Abstract
Current optical imaging techniques can successfully measure tumor load in murine models of lung carcinoma but lack
structural detail. We demonstrate that respiratory gated micro-CT imaging of such models gives information about
structure and correlates with tumor load measurements by optical methods.
Four mice with multifocal, Kras-induced tumors expressing firefly luciferase were imaged against four controls using
both optical imaging and respiratory gated micro-CT. CT images of anesthetized animals were acquired with a custom
CNT-based system using 30 ms x-ray pulses during peak inspiration; respiration motion was tracked with a pressure
sensor beneath each animal's abdomen. Optical imaging based on the Luc+ signal correlating with tumor load was
performed on a Xenogen IVIS Kinetix.
Micro-CT images were post-processed using Osirix, measuring lung volume with region growing. Diameters of the
largest three tumors were measured. Relationships between tumor size, lung volumes, and optical signal were compared.
CT images and optical signals were obtained for all animals at two time points. In all lobes of the Kras+ mice in all
images, tumors were visible; the smallest to be readily identified measured approximately 300 microns diameter. CT-derived
tumor volumes and optical signals related linearly, with r=0.94 for all animals. When derived for only tumor
bearing animals, r=0.3. The trend of each individual animal's optical signal tracked correctly based on the CT volumes.
Interestingly, lung volumes also correlated positively with optical imaging data and tumor volume burden, suggesting
active remodeling.
