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¹⁸F-FDOPA Kinetics in Brain Tumors

¹ Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, California; and ² Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, California

View larger version (13K): [in this window] [in a new window]   FIGURE 1.  Biochemical pathways of 18F-FDOPA after administration in venous circulation. Metabolite OMFD is produced in blood and liver and in negligible amounts in brain and is transported bidirectionally. Because this metabolite still has 18F label, it cannot be distinguished from injected tracer 18F-FDOPA. In brain, 2 compartments are considered: one with unbound 18F-FDOPA and another with bound (metabolized) tracer. Question mark indicates that role of 18F-FDOPA in third compartment of tumors is not known. FDA = 6-fluorodopamine; FDOPAC = 6-fluoro-3,4-dihydroxyphenylacetic acid; FHVA = 6-fluorohomovanillic acid. Adapted from Huang et al. (16).

View larger version (39K): [in this window] [in a new window]   FIGURE 2.  Factor images for 24-y-old woman with newly diagnosed brain tumor. Pathology revealed grade III oligodendroglioma. (A) Vascular factor images of transverse (arrows) and cavernous (arrowhead) sinuses. (B) Factor images of tumor located in right frontal lobe. (C) Striatum with some asymmetry in caudate nucleus and globus pallidus because of head tilt. Note inferior edge of right frontal tumor in plane P 27.

View larger version (9K): [in this window] [in a new window]   FIGURE 3.  Typical time–activity curves for striatum (), cerebellum (), and tumor (). Maximum uptake in tumor was higher than that in striatum. Note early steep ascent in tumor curve and parallel patterns of tumor and cerebellum curves. In contrast, striatum had active metabolism, leading to plateau-shaped curve.

View larger version (16K): [in this window] [in a new window]   FIGURE 4.  Kinetic parameters obtained with 3-compartment model and corrections for metabolites and partial volume. Average results for 45 studies of different structures are shown. Error bars denote SDs. Only one malignant tumor was selected per patient. Values for k1–k4 and K are given in minutes–1. Vb = blood volume fraction in tissue.

View larger version (16K): [in this window] [in a new window]   FIGURE 5.  Average values of kinetic parameters for high-grade tumors (n = 18), low-grade tumors (n = 11), tumors with predominantly posttreatment (Rx) changes (n = 6), and benign lesions (n = 2) in brain. Error bars denote SDs. Values for k1–k4 and K are given in minutes–1. Vb = blood volume fraction in tissue.

View larger version (8K): [in this window] [in a new window]   FIGURE 6.  Plot of equilibrium distribution volume (Ved = k1/k2) for newly diagnosed tumors. High- and low-grade tumors formed separate subgroups. High grade: 4 patients with 9 tumors. Low grade: 5 patients with 7 tumors. 2C = 2-compartment model; 3C– = 3-compartment model without metabolite correction; 3C+ = 3-compartment model with metabolite correction.