Near-infrared Imaging Device Research Articles

Redefining Wound Healing Using Near-Infrared Spectroscopy.

No standard definition for a completely healed wound currently exists; it is recommended that providers use a reliable wound assessment tool to determine healing. The objective of this feasibility study was to determine if a point-of-care, noncontact, near-infrared (NIR) imaging device could provide an objective measure of wound resolution and guide clinical decision-making for the optimal time to transition from protective wound dressings and gradual return to full activity. In this single-center feasibility study, adult patients 18 years and older with a lower extremity wound of any size and etiology were seen weekly for wound assessment and standard-of-care treatment. The researchers performed serial imaging with a point-of-care, noncontact, NIR imaging device (Snapshot NIR ; Kent Imaging Inc) to assess the wound and surrounding skin and evaluated the difference in time to 100% reepithelialization on visual inspection and homogeneous tissue oxygen saturation levels at the wound site and surrounding closed skin envelope. An average time difference of 13.5 ± 10 days (median, 12 days; range, 0-35 days) was observed between 100% reepithelialization on visual wound inspection and imaging assessment. Further, NIR imaging could determine when a patient was at risk for recurrent wound breakdown. The addition of point-of-care, noncontact, NIR imaging may help guide clinical decision-making for the optimal time to transition from protective wound dressings with gradual return to full activity and minimize wound recurrence.

Fabrication of Tuneable Tissue-Mimicking Phantom for Optical Methods.

Tissue mimicking optical phantoms are commonly used to calibrate or validate the performance of near-infrared spectroscopy or tomography. Human tissue is not only irregular in shape, but also exhibits dynamic behaviour, which can cause changes in optical properties. However, existing phantoms lack complex structures and/or continuously varying optical properties. The project aimed to design, fabricate and characterise a novel phantom system for testing near-infrared imaging devices. We designed a dynamic tissue-mimicking phantom platform which features arbitrary internal shapes and variable optical properties. The solid part of phantom was made of silicone material with absorbing and scattering properties similar to the brain. We printed a semi-ellipsoidal sphere (a major axis=20 mmand a minor axis=the third axis=12 mm) using a water-soluble material polyvinyl alcohol (PVA). The shape was placed at the depth of 5 mm in the silicone bulk. The desired internal hollow structure was formed after curing and submerging the phantom in water. The liquid part contained dyes and Intralipid. The optical properties within the internal shape were adjusted by injecting the liquid solutions of varying dye concentrations with a syringe pump at a constant rate. The phantom was measured by a frequency domain near-infrared spectroscopy (FD NIRS) and imaged by a time domain near-infrared optical tomography (TD NIROT). A dynamic phantom system with a complex internal structure and varying optical properties was created. Changes in light intensity were detected by the FD NIRS. The internal structure of this phantom was accurately recovered by NIROT image reconstruction. We successfully developed a novel phantom system with an internal complex shape and continuously adjustable optical properties. This phantom was accurately imaged using NIROT, and the changing light intensity was detected by NIRS. It is a valuable tool for validating optical technologies.

Design and fabrication of near-infrared metalens

Metalens is an imaging device based on metasurfaces, which can accurately regulate the phase, polarization, and amplitude of light. It has advantages of lightweight, easy-integration and planarizartion. For miniaturization and integration of near-infrared imaging devices, a near-infrared polarized insensitive metalens based on amorphous silicon was designed and fabricated. For selecting basic structures, the focusing efficiency of metalenses designed by 8-order and 6-order primitives were compared. To improve the processing tolerance and reduce the processing difficulty, the 8-order primitive was used to design metalens, and the maximum depth-width ratio was 6. For large-span between simulation and processing of metalens, the 600 nm-thick polysilicon by chemical vapor deposition was grew. The metalens was made by electron beam etching. The measured results show that the metalens has a good appearance and the focusing efficiency is 65%.

Development and Validation of a Smartphone-Based Near-Infrared Optical Imaging Device to Measure Physiological Changes In-Vivo.

