In vivo micro-computed tomography imaging in liver tumor study of mice using Fenestra VC and Fenestra HDVC.

Contrast agents are used to enhance the visibility of rodent organs during in vivo micro-computed tomography imaging. Specifically, this non-invasive technique can study liver tumor growth and progression in small animals. Fenestra VC and the novel Fenestra HDVC were compared for enhancement in the liver of healthy and tumor-bearing mice, and the images were compared for their ability to define the tumor border, volume and quantity of tumors. Fenestra VC and Fenestra HDVC were injected into healthy eight-week-old female mice (C57BL/6) via the tail vein then imaged at seven different time points. The experimental results showed that 0.005 mL/g of Fenestra HDVC resulted in the same enhancement for all eight organs as 0.01 mL/g of Fenestra VC across all time points. For the tumor study, B16F10 tumors were surgically introduced into ten eight-week-old female mice (C57BL/6) then imaged in vivo over a 3 day period. Ex vivo micro-CT images of the excised livers were also obtained. The tumor volume and quantity were measured in each image, and the tumour progression observed over 3 days. We showed Fenestra HDVC is effective for in vivo imaging in rodents because the optimal enhancement level in organs is maintained at a reduced injection volume.

Time-course study of a gold nanoparticle contrast agent for cardiac-gated micro-CT imaging in mice.

Although micro-computed tomography (micro-CT) images have high contrast for bone or air, between soft tissues the contrast is typically low. To overcome this inherent issue, attenuating exogenous contrast agents are used to provide contrast enhancement in the vasculature and abdominal organs. The aim of this study is to measure the contrast enhancement time course for a gold nanoparticle blood-pool contrast agent and use it to perform cardiac-gated 4D micro-CT scans of the heart. Six healthy female C57BL/6 mice were anesthetized and imaged after receiving an injected dose of MVivo gold nanoparticle blood-pool contrast agent. Following the injection, we performed micro-CT scans at 0, 0.25, 0.5, 0.75, 1, 2, 4, 8, 24, 48 and 72 h. The mean CT number was measured for 7 different organs. No contrast enhancement was noticed in the bladder, kidneys or muscle during the time-course study. However, it clearly appears that the contrast enhancement is high in both right ventricle and vena cava. To perform cardiac-gated imaging, either the gold nanoparticle agent (n = 3) or an iodine-based (n = 3) contrast agent was introduced and images representing 9 phases of the cardiac cycle were obtained in 6 additional mice. A few typical cardiac parameters were measured or calculated, with similar accuracy between the gold and iodinated agents, but better visualization of structures with the gold agent. The MVivo Au contrast agent can be used for investigations of cardiac or vascular disease with a single bolus injection, with an optimal cardiac imaging window identified during the first hour after injection, demonstrating similar image quality to iodinated contrast agents and excellent measurement accuracy. Furthermore, the long-lasting contrast enhancement of up to 8 h can be very useful for scanning protocols that require longer acquisition times.