Angelique M. Berens

Computer-Aided Design and 3D Printing to Produce a Costal Cartilage Model for Simulation of Auricular Reconstruction.

M icrotia, or underdevelopment of the auricle, affects approximately 0.03% of live births. Carving an auricular cartilage framework from autogenous cartilage—the most common technique for auricular reconstruction—is one of the most challenging skills for the reconstructive surgeon to learn. Given the potential morbidity associated with technical errors in framework carving, opportunities for acquisition of this skill are limited. It is critical for surgeons to be able to practice their carving skills. This presents an opportunity for surgical simulation. Materials previously used for simulation of auricular framework carving include carrots, potatoes, porcine/bovine/human cadaveric costal cartilage, and dental impression material. These materials poorly represent the geometry, texture, and size of the harvested costal cartilage presented to the reconstructive surgeon. There is a commercially available model (Medicon, Tuttlingen, Germany) that is based on adult rib and is costly. To better represent pediatric rib geometry and texture, techniques were developed to produce negative molds from harvested pediatric rib cartilage. While these methods are an improvement on the simulation of shape and size, questions remained on the similarity of the material to costal cartilage. In this report, we aim to use computer-aided design and 3dimensional (3D) printing to create a representative pediatric costal cartilage model for simulation of auricular framework reconstruction. Furthermore, with computed tomography scan data, the potential for patient-specific simulation is introduced, allowing for surgical planning.

Evaluation of segmentation methods on head and neck CT: Auto‐segmentation challenge 2015

Purpose Automated delineation of structures and organs is a key step in medical imaging. However, due to the large number and diversity of structures and the large variety of segmentation algorithms, a consensus is lacking as to which automated segmentation method works best for certain applications. Segmentation challenges are a good approach for unbiased evaluation and comparison of segmentation algorithms. Methods In this work, we describe and present the results of the Head and Neck Auto‐Segmentation Challenge 2015, a satellite event at the Medical Image Computing and Computer Assisted Interventions (MICCAI) 2015 conference. Six teams participated in a challenge to segment nine structures in the head and neck region of CT images: brainstem, mandible, chiasm, bilateral optic nerves, bilateral parotid glands, and bilateral submandibular glands. Results This paper presents the quantitative results of this challenge using multiple established error metrics and a well‐defined ranking system. The strengths and weaknesses of the different auto‐segmentation approaches are analyzed and discussed. Conclusions The Head and Neck Auto‐Segmentation Challenge 2015 was a good opportunity to assess the current state‐of‐the‐art in segmentation of organs at risk for radiotherapy treatment. Participating teams had the possibility to compare their approaches to other methods under unbiased and standardized circumstances. The results demonstrate a clear tendency toward more general purpose and fewer structure‐specific segmentation algorithms.

An Automated Methodology for Assessing Anatomy-Specific Instrument Motion during Endoscopic Endonasal Skull Base Surgery

Objectives Describe instrument motion during live endoscopic skull base surgery (ESBS) and evaluate kinematics within anatomic regions. Design Case series. Setting Tertiary academic center. Participants A single skull base surgeon performed six anterior skull base approaches to the pituitary. Main Outcomes and Measures Time‐stamped instrument coordinates were recorded using an optical tracking system. Kinematics (i.e., mean cumulative instrument travel, velocity, acceleration, and angular velocity) was calculated by anatomic region including nasal vestibule, anterior and posterior ethmoid, sphenoid, and lateral opticocarotid recess (lOCR) regions. Results We observed mean (standard deviation, SD) velocities of 6.14 cm/s (1.55) in the nasal vestibule versus 1.65 cm/s (0.34) near the lOCR. Mean (SD) acceleration was 7,480 cm/s2 (5790) in the vestibule versus 928 cm/s2 (662) near the lOCR. Mean (SD) angular velocity was 17.2 degrees/s (8.31) in the vestibule and 5.37 degrees/s (1.09) near the lOCR. We observed a decreasing trend in the geometric mean velocity, acceleration, and angular velocity when approaching the pituitary (p < 0.001). Conclusion Using a novel method for analyzing instrument motion during live ESBS, we observed a decreasing trend in kinematics with proximity to the pituitary. Additional characterization of surgical instrument motion is paramount for optimizing patient safety and training.

