIR.

<p>A schematic representation of the effects of cell concentration on microbial resistance to CIR.</p