CT image-guided intensity-modulated therapy for paraspinal tumors using stereotactic immobilization

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Technology

Background:

• Paraspinal lesions require precise radiotherapy for effective treatment.
• Accurate patient immobilization and positioning are critical for minimizing radiation dose to healthy tissues.
• Existing immobilization techniques may have limitations in achieving high precision for spinal targets.

Purpose of the Study:

• To develop and evaluate a noninvasive stereotactic immobilization technique for paraspinal lesions.
• To implement daily CT image-guided positioning for accurate treatment delivery.
• To quantify systematic and random patient setup errors associated with the technique.

Main Methods:

• Development of a stereotactic body frame (SBF) for rigid immobilization.
• Evaluation of system accuracy using phantom studies.
• Daily CT-guided positioning and setup error correction in seven patients with thoracic and lumbar spine lesions over 33 treatment fractions.
• Retrospective analysis of treatment impact without daily corrections.

Main Results:

• The SBF system demonstrated accuracy within 1 mm (1 SD) for phantom targets.
• Average systematic and random setup errors for uncorrected patient setups were approximately 2 mm and 1.5 mm (1 SD), respectively.
• Intensity-modulated radiotherapy plans showed potential for >100% dose increase to the spinal cord without daily corrections.

Conclusions:

• The noninvasive SBF with daily CT guidance provides accurate and precise immobilization for paraspinal lesion treatment.
• Setup accuracy better than 2 mm (1 SD) is achievable with the SBF.
• Daily CT guidance is crucial for highly conformal treatments, ensuring spinal cord dose remains within 10-15% of the planned value.