Glossary of Medical Imaging Technologies

This glossary is excerpted with permission from Radiologyinfo.org, sponsored by the American College of Radiology and the Radiological Society of North America. Visit www.Radiologyinfo.org for a broader glossary of radiology terms.

angiocardiography
(an-jE-O-kar-dE-O-gra-fE)

X-ray imaging of the heart and great vessels made visible by injection of a radiopaque solution.

angiography
(an-jE-og-ra-fE)

Radiography of vessels after the injection of a radiopaque contrast material. Unlike angioplasty, which is an invasive procedure, angiography breaks the skin only for the insertion of a needle for administering a radiopaque catheter and positioning under fluoroscopic control. This technique is used to image arteries in the brain, heart, kidneys, gastrointestinal tract, aorta, neck, chest, limbs and pulmonary circuit.

angioplasty
(an-jE-O-plas-tE)

Reconstitution or reopening of a blood vessel; may involve balloon dilation, mechanical stripping of the inside of the blood vessel, forceful injection of an elastic filamentous protein, or placement of a stent.

barium (Ba)
(ba-rE-um, bA-rE-um)

A metallic, alkaline, divalent earth element; atomic no. 56, atomic wt. 137.327. Salts are often used in diagnosis.

brachytherapy
(bray-key-therapy)

Radiotherapy in which the source of irradiation is placed close to the surface of the body or within a body cavity; e.g., application of radium to the cervix.

catheter angiography

An examination of blood vessels by injecting contrast material directly into an artery through a small plastic tube.

For details see the Catheter Angiography page.

colonoscopy
(kO-lon-os-ko-pE)

Visual examination of the inner surface of the colon by means of an instrument for the examination of the interior of the colon – the division of the large intestine extending from the first part of the large intestine to the rectum.

computed radiography

Computed radiography (CR) systems capture X-ray images onto storage phosphor-based image plates, inside a removable cassette. The plate is exposed in the same manner as film. These image plates are placed in a reader, scanned, and processed to create the final digital radiographic image. Computed radiography (CR) systems can serve facilities of all sizes, including physician offices and imaging centers, as well as hospital radiology departments, ICUs and specialty care areas. CR systems offer sophisticated image processing, excellent image quality and productivity.

computed tomography (CT)
(tO-mog-ru-fE)

Sometimes referred to as CAT scan (computerized axial tomography).

Imaging anatomical information from a cross-sectional plane of the body, each image generated by a computer synthesis of X-ray transmission data obtained in many different directions in a given plane.

Developed in 1967 by British electronics engineer Godfrey Hounsfield, CT has revolutionized diagnostic medicine. Hounsfield linked X-ray sensors to a computer and worked out a mathematical technique called algebraic reconstruction for assembling images from transmission data. In 1973, the Mayo Clinic began operating the first machine in the U.S. Early machines yielded digital images with at least 100 times the clarity of normal X-rays. Subsequently, the speed and accuracy of machines has improved many times over. CT scans reveal both bone and soft tissues, including organs, muscles, and tumors. Image tones can be adjusted to highlight tissues of similar density, and, through graphics software, the data from multiple cross-sections can be assembled into 3-D images. CT aids diagnosis and surgery or other treatment, including radiation therapy, in which effective dosage is highly dependent on the precise density, size, and location of a tumor.

computed tomography (CT) angiography
( tO-mog-ru-fE an-jE-O-gra-fE)

A method of examining blood vessels utilizing X-rays and injection of iodine-containing contrast medium.

For details see the CT Angiography page.

computer-aided detection

Computer-aided detection (CAD) software uses sophisticated algorithms to highlight suspicious areas on patients' digitized images, signaling radiologists to closely examine these areas for possible disease. CAD technology pinpoints suspicious areas on medical images by analyzing the shape, groupings and other characteristics of abnormalities and determining their correlation to previously analyzed disease characteristics.

densitometry

A method for imaging density.

diagnostic ultrasound

The use of ultrasound to obtain images for medical diagnostic purposes, typically employing frequencies ranging from 2 MHz to about 12 MHz.

digital radiography

Digital radiography (DR) systems capture X-ray images directly onto a detector, using amorphous selenium as a photoconductor layered on thin film transistors that directly convert X-ray photons into an electrical signal. These images are immediately ready for display and storage. Digital radiography systems provide highly efficient, high-quality direct digital image capture for most radiographic exams conducted by hospitals and imaging clinics.

