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PubMed2000

An appraisal of medical students' reflection-in-learning.

INTRODUCTION: How do students reflect as they strive for some control of learning early in their clinical activities? The purpose of this study was to examine the reflection-in-learning profile of medical students as they started their clinical apprenticeship. METHODS: A measure of reflection-in-learning was used to appraise the level and direction of change of reflection in relation to a course experience. The study involved 103 medical students of both sexes who were beginning clinical activities. Assessments of self-regulation of learning, of the meaningfulness of the learning experience, and of diagnostic thinking were also obtained. RESULTS: The results showed that 81% of the students had an increase in scores for reflection-in-learning between the beginning and the end of a course. At the end of the course, the level of reflection-in-learning was significantly associated with self-perceived competence for self-regulated learning and with the meaningfulness of the learning experience. In the following term, students who had high reflection-in-learning scores at the end of the course had higher grade-point averages and greater self-reported diagnostic ability in comparison with those with low scores. CONCLUSIONS: There was some evidence of an improved quality of reflection as the students strive for some control of learning. Overall, the findings support the idea that a greater effort at reflection is associated with a more positive learning experience. They also suggest that reflection-in-learning is related to readiness for self-regulation of learning and may be conducive to enhanced diagnostic ability. In conclusion, measuring reflection-in-learning may be a useful tool in the appraisal of medical students' learning profiles.

Attitude↗
PubMed1998

Synaptic facilitation by reflected action potentials: enhancement of transmission when nerve impulses reverse direction at axon branch points.

A rapid, reversible enhancement of synaptic transmission from a sensory neuron is reported and explained by impulses that reverse direction, or reflect, at axon branch points. In leech mechanosensory neurons, where one can detect reflection because it is possible simultaneously to study electrical activity in separate branches, action potentials reflected from branch points within the central nervous system under physiological conditions. Synapses adjacent to these branch points were activated twice in rapid succession, first by an impulse arriving from the periphery and then by its reflection. This fast double-firing facilitated synaptic transmission, increasing it to more than twice its normal level. Reflection occurred within a range of resting membrane potentials, and electrical activity produced by mechanical stimulation changed membrane potential so as to produce and cease reflection. A compartmental model was used to investigate how branch-point morphology and electrical activity contribute to produce reflection. The model shows that mechanisms that hyperpolarize the membrane so as to impair action potential propagation can increase the range of structures that can produce reflection. This suggests that reflection is more likely to occur in other structures where impulses fail, such as in axons and dendrites in the mammalian brain. In leech sensory neurons, reflection increased transmission from central synapses only in those axon branches that innervate the edges of the receptive field in the skin, thereby sharpening spatial contrast. Reflection thus allows a neuron to amplify synaptic transmission from a selected group of its branches in a way that can be regulated by electrical activity.

Action Potentials↗
PubMed2001

Helping learners become reflective practitioners.

CONTEXT: In too many schools in the health professions, students are given little or no opportunities to reflect systematically on their simulated or real experiences practicing the skills they need as clinicians (e.g. eliciting information and solving problems). In addition, they are given little or no help in learning the skills that are central to being reflective practitioners. RATIONALE: Reflecting alone or with the help of educators or others, students and residents can learn to identify and build on their existing knowledge, identify their biases and assumptions, integrate new understandings, and formulate generalizations that will enable them to make positive changes in what they do in future situations. Put another way, they can derive lessons from their experiences that will enhance their skills and enable them to provide better patient care. When learners reflect aloud on their insights and their strengths and deficiencies before their teachers give them advice or feedback, learners can make their own discoveries and have the dignity of identifying what they need to work on. The learners' self-disclosures provide educators with "diagnostic" information that can enable them to tailor their teaching to the learners' interests and needs. SUGGESTIONS: Educators can help learners become reflective practitioners by taking such steps as ensuring learners have worthy experiences on which to reflect; observing learners in action; scheduling times and places for reflection; building trust; determining the learners' prior experiences, comfort with, and attitudes toward reflection; ensuring learners understand the rationale and strategies for reflection; modeling reflection; clarifying the learning goals; encouraging learners to have questions to ask themselves; helping learners reflect on their thoughts, feelings, biases, and assumptions; helping learners consider other approaches; inviting learners to identify the lessons they've learned; and asking them to discuss how they intend to use these new understandings.

