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Quality Assurance of Nuclear Medicine Systems
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Poor scatter rejection. A gamma camera imaging system uses energy windowing to preferentially select un-scattered photopeak photons for the imaging radionuclide being used. If this energy window is incorrectly set – either globally or on independent detector components, or if individual detectors have poor energy resolution – there is a risk that images will have an inferior image quality, or that the detector will have a spatially invariant response. The energy response of the system as a whole should therefore be tested as part of a routine quality control programme.
Special Considerations in Pediatric Nuclear Medicine
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Sofie Lindskov Hansen, Søren Holm, Liselotte Højgaard, Lise Borgwardt
When planar imaging is performed, the distribution of the relevant radiopharmaceutical is imaged by one or two gamma cameras at a fixed angular position. The patient is placed above and/or under the gamma camera, and if an area larger than the field of view of the camera is required, then the patient is moved on the scanner bed along the camera or vice versa. A two-dimensional projection of the distribution of the tracer is imaged. If information about the rate of change of the distribution is needed for the diagnostic evaluation, this may be obtained in a dynamic acquisition at one fixed camera position.
Evaluation of the Potential of Microspherical Systems for Regional Therapy in the Tumor-Bearing Liver and Kidney Using Techniques in Nuclear Medicine
Published in Neville Willmott, John Daly, Microspheres and Regional Cancer Therapy, 2020
Jacqueline A. Goldberg, James H. McKillop, Colin S. McArdle
99mTc is widely used in nuclear medicine.1,6 It has many advantages, including availability from a generator when required, gamma ray photons with a near-ideal energy for gamma camera detection, chemical properties that allow combination to many different substances (thus enabling it to be used for radiopharmaceuticals targeted on many different organs), and a relatively short half-life, which reduces radiation dose to the patient. 99mTc-labeled microspheres are ideal for studying the distribution of blood flow by gamma camera imaging. Because of their relatively short half-life they are not suitable for evaluating the long-term (i.e., more than 12 to 24 h) stability of microspheres in vivo.
Progress in large field-of-view interventional planar scintigraphy and SPECT imaging
Published in Expert Review of Medical Devices, 2022
Martijn M.A. Dietze, Hugo W.A.M de Jong
The first imaging mode concerns planar scintigraphy. This imaging mode is the same as is most often performed with handheld gamma cameras. Compared with handheld devices, large field-of-view gamma cameras would enable imaging of relatively larger organs and activity accumulations that are not close to the patient’s skin. The advantage of planar scintigraphy over SPECT is that immediate or even real-time feedback on the activity distribution is obtained. This allows for the imaging of dynamic events (e.g. the injection of activity in the body). However, the downside of this imaging mode is that image interpretation can be challenging. For example, gamma photons originating from overlapping tissues will be detected at the same location, gamma photons may be differently attenuated in different parts of the body (e.g. when passing lung tissue), collimator resolution will make the image blurrier, and substantial noise will be present at low count rates. These image-deteriorating effects will be more severe for activity accumulations that are relatively far away from the patient’s skin because the gamma photons traverse more attenuating material and because the source to collimator distance is larger. These effects make large field-of-view planar scintigraphy primarily interesting for cases in which either the image volume is large (e.g. the liver) or the activity is located in a dense hotspot (e.g. in biopsies).
mRNA and small RNA gene expression changes in peripheral blood to detect internal Ra-223 exposure
Published in International Journal of Radiation Biology, 2022
Patrick Ostheim, Matthias Miederer, Mathias Schreckenberger, Tim Nestler, Manuela A. Hoffmann, Michael Lassmann, Uta Eberlein, Vahe Barsegian, Alexis Rump, Mattháus Majewski, Matthias Port, Michael Abend
For detection of incorporated alpha-emitting radionuclides, excretion analysis has been the established method for decades (Karlsruhe 1979; Taylor and Carolina 2000; Jefferson et al. 2009). Because internal dose cannot be measured directly, it has to be modeled and calculated indirectly under several assumptions. Knowledge of the dynamic behavior (biokinetics) of the incorporated material in the human body is essential for radiation dose estimation of individual organs. This is laborious and time consuming. Although gamma emissions comprise only about 1% of the total emitted energy in Ra-223, there are reports that quantitative imaging may be feasible for dosimetry in case of primarily alpha-emitting radionuclides (Hindorf et al. 2012). However, the need for gamma cameras and imaging time renders this approach infeasible for screening large numbers of people.
Pulmonary translocation of ultrafine carbon particles in COPD and IPF patients
Published in Inhalation Toxicology, 2022
Mikaela Qvarfordt, Martin Anderson, Alejandro Sanchez-Crespo, Maria Diakopoulou, Magnus Svartengren
Tables 3 and 4 clearly shows an imbalance between the total activity cleared from the lungs and the cumulative activity found in blood and excreted through the urinary system. This suggests that UFC particles cleared from the lungs may accumulate in other organs of the body, typically in liver and spleen (Miller et al. 2017). However, none of the subjects in this work concentrated detectable amounts of activity in those organs, suggesting a wider tissue distribution. The low amount of inhaled activity in conjunction to the limited sensitivity of the gamma camera and background radiation, limits the possibility to trace these particles in the body outside the lung region. An approximative value for the minimum detectable activity (MDA) in the liver region can be derived using the Currie formulation (Currie 1968). The minimum mean number of counts needed to ensure a false-negative rate of 5% is; Nbkg is the background count density over the liver region. Assuming photon attenuation in liver with a 5 cm mean photon attenuation pathlength and an effective attenuation coefficient of 0.135 cm−1 for In111, the attenuation corrected minimum mean number of counts is then;