Transorbital endoscopic identification of supernumerary ethmoid arteries

Background Anterior and posterior ethmoid arteries supply the paranasal sinuses, septum, and lateral nasal wall. Precise identification of these arteries is important during anterior skull base procedures, endoscopic sinus surgery, and ligation of ethmoid arteries for epistaxis refractory to standard treatment. There is controversy in the literature regarding the prevalence of supernumerary ethmoid arteries. Objective This study examined the prevalence of supernumerary ethmoid arteries by using direct visualization after transorbital endoscopic dissection. Methods Nineteen cadaveric specimens were evaluated by using a superior lid crease (blepharoplasty) incision and an endoscopic approach to the medial orbital wall. Ethmoid arteries were identified as they pierced the lamina papyracea coplanar with the skull base and optic nerve. The distances from the anterior lacrimal crest to the ethmoid arteries and optic nerve were measured with a surgical ruler under endoscopic guidance. Results Thirty-eight cadaveric orbits were measured. Overall, there were three or more ethmoid arteries (including anterior and posterior arteries) in 58% of orbits, with 8% of the total sample that contained four or more ethmoid arteries. The average number of ethmoid arteries was 2.7. Bilateral supernumerary ethmoid arteries were noted in 42% of the specimens. The distance between the anterior lacrimal crest and the anterior ethmoid, posterior ethmoid, and optic nerve averaged 20, 35, and 41 mm, respectively. The average distance to the supernumerary or middle ethmoid artery was 29 mm. Conclusion This study found supernumerary ethmoid arteries in 58% of cadaveric specimens, a prevalence much higher than previously reported. Recognition of these additional vessels may improve safety during endoscopic sinus surgery and skull base surgery, and may permit more effective ligation for refractory epistaxis originating from the ethmoid system.

Region-Specific Objective Signatures of Endoscopic Surgical Instrument Motion: A Cadaveric Exploratory Analysis

Objectives The objective of this study was to evaluate region‐specific surgical instrument kinematics among novice and experienced surgeons performing endoscopic endonasal skull base surgery. Design Cadaveric experimental study. Setting Tertiary academic center. Participants Two novice and two experienced surgeons performed eight endoscopic total ethmoidectomies and sphenoidotomies using an optically tracked microdebrider. Main Outcome Measures Time‐stamped Euclidian coordinates were recorded. Cumulative instrument travel, mean linear velocity and acceleration, and mean angular velocities were calculated in the anterior ethmoid, posterior ethmoid, and sphenoid sinus regions. Results Mean cumulative instrument travel (standard deviation) was highest in the posterior ethmoid region for both novice and experienced surgeons (9,795 mm [1,664] vs. 3,833 mm [1,080]). There was a trend in mean linear and angular velocities, and acceleration with increasing magnitudes for experienced surgeons compared with novices. Among experienced surgeons, we observed a trend of decreasing yaw velocity during the approach to the surgical target. Conclusions We present a novel method of evaluating surgical instrument motion with respect to anatomical regions of the skull base during endoscopic endonasal skull base surgery. These data may be used in the development of surgical monitoring and training systems to optimize patient safety.

Efficient orbital structures segmentation with prior anatomical knowledge

Abstract. We present a fully automatic method for segmenting orbital structures (globes, optic nerves, and extraocular muscles) in CT images. Prior anatomical knowledge, such as shape, intensity, and spatial relationships of organs and landmarks, were utilized to define a volume of interest (VOI) that contains the desired structures. Then, VOI was used for fast localization and successful segmentation of each structure using predefined rules. Testing our method with 30 publicly available datasets, the average Dice similarity coefficient for right and left sides of [0.81, 0.79] eye globes, [0.72, 0.79] optic nerves, and [0.73, 0.76] extraocular muscles were achieved. The proposed method is accurate, efficient, does not require training data, and its intuitive pipeline allows the user to modify or extend to other structures.

Evaluation of a Minimally Disruptive Treatment Protocol for Frontal Sinus Fractures

Importance Despite common goals of frontal sinus fracture treatment (restoring forehead contour and creating a safe sinus), there remains significant variability in evaluation and treatment. Objective To describe our experience with a minimally disruptive treatment protocol for the treatment of frontal sinus fractures. Design, Setting, and Participants Analysis of prospectively collected data from 2010 through 2015 at a level 1 trauma center. All patients with frontal sinus fractures treated with our protocol from January 2010 to December 2015. Patients with poor follow-up and/or incomplete medical records were excluded from analysis. Main Outcomes and Measures Presence of an aerated frontal sinus and aesthetically acceptable forehead contour. Secondary outcome measures were complications related to frontal sinus fractures. Results A total of 39 patients were treated under our minimally disruptive protocol, and 25 patients were included in the study; 18 (72%) were male and 7 (28%) were female. Their ages ranged from 6 to 62 years. After review, 22 patients had both clinical and radiographic follow-up. No patients underwent immediate frontal sinus repair. Five of 22 patients underwent surgery for indications other than their frontal sinus fracture: 1 of 5 patients underwent immediate surgical repair due to bilateral LeFort fractures, and 4 of 5 underwent delayed surgery due to nasal polyps (1 patient), scar revision (1 patient), and concomitant LeFort fractures (2 patients). Two of 22 patients (9%) underwent frontal sinus repair after outpatient surveillance due to persistent cerebrospinal fluid leak (1 patient) and orbital roof fracture (1 patient). The remaining 20 patients were treated nonoperatively, and 19 of 20 (95%) had spontaneous improvement in opacification and/or contour deformity. Twelve of 20 patients (60%) had improvement or resolution in both. One patient had ongoing partial opacification and deformity at the 3-month follow-up but was asymptomatic and had bony contour that was aesthetically acceptable to the patient. There were no complications. The median of all follow-up was 3 months. Conclusions and Relevance Frontal sinus fractures treated nonoperatively had a high rate of spontaneous ventilation and bony autoreduction with aesthetically acceptable frontal bone remodeling. There were no complications in the nonoperative group. The initial results of this study support further study of the safety and efficacy of a minimally disruptive protocol for frontal sinus fractures. Level of Evidence 4.

Complications in facial Mohs defect reconstruction

Purpose of review To review the recent literature in regards to complications after reconstruction of Mohs defects, outline common pitfalls and to discuss the literature on avoiding complications as outlined per aesthetic subunit. Recent findings Complications in facial Mohs reconstruction commonly consist of infection, wound necrosis and dehiscence, hematoma and suboptimal scarring. However, site-specific complications such as hairline or eyebrow distortion, eyelid retraction or ectropion, nasal contour abnormality, alar retraction, nasal valve compromise, significant facial asymmetry or even oral incompetence must also be considered. Summary A successful reconstruction mimics the premorbid state and maintains function. The use of perioperative antibiotics, sterile technique, meticulous hemostasis, subcutaneous dissection and deep sutures to minimize wound tension should be considered for all Mohs reconstructions. Cartilage grafting can minimize nasal deformity and obstruction. Reconstruction near the lower eyelid should employ periosteal suspension sutures to minimize downward tension and lid retraction. Perioral complications, such as microstomia and oral incompetence, typically improve with time and therapy. Always consider secondary procedures such as dermabrasion, steroid injection, scar revision and laser resurfacing to help optimize aesthetic outcome.

Quantitative Analysis of Transnasal Anterior Skull Base Approach: Report of Technology for Intraoperative Assessment of Instrument Motion:

Objective: To develop a method to measure intraoperative surgical instrument motion. This model will be applicable to the study of surgical instrument kinematics including surgical training, skill verification, and the development of surgical warning systems that detect aberrant instrument motion that may result in patient injury. Design: We developed an algorithm to automate derivation of surgical instrument kinematics in an endoscopic endonasal skull base surgery model. Surgical instrument motion was recorded during a cadaveric endoscopic transnasal approach to the pituitary using a navigation system modified to record intraoperative time-stamped Euclidian coordinates and Euler angles. Microdebrider tip coordinates and angles were referenced to the cadaver’s preoperative computed tomography scan allowing us to assess surgical instrument kinematics over time. A representative cadaveric endoscopic endonasal approach to the pituitary was performed to demonstrate feasibility of our algorithm for deriving surgical instrument kinematics. Conclusions: Technical feasibility of automatically measuring intraoperative surgical instrument motion and deriving kinematics measurements was demonstrated using standard navigation equipment.

Atlas and feature based 3D pathway visualization enhancement for skull base pre-operative fast planning from head CT

Minimally invasive neuroendoscopic surgery provides an alternative to open craniotomy for many skull base lesions. These techniques provides a great benefit to the patient through shorter ICU stays, decreased post-operative pain and quicker return to baseline function. However, density of critical neurovascular structures at the skull base makes planning for these procedures highly complex. Furthermore, additional surgical portals are often used to improve visualization and instrument access, which adds to the complexity of pre-operative planning. Surgical approach planning is currently limited and typically involves review of 2D axial, coronal, and sagittal CT and MRI images. In addition, skull base surgeons manually change the visualization effect to review all possible approaches to the target lesion and achieve an optimal surgical plan. This cumbersome process relies heavily on surgeon experience and it does not allow for 3D visualization. In this paper, we describe a rapid pre-operative planning system for skull base surgery using the following two novel concepts: importance-based highlight and mobile portal. With this innovation, critical areas in the 3D CT model are highlighted based on segmentation results. Mobile portals allow surgeons to review multiple potential entry portals in real-time with improved visualization of critical structures located inside the pathway. To achieve this we used the following methods: (1) novel bone-only atlases were manually generated, (2) orbits and the center of the skull serve as features to quickly pre-align the patient’s scan with the atlas, (3) deformable registration technique was used for fine alignment, (4) surgical importance was assigned to each voxel according to a surgical dictionary, and (5) pre-defined transfer function was applied to the processed data to highlight important structures. The proposed idea was fully implemented as independent planning software and additional data are used for verification and validation. The experimental results show: (1) the proposed methods provided greatly improved planning efficiency while optimal surgical plans were successfully achieved, (2) the proposed methods successfully highlighted important structures and facilitated planning, (3) the proposed methods require shorter processing time than classical segmentation algorithms, and (4) these methods can be used to improve surgical safety for surgical robots.