Journal Article↗
PubMed1981

Photoelectric plethysmography--some fundamental aspects of the reflection and transmission method.

In photoelectric plethysmography a distinction is made between the reflection methods. Uncertainties still exist, especially regarding the origin of the reflected signal: some investigators attach quantitative value to the amplitude of the plethysmogram. The various findings are reconsidered. Various fluids are pulsatingly pumped through an in vitro circuit. Flow, pressure and volume pulsations are measured, as is the total light intensity detected by a photoelectric plethysmograph with the small variations caused in it by the pulsations in flow. Both phase and amplitude of the resulting plethysmogram are studied and the results compared with those found in vivo at the fingers and auricles. In vitro, the variations in light reflection are in phase with the volume pulsations: this can only be ascribed to reflection by orienting erythrocytes. In vivo, however, the light reflection, like the light transmission, is in anti-phase with the volume excursions, thus eliminating the determinative effect of light reflection by orienting erythrocytes--the strong reflection from surrounding tissues completely dominates reflection from erythrocytes. Since erythrocytes also have absorptive properties, and the light reflection is in anti-phase with the volume excursions, it is concluded that this absorptivity can manifest itself over the strong reflection from surrounding tissue. In vivo, therefore, the reflection plethysmogram is, in principle, an absorption measurement. The relationship between intensity of detected light and resultant voltage may not be linear: this nonlinearity may not be neglected when amplitude changes are compared. Amplitude changes of different plethysmograms may only be compared quantitatively if there is no difference in their light-voltage relationship.

Blood Physiological Phenomena↗
PubMed2003

Tissue oxygenation and perfusion in inferior pedicle reduction mammaplasty by near-infrared reflection spectroscopy and color-coded duplex sonography.

Near-infrared reflection spectroscopy has been used in various experimental and clinical settings to investigate tissue perfusion and oxygenation noninvasively. Its application in plastic surgery has only recently been reported. The current study used near-infrared reflection spectroscopy to monitor cutaneous microcirculation in breast skin flaps after inferior pedicle reduction mammaplasty. Thirty patients underwent bilateral reduction mammaplasty by a modified Robbins technique. Near-infrared reflection spectroscopy measurements were performed preoperatively and postoperatively at several defined positions of the breast. The reflection spectroscopy system was capable of detecting absolute values of total hemoglobin in milligrams per milliliter of tissue and tissue hemoglobin oxygen saturation in percent. Color-coded duplex sonography was used to visualize nutrient vessels of the inferior dermoglandular pedicle and to measure systolic peak flow in the arteries supplying the nipple-areola complex. Reflection spectroscopy values were examined for changes during the postoperative course. Reflection spectroscopy and duplex sonography values were analyzed for differences between patients with normal and compromised skin flap perfusion and wound healing, which was assessed clinically and by ultrasound. Preoperative reflection spectroscopy values demonstrated local, regional, and interindividual variations. Postoperatively, characteristic changes of tissue hemoglobin oxygen saturation and total hemoglobin were observed in all patients during the 2-week follow-up. Reflection spectroscopy values differed significantly between breast and nipple-areola skin. Tissue hemoglobin oxygen saturation was significantly lower, and total hemoglobin significantly higher, in patients with impaired wound healing compared with patients having normal wound healing. However, systolic peak flow in arteries of the inferior dermoglandular pedicle did not reveal differences between patients with impaired or normal wound healing of the nipple-areola complex. Near-infrared reflection spectroscopy allows the detection of hemoglobin content and oxygenation in skin flaps. Changes in tissue hemoglobin oxygen saturation and total hemoglobin reflect hemodynamic changes in skin flaps during normal and pathological wound healing. Because of considerable intraindividual and interindividual variations, trend values seem to be superior to single measurements. Although in this study, near-infrared reflection spectroscopy was capable of distinguishing between normal and impaired perfusion in skin flaps in a clinical model, its future implication may be the early detection of vascular compromise in free flaps.

