Optimal ct protocols for ct-guided planning preparation in radiotherapy

Abstract

The invention of the computed tomography (CT) in 1972 by Cormack and Hounsfield allowed for the very first time the acquisition of 3D images. CT scans taken for radiotherapy treatment planning usually differ from those taken for diagnostic use, since those are optimized to perform a three-dimensional dose calculation inside the patient. Radiation dose is of less concern than in diagnostic imaging, even though it should be always minimized. Image quality (IQ) has indeed relevant importance as it affects the accuracy of the treatment planning (par. 2). In order to correctly simulate a radiation treatment condition, several requirements are suggested: it is essentially the identification of the optimal CT acquisition parameter settings (CT scanner protocols), considering the special requirements of CT simulation (par. 3). For CT scanners used as a simulator for radiotherapy treatment, the quality assurance (QA) needs to be very comprehensive as it includes two important aspects: imaging CT and treatment planning, as it provides input for the TPS (par. 4). Improvements in the CT simulations are also a topic of recent research. In particular, the use of dual-energy CT (DECT) and cone beam CT (CBCT) as CT simulators is described in paragraph 5. Another area of research, which is now being transferred into clinical operation, is the one related to MRI-based delivery systems. This growing technology allows acquisition of online MRI images which present with the major advantages as compared to CT images: high soft tissue contrast and radiation-free (par. 5).