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Case Reports
. 2024 Aug 15;16(8):e66943.
doi: 10.7759/cureus.66943. eCollection 2024 Aug.

Enhancing Precision in Radiation Therapy for Locally Advanced Lung Cancer: A Case Study of Cone-Beam Computed Tomography (CBCT)-Based Online Adaptive Techniques and the Promise of HyperSight™ Iterative CBCT

Jingwei Duan  1 , Joel A Pogue  1 , Drexell H Boggs  1 , Joseph Harms  1
Affiliations
Case Reports

Enhancing Precision in Radiation Therapy for Locally Advanced Lung Cancer: A Case Study of Cone-Beam Computed Tomography (CBCT)-Based Online Adaptive Techniques and the Promise of HyperSight™ Iterative CBCT

Jingwei Duan et al. Cureus. .

Abstract

This study explores the dosimetric benefits of cone-beam computed tomography (CBCT)-based online adaptive radiation therapy (oART) for a non-small-cell lung cancer (NSCLC) patient exhibiting significant tumor shrinkage during ChemoRT. The patient was prescribed 60 Gray (Gy) in 30 fractions and was initially treated with conventional RT. After the delivery of the first four treatment fractions, the patient's treatment course was converted to oART due to tumor shrinkage seen on CBCT. Current oART dose calculations use a synthetic CT (sCT) image derived from deformable image registration (DIR) of the planning CT to the daily CBCT, and, as the tumor regressed, the discrepancy between the CBCT and the sCT increased, leading to a re-simulation after the delivery of the ninth fraction. In this case report, we first investigated dosimetric differences leveraged by converting this patient from conventional RT to oART. With oART using sCT, the patient's target coverage remained consistent with the reference plan while simultaneously changing lung V20 by 7.8 ± 1.4% and heart mean by 3.4 ± 1.5 Gy. Then, using this new simulation CT and comparing it with iterative CBCT (iCBCT) images acquired with the new HyperSight™ (HS) (Varian Medical Systems, Inc., Palo Alto, CA, USA) imaging system on the Ethos, we investigated the impact of direct dose calculation on HS-iCBCT as compared to sCT. The HS-iCBCT generated a dose distribution similar to the CT reference, achieving a 96.01% gamma passing rate using Task Group-218 (TG-218) criteria. Results indicate that HS-iCBCT has the potential to better reflect daily anatomical changes, resulting in improved dosimetric accuracy. This study highlights the advantages of oART in the presence of tumor response to therapy and underscores HS-iCBCT's potential to provide CT-level dose calculation accuracy in oART for NSCLC patients.

Keywords: cbct-dosimetry; dosimetric analysis; online-adaptive radiotherapy; synthetic ct; tumor regression.

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Conflict of interest statement

Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: Drexell H. Boggs declare(s) research support from Varian Medical Systems, Inc. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1. Patient’s diagnosis and treatment timeline.
oART: Online adaptive radiation therapy; PET/CT: Positron emission tomography/computed tomography; RML: Right middle lobe; Fx: Fraction; IGRT: Image-guided radiation therapy
Figure 2
Figure 2. Three views of the patient’s CT simulations at different times.
The blue, green, and red contours indicate the GTV, CTV, and PTV, respectively. GTV: Gross tumor volume; CTV: Clinical target volume; PTV: Planning target volume; CBCT: Cone-beam computed tomography; Fx: Fraction
Figure 3
Figure 3. Mean DVHs for the reference, adapted, and scheduled plans.
The scheduled and adapted plans were both calculated on sCT for each oART session. The shaded areas represent the standard deviation across 26 fractions. Each individual fraction dose was scaled to the full-course dose before averaging. DVHs: Dose-volume histograms; sCT: Synthetic computed tomography; oART: Online adaptive radiation therapy; PTV: Planning target volume; GTV: Gross tumor volume
Figure 4
Figure 4. a) The plan scores of the scheduled plan and adapted plan, both calculated on sCT; b) The plan scores of the adapted plan calculated on HS-iCBCT and sCT, respectively.
sCT: Synthetic computed tomography; HS-iCBCT: HyperSight iterative cone-beam computed tomography; oART: Online adaptive radiation therapy
Figure 5
Figure 5. Mean DVHs of adapted plans calculated on HS-iCBCT and sCT for all oART sessions.
The differences between sCT and HS-iCBCT calculations (sCT minus HS-iCBCT) are inserted. The shaded area indicates the standard deviation among 26 fractions. Each individual fraction dose is scaled to the full-course dose before averaging. DVHs: Dose-volume histograms; HS-iCBCT: HyperSight iterative cone-beam computed tomography; sCT: Synthetic computed tomography; oART: Online adaptive radiation therapy; PTV: Planning target volume; GTV: Gross tumor volume
Figure 6
Figure 6. Gamma passing rate between HS-iCBCT and sCT throughout the oART treatment course under different criteria.
HS-iCBCT: HyperSight iterative cone-beam computed tomography; sCT: Synthetic computed tomography; oART: Online adaptive radiation therapy
Figure 7
Figure 7. Images from the re-CT, along with HS-iCBCT and sCT at fraction 9, are presented.
Using re-CT as the reference, the gamma distributions of HS-iCBCT and sCT with a criterion of 3%/2 mm are shown on re-CT. HS-iCBCT: HyperSight iterative cone-beam computed tomography; sCT: Synthetic computed tomography; Fx: Fraction
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