Bertram Unger

Generation of a 3D printed temporal bone model with internal fidelity and validation of the mechanical construct.

Objective To generate a rapid-prototyped temporal bone model from computed tomography (CT) data with a specific focus on internal anatomic fidelity. Study Design Research ethics board-approved prospective cohort study. Setting Current iterations of a rapid-prototyped temporal bone model are complicated by absent void spaces and inconsistent bone density due to limited infiltrant exposure. The creation of a high-fidelity model allows surgical trainees to practice in a standardized and reproducible training environment. This learning paradigm will significantly augment resident understanding of surgical approaches and techniques to prevent adverse outcomes. Subjects and Methods We describe a technique for generating internally accurate rapid-prototyped anatomical models with solid and hollow structures, including void spaces. The novel slicing algorithm digitally deconstructs a model into segments and permits removal of extraneous print material and allows infiltrant penetration of the entire bone structure. Precise reassembly is facilitated by digitally generated fiducials. Infiltrant of choice was determined by expert assessment and subjected to objective mechanical property assessment with comparison to cadaveric sheep bone. Results The printed bone models are highly realistic. Void space representation was excellent with 88% concordance between cadaveric bone and the resultant rapid-prototyped temporal bone model. Ultimately, cyanoacrylate with hydroquinone was determined to be the most appropriate infiltrant for both cortical and trabecular simulation. The mechanical properties of all tested infiltrants were similar to real bone. Conclusion This model serves as an excellent replica of a human temporal bone for training and preoperative surgical rehearsal and can be dissected in a true-to-life fashion.

Comparison of cadaveric and isomorphic three-dimensional printed models in temporal bone education.

Current three‐dimensional (3D) printed simulations are complicated by insufficient void spaces and inconsistent density. We describe a novel simulation with focus on internal anatomic fidelity and evaluate against template/identical cadaveric education.

Ultrasound assessment of optic nerve sheath diameter in healthy volunteers.

BACKGROUND Ultrasound assessment of optic nerve sheath diameter (ONSD) has been suggested as a non-invasive measure of intracranial pressure. Numerous small studies suggest its validity; however, discrepancy exists around normal values for ONSD. In this study we sought to define a normal value range for ONSD in a population of healthy adult volunteers. METHODS ONSD was measured in healthy adult volunteers and a normal range was defined using descriptive statistics. A regression analysis was used to determine relationship between ONSD measurements and sex, age, height and weight. RESULTS One hundred twenty adults were recruited (age 18-65 [mean 29.3]) with 55 male and 65 female subjects. Mean ONSD was 3.68 mm (95% confidence interval [CI], 2.85-4.40). Upon regression analysis, mean ONSD did not vary with age, weight, or height but did vary with sex. Mean ONSD measurements for men were 3.78 mm (95% CI, 3.23-4.48) compared with 3.60 mm (95% CI, 2.83-4.11) for women. CONCLUSION This study has defined the range of ONSD in a healthy cohort of volunteers. The lack of relationship to age, weight and height is similar to other studies but this is the first study to find a difference depending on sex suggesting the possible need for separate reference ranges for men and women.

Roughness Perception in Virtual Textures

Haptic devices allow the production of virtual textured surfaces for psychophysical experiments. Some studies have shown inconsistencies between virtual and real textures with respect to their psychophysical functions for roughness, leading to speculation that virtual textures differ in some way from real ones. We have determined the psychophysical function for roughness using textures rendered with a high-fidelity magnetic levitation haptic device. A constraint surface algorithm was used to simulate the motion of a spherical probe over trapezoidal gratings and randomly dithered cones. The shape of the psychophysical functions for roughness is consistent between subjects but varies with changes in texture and probe geometry. For dithered cones, inverted “U”-shaped functions were found nearly identical, in maxima and curvature, to those in the literature for real textures with similar geometry.

