Objective:To explore the adjustment ranges of auto-segmentation contours for organs at risk (OAR) in patients with nasopharyngeal carcinoma and assess the dosimetric impacts of the contours from varying sources on radiotherapy plans.Methods:Twenty-five patients with early-stage nasopharyngeal carcinoma were investigated. Through expert delineation, deep learning-based automatic delineation, and atlas-based automatic delineation of their spinal cord, brainstem, optic nerves, optic chiasm, parotid glands, oral cavity, hypopharynx, and mandible, as well as expert correction of these automatic delineations, five structure sets were formed. Moreover, the contours delineated by experts (also referred to as the expert contours) of the target volumes and other OARs were copied into the images for subsequent research. The Dice similarity coefficients (DSCs) of the structure sets were calculated. Using the radiotherapy plans optimized based on expert contours as templates, the radiotherapy plans and dose distributions of all the structure sets were established. The expert contours and contours determined using automatic delineation and corrected by experts (also referred to as the corrected contours) were defined as clinical contours. Then, three research objectives were set: the dosimetric effects of inter-observer clinical contour variations, the impacts of contour variations on plan optimization, and the impacts of contour variations on plan evaluation.Results:The average DSC of the visual pathway was 0.62±0.10, lower than that of other OARs (0.86±0.04). After expert correction, the DSCs of contours obtained using deep learning- and atlas-based automatic delineation increased by 7.61% and 10.69%, respectively. For the dosimetric effects of inner-observer contour variations, the Dmax of the optic chiasm was the maximum (3.96±6.02)Gy, while the Dmean of the hypopharynx was the minimum (0.81±0.55 Gy). When the impacts of contour variations on plan optimization were assessed based on expert contours, the dose differences (Δ D) exceeding ±3 Gy accounted for 22%, 14%, 46%, and 42%, respectively for the spinal cord, brainstem, optic nerve, and optic chiasm and accounted for only 2% for other OARs. After expert correction, the Δ D between automatic and expert contours decreased, with Δ D exceeding ±3 Gy decreased by 16% and 14%, respectively for the optic nerves and optic chiasm. When the average distance of the overlap volume histogram (OVH) exceeded 3.5 cm, all Δ Dmax fell within ±3 Gy. When the average distance of OVH was greater than 1.5 cm, all Δ Dmean fell within ±2 Gy. For contours obtained using deep learning and atlas-based automatic delineation, the doses of 50.0%±17.3% and 52.6%±19.3% of patients fell within the dose ranges of clinical contours, respectively. The numbers of patients for whom the Dmax of the spinal cord, optic nerve, optic chiasm and the D1 cm 3 of the mandible in the two types of automatic contours fell within the dose ranges of clinical contours were statistically different ( t = -4.24, -3.99, -3.16, 3.51, P < 0.05). Conclusions:After expert correction, the automatic delineation results from different sources exhibited certain geometric differences. The expert correction reduced the impacts of automatic contours on plan optimization. The average distance of OVH is identified as an important feature used to determine dose differences. For small-volume serial organs close to the target volumes, meticulous corrections are required before applying auto-segmentation to clinical practice.

Objective To analyze the target volume margins and positioning errors in the radiotherapy for nasopharyngeal carcinoma(NPC)using the cone-beam computed tomography(CBCT)of Halcyon linear accelerator for providing a reference for the margin from clinical target volume to planning target volume(CTV-to-PTV margin)in the radiotherapy for NPC using Halcyon linear accelerator,hence improving treatment precision and effectiveness.Methods A total of 117 NPC patients who received volumetric modulated arc therapy using Halcyon linear accelerator from May 2020 to June 2022 in Jinshazhou Hospital of Guangzhou University of Chinese Medicine were enrolled.The 3861 CBCT images collected from the patients were matched with the CT images to obtain the correction values of the treatment couch in lateral(Lat),longitudinal(Lng)and vertical(Vrt)directions for positioning error analysis.The CTV-to-PTV margin was obtained by the equation(margin =2.5∑+0.7δ).Results The positioning errors in the radiotherapy for NPC using Halcyon linear accelerator were 0.10(0.00,0.10)cm,0.10(0.00,0.20)cm and 0.20(0.10,0.30)cm in Lat,Lng and Vrt directions,respectively.The CTV-to-PTV margins in Lat,Lng and Vrt directions were 0.12,0.12 and 0.09 cm,respectively.Conclusion Low positioning errors can be achieved for NPC patients undergoing image-guided treatment using Halcyon linear accelerator.

Peripheral pulmonary lesions(PPL),including peripheral pulmonary nodules,are common lung problems.As the increase of patients with lung nodules,the demand for tissue sampling also increases.Safe and accurate biopsy techniques are very important for patients to identify benign and malignant lesions.Electronic bronchoscopy is one of the biopsy techniques for the diagnosis of PPL in recent decades.Various guiding techniques,such as radial probe endobronchial ultrasound and virtual navigation bronchoscope,have been proved to improve the performance of conventional bronchoscopy.This paper aims to provide an review of the available data on advanced bronchoscopic techniques and explore their application in diagnosing PPL.