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CBCT dose reduction with HyperSight on an Ethos linear accelerator: A phantom-based TLD measurement study.
Svenja Ganz1, Sven Knobe1, Marc Ries1
1Saarland University Hospital and Saarland University Faculty of Medicine, Clinic for Radiotherapy and Radiation Oncology, Kirrberger Str. 100, 66421 Homburg/Saar, Germany.
Zeitschrift Fur Medizinische Physik
|July 15, 2026
Summary
The HyperSight cone-beam CT system offers high-quality imaging with reduced organ doses compared to older systems. Careful protocol selection is crucial to minimize radiation exposure during adaptive radiotherapy.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Radiation Dosimetry
Background:
- The HyperSight cone-beam CT (CBCT) system aims to improve image quality for online-adaptive radiotherapy.
- Daily imaging with CBCT systems can increase cumulative organ radiation dose.
- Evaluating organ doses and associated risks is essential for patient safety.
Purpose of the Study:
- To evaluate and compare organ doses across different HyperSight CBCT protocols on an O-ring Linac.
- To calculate the effective dose and secondary cancer risk from daily HyperSight imaging.
- To assess the image quality and dose benefits of HyperSight compared to previous CBCT systems.
Main Methods:
- Thermoluminescent dosimeter (TLD) measurements were conducted on an anthropomorphic phantom for all HyperSight CBCT protocols.
- TLDs were positioned across various anatomical regions (head, thorax, pelvis) to measure organ doses.
- Effective doses and secondary cancer risks were calculated based on measured organ doses.
Main Results:
- HyperSight CBCT demonstrated lower mean organ doses (e.g., bladder, rectum) compared to OBI Version 1.4.13.
- A left-right dose asymmetry was noted due to partial gantry rotation, affecting beam-facing organs.
- Imaging dose varied significantly; Low Dose protocols reduced exposure by up to 55%, while slow/large protocols increased it by 40-60%.
Conclusions:
- HyperSight CBCT provides high-quality imaging with reduced dose levels compared to earlier CBCT generations.
- Observed beam geometry-related dose asymmetry requires consideration in clinical practice.
- Individualized protocol selection is vital for minimizing radiation exposure under ALARA principles in image-guided radiotherapy.
