Real time evaluation of overranging in helical computed tomography

TL;DR

This paper introduces a simple, real-time dosimetry method using a pencil chamber to accurately estimate overranging in modern helical CT scans with adaptive collimation, replacing less suitable film-based methods.

Contribution

A new, easy-to-implement real-time overranging estimation method using a pencil chamber for modern CT scanners with adaptive collimation.

Findings

Method is easy to implement and time-efficient.

Achieves accuracy comparable to film-based benchmarks.

Suitable for modern CT systems with adaptive collimation.

Abstract

Overranging or overscanning increases the dose delivered to patients undergoing helical Computed Tomography examinations. In order to reduce it, nowadays most of the multidetector tomographs close the X-ray beam aperture at the scan extremes. This technical innovation, usually referred to as dynamic or adaptive collimation, also influences the overranging assessment methods. In particular, the film free approach proposed in previous studies is not suitable for these modern tomographs. The present study aims to introduce a new method of estimating overranging with real time dosimetry, even suitable for tomographs equipped with adaptive collimation. The approach proposed is very easy to implement and time saving because only a pencil chamber is required. It is also equivalent in precision and in accuracy to the film based one, considered an absolute benchmark.