RESUMO
BACKGROUND: Noninvasive vascular tests are critical for identifying patients who may benefit from surgical revascularization, but current tests have significant limitations in people with diabetes. This study aimed to evaluate the ability of spatial frequency domain imaging (SFDI), an optical imaging method capable of measuring tissue oxygen saturation (StO2) and tissue hemoglobin, to assess lower extremity blood supply. METHODS: Ankle-brachial index, toe-brachial index, pedal Doppler waveforms, and SFDI images were prospectively evaluated in 47 consecutive patients with and without diabetes in whom there was concern for peripheral artery disease (PAD). SFDI is a noncontact optical imaging technology that uses structured illumination to quantify subsurface (2-3 mm in depth) StO2 and tissue hemoglobin in the dermal microcirculation (HbT1) and macrocirculation (HbT2) over a large field of view (15 × 20 cm) within 10 seconds. RESULTS: This demonstrates the ability of SFDI to capture reliable clinical measurements of perfusion in plantar aspects of the feet. SFDI StO2 values differentiate nondiabetic patients with and without arterial disease, defined as ankle-brachial index <0.9 (P = .06), but are limited in those with diabetes (P = .43). An elevated StO2 and reduced HbT1 are observed in people with diabetes compared with nondiabetic patients (P < .05). An SFDI-derived HbT2/HbT1 index differentiates diabetics with PAD vs no PAD (P < .01) using toe-brachial index <0.7 as a cutoff for PAD in diabetes. CONCLUSIONS: SFDI is a feasible, rapid, and easy to use widefield measurement of perfusion in a clinical setting. This first-of-use study suggests that the technology has potential to evaluate lower extremity perfusion in people with and without diabetes. Further studies with increased numbers of patients and end points including wound healing will need to be designed to fully evaluate the applicability of this new technology.
Assuntos
Angiopatias Diabéticas/diagnóstico por imagem , Extremidade Inferior/irrigação sanguínea , Imagem Óptica , Imagem de Perfusão/métodos , Doença Arterial Periférica/diagnóstico por imagem , Idoso , Índice Tornozelo-Braço , Biomarcadores/metabolismo , Angiopatias Diabéticas/fisiopatologia , Feminino , Hemoglobinas/metabolismo , Humanos , Masculino , Oxigênio/metabolismo , Doença Arterial Periférica/fisiopatologia , Valor Preditivo dos Testes , Prognóstico , Estudos Prospectivos , Fluxo Sanguíneo Regional , Reprodutibilidade dos Testes , Ultrassonografia DopplerRESUMO
BACKGROUND AND OBJECTIVE: Pressure ulcers (PU) are a significant problem facing the health system in the United States. Here, we present preliminary case studies demonstrating feasibility of Spatial Frequency Domain Imaging (SFDI) to assess skin status in high-risk populations and pre-existing wounds. SFDI is a wide-field non-contact optical imaging technology that uses structured light to obtain tissue optical properties and of tissue constituents. This study aims to determine the fit of SFDI for PU care and determine the next steps. STUDY DESIGN/MATERIALS AND METHODS: Patients at risk for pressure ulcers were imaged using a near-infrared SFDI system. SFDI-derived images of tissue function (tissue hemoglobin, tissue oxygen saturation) and structure (tissue scattering) were then compared to each other as well as a blinded dermatologist's clinical impressions. RESULTS: Four case series were chosen to demonstrate the imaging capability of this technology. The first scenario demonstrates normal skin of three patients without skin breakdown with spatially uniform measures of tissue oxygen saturation, scattering, and blood volume. The second scenario demonstrates a stage II PU; the third case shows non-blanchable erythema of an unstageable PU; a fourth scenario is a clinically indistinguishable skin rash versus early stages of a PU. In all these cases, we observe spatial changes in tissue constituents (decrease in tissue oxygen saturation, increased blood pooling, decreased scattering). CONCLUSION: We have presented the first use of SFDI for pressure ulcer imaging and staging. This preliminary study demonstrates the feasibility of this optical technology to assess tissue oxygen saturation and blood volume status in a quantitative manner. With the proposed improvements in modeling and hardware, SFDI has potential to provide a means for pressure ulcer risk stratification, healing and staging. Lasers Surg. Med. 49:827-834, 2017 © 2017 Wiley Periodicals, Inc.
