Correlation of lung tumor motion with external surrogate indicators of respiration

Int J Radiat Oncol Biol Phys. 2004 Nov 15;60(4):1298-306. doi: 10.1016/j.ijrobp.2004.07.681.

Abstract

Purpose: To assess the correlation of respiratory volume and abdominal displacement with tumor motion as seen with X-ray fluoroscopy. Measurements throughout the patient's treatment course allowed an assessment of the interfractional reproducibility of this correlation.

Methods and materials: Data were acquired from 11 patients; 5 were studied over multiple days. Measurements of respiratory volume by spirometry and abdominal displacement by a real-time position tracking system were correlated to simultaneously acquired X-ray fluoroscopy measurements of superior-inferior tumor displacement. The linear correlation coefficient was computed for each data acquisition. The phase relationship between the surrogate and tumor signals was estimated through cross-correlation delay analysis.

Results: Correlation coefficients ranged from very high to very low (0.99-0.39, p < 0.0001). The correlation between tumor displacement and respiratory volume was higher and more reproducible from day to day than between tumor displacement and abdominal displacement. A nonzero phase relationship was observed in nearly all patients (-0.65 to +0.50 s). This relationship was observed to vary over inter- and intrafractional time scales. Only 1 of 5 patients studied over multiple days had a consistent relationship between tumor motion and either surrogate.

Conclusions: Respiratory volume has a more reproducible correlation with tumor motion than does abdominal displacement. If forming a tumor-surrogate prediction model from a limited series of observations, the use of surrogates to guide treatment might result in geographic miss.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Female
  • Fluoroscopy
  • Humans
  • Lung Neoplasms / diagnostic imaging*
  • Lung Neoplasms / radiotherapy
  • Male
  • Middle Aged
  • Movement*
  • Reproducibility of Results
  • Respiration*
  • Spirometry