Mixed Reality Anatomy Using Microsoft HoloLens and Cadaveric Dissection: A Comparative Effectiveness Study.

PURPOSE: As the amount of curricular material required of medical students increases, less time is available for anatomy; thus, methods to teach anatomy more efficiently and effectively are necessary. In this randomized controlled trial, we looked at the effectiveness of a mixed reality (MR) device to teach musculoskeletal anatomy to medical students compared with traditional cadaveric dissection. METHOD: Participating students were divided into three cohorts. Cohort 1 first studied upper limb anatomy in MR followed by lower limb anatomy through cadaveric dissection. Cohort 2 studied upper limb anatomy with cadaveric dissection followed by lower limb anatomy in MR. After the six sessions, a third cohort of 33 students who never received any teaching in MR was recruited to participate in the final practical exams as a control group. All 64 students completed two practical exams with equivalent content, one in the cadaver lab and one using MR. RESULTS: The average scores were 73.8% + 12.3 on the cadaver exam and 74.2% + 13.0 in MR. There is no statistical difference between these scores (p > 0.05). A correlation was found between the MR practical exam and cadaver practical exam scores (r = 0.74, p < 0.01) across all students. CONCLUSIONS: To our knowledge, this study marks the first time that MR was compared with traditional anatomy learning modalities in a multi-session, group course. Our results clearly indicate that medical students, regardless of the study modality, performed similarly on the MR and the cadaver practical exams.

Plasma instability of a vacuum arc centrifuge.

Ever since conception of the vacuum arc centrifuge in 1980, periodic fluctuations in the ion saturation current and floating potential have been observed in Langmuir probe measurements in the rotation region of a vacuum arc centrifuge. In this work we develop a linearized theoretical model to describe a range of instabilities in the vacuum arc centrifuge plasma column, and then test the validity of the description through comparison with experiment. We conclude that the observed instability is a "universal" instability, driven by the density gradient, in a plasma with finite conductivity.

Psychological factors and hyperemesis gravidarum.

Hyperemesis gravidarum (HG) is a condition of severe, intractable nausea and vomiting during pregnancy. It has long been held that HG is a psychosomatic illness reflective of a long-term psychological trait, that is, conversion disorder. We investigated this possibility by conducting a two-phase study: (1) a comparison of women with (n = 9) and without (n = 10) HG during pregnancy and (2) a comparison of nonpregnant women who did (n = 10) and did not (n = 12) have HG during their most recent pregnancies. The pattern of findings differed between experiments 1 and 2. During pregnancy, women with HG scored significantly higher on three scales associated with conversion disorder (all p values <0.01) than did women without HG. There were no significant differences between HG subjects and controls after pregnancy. We find no support for the theory that HG is a psychosomatic condition. Rather, it appears to be a complex interaction of biological, psychological, and sociocultural factors.

Regional cerebral volume measurements in late-life depression: relationship to clinical correlates, neuropsychological impairment and response to treatment.

BACKGROUND: Elderly people who develop depression have demonstrable changes in cerebral structure but little is known of the relationship between regional cerebral volumes, treatment response and cognitive impairment. METHOD: Forty-four patients with major depression diagnosed according to DSM-IIIR criteria underwent magnetic resonance imaging and regional cerebral volumes were quantified using multispectral analysis. Response to antidepressant treatment was assessed prospectively and a neuropsychological test battery was administered. RESULTS: There was a trend for smaller fronto-temporal volumes in the treatment-resistant patients. Impaired immediate working memory was linked with reduced frontal and parietal lobe volume and impaired short-term memory functioning was associated with reduced temporal lobe volume. Ventricular enlargement was associated with prior administration of electro-convulsive therapy, poor physical health and later age at onset of first episode of depression. CONCLUSION: In late-life depression, brain changes should not preclude vigorous antidepressant treatment. Regional cerebral volume changes may be a complication of poor physical health and are associated with memory dysfunction even upon recovery from depression.

The prognostic significance of abnormalities seen on magnetic resonance imaging in late life depression: clinical outcome, mortality and progression to dementia at three years.

OBJECTIVE: To study the course of depressive symptoms over 3 years, rate of dementia and mortality in relation to baseline neuroradiological abnormalities. DESIGN: Retrospective casenote analysis of 38 patients (of 44) who had a Magnetic Resonance Imaging (MRI) scan 3 years earlier. Twenty-two patients also received a detailed interview. RESULTS: Overall outcome was good for around two-thirds of the sample. Poorer clinical course was associated with lesions in pons and more than five Virchow Robins spaces in the corona radiata. Pontine raphe lesions and confluent periventricular lesions were associated with later dementia and with reduced survival from cardiovascular death. Males had more recurrences and a reduced survival. CONCLUSIONS: MRI lesions influence outcome, mortality and the onset of dementia. However, because they are quite common in elderly depressed patients they have limited utility on their own as predictors of outcome. The association of periventricular lesions with dementia is a new finding, and suggests that the site and type of lesions may be as important than the quality of them.

