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Whether the depth and healing of scalds and contact burns are similar is controversial. Due to water's greater heat capacity, we hypothesized that when exposed to similar temperatures and durations of exposure, burns caused by hot water would be deeper than those caused by contact with hot metal. Forty standardized burns were created in two anesthetized female domestic pigs using a brass bar or circulating heated water. In one pig, the temperature was kept constant (95°C) while the duration of exposure varied (5, 10, 15 seconds) In the second pig, the exposure time was kept constant (10 seconds) while the temperature of exposure varied (70°C, 80°C, 98°C). Periodic punch biopsies were taken to determine burn depth immediately after injury, percentage burns reepithelialized within 21 days, and depth of scar at 28 days. The analysis was performed using analysis of variance. When the temperature was held constant, duration of exposure (5, 10, and 15 seconds) was associated with scar depth (2.1 vs 3.8 vs 5.0 mm, respectively, P = 0.001) but not with burn depth (2.0 vs 2.2 vs 2.3 mm, respectively, P = 0.10). When exposure duration was held constant, temperature (70°C, 80°C, 98°C) was associated with scar depth (0.6 vs 1.7 vs 3.6, P < 0.001) but not with burn depth (1.2 vs 1.5 vs 1.7 mm, respectively, P = 0.21). Burn depths were greater for scald than contact burns although not significantly greater. After controlling for temperature, the difference in scar depth between scalds and contact burns was statistically significant (marginal means 3.0 for contact burns, 4.3 for scalds, P = 0.008). We conclude that burns created in swine with circulating hot water result in deeper scars than those created by contact with a brass bar when controlling for temperature and duration of exposure.

Patients arrive in burn centers with many etiologies of burn incidence (such as scald, contact, flame, steam, etc.). Treatment of these injuries depends on the burn depth and surface area of these burns. Moreover, earlier diagnosis and treatment of these burns lead to better patient outcomes. In this study, we show that THz-TDS imaging with a neural network classification algorithm can reproducibly classify burns, independent of their etiology, with an ROC-AUC of 88% in a porcine model.

Topographical abnormality in corneal tissue is a common diagnostic marker for many eye diseases and injuries. Using an asynchronous optical sampling terahertz time-domain spectroscopy setup, we developed a non-contact and normal-incidence imaging system to measure topographic changes along the surface of spherical samples. We obtained orthogonal 1D scans of calibration spheres to evaluate the minimum axial resolution of our system. We determined the axial and spatial resolution of the scanner using 3D-printed spherical cross and Boehler star targets. Furthermore, we characterized the asymmetrical performance of the scanner due to the use of an off-axis parabolic mirror. Finally, we developed an edge-detection filter to aid with improving the topographic scans. We showed that when imaging samples were comparable in size to the human cornea, the axial and spherical spatial resolutions were limited to about 15 µm ( ∼ λ / 67 ) and 1 mm, respectively.

Dielectric heterogeneity in addition to wavelength-scale air voids and granular particles lead to significant electromagnetic scattering in the transmission-mode THz-TDS. These scattering processes result in the distorted or obscured resonant signatures, a frequency-dependent extinction loss, and the appearance of anomalous spectral artifacts, imposing severe challenges on the real-world automatic material characterization schemes. In this work, we use a combination of the wavelet multiresolution analysis, the principal component analysis, and the bimodality coefficient to simultaneously identify all the resonant frequencies of a heterogeneous sample embedded beneath a highly scattering turbid medium.

THz imaging is a promising modality to improve the standard-of-care for patients with partial thickness burn injuries. In this study, we show the accuracy and efficacy of THz-TDSI for characterizing and monitoring burn wounds in a porcine model. We show that our new THz hyperspectral metric, $Z$ , can differentiate between partial-thickness burns against their histologically determined depths of injury ( $p ).

Terahertz imaging often involves seeing through inhomogeneous and highly scattering media. We propose a wavelet multiresolution analysis approach to mitigate the scattering effects and produce highly-resolved reflection spectral images for chemical mapping through turbid media.

The accuracy of current burn triage techniques has remained between 50-70%. Accordingly, there is a significant clinical need for the quantitative and accurate assessment of partial-thickness burn injuries. Porcine skin represents the closest animal model to human skin, and is often used in surgical skin grafting procedures. In this study, we used a standardized in vivo porcine burn model to obtain terahertz (THz) point-spectroscopy measurements from burns with various severities. We then extracted two reflection hyperspectral parameters, namely spectral area under the curve between approximately 0.1 and 0.9 THz (−10 dB bandwidth in each spectrum), and spectral slope, to characterize each burn. Using a linear combination of these two parameters, we accurately classified deep partial- and superficial partial-thickness burns (p = 0.0159), compared to vimentin immunohistochemistry as the gold standard for burn depth determination.

We report on the development and performance characterization of a telecentric terahertz spectroscopic scanner using an f-θ objective lens and a single gimballed scanning mirror for image formation. We derived a beam steering transform to compensate for the intercoupling of the gimballed mirror axes and the distortions caused by an imperfect scanning lens. We characterize the optical performance of the system in both the time and spatial domains, demonstrating a constant diffraction-limited imaging resolution over the entire field of view. Finally, given the large depth of focus of the objective lens, we demonstrate the broadband imaging capability at different depths using a Boehler star target. This imaging setup has the potential to be miniaturized into portable form factors for field-deployable scenarios.

