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CT Essentials Glossary

CT Essentials Glossary

CT Essentials Glossary Glossary term Description Ablation Ablation in the medical context means the removal of biological tissue or cells, usually by surgery or mechanical minimal invasive interventions (e.g. rotablation of atherosclerotic (blocked) blood vessels is the removal of fatty deposits or plaque with a drill-like device). However, surface abla- tion of the skin can be carried out by chemicals or lasers. Ablation therapy of the heart in electrophysiology uses radio frequency waves to cure a variety of cardiac arrhythmia. Absorbed Dose (D) The absorbed dose is the amount of energy deposited in matter after be- ing exposed to a certain amount of radiation measured in gray (Gy) units. One gray is defined as the amount of radiation required to deposit 1 joule (J) of energy in 1 kilogram of any kind of matter. Acute Radiation Syndrome Acute radiation syndrome (ARS), also known as radiation poisoning or (ARS) radiation sickness, is caused by the death of a large number of cells in organs, impairing their function after exposure to radiation. Adaptive 3D Intervention The Adaptive 3D Intervention option has the following key features: • Special intervention scan modes which can be adapted to the user's preferred workflow (in-room or out-of-room) and clinical needs • User can switch between the scan modes and can modify the parameters at any time during the procedure • An additional table-side panel (i-Control) facilitates in-room manipulation of table movement and image display and allows full access to the software control • Flexible screen layouts, also for dual-monitor display (offered as an option), providing a more comprehensive image viewing during the procedure • Screen layouts can be customized with a Layout Editor • 3D intervention functionality that provides MPR and VRT displays of the target volume permitting tracking of the needle in three dimensions • i-Precision View: a switch that permits the mAs to be raised for the next scan (in percent with relation to the intervention dose) to obtain quality diagnostic images for documentation purposes • Needle View displays MPRs oriented according to the needle position for better visualization and tracking during the procedure • i-Needle Sharp (offered as an option) displays images with reduced needle artifacts and provides presets for different needle gauges • Specific interventional toolbars which can be customized to the preferred workflows Adaptive Cardio Sequence A mode in which the CT scanner registers the ECG in real time; it analyzes if the heartbeats are normal and triggers the scan during a predefined phase of the ECG. Adaptive ECG-Pulsing A CT scan mode in which the current intensity is modulated such that the radiation is maximal during the prescribed phase of the ECG and the radia- tion is reduced to a minimum during the rest of the ECG. Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date: 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Job Aid | CT Essentials Glossary Effective Date: 18/OCT/2020 | HOOD05162003134673 Glossary term Description ADMIRE Advanced Modeled Iterative Reconstruction AEF Arterial enhancement fraction ALARA As Low As Reasonably Achievable Alpha particles Alpha (α) particles are fast-moving Helium-4 (4He) nuclei. Angiography Radiographic visualization of the blood vessels after injection of a radio- paque substance (contrast agent). In CT, iodine is frequently used as a contrast agent. Anode The electron-collecting electrode of the X-ray tube. API Automatic Patient Instruction Apoptosis A genetically determined process of cell self-destruction that is marked by the fragmentation of nuclear DNA; it can be activated by radiation. ASA Advanced Smoothing Algorithm. A type of image filter used in image pro- cessing. Attenuation Reduction of the amount of force or the value of a parameter; in this con- text, reduction of the intensity of the radiation beam Attenuation manifests itself in the reduction of the X-rays' detectable in- tensity after passing through a body. Radio-opaque tissue is commonly displayed in white or light gray. AWP Acquisition workplace bi-segment reconstruction Taking data from up to two heart beats for improving temporal resolution. Bone marrow Soft, highly vascular, modified connective tissue that occupies the cavities of most bones and occurs in two forms: (a) a yellowish bone marrow con- sisting chiefly of fat cells and predominating in the cavities of the long bones – this type is called yellow marrow; (b) a reddish bone marrow con- taining little fat, constituting the main site of red blood cell and blood granulocyte formation, and occurring in the normal adult only in cancel- lous tissue especially in certain flat bones – this type is called red marrow. CAD Computer-aided detection CARE Combined Applications to Reduce Exposure CARE Dose Dose-modulated acquisition for adaption of the tube current during the examination; it provides optimum image quality at the lowest radiation dose. CARE Dose4D A system that not only modulates the radiation intensity according to the size of the patient but also to the anatomical region which is being irradi- ated as the CT scan progresses. CARE Combined applications to reduce exposure. CAT Computed Axial Tomography Cathode The electron-emitting electrode of the X-ray tube. CCC Siemens Customer Care Center cCTA Coronary CT angiography CNR Contrast-to-noise ratio Collimator Device (shield) for narrowing a beam of radiation (such as X-rays) with the purpose of aligning it in a specific direction or shaping its spatial cross section. Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Page 2 of 9 Job Aid | CT Essentials Glossary Effective Date: 18/OCT/2020 | HOOD05162003134673 Glossary term Description Convolution Kernel The convolution algorithm “Kernel” affects on image sharpness, noise and resolution, applies a specific mathematical algorithm and digitally filters the raw data during image reconstruction. CT Computed Tomography. The C in CT stands for "Computed" since a computer is required to process the large amount of data generated during the examination. The T stands for Tomograph or Tomography. Tomo refers to the greek word tome for "cut" or "section" and grafein for "to write". CT slice Each image generated by a CT scan along the chosen section plane (trans- verse, coronal, sagittal, or oblique). CTA CT Angiography CTDI Computed Tomography Dose Index or CT Dose Index is the sum of the ab- sorbed dose inside and outside of the slice (the latter due to scattered radiation). CTDIvol CTDIvol is a measure of dose absorbed during a CT examination. It is a local quantity describing the energy deposited in a unit of mass. It describes the average dose in the scan volume for the selected scan parameters. CTDIw is calculated by weighting measured CTDI100 values from different places in dedicated plastic phantoms: one third in the center and two thirds from the periphery. CTDI100 is the integral of the dose profile produced in a single axial scan along a line perpendicular to the scan plane from -50 mm to +50 mm, di- vided by the scan length. CTDIvol is the CTDIw corrected by the Pitch factor for a spiral scan describ- ing the average dose in the scanned volume: CTDIvol = CTDIw/Pitch factor. DAS Data Acquisition System DECT Dual Energy CT Detector Device for detecting the presence of electromagnetic waves or of radioactivity. Deterministic damage This term implies that radiation poisoning definitely occurs and that the damage is dependent on the amount of radiation received. Damage of or- ganic tissue will occur for sure as a consequence of the exposition to a high amount of ionizing radiation. DICOM Digital Imaging and Communication in Medicine Dose-Length Product (DLP) Dose-Length Product or DLP is the product of CTDIvol and the length of the examination range. DSA Digital Subtraction Angiography DSCT Dual Source CT ECG Electrocardiogram Ectopic beat A heartbeat that is spurious and is not synchronized as normal heartbeats. Effective Dose (E) The effective dose reflects the sensitivity of each organ and is a weighted average of the equivalent dose received by the organs. Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Page 3 of 9 Job Aid | CT Essentials Glossary Effective Date: 18/OCT/2020 | HOOD05162003134673 Glossary term Description It is measured in sievert (Sv) units and is the sum of the equivalent doses in all irradiated organs multiplied by the respective tissue weighting factors wr. Effective mAs The effective mAs was defined as the actual mAs value, divided by the pitch factor; effective mAs = mAs / pitch. Electromagnetic radiation Radiation that has the properties of particles and waves (photons) and con- sists of both electric and magnetic fields. Electron An elementary particle carrying a charge of negative electricity and spinning around the atomic nucleus. Equivalent Dose (H) The equivalent dose for any type of radiation is defined as the absorbed dose (D) multiplied by a factor (wr) that weights the radiation-specific dam- age caused to biological tissue. In the case of X-rays used in CT, the weighting factor is 1; therefore, the equivalent dose is the same as the ab- sorbed dose (H=D). The equivalent dose is measured in sievert (Sv) units. It takes into account the damage caused by different types of radiation. Examination