Improving IMRT dose accuracy via deliverable Monte Carlo optimization for the treatment of head and neck cancer patients
- Radiation Oncology Department, Virginia Commonwealth University Medical Center, 401 College Street, Richmond, Virginia 23298 (United States)
The purpose of this work is to investigate the effect of dose-calculation accuracy on head and neck (H and N) intensity modulated radiation therapy (IMRT) plans by determining the systematic dose-prediction and optimization-convergence errors (DPEs and OCEs), using a superposition/convolution (SC) algorithm. Ten patients with locally advanced H and N squamous cell carcinoma who were treated with simultaneous integrated boost IMRT were selected for this study. The targets consisted of gross target volume (GTV), clinical target volume (CTV), and nodal target volumes (CTV nodes). The critical structures included spinal cord, parotid glands, and brainstem. For all patients, three IMRT plans were created: A: an SC optimized plan (SC{sub opt}), B: an SC{sub opt} plan recalculated with Monte Carlo [MC(SC{sub opt})], and C: an MC optimized plan (MC{sub opt}). For each structure, DPEs and OCEs were estimated as DPE{sub SC}=D{sup B}-D{sup A} and OCE{sub SC}=D{sup C}-D{sup B} where A, B, and C stand for the three different optimized plans as defined above. Deliverable optimization was used for all plans, that is, a leaf-sequencing step was incorporated into the optimization loop at each iteration. The range of DPE{sub SC} in the GTV D{sub 98} varied from -1.9% to -4.9%, while the OCE{sub SC} ranged from 0.9% to 7.0%. The DPE{sub SC} in the contralateral parotid D{sub 50} reached 8.2%, while the OCE{sub SC} in the contralateral parotid D{sub 50} varied from 0.91% to 6.99%. The DPE{sub SC} in cord D{sub 2} reached -3.0%, while the OCE{sub SC} reached to -7.0%. The magnitude of the DPE{sub SC} and OCE{sub SC} differences demonstrate the importance of using the most accurate available algorithm in the deliverable IMRT optimization process, especially for the estimation of normal structure doses.
- OSTI ID:
- 20853691
- Journal Information:
- Medical Physics, Vol. 33, Issue 11; Other Information: DOI: 10.1118/1.2357835; (c) 2006 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
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