characterizing treatment response of residual tumor. These images are obtained using an echo-planar 
sequence performed during the first 60 seconds after rapid intravenous infusion of gadopentetate 
dimeglumine contrast material. (5) Magnetization transfer contrast has proven useful in 
characterizing a variety of white matter abnormalities [48]. For the purpose of monitoring the 
effectiveness of therapy, we will investigate its ability to distinguish neoplastic tissue from 
encephalomalacia, radiation necrosis and regions containing edema with relatively few tumor cells. 
III.D.2 Positron emmislon tomography (PET) evaluation. 
Regional cerebral glucose metabolism will be measured using the FDG technique of Reivich et. al. [49]. 
A venous catheter will be inserted into an antecubital vein of one arm for the administration of FDG and 
second venous catheter will be inserted into the opposite hand for “arteriolized” blood sampling. FDG 
will then be administered as a bolus (114 mci/kg), 2 ml blood samples will be obtained every 15 
seconds for the first minute, then a less frequent intervals for the duration of the study. The blood 
samples will be centrifuged and aliquots of plasma analyzed for 18F activity and glucose concentration. 
Forty minutes after the administration of FDG, the patient will be positioned into the PENN PET scanner 
(UGM Medical Systems, Inc.). The PET scans will be acquired parallel to the canthomeal line and will 
include the entire brain. The total imaging time will be 30 minutes which in our experience is tolerated 
well by most patients. Regional glucose metabolic rates will be calculated using the operational 
equation, derived by Sokoloff et. al. [50] and as modified by Huang et. al. [49, 51] will be used in the 
calculation of the metabolic rates. 
The Penn-PET scanner is unique in its ability to sample continuously in the transverse and axial 
directions. It’s large field of view in the axial axis (12.8 x 9.5 cm) permits imaging of the entire brain 
in one data acquisition session. The spatial resolution of the system in 5.5 mm in all three planes, 
specifications that are unique to this instrument. This high resolution reduces partial volume effects, 
an important consideration with small or irregular shaped tumors. Slice thickness can be varied with 
this scanner and we will use 2 mm sampling in the z-axis for this study. The equally good spatial 
resolution in all planes allows the data to be treated as a volume and resliced along any planes for 
subsequent MRI and PET image superimposition and data analysis. 
FDG PET studies will be analyzed using PETVIEW, a SUN workstation-based program developed at PENN 
with UGM Medical Systems, Inc. This analysis system acquires data directly from a UGM PENN-PET 
SUN workstation and permits superimposition of PET and MRI images. MRI and PET images are 
constructed in the transverse plane and stacked to form a volume image. Each section is then resliced 
parallel to the anterior commissure-posterior commissure line using the OBLIQUE software module of 
PETVIEW. The slice containing caudate nucleus on PET and MRI is used as visual guide confirm the 
accuracy of image overlay and for positioning in the z-axis. 
We intend to use both qualitative (visual interpretation) as well as quantitative approach to determine 
the metabolic activity of the tumoral sites. Qualitative assessment will use the following grading system 
for FDG tumor uptake: (1) no FDG tumor uptake; (2) less than surrounding brain; (3) 
indistinguishable from adjacent brain; (4) slightly to moderately increased compared with adjacent 
brain; (5) markedly increased compared with adjacent brain. Quantitative assessment will include 
measurements of regional glucose metabolic rates and calculated ratios of tumor:normal brain [43] 
glucose utilization. Absolute glucose metabolic rate vary widely in brain tumors and their correlation 
with histology or clinical tumor to that of (a) whole brain, (b) contralateral white matter or (c) 
cerebellar hemisphere, are closely correlated with histology. Treatment response, survival and other 
clinical parameters. For this study, brain tumor boundaries will be identified on MR images, then 
superimposed on co-planner PET slices. Average, peak and decade profile (i.e., 10% bins) glucose 
metabolic rate values will be calculated for the tumor and for centrum semiovale white matter in the 
hemisphere contralateral to tumor. 
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