Objective: Venous leg ulcers (VLUs) are one of the most common complications in lower extremity wounds. To date, clinicians employ visual inspection of the wound site during its healing process by monitoring surface granulation and reduction in wound size across weeks of treatment. In this study, a handheld near-infrared optical scanner (NIROS) has been developed at the Optical Imaging Laboratory to differentiate healing from nonhealing VLUs based on differences in blood flow to the wound and its surroundings. Approach: Noncontact near-infrared (NIR) area imaging of 12 VLUs have been carried out at two podiatric clinics. Diffuse reflectance images of the wounds were used to quantify optical contrasts between the wound and its surroundings. The variability in imaging conditions, analysis, and operator dependency were assessed to determine the robustness of the imaging approach. Results: Optical contrast obtained from diffuse reflectance images of VLUs were distinctly different for healing (positive contrast) and nonhealing (negative contrast) wounds, independent of the varying imaging and data analysis conditions. Innovation: NIR imaging of wounds to differentiate healing from nonhealing VLUs using a noncontact wide-area imager has been demonstrated for the first time. Conclusion: The application of a portable handheld imager to assess the healing or nonhealing nature of VLUs during weekly clinical treatment is significant since physiological changes, as observed using NIROS, manifest before visual reduction in wound size during the healing process.
The complementary information provided by combined MRI-PET modalities promises to facilitate metabolic investigations of complex physiological processes. We developed a radio frequency (RF) coil array that can operate in close proximity (2-mm radial distance) to a miniaturized PET camera insert for simultaneous PET-MRI of a rat brain at high magnetic fields (4 Tesla). All ferromagnetic components in the PET instrument were replaced with non-ferromagnetic components to minimize susceptibility artefacts in MRI, and optical fibres were used to connect the electronics of the PET camera to the acquisition system located outside the MRI scanner room. A passive electromagnetic shielding was developed to minimize the interference between the PET-electronics and MRI RF coil array. MR images of water phantoms and "ex-vivo" rat brains were collected in two different conditions: with and without PET acquisition. Similarly, PET data was acquired in two different conditions: with and without MRI pulses (RF and gradients). The MR images showed good uniform sensitivity profiles for all cases and 66% decrease in SNR for the shielded case. The PET and MRI datasets demonstrated that the electromagnetic shielding successfully minimizes the RF interference between the instruments, minimizing MRI artefacts and protecting the delicate components of the PET electronics from MRI RF pulses.
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