Direct measurement of CTDI_w on helical CT scans

Abstract

Purpose Medical physics computed tomography (CT) practice involves measurements to determine CTDIvol on representative clinical CT protocols. In current practice the majority of CT exams employ helical scans. To determine CTDIvol for a helical scan, one measures CTDIw with an axial scan, then divides by the pitch. Problems arise in CT units where one is unable to select an axial scan with the same detector configuration and pre‐patient (bowtie) filtration that is employed on the helical scan. Presented is a method to measure CTDIw on helical scans. Methods The body and head CTDI phantoms were supported on the gantry shroud with brackets attached to the phantom. The phantom is above the tabletop and remains stationary during helical scans as the table moves beneath the phantom. With the phantom stationary, the CTDIw associated with head and body helical scans was measured. CTDIw was also measured for head and body axial scans with the same pre‐patient filtrations and detector configurations. Results For both the head and body CTDI phantom the agreement between the axial and helical CTDIw measurements was <1.5%. Conclusions Body and head CTDIw and CTDIvol can be directly measured by employing helical scans with the method in this paper

Safire Strength Optimization: Effect on Tissue Contrast and Pathological Assessment of Brain MSCT With Non-Hemorrhage Stroke (Snh)

“…The radiation dose received by the patient can be estimated using parameters such as CTDI and DLP. CTDI refers to the average absorbed dose over the entire z-axis that is irradiated and adjacent or can also be represented as a homogeneous phantom absorbed dose (DePew et al, 2022). Computer Tomography Dose Index (CTDI) is a CT scan X-ray dose on a single slice and is usually measured using a standard phantom cylinder.…”