A comparative study of postural fixation techniques for radiotherapy in upper abdominal malignancies

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Techniques

Background:

• Accurate patient positioning is critical in radiotherapy for upper abdominal malignancies.
• Setup errors can lead to under- or over-dosing of the target volume and surrounding organs at risk.
• Optimizing postural fixation techniques is essential for improving treatment precision.

Purpose of the Study:

• To evaluate the effectiveness of a combined thermoplastic body film and air bag technique versus thermoplastic body film alone in reducing setup errors.
• To compare random errors (Σ), systematic errors (σ), and planning target volume (PTV) margins (MPTV) between the two techniques.
• To assess the impact of different postural fixation methods on positional accuracy in patients with upper abdominal tumors.

Main Methods:

• A comparative study involving 77 patients with upper abdominal malignancies.
• Patients were divided into an observation group (thermoplastic body film + air bag) and a control group (thermoplastic body film only).
• Setup errors along X, Y, and Z axes were measured using cone-beam computed tomography (CBCT) and registered with planning CT images. Statistical analysis was performed using the Wilcoxon rank-sum test.

Main Results:

• The observation group demonstrated statistically significant reductions in three-directional setup errors (X, Y, Z) and the resultant displacement vector (T) compared to the control group (p < 0.05).
• Random errors (Σ), systematic errors (σ), and PTV margins (MPTV) were consistently smaller in the observation group.
• The combined technique resulted in improved positional accuracy and reduced variability in patient setup.

Conclusions:

• The combination of thermoplastic body film and an air bag is a superior postural fixation method for reducing radiotherapy setup errors in upper abdominal malignancies.
• This technique enhances positional repeatability, minimizes both random and systematic errors, and allows for smaller PTV margins.
• Implementing this combined approach can lead to improved treatment efficacy and better protection of healthy tissues adjacent to the tumor.