Scan Glossary

Medical scanning uses specialised and advanced technology and using technical terms in describing what we do is sometimes unavoidable. To help, here is a glossary of some of the common technical terms you’ll come across.


Cells that are alive and functioning.

Tissue that is alive and functioning. In PET scanning, the radiopharmaceutical FDG builds up in areas that are very active, such as cancer cells.

The body’s structure, parts and organs

An examination of arteries and veins using a contrast medium to differentiate them from surrounding organs. The contrast medium is introduced through a catheter to show the blood vessels and the structures they supply, including organs.


A barium enema is a procedure (done through X-ray) for examining the large intestine in which the compound barium sulphate is used.

A medical procedure that involves obtaining a tissue sample for analysis to establish a precise diagnosis.

A bone scan is done to look for abnormalities in the bones. It’s usually done in the Nuclear Medicine Department of the hospital. A bone scan can be done to look at a particular joint or bone. In cancer diagnosis, it’s more usual to scan the whole body. The scan involves having to have one injection, but apart from that, it’s painless.

This is when healthy women are examined to see if breast cancer can be picked up early – usually before there are any symptoms.


See Computed Tomography.

The clinical study and practice of treating the heart.

The smallest unit of living matter, capable of functioning. The human body contains billions of cells all with their own different job.

Pictures of the inside of the chest, mainly of the lungs, taken using high energy rays. Please refer to the Patient Information section on X-ray for further information.

CT stands for Computed Tomography, an imaging technique used to visualise both the soft tissue and bone inside your body. CT uses special x-rays to obtain image data from different angles around the body. A powerful computer is then used to process the information to show a cross-section of body tissues and organs – much like viewing the slices of a loaf of bread. CT imaging can show bones, as well as surrounding tissues such as muscle and blood vessels with great clarity. Using this technique, Radiologists can more easily diagnose problems such as cancer, cardiovascular disease, infectious disease, trauma and musculoskeletal disorders. Please refer to our CT information page for further information.

A senior doctor who takes full responsibility for the clinical care of patients. Most Consultants head a team of junior doctors.

Substance given to the patient, either through a drink or injection, to help areas of the body show up more clearly during a scan.

In imaging, a cross-section allows doctors to see slices of the human body – much like viewing the slices of a loaf of bread.

Intended to overcome disease and promote recovery.


Finding out what is wrong, usually about an illness.


See Electrocardiogram.

Medical test of the heart. Small pads are stuck onto the chest around the heart. Wires are attached to the pads and these connect to a machine that takes an electrical recording of the heart beat. Doctors can examine the trace of the heart beat to see if the heart is working normally.


See Fluoro-Deoxy-Glucose.

This means that a test has shown that a disease is not present when in fact it is.

This means a test has shown that a disease is present when it is not.

Also commonly referred to as FDG; compound used widely in PET imaging and which behaves in a similar (analogous) way to Glucose and therefore reflects metabolism in the body. Cancer cells have an increased metabolism and therefore show increased uptake of FDG, reflected in PET images.


A special type of camera that is used in nuclear medicine to produce pictures of the inside of the body after an injection of a special pharmaceutical that gives off radiation. The radiation is detected by the camera allowing the doctor to see diseases that may be present.

PET scanning performed on modified Nuclear Medicine imaging equipment (known as gamma cameras, or SPECT scanners). The performance for PET imaging is compromised and therefore this technique has limited use and acceptance.

A short wavelength, electromagnetic radiation with a range of wavelengths from 10-9 to 10-12 cm. In PET imaging, two gamma rays are emitted when an electron collides with a positron and annihilation occurs.

The portion of the scanner that the patient bed moves through during a scan.

A simple sugar, present in human tissue.


The time taken for a radiopharmaceutical to lose half of its active radioactivity.


Method for displaying two images of the same patient from different scanners simultaneously, for example PET and CT images. This gives doctors more information allowing them to more accurately locate where disease may be.

Tests that produce pictures of areas inside the body.