Assuntos
Imagem Óptica/métodos , Úlcera por Pressão/diagnóstico por imagem , Idoso , Estudos de Viabilidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Imagem Óptica/instrumentação , Úlcera por Pressão/etiologia , Úlcera por Pressão/patologia , Estudos Prospectivos , Reprodutibilidade dos TestesRESUMO
BACKGROUND: Detecting failing tissue flaps before they are clinically apparent has the potential to improve postoperative flap management and salvage rates. This study demonstrates a model to quantitatively compare clinical appearance, as recorded via digital camera, with spatial frequency domain imaging (SFDI), a noninvasive imaging technique using patterned illumination to generate images of total hemoglobin and tissue oxygen saturation (stO2). METHODS: Using a swine pedicle model in which blood flow was carefully controlled with occlusion cuffs and monitored with ultrasound probes, throughput was reduced by 25%, 50%, 75%, and 100% of baseline values in either the artery or the vein of each of the flaps. The color changes recorded by a digital camera were quantified to predict which occlusion levels were visible to the human eye. SFDI was also used to quantify the changes in physiological parameters including total hemoglobin and oxygen saturation associated with each occlusion. RESULTS: There were no statistically significant changes in color above the noticeable perception levels associated with human vision during any of the occlusion levels. However, there were statistically significant changes in total hemoglobin and stO2 levels detected at the 50%, 75%, and 100% occlusion levels for arterial and venous occlusions. CONCLUSIONS: As demonstrated by the color imaging data, visual flap changes are difficult to detect until significant occlusion has occurred. SFDI is capable of detecting changes in total hemoglobin and stO2 as a result of partial occlusions before they are perceivable, thereby potentially improving response times and salvage rates.
Assuntos
Percepção de Cores , Retalhos de Tecido Biológico/irrigação sanguínea , Imagem Óptica , Fotografação , Animais , Biomarcadores/sangue , Retalhos de Tecido Biológico/fisiologia , Hemoglobinas/metabolismo , Oxigênio/sangue , SuínosRESUMO
We employ a clinical multiphoton microscope to monitor in vivo and noninvasively the changes in reduced nicotinamide adenine dinucleotide (NADH) fluorescence of human epidermal cells during arterial occlusion. We correlate these results with measurements of tissue oxy- and deoxyhemoglobin concentration during oxygen deprivation using spatial frequency domain imaging. During arterial occlusion, a decrease in oxyhemoglobin corresponds to an increase in NADH fluorescence in the basal epidermal cells, implying a reduction in basal cell oxidative phosphorylation. The ischemia-induced oxygen deprivation is associated with a strong increase in NADH fluorescence of keratinocytes in layers close to the stratum basale, whereas keratinocytes from epidermal layers closer to the skin surface are not affected. Spatial frequency domain imaging optical property measurements, combined with a multilayer Monte Carlo-based radiative transport model of multiphoton microscopy signal collection in skin, establish that localized tissue optical property changes during occlusion do not impact the observed NADH signal increase. This outcome supports the hypothesis that the vascular contribution to the basal layer oxygen supply is significant and these cells engage in oxidative metabolism. Keratinocytes in the more superficial stratum granulosum are either supplied by atmospheric oxygen or are functionally anaerobic. Based on combined hemodynamic and two-photon excited fluorescence data, the oxygen consumption rate in the stratum basale is estimated to be â¼0.035 µmoles/10(6) cells/h.