Adolescent↗
PubMed2006

Wave reflection effects in the central circulation of American alligators (Alligator mississippiensis): what the heart sees.

A large central compliance is thought to dominate the hemodynamics of all vertebrates except birds and mammals. Yet large crocodilians may adumbrate the avian and mammalian condition and set the stage for significant wave transmission (reflection) effects, with potentially detrimental impacts on cardiac performance. To investigate whether crocodilians exhibit wave reflection effects, pressures and flows were recorded from the right aorta, carotid artery, and femoral artery of six adult, anesthetized American alligators (Alligator mississippiensis) during control conditions and after experimentally induced vasodilation and constriction. Hallmarks of wave reflection phenomena were observed, including marked differences between the measured profiles for flow and pressure, peaking of the femoral pressure pulse, and a diastolic wave in the right aortic pressure profile. Pulse wave velocity and peripheral input impedance increased with progressive constriction, and thus changes in both the timing and magnitude of reflections accounted for the altered reflection effects. Resolution of pressure and flow waves into incident and reflected components showed substantial reflection effects within the right aorta, with reflection coefficients at the first harmonic approaching 0.3 when constricted. Material properties measured from isolated segments of blood vessels revealed a major reflection site at the periphery and, surprisingly, at the junction of the truncus and right aorta. Thus, while our results clearly show that significant wave reflection phenomena are not restricted to birds and mammals, they also suggest that rather than cope with potential negative impacts of reflections, the crocodilian heart simply avoids them because of a large impedance mismatch at the truncus.

Alligators and Crocodiles↗
PubMed2006

Microtubule contribution to the reflectance of the retinal nerve fiber layer.

PURPOSE: The reflectance of the retinal nerve fiber layer (RNFL) arises from light scattering by cylindrical structures oriented parallel to ganglion cell axons. In amphibian retinas, at 440 nm, microtubules (MTs) contribute about one half of RNFL reflectance. In rodent retinas, MTs are the only structure contributing to RNFL birefringence. To increase understanding of the anatomic basis for clinical RNFL measurements, this study was conducted to evaluate the MT contribution to RNFL reflectance in rodent retinas by using the MT depolymerizing agent colchicine. METHODS: Reflectance of nerve fiber bundles in isolated rat retinas was measured at 460, 580, and 830 nm with a multispectral imaging reflectometer. Images were taken frequently over an extended period. During baseline, the tissue was perfused with a physiological solution. During a treatment period, the solution was switched either to a control solution or to a solution containing colchicine. RESULTS: Because of the high reflectance of the RNFL, nerve fiber bundles appeared as bright stripes against a darker retina. The reflectance of bundles was relatively stable in control experiments. With colchicine treatment, however, bundle reflectance at first decreased rapidly and then became stable. After 70 minutes of colchicine treatment, RNFL reflectance had declined to approximately 50% below baseline at all wavelengths. CONCLUSIONS: MTs contribute to RNFL reflectance at all wavelengths. Unlike RNFL birefringence, however, which totally disappears after colchicine treatment, about one half of RNFL reflectance remained after colchicine treatment. This result suggests that, in addition to MTs, other mechanisms may contribute to RNFL reflectance.

Animals↗
PubMed2006

Integrating professionalism in early medical education: the theory and application of reflective practice in the anatomy curriculum.

Renewed emphases on teaching professionalism require physicians to develop the ability to critically reflect upon their own decisions. Innovative programs that address teaching professionalism within medical curricula have been implemented in almost all medical schools. The foundation for many of these programs is "reflection," which is regarded as a core skill in professional competence. In order to achieve the desired outcomes and meet the demands of a required curriculum, an understanding of educational concepts in the designing of medical curricula is essential. Educators recognize that, for most medical students, professional growth is initiated during the first year of the medical curriculum and, therefore, traditionally pure content delivery courses such as first year anatomy course are being utilized now in order to explore issues related to critical thinking and professionalism. As a result, learning strategies such as "reflective practice" are beginning to play an important role in curriculum design. This article provides an overview of the theory of reflective practice, and demonstrates how reflective practice may be integrated into the anatomy curriculum. In order to incorporate reflective exercises into a curriculum, the basic elements of a reflective process are defined, strategies to implement reflective exercises within the course are described, and the benefits of reflective practice are highlighted. Therefore, in creating an environment that fosters reflective learning, the gap between theory and practice may be consolidated, which in the context of anatomy promotes the issue of teaching for relevance and clinical application.

