Treat-through OLED Displays: Dosimetry and performance of OLED AVATAR screens for Megavoltage Radiotherapy

TL;DR

This study evaluates OLED AVATAR screens for pediatric radiotherapy, demonstrating minimal dose perturbation and confirming their suitability for clinical use with high image quality and fast alignment.

Contribution

It provides a comprehensive dosimetry assessment of OLED screens in radiotherapy, establishing their safety and performance for treatment setups.

Findings

Average attenuation difference of 0.3% with OLED screens

Minimal dose deviations in megavoltage arc therapy

Surface dose slightly increased but remains low

Abstract

The AVATAR system utilizes a radiolucent video display to help relax and immobilize pediatric patients during radiotherapy. This study investigates the use of OLED (Organic Light Emitting Diode) displays, which offer superior image quality and faster alignment compared to traditional projector-based systems, albeit with slightly increased thickness. The dose perturbations caused by these screens were assessed to evaluate their suitability for radiotherapy. A 20 cm OLED screen was positioned in the patient's line of sight, between the patient's head and the radiation source. The screen comprises a 0.25 mm thick flexible OLED panel and a custom carbon fiber backing (0.3 to 0.6 mm thick), with most electronic components relocated via ribbon cable. 6 MV portal images were captured with and without the screen to create transmission maps. Additionally, parallel plate ion chamber measurements were taken at the surface and at depth in a solid water phantom. The OLED's radiation tolerance was tested with a 100 Gy dose delivery and 12 months of use in an active radiotherapy linac vault. The portal image transmission maps indicated an average attenuation difference of 0.3\% (SD = 0.37 \%) between measurements with and without the AVATAR screen, with a maximum point attenuation of 3\%. Ion chamber measurements revealed a 0.31\% decrease in dose at 2 cm depth and a 7.04 \% increase at the surface under an anterior-posterior beam. For a VMAT arc, the dose difference was 0.04 \% at 2 cm depth and 0.1\% at the phantom surface. The minimal dose deviations indicate that these screens are suitable for megavoltage arc therapy without significantly affecting the target dose. While surface dose is slightly increased for static anterior beams, it remains low. For lower photon energies or particle beams, larger perturbations may occur, necessitating further measurements or beam entry avoidance.