Smartphone-based technologies for medical imaging purposes are limited, especially when it involves the measurement of physiological information of the tissues. Herein, a smartphone-based near-infrared (NIR) imaging device was developed to measure physiological changes in tissues across a wide area and without contact. A custom attachment containing multiple multi-wavelength LED light sources (690, 800, and 840 nm; and <4 mW of optical power per LED), source driver, and optical filters and lenses was clipped onto a smartphone that served as the detector during data acquisition. The ability of the device to measure physiological changes was validated via occlusion studies on control subjects. Noise removal techniques using singular value decomposition algorithms effectively removed surface noise and distinctly differentiated the physiological changes in response to occlusion. In the long term, the developed smartphone-based NIR imaging device with capabilities to capture physiological changes will be a great low-cost alternative for clinicians and eventually for patients with chronic ulcers and bed sores, and/or in pre-screening for potential ulcers in diabetic subjects.

Estimating carotid pulse and breathing rate from near-infrared video of the neck

Objective: Non-contact physiological measurement is a growing research area that allows capturing vital signs such as heart rate (HR) and breathing rate (BR) comfortably and unobtrusively with remote devices. However, most of the approaches work only in bright environments in which subtle photoplethysmographic and ballistocardiographic signals can be easily analyzed and/or require expensive and custom hardware to perform the measurements. Approach: This work introduces a low-cost method to measure subtle motions associated with the carotid pulse and breathing movement from the neck using near-infrared (NIR) video imaging. A skin reflection model of the neck was established to provide a theoretical foundation for the method. In particular, the method relies on template matching for neck detection, principal component analysis for feature extraction, and hidden Markov models for data smoothing. Main results: We compared the estimated HR and BR measures with ones provided by an FDA-cleared device in a 12-participant laboratory study: the estimates achieved a mean absolute error of 0.36 beats per minute and 0.24 breaths per minute under both bright and dark lighting. Significance: This work advances the possibilities of non-contact physiological measurement in real-life conditions in which environmental illumination is limited and in which the face of the person is not readily available or needs to be protected. Due to the increasing availability of NIR imaging devices, the described methods are readily scalable.

Sol-Gel Processed p-Type CuO Phototransistor for a Near-Infrared Sensor

Solutionp-type thin-film transistors, consisting of sol-gel-processed CuO films, were fabricated. The optoelectric properties of sol-gel-processed, CuO-based back gate thin-film transistors were investigated, and a detectivity of 1.38 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> (cm Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) was achieved. This detectivity for sol-gel-processed CuO thin-film transistors is higher than that of the previously reported layered two-dimensional material systems and comparable to that of devices based on a one-dimensional nanowire system. Our results indicate that the sol-gel-processed, CuO-based photodetector system is a promising candidate for applications, such as near-infrared imaging devices, sensors, solar cells, and p-type inks for future printed electronics.

Oxygen-Sensing Paint-On Bandage: Calibration of a Novel Approach in Tissue Perfusion Assessment.

Knowledge of tissue oxygenation status is fundamental in the prevention of postoperative flap failure. Recently, the authors introduced a novel oxygen-sensing paint-on bandage that incorporated an oxygen-sensing porphyrin with a commercially available liquid bandage matrix. In this study, the authors extend validation of their oxygen-sensing bandage by comparing it to the use of near-infrared tissue oximetry in addition to Clark electrode measurements. The oxygen-sensing paint-on bandage was applied to the left hind limb in a rodent model. Simultaneously, a near-infrared imaging device and Clark electrode were attached to the right and left hind limbs, respectively. Tissue oxygenation was measured under normal, ischemic (aortic ligation), and reperfused conditions. On average, the oxygen-sensing paint-on bandage measured a decrease in transdermal oxygenation from 85.2 mmHg to 64.1 mmHg upon aortic ligation. The oxygen-sensing dye restored at 81.2 mmHg after unclamping. Responses in both control groups demonstrated a similar trend. Physiologic changes from normal to ischemic and reperfused conditions were statistically significantly different in all three techniques (p < 0.001). The authors' newly developed oxygen-sensing paint-on bandage exhibits a comparable trend in oxygenation recordings in a rat model similar to conventional oxygenation assessment techniques. This technique could potentially prove to be a valuable tool in the routine clinical management of flaps following free tissue transfer. Incorporating oxygen-sensing capabilities into a simple wound dressing material has the added benefit of providing both wound protection and constant wound oxygenation assessment.

Intraoperative Near-infrared Imaging for Parathyroid Gland Identification by Auto-fluorescence: A Feasibility Study.

