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SU‐FF‐J‐17: Accuracy and Dosimetric Advantage of Target Localization Using Stereoscopic Image‐Guided Radiotherapy for Lung Cancer Treatment
Author(s) -
Ding M,
Stuhr K,
Newman F,
Johnson T,
Kavanagh B
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2240796
Subject(s) - isocenter , image guided radiation therapy , medicine , radiation therapy , nuclear medicine , lung cancer , radiation treatment planning , radiology
Purpose: We analyzed the accuracy of stereoscopic image‐guided radiotherapy (S‐IGRT) with the ExacTrac® system (BrainLAB AG, Heimstetten, Germany), and demonstrated the dosimetric advantage for lung cancer treatment. Methods: The accuracy of target localization using the ExacTrac system was analyzed by re‐scanning ten patients immobilized in the Vac‐loc bag with BB tags put on the isocenter marks determined by the ExacTrac system. The re‐scanned CT data from each patient was fused and compared to the isocenter locations on the original CT used for the treatment planning. The Active Breathing Coordinator™ (Elekta, Norcross, GA) was employed to minimize the breathing motion effect on S‐IGRT. The dosimetric advantage of S‐IGRT was demonstrated by comparing the normal lung volume receiving 15%, 30% and 50% of the prescription dose (V 15% , V 30% and V 50% ) between the plans with smaller margins in the S‐IGRT and those with normal margins in the conventional radiotherapy for the ten patients. Results: The average isocenter shifts using S‐IGRT were within 3.4 ±1.7mm in the lateral, 3.6±1.9mm in the anterior/posterior, and 2.2±3.2mm in the superior/inferior directions. The added margins around the CTV to create the PTV were chosen to be 10mm in the superior/inferior and 5mm in radial direction for the lung cancer treatment planning in S‐IGRT. For the ten patients with CTV volume from 8.3cm 3 to 43.4cm 3 and lung volume from 2736cm 3 to 3640cm 3 , the averages of V 15% , V 30% and V 50% were 17.4%, 9.8%, 5.9% for the S‐IGRT plans, and 33.4%, 18.2%, 12.8% for the conventional radiotherapy plans with 2cm margins in the all directions. Conclusion: The S‐IGRT with the ExacTrac system provided highly accurate tumor localization. The margins from CTV to PTV in S‐IGRT treatment planning could be reduced significantly due to the accurate target localization which will reduce the lung volume receiving doses in the medium and low ranges.