Search results for "positron"

Confinement-induced polymorphism in acetylsalicylic acid–nanoporous glass composites

2018

We report on the experimental observation of confinement-induced new phase appearance in acetylsalicylic acid (ASA)–porous glass (PG) composites. In this study, ASA was embedded in PG host matrices of various pore widths (15–200 nm). The Raman spectra and positron annihilation lifetime measurements exhibit the existence of ASA nanocrystals in the PG matrix. The DSC data revealed that the melting temperature TM and excess specific heat decrease with decreasing the size of embedded ASA nanocrystals. The close inspection of the TM dependence versus diameter of filled pores has shown that the ASA crystallizes in polymorph II in confined matrix. Moreover, it was demonstrated that the ASA spatial…

Scandium-44: Benefits of a Long-Lived PET Radionuclide Available from the 44Ti/44Sc Generator System

2011

(44)Ti/(44)Sc radionuclide generators are of interest for molecular imaging. The 3.97 hours half-life of (44)Sc and its high positron branching of 94.27% may stimulate the application of (44)Sc-labeled PET radiopharmaceuticals. This review describes the current status of (44)Ti production, (44)Ti/(44)Sc radionuclide generator development, post-processing of generator eluates towards medical application, identification of ligands adequate to Sc(III) co-ordination chemistry, proof-of-principle labeling of (44)Sc-DOTA-octreotides, investigation of in vitro and in vivo parameters, and initial applications for molecular imaging - both in small animals and humans.

Gamma-ray spectrometric measurement of radionuclide purity of radiopharmaceuticals contained in bottle samples

2012

The radionuclide purity of a radiopharmaceutical product is usually measured by gamma-ray spectrometry with various measurement geometries. The importance of this test is that the radionuclide impurities, if present, result in an increase in the radiation dose to the patient without contributing to diagnostic information and in some cases may also interfere with the marking molecules and affect the proper conduct of diagnostic examination. In this work, gamma-ray spectrometry is used to determine the amounts of impurities by adopting as measurement geometry the same bottle containing eluted or prepared radiopharmaceuticals. In addition to high-purity germanium semiconductor detectors, the u…

Plasmonic Biosensors for the Detection of Lung Cancer Biomarkers: A Review

2021

Lung cancer is the most common and deadliest cancer type globally. Its early diagnosis can guarantee a five-year survival rate. Unfortunately, application of the available diagnosis methods such as computed tomography, chest radiograph, magnetic resonance imaging (MRI), ultrasound, low-dose CT scan, bone scans, positron emission tomography (PET), and biopsy is hindered due to one or more problems, such as phenotypic properties of tumours that prevent early detection, invasiveness, expensiveness, and time consumption. Detection of lung cancer biomarkers using a biosensor is reported to solve the problems. Among biosensors, optical biosensors attract greater attention due to being ultra-sensi…

SU-E-I-83: Detectability Limits of a New Positron Emission Mammography in Relation to Tumour-Size, Tumour-To-Background Ratio and Activity Concentrat…

2017

Purpose:Positron emission mammography(PEM) improves spatial resolution and sensitivity, making it suitable for early breast tumours detection. The aim of this study is to evaluate the limits of a dedicated breast PET in terms of tumour‐size, tumour‐to‐background activity concentration ratio (TBR) and activity concentration. Methods: A dedicated PEM is evaluated. To characterize the device, we use a phantom of 15 cm of diameter containing 6 inserts of inner diameters 18, 15, 11, 8, 5 and 3 mm. To evaluate the detectability limits images are acquired by varying the TBR from 10 to 2 and without background activity concentration. In all the studies the activity concentration for the 6 inserts i…

Simulated one-pass list-mode: an approach to on-the-fly system matrix calculation.

2013

In the development of prototype systems for positron emission tomography a valid and robust image reconstruction algorithm is required. However, prototypes often employ novel detector and system geometries which may change rapidly under optimization. In addition, developing systems generally produce highly granular, or possibly continuous detection domains which require some level of on-the-fly calculation for retention of measurement precision. In this investigation a new method of on-the-fly system matrix calculation is proposed that provides advantages in application to such list-mode systems in terms of flexibility in system modeling. The new method is easily adaptable to complicated sy…

PET Chemistry: An Introduction

2021

One major advantage of radioactivity is its extremely high sensitivity of detection. Regarding the medical applicability of radioactivity, it permits non-invasive in vivo detection of radiolabelled compounds at nano- to picomolar levels. The use of substances at such low concentrations usually precludes a physiological, toxic or immunologic response of the investigated biological system. Consequently, the considered physiological process or system is examined in an unswayed situation. Furthermore, a wide range of substances, even those which are toxic at higher concentrations, become considerable for the development of radiopharmaceuticals and use in nuclear medicine. In contrast to the wid…

Whole-Body Magnetic Resonance Imaging: Current Role in Patients with Lymphoma.

2021

Imaging of lymphoma is based on the use of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) and/or contrast-enhanced CT, but concerns have been raised regarding radiation exposure related to imaging scans in patients with cancer, and its association with increased risk of secondary tumors in patients with lymphoma has been established. To date, lymphoproliferative disorders are among the most common indications to perform whole-body magnetic resonance imaging (MRI). Whole-body MRI is superior to contrast-enhanced CT for staging the disease, also being less dependent on histology if compared to 18F-FDG-PET/CT. As well, it does not require exposure to i…

Emission of thermal positrons from metal surfaces

1986

Measurement of cerebral ABCC1 transport activity in wild-type and APP/PS1-21 mice with positron emission tomography

2020

Previous data suggest a possible link between multidrug resistance-associated protein 1 (ABCC1) and brain clearance of beta-amyloid (Aβ). We used PET with 6-bromo-7-[11C]methylpurine ([11C]BMP) to measure cerebral ABCC1 transport activity in a beta-amyloidosis mouse model (APP/PS1-21) and in wild-type mice aged 50 and 170 days, without and with pretreatment with the ABCC1 inhibitor MK571. One hundred seventy days-old-animals additionally underwent [11C]PiB PET scans to measure Aβ load. While baseline [11C]BMP PET scans detected no differences in the elimination slope of radioactivity washout from the brain (kelim) between APP/PS1-21 and wild-type mice of both age groups, PET scans after MK…