This study aims to understand the application of thermal imaging to detect inflammatory bowel disease. Active inflammation increases tissue temperature, dissipating through different tissue types and fecal matter. In this study, heat conduction in swine gastrointestinal tissue were investigated experimentally and matched to theoretical models to measure the tissue's thermal properties and compute the depth at which inflammation that can be diagnosed by thermography. First, we measured the tissue's thermal conductivity, density, and heat capacitance using thermal transient heat conduction analysis through biomaterials. Then, using thermal conductivity and steady-state analysis of heat diffusion, we estimated the temperature drop through different types of swine intestinal tissue to calculate the detection depth range of thermography. The temperature drop through these experiments shows that heat rise from inflammation in the bowel should be detectable with infrared endoscopy.
KEYWORDS: Dental caries, Teeth, Signal to noise ratio, 3D modeling, Tomography, Modulation, 3D image processing, Imaging systems, Thermography, Cameras
Significance: Dental caries is the most common oral disease, with significant effects on healthcare systems and quality of life. Developing diagnostic methods for early caries detection is key to reducing this burden and enabling non-invasive treatment as opposed to the drill-and-fill approach.
Aim: The application of a thermophotonic-based 3D imaging modality [enhanced truncated-correlation photothermal coherence tomography (eTC-PCT)] to early dental caries is investigated. To this end, the detection threshold, sensitivity, and 3D lesion reconstruction capability of eTC-PCT in imaging artificially generated caries and surface erosion are evaluated.
Approach: eTC-PCT employs a diode laser with pulsed excitation, a mid-IR camera, and an in-house developed image reconstruction algorithm to produce depth-resolved 2D images and 3D reconstructions. Starting with healthy teeth, dental caries and surface erosion are simulated in vitro through application of specific demineralizing/eroding acidic solutions.
Results: eTC-PCT can detect artificial caries as early as 2 days after onset of artificial demineralization and after 45 s of surface erosion, with a laser power equivalent to 64% of maximum permissible exposure. In both cases, the lesion is not visible to the eye and undetected by x-rays. eTC-PCT is capable of monitoring lesion progression in 2-day increments and generating 3D tomographic reconstructions of the advancing lesion.
Conclusions: eTC-PCT shows great potential for further development as a dental imaging modality combining low detection threshold, high sensitivity to lesion progression, 3D reconstruction capability, and lack of ionizing radiation. These features enable early diagnosis and frequent monitoring, making eTC-PCT a promising technology for facilitating preventive dentistry.
Photoacoustic imaging (PAI) has been proposed as a non-invasive technique for imaging neonatal brain injury. Since
PAI combines many of the merits of both optical and ultrasound imaging, images with high contrast, high resolution, and
a greater penetration depth can be obtained when compared to more traditional optical methods. However, due to the
strong attenuation and reflection of photoacoustic pressure waves at the skull bone, PAI of the brain is much more
challenging than traditional methods (e.g. near infrared spectroscopy) for optical interrogation of the neonatal brain. To
evaluate the potential limits the skull places on 3D PAI of the neonatal brain, we constructed a neonatal skull phantom
(1.4-mm thick) with a mixture of epoxy and titanium dioxide powder that provided acoustic insertion loss (1-5MHz)
similar to human infant skull bone. The phantom was molded into a realistic infant skull shape by means of a CNCmachined
mold that was based upon a 3D CAD model. To evaluate the effect of the skull bone on PAI, a photoacoustic
point source was raster scanned within the phantom brain cavity to capture the imaging operator of the 3D PAI system
(128 ultrasound transducers in a hemispherical arrangement) with and without the intervening skull phantom. The
resultant imaging operators were compared to determine the effect of the skull layer on the PA signals in terms of
amplitude loss and time delay.
Photoacoustic imaging (PAI) has been proposed as a non-invasive technique for the diagnosis and monitoring of
disorders in the neonatal brain. However, PAI of the brain through the intact skull is challenging due to reflection and
attenuation of photoacoustic pressure waves by the skull bone. The objective of this work was to develop a phantom for
testing the potential limits the skull bone places on PAI of the neonatal brain. Our approach was to make acoustic
measurements on materials designed to mimic the neonatal skull bone and construct a semi-realistic phantom. A water
tank and two ultrasound transducers were utilized to measure the ultrasound insertion loss (100 kHz to 5MHz) of several
materials. Cured mixtures of epoxy and titanium dioxide powder provided the closest acoustic match to neonatal skull
bone. Specifically, a 1.4-mm thick sample composed of 50% (by mass) titanium dioxide powder and 50% epoxy was
closest to neonatal skull bone in terms of acoustic insertion loss. A hemispherical skull phantom (1.4 mm skull
thickness) was made by curing the epoxy/titanium dioxide powder mixture inside a mold. The mold was constructed
using 3D prototyping techniques and was based on the hairless head of a realistic infant doll. The head was scanned to
generate a 3D model, which in turn was used to build a 3D CAD version of the mold. The mold was CNC machined
from two solid blocks of Teflon®. The neonatal skull phantom will enable the study of the propagation of photoacoustic
pressure waves under a variety of experimental conditions.
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