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Gastrointestinal tract and salivary glands
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The patient is positioned in the gamma camera ready to commence imaging during the meal. A dual-headed gamma camera allows anterior and posterior images to be collected simultaneously and a geometric mean can then be determined. The patient is instructed to consume the meal as quickly as is comfortable. Image acquisition is initiated as the patient consumes the meal and the dynamic imaging protocol is divided into two phases: A first phase of 30 frames in rapid succession, with each frame acquired over a 10 second period.A second phase of 1 minute frames for a period up to 90 minutes, terminated at any time if emptying is observed to be complete.
Light Sheet or Selective Plane Microscopy
Published in John Girkin, A Practical Guide to Optical Microscopy, 2019
As a microscopy technique, light sheet methods as currently operated, are new and the technical developments in the field are currently very rapid. The main advantages of the method are, however, clear. If one requires three-dimensional images of an intact, living, basically transparent sample, SPIM is probably the first method to consider. If one then adds to this the desire to image at higher speed in three dimensions then it is without doubt the route to explore. In all light microscopy methods the sample has to be illuminated and while for fixed, dead samples the light is not normally harmful (though you may have a little photo-bleaching), for anything that is living this has to be a consideration. Light sheet microscopy delivers the lowest light dose to the sample of any three-dimensional imaging method making it an excellent choice for extending imaging of samples. In taking a single optical section in one image it is also the fastest method and thus ideally suited for dynamic imaging. The resolution of the image can be diffraction limited in the main plane, however. In the optical axis the thickness of the slice is larger than one would achieve using a well-adjusted confocal microscope with a high numerical aperture objective. There are complex ways around this limitation but they are not simple to implement.
Biomedical Imaging Molecular Imaging
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
Christian J. Konopka, Emily L. Konopka, Lawrence W. Dobrucki
Closely tied to the sensitivity of a system is its temporal resolution. Temporal resolution refers to the ability of a system to quickly acquire an acceptable image. This is an important quality when considering applications for MI, because researchers are finding that tracer dynamics, or how the tracer distribution changes over time, can be more important than looking at the distribution of a tracer at a certain time. To perform dynamic imaging, quick image acquisition is necessary to produce multiple frames in as little amount of time as possible. To do this, an adequate number of counts to reconstruct images of sufficient signal-to-noise ratio need to be acquired. PET imaging has the advantage in this arena due to its increased sensitivity and full ring of detectors, and dynamic PET imaging is capable in most systems. SPECT has the limitations of decreased sensitivity compared to PET, and the necessity to complete a rotation around a subject to produce an image. Because of these limitations, SPECT is not traditionally used for dynamic studies. Researchers have developed specialized SPECT systems however which can perform dynamic imaging, largely by modifying the detector gantry so that it is a fixed gantry with no need to rotate around the patient as in conventional SPECT imaging, or a ring of SPECT detectors as in PET. There are also dedicated cardiac SPECT imagers which rotate just enough to gain sufficient angular sampling, allowing for kinetic modeling of cardiac function (Ben-Haim et al. 2013, Farncombe et al. 1999, Furenlid et al. 2004).
Identifying and addressing the limitations of EVAR technology
Published in Expert Review of Medical Devices, 2018
Viony M Belvroy, Ignas B Houben, Santi Trimarchi, Himanshu J Patel, Frans L Moll, Joost A. Van Herwaarden
Magnetic Resonance Imaging (MRI, Figure 1F) does not involve ionizing radiation and MR Angiography (MRA) uses less nephrotoxic contrast agents than CTA, making it the preferred imaging modality for patients with severe renal dysfunction (glomerular filtration rate < 30)[22]. Nevertheless, CTA remains the gold standard and MRA is exceptionally used in pregnant, very young or chronic kidney disease patients. The commonly used intraoperative techniques are fluoroscopy and angiography, providing2D plain radiographic images after intravascular admission of contrast agent. The disadvantage of angiography is the use of a nephrotoxic contrast agent and the exposal to radiation damage. A new development is CTA with fluoroscopy fusion technology. This technique uses a 3D CTA image from a cone beam CT, a preoperative CTA or a preoperative MRA and combines this with another dynamic imaging modality, usually fluoroscopy. This produces an overlay, giving a real-time 3D road-map for catheterization and guide wire movements. It limits both operation time and the nephrotoxic ionized contrast dose [23]*.