Assuntos
Queratinócitos/metabolismo , Microscopia de Fluorescência por Excitação Multifotônica/métodos , NAD/metabolismo , Pele/citologia , Absorção , Fluorescência , Hemoglobinas/metabolismo , Humanos , Queratinócitos/citologia , Modelos Biológicos , Método de Monte Carlo , Fatores de TempoRESUMO
INTRODUCTION: Although various methods exist for monitoring flaps during reconstructive surgery, surgeons primarily rely on assessment of clinical judgment. Early detection of vascular complications improves rate of flap salvage. Spatial frequency domain imaging (SFDI) is a promising new technology that provides oxygenation images over a large field of view. The goal of this clinical pilot study is to use SFDI in perforator flap breast reconstruction. METHODS: Three women undergoing unilateral breast reconstruction after mastectomy were enrolled for our study. The SFDI system was deployed in the operating room, and images acquired over the course of the operation. Time points included images of each hemiabdominal skin flap before elevation, the selected flap after perforator dissection, and after microsurgical transfer. RESULTS: Spatial frequency domain imaging was able to measure tissue oxyhemoglobin concentration (ctO2Hb), tissue deoxyhemoglobin concentration, and tissue oxygen saturation (stO2). Images were created for each metric to monitor flap status and the results quantified throughout the various time points of the procedure. For 2 of 3 patients, the chosen flap had a higher ctO2Hb and stO2. For 1 patient, the chosen flap had lower ctO2Hb and stO2. There were no perfusion deficits observed based on SFDI and clinical follow-up. CONCLUSIONS: The results of our initial human pilot study suggest that SFDI has the potential to provide intraoperative oxygenation images in real-time during surgery. With the use of this technology, surgeons can obtain tissue oxygenation and hemoglobin concentration maps to assist in intraoperative planning; this can potentially prevent complications and improve clinical outcome.
Assuntos
Mamoplastia/métodos , Monitorização Intraoperatória/métodos , Retalho Perfurante/irrigação sanguínea , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Adulto , Idoso , Biomarcadores/metabolismo , Feminino , Seguimentos , Hemoglobinas/metabolismo , Humanos , Mastectomia , Pessoa de Meia-Idade , Monitorização Intraoperatória/instrumentação , Avaliação de Resultados em Cuidados de Saúde , Oxigênio/metabolismo , Oxiemoglobinas/metabolismo , Retalho Perfurante/transplante , Projetos Piloto , Espectroscopia de Luz Próxima ao Infravermelho/instrumentaçãoRESUMO
The microvasculature (with vessels <100 µm in diameter) plays a crucial role in tissue oxygenation, perfusion and wound healing in the lower limb. While this holds clinical significance, microvasculature evaluation in the limbs is not a standard practice. Surgical interventions focus on reestablishing blood flow in larger vessels affected by the peripheral artery disease (PAD). Nevertheless, the impact of revascularization on tissue oxygenation and perfusion in severe microvascular disease (MVD) is still unknown. We present the cases of two patients who underwent surgical revascularization for peripheral blood flow with different outcomes. Patient A had PAD, while B had PAD, severe MVD and a non-healing wound. Although both showed improvements in ankle-brachial index post-op, spatial frequency domain imaging metrics (which measure microvascular oxygenation and perfusion) remained unchanged in B, indicating a potential gap in assessing the surgical efficacy in MVD using ankle brachial index and emphasizing microcirculation evaluation in optimizing wound healing outcomes.
RESUMO
BACKGROUND: Microvascular disease (MVD) describes systemic changes in the small vessels (~100 um diameter) that impair tissue oxygenation and perfusion. MVD is a common but poorly monitored complication of diabetes. Recent studies have demonstrated that MVD: (i) is an independent risk factor for ulceration and amputation and (ii) increases risk of adverse limb outcomes synergistically with PAD. Despite the clinical relevance of MVD, microvascular evaluation is not standard in a vascular assessment. METHODS: We evaluated 299 limbs from 153 patients seen clinically for possible lower extremity PAD. The patients were assessed by ankle brachial index (ABI), toe brachial index (TBI), and spatial frequency domain imaging (SFDI). These measurements were evaluated and compared to patient MVD status, defined by clinical diagnoses of (in ascending order of severity) no diabetes; diabetes; diabetes + neuropathy; diabetes + neuropathy + retinopathy. RESULTS: SFDI-derived parameters HbT1 and StO2 were significantly different across the MVD groups (P < .001). A logistic regression model based on HbT1 and StO2 differentiated limbs with severe MVD (diabetes+neuropathy+retinopathy) from the larger group of limbs from patients with only diabetes (P = .001, area under the curve = 0.844). Neither ABI nor TBI significantly differentiated these populations. CONCLUSIONS: Standard assessment of PAD using ABI and TBI are inadequate for detecting MVD in at-risk populations. SFDI-defined HbT1 and StO2 are promising tools for evaluating MVD. Prospective studies with wound-based outcomes would be useful to further evaluate the role MVD assessment could play in routine clinical evaluation of patients at risk for lower extremity complications.
