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. 2022 May 19;27(2):360-370.
doi: 10.5603/RPOR.a2022.0029. eCollection 2022.

Evaluation of target volume and dose accuracy in intrafractional cases of lung cancer based on 4D-CT and 4D-CBCT images using an in-house dynamic thorax phantom

Firyal Dhiyaul Haqqi  1 , Arief Sudarmaji  1 , Wahyu Edy Wibowo  2 , Nuruddin Nasution  2 , Handoko Handoko  2 , Annisa Rahma Fauzia  2 , Jihadil Qudsi  3 , Supriyanto Ardjo Pawiro  1
Affiliations

Evaluation of target volume and dose accuracy in intrafractional cases of lung cancer based on 4D-CT and 4D-CBCT images using an in-house dynamic thorax phantom

Firyal Dhiyaul Haqqi et al. Rep Pract Oncol Radiother. .

Abstract

Background: This study aimed to evaluate the target volume and dose accuracy in intrafraction cases using 4-dimensional imaging modalities and an in-house dynamic thorax phantom. Intrafraction motion can create errors in the definition of target volumes, which can significantly affect the accuracy of radiation delivery. Motion management using 4-dimensional modalities is required to reduce the risk.

Materials and methods: Two variations in both breathing amplitude and target size were applied in this study. From these variations, internal target volume (ITVs) contoured in 10 phases of 4D-CT (ITV10), average intensity projection (AIP), and mid-ventilation (Mid-V) images were reconstructed from all 4D-CT datasets as reference images. Free-breathing (FB), augmentation free-breathing (Aug-FB), and static images were also acquired using the 3D-CT protocol for comparisons. In dose evaluations, the 4D-CBCT modality was applied before irradiation to obtain position correction. Then, the dose was evaluated with Gafchromic film EBT3.

Results: The ITV10, AIP, and Mid-V provide GTVs that match the static GTV. The AIP and Mid-V reference images allowed reductions in ITVs and PTVs without reducing the range of target movement areas compared to FB and Aug-FB images with varying percentages in the range of 29.17% to 48.70%. In the dose evaluation, the largest discrepancies between the measured and planned doses were 10.39% for the FB images and 9.21% for the Aug-FB images.

Conclusion: The 4D-CT modality can enable accurate definition of the target volume and reduce the PTV. Furthermore, 4D-CBCT provides localization images during registration to facilitate position correction and accurate dose delivery.

Keywords: 4D-CBCT; 4D-CT; dose evaluation; in-house phantom; volume evaluation.

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Conflict of interest statement

Conflict of interest The authors declare that they have no conflicts of interest.

Figures

Figure 1
Figure 1
A. Assembly of the in-house dynamic thorax phantom; B. Controller of the dynamic component
Figure 2
Figure 2
Comparison of gross tumour volumes (GTVs), internal target volumes (ITVs), and planning target volumes (PTVs) (in cm3) on several reference images for a (A) 2-cm-diameter target and (B) 3-cm-diameter target
Figure 3
Figure 3
The distribution of discrepancies in all reference images for the first comparison. FB — free breathing; AugFB — augmentation free breathing; ITV — internal target volume; AIP — average intensity projection; Mid-V — mid-ventilation phase
Figure 4
Figure 4
The distribution of discrepancies in all reference images in the second comparison. FB — free breathing; AugFB — augmentation free breathing; ITV — internal target volume; AIP — average intensity projection; Mid-V — mid-ventilation phase
See this image and copyright information in PMC

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