Anatomy↗
PubMed2005

Autofluorescence and diffuse reflectance spectroscopy for oral oncology.

BACKGROUND AND OBJECTIVES: Autofluorescence and diffuse reflectance spectroscopy have been used separately and combined for tissue diagnostics. Previously, we assessed the value of autofluorescence spectroscopy for the classification of oral (pre-)malignancies. In the present study, we want to determine the contributions of diffuse reflectance and autofluorescence spectroscopy to diagnostic performance. STUDY DESIGN/MATERIALS AND METHODS: Autofluorescence and diffuse reflectance spectra were recorded from 172 oral lesions and 70 healthy volunteers. Autofluorescence spectra were corrected in first order for blood absorption effects using diffuse reflectance spectra. Principal Components Analysis (PCA) with various classifiers was applied to distinguish (1) cancer and (2) all lesions from healthy oral mucosa, and (3) dysplastic and malignant lesions from benign lesions. Autofluorescence and diffuse reflectance spectra were evaluated separately and combined. RESULTS: The classification of cancer versus healthy mucosa gave excellent results for diffuse reflectance as well as corrected autofluorescence (Receiver Operator Characteristic (ROC) areas up to 0.98). For both autofluorescence and diffuse reflectance spectra, the classification of lesions versus healthy mucosa was successful (ROC areas up to 0.90). However, the classification of benign and (pre-)malignant lesions was not successful for raw or corrected autofluorescence spectra (ROC areas <0.70). For diffuse reflectance spectra, the results were slightly better (ROC areas up to 0.77). CONCLUSIONS: The results for plain and corrected autofluorescence as well as diffuse reflectance spectra were similar. The relevant information for distinguishing lesions from healthy oral mucosa is probably sufficiently contained in blood absorption and scattering information, as well as in corrected autofluorescence. However, neither type of information is capable of distinguishing benign from dysplastic and malignant lesions. Combining autofluorescence and reflectance only slightly improved the results.

Adolescent↗
PubMed1984

Effect of nitroprusside on wave reflections in patients with heart failure.

The relationship between wave reflections and ventricular-vascular coupling has been the subject of considerable speculation. Since we have previously shown that low-dose nitroprusside infusion improved ventricular-vascular coupling (as evidenced by increases in cardiac output and in aortic and pulmonary arterial total external power) in patients with severe left ventricular failure and secondary pulmonary hypertension, we chose to examine the changes in their aortic and pulmonary arterial wave reflections in this study. Wave reflection indexes examined included calculated backward and forward pressure waves and the ratio of their magnitudes (reflection factor), the reflection coefficient spectrum obtained by taking the ratios of the corresponding Fourier harmonics of the backward and forward waves, two terminal reflection coefficients calculated as gamma t = (R - Zc)/(R + Zc), where Z is characteristic impedance and R is either total resistance or vascular resistance, and the difference between the maximum and minimum impedance moduli for frequencies of 4 to 15 Hz. In the systemic vasculature, nitroprusside produced large reductions in the elevated vascular resistances and decreased aortic reflections as indexed by the reflection factor and by both terminal reflection coefficients. In contrast, however, no significant changes were found in the pulmonary artery wave reflection indexes despite large reductions in the pulmonary resistances.

Aorta↗
PubMed2003

Reflection: a casualty of modularisation?