Assuntos
Retinopatia Diabética , Doença Arterial Periférica , Humanos , Estudos Prospectivos , Doença Arterial Periférica/diagnóstico por imagem , Extremidade Inferior , Índice Tornozelo-Braço , Gravidade do PacienteRESUMO
BACKGROUND AND OBJECTIVE: Objective methods to assess port wine stain (PWS) response to laser treatment have been the subject of various research efforts for several years. Herein, we present a pilot study using a newly developed, light emitting diode (LED) based spatial frequency domain imaging (SFDI) device to record quantitatively biochemical compositional changes in PWS after laser therapy. STUDY DESIGN/PATIENTS AND METHODS: A SFDI system was used to image before, and after, five PWS treatment sessions [n = 4 subjects (one subject was imaged before and after two consecutive laser treatments)]. SFDI derived wide-field optical properties (absorption and scattering) and tissue chromophore concentrations including oxy-hemoglobin (ctO(2) Hb), deoxy-hemoglobin (ctHHb), total hemoglobin (ctTHb), and tissue oxygen saturation (stO(2) ) are presented for skin imaged prior to and immediately after laser treatment. The SFDI derived images were analyzed by comparing the above measurements in PWS to those of normal skin and tracking changes immediately after laser exposure. RESULTS: Elevated oxy-hemoglobin (>20%) and tissue oxygen saturation (>5%) were measured in all PWS lesions and compared to values for normal skin prior to treatment. Laser treatment resulted in an increase in deoxy-hemoglobin (>100%), decrease in tissue oxygen saturation (>10%), and reduced scattering (>15%) in all PWS lesions. One subject was followed before and after two consecutive laser treatments and the overall improvement in PWS lesion blanching was quantitatively assessed by measuring a 45% decrease in dermal blood volume. CONCLUSION: SFDI is a rapid non-contact wide-field optical technique that shows potential as an imaging device that can be used to quantify biochemical compositional changes in PWS after laser therapy. Future work will investigate the potential of SFDI to provide intra-operative guidance for laser therapy of PWS lesions on an individual patient basis.
Assuntos
Diagnóstico por Imagem/métodos , Terapia com Luz de Baixa Intensidade , Mancha Vinho do Porto/patologia , Mancha Vinho do Porto/radioterapia , Pele/metabolismo , Adulto , Idoso , Criança , Feminino , Hemoglobinas/metabolismo , Humanos , Masculino , Oxigênio/metabolismo , Oxiemoglobinas/metabolismo , Projetos PilotoRESUMO
Laser speckle imaging (LSI) is a fast, noninvasive method to obtain relative particle dynamics in highly light scattering media, such as biological tissue. To make quantitative measurements, we combine LSI with spatial frequency domain imaging, a technique where samples are illuminated with sinusoidal intensity patterns of light that control the characteristic path lengths of photons in the sample. We use both diffusion and radiative transport to predict the speckle contrast of coherent light remitted from turbid media. We validate our technique by measuring known Brownian diffusion coefficients (D(b)) of scattering liquid phantoms. Monte Carlo (MC) simulations of radiative transport were found to provide the most accurate contrast predictions. For polystyrene microspheres of radius 800 nm in water, the expected and fit D(b) using radiative transport were 6.10E-07 and 7.10E-07 mm²/s, respectively. For polystyrene microspheres of radius 1026 nm in water, the expected and fit D(b) were 4.7E-07 and 5.35 mm²/s, respectively. For scattering particles in water-glycerin solutions, the fit fractional changes in D(b) with changes in viscosity were all found to be within 3% of the expected value.
Assuntos
Lasers , Imagem Molecular/instrumentação , Imagem Molecular/métodos , Difusão , Glicerol/química , Microesferas , Método de Monte Carlo , Fenômenos Ópticos , Imagens de Fantasmas , Poliestirenos/química , ViscosidadeRESUMO
The use of free flaps in lower extremity reconstructive surgery has seen growing adoption for treating tissue loss in patients with diabetes mellitus and peripheral artery disease as a means for limb preservation. The superficial circumflex iliac perforator artery (SCIP) flap is one of the most commonly utilized flaps in foot reconstruction and has demonstrated benefits over amputation. Patients with impaired vascular and neurologic function are predisposed to complications following lower extremity reconstructive surgery, particularly ischemia in the angiosomes of the arteries used for flap anastomosis. We present the case of a patient who underwent successful SCIP flap reconstruction of the calcaneus but developed gangrene in the forefoot region supplied by a hypoplastic posterior tibial artery in subsequent months. The changes in tissue oxygenation and hemoglobin distribution of the foot are shown using spatial frequency domain imaging throughout the flap healing process and eventual tissue necrosis.
