Abstract
The purpose of this work was to evaluate the intrapatient tumor position reproducibility in a deep inspiration breath‐hold (DIBH) technique based on two infrared optical tracking systems, ExacTrac and ELITETM, in stereotactic treatment of lung and liver lesions. After a feasibility study, the technique was applied to 15 patients. Each patient, provided with a real‐time visual feedback of external optical marker displacements, underwent a full DIBH, a free‐breathing (FB), and three consecutive DIBH CT‐scans centered on the lesion to evaluate the tumor position reproducibility. The mean reproducibility of tumor position during repeated DIBH was 0.5±0.3mm in laterolateral (LL), 1.0±0.9mm in anteroposterior (AP), and 1.4±0.9mm in craniocaudal (CC) direction for lung lesions, and 1.0±0.6mm in LL, 1.1±0.5mm in AP, and 1.2±0.4mm in CC direction for liver lesions. Intra‐and interbreath‐hold reproducibility during treatment, as determined by optical markers displacements, was below 1 mm and 3 mm, respectively, in all directions for all patients. Optically‐guided DIBH technique provides a simple noninvasive method to minimize breathing motion for collaborative patients. For each patient, it is important to ensure that the tumor position is reproducible with respect to the external markers configuration.PACS numbers: 87.53.Ly, 87.55.km
Highlights
Tumors in the thorax and upper abdomen are subject to respiratory-driven motion
We investigated the use of deep inspiration breath-hold (DIBH) technique in stereotactic treatments of lung and liver lesions using two infrared optical tracking systems, ExacTrac (BrainLAB AG, Germany) and ELITE (BTS S.p.a., Milan, Italy), in the attempt to either increase the dose or reduce the safety margin
Feasibility study of the reproducibility of DIBH technique Real-time visual feedback of marker displacements to the voluntary subjects led to a significantly higher repeatability of surface localization during DIBH, with overall mean 3D displacement of 2.2 ± 0.8 mm, compared to a mean value of 3.2 ± 1.1 obtained with verbal instructions given by an operator (p = 0.0003)
Summary
Tumors in the thorax and upper abdomen are subject to respiratory-driven motion. In conventional radiotherapy, large safety margins up to 2.0 cm are added to the clinical target volume (CTV) to account for breathing motion and setup errors.[1]. The breath-hold technique can be performed either at end of expiration, more reproducible but less comfortable for the patient, or at end of inspiration.[17] Deep inspiration breath-hold has particular advantages in lung tumors, allowing a reduction of lung density with a decrease of normal tissue in the high-dose region. This has the potential for dose escalation for the same calculated lung morbidity, even without margin reduction. The reduced target motion during DIBH may justify a smaller safety margin from CTV to planning target volume (PTV).(20)
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