INTRODUCTION: The use of reflection in nursing and midwifery is well-established and reflective skills are taught on both pre- and post-registration courses as a way of integrating theory and practice, and of developing students' critical and analytical skills. Reflection is generally regarded positively with an assumption that reflective skills benefit both practitioners and patients. The aim of this study was to identify the educational strategies used to develop reflective skills in one pre-registration diploma in nursing curriculum. METHODS: The survey was cross-sectional in design. A questionnaire was designed for the study to explore perceptions of both students and lecturers in one educational establishment. Curriculum documentation was analysed to examine where in the curriculum the development of reflective skills was prominent. The sample consisted of two student cohorts from the adult branch and all senior lecturers within the Institute who taught on the pre-registration programme. RESULTS: The findings revealed a complex picture of students' and lecturers' views of the teaching and learning strategies used to develop reflective skills. Lectures and group work were the strategies cited most commonly by the students, whereas the lecturers felt the strategies used most often were personal tutorials, group work and case scenarios. The documentary analysis revealed that out of the 13 modules, there was explicit reference in only three modules to reflective practice. Furthermore, it was evident that the majority of lecturers were not clear where in the curriculum reflective skills were taught which suggested that an overview of the whole curriculum is not always evident. CONCLUSIONS: Modularisation may have contributed to a fragmentation in the way in which some key health practitioner skills are developed and built upon throughout a curriculum. There needs to be agreement on the nature of the skills which are central to the development of reflective practitioners and clear thinking on how these are developed and assessed within a curriculum.

Attitude of Health Personnel↗
PubMed2000

Reflection: nursing's practice and education panacea?

Nurses are now directed to 'reflect effectively and practice reflectively'. When there is scant evidence to support the use of reflection, why does the United Kingdom Central Council, English National Board for Nursing Midwifery and Health Visiting and institutes of nurse education insist that nurses, at all levels of experience, reflect? Before developing the debate in relation to the robustness or otherwise of the concept of 'reflection' and its application to practice, a discussion as to what constitutes nursing knowledge, followed by an examination of the main theories related to adult learning, is presented. The paper develops to encompass a critical examination of both theoretical and applied perspectives on reflection. Conceptual issues and assumptions related to reflection are explored. Key areas considered are whether the practice of reflection facilitates the improvement of one's knowledge, helps to generate theory and results in one becoming a more critical practitioner with resulting benefits for patients. It will be argued that reflective theory and practice has not yet been adequately tested and that there is a pressing need for evidence to demonstrate irrefutably the effectiveness of reflection on nursing practice, particularly with respect to patient outcomes.

Adult↗
PubMed2000

Exploring reflective thinking in nursing practice.

While it is claimed in the nursing literature that reflective thinking is the approach par excellence for learning and advancing the art and practice of nursing, few empirical studies have been undertaken in this area to date. Sense-Making, a qualitative research method, was utilized to obtain and analyse data from interviews with 10 registered nurses in order to study reflective thinking in actual nursing practice. Ten non-routine nursing situations were analysed for the presence of reflective thinking. Time-line interviews of the events resulted in a total of 59 micro-moments, each of which was explored in terms of the thinking processes utilized to make sense of the situation as well as the focus of their thought. 'Pre-perceptions' played an important part in how the respondents perceived their situation. Reflective thinking was extensively manifest, especially in moments of doubt and perplexity, and consisted of such cognitive activities as comparing and contrasting phenomena, recognizing patterns, categorizing perceptions, framing, and self-questioning in order to create meaning and understanding. Self-questioning was identified as a significant process within reflective thinking. By exploring and analysing the type of questions respondents were asking themselves, the study uncovered three hierarchical levels of reflective thinking. Respondents most often engaged in reflective thinking-for-action which centred on the here and now in order to act. Reflective thinking-for-evaluation focused on creating wholeness and contributed to the realization of multiple perceptions and multiple responses. Reflective thinking-for-critical-inquiry could not be demonstrated in the study sample. The findings of this study resulted in the development of a model of reflective thinking, which is discussed in terms of the implications for learning in nursing practice.

Decision Making↗
PubMed2001

Teacher candidates' reflective teaching and learning in a hospital setting - changing the pattern of practical training: a challenge to growing into teacherhood.