RESUMO
INTRODUCTION: The use of non-invasive vascular and perfusion diagnostics are an important part of assessing lower extremity ulceration and amputation risk in patients with diabetes mellitus. Methods for detecting impaired microvascular vasodilatory function in patients with diabetes may have the potential to identify sites at risk of ulceration prior to clinically identifiable signs. Spatial frequency domain imaging (SFDI) uses patterned near-infrared and visible light spectroscopy to determine tissue oxygen saturation and hemoglobin distribution within the superficial and deep dermis, showing distinct microcirculatory and oxygenation changes that occur prior to neuropathic and neuroischemic ulceration. RESEARCH DESIGNS AND METHODS: 35 patients with diabetes mellitus and a history of diabetic foot ulceration were recruited for monthly imaging with SFDI. Two patients who ulcerated during the year-long longitudinal study were selected for presentation of their clinical course alongside the dermal microcirculation biomarkers from SFDI. RESULTS: Patient 1 developed a neuropathic ulcer portended by a focal increase in tissue oxygen saturation and decrease in superficial papillary hemoglobin concentration 3 months prior. Patient 2 developed bilateral neuroischemic ulcers showing decreased tissue oxygen saturation and increased superficial papillary and deep dermal reticular hemoglobin concentrations. CONCLUSIONS: Wounds of different etiology show unique dermal microcirculatory changes prior to gross ulceration. Before predictive models can be developed from SFDI, biomarker data must be correlated with the clinical course of patients who ulcerate while being followed longitudinally. TRIAL REGISTRATION NUMBER: NCT03341559.
Assuntos
Diabetes Mellitus , Pé Diabético , Doenças do Sistema Nervoso Periférico , Amputação Cirúrgica , Pé Diabético/diagnóstico por imagem , Humanos , Estudos Longitudinais , MicrocirculaçãoRESUMO
AIMS: Annually, up to 4% of people with diabetes present with a chronic foot ulcer. Quantitative real-time testing to identify patients at risk for ulceration can guide preventative care. Here, we assess whether a non-invasive optical imaging technique, Spatial Frequency Domain Imaging (SFDI), can identify patients at the highest risk for ulceration and predict ulcer onset. METHODS: We imaged 252 subjects with diabetes at Kaiser Permanente, Southern California. SFDI derived tissue biomarkers of microcirculation were compared between subjects with and without a history of ulceration, and subjects who did or did not develop ulcers after 1â¯year. RESULTS: Feet of subjects at the highest risk (i.e. history of ulceration) had significantly lower hemoglobin in the papillary dermis (HbT1), along with higher oxygenation (StO2) due to poor extraction. These subjects also had more homogeneous hemoglobin spread in the reticular dermis (HbT2) and tissue scattering (related to skin structure). Prediction based on HbT1 and tissue scattering identified new ulcerations and performed with sensitivity/specificity of 68.8%/64.8% and 75.0%/69.1%, respectively. CONCLUSION: These results show that SFDI hemoglobin distribution and oxygenation biomarkers provide a quantitative basis for ulcer risk stratification and ulcer onset prediction.
Assuntos
Diabetes Mellitus , Pé Diabético , Biomarcadores , California , Pé Diabético/complicações , Pé Diabético/diagnóstico , Hemoglobinas , Humanos , Microcirculação , Medição de RiscoRESUMO
We present a wide-field method for obtaining three-dimensional images of turbid media. By projecting patterns of light of varying spatial frequencies on a sample, we reconstruct quantitative, depth resolved images of absorption contrast. Images are reconstructed using a fast analytic inversion formula and a novel correction to the diffusion approximation for increased accuracy near boundaries. The method provides more accurate quantification of optical absorption and higher resolution than standard diffuse reflectance measurements.
