DCEMRI of spontaneous canine tumors during fractionated radiotherapy: A pharmacokinetic analysis
Received 17 February 2009; received in revised form 28 July 2009; accepted 4 August 2009. published online 11 September 2009.
Abstract
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 54Gy given in 18 fractions. T1-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 kep 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 kep and the change in kep 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.
aDepartment of Radiation Biology, Oslo University Hospital, Oslo, Norway
bDepartment of Companion Animal Clinical Sciences, The Norwegian School of Veterinary Science, Oslo, Norway
cDepartment of Physics, University of Oslo, Oslo, Norway
dDepartment of Medical Physics, Oslo University Hospital, Oslo, Norway
eDepartment of Oncology, Oslo University Hospital, Oslo, Norway
fFaculty of Clinical Medicine, University of Oslo, Oslo, Norway
Corresponding author. Address: Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway.
ABSTRACT