First rib metamorphosis: its possible utility for human age-at-death estimation.

Human first ribs demonstrate predictable, sequential changes in shape, size, and texture with increasing age, and thus, can be used as an indicator of age at death. Metamorphosis of the first rib's head, tubercle, and costal face was documented in a cross-sectional sample of preadult and adult first ribs of known age at death from the Hamann-Todd skeletal collection (Cleveland Museum of Natural History, Cleveland, Ohio). Blind tests of the usefulness of the first rib as an age indicator were conducted, including tabulation of intraobserver and interobserver inaccuracies and biases. First rib age estimates show inaccuracies and biases by decade comparable to those generated by other aging techniques. Indeed, the first rib method is useful as an isolated age indicator. When used in conjunction with other age indicators, the first rib improves the quality of summary age assessments.

Single-shot echo-planar imaging of multiple sclerosis: effects of varying echo time.

Our aim was to determine the relative merits of short and long echo times (TE) with single-shot echo-planar imaging for imaging cerebral lesions such as multiple sclerosis. We examined seven patients with clinically definite multiple sclerosis were imaged at 1.5 T. Patients were scanned with spinecho, single-shot echo-planar imaging, using TEs of 45, 75, 105, and 135 ms. Region of interest (ROI) measurements were performed on 36 lesions at or above the level of the corona radiata. The mean image contrast (IC) was highest (231.1) for a TE of 45 ms, followed by 75 ms (218.9), 105 ms (217.9), and 135 ms (191.6). When mean contrast-to-noise ratios (C/N) were compared, the value was again highest (29.7) for TE 45 ms, followed by 75 ms (28.9), 105 ms (28.5), and 135 ms (26.3). In a lesion-by-lesion comparison, TE 45 ms had the highest IC and C/N in the largest number of cases (50 % and 47.2 %, respectively). IC and C/N for TE 45 ms were superior to those of 75 ms in 64% and 58%, respectively. These results support the use of relatively short TEs for single-shot echo-planar imaging in the setting of cerebral lesions such as multiple sclerosis.

A radiographic study of the development of the human mandibular dentition.

This paper presents new data on the absolute timing of the growth of the mandibular permanent teeth, with an emphasis on the timing of the completion of the enamel crown. Two collections of cranio-dental radiographs were analyzed: (1) 267 juveniles from a contemporary pediatric dental clinic (Case Western Reserve University School of Dentistry, Cleveland, Ohio), and (2) 36 individuals sampled longitudinally from the Bolton-Brush Growth Study Center. The ages of the individuals span from three months to 18 years of age and the study includes both cross-sectional and longitudinal data. Comparisons of the ages of attainment of the Cleveland samples with other schedules of dental development are made. The relative contribution of the multiple underlying sources of variation producing the differences between the radiographically based developmental schedules remain elusive.

1997 IPA/Bayer Research Awards in Psychogeriatrics. Subcortical hyperintensities in late-life depression: acute response to treatment and neuropsychological impairment.

Subcortical hyperintensities are easily visualized areas of signal abnormality that are seen on T2-weighted magnetic resonance imaging (MRI). Characteristically they occur in the white matter of the brain and are more common in elderly people. In depression, little is known of the clinical significance of subcortical hyperintensities or their contribution to the prognosis. Fifty-eight consecutive patients with DSM-III-R depression and an age range of 65 to 85 years were prospectively collected from an old-age psychiatry service. Response to treatment was assessed with a clinical global outcome measure. A neuropsychology battery was completed on all patients after treatment. Forty-four patients completed MRI scanning. The scans were scored using a regional rating system for hyperintensities. Forty-eight percent of patients had a favorable response to treatment on the clinical global outcome scale. Poor outcome was associated with female sex (p = .07), poor physical health (p = .040), diabetes (p = .018), psychosis (p = .026), and an early age at onset of first episode of depression (p = .036). Even after adjustment for confounding effects, there were significant neuropsychological associations with the regional hyperintensities. Distribution in the periventricular area correlated with delayed recall after distraction (p = .025), and punctate lesions in the basal ganglia correlated with impaired category production (p = .020). Pontine reticular formation hyperintensities were related to impaired psychomotor speed (p = .04). Location in the frontal deep-white matter (p = .024), basal ganglia (p = .03), and pontine reticular formation (p = .02) was associated with a poor acute response to treatment. However, the response to treatment was not related to total cerebral white-matter hyperintensity load. A logistic regression equation included all the significant prognostic features and found four independent predictors of poor outcome: More than five punctate lesions of the basal ganglia, diabetes, lower mean arterial pressure, and hyperintensity of the pontine reticular formation significantly predicted outcome. These four factors correctly predicted 95.6% of patients with a poor outcome and 85.7% with a favorable outcome. In late-life depression, subcortical hyperintensities are common. Lesions in the cerebral white matter are predominantly associated with memory disturbance, and those in deeper infratentorial areas, with psychomotor slowing and executive deficits. Total white-matter load has no prognostic value, and although some subcortical regions are associated with poor response, individually they have little specificity. However, a combination of involvement in three areas (basal ganglia, pons, and frontal lobe) is clinically relevant and predicts outcome with great accuracy (91%). Patients with lesions in the basal ganglia and deep white matter had an especially poor response to pharmacotherapy.

