1. Improving Ear Pain of Patients with Whole Brian Radiation Therapy
Using Intensity Modulated Arc Therapy
江品儀 Pin-Yi Chiang, 張志嘉 Chih-Chia Chang, 曾玉華 Yuk-Wah Tsang
戴德森醫療財團法人嘉義基督教醫院 放射腫瘤科
Department of Radiation Oncology , Ditmanson Medical Foundation Chia-Yi Christian Hospital
Purpose
The cancer patients with intracranial metastasis were traditionally treated by bilateral-field (BF) technique for whole brain radiation therapy (WBRT). The BF plan is simple and rough to save treatment time and planning time but the worse dose homogeneity may increase the complications of normal brain tissue and critical organs. A higher fractional dose, above 2.5Gy, is usually used in WBRT, and the higher doses would be distributed at bilateral cochleas of patients in BF plans, and cause earache in clinical experiences. The intensity modulated arc therapy (IMAT) technique can be used to decrease cochlear doses of WBRT plans, and compare with BF
technique.
Materials and Methods
The treatment fields and contours of whole brain PTV, bilateral cochleas and other critical organs of ten patients would be determined by one radiation oncologist (shown in Figure 1). Both IMAT and BF plans of each patient were planned with a prescribed dose of 30Gy in 12 fractions and normalized to 100% prescribed dose covered 99% PTV using Eclipse A10 treatment planning system. The maximal doses and the mean doses of bilateral cochleas would be calculated and normalized to compared by Wilcoxon signed-rank test.
Figure 1 The contours of whole brain PTV (blue line) and cochleas (pink line).
Results
The mean doses of right side cochlea were decreased from 30.66±0.20 Gy (BF) to ±0.78 Gy (IMAT) with p=0.005, and from 30.60±0.24 Gy (BF) to 22.77±1.09 Gy (IMAT) in left side with p= The maximal doses of right side cochlea were decreased from 31.49±0.42 Gy (BF) to 26.16±0.92 Gy (IMAT) with p=0.005, and from 31.30±0.32 Gy (BF) to 26.34±1.08 Gy (IMAT) in left side with p= The IMAT plans are also showed better dose coverage in nasofrontal area. (Figure 2)
Figure 2 The dose distributions of a IMAT plan and a BF plan from one patient. The red arrows show better dose coverage in frontal sinus area and blue arrow shows lower dose in bilateral cochleas.
IMAT plan
BF plan
Conclusion
Brain metastasis patients treated with IMAT techniques may decrease the radiation doses in their cochleas and improve their earache. The better dose coverage in nasofrontal area may also improve treatment quality.
Acknowledgement
This study was supported by Ditmanson Medical Foundation Chia-Yi Christian Hospital Research Program (R ).
Keywords IMAT, WBRT, earache