Understanding and enhancing the use of micro-computed tomography in soft tissue

Abstract

The use of micro-computed tomography (micro-CT) has risen exponentially over the past decade. The capability of Micro-CT to provide high-resolution images has played an important role in enabling researchers to observe and analyse minute anatomic details in small animals. Furthermore, the non-destructive nature of this imaging modality has allowed researchers to monitor the progression of various diseases in small animal models.Micro-CT is most commonly used for imaging hard tissues and materials, however it’s extendibility to imaging soft tissue has been restricted due to poor inter-tissue contrast. Over the past decade, numerous publications addressed methods of increasing the contrast in the images produced through incorporation of various staining agents.This report describes a proposed study in which iodine potassium iodide (I2KI), phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) were investigated as contrast agents for soft tissue micro-CT imaging. The aim was to understand which stain provides the best inter-tissue contrast in rat cardiac tissue.A staining process itself was developed through this project. Through a literature review of related works it is evident that the perfusion-staining protocols from this project are novel and provide promising outcomes in terms of the contrast obtained.Micro-CT tissue images were assessed and compared for contrast and information content. Contrast was analysed using wide field and focused intensity histograms and statistical measures of intensity distributions. Structural information in each image was assessed using structure tensor analysis. Specific measures were fractional anisotropy and principle (fibre) structure orientations.The key outcomes of this project firstly include: (1) reproducible staining protocols that are capable of providing good contrast when imaging rat cardiac tissue using micro-CT; (2) the finding that PMA provides consistent and good levels of contrast in both normal rat cardiac tissue and diabetic rat cardiac tissue, closely followed by I2KI and by PTA; (3) that analysis between diabetic and non-diabetic rat cardiac tissues suggest an enhanced degree of structural anisotropy in diabetic cardiac tissue but transmural cardiac fibre orientation is unaffected.