Radioactive Tracers

The natural radioactivity of K40, Th232and Ra226 in rocks and soils samples collected around Aurangabad-Maharashtra in India. The concentration of radionuclide in samples were determined by gamma-ray spectrometer NaI(Tl) detector. The aim of the present work is to measure the levels of natural radioactivity in the selected samples. In addition to this radiological hazard assessment due to natural radionuclide carried out and the average activity concentration of 226Ra, 232Th, 40K were determined. The Radium equivalent, air absorbed gamma radiation dose rate and external radiation hazard index and the annual effective radiation dose were calculated in this study

Molecular imaging methods such as positron emission tomography (PET) are increasingly involved in the development of new drugs. Using radioactive tracers as imaging probes, PET allows the determination of the pharmacokinetic and pharmacodynamic properties of a drug candidate, via recording target engagement, the pattern of distribution, and metabolism. Because of the noninvasive nature and quantitative end point obtainable by molecular imaging, it seems inherently suited for the examination of a pharmaceutical's behavior in the brain. Molecular imaging, most especially PET, can therefore be a valuable tool in CNS drug research. In this Perspective, we present the basic principles of PET, the importance of appropriate tracer selection, the impact of improved radiopharmaceutical chemistry in radiotracer development, and the different roles that PET can fulfill in CNS drug research.

We have prepared five new analogs (n-propyl, iso-propyl, allyl, n-butyl, and iso-butyl) of the dopamine D-2 receptor antagonist, FPMB which result from modifications of the ethyl group at the pyrrolidine nitrogen in FPMB. As expected, all new derivatives showed higher apparent lipophilicity (log kw), with iso-butyl being the most lipophilic (log kw = 2.52), followed by the allyl derivative (log kw = 2.43). The allyl group showed the largest increase in affinity (from 0.26 nM for the ethyl substituent to 0.03 nM for the allyl substituent, almost 10-fold), followed by the n-propyl substituent which showed approximately five-fold better affinity than did the ethyl substituent. Radiosynthesis of (S)-N-[(1-allyl-2-pyrrolidinyl)methyl]-5-(3-[18F]fluoropropyl)-2, 3-dimethoxybenzamide ([18F]fallypride) was carried out by nucleophilic substitution reaction of (S)-N-[(1-allyl-2-pyrrolidinyl) methyl]-5-(3-tosyloxypropyl)-2,3-dimethoxybenzamide with no carrier added 18F-. [18F]Fallypride was ob...

Sentinel lymph node biopsy (SLNB) is the standard of care for axillary staging in early breast cancer. Currently, no consensus exists on the optimal site of injection of the radioactive tracer or blue dye. A systematic review and meta-analysis of studies comparing superficial and deep injections of radioactive tracer or blue dye for lymphatic mapping and SLNB was performed. The axillary and extra-axillary sentinel lymph node (SLN) identification rates obtained by lymphoscintigraphy and intraoperative SLNB were evaluated. Pooled odds ratios (ORs) and 95 per cent c.i. were estimated using fixed-effect analyses, or random-effects analyses if there was statistically significant heterogeneity (P < 0·050). Thirteen studies were included in the meta-analysis. There was no significant difference between superficial and deep injections of radioactive tracer for axillary SLN identification on lymphoscintigraphy (OR 1·59, 95 per cent c.i. 0·79 to 3·17), during surgery (OR 1·27, 0·60 to 2·68...

This paper describes the development and standardization of a profilometry-based method for assessment of dentifrice abrasivity called Radioactive Dentin Abrasivity - Profilometry Equivalent (RDA-PE). Human dentine substrates are mounted in acrylic blocks of precise standardized dimensions, permitting mounting and brushing in V8 brushing machines. Dentin blocks are masked to create an area of "contact brushing." Brushing is carried out in V8 brushing machines and dentifrices are tested as slurries. An abrasive standard is prepared by diluting the ISO 11609 abrasivity reference calcium pyrophosphate abrasive into carboxymethyl cellulose/glycerin, just as in the RDA method. Following brushing, masked areas are removed and profilometric analysis is carried out on treated specimens. Assessments of average abrasion depth (contact or optical profilometry) are made. Inclusion of standard calcium pyrophosphate abrasive permits a direct RDA equivalent assessment of abrasion, which ...

