Evaluation of Ultra-low-dose Paediatric Cone-beam Computed Tomography for Image-guided Radiotherapy

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Diagnostic Imaging

Background:

• Daily cone-beam computed tomography (CBCT) is underutilized in pediatric radiotherapy due to concerns about imaging radiation dose.
• Simulating lower-dose CBCT protocols is crucial for designing safer and more effective clinical workflows.
• Accurate image guidance is essential for precise radiation delivery in pediatric cancer treatment.

Purpose of the Study:

• To simulate and evaluate ultra-low-dose CBCT for pediatric image-guided radiotherapy.
• To assess the impact of dose reduction on image registration accuracy and visual image quality.
• To determine the feasibility of implementing reduced-dose CBCT protocols in clinical practice.

Main Methods:

• Ultra-low-dose CBCT was simulated by adding noise to projection images, validated in phantoms, and applied to 100 pediatric patient scans at doses ranging from 0.125 to 0.5 mGy.
• Automatic and inter-observer registration accuracy for bony and soft-tissue anatomy was assessed.
• Visual image quality was evaluated using Likert scales for registration performance and visibility of critical structures.

Main Results:

• Simulated ultra-low-dose CBCT scans showed registration discrepancies within 2 mm and 1° for bony anatomy compared to the clinical protocol, with excellent inter-observer agreement.
• Bone visualization and registration performance were acceptable (over 75%) down to the lowest simulated doses.
• Soft-tissue registration and visualization demonstrated significant discrepancies and did not meet acceptability thresholds.

Conclusions:

• Accurate simulation of ultra-low-dose CBCT is feasible and effective for bony anatomy setup in pediatric radiotherapy.
• Significant dose reduction (down to 0.125 mGy) is achievable, potentially allowing for daily image guidance.
• Implementing ultra-low-dose CBCT could enhance the accuracy of patient positioning and improve radiotherapy outcomes for children.