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Scintillation Detectors
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
The development of gas ionization chambers and associated electronic circuitry in the 1930s eventually made these men obsolete since it provided the users with a possibility not only to more precisely quantify the individual ionization events, but the measurements could also be performed at much higher count rates than what the human eye could accomplish and, more importantly, this development could detect not only alpha particles but also the weaker ionizing β-particles. Prior to 1930, scintillation screens of barium platinocyanide or artificially made willemite (a natural highly fluorescent zinc silicate mineral), were used as alternatives to activated zinc sulphide for visual scintillation counting. The disadvantage of these scintillators was that they were only available as small crystals or crystalline powders and the ZnS(Ag) scintillator had a severe shortcoming in that it could only be used in thin layers since it is almost opaque to its own scintillation light. The scintillations originating from weakly ionizing radiations on ZnS(Ag) could thus not be seen even by a trained human eye.
Cherenkov and Scintillation Imaging Dosimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Rachael L. Hachadorian, Irwin I. Tendler, Brian W. Pogue
Finally, the choice of using Cherenkov or scintillation luminescence to image translates into different applications because the quality of the signal intensity and linearity are different. Cherenkov imaging can provide the signal directly from a patient's tissue, inherently providing a map of the dose directly on the subject, albeit somewhat altered by the tissue optical properties of the patient [3]. Whereas scintillation imaging provides a brighter signal which is known to be highly linear with dose. So, there are strengths and weaknesses associated with both Cherenkov and scintillation imaging, but interestingly, the technology to image these two signals is substantially similar. This is a field that is still emerging, and each tool could turn into either a useful calibration tool or a time-saving clinical verification tool. The range of methods to image and the applications are outlined here.
Small field and radiosurgery dosimetry
Published in Sam Beddar, Luc Beaulieu, Scintillation Dosimetry, 2018
Kamil M. Yenice, David Klein, Dany Theriault
Plastic scintillation detectors (PSDs) emit light with an intensity proportional to the radiation dose being deposited in the plastic base. A rigorous explanation of the physics behind the scintillation process is given in Chapter 1 of this book, and Chapter 4 provides an extensive description of the basic properties of PSDs. PSDs are very capable candidates with respect to small field radiation dosimetry. They are water equivalent, with mass energy-absorption coefficients that closely match water above . They can be manufactured into various shapes to fit the needs of small measurement geometries while maintaining mechanical robustness, and are also readily available in the form of small, diameter fibers. They mechanical robustness, and are also readily available in the form of small, diameter fibers. They are highly sensitive even at small sizes and exhibit fast luminescence with relaxation times in the order of dose rate, temperature, and energy independent and linear with dose (Beddar, Mackie, & Attix, 1992a, b). Scintillation is an immediate effect. As such, PSDs cannot function as integrating dosimeters and must
Prostate-specific membrane antigen-directed imaging and radioguided surgery with single-photon emission computed tomography: state of the art and future outlook
Published in Expert Review of Medical Devices, 2022
Luca Filippi, Barbara Palumbo, Viviana Frantellizzi, Susanna Nuvoli, Giuseppe De Vincentis, Angela Spanu, Orazio Schillaci
As the present paper is focused on gamma-emitting PSMA-targeting tracers, we briefly describe the main characteristics of the two types of handheld devices employed as gamma-probes: the scintillation and the semiconductor-ionization detectors [28]. Scintillation probes are made up of some components: scintillation crystal – most commonly, thallium-activated sodium iodide/NaI(Tl) -, a light guide, a photomultiplier tube (PMT) and associated electronic: incident photon is absorbed by the scintillator crystal, producing visible light that, in its turn, is converted into electric pulse by the PMT. In the semiconductor-ionization detector-based probes, the main components are: semiconductor crystal, a pre-amplifier and its associated electronic; in this type of gamma-probes, incident photons determine ionization in the semiconductor crystal producing free electrons that are collected as electric pulse. It is still an open debate which type of intraoperative probe (scintillation vs semiconductor ones) performs better: while semiconductor probes, in fact, are generally characterized by higher energy and spatial resolution, scintillation detectors present higher sensitivity, especially for high and medium-energy photons [29,30].
Disposition study of the novel dipeptidyl peptidase 4 inhibitor cetagliptin in rats
Published in Xenobiotica, 2022
Jinmiao Lu, Yan Hao, Fuzhi Zhang, Huiping Pan, Juping Ding, Qiang Yu, Tong Wang
Bile from BDC SD rats was pooled according to volume and specified time intervals, vortexed, and 0.025 g of bile was mixed with 10 ml scintillation fluid. Urine from BDC SD rats was pooled according to volume and specified time intervals, vortexed, and 0.1 g of urine was mixed with 5 ml scintillation fluid. Cage washing fluid and cleaner fluid from BDC SD rats were pooled according to volume and specified time intervals, vortexed, and 1 g cage washing fluid and cleaner; fluid was mixed with 5 ml scintillation fluid. Faeces were mixed with isopropanol: water (50:100, v: v), and overnight at 4 °C, then an appropriate amount of isopropanol: water (50:100, v: v) was added. The mixture was weighted, vortexed; 0.1 g–0.3 g of the mixture was burned by the biological oxidiser, the carbon dioxide generated by the sample was captured with 15 ml scintillation fluid. All the process was analysed using scintillation analyser.
What is the current value of fluorescence polarization assays in small molecule screening?
Published in Expert Opinion on Drug Discovery, 2020
Since the first use of plate readers for HTS, FP-based detection methods have played a leading role. FP-based assays can be performed in homogeneous solutions since no physical separation of the bound and free ligands is required, resulting in fewer handling steps. Thus, FP-based assays are faster than the alternative filtration assays, which require physical separation and thus additional handling steps. Furthermore, alternative scintillation proximity assays are expensive to perform [2,p.105]. Several useful properties of the FP phenomenon support the success of FP-based assays in HTS experiments. Namely, ratiometric FP techniques are tolerant to small fluctuations in instrument variance and fluorescence intensity. FP-based assays are also rapid and precise; several instruments have measurement standard deviations of less than 1 mP at a tracer concentration of 1 nM and a reading time of less than 1 min for a 384-well plate. Often, quality factor Z′ values [4] greater than 0.7 have been achieved for FP assays, where assays are considered suitable for HTS at Z′ values of 0.5–1.0. Glickman, in a comparison between two types of FP-based assays (Polar Screen™ and IMAP®) and alternative assays used in HTS [2,p.88], concluded that the major drawback of Polar Screen and IMAP is a susceptibility to compound fluorescence interference.