Cerenkov luminescence (CL), optical radiation induced by PET radiotracers, has shown promise as a means to visualize tumor margins during surgery. However, detecting this faint optical signal under ambient lighting conditions represents a major challenge. We have developed an ambient light CL imaging system that uses a sensitive imaging detector, custom electronic control board, and an LED illumination array. By gating both LED illumination and imaging detector, we have demonstrated that is possible to image faint Cerenkov-emitting sources in a perceptually well-lit room, without harm to the sensitive detector.
System performance was characterized by imaging 18F radionuclide solution contained in 10 mm well plates, ranging in activity from >1 MBq to <1 kBq, under visible light conditions with irradiances ranging from 0 to >30 µW/cm2. Both detector and LED illumination were gated at 30 Hz with 10 ms active duty cycles. Contrast-to-noise ratio (CNR) was computed from ROIs drawn over activity-containing wells. Though CNR decreased with increasing illumination levels, an activity of 240 kBq, was unambiguously detectable with gated illumination of 37 µW/cm2 (equivalent to typical indoor light levels) and an activity of <24 kBq was unambiguously detectable with gated illumination of 2 µW/cm2. Furthermore, we have characterized sources of noise for the imaging system, which have provided insight into strategies for optimization in anticipation of use in an intraoperative setting.
Optical coherence tomography (OCT) is a minimally-invasive imaging modality capable of tracking the development of
individual colonic adenomas. As such, OCT can be used to evaluate the mechanisms and effectiveness of
chemopreventive and chemotherapeutic agents in colorectal cancer models. The data presented here represent part of a
larger study evaluating α-difluoromethylornithine (DFMO) and Sulindac as chemopreventive and chemotherapeutic
agents using mice treated with the carcinogen azoxymethane (AOM). 27 A/J mice were included in the chemoprevention
study, subdivided into four treatment groups (No Drug, DFMO, Sulindac, DFMO/Sulindac). 30 mm lateral images of
each colon at eight different rotations were obtained at five different time points using a 2 mm diameter spectral domain
OCT endoscopy system centered at 890 nm with 3.5 μm axial resolution in air and 5 μm lateral resolution. Images were
visually analyzed to determine number and size of adenomas. Gross photos of the excised colons and histology provided
gold standard confirmation of the final imaging time point. Preliminary results show that 100% of mice in the No Drug
group developed adenomas over the course of the chemoprevention study. Incidence was reduced to 71.43% in mice
given DFMO, 85.71% for Sulindac and 0% for DFMO/Sulindac. Discrete adenoma size did not vary significantly
between experimental groups. Additional experiments are currently under way to verify these results and evaluate
DFMO and Sulindac for chemotherapeutic applications.
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