A comprehensive quality assurance procedure for 4D CT commissioning and periodic QA

Abstract

Purpose The 4D computed tomography (CT) simulation is an essential procedure for tumors exhibiting breathing‐induced motion. However, to date there are no established guidelines to assess the characteristics of existing systems and to describe meaningful performance. We propose a commissioning quality assurance (QA) protocol consisting of measurements and acquisitions that assess the mechanical and computational operation for 4D CT with both phase and amplitude‐based reconstructions, for regular and irregular respiratory patterns. Methods The 4D CT scans of a QUASAR motion phantom were acquired for both regular and irregular breathing patterns. The hardware consisted of the Canon Aquilion Exceed LB CT scanner used in conjunction with the Anzai laser motion monitoring system. The nominal machine performance and reconstruction were demonstrated with measurements using regular breathing patterns. For irregular breathing patterns the performance was quantified through the analysis of the target motion in the superior and inferior directions, and the volume of the internal target volume (ITV). Acquisitions were performed using multiple pitches and the reconstructions were performed using both phase and amplitude‐based binning. Results The target was accurately captured during regular breathing. For the irregular breathing, the measured ITV exceeded the nominal ITV parameters in all scenarios, but all deviations were less than the reconstructed slice thickness. The mismatch between the nominal pitch and the actual breathing rate did not affect markedly the size of the ITV. Phase and normalized amplitude binning performed similarly. Conclusions We demonstrated a framework for measuring and quantifying the initial performance of 4D CT simulation scans that can also be applied during periodic QAs. The regular breathing provided confidence that the hardware and the software between the systems performs adequately. The irregular breathing data suggest that the system may be expected to capture in excess the target motion and geometry, but the deviation is expected to be within the slice thickness.

A comprehensive quality assurance program for four-dimensional computed tomography in radiotherapy

“…Two separate groups also recently published a detailed overview of their QA workflow for 4DCT commissioning and periodic QA. In the workflow presented by Polizzi et al [11] , 4DCT images of a QUASAR motion phantom were acquired with both regular and irregular breathing curves. Tumor motion and ITV were analyzed to quantify 4DCT performance.…”

Shallow kinetics induced by a metronome (SKIM): A novel contactless respiratory motion management

“…In general, there is a limitation of breathing speed when scanning a patient with 4DCT. Thus, it is essential to check the specific capabilities and limitations of the CT scanner 24–26 . For example, the maximum value of BPM for the Brilliance Big Bore CT is 60.…”

“…Thus, it is essential to check the specific capabilities and limitations of the CT scanner. [24][25][26] For example, the maximum value of BPM for the Brilliance Big Bore CT is 60.…”

4DCT is long overdue for improvement

“…The authors proposed acceptable volume and amplitude deviation criteria after fine‐tuning acquisition parameters and evaluating results from various phantom studies, with regular and irregular breathing patterns. 50 …”

“…In recognizing the need to quantify target delineation uncertainties, a more recent study showed that a comprehensive QA of 4DCT could quantify the system's performance. The authors proposed acceptable volume and amplitude deviation criteria after fine‐tuning acquisition parameters and evaluating results from various phantom studies, with regular and irregular breathing patterns 50 …”