Using Optical Coherence Tomography to Evaluate Skin Sun Damage and Precancer

Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that produces cross-sectional images of tissue morphology with a high resolution. We used OCT to statistically evaluate the degree of skin sun damage and identify pre-cancerous lesions. OCT images shown below are of undiseased skin on the lateral forearm (Figure 1) and an actinic keratosis (AK) on the lateral forearm (Figure 2). Statistically significant differences (p < 0.0001) were found between severe and minimal degrees of sun damage, and in undiseased versus AK sites.

Figure 1 (left) : Example OCT image of minimal sun damaged lateral forearm of a 56 year old female. S = stratum corneum, E = epidermis, D = dermis.

Figure 2 (right) : Example OCT image of an AK with a very thick keratin layer on the lateral forearm of a 77 year old male. This image has significant vertical shadowing caused by skin flakes. E = epidermis, D = dermis. Arrow points to keratinized region.

Evaluating Methemoglobin as a Magnetic Resonance Imaging Contrast Agent

 Pulsed laser irradiation of blood converts oxyhemoglobin to methemoglobin with high efficiency. Methemoglobin is paramagnetic, and has the potential to act as a natural contrast agent, reducing side effects and toxicity concerns. We created samples with varying concentrations of oxyhemoglobin and methemoglobin using sodium nitrite and with a 532 nm, 10 ms pulsed laser. T1 and T2 weighted MRI signal enhancement in vitro from methemoglobin were evaluated (Figures 3 and 4) showing a maximum signal increase of over 330% and signal decrease to essentially zero, respectively.

Figure 3 (left): Percent signal increase of met-Hb-containing intact RBC relative to untreated RBC in isotonic saline suspension as function of % Hb in the met-form, and imaging parameters. Results of T1 weighted imaging with TE = 6.4 ms and TR = 83.2 ms, 643.2 ms, 1203.2 ms.

Figure 4 (right): Percent signal decrease of met-Hb-containing intact RBC relative to untreated RBC in isotonic saline suspension as a function of % Hb in the met-form, and imaging parameters. Reults of T2 weighted imaging, TR = 20 sec and TE = 15 ms, 30 ms, and 75 ms.

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