High-dose laser exposure to tissue causes thermal damage and significant changes in tissue optical properties. Samples of porcine dermis and subcutaneous fat were immersed in a temperature-controlled water bath to induce a range of thermal damage. Temperature history was recorded to quantify the damage with the Arrhenius integral. Samples were then measured in a double integrating sphere setup and optical coefficients computed using the inverse adding doubling method. The tissues demonstrate non-monotonic changes in optical properties with respect to induced thermal damage. These results will inform medical scenarios and computational models where optical interaction with damaged tissues is expected.
In this paper, we explore the use of low-light image enhancement as a preprocessing step to improve the quality of novel view synthesis by Neural Light Fields (NeLF). NeLF is a 3D scene representation method that employs a light field representation, differing from prior methods based on volumetric rendering schemes. One of the main advantages of NeLF is its faster rendering speed, as it requires only one network forward pass without Ray marching. However, NeLF struggles to model low-illumination scenes due to its viewer-centered framework, which does not consider the interaction between illumination and scenes. To address this issue, we propose the use of 2D low-light image enhancement as a preprocessing solution. Our approach utilizes the Alpha-rooting by 2-D DFT as a preprocessing step to enhance low-light images prior to their use by the NeLF model. We demonstrate that this approach leads to significant improvements in the quality of novel view synthesis by NeLF on low-light images. We also consider how this can have practical applications in various domains such as applied human biomechanics.
Accurate values of the optical properties of skin and subcutaneous fat are important for a variety of applications, such as optical imaging techniques and computational modeling of possible hazardous laser exposure. Several studies are available in the published literature that report skin optical properties, but the method of tissue preparation and storage in these experiments can be variable. These methods include the application of some form of cold storage, such as refrigeration or freezing, which may in turn affect the optical properties of the tissues compared to the in vivo or freshly excised case. We measured the absorption and scattering coefficients of skin and subcutaneous fat samples prior to and following various methods of cold storage, particularly refrigeration, slow freezing, and flash freezing. Tissues were collected from two subjects in order to capture biological variability. We employed a double integrating sphere setup and the inverse adding-doubling method to determine optical properties. The results of this investigation will help contextualize existing studies on tissue optical properties and enable informed procedural design for future measurements.
Accurate values of the optical properties of skin and subcutaneous tissues are critical for a variety of applications, such as optical imaging techniques and computational modeling of possible hazardous laser exposure. Several studies are available in the published literature that report skin optical properties, but the method of tissue preparation and storage in these experiments can be variable, ranging from measurement immediately after excision, to undergoing some form of cold storage, such as refrigeration or freezing. The degree to which cold storage affects the optical properties of skin tissues is unknown. We measured the absorption and reduced scattering coefficients of skin and subcutaneous tissues that underwent refrigeration and slow freezing, and compared them to freshly excised samples. Tissues were collected from several subjects in order to capture biological variability. We employed a goniometric spectrophotometer setup and a Monte Carlo light propagation method to determine optical properties. The results of this investigation will help contextualize existing studies on tissue optical properties and enable informed procedural design for future measurements.
Bladder cancer is the fourth most common cancer in men and is considered to have the highest rate of recurrence of all cancers at ~70%, and transitional cell carcinoma (TCC) is the most common form of intrabladder malignancy. Current standard-of-care for Stages 2 or higher is radical cystectomy, which involves removal of the urinary bladder and nearby lymph nodes. Alternative, organ-sparing treatments such as chemo- or radiotherapy are relatively ineffective against these cancers. The latter is effective when precisely targeted, but suffers from accuracy issues due to low contrast from computed tomography guidance. These motivate an innovative approach to more precisely visualize and spatially pinpoint TCC. This manuscript presents a novel non-invasive computer vision pipeline that can extract 3D structural information from 2D images obtained during routine flexible cystoscopy. The pipeline utilized camera calibration, adaptive thresholding, Scale Invariant Feature Transform (SIFT), and a Structure from Motion (SFM) implementation to reconstruct 3D point clouds of the inner surface of organ phantoms and an ex vivo porcine bladder. 3D point clouds were processed by Poisson reconstruction to generate a textured, triangle meshed 3D surface. The reconstruction pipeline generated a visually recognizable, qualitative 3D representation of the bladder from 2D video captured via flexible cystoscopy. Once further developed, this approach will enhance the targeting precision of external beam radiotherapy, providing clinicians with better organ-sparing methods to treat TCC.
This paper describes a new infusion catheter, based on our fiberoptic microneedle device (FMD), designed with the objective of photothermally augmenting the volumetric dispersal of infused therapeutics. We hypothesize that concurrent delivery of laser energy, causing mild localized photothermal heating (4-5 °C), will increase the spatial dispersal of infused chemotherapy over a long infusion period. Agarose brain phantoms, which mimic the brain’s mechanical and fluid conduction properties, were constructed from 0.6 wt% Agarose in aqueous solution. FMDs were fabricated by adhering a multimode fiberoptic to a silica capillary tube, such that their flat-polished tips co-terminated. Continuous wave 1064 nm light was delivered simultaneously with FD&C Blue #2 (5%) dye into phantoms. Preliminary experiments, where co-delivery was tested against fluid delivery alone (through symmetrical infusions into in vivo rodent models), were also conducted. In the Agarose phantoms, volumetric dispersal was demonstrated to increase by more than 3-fold over a four-hour infusion time frame for co-delivery relative to infusion-only controls. Both forward and backward (reflux) infusions were also observed to increase slightly. Increased volumetric dispersal was demonstrated with co-delivery in an in vivo rodent model. Photothermal augmentation of infusion was demonstrated to influence the directionality and increase the volume of dye dispersal in Agarose brain phantoms. With further development, FMDs may enable a greater distribution of chemotherapeutic agents during CED therapy of brain tumors.
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