• Int. J. Radiat. Oncol. Biol. Phys. · Dec 2010

    Dosimetric impact of online correction via cone-beam CT-based image guidance for stereotactic lung radiotherapy.

    • Ana Paula Galerani, Inga Grills, Geoffrey Hugo, Larry Kestin, Nasiruddin Mohammed, K Kenneth Chao, Andrew Suen, Alvaro Martinez, and Di Yan.
    • Department of Radiation Oncology, Clinirad, Angelina Caron Hospital, Curitiba, Parana, Brazil.
    • Int. J. Radiat. Oncol. Biol. Phys. 2010 Dec 1; 78 (5): 1571-8.

    PurposeTo evaluate the dosimetric impact of online cone-beam computed tomography (CBCT) guided correction in lung stereotactic body radiation therapy (SBRT).Methods And MaterialsTwenty planning and 162 CBCT images from 20 patients undergoing lung SBRT were analyzed. The precorrection CBCT (CBCT after patient setup, no couch correction) was registered to planning CT using soft tissue; couch shift was applied, with a second CBCT for verification (postcorrection CBCT). Targets and normal structures were delineated on CBCTs: gross tumor volume (GTV), clinical target volume (CTV), cord, esophagus, lung, proximal bronchial tree, and aorta. Dose distributions on all organs manifested on each CBCT were compared with those planned on the CT.ResultsWithout CBCT guided target position correction, target dose reduced with respect to treatment plan. Mean and standard deviation of treatment dose discrepancy from the plan were -3.2% (4.9%), -2.1% (4.4%), -6.1% (10.7%), and -3.5% (7%) for GTV D(99%), GTV D(95%), CTV D(99%), and CTV D(95%), respectively. With CBCT correction, the results were -0.4% (2.6%), 0.1% (1.7%), -0.3% (4.2%), and 0.5% (3%). Mean and standard deviation of the difference in normal organ maximum dose were 2.2% (6.5%) before correction and 2.4% (5.9%) after correction for esophagus; 6.1% (14.1%) and 3.8% (8.1%) for cord; 3.1% (17.5%) and 6.2% (9.8%) for proximal bronchial tree; and 17.7% (19.5%) and 14.1% (17%) for aorta.ConclusionOnline CBCT guidance improves the accuracy of target dose delivery for lung SBRT. However, treatment dose to normal tissue can vary regardless of the correction. Normal tissues should be considered during target registration, according to target proximity.Copyright © 2010 Elsevier Inc. All rights reserved.

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