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Equipment for Patient Data Acquisition
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
The scintillating material must have a high sensitivity to 511 keV photons (in practice, a high density and high effective atomic number), a short scintillation decay time, a high light output for a given energy deposition, and a narrow energy resolution at 511 keV. Depending on the manufacturer, there are several options for the choice of the material: bismuth germanate (BGO), lutetium oxyorthosilicate (LSO), gadolinium oxyorthosilicate (GSO), etc. The choice is a matter of compromise between their various characteristics. The thickness of the crystal must be large enough to absorb most photons. It is of the order of 20 mm to 30 mm.
Positron Emission Tomography Imaging Systems And Applications
Published in Bhagwat D. Ahluwalia, Tomographic Methods in Nuclear Medicine: Physical Principles, Instruments, and Clinical Applications, 2020
There are advantages and disadvantages of TOF positron emission tomography (TOFPET) as compared with the conventional non-TOFPET.34 In non-TOFPET, the bismuth germanate (BGO) detector has high efficiency and high spatial and temporal resolution; it has low signal-to-noise ratio, however, relative to the TOFPET. The TOFPET can handle high count rate detection and the accidental rates are reduced relative to the non-TOFPET. The efficiency of the detectors in TOFPET is small due to the available sizes. The spatial resolution of the TOFPET systems is limited and can be improved with smaller and efficient crystal-phototube detectors.
In Vivo Treatment Verification *
Published in Harald Paganetti, Proton Therapy Physics, 2018
The 511 keV photon pairs are energetic enough to penetrate the tissue surrounding the place of annihilation and eventually escape from the patient. Therefore, the PET signal can be acquired by opposite detector pairs surrounding the patient and operated in coincidence (Figure 21.5). Due to the relatively high photon energy, dense high-Z inorganic scintillators are usually employed for stopping the penetrating photon radiation and, at the same time, for enabling fast timing performances of coincident detection typically within a few nanoseconds time window. Commonly used PET detectors are based on bismuth germanate (BGO), gadolinium orthosilicate (GSO), or lutetium oxyorthosilicate (LSO) scintillator crystals coupled to photomultipliers, though more recent solutions combine latest generation scintillators such as lutetium fine silicate (LFS) with state-of-the-art silicon photomultipliers [12].
Markov chain Monte Carlo sampling for accurate estimation of spatial distribution of naturally occurring radionuclides radiation (232Th, 40K, and 238U) in Senegal
Published in Egyptian Journal of Basic and Applied Sciences, 2020
Djicknack Dione, Modou Mbaye, Cheikh Amadou Bamba Dath, Ababacar Sadikhe Ndao, Ndeye Arame Boye Faye
A high resolution, 1024 channels portative gamma spectrometer with a large (103 cm3) high-density Bismuth Germanate crystal detector with an energy range from 30 KeV to 3000 KeV was used for field measurement. The sampling Measurement time was set around 5 minutes for each individual point in a pseudo-randomly sampling procedure. A Bluetooth GPS device paired with the spectrometer was used to record the geographical position. The gamma-ray spectra recorded for each point were further analyzed and taking into account transition of interest from well-defined photo peak from natural radioisotopes of 40K, 232Th and 238U. Determination of the primordial potassium 40K in soil was through the detection of 1460 KeV of associated with the gamma-ray decay of 40K. Based on the assumption of secular equilibrium of naturally occurring radioisotopes of 232Th and 238U primordial series; the thorium radioisotope was estimated through the detection of 2615 KeV gamma-ray energy of 208TI; similarly, 238U was estimated through detection of 1765 KeV gamma-ray energy of 214Bi. An assumption of equilibrium of primordial radionuclides is common in rocks and the 232Th series may be considered in equilibrium in most geological environments [15]. The activity concentration of radioisotopes was converted into specific concentration according to the following relation given by IAEA-2003. Figure 1 shows the geographic location of the study area. The study area is characterized by cumulative rain between 1100 and 1500 mm in the time between 2015 and 2016. Local temperature varies substantially between 19°C and 45°C. In this site of Saraya, measurement of six fields were carried out.