Dosimetry of rotational photon fields with gravity-oriented eye blocks

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Radiotherapy for facial tumors requires precise dose delivery to maximize tumor control and minimize damage to surrounding healthy tissues, particularly the eyes.
• Conventional techniques can struggle to achieve uniform dose distribution in complex facial geometries, potentially leading to under- or over-treatment of target volumes.

Purpose of the Study:

• To evaluate a novel radiotherapeutic technique employing eye protection accessories and machine-oriented beam compensation for uniform dose delivery to facial tumors.
• To assess the efficacy of this technique in sparing ocular structures while ensuring adequate target coverage.

Main Methods:

• Rotational 4 MV photon fields with gravity-oriented eye blocks were applied to patients and a phantom.
• A machine-oriented compensator with specific geometric features was used to enhance dose uniformity.
• Dose distributions were calculated using a treatment planning system and verified with thermoluminescent dosemeters (TLD) in vivo and in an anthropomorphic phantom.

Main Results:

• The technique achieved dose uniformity across the target, with doses to unblocked target regions showing 5% mean standard deviations.
• Ocular doses were reduced to approximately 15% of unblocked target doses.
• Doses to partly blocked target regions ranged from 86% to 129% of unblocked target doses, indicating effective dose delivery.

Conclusions:

• The investigated technique provides uniform target dose delivery and effective eye-sparing for tumors surrounding the eyes.
• This method demonstrates favorable comparison with conventional radiotherapy techniques in terms of simplicity and efficacy.
• The findings support the routine use of this technique for improved radiotherapy outcomes in facial tumor treatment.