Work

Computed tomography for four‐dimensional dose calculation: Effect of detector array length

Year: 2026

Type: article

Abstract: Purpose Four‐dimensional computed tomography (4DCT) is susceptible to a geometrical error when respiration changes upon patient shift. 4DCT using 16‐cm detector arrays, not needing the shift, has been shown to improve geometrical accuracy, compared with a conventional 4DCT (4‐cm array), albeit with some Hounsfield unit discrepancies. The 4DCTs were validated for 4D planning. Materials and methods A lung‐mimicking phantom containing a spherical target with ten respiratory traces and three tumor‐shaped targets with their traces was respectively imaged when, to each of the ten‐positions/phases, the lung was moved (1) step‐wisely by helical scan at each movement (ground truth; 4DCT GT ), (2) continuously by 4D scan with 16 cm detectors (4DCT 16 ), and (3) similarly with 4 cm detectors (4DCT 4 ). Respiratory irregularities affected 4DCT 4 only due to shifts. Treatment plans included volumetric modulated arc therapy (VMAT) and intensity‐modulated proton therapy (IMPT) on averaged CT images from 4DCT 16 and 4DCT 4 . IMPT was targeted to internal gross target volumes (iGTVs) with density overrides (1.0 g/cm 3 ), while VMAT to iGTVs+3 mm, with the objective V prescribed dose(PD) ≥ 95%. The plans were recalculated on each phase image of 4DCT GT and those of 4DCT 16 were additionally calculated on its phase images. The calculated doses were registered to the maximum‐exhale image, and summed. Results (1) 4DCT 16 : IMPT plans met the objective, despite under‐coverages in certain phase images, achieving 98.95 ± 1.09% and 98.27% in averaged V PD for the spherical and tumor targets, respectively. VMAT plans showed 97.26 ± 1.60% and 94.41% for the respective targets. (2) 4DCT 4 : IMPT plans did not meet the objective with 93.83 ± 9.29% and 97.38% for them. VMAT plans yielded 93.20 ± 5.81% and 91.17% for them. (3) 4DCT 16 versus 4DCT GT : 4D doses based on 4DCT 16 matched those on 4DCT GT with 62.76 Gy versus 62.76 ± 0.19 Gy for IMPT plans and 63.79 Gy versus 63.90 ± 0.28 Gy for VMAT plans. Conclusions The 4DCT 16 demonstrated accurate and reliable imaging of a lung tumor in 4D dose by IMPT plans. However, it could be affected by phase‐sorting uncertainty.

Source: Journal of Applied Clinical Medical Physics

DOI: 10.1002/acm2.70550

Authors: Inhwan Yeo, Qianyi Xu

Institution: Thomas Jefferson University

Language: English

Topic: Advanced Radiotherapy Techniques

Subfield: Radiation

Field: Physics and Astronomy

Domain: Physical Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $900