Evaluation of scan strategies for small animal in vivo micro-CT

Abstract

The micro-CT scanners of the radiography laboratories at the Institute of Experimental and Applied Physics (IEAP) have been used many times for post mortem imaging of small animals. The systems are based on the Timepix detector technology and they can provide CT models with spatial resolution up to few micrometres for such samples. Until now the investigated samples were ex vivo organs or small animals and image quality was a key parameter of these scans. The transition to the in vivo measurement is connected with the limitation of the absorbed dose in the investigated sample. Pilot measurements with the thermoluminescent dosimeters (TLD) were performed and the dose rate for a small rodent was estimated. This dose rate limits the maximal irradiation time for live specimens to tens of seconds to avoid immunosuppression or other irreversible biological damages. Series of measurements were performed with PlastiMouseTM phantom using different acquisition parameters to evaluate best data acquisition strategy for given dose limits. The presented data refers to the relationship between exposure time recorded by the detector and the reconstructed micro-CT slices quality. Contrast-to-noise ratio was evaluated for 112 selected combinations of acquisition times and angular sampling. This covers a range of sample doses from 50 to 4500 mGy delivered during recorded exposure time.