Document Type

Article

Publication Date

4-1-2025

Comments

This article is the author's final published version in Journal of Applied Clinical Medical Physics, Volume 26, Issue 4, April 2025, Article number e70056.

The published version is available at https://doi.org/10.1002/acm2.70056.

Copyright © 2025 The Author(s)

Abstract

PURPOSE: To evaluate a 16 cm-array axial four-dimensional computer tomography (4DCT) in comparison with a 4 cm-array 4DCT in the presence of respiration irregularity.

METHOD: Ten traces of lung tumor motion from CyberKnife treatments were imported to move the lung cylinder, containing a spherical target, of a phantom. Images were acquired for the lung that moved to each of the 10-positions/phases (1) step-wisely by nominal helical scan at each movement (ground truth), (2) continuously by 4D scan with the 16 cm array, and (3) the same with the 4 cm array, involving table shift. Irregularities, consisting of baseline shift and/or amplitude change of the traces in their second periods, affected #3 scan only in its second table position. The full-widths at half maximum of the target in the direction of the motion were determined on the average (Ave) CT, maximum-intensity (Mip) CT, and a phase (MP) CT that is associated with the maximum error, comparing #2 and 3 with #1. Three tumor-shaped targets were also imaged, and overlap ratios of them from #2 and 3 with the targets from #1 were inter-compared. Hounsfield unit (HU)s of the targets were also compared.

RESULTS: The average difference in the spherical-target length between #2 and #1 was found to be 0.28 ± 0.15 cm on AveCT, 0.00 ± 0.18 cm on MipCT, and 0.07 ± 0.06 cm on MPCT, showing agreement. The average difference between #3 and #1 was 0.34 ± 0.23 cm on AveCT, 0.48 ± 0.31 cm on MipCT, and 0.56 ± 0.50 cm on MPCT, showing disagreement. The overlap ratios were better with #2 than with #3 for all tumor-shaped targets in each phase CT and MipCT, but they were not perfect for #2 due to motion averaging and phase sorting limitations. The differences in HUs were smaller with #2 than with #3, but not fully satisfactory with #2.

CONCLUSION: 4DCT with the 16 cm array needs to be used to minimize the impact of the irregularity.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

PubMed ID

39989327

Language

English

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