UNLABELLED: AIMS OF THE PROJECT: The main goal of the 'teacher candidates' reflective teaching and learning' project was to integrate theories of reflection in education and nursing practice. This was realised through teacher candidates' practical training in a hospital setting providing them with personal experiences of reflection in different forms and contexts. In this paper one teacher candidate pair's experiences of developing documentation in one operating theatre are described. BACKGROUND: The power of reflection is acknowledged in health care education and, on the other hand, also in nursing practice. Reflection, however, is not spontaneous but it requires active contribution. The key persons in this respect seem to be healthcare teachers. The challenges for today are that, for example, the theoretical background of reflection is multi-fold and that the concept of reflection is popularised in common use. DESIGN OF THE PROJECT: The project (1995-1998) was accomplished in one of the biggest university hospitals in Finland. On the collaborating wards, systematic team supervision was in progress. Teacher candidates planned and implemented in-service-training modules for teams based on educational needs raised during team supervision sessions. FINDINGS: The contribution of the project can be assessed as important to health care teacher education, but also to nursing practice. Practical training in a hospital setting enhanced teacher candidates' ability to work as teachers in a hospital organisation as well as a nursing college/polytechnic by providing them with a new viewpoint. They learned valuable lessons from applying theory, as planning in-service-training required continuous reflective discussion with the nursing staff but also theoretical reflection. Improvements in nursing practice were also promoted as staff educational needs were met. CONCLUSIONS: Shifting the teacher candidates' practical training into a hospital setting and emphasising reflection seemed to promote their professional development towards teacherhood and improve nursing practice.

Adult↗
PubMed1999

The use of brief written educational material to promote reflection amongst trained nurses: a pilot study.

The UKCC (1995) suggest that in order for nurses to maintain their registration, they must maintain a personal professional profile via reflection, and there are numerous approaches to the teaching of reflection. Similarly, several models of reflection exist. However, much of this activity has occurred without attempts to establish the effectiveness of either reflection or attempts to teach it. The current study attempted to examine whether written educational material could significantly improve nurses' reflective ability. Nineteen practising nurses were recruited from a variety of sources and offered an educational package, largely based on Boud et al. (1985) model of reflection in learning. In a repeated measures design study, these participants completed a reflective exercise before and after offering of the educational material. Their scripts were rated, using Wong et al.'s (1995) tool, by three raters, two of whom were unaware of whether the scripts were completed before or after offering of the educational material. An initial analysis showed that there were no statistically significant changes in subjects' reflective ability following education. However, removal from the analysis of 6 participants who had a pre-test ability at the highest possible level (and for whom no improvement was, therefore, possible) resulted in a significant improvement in participants' ability from pre- to post-test (z = -2.4450, P = 0.0145). Interrater reliability calculated using Cronbach's Alpha was 0.7210 for pretest reflective accounts and 0.7369 for post-test reflective accounts.

Adult↗
PubMed1998

Reflection of ultraviolet radiation from different skin types.

In this study using 43 male subjects, the spectral reflectance of ultraviolet radiation (UVR) has been measured from the skin of each subject's forearm. The total diffuse reflectance and directional characteristics of reflection were determined for different wavelengths. Mean values were determined for four skin types in both the ultraviolet A (UVA) and ultraviolet B (UVB) range from 280 to 400 nm. Reflection occurs in all directions and with cylindrical symmetry that is normal to the skin surface. The ability of skin to reflect UVR decreases rapidly with decreasing wavelength. Reflection is as high as 20% for 400 nm and falls below 1% at 280 nm. Average UVA (315 to 400 nm) reflectance can reach 12%, but is only about 2.5% in the UVB (280 to 315 nm) spectral range. The significant differences in reflectance occur between different skin types and are determined primarily by complexion. Skin types with moderate sensitivity to solar radiation, neither too pale nor too tanned, reflect the greatest UVR. In this skin type the protective mechanism of reflection dominates over a mechanism based upon the absorption of UVR by melanin pigment.

Adult↗
PubMed2004

Investigation of TRAM flap oxygenation and perfusion by near-infrared reflection spectroscopy and color-coded duplex sonography.

