• Tomoki Kimura, Yutaka Hirokawa, Yuji Murakami, Masatsugu Tsujimura, Tateo Nakashima, Yoshimi Ohno, Masahiro Kenjo, Yuko Kaneyasu, Koichi Wadasaki, and Katsuhide Ito.
• Department of Radiology, Hiroshima University Graduate School of Medicine, Hiroshima, Japan. tkkimura@hiroshima-u.ac.jp
• Int. J. Radiat. Oncol. Biol. Phys. 2004 Nov 15; 60 (4): 1307-13.

PurposeTo evaluate in healthy volunteers the reproducibility of organ position using a voluntary breath-hold method with a spirometer and the feasibility of this method for extracranial stereotactic radiotherapy in a clinical setting.Methods And MaterialsFor this study, 5 healthy volunteers were enrolled. After training sessions, they held their breath at the end-inspiration and the end-expiration phase under spirometer-based monitoring. Computed tomography (CT) scans were performed twice at each respiratory phase, with a 10-min interval, on 2 separate days. The total number of CT scans was four at each respiratory phase. After CT volume data were transferred to a three-dimensional treatment-planning system, digitally reconstructed radiographs (DRRs) were calculated for anterior-posterior and left-right beams. Verification was performed with DRRs relative to the diaphragm position, bony landmarks, and the isocenter in each healthy volunteer at each respiratory phase. To evaluate intrafraction reproducibility, we measured the distance between diaphragm position and bony landmarks. To evaluate interfraction reproducibility, we measured the distance between diaphragm position and the isocenter. Reproducibility and setup error were defined as the average value of the differences between each DRR with regard to the first DRR.ResultsIntrafraction reproducibility of the caudal-cranial direction was 4.0 +/- 3.5 mm at the end-inspiration phase and 2.2 +/- 2.0 mm at the end-expiration phase. Interfraction reproducibility of the caudal-cranial direction was 5.1 +/- 4.8 mm at the end-inspiration phase and 2.1 +/- 1.8 mm at the end-expiration phase. The end-expiration phase was more stable than the end-inspiration phase.ConclusionsThe voluntary breath-hold method with a spirometer is feasible, with relatively good reproducibility. We are encouraged about the use of this technique clinically for extracranial stereotactic radiotherapy.

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