Dosimetric Comparisons among Different Techniques of Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma
| Autor: | Szu-Huai Lu, 陸思慧 |
|---|---|
| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 Radiation therapy plays an important role in nasopharyngeal carcinoma（NPC） treatment. Its advances in treatment technology not only improve tumor control probability (TCP), but also lower normal tissue complication probability (NTCP). Intensity modulation radiation therapy (IMRT) has greatly mitigated the shortcomings of traditional radiotherapy by reducing the damage to normal tissues, particularly to the salivary glands. A newly developed technique, helical TomoTherapy (HT) and volumetric modulated arc therapy (VMAT), combines inverse planning of intensity modulation and a full 360° radiation beam direction resulting in better dosage conformity for the NPC treatment with lower doses to the surrounding organs at risk. A total of 20 consecutive NPC patients treated by HT were enrolled in this study. Their treatments were re-planned using VMAT and IMRT with the same imaging sets and patient contours for the retrospective study in dosimetric comparison. The plans were evaluated by isodose curves, dose-volume histograms（DVH）and delivery efficiency. The study results demonstrated that with the same target coverage, radiation therapy using VMAT and HT could provide better homogeneity. However, HT attained significantly better conformity than VMAT and IMRT. In terms of normal tissue protection, with the exception of maximum doses to the eyes and the optic nerves, where IMRT and HT each has their own advantages and disadvantages due to different design criteria, VMAT and HT in general provide better dose sparing to the OARs, especially the mean dose to parotid glands. VMAT outperformed HT and IMRT by lower treatment time and monitor units (MUs) and thereby relieve the patients from discomfort and avoid body motion due to prolonged treatment time. VMAT and HT are suitable for nasopharyngeal carcinoma treatment and expected to reduce the patient discomfort during the course of treatment and long-term side effects with better plan quality. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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