scholarly journals In vivo Muscarinic Cholingeric Receptor Imaging in Human Brain with [11C]Scopolamine and Positron Emission Tomography

1992 ◽  
Vol 12 (1) ◽  
pp. 147-154 ◽  
Author(s):  
K. A. Frey ◽  
R. A. Koeppe ◽  
G. K. Mulholland ◽  
D. Jewett ◽  
R. Hichwa ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Kinetic Analysis ◽  
Muscarinic Receptor ◽  
Emission Tomography ◽  
In Vivo Studies ◽  
Receptor Imaging ◽  
Arterial Blood ◽  
Positron Emission

Cerebral muscarinic cholinergic receptors were imaged and regionally quantified in vivo in humans with the use of [11C]scopolamine and positron emission tomography. Previous studies in experimental animals have suggested the utility of radiolabeled scopolamine for in vivo measurements, on the bases of its maintained pharmacologic specificity following systemic administration and the exclusion of labeled metabolites from the brain. The present studies describe the cerebral distribution kinetics of [11C]scopolamine in normal subjects following intravenous injection. Scopolamine is initially delivered to brain in a perfusion-directed pattern. After 30 to 60 min, activity is lost preferentially from cerebral structures with low muscarinic receptor density including the cerebellum and thalamus. Activity continues to accumulate throughout a 2 h postinjection period in receptor-rich areas including cerebral cortex and the basal ganglia. The late regional concentration of [11C]scopolamine does not, however, accurately parallel known differences in muscarinic receptor numbers in these receptor-rich areas. Tracer kinetic analysis of the data, performed on the basis of a three-compartment model, provides receptor binding estimates in good agreement with prior in vitro measurements. Kinetic analysis confirms significant contributions of ligand delivery and extraction to the late distribution of [11C]scopolamine, reconciling the discrepancy between receptor levels and tracer concentration. Finally, a novel dual-isotope method for rapid chromatographic processing of arterial blood samples in radiotracer studies is presented. The combination of rapid chromatography and compartmental analysis of tracer distribution should have broad utility in future in vivo studies with short-lived radioligands.

scholarly journals Serotonin 5HT2 Receptor Imaging in the Human Brain Using Positron Emission Tomography and a New Radioligand, [18F]Altanserin: Results in Young Normal Controls

1995 ◽  
Vol 15 (5) ◽  
pp. 787-797 ◽  
Author(s):  
B. Sadzot ◽  
C. Lemaire ◽  
P. Maquet ◽  
E. Salmon ◽  
A. Plenevaux ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
High Specific Activity ◽  
Emission Tomography ◽  
Binding Potential ◽  
Receptor Imaging ◽  
Time Activity ◽  
Arterial Blood ◽  
Positron Emission

Changes in serotonin-2 receptors have been demonstrated in brain autopsy material from patients with various neurodegenerative and affective disorders. It would be desirable to locate a ligand for the study of these receptors in vivo with positron emission tomography (PET). Altanserin is a 4-benzoylpiperidine derivative with a high affinity and selectivity for S2 receptors in vitro. Dynamic PET studies were carried out in nine normal volunteers with high-specific activity (376–1,680 mCi/μmol) [18F]altanserin. Arterial blood samples were obtained and the plasma time–activity curves were corrected for the presence of labeled metabolites. Thirty minutes after injection, selective retention of the radioligand was observed in cortical areas, while the cerebellum, caudate, and thalamus had low radioactivity levels. Specific binding reached a plateau between 30 and 65 min postinjection at 1.8% of the injected dose/L of brain and then decreased, indicating the reversibility of the binding. The total/nonspecific binding ratio reached 2.6 for times between 50 and 70 min postinjection. The graphical analysis proposed by Logan et al. allowed us to estimate the binding potential ( Bmax/ KD). Pretreatment with ketanserin was given to three volunteers and brain activity remained uniformly low. An additional study in one volunteer showed that [18F]altanserin can be displaced from the receptors by large doses of ketanserin. At the end of the study, unchanged altanserin was 57% of the total plasma activity. These results suggest that [18F]altanserin is selective for S2 receptors in vivo as it is in vitro. They indicate that [18F]altanserin is suitable for imaging and quantifying S2 receptors with PET in humans.

scholarly journals Development of a blood sample detector for multi-tracer positron emission tomography using gamma spectroscopy

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Carlos Velasco ◽  
Adriana Mota-Cobián ◽  
Jesús Mateo ◽  
Samuel España
Keyword(s):  
Positron Emission Tomography ◽  
Blood Sample ◽  
Pet Imaging ◽  
Spectroscopic Analysis ◽  
Gamma Spectroscopy ◽  
Emission Tomography ◽  
Blood Samples ◽  
Positron Emission

Abstract Background Multi-tracer positron emission tomography (PET) imaging can be accomplished by applying multi-tracer compartment modeling. Recently, a method has been proposed in which the arterial input functions (AIFs) of the multi-tracer PET scan are explicitly derived. For that purpose, a gamma spectroscopic analysis is performed on blood samples manually withdrawn from the patient when at least one of the co-injected tracers is based on a non-pure positron emitter. Alternatively, these blood samples required for the spectroscopic analysis may be obtained and analyzed on site by an automated detection device, thus minimizing analysis time and radiation exposure of the operating personnel. In this work, a new automated blood sample detector based on silicon photomultipliers (SiPMs) for single- and multi-tracer PET imaging is presented, characterized, and tested in vitro and in vivo. Results The detector presented in this work stores and analyzes on-the-fly single and coincidence detected events. A sensitivity of 22.6 cps/(kBq/mL) and 1.7 cps/(kBq/mL) was obtained for single and coincidence events respectively. An energy resolution of 35% full-width-half-maximum (FWHM) at 511 keV and a minimum detectable activity of 0.30 ± 0.08 kBq/mL in single mode were obtained. The in vivo AIFs obtained with the detector show an excellent Pearson’s correlation (r = 0.996, p < 0.0001) with the ones obtained from well counter analysis of discrete blood samples. Moreover, in vitro experiments demonstrate the capability of the detector to apply the gamma spectroscopic analysis on a mixture of 68Ga and 18F and separate the individual signal emitted from each one. Conclusions Characterization and in vivo evaluation under realistic experimental conditions showed that the detector proposed in this work offers excellent sensibility and stability. The device also showed to successfully separate individual signals emitted from a mixture of radioisotopes. Therefore, the blood sample detector presented in this study allows fully automatic AIFs measurements during single- and multi-tracer PET studies.

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