Parathyroid glands (PGs) can be particularly hard to distinguish from surrounding tissue and thus can be damaged or removed during thyroidectomy. Postoperative hypoparathyroidism is the most common complication after thyroidectomy. Very recently, it has been found that the parathyroid tissue shows near-infrared (NIR) auto-fluorescence which could be used for intraoperative detection, without any use of contrast agents. The work described here presents a histological validation ex vivo of the NIR imaging procedure and evaluates intraoperative PG detection by NIR auto-fluorescence using for the first time to our knowledge a commercially available clinical NIR imaging device. Ex vivo study on resected operative specimens combined with a prospective in vivo study of consecutive patients who underwent total or partial thyroid, or parathyroid surgery at a comprehensive cancer center. During surgery, any tissue suspected to be a potential PG by the surgeon was imaged with the Fluobeam 800 (®) system. NIR imaging was compared to conventional histology (ex vivo) and/or visual identification by the surgeon (in vivo). We have validated NIR auto-fluorescence with an ex vivo study including 28 specimens. Sensitivity and specificity were 94.1 and 80%, respectively. Intraoperative NIR imaging was performed in 35 patients and 81 parathyroids were identified. In 80/81 cases, the fluorescence signal was subjectively obvious on real-time visualization. We determined that PG fluorescence is 2.93±1.59 times greater than thyroid fluorescence in vivo. Real-time NIR imaging based on parathyroid auto-fluorescence is fast, safe, and non-invasive and shows very encouraging results, for intraoperative parathyroid identification.

Development of near Infrared Imaging Devices and Their Applications

Near infrared (NIR) technology has several attractive features, such as suitability for non-destructive and in situ analysis, suitability for collection of transmission measurements, availability of optical fibres, high-speed monitoring and stability; it is therefore widely used in the analysis of pharmaceuticals, polymers, biological materials, biomedical samples, agricultural products etc. 1–3 Moreover, recently, NIR imaging technology has considerably enhanced the potential of NIR spectroscopy used in practical situations, because it can provide insightful evaluations regarding surface homogeneity, morphology and component distribution in a sample. Consequently, a number of NIR imaging devices have been developed by commercial companies and researchers in the past decade. Generally, imaging devices involving microscopy have been employed to facilitate detailed analysis of the target material. Moreover, portability and the capability to make wide-area measurements at high speed are integral parts of the development of new NIR imaging devices for diverse practical situations such as on-line process monitoring. However, NIR imaging devices which have the above advantages are still under development and elucidation of the optimum evaluation method(s) to predict component distributions in a target based on NIR imaging has not yet been fully realised for most applications. Our research group has collaborated with a number of companies and has recently developed two NIR imaging devices. 4–7

Image monitoring of pharmaceutical blending processes and the determination of an end point by using a portable near-infrared imaging device based on a polychromator-type near-infrared spectrometer with a high-speed and high-resolution photo diode array detector.

In the present study we have developed a new version (ND-NIRs) of a polychromator-type near-infrared (NIR) spectrometer with a high-resolution photo diode array detector, which we built before (D-NIRs). The new version has four 5 W halogen lamps compared with the three lamps for the older version. The new version also has a condenser lens with a shorter focal point length. The increase in the number of the lamps and the shortening of the focal point of the condenser lens realize high signal-to-noise ratio and high-speed NIR imaging measurement. By using the ND-NIRs we carried out the in-line monitoring of pharmaceutical blending and determined an end point of the blending process. Moreover, to determinate a more accurate end point, a NIR image of the blending sample was acquired by means of a portable NIR imaging device based on ND-NIRs. The imaging result has demonstrated that the mixing time of 8 min is enough for homogeneous mixing. In this way the present study has demonstrated that ND-NIRs and the imaging system based on a ND-NIRs hold considerable promise for process analysis.

Selective removal of demineralized enamel using a CO2 laser coupled with near-IR reflectance imaging.

Detection and diagnosis of early dental caries lesions can be difficult due to variable tooth coloration, staining of the teeth and poor contrast between sound and demineralized enamel. These problems can be overcome by using near-infrared (NIR) imaging. Previous studies have demonstrated that lasers can be integrated with NIR imaging devices, allowing image-guided ablation. The aim of this study was to demonstrate that NIR light at 1500 - 1700 nm can be used to guide a 9.3-μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. The occlusal surfaces of ten sound human molars were used in this in-vitro study. Shallow simulated caries lesions of varying depth and position were produced on tooth occlusal surfaces using a demineralization solution. Sequential NIR reflectance images at 1500 - 1700 nm were used to guide the laser for selective ablation of the lesion areas. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess the selectivity of removal. This study demonstrates that high contrast NIR reflectance images can be used for the image-guided laser ablation of early demineralization from tooth occlusal surfaces.

