A comparison of computed and measured heel effect for various target angles

Area of Science:

• Medical Physics
• Radiological Sciences
• X-ray Imaging

Background:

• Accurate modeling of X-ray emission spectra is crucial for diagnostic and therapeutic applications.
• The heel effect, a variation in X-ray intensity across the beam, is influenced by target material and geometry.
• Understanding Bremsstrahlung radiation is key to predicting X-ray beam characteristics.

Purpose of the Study:

• To evaluate two distinct models for predicting thick target X-ray emission spectra.
• To compare model predictions of filtered emission spectra against measured heel effect data.
• To assess the impact of target take-off angle and X-ray energy on spectral prediction accuracy.

Main Methods:

• Employed two thick target models: constant depth Bremsstrahlung and continuous slowing-down with multiple thin targets.
• Calculated filtered X-ray emission spectra at various angles.
• Integrated predicted spectra and compared them with measured heel effect data for tungsten targets.
• Investigated the influence of Bremsstrahlung angular anisotropy.

Main Results:

• Excellent agreement was achieved for tungsten targets at 7 and 10 degrees take-off angles for 60 and 100 kVp X-rays.
• The models accurately predicted the heel effect when Bremsstrahlung angular anisotropy was considered.
• Poorer results were observed for a 17.5 degrees target at 60 kVp, suggesting model limitations.

Conclusions:

• The validated models provide accurate predictions of X-ray spectra and heel effect for specific tungsten target configurations.
• Accounting for Bremsstrahlung angular anisotropy is essential for precise spectral modeling.
• Further refinement of Bremsstrahlung angular dependence models may be needed for steeper target angles.