EPID in vivo dosimetry in RapidArc technique

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Accurate in vivo dose verification is critical in modern radiotherapy.
• The amorphous silicon electronic portal imaging device (aSi-EPID) offers potential for real-time dose monitoring.
• RapidArc is an advanced arc therapy technique requiring precise dose delivery.

Purpose of the Study:

• To estimate the delivered dose at the reference point using an aSi-EPID during patient treatment.
• To validate a novel method for in vivo dose evaluation in RapidArc radiotherapy.

Main Methods:

• A direct proportionality between EPID signal and delivered dose was assumed.
• Treatment plans were calculated for patients using the RapidArc technique.
• Dose was measured using an ionization chamber in a water-equivalent phantom and compared with EPID signal.
• An in vivo dose calculation formula was derived using EPID data and phantom measurements.
• Irradiation was performed on a Varian Clinac using an aSi-1000 EPID and Eclipse/Helios treatment planning system.

Main Results:

• In vivo dose calculations were performed for five patients.
• The planned dose at the reference point was 2 Gy for all treatment plans.
• The mean in vivo dose ranged from 1.96 Gy to 2.09 Gy, showing good agreement with planned doses.

Conclusions:

• The developed method is suitable for in vivo dose evaluation in RapidArc treatments.
• The aSi-EPID can be effectively utilized for accurate dose monitoring in clinical practice.