Deep learning-based two-step organs at risk auto-segmentation model for brachytherapy planning in parotid gland carcinoma.

Purpose: Delineation of organs at risk (OARs) represents a crucial step for both tailored delivery of radiation doses and prevention of radiation-induced toxicity in brachytherapy. Due to lack of studies on auto-segmentation methods in head and neck cancers, our study proposed a deep learning-based two-step approach for auto-segmentation of organs at risk in parotid carcinoma brachytherapy. Material and methods: Computed tomography images of 200 patients with parotid gland carcinoma were used to train and evaluate our in-house developed two-step 3D nnU-Net-based model for OARs auto-segmentation. OARs during brachytherapy were defined as the auricula, condyle process, skin, mastoid process, external auditory canal, and mandibular ramus. Auto-segmentation results were compared to those of manual segmentation by expert oncologists. Accuracy was quantitatively evaluated in terms of dice similarity coefficient (DSC), Jaccard index, 95th-percentile Hausdorff distance (95HD), and precision and recall. Qualitative evaluation of auto-segmentation results was also performed. Results: The mean DSC values of each OAR were 0.88, 0.91, 0.75, 0.89, 0.74, and 0.93, respectively, indicating close resemblance of auto-segmentation results to those of manual contouring. In addition, auto-segmentation could be completed within a minute, as compared with manual segmentation, which required over 20 minutes. All generated results were deemed clinically acceptable. Conclusions: Our proposed deep learning-based two-step OARs auto-segmentation model demonstrated high efficiency and good agreement with gold standard manual contours. Thereby, this novel approach carries the potential in expediting the treatment planning process of brachytherapy for parotid gland cancers, while allowing for more accurate radiation delivery to minimize toxicity.

[Analysis of clinical effects of iliolumbar fixation in treating sacrum fracture of Denis type II].

OBJECTIVE: To evaluate the clinical effects of iliolumbar fixation for the sacrum fractures of Denis type II. METHODS: The clinical data of 86 patients with sacrum fracture of Denis type II treated by iliolumbar fixation from January 2008 to January 2012 were retrospectively analyzed. There were 55 males and 31 females, aged from 17 to 55 years old with an average of 39.1 years. Among them, 73 cases complicated with pelvis fracture and 13 cases with acetabular fracture; 37 cases with sacral neurological symptoms and 49 cases without sacral neurological symptoms. Fracture healing time, nerve function, clinical function and complications were observed in the patients. RESULTS: In 86 cases, 6 cases were out of followed-up and 80 cases were followed up from 24 to 71 months with an average of 36 months. The mean fracture healing time was 13 weeks (ranged, 10 to 38 weeks). According to Gibbons scoring to evaluate the neurological function, preoperative nerve rehabilitation, lower limbs feeling, lower limbs activity,bladder and rectum function,total score respectively were 0.62 +/- 0.04, 1.54 +/- 0.35, 1.12 +/- 0.18, 0.23 +/- 0.01, 3.46 +/- 0.47 and postoperative respectively were 0.82 +/- 0.12, 0.36 +/- 0.04, 0.05 +/- 0.01, 0.03 +/- 0.01, 1.25 +/- 0.22, there were statistically significant differences between preoperative and postoperative (P < 0.05). According to Majeed scoring to evaluate the clinical function, postoperative pain, standing, sitting, sexual life, work ability, total score respectively were 22.54 +/- 4.02, 27.93 +/- 5.46, 8.47 +/- 3.61, 2.54 +/- 1.33, 16.46 +/- 4.34, 81.32 +/- 8.73, 60 cases got excellent results, 17 good, 3 fair. The main complications including fracture nonunion of 5 cases,deep incision infection of 1 case, and screw prominence resulting uncomfortable of 8 cases. CONCLUSION: Iliolumbar fixation has the advantages of stable fixation, satisfactory functional rehabilitation, less complications, and is a good method in treating sacrum fracture of Denis type II.

Replanning Criteria and Timing Definition for Parotid Protection-Based Adaptive Radiation Therapy in Nasopharyngeal Carcinoma.

The goal of this study was to evaluate real-time volumetric and dosimetric changes of the parotid gland so as to determine replanning criteria and timing for parotid protection-based adaptive radiation therapy in nasopharyngeal carcinoma. Fifty NPC patients were treated with helical tomotherapy; volumetric and dosimetric (D mean, V 1, and D 50) changes of the parotid gland at the 1st, 6th, 11th, 16th, 21st, 26th, 31st, and 33rd fractions were evaluated. The clinical parameters affecting these changes were studied by analyses of variance methods for repeated measures. Factors influencing the actual parotid dose were analyzed by a multivariate logistic regression model. The cut-off values predicting parotid overdose were developed from receiver operating characteristic curves and judged by combining them with a diagnostic test consistency check. The median absolute value and percentage of parotid volume reduction were 19.51 cm(3) and 35%, respectively. The interweekly parotid volume varied significantly (p < 0.05). The parotid D mean, V 1, and D 50 increased by 22.13%, 39.42%, and 48.45%, respectively. The actual parotid dose increased by an average of 11.38% at the end of radiation therapy. Initial parotid volume, initial parotid D mean, and weight loss rate are valuable indicators for parotid protection-based replanning.