Dose reduction in CT Fluoroscopy

Computed Tomography Fluoroscopy (CTF) is a technique that provides the physician immediate feedback due to the reconstruction and display of CT images in real time and overcomes the classic limitations of ultrasound imaging and conventional fluoroscopy. It matches the advantages of CT quality images to be matched with the speed of fluoroscopic guidance. CTF images have (1) a wide dynamic range for imaging air, soft tissue and bone, (2) they do not superimpose anatomical structures as conventional fluoroscopy does, (3) and provide acceptable image quality less affected by patient breathing and motion (Kato et al 1996; Froelich et al 1998; Nickoloff et al 2000). These characteristics allow immediate correction for depth and direction of a needle during a percutaneous procedure. The obvious benefits of obtaining CT images in real time has made CTF a popular image guiding tool for various types of non-vascular and therapeutic interventions. Reported procedures with CTF guidance are, amongst others, precise needle placement, core biopsies, fluid collection aspirations, catheter insertion and drainages, local drug injections, radio-frequency ablations, placement of marking coils before stereotactic radiotherapy, lumbar nerve root blocks, vertebroplasty, jejunostomy tube insertion, arthrodesis of the spine and arthrography. The term "fluoroscopy" in CTF is only used by analogy with its conventional radiology counterpart; the only common thing is that both techniques are based on x-ray imaging that give the impression of a real-time imaging display. In this chapter, the use of real-time CT is referred to as CT fluoroscopy.