In the present investigation we have characterized strong and weak base anion exchange resins on the basis of their performance under different operational parameters. The radioactive tracer isotopes 131I and 82Br were used to trace the ion-isotopic exchange reactions. In case of iodide and bro mide ion-isotopic exchange reactions using both the resins, there exists a strong positive correlationship between amount of ions exchanged and ionic concentration, while strong negative correlationship exist between amount of ions exchanged and temperature of exchanging mediu m. The values of specific reaction rates (min-1), percentage / amount of ions exchanged, and distribution coefficient calculated for Duolite A-611 were higher than that calculated for Ind ion-870, indicating superior performance of Duolite A-611 over Indion-870.

This article addresses to the fundamental approaches for signal acquisition in Brain-Computer-Interface technology. Signal acquisition approaches are broadly classified into three major categories as Invasive-Approach, Semi-Invasive-Approach and Non-Invasive-Approach. In this context first of all we discussed the invasive approach in which electrical signals to be extracted from gray matter of the brain by neurosurgery, than semi invasive approach discussed in which electrical signals to be extracted from outside the gray matter by using electrocorticography technique. After that we discussed non invasive approach in detail including various techniques as EEG, MEG, EMG, MRI, TMS, PET, CT, NIRS, EROS, fNIRS, and fMRI.

This article reviews positron emission tomography (PET) studies of labeled enantiomers of different PET-tracers from the early 1980s. Comparative studies on stereoselective behavior of the transport of tracers across the blood-brain barrier (BBB) are discussed. Tracers are transported through the BBB into the brain, via diffusion or via several transport systems. These transport systems are able to transport endogenous and exogenous compounds from the blood into the brain, and visa versa. A clear difference exists in BBB transport of the enantiomers of several tracers. In addition, in most cases, binding of these labeled enantiomers to receptors/transporters is stereoselective. Finally, use of the biological inactive labeled enantiomer for the measurement of nonspecific binding is discussed.Given the differences in transport and binding, it is concluded that quantitative PET studies can only be performed using pure enantiomers.

This paper describes the development and standardization of a profilometry-based method for assessment of dentifrice abrasivity called Radioactive Dentin Abrasivity - Profilometry Equivalent (RDA-PE). Human dentine substrates are mounted in acrylic blocks of precise standardized dimensions, permitting mounting and brushing in V8 brushing machines. Dentin blocks are masked to create an area of "contact brushing." Brushing is carried out in V8 brushing machines and dentifrices are tested as slurries. An abrasive standard is prepared by diluting the ISO 11609 abrasivity reference calcium pyrophosphate abrasive into carboxymethyl cellulose/glycerin, just as in the RDA method. Following brushing, masked areas are removed and profilometric analysis is carried out on treated specimens. Assessments of average abrasion depth (contact or optical profilometry) are made. Inclusion of standard calcium pyrophosphate abrasive permits a direct RDA equivalent assessment of abrasion, which ...

The use of deuterated water as a method to measure gluconeogenesis has previously been well validated and is reflective of normal human physiology. However, there has been concern since the method was first introduced that transaldolase exchange may lead to the overestimation of gluconeogenesis. We examined the impact of transaldolase exchange on the estimation of gluconenogenesis using the deuterated water method under a variety of physiological conditions in humans by using the gluconeogenic tracer [U-13C]propionate, 2H2O, and 2H/13C nuclear magnetic resonance (NMR) spectroscopy. When [U-13C]propionate was used, 13C labeling inequality occurred between the top and bottom halves of glucose in individuals fasted for 12–24 h who were weight stable ( n = 18) or had lost weight via calorie restriction ( n = 7), consistent with transaldolase exchange. Similar analysis of glucose standards revealed no significant difference in the total 13C enrichment between the top and bottom halves of...

Aminopeptidase N (APN/CD13) plays an important role in tumor neoangiogenic process and the development of metastases. Furthermore, it may serve as a potential target for cancer diagnosis and therapy. Previous studies have already shown that asparagine-glycine-arginine (NGR) peptides specifically bind to APN/CD13. The aim of the study was to synthesize and investigate the APN/CD13 specificity of a novel (68)Ga-labeled NOTA-c(NGR) molecule in vivo using miniPET. c[KNGRE]-NH2 peptide was conjugated with p-SCN-Bn-NOTA and was labeled with Ga-68 ((68)Ga-NOTA-c(NGR)). Orthotopic and heterotopic transplanted mesoblastic nephroma (NeDe) bearing Fischer-344 rats were prepared, on which biodistribution studies and miniPET scans were performed for both (68)Ga-NOTA-c(NGR) and ανβ3 integrin selective (68)Ga-NODAGA-[c(RGD)]2 tracers. APN/CD13 receptor expression of NeDe tumors and metastases was analyzed by western blot. (68)Ga-NOTA-c(NGR) was produced with high specific activity (5.13-5.92GBq/μm...