Near-infrared reflection spectroscopy, used experimentally for investigation of tissue hemoglobin content and oxygenation in various flaps, was tested in the pedicled transverse rectus abdominis musculocutaneous (TRAM) flap, chosen as a simple clinical model because of its well-known vascular anatomy and clinical relevance. The study intended to answer the following questions: Does the near-infrared reflection spectroscopy system used in this study measure tissue hemoglobin content and oxygenation in the superficial skin layers only, as proposed by the manufacturer? Is near-infrared reflection spectroscopy able to detect differences of tissue hemoglobin content and oxygenation in distinct zones of the TRAM flap skin before, early, and late after surgery? Does tissue hemoglobin content and oxygenation correspond to blood flow in the supplying superior epigastric artery and to clinical signs of TRAM flap perfusion and viability? In 11 patients, tissue hemoglobin content and oxygenation in the lower abdomen/TRAM flap, mastectomy skin flap, and contralateral breast were measured by a new near-infrared reflection spectroscopy system preoperatively, early postoperatively, and late postoperatively. Simultaneously, systolic peak flow in the ipsilateral superior epigastric artery was obtained by color-coded duplex sonography. Routine clinical monitoring was performed throughout the early postoperative period. Tissue hemoglobin content and oxygenation in the lower abdomen, mastectomy skin flap, and contralateral breast were similar before surgery but varied considerably between different patients. There were no significant differences among preoperative, early postoperative, and late postoperative values of tissue hemoglobin content and oxygenation in the mastectomy skin flap and contralateral breast. However, near-infrared reflection spectroscopy measurements of the TRAM flap revealed significant differences between preoperative and early postoperative values of tissue hemoglobin content and oxygenation and among zones I, II, and III early after surgery. Tissue hemoglobin content in the TRAM flap skin increased and oxygenation decreased early after surgery. Near-infrared reflection spectroscopy values corresponded to clinical signs of venous congestion predominantly in zone III. Late postoperative return of hemoglobin content and oxygenation in the TRAM flap toward preoperative values can be attributed to improved venous return by reversed flow across regurgitant valves and development of collateral circulation. Finally, there was a significant increase of systolic peak flow in the ipsilateral superior epigastric artery early after surgery. This could be related to the opening of small-caliber choke arteries between the superior and deep inferior epigastric arteries following ligation of the dominant deep inferior epigastric artery and TRAM flap transfer to the chest. Systolic peak flow returned to preoperative values late after surgery. The near-infrared reflection spectroscopy system used in this study appeared to measure hemoglobin content and oxygenation in the superficial skin layers only. Near-infrared reflection spectroscopy was able to detect differences of tissue hemoglobin content and oxygenation in the TRAM flap between preoperative and postoperative measurements and between distinct zones of the TRAM flap early postoperatively. Postoperative changes in near-infrared reflection spectroscopy values corresponded to clinical observations and blood flow in the superior epigastric artery measured by color-coded duplex sonography. Further experience is needed before near-infrared reflection spectroscopy can be advocated for routine clinical flap monitoring.

Adult↗
PubMed2006

Reflectance sharing: predicting appearance from a sparse set of images of a known shape.

Three-dimensional appearance models consisting of spatially varying reflectance functions defined on a known shape can be used in analysis-by-synthesis approaches to a number of visual tasks. The construction of these models requires the measurement of reflectance, and the problem of recovering spatially varying reflectance from images of known shape has drawn considerable interest. To date, existing methods rely on either: (1) low-dimensional (e.g., parametric) reflectance models, or (2) large data sets involving thousands of images (or more) per object. Appearance models based on the former have limited accuracy and generality since they require the selection of a specific reflectance model a priori, and while approaches based on the latter may be suitable for certain applications, they are generally too costly and cumbersome to be used for image analysis. We present an alternative approach that seeks to combine the benefits of existing methods by enabling the estimation of a nonparametric spatially varying reflectance function from a small number of images. We frame the problem as scattered-data interpolation in a mixed spatial and angular domain, and we present a theory demonstrating that the angular accuracy of a recovered reflectance function can be increased in exchange for a decrease in its spatial resolution. We also present a practical solution to this interpolation problem using a new representation of reflectance based on radial basis functions. This representation is evaluated experimentally by testing its ability to predict appearance under novel view and lighting conditions. Our results suggest that since reflectance typically varies slowly from point to point over much of an object's surface, we can often obtain a nonparametric reflectance function from a sparse set of images. In fact, in some cases, we can obtain reasonable results in the limiting case of only a single input image.

Algorithms↗