Imaging regional variation of cellular proliferation in gliomas using 3′-deoxy-3′-[18F]fluorothymidine positron-emission tomography: an image-guided biopsy study

AimTo compare regional variations in uptake of 3′-deoxy-3′- [18F]-fluorothymidine (FLT) images using positron-emission tomography (PET) with measures of cellular proliferation from biopsy specimens obtained by image-guided brain biopsies.Materials and methodsFourteen patients with a supratentorial glioma that required an image-guided brain biopsy were imaged preoperatively with dynamic PET after the administration of FLT. Maps of FLT irreversible uptake rate (Ki) and standardized uptake value (SUV) were calculated. These maps were co-registered to a gadolinium-enhanced T1-weighted spoiled gradient echo (SPGR) sequence that was used for biopsy guidance, and the mean and maximum Ki and SUV determined for each biopsy site. These values were correlated with the MIB-1 labelling index (a tissue marker of proliferation) from these biopsy sites.ResultsA total of 57 biopsy sites were studied. Although all measures correlated with MIB-1 labelling index, Kimax provided the best correlation (Pearson coefficient, r = 0.68; p < 0.001). In low-grade gliomas the Kimean (±SD) was significantly higher than in normal tissue (3.3 ± 1.7 × 10−3 mlplasma/min/mltissue versus 1.2 ± 0.7 × 10−3 mlplasma/min/mltissue; p = 0.001). High-grade gliomas showed heterogeneous uptake with a mean Ki of 7.7 ± 4 × 10−3 mlplasma/min/mltissue. A threshold Kimean of 1.8 × 10−3 differentiates between normal tissue and tumour (sensitivity 84%, specificity 88%); however, the latter threshold underestimated the extent of tumour in half the cases. SUV closely agreed with Ki measurements.ConclusionFLT PET is a useful marker of cellular proliferation that correlates with regional variation in cellular proliferation; however, it is unable to identify the margin of gliomas.