Comparison of diaphyseal growth between the Libben Population and the Hamann-Todd chimpanzee sample.

The differences in limb lengths and proportions between humans and chimpanzees are widely known. Humans have relatively shorter forelimbs and longer hind limbs than chimpanzees. Humans have a longer period of long bone formation than chimpanzees. Recent advances in estimating age-at-death in chimpanzees from their dentition have allowed us to reexamine long bone growth in chimpanzees using their skeletal remains and compare it with similar data for humans. A chronological normalization procedure allowing direct interspecific comparison of long bone growth is presented. The preadult chimpanzee sample (n = 43) is from the Hamann-Todd Osteological Collection from the Cleveland Museum of Natural History. All human specimens (n = 202) are from the late Woodland Libben Population currently housed at Kent State University. Relying on these cross-sectional data, we conclude that both species elongate their femora at similar absolute (length per unit time) but different relative (length relative to normalized dental age) rates. The species differ in the absolute growth rate of the humerus but share a common normalized rate of growth. Forelimb segment proportion differences between species are due to differential elongation rates of the segments. Hind limb diaphyseal proportions are the same in both species, which suggests that changes in segment length are proportional. Therefore, alternative developmental mechanisms exist in these closely related species which can produce changes in limb length.

Independent test of the fourth rib aging technique.

The sternal surface of the 4th rib has been suggested as a useful predictor of adult age-at-death (Iscan et al.: Journal of Forensic Sciences 29:1094-1104, 1984; American Journal of Physical Anthropology 65:147-156, 1984). We tested its ability to do so in two tests. In the first, we developed a method of seriation and target age assignment for the 4th rib so that inaccuracy and bias of the method could be assessed by decade. We found that the 4th rib shows characteristic changes in morphology with age and can be included in multifactorial age estimates. In the second test, we applied the phase method developed by Iscan et al. (Journal of Forensic Sciences 29:1094-1104, 1984). The results of our three judges were generally similar to those reported by Iscan and Loth (Journal of Forensic Sciences 31:122-132, 1986). Measures of race differences in 4th rib morphology were included in both tests. Americans of African descent (black) showed a non-significant trend for the rib changes to be delayed compared to Americans of European descent (white). This is in contrast to the work of Iscan et al., which predicted that blacks would show a tendency toward accelerated rib changes compared to whites, especially after the early 30s (phases 5-7) (Iscan et al.: Journal of Forensic Sciences 32(2):452-466, 1987).

Test of the multifactorial aging method using skeletons with known ages-at-death from the Grant Collection.

The multifactorial aging method has been shown to be a highly reliable method of skeletal aging because it incorporates age information from as many age indicators as are available for each skeleton (Lovejoy et al.; Am. J. Phys. Anthropol. 68:1-14, 1985). The present study was a blind test to assess its accuracy on a skeletal sample composed of 55 individuals with verified death certificates (Grant Collection, University of Toronto). Three authors (C.O.L., M.E.B., and K.F.R.), with no access to the death certificate ages, independently seriated and aged the sample using three to four criteria: auricular surface, pubic symphysis, and radiographs of the proximal femur and clavicle. Summary ages were then calculated for each individual in the sample. The authors' independent summary age estimates showed strong correlations with one another (r = 0.84-0.89). Multifactorial age estimates correlated better with real age than did those from any single indicator used. The mean error (averaging 8.7 years) for summary age was at least 1 year less than that for any single indicator. Average bias ranged from -0.7 (underage) to 1.4 (overage) years. These results indicate that utilization of several age indicators, weighted according to their reliability, helps control for variation in the changes that occur with age in any single morphological indicator. This method may therefore be considered one of the most accurate available for the determination of skeletal age-at-death, particularly for paleodemographic analysis.

Further evidence on relative dental maturation and somatic developmental rate in hominoids.

New data on hominoid dental development are presented. Individual bivariate pairings of all mandibular teeth were made for African apes and humans. Data were analyzed with a full linear regression model. No statistically significant differences were found among apes, although a consistent pattern of earlier incisal development was observed in Pan relative to Gorilla. This is concordant with an earlier fusion of the premaxillary:maxillary suture in Pan. Only one tooth pair differed significantly by sex among apes. Two biologically distinct human samples (Libben and Hamann-Todd), although assessed differently (extraction and radiography) yielded virtually identical results. Humans differ from apes only by earlier relative calcification of their anterior teeth. This can be viewed as a consequence of reduced facial prognathism and a shift in hominid canine function.