Preliminary dosimetric evaluation of a designed head and neck phantom for intensity modulated radiation therapy (IMRT)

Abstract

The aims of this paper are to design, construct, and evaluate an anthropomorphic head and neck 
phantom for dosimetric verification of nasopharyngeal cancer treatment plan using intensity modulated 
radiation therapy (IMRT) technique. The phantom was designed as an assembly of thirty nine (39) 
transversal section slabs fabricated from Perspex material each with delineated planning target 
volumes (PTVs) and organ at risk (OARs) regions. Thermoluminescent dosimeter (TLD) was used after 
multiple calibration cycles. The phantom was imaged, planned, and irradiated by IMRT plan. The 
reproducibility of phantom measurements was checked by three identical IMRT irradiations. Four (4) 
nasopharyngeal patients’ IMRT treatment plans were transferred to the phantom for dose verification. 
Phantom’s measured doses were reproducible with less than 3.5% standard deviation. For the 
verification of IMRT patient’s plans, the mean of percent dose differences between measured and 
calculated doses was found 6.2% (SD: 4.7) at OAR and 5.96% (SD: 2.5%) at PTV. The percentage dose 
deviation met the accuracy criteria of 7% at low dose regions. The standard deviation of TLD/TPS was 
2.4% at PTV and 6.8% at OAR. This good agreement proves the feasibility of applying this phantom 
in IMRT dose verification.