Original Knee Fixation Device as a Useful Fixation Method during Prostate Intensity-Modulated Radiation Therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Intensity-modulated radiation therapy (IMRT) requires precise patient positioning to ensure accurate radiation delivery.
• Setup errors, including rotational and translational inaccuracies, can compromise treatment efficacy and increase toxicity.
• Existing immobilization techniques may not sufficiently address all sources of setup variability.

Purpose of the Study:

• To evaluate the effectiveness of an original knee fixation device (KFD) in reducing setup errors during IMRT.
• To assess the impact of the KFD on clinical target volume (CTV) coverage.
• To quantify improvements in rotational and translational accuracy with the KFD.

Main Methods:

• A comparative study was conducted with two groups: knee flexion (KF) using KFD (n=16) and knee extension (KE) without KFD (n=15).
• Residual rotational errors (yaw, pitch, roll) and inter-fractional setup errors (A-P, S-I) were measured.
• Inter-fractional margins were calculated, and CTV coverage was evaluated using logistic regression analysis.

Main Results:

• The KF group showed significant improvements in residual rotational errors (yaw, roll) and inter-fractional error in the A-P direction (P < 0.02).
• Inter-fractional margins were reduced by 20.8% in the A-P and 12.6% in the S-I directions in the KF group.
• The odds ratios for CTV coverage were significantly higher in the KF group (2.76 for A-P, 1.74 for S-I).

Conclusions:

• The KFD effectively reduces rotational and translational setup errors in IMRT.
• The use of KFD leads to improved CTV coverage and reduced margins, enhancing treatment precision.
• This original KFD is a potentially valuable tool for improving prostate IMRT immobilization.