Terahertz (THz) imaging is a widely used technique in the study and detection of many chemicals and biomolecules in polycrystalline form because the spectral absorption signatures of these target materials often lie in the THz frequencies. When the size of dielectric grain boundaries are comparable to the THz wavelengths, spectral features can be obscured due to electromagnetic scattering. In this study, we first investigate this granular scattering effect in identification of chemicals with THz spectral absorption features. We then will propose a signal processing technique in the so-called "quefrency" domain to improve the ability to resolve these spectral features in the diffuse scattered THz images. We created a pellet with α-lactose monohydrate and riboflavin, two biologically significant materials with well-known vibrational spectral resonances, and buried the pellet in a highly scattering medium. THz transmission measurements were taken at all angles covering the half focal plane. We show that, while spectral features of lactose and riboflavin cannot be distinguished in the scattered image, application of cepstrum filtering can mitigate these scattering effects. By employing our quefrency-domain signal processing technique, we were able to unambiguously detect the dielectric resonance of lactose in the diffused scattering geometries. Finally we will discuss the limitation of the new proposed technique in spectral identification of chemicals.

Introduction Whether the depth and healing of scalds and contact burns are similar is controversial. Prior studies have not compared scalds and contact burns using identical temperatures and durations of exposure limiting direct comparison. We hypothesized that when exposed to similar temepratures and durations of exposure, burns caused by hot water and contact with hot metal would be similar. Methods Multiple 2.5 or 5 cm diameter standardized cutaneous burns were created in two anesthetized female domestic pigs (~45kg) using a brass bar or circulating heated water in replicates. The temperatures were controlled and kept constant using thermosensors. In one pig, the temperature was kept constant (95 degrees C) while the duration of exposure varied (5, 10, 15 sec.) In the second pig, the exposure time was kept constant (10 sec.) while the temperature of exposure varied (70, 80, 98 degrees C). Burns were covered with a topical antibiotic ointment and frequent dressing changes were performed for 4 weeks. Periodic punch biospies were taken to determine burn depth immediately after injury, percentage burns reepithelialized within 21 days, and depth of scar at 28 days. Analysis was performed using analysis of variance. Results When temperature was held constant, duration of exposure (5, 10, and 15 sec.) was associated with scar depth (2.1 vs 3.8 vs 5.0 mm respectively, P=0.001) and there was a trend for an association with burn depth (2.0 vs 2.2 vs 2.3 mm respectively, P=0.10). When exposure duration was held constant, temperature (70, 80, 98 degrees C) was associated with scar depth (0.6 vs 1.7 vs 3.6, P< 0.001) but not significantly associated with burn depth (1.2 vs 1.5 vs 1.7 mm respectively, P=0.21). For each pig a comparison of burn and scar depth by device generally showed that depths were greater for scald than contact burns although not significantly greater. Only scar depth in the first pig showed a difference with a significance of less than 0.10 (2.9 for contact vs 4.1 mm for scalds, P=0.08). After controlling for temperature the difference between scalds and contact burns was statistically significant (marginal means 3.0 for contact burns, 4.3 for scalds, P=0.008). When combining data from both pigs and controlling for temperatures and duration, scar depths for scalds (2.7 mm) vs contacts (1.9 mm) showed a significant difference (P=0.02) while burn depth was not quite significant (1.7 vs 1.5 mm, P=0.07). Almost all burns were reepithelialized by day 21. Conclusions Burns created in swine with circulating hot water tend to be deeper and result in deeper scars than those created by contact with a brass bar when controlling for temperature and duration of exposure. Applicability of Research to Practice Scalds of similar temperature and exposure times result in deeper scars than contact burns.

Perturbation of normal corneal water content is a common manifestation of many eye diseases. Terahertz (THz) imaging has the potential to serve as a clinical tool for screening and diagnosing such corneal diseases. In this study, we first investigate the diffusive properties of a corneal phantom using simultaneous THz time-domain spectroscopy (THz-TDS) and gravimetric measurements. We will then utilize a variable-thickness diffusion model combined with a stratified composite-media model to simulate changes in thickness, hydration profile, and the THz-TDS signal as a function of time. The simulated THz-TDS signals show very good agreement with the reflection measurements. Results show that the THz-TDS technique can be used to understand water diffusion dynamics in corneal phantoms as a step towards future in vivo quantitative hydration sensing.

We demonstrate the application of THz-TDS in characterizing the severity of burn injuries in a live animal model. 2nd and 3rd degree burns were studied immediately and 72 hours post-burn. A new diagnosis criterion was verified against histopathology.

A diagnosis criterion is proposed for noninvasive grading of burn injuries using terahertz radiation. Experimental results are presented from in vivo terahertz time-domain spectroscopy of second- and third-degree wounds, which are obtained in a 72-hour animal study. During this period, the change in the spectroscopic response of the burned tissue is studied. It is shown that terahertz waves are sensitive not only to the postburn formation of interstitial edema, but also to the density of skin structures derived from image processing analysis of histological sections. Based on these preliminary results, it is suggested that the combination of these two effects, as probed by terahertz spectroscopy of the tissue, may ultimately be used to differentiate partial-thickness burns that will naturally heal from those that will require surgical intervention.