Phantom scatter factors for small MV photon fields.

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Accurate dosimetry in small radiation fields is crucial for modern radiotherapy.
• Previous studies have reported variations in S(p) values, necessitating further investigation.

Purpose of the Study:

• To create a comprehensive table of small field scatter- هوا (S(p)) values.
• To compare these values with existing literature and investigate discrepancies.

Main Methods:

• S(p) values were calculated from measured scatter- هوا (S(cp)) and phantom scatter- هوا (S(c)) data.
• Measurements were performed using three types of diodes and a diamond detector.

Main Results:

• Differences in S(p) values were attributed to detector and phantom-specific issues in S(cp) and S(c) measurements.
• Small field S(p) values were found to be independent of beam defining system and linac design.
• S(p) values derived from photon diode measurements were unreliable due to S(cp) measurement problems.

Conclusions:

• Electron and stereotactic diodes, along with diamond detectors, are suitable for S(cp) and S(c) measurements.
• Further Monte Carlo modeling is needed to clarify discrepancies between diamond and unshielded diode S(p) values.
• A final table of S(p) values for fields greater than 0.5 cm width was generated.