A diamond target for megavoltage cone-beam CT

Area of Science:

• Medical Physics
• Radiological Imaging
• Materials Science

Background:

• Megavoltage cone-beam CT (MV-CBCT) is crucial for image-guided radiation therapy.
• Traditional MV-CBCT systems often use graphite or tungsten targets, influencing beam characteristics.
• Optimizing target materials can enhance imaging performance and system efficiency.

Purpose of the Study:

• To evaluate the imaging properties of a megavoltage cone-beam CT system utilizing an unflattened beam from a sintered diamond target.
• To compare the performance of a diamond target at 4 and 6 MV with existing target materials.

Main Methods:

• A sintered diamond target was integrated into a linear accelerator's imaging beamline, replacing a graphite target.
• Images of phantoms and patients were acquired using both diamond and graphite targets at 4 MV and 6 MV.
• Monte Carlo simulations were employed to determine beam spectra and dose distributions.

Main Results:

• The diamond target enabled imaging at both 4 MV and 6 MV, aligning with treatment beam energies.
• Image quality at 4 MV with the diamond target was comparable to the graphite target.
• A slight decrease in contrast-to-noise ratio was observed at 6 MV due to spectral changes, with minimal impact on overall image quality.

Conclusions:

• Sintered diamond targets offer comparable image quality to graphite targets in MV-CBCT.
• Diamond targets facilitate the use of higher beam energies (6 MV) and may simplify system installation and maintenance.
• The use of diamond targets can potentially lead to higher dose rates for equivalent beam currents.