Voxel-Based Analysis of Dual-Time-Point ¹⁸F-FDG PET Images for Brain Tumor Identification and Delineation

Abstract

We have investigated dual-time-point 18 F-FDG PET for the detection and delineation of high-grade brain tumors using quantitative criteria applied on a voxel basis. Methods: Twenty-five patients with suspected high-grade brain tumors and inconclusive MRI findings underwent 11 C-methionine PET and dual-time-point 18 F-FDG PET. Images from each subject were registered and spatially normalized. Parametric maps of standardized uptake value (SUV) and tumor-to-normal gray matter (TN) ratio for each PET image were obtained. Tumor diagnosis was evaluated according to 4 criteria comparing standard and delayed 18 F-FDG PET images: any SUV increase, SUV increase greater than 10%, any TN increase, and TN increase greater than 10%. Voxel-based analysis sensitivity was assessed using 11 C-methionine as a reference and compared with visual and volume-of-interest analysis for dual-timepoint PET images. Additionally, volumetric assessment of the tumor extent that fulfills each criterion was compared with the volume defined for 11 C-methionine PET. Results: The greatest sensitivity for tumor identification was obtained with any increase of TN ratio (100%), followed by a TN increase greater than 10% (96%), any SUV increase (80%), and an SUV increase greater than 10% (60%). These values were superior to visual analysis of standard 18 F-FDG (sensitivity, 40%) and delayed 18 F-FDG PET (sensitivity, 52%). Volume-of-interest analysis of dual-time-point PET reached a sensitivity of only 64% using the TN increase criterion. Regarding volumetry, voxel-based analysis with the TN ratio increase as a criterion, compared with 11 C-methionine PET, detected 55.4% of the tumor volume, with the other criteria detecting volumes lower than 20%. Nevertheless, volume detection presented great variability, being better for metastasis (78%) and glioblastomas (56%) than for anaplastic tumors (12%). A positive correlation was observed between the volume detected and the time of acquisition of the delayed PET image (r 5 0.66, P , 0.001), showing volumes greater than 75% when the delayed image was obtained at least 6 h after 18 F-FDG injection. Conclusion: Compared with standard 18 F-FDG PET studies, quantitative dual-time-point 18 F-FDG PET can improve sensitivity for the identification and volume delineation of high-grade brain tumors.

Use of Dual-Point Fluorodeoxyglucose Imaging to Enhance Sensitivity and Specificity

“…Moreover, in 25 patients with suspected high-grade brain tumors and inconclusive MRI findings, quantitative DP FDG-PET improved the sensitivity for the identification and volume delineation of such neoplasms, when compared with standard single-time studies. 69 DP FDG-PET provided superior assessment of recurrence versus posttreatment necrosis in a group of 32 patients with treated brain metastases, lesion size Ͼ0.5 cm 3 , and suspected recurrence on MRI. 70 Early (45-60 minutes postinjection) or delayed (ϳ225 minutes later) SUVs of the lesion alone did not accurately differentiate between tumor and necrosis, whereas a change Ͼ19% of lesion to gray matter SUV ratios as a function of time was 95% sensitive, 100% specific, and 96% accurate (AUC 0.97) in making this differential diagnosis, regardless of histological type.…”

Quantitative volumetric analysis of gliomas with sequential MRI and 11C-methionine PET assessment: patterns of integration in therapy planning

“…PET examinations using radiolabelled amino acid such as L-(S-methyl-[ 11 C])methionine (MET) have been shown to be more efficient than 2-deoxy-2-[ 18 F] fluoro-D-glucose (FDG) in detecting and delineating the tumour extent, especially in low-grade gliomas and tumour recurrences [14,15], even when using dual time point FDG PET protocols [16]. Tumour delineation using MET and PET (MET PET) includes both solid tumour and areas of tumour infiltration with a sensitivity of 87% and a specificity of 89% compared with neuropathological findings [17].…”

Delayed FDG-Pet/Ct Images in Patients With Brain Tumors - Impact on Visual and Semiquantitative Assessment

“…The aim is to achieve optimal wash-out from the normal structures without reaching a nadir in tumor activity. There is some literature addressing the utilization of dual phase PET/CT of the brain with the delay interval ranging from 2 to 8 hours after FDG administration [11,12,13,14]. We also adopted this technique selecting a baseline registration at 60 th minute and a three-hour delay time for the second registration.…”