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摘要：Although magnetic resonance imaging (MRI) is highly effective in identifying tumor location or size and in detecting even small intracranial lesions, it remains often difficult of differentiating between viable tumor tissue and postsurgical morphological changes such as gliosis or tumor-associated brain edema. PET may help to overcome this dilemma of diagnosis.

PET represents an analytical imaging technology developed to use compounds labeled withpositronemitting radioisotopes as molecular probes to image and measure biochemical processes of mammalian biology in vivo.

C11 - L-methyl methionine , Raclopride C 11, [[11C]DASB] are the 3 tracers used in PET brain imaging apart from the most commonly used FDG.

C11 - L-methyl methionine

Carbon-11 methionine is another radiopharmaceutical that can be used for tumor imaging. Its uptake reflects increased amino acid transport and protein synthesis and is related to cellular multiplication activity .

Pharmacokinetics

In the evaluation of brain lesions, 11C-methionine has advantages over 18F-FDG, stemming primarily from its low uptake in the normal brain.However,18F-FDG can be synthesized more easily, is more widely available, and has a longer half-life than 11C-methionine of 20 minutes. These factors hinder the clinical application of 11C-methionine.

Distribution

Methionine and other large neutral AA are transported across the BBB and cell membranes by a particular carrier system mediated through the sodium-independent L-transport system in the luminal membrane of endothelial cells.

The methionine uptake does not directly reflect protein synthesis, but it represents cell avidity for AA, which relates to the activity of the transport system and incorporation in proteins.

METHOD OF ANALYSIS:

The tumor ROIs were defined on the T1 weighted MRI with Gadolinium DTPA scans, followed by the transverse slices of the11C-Met PETscans .The tumor ROI was then mirrored to the contralateral side (tumor mirror region).

NOTE: [11C-Met uptake ratios :a) tumor/wm�average tumor tissue uptake divided by the white matter uptake,b) tumor max/wm�the peak tumor tissue uptake divided by the white matter uptake,c) https://www.51lunwen.org/dxygassignment/ tumor/mirror�average tumor tissue uptake divided by the average mirror region uptake.]

A representation and interpretation of the area under a receiver operating characteristic (ROC) curve obtained by the 'rating' method, or by mathematical predictions based on patient characteristics, is presented. It is shown that in such a setting the area represents the probability that a randomly chosen diseased subject is ranked with greater suspicion than a randomly chosen non-diseased subject (2).

The study done by Borb�ly et al., 2006 reveals that receiver-operating-curve analysisis as the preferred semi-quantitative analysisi method .It showed that characteristic (ROCs) curves of the uptake ratios of the parameter tumor/mirror11C-Met can be the suitable ratio for a higher sensitivity and specificity.

Clinically

•Methionine-PET scanning has been proved to be helpful for brain tumor diagnosis and delineation.
•The studies overcome the difficulty in differentiating brain tumors from other cerebral pathologies that is, infections, radiation necrosis, or brain edema formation, especially for determining their tumoral boundaries.
•It has been reported to offer a reliable diagnostic method for differentiation between recurrent malignant astrocytoma and radiation necrosis or gliosis.

Raclopride C 11

Raclopride C 11, commonly referred to as [O-methyl-11C] raclopride . Raclopride, a compound of the salicylami本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。