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. 2019 Jan 25;20(1):229-234.
doi: 10.31557/APJCP.2019.20.1.229.

Application of aSi-kVCBCT for Volume Assessment and Dose Estimation: An Offline Adaptive Study for Prostate Radiotherapy

Arun Gandhi  1   2 , Subramani Vellaiyan, Shanmuga Subramanian, Shanmugam Thirumalai Swamy, Kala Subramanian, Anantharaman Ayyalusamy
Affiliations

Application of aSi-kVCBCT for Volume Assessment and Dose Estimation: An Offline Adaptive Study for Prostate Radiotherapy

Arun Gandhi et al. Asian Pac J Cancer Prev. .

Abstract

Objective: The purpose of this study is to develop a method to estimate the dose using amorphous silicon detector panel cone beam computed tomography (aSi-kVCBCT) for the OARs and targets in prostate radiotherapy and to compare with the actual planned dose. Methods: The aSi-kVCBCT is used widely in radiotherapy to verify the patient position before treatment. The advancement in aSi-kVCBCT combined with adaptive software allows us to verify the dose distribution in daily acquired CBCT images. CBCT images from 10 patients undergoing radical prostate radiotherapy were included in this study. Patients received total dose of 65Gy in 25 fractions using volumetric modulated arc therapy (VMAT). aSi-kVCBCT scans were acquired before daily treatment and exported to smart adapt software for image adaptation. The planning CT is adapted to daily aSi-kVCBCT images in terms of HU mapping. The primary VMAT plans were copied on to the adapted planning CT images and dose was calculated using Anisotropic Analytic Algorithm (AAA). The DVH is then used to evaluate the volume changes of organs at risk (OAR), the actual dose received by OARs, CTV and PTV during a single fraction. Results: The normalized volume of the bladder and rectum ranged from 0.70–1.66 and 0.70–1.16 respectively. The cumulative mean Sorensen–Dice coefficient values of bladder and rectum were 0.89±0.04 and 0.79±0.06 respectively. The maximum dose differences for CTV and PTV were 2.5% and -4.7% and minimum were 0.1% and 0.1% respectively. Conclusion: The adapted planning CT obtained from daily imaging using aSi-kVCBCT and SmartAdapt® can be used as an effective tool to estimate the volume changes and dose difference in prostate radiotherapy.

Keywords: aSi-kVCBCT; adapted planning CT; prostate radiotherapy; volume change; dose difference.

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Figures

Figure 1
Figure 1
The Volume Projection in an Axial Section of Bladder and Rectum on the Weekly Adapted Planning CT
Figure 2
Figure 2
Normalized Bladder Volume Corresponding to Initial Planning Volumes
Figure 3
Figure 3
Normalized Rectum Volume Corresponding to Initial Planning Volumes
Figure 4
Figure 4
Dose Distribution and DVH Spread on Planning CT and Adapted Planning CT of a Prostate Patient
See this image and copyright information in PMC

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