The maturation process of the feline cornea proceeds over the first 1-2 years of life to attain an adult status that is characterized by a roughly spherical state of approximately 39 D corneal curvature, substantially flatter than the human cornea, and a central thickness similar to the human cornea. Research studies of the refractive or optical properties of the cornea in which cats are used as experimental animals should be conducted on animals greater than 18 months of age.

Recent advances in nanotechnology have allowed for the effective use of iron oxide nanoparticles (IONPs) for cancer imaging and therapy. When activated by an alternating magnetic field (AMF), intra-tumoral IONPs have been effective at controlling tumor growth in rodent models. To accurately plan and assess IONP-based therapies in clinical patients, noninvasive and quantitative imaging technique for the assessment of IONP uptake and biodistribution will be necessary. Proven techniques such as confocal, light and electron microscopy, histochemical iron staining, ICP-MS, fluorescent labeled mNPs and magnetic spectroscopy of Brownian motion (MSB), are being used to assess and quantify IONPs in vitro and in ex vivo tissues. However, a proven noninvasive in vivo IONP imaging technique has not yet been developed. In this study we have demonstrated the shortcomings of computed tomography (CT) and magnetic resonance imaging (MRI) for effectively observing and quantifying iron/IONP concentrations in the clinical setting. Despite the poor outcomes of CT and standard MR sequences in the therapeutic concentration range, ultra-short T2 MRI methods such as, Sweep Imaging With Fourier Transformation (SWIFT), provide a positive iron contrast enhancement and a reduced signal to noise ratio. Ongoing software development and phantom and in vivo studies, will further optimize this technique, providing accurate, clinically-relevant IONP biodistribution information.

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In order to better understand light dosimetry issues for photodynamic therapy (PDT), we have used various tumor and normal tissue geometries to develop a diffusion model of light transport in tissues. We hypothesize that tumor tissues with curved surfaces will have significantly different internal fluence distributions, as compared to tissues with flat surfaces. Using a mouse subcutaneous tumor and rear limb muscle model we compared the internal fluence values within the tissue. In addition, numerical simulations for these corresponding tissue geometries and laser light incidence angles were made. Assuming that the relative photon fluence in the tissue can be accurately modeled by the diffusion equation, we used a finite element approach to approximate the distribution inside the tissue. Meshes with different geometries (flat and curved with different curvatures) were used in this study to mimic the tumor and leg geometries of the murine tumors treated in the lab. Results suggest that tissues surface geometries and incidence angle of light can significantly alter the photon fluence inside the tissue. The photon fluence difference for an 8 mm diameter, curved surface mouse tumor vs. flat muscle tissue can be as high as 20%. In general, the greater the tissues curvature, the greater the potential loss in light fluence is. In summary, our data demonstrates the importance of tissue surface geometry and the incidence angle of light in determining optimal PDT light dosimetry, and indicates that comparisons between tissue geometries must be carried out with attention to differences in the internal optical distribution.