Abstract 4936: Tumor PaintTM technology detects naturally occurring solid tumors in dogs

Abstract Tumor PaintTM technology is designed to provide real-time visualization of tumors during surgery at improved resolution over existing methods. BLZ-100 is a Tumor Paint product consisting of a chlorotoxin (CTX) peptide conjugated to a near-infrared (NIR) fluorophore that is being advanced toward clinical studies. CTX-based Tumor Paint products have been shown to illuminate a broad range of cancers in mouse models. To facilitate clinical translation, a preclinical feasibility study was conducted in dogs with naturally occurring solid tumors. Many types of canine tumors resemble human disease, including sarcomas, mammary and lung cancers, mucosal squamous cell cancers, and gliomas. The diversity of tumor size and type, surrounding tissue, and patient body mass provides a model that is superior to the mouse in predicting the clinical characteristics of BLZ-100, including tumor penetration, background staining, and effective imaging dose. Twenty-seven dogs were given BLZ-100 intravenously 24 - 48 hours before surgery. Doses, normalized to body surface area (mg/m2), were 0.25 - 0.8 (7 dogs), 0.8 - 1.2 (15 dogs) and 1.2 - 1.6 (5 dogs). Tumor types were sarcoma, adenocarcinoma, mastocytoma, squamous cell carcinoma, and meningioma. Dogs received standard of care including tumor resection with intent to control or cure local disease. Excised tissues were imaged using the IVIS Spectrum (Caliper) and the Odyssey NIR scanner (Li-Cor) to determine overall signal in tumor and gross tumor to normal ratios. Tissues were then embedded in OCT, sectioned on a cryostat, and scanned on the Odyssey. Serial sections were stained with H&amp;E, and comparison with the fluorescence scans was used to validate the specificity of BLZ-100 for tumor tissue. Ex vivo imaging data showed maximal tumor fluorescence at doses above 0.9 mg/m2. In dogs treated with 0.8 mg/m2 or higher (20 dogs in total), ratios of fluorescence in tumour to normal surrounding tissue ranged from &amp;lt;1 (no specific signal, 2 dogs) to &amp;gt;200, with good differentiation in several tumor types including meningioma, carcinomas (lung, thyroid, and mammary), and sarcomas. Highest signals and gross tumor to background ratios were seen in a subset of soft tissue sarcomas, suggesting preferential uptake of the conjugate in these tumor types. Histologic analysis of these cases showed 95% sensitivity and 85% specificity. Intraoperative imaging was conducted in several cases, using a prototype open NIR imaging device. These cases showed good contrast between gross tumors and surrounding structures, detection of tumor through 0.5 cm of normal fatty tissue, and low background in tissues such as fat and muscle. The information obtained in this study provides data that will be valuable in clinical translation of BLZ-100. This project was funded in whole with Federal funds from National Cancer Institute, National Institutes of Health, Department of Health and Human Services, under Contract No. HHSN2612012000054C. Citation Format: William S. Dernell, Janean Fidel, Katie Kennedy, Stacey Hansen, Valorie Wiss, Mark Stroud, Julia E. Parrish-Novak. Tumor PaintTM technology detects naturally occurring solid tumors in dogs. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4936. doi:10.1158/1538-7445.AM2014-4936

The use of a microscope with near-infrared imaging function in indocyanine green lymphography and lymphaticovenous anastomosis

Indocyanine green (ICG) lymphography has become an important investigation in lymphaticovenous anastomosis (LVA). Near-infrared (NIR) imaging systems are available in the market for the production of ICG lymphography. These machines, however, may be difficult to obtain owing to their costs. In our institute, these NIR imaging devices are not available. Alternatively, microscopy with NIR imaging function was used for LVA. The experiences of the production of ICG lymphography with an NIR microscope are described. For the production of preoperative ICG lymphography, ICG solution was injected subdermally to the web spaces of the lymphoedema limb. The NIR mode of the microscope was used for the lymphatic mapping. Black and white images and videos of the ICG lymphography were then produced. Intra-operatively, the NIR function was used for the localisation of lymphatic vessels and confirmation of the patency of the LVA. Between February 2013 and May 2013, 24 ICG lymphographies were performed in 20 female patients as a preoperative investigation for LVA. All four ICG lymphography patterns (linear, splash, stardust and diffuse patterns) were demonstrated. In institutes where NIR imaging devices are not available, we believe that a microscope with an NIR imaging function is a reasonable alternative for the production of ICG lymphography.

