Dosimetric Impact of Image-Guided Radiotherapy in Liver Stereotactic Radiotherapy |
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| Authors: | Cynthia L. Eccles Patricia E. Lindsay Tim D. Craig John J. Kim Laura A. Dawson |
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| Affiliation: | 1. Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto, Canada;2. Department of Radiation Oncology, University of Toronto, Toronto, Canada;1. Rapid Response Radiotherapy Program, Odette Cancer Centre, Toronto, Ontario, Canada;2. Department of Nursing, Odette Cancer Centre, Toronto, Ontario, Canada;3. Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada;4. Department of Psychiatry and Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada;1. Department of Radiation Oncology, ORLAM group, 44 rue ambroise Paré, Mâcon, France;2. Vision RT Ltd., Dove House, Arcadia Avenue London, N3 2JU, United Kingdom;1. IFCA Radiotherapy and Medical Physics Unit, Via del Pergolino, 1, 50139 Florence, Italy;2. AOU Careggi Medical Physics Unit, Largo Brambilla, 3, 50134 Florence, Italy;3. AOU Careggi Radiotherapy Unit, Largo Brambilla, 3, 50134 Florence, Italy;4. University of Florence, Department of Clinical and Experimental Biomedical Sciences “Mario Serio”, Viale Morgagni 50, 50134 Florence, Italy;1. Department of Oncology, Clínica Universidad de Navarra, Madrid, Spain;2. School of Medicine, Complutense University, Madrid, Spain;3. Department of General Surgery, Hospital General Universitario Gregorio Marañón, Institute for Sanitary Research Gregorio Marañón (IiSGM), Madrid, Spain, Complutense University of Madrid, Madrid, Spain;4. Department of Radiotherapy and Radio-Oncology, Paracelsus Medical University Hospital Salzburg, Landeskrankenhaus, Salzburg, Austria;5. CCU Molecular Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany;6. Department of Radiotherapy, Helios Hospital Berlin-Buch, Berlin, Germany;7. Paris Sciences & Lettres PSL University, Paris, France;8. Department of Radiation Oncology, University Hospital of Heidelberg, Heidelberg, Germany;9. Radiotherapy Unit, Department of Translation Medicine, University of Piemonte Orientale, Novara, Italy |
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| Abstract: | IntroductionIn the absence of volumetric image-guided radiotherapy (IGRT) with or without intravenous contrast, IGRT with two-dimensional (2D) imaging can improve the accuracy and precision of radiation delivery by correcting the largest sources of geometric uncertainty, facilitating the delivery of higher doses to the tumor and/or reduced doses to normal tissues. The purpose of this work was to estimate dosimetric impact of 2D IGRT for patients undergoing breath hold liver stereotactic body radiotherapy (SBRT).Materials/MethodsOffline residual offsets were determined using orthogonal image pairs acquired with patients positioned with external setup marks (non-IGRT) and following IGRT and repositioning (IGRT) for 30 patients treated with 6-fraction liver SBRT. The diaphragm was used as a surrogate for the liver for craniocaudal positioning, and the vertebral bodies for anterioposterior and right-left positioning, with a 3-mm threshold. The planned dose distributions were shifted by the measured IGRT and non-IGRT offsets. Total doses to target volumes and organs at risk (OAR) were calculated and compared to the prescribed plans.ResultsA total of 643 images (416-MV electronic portal images; 227 kV cone beam computed tomography projection images) were evaluated. Residual non-IGRT offsets frequently exceeded 3 mm (72%), resulting in clinically significant variations from the prescribed minimum planning target volume dose (mean change –6.5 Gy; P =.0150). The population mean reductions in minimum gross tumor volume doses (standard deviation (σ) to 0.5 mL with were 7.2 Gy (6.3) and 4.7 Gy (6.1) for non-IGRT and IGRT, respectively. The mean population increase in maximum OAR dose (to 0.5 mL) was largest for bowel (2.7 Gy, σ = 5.5 Gy) for non-IGRT.ConclusionsIGRT significantly improves concordance of delivered doses with planned doses for liver target volumes and OARs. |
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