Doppler ultrasonography

An application of diagnostic ultrasound used to detect moving blood cells or other moving structures and measure their direction and speed of movement. The Doppler effect is used to evaluate movement by measuring changes in frequency of the echoes reflected from moving structures.

In many instances, Doppler ultrasound has replaced X-ray methods such as angiography, as a method to evaluate blood vessels and blood flow. Doppler ultrasound permits real-time viewing of blood flow that cannot be obtained by other methods. Doppler ultrasound has proved a boon in all areas of ultrasound, aiding in the evaluation of the major arteries and veins of the body, the heart, and in obstetrics for fetal monitoring.

electrocardiogram (ECG)

A record of the electrical activity of the heart. An abnormal pattern may indicate a disturbance of the heart's rhythm, not enough blood getting to part of the heart wall, or an actual heart attack.

embolization

The movement of a blood clot, piece of tissue, or pocket of air or gas from where it forms through the bloodstream until it lodges in place, cutting off the flow of blood with its oxygen and tissue nutrients. Catheter embolization is the deliberate introduction of foreign ("embolic") material such as gelatin sponge or metal coils to stop bleeding or cut off blood flowing to a tumor or arteriovenous malformation.

external beam therapy

External beam therapy is used to aim highly focused beams of radiation at the edges of the site where cancer is found in order to destroy any abnormal cells and prevent the growth or regrowth of the tumor.

hospital information system and radiology information system (HIS/RIS)

A hospital information system (HIS) is a system that serves as the overall information network for a healthcare facility, and often times a radiology information system (RIS) will feed into and, in effect, become part of the HIS. (See definition of RIS.)

interventional radiology

The clinical subspecialty that uses fluoroscopy, CT, and ultrasound to guide percutaneous (through the skin) procedures such as performing biopsies, draining fluids, inserting catheters, or dilating or stenting narrowed ducts or vessels.

intravenous pyelography (IVP)

Radiography of kidneys, ureters, and bladder following injection of contrast medium into a peripheral vein.

laser

A device emitting intense, focused light energy that can destroy tissues as an alternative to conventional surgical removal.

magnetic resonance cholangiopancreatography
(kO-lan-gE-O-pan-KrE-a-tog-ra-fE)

Magnetic Resonance Cholangiopancreatography (MRCP) is an examination of the bile ducts and pancreas using magnetic resonance imaging.

magnetic resonance imaging (MRI)

A diagnostic radiological modality, using nuclear magnetic resonance technology, in which the magnetic nuclei (especially protons) of a patient are aligned in a strong, uniform magnetic field, absorb energy from tuned radiofrequency pulses, and emit radiofrequency signals as their excitation decays. These signals, which vary in intensity according to nuclear abundance and molecular chemical environment, are converted into sets of tomographic (selected planes) images by using field gradients in the magnetic field, which permits 3-dimensional localization of the point sources of the signals.

magnetic resonance MR angiography
(an-jE-O-gra-fE)

A method of angiography utilizing the magnetic properties of tissues and body fluids rather than X-rays to record images.

For details see the MR Angiography page.

mammography
(ma-mog-ru-fE)

Imaging examination of the breast by means of X-rays, used for screening and diagnosis of breast disease. Ultrasound and magnetic resonance may also be used to image the breast.

For details see the Mammography page.

myocardial perfusion scan

The most common Cardiac Nuclear Medicine procedure, which results in imaging of blood-flow patterns to the heart muscles.

nuclear medicine

The clinical discipline concerned with the diagnostic and therapeutic uses of radionuclides (an isotope of artificial or natural origin that exhibits radioactivity), excluding the therapeutic use of sealed radiation sources.

