Related Experiment Video
Updated: Jan 9, 2026
Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
A prospective study using a spirometry-based system on the positional reproducibility of anatomical landmarks and
Noriko Kishi1, Yukinori Matsuo2, Mitsuhiro Nakamura3
1Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
Purpose:
This prospective study evaluated the positional reproducibility of anatomical landmarks and estimated planning target volume (PTV) margins using a spirometry-based system during deep inspiration breath-hold (DIBH), and evaluated the system's potential as a surrogate for dynamic tumour tracking (DTT).
Patients And Methods:
The study comprised two components, each involving 10 patients and utilising a spirometry-based system. Part A evaluated inter- and intra-fractional variations at 12 bronchial bifurcation landmarks and estimated PTV margins based on vertebral- and carina-based registrations. Part B assessed six 4D tumour position prediction models using varying ratios of spirometry- and surface-based inputs. The root-mean-square error (RMSE) was used to evaluate the prediction accuracy over two time intervals. For short-term evaluation, 20 s of data were used for model training, and the subsequent 50 s for validation. For long-term evaluation, a separate 70-second dataset was used.
Results:
In Part A, mean inter- and intra-fractional variations across the 12 landmarks were 4.2 ± 2.0 mm and 2.9 ± 2.0 mm, respectively. PTV margins remained < 5 mm for both registrations, except in the superior-inferior direction of the left anteromedial segment. In Part B, no significant RMSE differences were observed in short-term predictions. For long-term predictions, the spirometry-only and combined-input models showed significantly lower RMSE than the surface-only model (P = 0.049 and P = 0.021, respectively).
Conclusions:
Spirometry-based DIBH demonstrated acceptable positional reproducibility; however, individualised PTV margins may be necessary for specific regions. Spirometry-based prediction remained robust during free breathing, supporting its utility as a surrogate for DTT.