A prospective pilot clinical trial evaluating the utility of a dynamic near-infrared imaging device for characterizing suspicious breast lesions

IntroductionCharacterizing and differentiating between malignant tumors, benign tumors, and normal breast tissue is increasingly important in the patient presenting with breast problems. Near-infrared diffuse optical imaging and spectroscopy is capable of measuring multiple physiologic parameters of biological tissue systems and may have clinical applications for assessing the development and progression of neoplastic processes, including breast cancer. The currently available application of near-infrared imaging technology for the breast, however, is compromised by low spatial resolution, tissue heterogeneity, and interpatient variation.Materials and methodsWe tested a dynamic near-infrared imaging schema for the characterization of suspicious breast lesions identified on diagnostic clinical ultrasound. A portable handheld near-infrared tissue imaging device (P-Scan; ViOptix Inc., Fremont, CA, USA) was utilized. An external mechanical compression force was applied to breast tissue. The tissue oxygen saturation and hemoglobin concentration were recorded simultaneously by the handheld near-infrared imaging device. Twelve categories of dynamic tissue parameters were derived based on real-time measurements of the tissue hemoglobin concentration and the oxygen saturation.ResultsFifty suspicious breast lesions were evaluated in 48 patients. Statistical analyses were carried out on 36 out of 50 datasets that satisfied our inclusion criteria. Suspicious breast lesions identified on diagnostic clinical ultrasound had lower oxygenation and higher hemoglobin concentration than the surrounding normal breast tissue. Furthermore, histopathologic-proven malignant breast tumors had a lower differential hemoglobin contrast (that is, the difference of hemoglobin concentration variability between the suspicious breast lesion and the normal breast parenchyma located remotely elsewhere within the ipsilateral breast) as compared with histopathologic-proven benign breast lesions.ConclusionThe proposed dynamic near-infrared imaging schema has the potential to differentiate benign processes from those of malignant breast tumors. Further development and refinement of the dynamic imaging device and additional subsequent clinical testing are necessary for optimizing the accuracy of detection.

Clinical utilization of near‐infrared spectroscopy devices for burn depth assessment

The diagnosis of burn depth is based on a visual assessment and can be subjective. Near-infrared (NIR) spectroscopic devices were used preclinically with positive results. The purpose of this study was to test the devices in a clinical setting using easily identifiable burn wounds. Adult patients with acute superficial and full-thickness burns were enrolled. NIR point spectroscopy and imaging devices were used to collect hemodynamic data from the burn site and an adjacent unburned control site. Oxy-hemoglobin and deoxy-hemoglobin concentrations were extracted from spectroscopic data and reported as oxygen saturation and total hemoglobin. Sixteen patients (n=16) were included in the study with equal numbers in both burn wound groups. Point spectroscopy data showed an increase in oxygen saturation (p<0.0095) and total hemoglobin (<0.0001) in comparison with the respective control areas for superficial burn wounds. The opposite was true for full-thickness burns, which showed a decrease in oxygenation (p<0.0001) and total hemoglobin (p<0.0147) in comparison with control areas. NIR imaging technology provides an estimate of hemodynamic parameters and could easily distinguish superficial and full-thickness burn wounds. These results confirm that NIR devices can successfully distinguish superficial and full-thickness burn injuries.

039 Determination of Burn Depth using near Infrared Spectroscopy

Introduction: Burn depth, based on the hemodynamic alterations that occur following a thermal insult, can be assessed in a rapid, non‐invasive, and nondestructive fashion using near infrared (NIR) spectroscopy. NIR has the capability to determine the difference between superficial and full thickness burn injuries. Methods: Sixteen burn patients admitted to an adult regional burn center were studied and evaluated with the NIR point and imaging devices. Non‐burned skin adjacent to the burn site was used as the control. NIR measurements were compared between superficial (8 wounds), full thickness (8 wounds) burn wounds and control sites. Results: NIR was able to easily detect an increase in oxyhemoglobin (68.3%, p &lt; 0.05), oxygen saturation (4.8%, p &lt; 0.05%) and total hemoglobin (91.3%, p &lt; 0.05) which typically occurs with superficial burn injuries. Full thickness injuries experienced a substantial drop in oxyhemoglobin (88.8%, p &lt; 0.05), oxygen saturation (79.1%, p &lt; 0.05) and total hemoglobin (77.5%, p &lt; 0.05) in comparison to control sites. Conclusions: These results confirm that NIR spectroscopy can successfully distinguish between superficial and full thickness burn injuries. The second phase of this study will involve determining the depth of indeterminant burn wounds and this preliminary data will also be presented. Acknowledgement: National Research Council of Canada