Assuntos
Luz , Óptica e Fotônica , Tomografia Óptica/instrumentação , Tomografia Óptica/métodos , Absorção , Diagnóstico por Imagem/métodos , Desenho de Equipamento , Análise de Fourier , Humanos , Processamento de Imagem Assistida por Computador , Modelos Estatísticos , Nefelometria e Turbidimetria , Imagens de Fantasmas , Reprodutibilidade dos Testes , Propriedades de SuperfícieRESUMO
We describe a noncontact profile correction technique for quantitative, wide-field optical measurement of tissue absorption (microa) and reduced scattering (micros) coefficients, based on geometric correction of the sample's Lambertian (diffuse) reflectance intensity. Because the projection of structured light onto an object is the basis for both phase-shifting profilometry and modulated imaging, we were able to develop a single instrument capable of performing both techniques. In so doing, the surface of the three-dimensional object could be acquired and used to extract the object's optical properties. The optical properties of flat polydimethylsiloxane (silicone) phantoms with homogenous tissue-like optical properties were extracted, with and without profilometry correction, after vertical translation and tilting of the phantoms at various angles. Objects having a complex shape, including a hemispheric silicone phantom and human fingers, were acquired and similarly processed, with vascular constriction of a finger being readily detectable through changes in its optical properties. Using profilometry correction, the accuracy of extracted absorption and reduced scattering coefficients improved from two- to ten-fold for surfaces having height variations as much as 3 cm and tilt angles as high as 40 deg. These data lay the foundation for employing structured light for quantitative imaging during surgery.
Assuntos
Processamento de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Óptica e Fotônica/métodos , Absorção , Algoritmos , Dedos/irrigação sanguínea , Dedos/fisiologia , Humanos , Luz , Imagens de Fantasmas , Espalhamento de Radiação , Propriedades de SuperfícieRESUMO
Spatial frequency domain imaging (SFDI) has witnessed very rapid growth over the last decade, owing to its unique capabilities for imaging optical properties and chromophores over a large field-of-view and in a rapid manner. We provide a comprehensive review of the principles of this imaging method as of 2019, review the modeling of light propagation in this domain, describe acquisition methods, provide an understanding of the various implementations and their practical limitations, and finally review applications that have been published in the literature. Importantly, we also introduce a group effort by several key actors in the field for the dissemination of SFDI, including publications, advice in hardware and implementations, and processing code, all freely available online.
Assuntos
Processamento de Imagem Assistida por Computador/métodos , Imagem Óptica , Animais , Queimaduras/diagnóstico por imagem , Desenho de Equipamento , Mãos/diagnóstico por imagem , Humanos , Intestino Grosso/diagnóstico por imagem , Imagem Óptica/instrumentação , Imagem Óptica/métodos , Cirurgia Assistida por Computador , SuínosRESUMO
This guest editorial introduces the Special Section on Spatial Frequency Domain Imaging.
Assuntos
Imagem Óptica , Humanos , Espalhamento de RadiaçãoRESUMO
Imaging Cherenkov emission during radiotherapy permits real-time visualization of external beam delivery on superficial tissue. This signal is linear with absorbed dose in homogeneous media, indicating potential for quantitative dosimetry. In humans, the inherent heterogeneity of tissue optical properties (primarily from blood and skin pigment) distorts the linearity between detected Cherenkov signal and absorbed dose. We examine the potential to correct for superficial vasculature using spatial frequency domain imaging (SFDI) to map tissue optical properties for large fields of view. In phantoms, applying intensity corrections to simulate blood vessels improves Cherenkov image (CI) negative contrast by 24% for a vessel 1.9-mm-in diameter. In human trials, SFDI and CI are acquired for women undergoing whole breast radiotherapy. Applied corrections reduce heterogeneity due to vasculature within the sampling limits of the SFDI from a 22% difference as compared to the treatment plan, down to 6% in one region and from 14% down to 4% in another region. The optimal use for this combined imaging system approach is to correct for small heterogeneities such as superficial blood vessels or for interpatient variations in blood/melanin content such that the corrected CI more closely represents the surface dose delivered.
