1. Using Field-in-field Technique and Intensity Modulated Arc Therapy to Reduce the Posterior Scalp Doses in Whole Brain Radiation Therapy
江品儀 Pin-Yi Chiang1, 洪照雄 Chao-Hsiung Hung2,
張志嘉 Chih-Chia Chang1, 李政彥 Cheng-Yen Lee1, 曾玉華 Yuk-Wah Tsang1
戴德森醫療財團法人嘉義基督教醫院 放射腫瘤科 1
Department of Radiation Oncology , Ditmanson Medical Foundation Chia-Yi Christian Hospital
嘉義長庚紀念醫院放射腫瘤科2
Department of Radiation Oncology, Chiayi Chang Gung Memorial Hospital2
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 organsThe higher doses would be distributed at posterior scalps of patients in BF plans, and cause hair loss in clinical experiences. The field-in-field (FIF) technique and the intensity modulated arc therapy (IMAT) technique used in WBRT may reduce the hair follicle doses in posterior scalps.
Materials and Methods
The contours of whole brain PTV and the posterior scalps of ten patients would be determined by one radiation oncologist (shown in Figure 1) and checked by another one. The opposite treatment fields of BF plans were created and copied a pair of subfields and modified MLCs to create the FIF plans. All BF, FIF and IMAT 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 posterior scalp doses would be normalized to 2Gy fractions of biological equivalent dose and analyzed with Scheffe’s test.
Figure 1 The contours of whole brain PTV (blue line) and posterior scalp area (yellow line).
Results
The mean biological equivalent dose of the maximal doses in posterior scalp were decreased from 37.39±0.57 Gy in BF plans to ±0.42 Gy in FIF plans with p=0.005, and decreased to 31.34±0.57 Gy in IMAT plans with p< The mean biological equivalent dose of the mean doses in posterior scalp were decreased from 28.85±1.11 Gy in BF plans to 27.61±0.91 Gy in FIF plans with p=0.030, and decreased to 18.44±0.92 Gy in IMAT plans with p<0.001.
Conclusion
Both FIF technique and IMAT technique can reduce posterior scalp dose significantly, especially in the IMAT plan. Using FIF or IMAT technique can improve life quality and spare hairs in posterior scalps of WBRT patients.
Acknowledgement
This study was supported by Ditmanson Medical Foundation Chia-Yi Christian Hospital Research Program (R ).