Reproducibility of organ position using voluntary breath-hold method with spirometer for extracranial stereotactic radiotherapy.
OBJECTIVE
To 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
For 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.


RESULTS
Intrafraction 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.


CONCLUSIONS
The 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.
Kimura
Tomoki
T
Department of Radiology, Hiroshima University Graduate School of Medicine, Hiroshima, Japan. tkkimura@hiroshima-u.ac.jp
Hirokawa
Yutaka
Y
Murakami
Yuji
Y
Tsujimura
Masatsugu
M
Nakashima
Tateo
T
Ohno
Yoshimi
Y
Kenjo
Masahiro
M
Kaneyasu
Yuko
Y
Wadasaki
Koichi
K
Ito
Katsuhide
K
D003964:Diaphragm / Q000000981:diagnostic imaging; D045853:Exhalation; D005240:Feasibility Studies; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000000981:diagnostic imaging; D009068:Movement; D015203:Reproducibility of Results; D013147:Spirometry; D013238:Stereotaxic Techniques; D035441:Thoracic Wall / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed