Imaging Characteristics Rad T 285 Review Topics 2 Imaging Characteristics

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Signal-to-Noise Ratio (SNR) A sensor responds to both signal strength and electronic errors from various sensor components (noise) SNR = signal-to-noise ratio signal = the actual energy reaching the detector noise = random error in the measurement (all systematic noise has been removed) To be effective, sensor must have high SNR

DQE

Copyright © 2017, Elsevier Inc. All Rights Reserved. Chapter 15 Computed Radiography Copyright © 2017, Elsevier Inc. All Rights Reserved.

Photostimulable Phosphor Copyright © 2017, Elsevier Inc. All Rights Reserved.

Copyright © 2017, Elsevier Inc. All Rights Reserved. Image Noise Mechanical Defects Slow scan driver Fast scan driver Optical Defects Laser intensity control Scatter of stimulating beam Light quanta emitted by screen Light quanta collected Computer Defects Electronic noise Inadequate sampling Inadequate quantization Copyright © 2017, Elsevier Inc. All Rights Reserved.

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Copyright © 2017, Elsevier Inc. All Rights Reserved. Chapter 16 Digital Radiography Copyright © 2017, Elsevier Inc. All Rights Reserved.

Copyright © 2017, Elsevier Inc. All Rights Reserved. Digital Radiography CR: photostimulable phosphor SPR: photodiode Indirect DR: thin-film transistor Indirect DR: charge coupled device Direct DR: thin-film transmitter Copyright © 2017, Elsevier Inc. All Rights Reserved.

Digital Radiography Imaging System Capture Element Coupling Element Collection Element Copyright © 2017, Elsevier Inc. All Rights Reserved.

CsI Charge-Coupled Device (CCD) Copyright © 2017, Elsevier Inc. All Rights Reserved.

Copyright © 2017, Elsevier Inc. All Rights Reserved. Capture Element CR Photostimulable phosphor DR Cesium iodide (CsI) Gadolinium oxysulfide (GdOS) Amorphous selenium (a-Se) Copyright © 2017, Elsevier Inc. All Rights Reserved.

Copyright © 2017, Elsevier Inc. All Rights Reserved. Coupling Element Lens Fiber optic assembly Contact layer a-Se Copyright © 2017, Elsevier Inc. All Rights Reserved.

Copyright © 2017, Elsevier Inc. All Rights Reserved. Collection Element Photodiode: light-sensitive device CCD: light-sensitive device Thin-film transistor (TFT): charge-sensitive device—collects electrons Copyright © 2017, Elsevier Inc. All Rights Reserved.

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Chapter 17 Digital Radiographic Technique Copyright © 2017, Elsevier Inc. All Rights Reserved.

Line Pairs and Spatial Frequency Copyright © 2017, Elsevier Inc. All Rights Reserved.

Spatial Resolution of Imaging Systems Gamma camera 0.1 lp/mm Magnetic resonance imaging 1.5 lp/mm Computed tomography Diagnostic ultrasound 2.0 lp/mm Fluoroscopy 3.0 lp/mm Digital radiography Radiography 8.0 lp/mm Mammography 12.0 lp/mm Copyright © 2017, Elsevier Inc. All Rights Reserved.

Copyright © 2017, Elsevier Inc. All Rights Reserved. Dynamic Range Screen-Film Imaging OD zero to 3.0 Three orders of magnitude Dynamic range = 1000 Digital Imaging Bit capacity of each pixel Four to five orders of magnitude Dynamic range > 65,000 Copyright © 2017, Elsevier Inc. All Rights Reserved.

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MTF Elsevier items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc.

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Contrast Detail(Resolution) Elsevier items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc.

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The patient makes the beam better suited for absorption by the receptor Elsevier items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc.