Meeting Abstract
Diffusible iodine-based contrast-enhanced computed tomography (diceCT) permits the visualization of soft-tissue anatomy at high three-dimensional spatial scales relatively rapidly and at minimal expense. However, its implementation can meet with widely varying levels of success owing to the bewilderingly complex array of variables related to specimen fixation, storage, staining, size, and µCT scanning. These can conspire to make consistent and favorable results somewhat elusive. To address this issue, we designed a 780-sample repeated-measures analysis, using pairwise grayscale differentials to systematically document and analyze the effects of these variables. We used thick (~1 cm) sections from the bodies of adult python specimens (Liasis, Antaresia) to represent standard samples of vertebrate tissues (e.g., cortical bone, spinal gray and white matter, skeletal muscle). Four size classes based on section diameter were prepared in triplicate as: (1) freshly fixed in neutral buffered formalin, (2) frozen followed by formalin fixation, or (3) freshly fixed followed by storage in ethanol, each to mimic common specimen preparations. Triplicates were stained with various exposures to iodine potassium-iodide (I2KI) and µCT scanned to determine how size-to-iodine relationships alter tissue contrasts. Next, the best contrasted exemplars were µCT scanned under various beam settings to determine the iodine-to-power relationships that maximize these contrasts. Our results indicate that: (1) long staining durations at low concentrations of I2KI are optimal; (2) µCT scanner settings should minimize voltage, maximize current, and enable multi-frame averaging; and (3) freshly fixed tissues are best-suited for diceCT imaging, followed by ethanol preservation and freezing.
