Precise radiotherapy has emerged as a primary method for delivering radiation therapy in modern treatment practices. Radiotherapy techniques, such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), aim for greater dose conformality and gradient. The complex aperture shape and corresponding intensities are modulated by varying the positions of the multileaf collimator (MLC) leaves. Even a slight deviation in leaf positions may result in significant dosimetric effects. According to a study conducted by Alejandra Rangel et al., a 1mm position shift of all MLC leaves resulted in a 2.7% increase in the error of the reference equivalent uniform dose (EUD) for the prostate and a 5.6% increase in the error for the head and neck clinical target volume (CTV). Therefore, accuracy of delivery is crucial due to the complex and non-intuitive fluences.

Several factors impact the accuracy of dose delivery, including the treatment planning system calculation algorithm and the mechanical accuracy of linear accelerator. The algorithm accuracy may lead to the differences between the prescribed dose and planned dose. For example, DLG (leaf gap) is a critical parameter in the MLC model used in Eclipse treatment planning system, and it significantly influences dosimetric calculations. Jinkoo Kim et al. proposed that the dose calculation errors decreased 6.2% for 6X and 5.9% for 6XFFF when DLG value increased 1 mm. Currently, Monte Carlo is widely considered the most accurate algorithm for dose calculation, while other algorithms pursue faster calculation speed at the expense of accuracy. Hence, exploring the algorithm effect on dose calculation is indispensable. Discrepancies can arise between the planned dose distribution and the actual dose delivered due to the mechanical accuracy of the linear accelerator. Beam quality, beam energy, beam profile and MLC leaf position accuracy play crucial roles in ensuring accurate dose delivery during patient treatment. Improving the accuracy of linear accelerator and enhancing the speed of performance for quality assurance are persistent and noteworthy subjects in precision radiotherapy.

Therefore, in this special issue, we focused on two aspects as follows:

(1) Enhancing the accuracy of dose calculations in treatment planning system, including modeling and algorithms

(2) Conducting quality assurance for linear accelerator

We are determined to provide recommendations for mechanical quality assurance of linear accelerator and enhancing clinical dose delivery. By addressing these aspects, we aim to improve the overall accuracy and precision of radiotherapy treatments.