Certain imaging procedures, including PET scanning, employ radionuclides to provide real-time visuals of biochemical processes. One device, a nuclear imaging machine, employs a scintillation camera, which can rotate around the body to pick up radiation emitted by an injected substance (e.g., radioactive iodine, which localizes in the thyroid, or radioactive thallium, which localizes in the heart). Through computerization, a digitized image of a particular organ is produced.

PACS/RIS

Medical facilities almost always integrate radiology information systems (RIS) - which serve as the information management backbone for a radiology department – with picture archiving and communications systems (PACS). This combination of image-centric PACS and information-centric RIS enables hospitals and imaging centers to simultaneously manage and archive medical images (such as digital X-ray images, MRI images and CT images) and information (such as radiology reports on patients), thus boosting productivity and, ultimately, patient care.

picture archiving and communications systems (PACS)

Picture archiving and communications systems (PACS) enable hospitals, imaging centers and multi-site healthcare organizations to manage and archive patient medical images such as digital X-ray images, MRI images and CT images. Access to these images is fast and easy, since the system features a central database that provides management of information archived in storage components throughout a healthcare system.

positron emission tomography (PET)

Positron emission tomography, also called PET or a PET scan, is a diagnostic examination that involves the development of biologic images based on the detection of subatomic particles. These particles are emitted from a radioactive substance given to the patient. The subsequent views of the human body are used to evaluate function.

For details see the Positron Emission Tomography page.

radiation
(rA-dE-A-shun)

1. The act or condition of diverging in all directions from a center.
2. The sending forth of light, short radio waves, ultraviolet or X-rays, or any other rays for treatment or diagnosis or for other purpose.
3. Radiant energy from waves or subatomic particles.

radiation oncology

The medical specialty of radiation therapy; the study of radiation treatment of abnormal tissue growths (malignant or nonmalignant).

radiation therapy

Treatment for non-malignant conditions and/or cancer through the use of X-rays or radionuclides.

radiofrequency ablation

A treatment technique that uses high-frequency alternating electrical current to destroy tissue cells by heating them.

radiographic
(rA-dE-a-graf-ic)

Referring to the examination of any part of the body for diagnostic purposes by means of X-rays or other diagnostic modalities.

radiography
(rA-dE-a-graf-E)

Examination of any part of the body for diagnostic purposes by means of X-rays with the record of the findings usually impressed upon a photographic film.

therapeutic radiology

A medical specialty and the study of radiation treatment of abnormal tissue (nonmalignant or cancerous) through the use of X-rays or radionuclides.

ultrasonography
(ul-tra-so-nog-ru-fE)

The location, measurement, or delineation of deep structures by measuring the reflection or transmission of high frequency or ultrasonic waves. Computer calculation of the distance to the sound-reflecting or absorbing surface plus the known orientation of the sound beam gives a two- or three-dimensional image.

ultrasound, diagnostic
(ul-tra-sownd)

Ultrasound (US) imaging, also known as ultrasound scanning or sonography, is a method of obtaining images from inside the human body through the use of high frequency sound waves. The sound waves' echoes are recorded and displayed as a real-time, visual image. No ionizing radiation is involved in ultrasound imaging.

urography
(yU-rog-ru-fE)

Radiography of any part (kidneys, ureters, or bladder) of the urinary tract.

venography
(vE-nog-ra-fE)

A type of X-ray in which contrast material is injected into a vein to show the details of its structure and any abnormality that may be present.

X-ray
(X-Ra)

1. The ionizing electromagnetic radiation emitted from a highly evacuated tube, resulting from the excitation of the inner orbital electrons by the bombardment of the target anode with a stream of electrons from a heated cathode.
2. Ionizing electromagnetic radiation produced by the excitation of the inner orbital electrons of an atom by other processes, such as nuclear delay and its sequelae.
3. A radiograph.

X-ray therapy

A medical specialty and the study of radiation treatment of abnormal tissue (nonmalignant or cancerous) through the use of X-rays or radionuclides.