Regional difference of muscle oxygen saturation and blood volume during exercise determined by near infrared imaging device.

Using a near infrared (NIR) imaging device, we tested the hypothesis that regional differences in oxygen status could be detected in the gastrocnemius muscle during exercise and recovery. Six healthy subjects performed the standing plantar flexion exercises for 2 min; the frequency was one contraction per second. The NIR imaging device was placed over the medial head of the right gastrocnemius muscle and the signals from two optical sensors situated on the middle proximal and middle distal portions were used. The NIR-O(2) saturation (difference between deoxygenated and oxygenated Hb signals) and NIR-blood volume (sum of the oxygenated and deoxygenated Hb signals) were calculated in optical density units. Plantar flexion resulted in more deoxygenation during exercise and more reoxygenation during recovery in the distal portion compared with the proximal portion. The changes in NIR-O(2) between rest and a 2 min exercise, and between a 2 min exercise and a 3 min recovery were 0.11 and -0.23, respectively, in the distal portion, which were significantly larger than proximal values (0.05 and -0.10, p < 0.05). Plantar flexion resulted in lower NIR-blood volumes during exercise and greater recovery of blood after exercise in the distal portion compared with the proximal portion. The changes in NIR blood volume between rest and a 2 min exercise and between a 2 min exercise and a 3 min recovery were -0.19 and 0.31, respectively, in the distal portion, significantly larger than proximal values (-0.07 and 0.12, p < 0.05 for all comparisons). These findings indicate that the distal portion of the medial gastrocnemius had larger changes in NIR-O(2) saturation and NIR-blood volume than the proximal portion had. This is consistent with the distal portion having a greater impairment of blood flow possibly because of the higher intramuscular pressure during exercise. (1) regional differences in oxygen status in the gastrocnemius muscle were detected with exercise, with the distal portion having greater NIR-O(2) saturation and NIR-blood volume changes, and (2) the NIR imaging device might be a useful method to detect the regional differences of oxygen status in the muscle.

Non-invasive optical spectroscopy and imaging of human brain function

Brain activity is associated with changes in optical properties of brain tissue. Optical measurements during brain activation can assess haemoglobin oxygenation, cytochrome- c-oxidase redox state, and two types of changes in light scattering reflecting either membrane potential (fast signal) or cell swelling (slow signal), respectively. In previous studies of exposed brain tissue, optical imaging of brain activity has been achieved at high temporal and microscopical spatial resolution. Now, using near-infrared light that can penetrate biological tissue reasonably well, it has become possible to assess brain activity in human subjects through the intact skull non-invasively. After early studies employing single-site near-infrared spectroscopy, first near-infrared imaging devices are being applied successfully for low-resolution functional brain imaging. Advantages of the optical methods include biochemical specificity, a temporal resolution in the millisecond range, the potential of measuring intracellular and intravascular events simultaneously and the portability of the devices enabling bedside examinations.

Evaluation of system performance of near-infrared imaging devices

Abstract A method is described for the evaluation of the performance of near-infrared imaging devices to detect underdrawing and reworking of paintings. System analyses have been performed on two different ' near-infrared imaging devices: a Hamamatsu lead sulphide vidicon camera and a Photometries silicon charge coupled device (CCD) camera. The analyses included modelling of the system spectral response curve by analysis of the system components, as well as considering the limiting resolution and modulation transfer function (MTF). The modelling was confirmed by examination of a test panel at various wavelengths. Calculation of visibility is introduced as a quantitative measure of system performance. This calculation is also discussed as a means to define more clearly the actual performance requirements of these systems. This analysis has revealed the strengths and weaknesses of current systems, and provides guidance in the construction of improved devices.

Evaluation of System Performance of Near-Infrared Imaging Devices

Evaluation of System Performance of Near-Infrared Imaging Devices