DCEMRI of spontaneous canine tumors during fractionated radiotherapy: a pharmacokinetic analysis

Radiother Oncol. 2009 Dec;93(3):618-24. doi: 10.1016/j.radonc.2009.08.012. Epub 2009 Sep 9.


Purpose: To estimate pharmacokinetic parameters from dynamic contrast-enhanced magnetic resonance (DCEMR) images of spontaneous canine tumors taken during the course of fractionated radiotherapy, and to quantify treatment-induced changes in these parameters.

Materials and methods: Six dogs with tumors in the oral or nasal cavity received fractionated conformal radiotherapy with 54 Gy given in 18 fractions. T(1)-weighted DCEMR imaging was performed prior to each treatment fraction. Time-intensity curves in the tumor were extracted voxel-by-voxel, and were fitted to the Brix pharmacokinetic model. The dependence of the pharmacokinetic parameters on the accumulated radiation dose was calculated.

Results: The Brix model reproduced the time-intensity curves well. A reduction in the k(ep) parameter with accumulated radiation dose was found for five (three significant) out of six cases, while the results for the A parameter were less consistent. Both pre-treatment k(ep) and the change in k(ep) with accumulated dose correlated significantly with tumor regression.

Conclusions: Pharmacokinetic parameters derived from DCEMR images taken during fractionated radiotherapy may predict response to radiotherapy. This may potentially impact on patient stratification and monitoring of treatment response for image-guided treatment strategies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Contrast Media* / pharmacokinetics
  • Dog Diseases / diagnosis
  • Dog Diseases / radiotherapy*
  • Dogs
  • Dose Fractionation, Radiation
  • Gadolinium DTPA* / pharmacokinetics
  • Magnetic Resonance Imaging / veterinary*
  • Mouth Neoplasms / diagnosis
  • Mouth Neoplasms / radiotherapy
  • Mouth Neoplasms / veterinary*
  • Nose Neoplasms / diagnosis
  • Nose Neoplasms / radiotherapy
  • Nose Neoplasms / veterinary*
  • Radiotherapy Dosage / veterinary
  • Radiotherapy, Conformal / veterinary*


  • Contrast Media
  • Gadolinium DTPA