The Protection Efficiency Of Individualized Bite Block System In Three Dimensional Conformal Radiotherapy For Head And Neck Cancer

Objective: Radiation therapy has become one of the three big mainstream methods for the treatment of cancer.The improvement of focal control and minimization the incidence of normal tissue complication is the always popurse of radiation therapy.In this study,imaging tool,such as CT,computer simulation were used for three dimensional conformal radiotherapy was used for oral and maxillofacial cancer,make radiation therapy plan.The aim of this research is to evaluate the protection efficiency of individualized bite block system in three-dimensional conformal radiation therapy.Methods: An adult female was selected with Cranial and maxillofacial spiral CT scanning,2-mm-thick reconstructed sections,scanning range in eyebrow bow for the upper bound,lower bound for the shape of laryngeal cartilage.different parts and different sizes of oral and maxillofacial region cancer were simulated on patient wear 10-mm-thick individualized bite block system or not.The simulated cancer lesions were sketched in Three dimensional conformal radiotherapy system by the physicist and physician,include the tumor volume,clinical target volume,internal target volume,planning target volume,treatment volume,irradiated volume,and the border of the protected organs.According the T-stage,protected organs and Oral and maxillofacial malignant tumor treatment guidelines,the subjects were grouped as follows:Group 1: lip cancer,with mandible and teeth as protection organ,PTV designed by 21.6ccm with Preoperative radiotherapy(70Gy);PTV designed by 33.2ccm with Postoperative radiotherapy(60Gy).Group 2: tongue cancer,maxilla and mandible as the protedtion organ,PTV designed by 31.5ccm with External beam radiotherapy(70Gy);PTV designed by 47.5ccm with postoperative radiotherapy(60Gy).Group 3: maxilla and gingival cancer,with tongue and mandible as the protection organ,PTV designed by 15.6ccm with External beam radiotherapy(70Gy);PTV designed by 17.0ccm with postoperative radiotherapy(60Gy).Calculate the dose volume of protected organs.Data recorded and then analyzed by the statistical software.Results: All the different sizes of individualized bite block can be wear on patient.1 Lip cancer group: The data show that in the case of the same intensity of radiation dose,the dose volume of target organ has been decreased after wearing the individualized bite block system.Make the statistical analysis to the data.The paired T test results as follows,the mandible(70 gy)group(P = 0.001(P< 0.05);Teeth(70 gy)group(P= 0.000(P< 0.05);Mandible(60 gy)group(P= 0.009(P < 0.05);Teeth(60 gy)group(P= 0.000(P< 0.05),so there are obvious differences before and after wearing individualized bite block system,there is statistical significance,It shows that the normal tissues in used group by radiation dose volume is less than the group non-used.2 Tongue cancer group: The experimental data show that in the both of cases of External beam radiotherapy and postoperative radiotherapy,mandible by dose volume has reducted in the high dose area(over50 gy and over 40 gy),and increased in the low dose region(over 30 gy,over 20 gy,over 10 gy),after wearing the individualized bite block.The maxilla as target organ by dose volume has decreased to some extent.Take the data for statistical analysis.The paired T test results as follows,the mandible(70 gy)group(P= 0.543(p>0.05);Maxilla(70 gy)group(P= 0.000(P< 0.05);Mandible(60 gy)group(P= 0.391(P>0.05);Maxilla(60 gy)group(P= 0.000(P< 0.05),The results show that the maxilla group have obvious difference with non-used and used group,It has statistical significance.Mandible groups has no statistical significance.3 maxilla and gingival tumor group: The data showed that the dose volume received by tongue in used group was significantly smaller than nonused.The mandible was less visible and even increased in lower doses area.Take the statistical analysis to the data.The paired T test results as follows,The mandible(70Gy)group P = 0.136(P>0.05);The tongue(70Gy)group P = 0.002(P< 0.05);The mandible(60Gy)group P = 0.101(P>0.05);The tongue(60Gy)group P= 0.005(P< 0.05),The results show that tongue group has a statistical significance.The Mandible group has no statistical significance.Conclusion: The individualized bite block system can protected the normal tissue,and minimized the injury for border organs.Also it can separate the cancer lesion with border organs,which is helpful for the sketch of tumor targeting area,the precision of radiotherapy,and the control of radiotherapy dose.The methods deserved the clinical expansion.