ABSTRACT
Objective:To evaluate the practicability of dose volume histogram (DVH) prediction model for organ at risk (OAR) of radiotherapy plan by minimizing the cost function based on equivalent uniform dose (EUD).Methods:A total of 66 nasopharyngeal carcinoma (NPC) patients received volume rotational intensity modulated arc therapy (VMAT) at Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences from 2020 to 2021 were retrospectively selected for this study. Among them, 50 patients were used to train the recurrent neutral network (RNN) model and the remaining 16 cases were used to test the model. DVH prediction model was constructed based on RNN. A three-dimensional equal-weighted 9-field conformal plan was designed for each patient. For each OAR, the DVHs of individual fields were acquired as the model input, and the DVH of VMAT plan was regarded as the expected output. The prediction error obtained by minimizing EUD-based cost function was employed to train the model. The prediction accuracy was characterized by the mean and standard deviation between predicted and true values. The plan was re-optimized for the test cases based on the DVH prediction results, and the consistency and variability of the EUD and DVH parameters of interest (e.g., maximum dose for serial organs such as the spinal cord) were compared between the re-optimized plan and the original plan of OAR by the Wilcoxon paired test and box line plots.Results:The neural network obtained by training the cost function based on EUD was able to obtain better DVH prediction results. The new plan guided by the predicted DVH was in good agreement with the original plan: in most cases, the D 98% in the planning target volume (PTV) was greater than 95% of the prescribed dose for both plans, and there was no significant difference in the maximum dose and EUD in the brainstem, spinal cord and lens (all P>0.05). Compared with the original plan, the average reduction of optic chiasm, optic nerves and eyes in the new plans reached more than 1.56 Gy for the maximum doses and more than 1.22 Gy for EUD, and the average increment of temporal lobes reached 0.60 Gy for the maximum dose and 0.30 Gy for EUD. Conclusion:The EUD-based loss function improves the accuracy of DVH prediction, ensuring appropriate dose targets for treatment plan optimization and better consistency in the plan quality.
ABSTRACT
In order to explore new ways in restraining the ascending blood pressure, this paper reports a research on the effects of multi-mode audio frequency pulse modulating laser irradiation with electrical stimulation on the hemorrheology and blood pressure of the spontaneously hypertensive rats (SHR). Forty male SHR were randomly divided into four groups: Group A (control), Group B (treated with electrical stimulation on stomach 36 point (ST-36)), Group C (treated with low level pulse laser irradiation on Erjian acupuncture point), Group D (low level laser irradiation together with electrical stimulation on Erjian acupuncture point and ST-36). Laser irradiation lasted for 45 min/ day, while electrical stimulation lasted for 30 min/day. After 10 days' treatment, we compared the hemorrheology and blood pressure of the rats in the four groups. The results were that values of hemorrheology in group A and group C were obviously improved compared with those in the other two groups. Meanwhile, the blood pressures in the three treated groups (B, C, and D) were lower than in the control group after the treatment, and the value of the rats in group A was the lowest. In conclusion, the treatment the laser irradiation combined with electrodes stimulation on spontaneously hypertensive rats brought better results of hemorrheology and blood pressure in the tested rats.