X-ray dose delivered during a longitudinal micro-CT study has no adverse effect on cardiac and pulmonary tissue in C57BL/6 mice

Abstract

Background: Micro-computed tomography (micro-CT) offers numerous advantages for small animal imaging, including the ability to monitor the same animals throughout a longitudinal study. However, concerns are often raised regarding the effects of X-ray dose accumulated over the course of the experiment.

Purpose: To scan C57BL/6 mice multiple times per week for 6 weeks, in order to determine the effect of the cumulative dose on pulmonary and cardiac tissue at the end of the study.

Material and methods: C57BL/6 male mice were split into two groups (irradiated group = 10, control group = 10). The irradiated group was scanned (80 kVp/50 mA) three times weekly for 6 weeks, resulting in a weekly dose of 0.84 Gy, and a total study dose of 5.04 Gy. The control group was scanned on the final week. Scans from week 6 were reconstructed and the lungs and heart were analyzed.

Results: Overall, there was no significant difference in lung volume or lung density or in left ventricular volume or ejection fraction between the control group and the irradiated group. Histological samples taken from excised lung and myocardial tissue also showed no evidence of inflammation or fibrosis in the irradiated group.

Conclusion: This study demonstrated that a 5 Gy X-ray dose accumulated over 6 weeks during a longitudinal micro-CT study had no significant effects on the pulmonary and myocardial tissue of C57BL/6 mice. As a result, the many advantages of micro-CT imaging, including rapid acquisition of high-resolution, isotropic images in free-breathing mice, can be taken advantage of in longitudinal studies without concern for negative dose-related effects.

Keywords: Micro-CT; X-ray dose; cardiac function; lung density; lung volume; myocardial tissue; pulmonary tissue.