David C. Eland

The virtual haptic back for palpatory training

This paper discusses the Ohio University Virtual Haptic Back (VHB) project, including objectives, implementation, and initial evaluations. Haptics is the science of human tactile sensation and a haptic interface provides force and touch feedback to the user from virtual reality. Our multimodal VHB simulation combines high-fidelity computer graphics with haptic feedback and aural feedback to augment training in palpatory diagnosis in osteopathic medicine, plus related training applications in physical therapy, massage therapy, chiropractic therapy, and other tactile fields. We use the PHANToM haptic interface to provide position interactions by the trainee, with accompanying force feedback to simulate the back of a live human subject in real-time. Our simulation is intended to add a measurable, repeatable component of science to the art of palpatory diagnosis. Based on our experiences in the lab to date, we believe that haptics-augmented computer models have great potential for improving training in the future, for various tactile applications. Our main project goals are to: 1. Provide a novel tool for palpatory diagnosis training; and 2. Improve the state-of-the-art in haptics and graphics applied to virtual anatomy.

The virtual haptic back: A simulation for training in palpatory diagnosis

BackgroundModels and simulations are finding increased roles in medical education. The Virtual Haptic Back (VHB) is a virtual reality simulation of the mechanical properties of the human back designed as an aid to teaching clinical palpatory diagnosis.MethodsEighty-nine first year medical students of the Ohio University College of Osteopathic Medicine carried out six, 15-minute practice sessions with the VHB, plus tests before and after the sessions in order to monitor progress in identifying regions of simulated abnormal tissue compliance. Students palpated with two digits, fingers or thumbs, by placing them in gimbaled thimbles at the ends of PHANToM 3.0® haptic interface arms. The interface simulated the contours and compliance of the back surface by the action of electric motors. The motors limited the compression of the virtual tissues induced by the palpating fingers, by generating counterforces. Users could see the position of their fingers with respect to the back on a video monitor just behind the plane of the haptic back. The abnormal region varied randomly among 12 locations between trials. During the practice sessions student users received immediate feedback following each trial, indicating either a correct choice or the actual location of the abnormality if an incorrect choice had been made. This allowed the user to feel the actual abnormality before going on to the next trial. Changes in accuracy, speed and Weber fraction across practice sessions were analyzed using a repeated measures analysis of variance.ResultsStudents improved in accuracy and speed of diagnosis with practice. The smallest difference in simulated tissue compliance users were able to detect improved from 28% (SD = 9.5%) to 14% (SD = 4.4%) during the practice sessions while average detection time decreased from 39 (SD = 19.8) to 17 (SD = 11.7) seconds. When asked in anonymous evaluation questionnaires if they judged the VHB practice to be helpful to them in the clinical palpation and manual medicine laboratory, 41% said yes, 51% said maybe, and 8% said no.ConclusionThe VHB has potential value as a teaching aid for students in the initial phases of learning palpatory diagnosis.

Muscle functional magnetic resonance imaging and acute low back pain: a pilot study to characterize lumbar muscle activity asymmetries and examine the effects of osteopathic manipulative treatment

