The optics of appearance

We are acquiring spectral images of faces to specify the optical parameters (blood, hydration, melanin, scattering) that affect appearance.

Evaluating laser treatment of port-wine stains in children

Port-wine stains (PWS) are treated by a laser to thermally cause thrombus formation (clots), which yields tissue ischemia (lack of oxygen) and elicits a wound healing response that removes the PWS. But often treatment is incomplete. We are using a spectral camera to image the ischemia after laser treatment of PWS to find areas where the clot has loosened (reperfusion) which re-established blood flow and oxygenation such that treatment fails. The goal is to allow the doctor to find regions that need additional touch-up treatment before the patient leaves the clinic.

Optical fibers can deliver light to remote sites within the body. White light is delivered by one fiber and light transmitted/reflected from the tissue is collected by a 2nd fiber and routed to a spectrometer. The spectrum, R(λ) is analyzed to specify the blood content and oxygen saturation of the tissue.

Interferometry can measure movements on the sub-nm scale. We use low-coherence light, achieved by a broad band of wavelengths, and lenses to restrict the interferometric measurement to a local region of interest.

Vibrations of inner ear cochlear membrane

An optical coherence tomography (OCT) system is used to image the cochlear membrane of the inner ear, the ribbon of tissue down which sound waves propagate. The noise floor is 30 pm vibration, and in vivo vibrations are typical 0.1-10 nm. Figure: The vibrations of the cochlear membrane, a thin 100-µm-thick ribbon stretched between two bone supports. OC = organ of Corti. RM = Riessner's membrane.

Clinical measurement of vibrations of middle ear structures

A similar OCT system is being developed as a hand-held otoscope to measure vibrations of the middle ear in the hearing clinic. Conductive hearing loss due to the ossicles (small ear bones) not properly moving in response to sound can be evaluated, without surgical violation of the typanic membrane. OCT can see through the typmanic membrane. Figure: TM = typmanic membrane. IN = incus. Ma = malleus.

Bedside pathology for imaging skin cancer during Mohs surgery

We are striving to change how Mohs surgery is conducted, by placing a bedside confocal microscope and developing a rapid staining protocol so that an image equivalent to an H&E stained biopsy can be acquired within 5 min. The Mohs surgeon could stay with the patient and finish multiple excisions of skin cancer, rather than leaving the patient waiting for 30-45 min waiting for histopathology to be done. The staining procedure stains nuclei with one fluorophore (image #1) and cytoplasm with another fluorophore (image #2), and uses reflectance to image collagen fiber bundles (image #3). Then the 3 images are false-colored and combined to yield a single picture that mimics an H&E stained specimen, which is the type of image the Mohs surgeon routinely uses. Figure: Left (c) is false color image of basal cell carcinoma in human patient. Right (d) is H&E stained biopsy (Dan Gareau).