Real-time dosimetry in lung cancer radiotherapy using PET imaging of positrons induced by gold nanoparticles

Radiation therapy (RT) is a potent lung cancer treatment. Real-time dosimetry improves precision and minimizes damage to healthy tissues. However, challenges persist due to invasive, low-resolution, or limited applicability of real-time dosimetry methods. The study aims to use gold nanoparticles (AuNPs)-induced pair production to acquire PET (Positron Emission Tomography) images during lung tumor radiotherapy and assess their feasibility for real-time dose monitoring. The GATE Monte Carlo code was employed to create a simulation of PET imaging for lung tumors with different levels of AuNP (2%, 4%, 6%, 8%, and 10% by weight (wt%)) during radiotherapy with 6 MV, 10 MV, and 15 MV photon beams. The quality of images was evaluated by utilizing signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Additionally, the root mean square error (RMSE) was calculated to evaluate differences between the normalized intensity volume histogram (nIVH) from PET images and the reference normalized dose volume histogram (nDVH). The study found that increasing AuNP concentrations in the tumor had minimal impact on CNR, SNR, and RMSE values for 6 MV photon beams. For 10 MV beams, CNR and SNR remained stable up to 8 wt%, but increased beyond this. For 15 MV beams, CNR and SNR values were constant at 4 wt% or lower but improved when exceeding 4 wt%. The lowest RMSE values for 15 MV beams were observed at concentrations of 4 wt% or higher. PET imaging with a 10 MV photon beam achieves acceptable dosimetric accuracy with at least 8 wt% AuNPs. Additionally, incorporating AuNPs at 4 wt% or higher concentrations in lung tumors allows for real-time dose monitoring during radiotherapy with a 15 MV photon beam.