A Unique Model for Ultrasound Assessment of Optic Nerve Sheath Diameter

BACKGROUND Ultrasonic assessment of optic nerve sheath diameter (ONSD) as a non-invasive measure of intracranial pressure (ICP) has been evaluated in the literature as a potential valid technique for rapid ICP estimation in the absence of invasive intracranial monitoring. The technique can be challenging to perform and little literature exists surrounding intra-operator variability. OBJECTIVES In this study we describe the creation of a novel model of ONSD to be utilized in ultrasound training of this technique. We demonstrate the realistic ultrasonographic images created utilizing this novel model. METHODS We designed ocular models composed of gelatin spheres and variable three dimensional printed cylinders, which simulate the globe of the eye and variable ONSDs respectively. These models were suspended in a gelatin background and ultrasound of the ONSD was conducted using standard techniques described in the literature. RESULTS This model produces clear and accurate representation of ONSD that closely mimics in vivo images. It is affordable and easy to produce in large quantities, portending its use in an educational environment. CONCLUSIONS Utilizing the standard linear array ultrasound probe for ONSD measurements in our model provided realistic images comparable to in vivo. This provides an affordable and exciting means to test intra- and inter- operator variability in a standardized environment. Knowing this, we can further apply this novel model of ONSD to ultrasound teaching and training courses with confidence in its ability and the techniques ability to produce consistent results.

End User Comparison of Anatomically Matched 3-Dimensional Printed and Virtual Haptic Temporal Bone Simulation: A Pilot Study.

Objective Simulation has assumed a prominent role in education. It is important to explore the effectiveness of different modalities. In this article, we directly compare surgical resident impression of 2 distinct temporal bone simulations (physical and haptic). Study Design Research Ethics Board–approved prospective cohort study. Setting A haptic voxel-based virtual model (VM) and a physical 3-dimensional printed temporal bone model (PBM) were developed. Participants rated each construct on a number of parameters and performed a direct comparison of the simulations using a survey instrument that employed a 7-point Likert scale and rank lists. Subjects and Methods Ten otolaryngology residents dissected anatomically identical, matched physical and virtual models. Data for both simulations originated from 10 unique cadaveric micro–computed tomography images. Results Subjects rated the PBM drill quality as being more similar to cadaveric temporal bone than the VM (cortical bone mean: 5.5 vs 3.2, P = .011; trabecular bone mean: 5.2 vs 2.8, P = .004) and with better air cell system representation (mean: 5.4 vs 4.5, P = .003). Subjects strongly agreed that both simulations are effective educational tools, but they rated the PBM higher (mean: 6.7 vs 5.4, P = .019). Notably, subjects agreed that both modalities should be integrated into training, but they were more favorably inclined toward the PBM (mean: 7.0 vs 5.5, P = .002). In direct comparison, the PBM was the preferred simulation in 7 of 9 educational domains. Conclusions Appraisal of a PBM and a VM found both to have perceived educational benefit. However, the PBM was considered to have more realistic physical properties and was considered the preferred training instrument.

Validation of the quality of ultrasound imaging and competence (QUICk) score as an objective assessment tool for the FAST examination.

BACKGROUND The Focused Assessment with Sonography for Trauma (FAST) examination has become a valuable tool in trauma resuscitation. Despite the widespread use of FAST training among traumatologists, no evidence-based guidelines exist to support optimal training requirements or to provide quantitative objective assessments of imaging capabilities. Both Task-Specific Checklist (TSC) and Global Rating Scale (GRS) have been validated as objective skill assessment tools; we developed both types of scoring checklist and assessed them for construct validity with the FAST examination. METHODS Two scoring checklists, collectively termed the Quality of Ultrasound Imaging and Competence (QUICk) Score, were developed and subjected to a modified Delphi consensus process. Two cohorts of 12 novice and 12 expert sonographers performed the FAST examination and were evaluated by two experts according to the QUICk model. Total scores as well as anatomic subsets were compared via comparison of means, and logistic regression modeling was used to determine sensitivity and specificity. RESULTS Experts achieved significantly higher total scores than novices on both scoring systems (17.2 vs. 11.1 of 24, p < 0.01 TSC, 29.8 vs. 18.4 of 40, p < 0.01 GRS). Sensitivity (85.7% TSC, 92.9% GRS) and specificity (75.0% TSC, 91.7% GRS) as well as area under the receiver operating characteristic curve (89.9% TSC, 97.6% GRS) were consistent with a highly discriminant tool. CONCLUSION The QUICk Score is the first validated objective tool for assessment of the quality of FAST examination imaging. Use of this tool may be instrumental in developing an evidence-based minimum-performance standard and for assessing quality-improvement modifications in FAST examination training.

Validation of hand motion analysis as an objective assessment tool for the Focused Assessment with Sonography for Trauma examination.