Assuntos
Neoplasias da Mama , Interpretação de Imagem Assistida por Computador/métodos , Radiometria/métodos , Processamento de Sinais Assistido por Computador , Mama/diagnóstico por imagem , Neoplasias da Mama/diagnóstico por imagem , Neoplasias da Mama/radioterapia , Desenho de Equipamento , Feminino , Humanos , Imagens de Fantasmas , Radiometria/instrumentaçãoRESUMO
The cochlea is the mammalian organ of hearing. Its predominant vibratory element, the basilar membrane, is tonotopically tuned, based on the spatial variation of its mass and stiffness. The constituent collagen fibers of the basilar membrane affect its stiffness. Laser irradiation can induce collagen remodeling and deposition in various tissues. We tested whether similar effects could be induced within the basilar membrane. Trypan blue was perfused into the scala tympani of anesthetized mice to stain the basilar membrane. We then irradiated the cochleas with a 694-nm pulsed ruby laser at 15 or 180 Jcm(2). The mice were sacrificed 14 to 16 days later and collagen organization was studied. Polarization microscopy revealed that laser irradiation increased the birefringence within the basilar membrane in a dose-dependent manner. Electron microscopy demonstrated an increase in the density of collagen fibers and the deposition of new fibrils between collagen fibers after laser irradiation. As an assessment of hearing, auditory brainstem response (ABR) thresholds were found to increase moderately after 15 Jcm(2) and substantially after 180 Jcm(2). Our results demonstrate that collagen remodeling and new collagen deposition occurs within the basilar membrane after laser irradiation in a similar fashion to that found in other tissues.
Assuntos
Limiar Auditivo/fisiologia , Limiar Auditivo/efeitos da radiação , Membrana Basilar/fisiologia , Membrana Basilar/efeitos da radiação , Colágeno/metabolismo , Lasers , Animais , Colágeno/efeitos da radiação , Camundongos , Camundongos Endogâmicos C57BL , Doses de RadiaçãoRESUMO
We introduce a tomographic approach for three-dimensional imaging of evoked hemodynamic activity, using broadband illumination and diffuse optical tomography (DOT) image reconstruction. Changes in diffuse reflectance in the rat somatosensory cortex due to stimulation of a single whisker were imaged at a frame rate of 5 Hz using a hyperspectral image mapping spectrometer. In each frame, images in 38 wavelength bands from 484 to 652 nm were acquired simultaneously. For data analysis, we developed a hyperspectral DOT algorithm that used the Rytov approximation to quantify changes in tissue concentration of oxyhemoglobin ([Formula: see text]) and deoxyhemoglobin (ctHb) in three dimensions. Using this algorithm, the maximum changes in [Formula: see text] and ctHb were found to occur at [Formula: see text] and [Formula: see text] beneath the surface of the cortex, respectively. Rytov tomographic reconstructions revealed maximal spatially localized increases and decreases in [Formula: see text] and ctHb of [Formula: see text] and [Formula: see text], respectively, with these maximum changes occurring at [Formula: see text] poststimulus. The localized optical signals from the Rytov approximation were greater than those from modified Beer-Lambert, likely due in part to the inability of planar reflectance to account for partial volume effects.
RESUMO
The standard of care for clinical assessment of burn severity and extent lacks a quantitative measurement. In this work, spatial frequency domain imaging (SFDI) was used to measure 48 thermal burns of graded severity (superficial partial, deep partial, and full thickness) in a porcine model. Functional (total hemoglobin and tissue oxygen saturation) and structural parameters (tissue scattering) derived from the SFDI measurements were monitored over 72 h for each burn type and compared to gold standard histological measurements of burn depth. Tissue oxygen saturation (stO2) and total hemoglobin (ctHbT) differentiated superficial partial thickness burns from more severe burn types after 2 and 72 h, respectively (p < 0.01), but were unable to differentiate deep partial from full thickness wounds in the first 72 h. Tissue scattering parameters separated superficial burns from all burn types immediately after injury (p < 0.01), and separated all three burn types from each other after 24 h (p < 0.01). Tissue scattering parameters also showed a strong negative correlation to histological burn depth as measured by vimentin immunostain (r² > 0.89). These results show promise for the use of SFDI-derived tissue scattering as a correlation to burn depth and the potential to assess burn depth via a combination of SFDI functional and structural parameters.