Double-contrast micro-CT colonoscopy in live mice.

PURPOSE: Models of colon cancer in small rodents are of particular interest as they most closely simulate the development and growth of colonic cancer in humans. Micro-computed tomography has been used for detection of polyps in murine models of colon cancer. The study was performed to evaluate whether a novel high-speed continuous-rotation, single-breath-hold scanning protocol in combination with double-contrasting of the colon can be successfully applied for colonoscopy of live mice at acquisition times of 40 s. METHODS: C57BL/6JApcMin/+ mice were intubated and ventilated. After double-contrasting the colon with barium and air, mice underwent continuous rotation micro-CT (mean resolution 41 × 41 × 53 µm) during a single-breath-hold period of 40 s. Sensitivity to detect colon polyps by four blinded radiologists was analysed. Number and location of polyps were verified in the excised colon. Radiation dose was measured using a thermoluminescence dosimeter placed within the distal colon. RESULTS: In six of seven mice, a total of 12 polyps were detected in the explanted colon (one mouse without polyps). One tumor (8.3%) was located in the proximal third, seven tumors (58.1%) and four tumors (33.2%) were located in the middle and in the distal third of the colon, respectively. Mean tumor volume was 6.5 ± 3.6 mm(3). Sensitivity to detect colon polyps was 0.85 ± 0.1. Mean radiation dose was 0.241 ± 0.002 Gy. CONCLUSION: Using a high-speed continuous rotation micro-CT protocol, double-contrast single-breath-hold colonoscopy in mice is feasible and yields sufficient contrast to visualize the proximal colonic folds and to detect colonic polyps in vivo.

High-speed single-breath-hold micro-computed tomography of thoracic and abdominal structures in mice using a simplified method for intubation.

OBJECTIVES: Respiratory gating with and without controlled ventilation has been applied for in vivo micro-computed tomography (micro-CT) of thoracic and abdominal structures in mice. We describe a simplified method for intubation and demonstrate its applicability for single-breath-hold micro-CT in mice. METHODS: Mice (n = 10) were anesthetized, intubated, ventilated, and relaxed by intraperitoneal administration of rocuronium. Contrast-enhanced micro-CT of the complete thorax including the upper abdominal organs (80 kV; 37.5 µA; 190-degree rotation; 600 projections/20 seconds or 1200 projections/40 seconds; 39 × 39 × 50-µm voxel size) was performed with and without single-breath-hold technique. RESULTS: The simplified method of intubation was fast (<1 minute) and required no special hardware in all mice. Relaxation of mice allowed prolonged single-breath-hold imaging of up to 40 seconds. Diameter of smallest identifiable lung vessels was 100 µm. CONCLUSIONS: The presented simplified method for intubation in mice is fast, safe, and effective. Additional relaxation allowed high-resolution single-breath-hold micro-CT in mice.

Application of micro-CT in small animal imaging.

Over the past decade, the number of publications using micro-computed tomography (muCT) imaging in preclinical in vivo studies has risen exponentially. Higher spatial and temporal resolution are the key technical advancements that have allowed researchers to capture increasingly detailed anatomical images of small animals and to monitor the progression of disease in small animal models. The purpose of this review is to present the technical aspects of muCT, as well as current research applications. Our objectives are threefold: to familiarize the reader with the basics of muCT techniques; to present the type of experimental designs currently used; and to highlight limitations, future directions, in muCT-scanner research applications, and experimental methods. As a first step we present different muCT setups and components, as well as image contrast generation principles. We then present experimental approaches in order of the evaluated organ system. Finally, we provide a short summary of some of the technical limitations of muCT imaging and discuss potential future developments in muCT-scanner techniques and experimental setups.

Vascular imaging in small rodents using micro-CT.

In vivo animal models of neoplasm, stroke, subarachnoid hemorrhage, and other diseases involving alterations in vessel anatomy and diameter, require a fast and easy-to-use imaging tool that captures anatomical structure and biologic function data. Micro-computed tomography angiography (muCTA) offers high spatial and temporal resolution and is suitable to perform this task. However, conducting muCTA in small rodents, especially in mice, requires a high degree of accuracy and precision. This article describes a setup for in vivo muCTA in mice using both a bolus technique with a conventional contrast agent, as well as, angiography with a blood-pool contrast agent. Our setup in mice is at isotropic resolutions up to 16 microm with scanning times less than 1 min. The described protocol also addresses some of the technical challenges associated with the imaging of vascular structures in mice models.

Ultrafast high-resolution in vivo volume-CTA of mice cerebral vessels.

BACKGROUND AND PURPOSE: Animal models developed in rats and mice have become indispensable in preclinical cerebrovascular research. Points of interest include the investigation of the vascular bed and the morphology and function of the arterial, capillary, and venous vessels. Because of their extremely small caliber, in vivo examination of these vessels is extremely difficult. In the present study we have developed a method to provide fast 3D in vivo analysis of cerebral murine vessels using volume computed tomography-angiography (vCTA). METHODS: Using an industrial X-ray inspection system equipped with a multifocus cone beam X-ray source and a 12-bit direct digital flatbed detector, high-speed vCTA (180 degrees rotation in 40 s. at 30 fps) was performed in anesthetized mice. During the scan an iodinated contrast agent was infused via a tail vein. Images were reconstructed using a filtered backprojection algorithm. Image analysis was performed by maximum intensity projection (MIP) and 3D volume reconstruction. RESULTS: All mice tolerated i.v. injection of the iodinated contrast agent well. Smallest achievable voxel size of raw data while scanning the whole neurocranium was 16 mum. Anatomy of cerebral vessels was assessable in all animals, and anatomic differences between mouse strains could easily be detected. Mean vessel diameter was measured in C57BL/6 and BALBc mice. Changes of vessel caliber were assessable by repeated vCTA. CONCLUSIONS: Ultra fast in vivo vCTA of murine cerebral vasculature is feasible at resolutions down to 16 mum. The technique allows the assessment of vessel caliber changes in living mice, thus providing an interesting tool to monitor different features such as vasospasm or vessel patency.