A specialised area of radiology that uses various imaging techniques to guide the insertion of small instruments and tools through the body to identify and treat a medical disorder without requiring conventional surgery.

One of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced to explain aspects of radioactivity. A radioactive isotope or radioisotope is a natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached.


See Magnetic Resonance Imaging.

An object, as a piece of iron or steel that possesses the property of attracting certain substances. The magnet used in MRI aligns the patient’s hydrogen atoms so they are pointing in the same direction. Pulses of very specific radio wave frequencies are then used to vibrate these hydrogen atoms back and forth between their resting (magnetised) state and their agitated (radio pulse) state. The MRI equipment records the duration, strength, and source location of the signals emitted by the atoms as they relax and translates the data into an image on a PC screen.

An imaging technique used to visualise the soft tissue inside your body. MRI combines a powerful magnet with radio-frequency pulses. These collect signals that are then processed by a sophisticated computer to form pictures of the inside of your body. MRI gives highly detailed pictures of the soft tissues within the body, for example muscles and ligaments. This capability means Doctors can use MRI in a wide range of investigations: from slipped discs and brain tumours, to painful or injured joints, to the assessment of blood flow. Please refer to our MRI information page for further details.

An x-ray examination of the breast to look for early signs of cancer.

An examination method using x-rays to detect cancer in the breast.

Use of electromagnetic radiation to produce images of internal body structures for diagnosis.

Any basic process of organic functioning or operating. Exercise, food, and environmental temperature all influence a human’s metabolism.


Study and treatment of nerve systems.

Small lumps, swellings or collection of tissue

Medical speciality using radioactive elements or isotopes for diagnosis and treatment of disease. A radioisotope is introduced into the body (usually by injection). The radiation it emits, detected by a scanner and recorded, reflects its distribution in different tissues and can reveal the presence, size, and shape of abnormalities in various organs. The isotopes used have short half-lives and decay before radioactivity causes any damage.

The main role of the Nuclear Medicine Consultant is, in common with all medical specialities, the assessment of the patient. The Nuclear Medicine Consultant is responsible not only for assessment of the patient, but also to select the most appropriate nuclear medicine investigation.


A doctor who specialises in treating cancer patients.

The study and treatment of cancer.

The study and treatment of bones and muscles.


See Positron Emission Tomography.

Combined PET and CT scanning on a single scanner, which has both PET and CT components in a single gantry.

A pacemaker is an electronic device used to treat patients who have symptoms caused by abnormally slow heartbeats. A pacemaker is capable of keeping track of the patient’s heartbeats. If the patient’s heart is beating too slowly, the pacemaker will generate electrical signals similar to the heart’s natural signals, causing the heart to beat faster. The purpose of the pacemaker is to maintain heartbeats so that adequate oxygen and nutrients are delivered through the blood to the organs of the body.

The branch of medicine that deals with laboratory examination of samples of body tissue for diagnostic and forensic purposes.

Relates to changes in the physiology, the normal functioning or state of the body, or a tissue or organ.

An imaging technique that uses small quantities of a radioactive tracer similar to sugar (18Fluorodeoxyglucose) to produce images showing how your body is functioning. PET visualises active tissue and cells as opposed to the body’s anatomy and structure. You will be injected with a non-harmful radioactive tracer that acts like glucose and travels all around the body. This tracer collects in active areas of your body, such as cancer cells and is imaged using a PET scanner. PET is primarily used in imaging cancer and can provide doctors with useful information at many stages of the disease process, such as diagnosis, staging or treatment evaluation. Applications for PET in cardiology and neurology are also on the increase.

A drug given to a patient with written instructions from a doctor.


(Radioactivity): Strictly speaking, radiation means giving off any energy particles or waves and includes heat and light but is usually used in relation to radioactivity. This means gamma rays, alpha or beta particles from a radioactive source. The radioactivity comes from the breakdown of atoms. The source can be natural or made in a nuclear reactor. Uncontrolled radiation can be dangerous and cause cancer. Controlled exposure to radiation can be used in medicine for diagnosis (eg X-rays) or to treat cancer (radiotherapy).

Radio frequency pulses or radio waves are used in MRI as part of the imaging process. The Radio frequency (RF) pulses are emitted by the scanner and cause the body’s water molecules, which have small magnetic fields, to change direction. Once the RF pulses are turned off the magnetic field of the water molecules go back to the original position, and they then give off their own radio waves which are picked up by the MRI system and turned into a medical image by the systems computer.

Something that gives off high energy rays or particles.

Type of internal radiotherapy. The radiation is given in liquid form as a drink (eg radioactive iodine) to treat cancer of the thyroid.

Dye which gives off radiation, this is used in very small amounts during some types of scan.

Injection into a vein of a tiny amount of a radioactive substance. This is usually done for a scan, for example a bone scan. But it can also be a treatment such as P32.

Radioactively labelled sugar, i.e. FDG (see Fluoro-Deoxy-Glucose)

A material that can be distinguished from its normal counterpart by its radioactivity and can be used to follow (trace) the metabolism of the normal substance.

Person trained to operate the scanner and who will look after you during your appointment.

A doctor who specialises in reading X-rays and scans, and carrying out scans and other specialist X-ray techniques.

Branch of medicine that uses radiation for diagnosis (diagnostic imaging) and treatment (radiation therapy) of disease.

Radioactive atoms used in tiny amounts as a tracer in a bone scan.

Doctor who specialises in treating patients with radiotherapy.

(Radiotherapy Treatment, Radium Treatment): Cancer treatment using high energy waves similar to X-rays. Used to be called radium treatment because all radiotherapy used to be given using radium.


Looking at the inside of the body from the outside to see if there is anything wrong (eg CT scan or MRI scan).

A medical device with which images of the body are obtained.

(Screening Programme, Screening Test, Screening Tests): Testing the general population to see if a particular disease can be picked up early – usually before that person has noticed any symptoms. Can only be done if there is a reliable and simple test for the disease, as with the cervical smear test or mammogram.

A sedative that relieves anxiety. Most sedatives act as mild depressants of the nervous system, lessening general nervous activity or reducing the irritability or activity of a specific organ. Sedatives taken in small quantities are useful in relieving coughing, nausea, or convulsions and in lessening anxiety.

A classification of cancer that looks at the size, site and spread of the disease.

A clip used in surgery to close off a bleeding blood vessel or for closing wounds.


A collection of cells similar in form and function. An example of a tissue would be muscle.

A scan covering the whole patient, from head to toe.

A material that can be distinguished from its normal counterpart by physical means (for instance in the case of FDG this is radioactivity) and can therefore be used to follow (trace) the metabolism of the normal substance.


(Ultrasound Scan, Ultrasound Scans): Scan using sound waves to build up a picture of the inside of the body. A gel is put on the skin and a microphone passed back and forth over the area to be scanned. A computer converts the reflected sound waves into a picture on a screen. Please refer to our Ultrasound information page for further information.

(UVA, UVB): Ultraviolet light is light that we cannot see as it has a wave length shorter than the visible light we can see; but it’s an important part of sunlight. Ultraviolet light is divided into UVA, UVB and UVC. UVC has the shortest wavelength and cannot get through the ozone layer to reach us. But UVA and UVB have both been linked to skin cancer, including malignant melanoma. Both sunbathing and using sun beds increases your skin’s exposure to ultraviolet light and so increases your risk of skin cancer.


A scan covering more than one bed position, typically either the entire body, head to toe, or the trunk. Often used in oncology scans.


This is a type of imaging technique that uses electromagnetic radiation of extremely short wavelength to generate pictures of inside the human body. X-rays travel at the speed of light and exhibit phenomena associated with waves, but experiments indicate that they can also behave like particles. On the electromagnetic spectrum, they lie between gamma rays and ultraviolet radiation. Please refer to our Patient Information page on X-ray for further information.

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