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SU‐E‐T‐225: A Comprehensive Evaluation of Real‐Time Motion Tracking of a Surface Imaging System for Lung Treatment
Author(s) -
Jin H,
Su Z
Publication year - 2012
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 - 10.1118/1.4735288
Subject(s) - imaging phantom , breathing , nuclear medicine , frame rate , coronal plane , tracking (education) , medicine , match moving , medical imaging , biomedical engineering , physics , motion (physics) , computer science , optics , computer vision , radiology , anatomy , psychology , pedagogy
Purpose: Applicability of the AlignRT surface imaging system was extensively investigated for real‐time motion tracking in radiation therapy of lung cancer. Methods: A 4D computer‐controlled motion phantom was employed to simulate a human breathing motion. An anthropomorphic thoracic phantom (a coronal cross‐sectional area: ∼1,200 cm 2 ) was monitored during the 4D motion tracking. A breathing cycle from a healthy subject (breathing frequency: 0.2 Hz; maximum amplitude: vertical 7 mm, longitudinal 6 mm, and lateral 1.2 mm) was monitored and fed into the phantom control system. The real time monitoring was investigated by modifying a region of detection (the whole, a half, and a quarter of the area) and combination of 3 cameras (patient left, middle, and right). Results: The real‐time tracking errors (detected breathing motion ‐ the input of the subject's breathing) of the phantom motion using one camera (lateral, longitudinal, vertical) were (0.02±0.14 mm, −0.23±0.48 mm, −0.10±0.48 mm) with ipsilateral halves of the area (frame rate: 1.52 Hz), (0.06±0.10 mm, −0.30±0.30 mm, ‐0.03−0.35 mm) with ipsilateral quarters (frame rate: 1.95 Hz), and (0.19±0.96 mm, 0.29±1.50 mm, −0.46±1.58 mm) with contralateral quarters (frame rate: 3.04 Hz). The detection errors using 2‐camera combinations (left‐middle and right‐middle) were (−0.06±0.06 mm, −0.43±0.21 mm, 0.00±0.22 mm) for the ipsilateral quarters and (−0.62±0.18 mm, −1.20±0.37 mm, 0.03±0.30 mm) for the contralateral quarters, respectively. The 3‐camera tracking using halves of the area presented an error of (−0.04±0.12 mm, −0.69±0.35 mm, −0.08±0.38 mm) with a frame rate of 0.62 Hz. Conclusions: To guarantee a sub‐millimeter accuracy of realtime motion tracking in the lung treatment, combination of 2 cameras or less, a frame rate of greater than the Nyquist frequency (in this study fN = 2B (breathing frequency) = 0.4 Hz), and a tracking area of less than an ipsilateral half of thoracic area is highly recommended.