BACKGROUND Point-of-care ultrasonography is a standard part of trauma assessments, but there are no objective tools to assess proficiency and ensure high-quality examinations. Hand motion analysis (HMA) has been validated as a measure of surgical skill but has not previously been applied to ultrasonography. HMA was assessed for construct validity in Focused Assessment with Sonography for Trauma (FAST) performance. METHODS Two cohorts of 12 expert and 12 novice ultrasonographers performed a FAST examination on a healthy volunteer. Hand motions were recorded with the trakSTAR 3D electromagnetic motion-tracking device (Ascension Technology) and analyzed using our custom-designed Motion Analysis and Recording System (MARS) software. Data were recorded at 240 Hz. Outcomes included time of examination, number of movements, and path length. RESULTS Time of examination was not different between cohorts (expert, 345.9 seconds; novice, 475.7 seconds; p = 0.12). Total path length of travel was shorter, and the number of discreet movements was less in the expert cohort for the left-hand (18.52 m vs. 28.01 m, p = 0.03, and 109.5 vs. 193.9, p = 0.027, respectively) and the right-hand performance (14.25 m vs. 32.09 m, p < 0.01, and 153.5 vs. 258.5, p = 0.03, respectively) versus the novice cohort. Both total path length traveled and total number of discreet movements were associated with expertise level in logistic regression modeling with areas under the receiver operating characteristic curves of 0.8269 and 0.8205, respectively. CONCLUSION This is the first study in the medical literature showing HMA as an objective, valid measure of FAST imaging performance. These objective, automated metrics can function as an adjunct measure to assess FAST performance as well as follow progress of and provide feedback to learners to improve future performances. LEVEL OF EVIDENCE A “diagnostic criteria”–style test where the “diagnosis” is a determination of competence in a care provider, level II.

The effect of blocked versus random task practice schedules on the acquisition and retention of surgical skills

BACKGROUND When learning multiple tasks, blocked or random training schedules may be used. We assessed the effects of blocked and random schedules on the acquisition and retention of laparoscopic skills. METHODS Thirty-six laparoscopic novices were randomized to practice laparoscopic tasks using blocked, random, or no additional training. Participants performed immediate post-tests, followed by retention tests 6 weeks later. Outcomes included previously validated Fundamentals of Laparoscopic Surgery (FLS) and hand-motion efficiency scores. RESULTS Both blocked and random groups had significantly higher FLS and hand-motion efficiency scores over baseline on post-tests for each task (P < .05) and higher overall FLS scores than controls on retention tests (P < .01). No difference was seen between the blocked and random groups in the amount of skill acquired or skill retained. CONCLUSIONS Both blocked and random training schedules can be considered as valid training options to allow programs and learners to tailor training to their individual needs.

Comparison of cadaveric and isomorphic virtual haptic simulation in temporal bone training

BackgroundVirtual surgery may improve learning and provides an opportunity for pre-operative surgical rehearsal. We describe a novel haptic temporal bone simulator specifically developed for multicore processing and improved visual realism. A position locking algorithm for enhanced drill-bone interaction and haptic fidelity is further employed. The simulation construct is evaluated against cadaveric education.MethodsA voxel-based simulator was designed for multicore architecture employing Marching Cubes and Laplacian smoothing to perform real-time haptic and graphic rendering of virtual bone.Ten Otolaryngology trainees dissected a cadaveric temporal bone (CTB) followed by a virtual isomorphic haptic model (VM) based on derivative microCT data. Participants rated 1) physical characteristics, 2) specific anatomic constructs, 3) usefulness in skill development and 4) perceived educational value. The survey instrument employed a Likert scale (1-7).ResultsResidents were equivocal about the physical properties of the VM, as cortical (3.2 ± 2.0) and trabecular (2.8 ± 1.6) bone drilling character was appraised as dissimilar to CTB. Overall similarity to cadaveric training was moderate (3.5 ± 1.8). Residents generally felt the VM was beneficial in skill development, rating it highest for translabyrinthine skull-base approaches (5.2 ± 1.3). The VM was considered an effective (5.4 ± 1.5) and accurate (5.7 ± 1.4) training tool which should be integrated into resident education (5.5 ± 1.4). The VM was thought to improve performance (5.3 ± 1.8) and confidence (5.3 ± 1.9) and was highly rated for anatomic learning (6.1 ± 1.9).ConclusionStudy participants found the VM to be a beneficial and effective platform for learning temporal bone anatomy and surgical techniques. They identify some concern with limited physical realism likely owing to the haptic device interface. This study is the first to compare isomorphic simulation in education. This significantly removes possible confounding features as the haptic simulation was based on derivative imaging.