Dosimetric comparison between jaw tracking and static jaw techniques in intensity-modulated radiotherapy
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RESEARCH
Open Access
Dosimetric comparison between jaw tracking and static jaw techniques in intensity-modulated radiotherapy Zhongsu Feng1, Hao Wu2, Yibao Zhang2, Yunjun Zhang3, Jinsheng Cheng1 and Xu Su1*
Abstract Purpose: To compare the dosimetric differences between jaw tracking technique (JTT) and static jaw technique (SJT) in dynamic intensity-modulated radiotherapy (d-IMRT) and assess the potential advantages of jaw tracking technique. Methods: Two techniques, jaw tracking and static jaw, were used respectively to develop the d-IMRT plans for 28 cancer patients with various lesion sites: head and neck, lungs, esophageal, abdominal, prostate, rectal and cervical. The dose volume histograms (DVH) and selected dosimetric indexes for the whole body and for organs at risk (OARs) were compared. A two dimensional ionization chamber Array Seven29 (PTW, Freiburg, Germany) and OCTAVIUS Octagonal phantom (PTW, Freiburg, Germany) were used to verify all the plans. Results: For all patients, the treatment plans using both techniques met the clinical requirements. The V5, V10, V20, V30, V40 (volumes receiving 5, 10, 20, 30 and 40 Gy at least, respectively), mean dose (Dmean) for the whole body and V5, V10, V20, Dmean for lungs in the JTT d-IMRT plans were significantly less than the corresponding values of the SJT d-IMRT plans (p < 0.001). The JTT d-IMRT plans deposited lower maximum dose (Dmax) to the lens, eyes, brainstem, spinal cord, and right optic nerve, the doses reductions for these OARs ranged from 2.2% to 28.6%. The JTT d-IMRT plans deposited significantly lower Dmean to various OARs (all p values < 0.05), the mean doses reductions for these OARs ranged from 1.1% to 31.0%, and the value reductions depend on the volume and the location of the OARs. The γ evaluation method showed an excellent agreement between calculation and measurement for all techniques with criteria of 3%/3 mm. Conclusions: Both jaw tracking and static jaw d-IMRT plans can achieve comparable target dose coverage. JTT displays superior OARs sparing than SJT plans. These results are of clinical importance, especially for the patients with large and complex targets but close to some highly radio-sensitive organs to spare, and for patients with local recurrent or secondary primary malignant lesion within a previously irradiated area. Keywords: Jaw tracking, IMRT, Dosimetry, OARs sparing
Introduction Nowadays, dynamic intensity-modulated radiotherapy (d-IMRT) is widely used in the treatment of cancer patients. Compared with three dimensional conformal radiotherapy, d-IMRT allows to increase the dose conformity of the target while decreasing normal tissue doses [1]. * Correspondence: [email protected] 1 Chinese Center for Medical Response to Radiation Emergency, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, 2 Xinkang Street, Deshengmenwai, Beijing 100088, China Full list of author information is available at the end of the article
In dynamic IMRT plans, the multi-leaf collimators (MLCs) translate
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