Quantifying the dosimetric effects of neck contour changes and setup errors on the spinal cord in patients with nasopharyngeal carcinoma: establishing a rapid estimation method.

The purpose of this study was to quantify the effect of neck contour changes and setup errors on spinal cord (SC) doses during the treatment of nasopharyngeal carcinoma (NPC) and to establish a rapid dose estimation method. The setup errors and contour changes in 60 cone-beam computed tomography (CBCT) images of 10 NPC patients were analysed in different regions of the neck (C1-C3, C4-C5 and C6-C7). The actual delivered dose to the SC was calculated using the CBCT images, and univariate simulations were performed using the planning CT to evaluate the dose effects of each factor, and an index ${\mathrm{Dmax}}_{\mathrm{displaced}}$ was introduced to estimate the SC dose.

A preliminary study of using a deep convolution neural network to generate synthesized CT images based on CBCT for adaptive radiotherapy of nasopharyngeal carcinoma.

This study aims to utilize a deep convolutional neural network (DCNN) for synthesized CT image generation based on cone-beam CT (CBCT) and to apply the images to dose calculations for nasopharyngeal carcinoma (NPC). An encoder-decoder 2D U-Net neural network was produced. A total of 70 CBCT/CT paired images of NPC cancer patients were used for training (50), validation (10) and testing (10) datasets.

[Resolutions of high superficial dose in intensity-modulated radiation therapy when the target area is close to the surface].

Objective: To study the impact of different planning target volume (PTV) margin settings on surface and superficial dose distribution and explore the resolution of high superficial dose when the target area is close to the surface during head and neck intensity-modulated radiotherapy (IMRT).

Methods: A typical superficial target volume was designed in an circular neck phantom. Two experimental inverse IMRT plans were conducted with 8MV X ray, and in plan A, the superficial side of PTV margin ranged from 0 to 5 mm, while other side margins were 5 mm; in plan B, an suppositional machine dosimetry data for IMRT optimization was established in which the build-up dose was eliminated, and this machine data was used to optimize the inverse IMRT plan followed by recalculation of the planned dose distribution with the actual clinical machine dosimetry data.