Respiratory-gated micro-CT using a carbon nanotube based micro-focus field emission x-ray source

A prototype physiologically gated micro-computed tomography (micro-CT) system based on a “eld emissionmicro-focus x-ray sour ce has been developed for in vivo imaging of small animal models. The novel x-raysource can generate radiation with a programmable waveform that can be readily synchronized and gated withnon-periodic physiological signals. The system performance is evaluated using phantoms and sacri“ced andanesthetized mouse models. Prospect ive respiratory-gated CT images of a nesthetized free-breathing mice arecollected using this scanner at 100msec temporal resolution and 10lp/mm of 10% system MTF.Keywords: micro-CT, in vivo imaging, respiratory gating, x-ray source, carbon nanotube 1. INTRODUCTION Micro-computed tomography (micro-CT) is an important tool in non-invasive screening of small animals suchas mice and rats for pre-c linical cancer studies. 1–3 Compared to clinical CT scanners, a much higher spatialresolution is needed in order to image the anatomy of small animals with research interest. Current commercialmicro-CT scanners oer the capability of imaging objects ex-vivo with high spatial resolution. Studies on lungand colon cancer models have shown that micro-CT is capable of sequentially tracking tumors of larger than2mm in diameter with high “delity. Small tumors are still hardly distinguishable from the normal tissue, whichis partially attributed to the motion-induced artifacts created by peristalsis, respiration and cardiac motion.The motion-induced artifacts can in principle be minimized by prospective gating where the image acquisition issynchronizedwith the physiological signals, as commonly done in clinical CT scanners. However, performing suchmeasurements on small animals is challenging because their physiological motions are at least ten times fasterthan those of human. Motion-induced artifacts blur the micro-CT image resulting in signi“cantly deterioratedspatial resolution than the nominal values.Several new designs have been considered for high-resolution CT imaging of live animals. One is to use ahigh power rotating anode x-ray source instead of a “xed-anode micro-focus x-ray tube.