Efficacy of Methylene Blue Photodynamic Therapy for Treatment of Deep Tissue Abscesses

Administration of 0.1 mg/mL methylene blue to the abscess cavity, followed by a 10 minute incubation interval. After this incubation interval, the methylene blue solution will be aspirated from the cavity and flushed twice with sterile saline.

The abscess cavity will be filled with sterile 0.1% lipid emulsion solution to gently distend the cavity and, through efficient light scattering, to homogenize the light dose to the walls of the cavity. After laser illumination, the Intralipid will be aspirated from the cavity.

A sterile, FDA-approved optical fiber will be advanced to the approximate center of the abscess cavity via the drainage catheter under image guidance. Following laser illumination, the fiber will be withdrawn.

Laser illumination will be delivered via the optical fiber for a duration of 20 minutes. The optical power will be set such that the fluence rate at the abscess wall due to ballistic photons is 20 mW/cm2.

The same sterile optical fiber used for treatment will be advanced through the drainage catheter/needle in order to make gentle contact with the wall of the cavity. Low-intensity, polarized white light will be delivered by a tungsten halogen lamp by the fiber, and captured by the same fiber. Light that has been de-polarized by interaction with tissue will be detected by a spectrometer and analyzed to extract tissue optical properties. Upon completion of these measurements, the fiber optic will be withdrawn, gently wiped with sterile gauze, and returned to the procedure cart.

Laser illumination will be delivered via the optical fiber for a duration of 20 minutes. The optical power will be set to deliver a fluence rate of 20 mW/cm2 in 95% of the abscess wall, based upon abscess morphology and optical spectroscopy results.

Following standard practice, a drainage catheter will be placed in the abscess cavity and used to aspirate purulent fluid.