Application of the spirometer in respiratory gated radiotherapy

Tiezhi Zhang, Harry Keller, Matthew J. O'Brien, Thomas R. Mackie, Bhudatt Paliwal

Research output: Contribution to journalArticlepeer-review

107 Scopus citations


The signal from a spirometer is directly correlated with respiratory motion and is ideal for target respiratory motion tracking. However, its susceptibility to signal drift deters its application in radiotherapy. In this work, a few approaches are investigated to control spirometer signal drift for a Bernoulli-type spirometer. A method is presented for rapid daily calibration of the spirometer to obtain a flow sensitivity function. Daily calibration assures accurate airflow measurement and also reduces signal drift. Dynamic baseline adjustment further controls the signal drift. The accuracy of these techniques was studied and it was found that the spirometer is able to provide a long-term drift-free breathing signal. The tracking error is comprised of two components: calibration error and stochastic signal baseline variation error. The calibration error is very small (1% of 3 l) and therefore negligible. The stochastic baseline variation error can be as large as 20% of the normal breathing amplitude. In view of these uncertainties, the applications of spirometers in treatment techniques that rely on breathing monitoring are discussed. Spirometer-based monitoring is noted most suitable for deep inspiration breath-hold but less important for free breathing gating techniques.

Original languageEnglish
Pages (from-to)3165-3171
Number of pages7
JournalMedical physics
Issue number12
StatePublished - Dec 2003


Dive into the research topics of 'Application of the spirometer in respiratory gated radiotherapy'. Together they form a unique fingerprint.

Cite this