Cone-beam-CT guided radiation therapy: A model for on-line application

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image-Guided Therapy

Background:

• Accurate patient positioning is critical for effective radiation therapy.
• Traditional set-up methods can be limited by anatomical variations and motion.
• On-line imaging offers a potential solution for real-time error correction.

Purpose of the Study:

• To present efficient and generalized processes for clinical application of on-line X-ray volumetric cone-beam CT imaging (XVI).
• To improve the accuracy of patient set-up in radiation therapy using XVI.
• To illustrate XVI image-guided therapy in contrasting sites: intra-cranial radiosurgery and prostate radiation therapy.

Main Methods:

• A two-step process for determining on-line set-up errors was developed.
• Step 1: Registration of XVI data to planning data by matching machine and planning isocenters.
• Step 2: Second registration to correct residual displacements; accuracy investigated in phantom studies.

Main Results:

• Sub-pixel set-up errors (down to 0.5mm) were accurately determined and implemented in radiosurgery.
• XVI provided quality skull detail for precise on-line skull-based alignment.
• A 'local XVI' technique showed soft-tissue detail for on-line prostate set-up.

Conclusions:

• XVI has significant potential to enhance radiation treatment accuracy.
• Current XVI image quality supports bony and soft-tissue set-up error determination and correction.
• Efficient procedures for utilizing on-line XVI data are crucial for image-guided therapy.