range Part of the body to be scanned along the longitudinal axis (z-axis). Examination Task Card An individual scan protocol can be edited and saved in a simple, intuitive way in the Examination Task Card. The typical workflow is as follows: • Registering the patient • Setting up the desired scan ranges with the appropriate scan and reconstruction parameters • Saving the protocol before or after scanning under Edit > Save Scan Protocol The protocol name and the body region folder can be specified in the pop-up dialog box: • If the same protocol name and folder are used, the modifications will override the existing parameters in the protocol • If a new protocol name is used, the previous protocol will be kept Useful hints: • Only numbers from 0 to 9 and characters from A to Z and the underscore sign ( _ ) can be used in the protocol name • Neither an empty space nor country-specific characters are allowed • The modified scan protocols are marked by a dot in front of the protocol in the Patient Model dialog • It is recommended to delete all unused scan protocols • It is possible to restore the Siemens default protocols FAST Fully assisting scanner technologies FBP Filtered Back-Projection FDA Food and Drug Administration Flash Spiral This is a new ECG-triggered technique that is based on a dual source spiral scan at very high pitch. It enables scanning of the heart in only one heart- Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Page 4 of 9 Job Aid | CT Essentials Glossary Effective Date: 18/OCT/2020 | HOOD05162003134673 Glossary term Description beat. Fluorescence Luminescence that is caused by the absorption of radiation at one wave- length followed by nearly immediate emission of light, usually at a different wavelength; this luminescence ceases almost immediately when the inci- dent radiation stops. FoV Field of View Free radicals Atoms, molecules, or ions with unpaired electrons. These unpaired elec- trons are usually highly reactive so that radicals are likely to take part in chemical reactions that eventually change or harm the DNA of the cells. Gamma rays (γ-rays) Radiation consisting of photons with a wavelength of less than 1 pm. Gastrografin Positive radiocontrast agent containing iodine: diatrizoic acid. Used as an alternative to barium-sulfate solution for medical imaging of, e.g., the gas- trointestinal tract or for urologic/endoscopic examinations. HCE High Contrast Enhancement. A type of image filter used in image processing. HD FoV High Definition Field of View HILS Healthcare Integrated Learning Solutions Hounsfield Unit CT numbers are normally expressed in Hounsfield units (HU), named after Sir Godfrey N. Hounsfield. He is the inventor of CT and received the Nobel Prize in 1979. HU Hounsfield units, CT number ICRP International Commission on Radiological Protection iMAR Iterative metal artifact reduction Integrated IR Integrated iterative reconstruction Ionization The process by which atoms are converted into ions (electrically charged atoms). Ionizing radiation Radiation that can ionize matter IR Iterative Reconstruction IRIS Iterative Reconstruction in Image Space Irradiation Radiation emitted with a specific, in this case, medical purpose. IRS Image reconstruction system Iterative Reconstruction In an iterative reconstruction, a correction loop is introduced into the image generation process. Synthesized projection data are compared with real measurement data in an iterative manner. The update image is refreshed by a correction image, and prior knowledge is imposed onto image data. The application of prior knowledge reduces image noise within homogeneous regions, whereas contrast edges are preserved. The corrected image has the potential to enhance spatial resolution and to reduce image noise with- out the loss of spatial resolution as in FBP or even at increased sharpness. iTRIM Iterative temporal resolution improvement method IVR Interleaved volume reconstruction Kernel The Kernel is a reconstruction parameter which affects on image sharpness, noise and resolution, applies a specific mathematical algorithm and digitally filters the raw data during image reconstruction. Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Page 5 of 9 Job Aid | CT Essentials Glossary Effective Date: 18/OCT/2020 | HOOD05162003134673 Glossary term Description keV Kiloelectron volt Kinetic energy Energy stored in a moving object kV Kilo volt; if printed in italics (kV), it stands for tube voltage. LCE Low Contrast Enhancement. A type of image filter used in image processing. LCS Lung cancer screening mA Milli ampere mAs mAs is the product of the X-ray tube current (mA) and the exposure time (s). mAs determines the amount of photons or quanta delivered by the X- ray beam. mGy Milli gray MinDose Retrospective ECG-gated spiral scan with pulsing plateaus and tube current reduction to 4%. MinIP Minimum Intensity Projection MIP Maximum Intensity Projection Modulation Adjustment of a parameter to keep it in the desired range MPR Multiplanar Reformatting MSCT Multislice CT Neutron An uncharged elementary particle that has a mass nearly equal to that of the proton and is present in all known atomic nuclei. Noise In this context, the grainy structure of a CT image. Nomenclature for scan pro- CT systems come complete with a number of default scan protocols, tocols which can be freely customized by the user. For clarity, they are grouped according to body regions, separately for adults and children. There are several types of protocols which can be recognized by the naming structure and suffixes. Protocols without a suffix are standard spiral modes, for example, 'Sinus' means the spiral mode for the sinus. The other protocol types are distinguished by their suffixes: "Seq": sequence studies - "AdaptSeq": Adaptive Cardio Sequence - "Routine": routine studies - "ECG": ECG-gated or -triggered mode - "Vol": 3D Recon workflow - "Neuro": neurological examinations with a special mode - "UHR": Ultra High Resolution modes - "z-UHR": Ultra High Resolution mode with z-Sharp technology - The other protocol types are distinguished by their prefixes: "DS": using Dual Source (only SOMATOM Definition) - "DSXXL": obese studies using Dual Source (only SOMATOM Definition) - "DE": using Dual Energy (only SOMATOM Definition) - "RT": Radio Therapy studies - Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Page 6 of 9 Job Aid | CT Essentials Glossary Effective Date: 18/OCT/2020 | HOOD05162003134673 Glossary term Description PACS Picture Archiving & Communication System PBV Perfused blood volume PET Positron emission tomography PEV Polyp enhanced viewing Photon A quantum of electromagnetic radiation. Pitch The term is applicable only to spiral CT. It is defined as the ratio of table feed per rotation to slice width of one detector row. Plexiglas phantoms Dummies of plexiglass used to measure the radiation doses in different parts of the body. Positron Positively charged particle with the same mass as the electron. Preston's Study Preston D L et al, Solid Cancer Incidence in Atomic Bomb Survivors: 1958–1998, RADIATION RESEARCH 168, 1–64 (2007). The most important study that addresses the risk of stochastic damage of radiation is the one conducted by Preston et al. on 105,000 radiation vic- tims in Hiroshima and Nagasaki. 35,000 having received radiation doses between 5 and 200 mSv. Unfortunately, this study shows a high statistical uncertainty in the low-dose range that applies to CT scanning. PWM Perfusion-weighted map Radiation The process of emitting radiant energy in form of waves or particles. Radioactive substances Substances that emit radiation of different types. Radioactivity The property possessed by some elements (as uranium) or isotopes (as car- bon-14) of spontaneously emitting energetic particles (as electrons or alpha particles) by the disintegration of their atomic nuclei. Radionecrosis Destruction of organic tissue by radiation. Radon Heavy radioactive gaseous element formed by the natural decay of uranium. Resolution A measure of the sharpness of an image or of the fineness with which a device (as a video display, printer, or scanner) can produce or record such an image. Right Dose Management Siemens has established programs to support customers in documenting and reporting the dose applied to patients. Optimize CARE CT, for example, is a consultancy program offered by Siemens Customer Service. You find current information on the Right Dose concept in the intranet sec- tion about CT products. RECIST Response Evaluation Criteria In Solid Tumors ROI Region of interest RRT Rapid Results Technology RTP Radiation Therapy Planning SAFIRE Sinogram Affirmed Iterative Reconstruction SFoV Scan Field of View Sharpness Clearness in the outline or detail of an image, the ability to resolve small details. Sinogram Is based on the sine function: 1. A visual representation of the raw data obtained in a Computed Axial Tomography (CAT) scan. Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Page 7 of 9 Job Aid | CT Essentials Glossary Effective Date: 18/OCT/2020 | HOOD05162003134673 Glossary term Description 2. Sinogram is a synonym for Radon transform data. A Radon transform is the mathematics underlying the process of the CAT scan. SNR Signal-to-noise ratio SPECT Single-photon emission computed tomography Spiral CT A CT scan during which the table and the X-ray tube move continuously and in which the radiation source follows a spiral path relative to the examined body region. SRS Siemens Remote Service SSD Shaded Surface Display Stochastic Damage Damage that might happen in a non-deterministic way. A stochastic process is determined by both predictable actions and a random element and there- fore involves a chance or probability. In this context, “stochastic ” means that the probability of suffering a dis- ease caused by radiation is proportional to the amount of radiation received years before. TAVI Transcatheter aortic valve implantation (EU term) TAVR Transcatheter aortic valve replacement (U.S. term) TBDE TwinBeam Dual Energy to trigger To initiate, actuate, or set off by a certain event or signal. Tomograph The device which produces sectional images, the tomogram. A tomograph or CT scanner displays the three-dimensional spatial distribu- tion of physical values. In our example, this is the density of a tissue. Tomography Tomography is imaging by sectional slices that is based on the interference of waves of energy from an X-ray source with the body. The result of the CT examination is the spatial representation of the distri- bution of, for example, bones, soft tissue, organs, and blood vessels to visu- alize pathological changes. Topogram A scan with a fixed tube position and continuous table movement that re- sults in an overview image. Tube current Current applied to the cathode of the X-ray tube. Tube voltage Voltage (electric potential difference) between the anode and the cathode of the tube. UFC Ultra Fast Ceramic Detector. It is characterized by up to 30% dose reduction in relation to conventional CT detectors and ultra short afterglow. UHR The Ultra High Resolution (collimator) is a comb-shaped collimator which increases the high contrast resolution in phi-direction. Vertebroplasty Vertebroplasty is a medical spinal procedure. The goal of this technique is to relieve the pain of osteoporotic compression fractures. Bone cement is in- jected percutaneously through a small hole in the skin into a fractured ver- tebra. It has been found to be ineffective in treating compression fractures of the spine. VOI Volume of interest VRT Volume Rendering Technique X-CARE Organ-based dose modulation. In this mode, the radiation intensity is re- Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Page 8 of 9 Job Aid | CT Essentials Glossary Effective Date: 18/OCT/2020 | HOOD05162003134673 Glossary term Description duced when the patient is irradiated from the front. X-ray Electromagnetic radiation that has an extremely short wavelength of less than 100 angstroms and has the property of penetrating various thickness- es of all solid materials. XRS X-ray Rotating System, the rotating part of the generator. Please note that the learning material is for training purposes only. For the proper use of the software or hardware, please always use the Operator Manual or Instructions for Use (hereinafter co llec- tively “Operator Manual”) issued by Siemens Healthineers. This material is to be used as training material only and shall by no means substitute the Operator Manual. Any material used in this training will not be updated on a regular basis and does not neces- sarily reflect the latest version of the software and hardware available at the time of the training. The Operator's Manual shall be used as your main reference, in particular for relevant safety information like warnings and cautions. Note: Some functions shown in this material are optional and might not be part of your system. Certain products, product related claims or functionalities (hereinafter collectively “Functionality”) may not (yet) be comme rcially available in your country. Due to regulatory requirements, the future availability of said Functionalities in any specific country is not guaranteed. Please contact your local Siemens Healthineers sales representative for the most current information. The reproduction, transmission or distribution of this training or its contents is not permitted without express written authority. Offenders will be liable for damages. All names and data of patients, parameters and configuration dependent designations are fictional and examples only. All rights, including rights created by patent grant or registration of a utility model or design, are reserved. Copyright © Siemens Healthcare GmbH 2020 Siemens Healthineers Headquarters Siemens Healthcare GmbH Henkestr. 127 91052 Erlangen, Germany Phone: +49 9131 84-0 siemens-healthineers.com Unrestricted | Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2020 SIEMENS Master Template Effective Date 5 Mar 2020 | HOOD05162003074494 Job Aid Effective Date: 18 OCT 2020 | HOOD05162003134673 Healthineers Page 9 of 9