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Computed Tomography Imaging in Radiotherapy
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
CT imaging is based on the measurement of photon attenuation profiles during the rotation of an x-ray tube located in the CT gantry. The x-ray tube operates at voltages between 80 kV and 140 kV and with high currents (up to 500 mA to 800 mA). At the output of the tube, a physical filtering system provides beam attenuation compensation (head/body) and beam hardening. A collimating slit is used to block the x-ray beam in the longitudinal direction so as to define a slice of a specified thickness. After traversing the patient, this fan-beam is intercepted by a series of 700 to 1000 detector elements in an arc-shaped row in the transverse plane of the patient. A focused anti-scatter grid is used to improve the image quality by eliminating most of the scattered radiation.
X-ray Interactions in Matter
Published in Ken Holmes, Marcus Elkington, Phil Harris, Clark's Essential Physics in Imaging for Radiographers, 2021
However, what must be remembered is that although there will be an overall reduction in the amount of scatter at higher beam energies, it is also the case that more of that scatter will be travelling at a reduced scattering angle (i.e. in a forward direction, towards the image receptor); therefore, the anti-scatter grid is more likely to be needed at these higher energies.
Breast imaging
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
A mammography system comprises: A high-voltage/medium frequency generator.X-ray tube.Tube filtration.Compression device.Anti-scatter grid.Image-receptor system.Automatic exposure control (AEC) device.Magnification facility.
Dual-energy material decomposition for cone-beam computed tomography in image-guided radiotherapy
Published in Acta Oncologica, 2019
Mikkel Skaarup, Jens M. Edmund, Sabrina Dorn, Marc Kachelriess, Ivan R. Vogelius
Previous methods to improve the image quality of CBCT scans have included an anti-scatter grid [6], iterative reconstructions [7] and noise suppression and scatter reduction algorithms [8,9]. The dual energy (DE) technique for diagnostic CTs have shown several benefits, including metal artifact reduction and better visualization of different tissues [10–14]. 2D DE radiographs have been investigated in RT treatment, e.g. with the goal of increasing soft tissue contrast [15] or to give better accuracy for marker-less motion tracking with bone suppression [16]. The DE technique has also been tested for CBCT images using phantom scans in a non-clinical setting [17].