PT  - JOURNAL ARTICLE
AU  - Oborski, Matthew
AU  - Laymon, Charles
AU  - Lieberman, Frank
AU  - Drappatz, Jan
AU  - Mountz, James
TI  - A DCE-MRI based approach to FLT PET ROI definition for early therapy response assessment in GBM.
DP  - 2015 May 01
TA  - Journal of Nuclear Medicine
PG  - 1788--1788
VI  - 56
IP  - supplement 3
4099  - http://jnm.snmjournals.org/content/56/supplement_3/1788.short
4100  - http://jnm.snmjournals.org/content/56/supplement_3/1788.full
SO  - J Nucl Med2015 May 01; 56
AB  - 1788 Objectives Heterogeneity in blood-brain-barrier (BBB) permeability confounds quantification of 18F-Fluorothymidine (FLT) PET of glioblastoma multiforme (GBM). Dynamic contrast enhanced MRI (DCE-MRI) measures permeability of tumor vasculature via the modeling parameter Ktrans. We explore a Ktrans based ROI definition method for quantifying FLT PET data.Methods N=3 GBM patients received baseline (BL) and early therapy assessment (ETA; 2 wks post-radio-chemo-therapy) dynamic FLT PET (Siemens HR+) and DCE-MRI (Siemens 3T TimTrio or 3T mMR) scans. PET acquisitions (68min) commenced with injection of 5mCi of FLT. DCE-MRI scans initiated with injection (Medrad injector) of 0.1mmol/kg of contrast agent (Magnevist). Voxelwise maps of Ktrans were computed from ETA DCE-MRI using a modified Tofts model and image based input function. Subject BL PET, ETA PET, and ETA Ktrans maps were co-registered to ETA contrast enhanced MRI (PMOD 3.5, PMOD Technologies Ltd). Two ROI were derived from each subject’s ETA Ktrans map using a threshold equal to half the maximum Ktrans value: voxels with Ktrans above the threshold formed the high Ktrans ROI, while voxels with Ktrans below the threshold formed the low Ktrans ROI. 2-tissue compartment modeling was used to compute subject specific FLT flux (KFLT ) for each ROI at each timepoint.Results Comparison of KFLT between high and low Ktrans ROI at BL showed larger KFLT values in the high Ktrans ROI compared to low Ktrans ROI for all subjects, while at ETA KFLT was larger in the high Ktrans ROI compared to the low Ktrans ROI for 2 of 3 subjects. KFLT decreased between BL and ETA timepoints in both the high and low Ktrans ROI for 2 subjects. For the third subject KFLT decreased between BL and ETA in the high Ktrans ROI, but increased in the low Ktrans ROI.Conclusions Regions of high Ktrans (suggesting comparatively higher BBB permeability) are associated with higher KFLT values compared to regions of low Ktrans.Research Support US National Institutes of Health research grants U01CA140230 and P30CA047904.