BackgroundMuscle functional magnetic resonance imaging (mfMRI) measures transverse relaxation time (T2), and allows for determination of the spatial pattern of muscle activation. The purposes of this pilot study were to examine whether MRI-derived T2 or side-to-side differences in T2 (asymmetries) differ in low back muscles between subjects with acute low back pain (LBP) compared to asymptomatic controls, and to determine if a single osteopathic manipulative treatment (OMT) session alters these T2 properties immediately and 48-hours after treatment.MethodsSubjects with non-specific acute LBP (mean score on 1-10 visual analog score = 3.02 ± 2.81) and asymptomatic controls (n = 9/group) underwent an MRI, and subsequently the LBP subjects received OMT and then underwent another MRI. The LBP subjects reported back for an additional MRI 48-hours following their initial visit. T2 and T2 asymmetry were calculated from regions of interest for the psoas, quadratus lumborum (QL), multifidus, and iliocostalis lumborum/longissimus thoracis (IL/LT) muscles.ResultsNo differences were observed between the groups when T2 was averaged for the left and right side muscles. However, the QL displayed a significantly greater T2 asymmetry in LBP subjects when compared to controls (29.1 ± 4.3 vs. 15.9 ± 4.1%; p = 0.05). The psoas muscle also displayed a relatively large, albeit non-significant, mean difference (22.7 ± 6.9 vs. 9.5 ± 2.8%; p = 0.11). In the subjects with LBP, psoas T2 asymmetry was significantly reduced immediately following OMT (25.3 ± 6.9 to 6.1 ± 1.8%, p = 0.05), and the change in LBP immediately following OMT was correlated with the change in psoas T2 asymmetry (r = 0.75, p = 0.02).ConclusionCollectively, this pilot work demonstrates the feasibility of mfMRI for quantification and localization of muscle abnormalities in patients with acute low back pain. Additionally, this pilot work provides insight into the mechanistic actions of OMT during acute LBP, as it suggests that it may attenuate muscle activity asymmetries of some of the intrinsic low back muscles.

Self-efficacy in mastery learning to apply a therapeutic psychomotor skill.

This study assessed changes in Self-efficacy scores produced by each of the four steps of instruction used to teach students a therapeutic psychomotor skill used by osteopathic physicians. Volunteering subjects were an entire class of 83 first-year osteopathic medical students (40 men, 43 women, M age = 25.1 yr.). Self-reported Self-efficacy to perform the skill was sampled: (1) after an instructors demonstration of the skill during a laboratory session, (2) after paired students practiced during the laboratory session, (3) after independent self-paced practice outside class using an instructional handout and videotape, and (4) after receiving individualized feedback on skill performance from an instructor acting as the “patient.” The first two steps, representing typical skill instruction, produced mean Self-efficacy scores of 18% and 30%, respectively. On the last two steps, added to implement mastery learning, mean Self-efficacy scores increased to 75% and 85%, respectively. The instructors confirmed that all students mastered performance of the skill. Mastery learning was effective in developing both the therapeutic skill and high Self-efficacy to utilize the skill.

The Virtual Haptic Back (VHB): A Virtual Reality Simulation of the Human Back for Palpatory Diagnostic Training

The Virtual Haptic Back (VHB) is designed as an aid to teaching medical palpatory diagnosis. It uses two PHANToM 3.0 haptic interfaces (SensAble Technologies, Inc.), permitting palpation by force feedback with two fingers of a life-sized virtual human back. A graphics image of the back is displayed on a monitor a few inches behind the palpable back. Movement of back components, e.g., skin or underlying vertebrae, by exertion of palpatory force by the user is reflected graphically. Mechanical properties of the back, e.g., spring constants of the surface, are chosen based on feedback from physicians experienced in palpatory diagnosis. Although subjective evaluation of the VHB by 81 users over 2 years is positive, results have not yet shown students being trained in palpatory diagnosis to perform better than controls subjects. Results guide modifications of the haptic model itself and of the user tasks employed during testing.

The Virtual Haptic Back: Detection of Compliance Differences

The ability of human subjects to distinguish small compliance differences in adjacent regions was tested with the Virtual Haptic Back (VHB), a simulation of human backs designed to aid in teaching medical palpatory diagnosis. The VHB uses two PHANToM 3.0 haptic interfaces (SensAble Technologies, Inc.). The contours and compliance properties of the backs are represented graphically and haptically. Medical students practiced 8 times over 2 weeks on the VHB, finding regions of altered compliance, the locations of which varied randomly. Baseline compliance was 2.52 mm/N; compliance in the abnormal regions ranged from 2.45 to 0.97 mm/N. Following the practice session the threshold of detection is 2.25 mm/N, an 11% difference from baseline.