16. RADIOLOGY TERMS

Radiology: Radiology is the medical specialty concerned with the study of x-rays.

X-rays: X-rays are invisible waves of energy that are produced by an energy source

(x-ray machine, cathode ray tube) and are useful in the diagnosis and treatment of

disease.

Nuclear medicine: It is the medical specialty that studies the characteristics and

uses of radioactive substances in the diagnosis of disease.

Radioactive substances: They are materials that emit high-speed particles and

energy-containing rays from the interior of their matter.

Gamma rays: They are used effectively as a diagnostic label to trace the path and

uptake of chemical substances in the body.

Radiologist: A radiologist is a physician who specializes in the practice of diagnostic

radiology.

Nuclear medicine physician: A nuclear medicine physician specializes in diagnostic

nuclear medicine procedures.

Radiologic technologists: Allied health care professionals who work with

physicians in the fields of radiology and nuclear medicine.

Radiolucent: Permitting the passage of x-rays. Radiolucent structures appear black

on x-ray film.

Radiopaque: Obstructing the passage of x-rays. Radiopaque structures appear

white on the x-ray film.

Ionization: Transformation of electrically neutral substances into electrically

charged particles. X-ray cause ionization of particles within tissues.

Computed tomography: Diagnostic x-ray procedure whereby a cross-sectional

image of a specific body segment is produced. Newer CT scanners can create 3D

images as well.

Contrast studies: Materials are injected to obtain contrast with surrounding tissue

when shown on the x-ray film.

Barium sulfate: It is a Radiopaque medium that is mixed in water and used for

examination of the upper and lower GI tract.

Angiography: X-ray image of blood vessels and heart chambers is obtained after

contrast is injected through a catheter into the appropriate blood vessel or heart

chamber,

Coronary angiography: It determines the degree of obstruction of the arteries that

supply blood to the heart.

Arthrography: Contrast or air or both are injected into a joint, and x-ray images pf

the joint are obtained.

Cholangiography: X-ray imaging after injection of contrast into bile ducts.

Digital subtraction angiography (DSA): X-ray image of contrast-injected blood

vessels is produced by taking two x-ray pictures and using a computer to subtract

obscuring shadows from the second image.

Hysterosalpingography: X-ray record of the endometrial cavity and fallopian tubes

is obtained after injection of contrast material through the vagina and into the

endocervical canal.

Myelography: X-ray imaging of the spinal cord after injection of contrast agent into

the subarachnoid space surrounding the spinal cord.

Pyelography: X-ray imaging of the renal pelvis and urinary tract.

Fluoroscopy: X-ray technique that produces a fluorescent image on an image

intensifier.

Fluorescence: Emission of glowing light results from exposure to and absorption of

radiation from x-rays.

Cineradiography: Use of motion picture techniques to record a series of x-ray

images during fluoroscopy.

Ultrasonography: Diagnostic technique that projects and retrieves high-frequency

sound waves as they echo off parts of the body.

Transducer: An instrument called transducer or probe is places near or on the skin,

which is covered with a thin coating of gel to ensure good transmission of sound

waves.

Echocardiography: Ultrasound imaging is used as a diagnostic tool by cardiologists

to detect heart valve and blood vessel disorders.

Doppler ultrasound and color-flow imaging: These two ultrasound techniques

make it possible to record blood flow velocity and to mage major blood vessels in

patients at risk for stroke.

Magnetic Resonance Imaging (MRI): Magnetic field and radio waves produce

sagittal, coronal and axial images of the body.

Gadolinium: MRI examinations are performed with and without contrast. The

contrast agent most commonly used is Gadolinium. It enhances vessels and tissues,

increases the sensitivity for lesion detection, and helps differentiate between normal

and abnormal tissues and structures.

Posteroanterior view (PA): In this most commonly requested chest x-ray view, xrays

travel from a posteriorly placed source to an anteriorly placed detector.

Anteroposterior view (AP): X-rays travel from an anteriorly placed source to a

posteriorly placed detector.

Lateral view: In a left lateral view, x-rays travel from a source located to the right

of the patient to a detector placed to the left of the patient.

Oblique view: X-rays travel in a slanting direction at an angle from the

perpendicular plane. Oblique views show regions or structures ordinarily hidden and

superimposed in routine PA and AP views.

Radioactivity: The emission of energy in the form of particles or rays coming from

the interior of a substance is called radioactivity.

Radionuclide: It is a substance that gives off high-energy particles or rays as it

disintegrates.

Half-life: It is the time required for a radioactive substance to lose half of its

radioactivity by disintegration.

In vitro: Process, test, or procedure is performed, measured or observed outside a

living organism.

In vivo: Process, test, or procedure is performed, measured or observed within a

living organism.

Radioimmunoassay: Test combines radioactive chemicals and antibodies to detect

minute quantities of substances in a patient’s blood.

Radiopharmaceutical: Radioactive drug that is administered safely for diagnostic

and therapeutic purposes.

Gamma camera: Machine to detect gamma rays emitted from radiopharmaceuticals

during scanning for diagnostic purposes.

Radionuclide scanning: The procedure of making an image to track the

distribution of radioactive substance in the body is radionuclide scanning.

Uptake: It refers to the rate of absorption of the radiopharmaceutical into an organ

or tissue.

Technetium-99m (99mTc): It is essentially pure gamma emitter with a half-life of 6

hours. Its properties make it the most frequently used radionuclide in diagnostic

imaging.

Bone scan: 99mTc is used to label phosphate substances and then is injected

intravenously. The phosphate compound is taken up preferentially by bone, and the

skeleton is imaged in 2 or 3 hours. Waiting 2 to 3 hours allows much of the

radiopharmaceutical to be excreted in urine and allows for better visualization of the

skeleton. The scan detects infection, inflammation or tumors involving the skeleton,

which appears as areas of high uptake on the scan.

Gallium scan: The radioisotope gallium 67 is injected intravenously and has an

affinity for tumors and non-neoplastic lesions such as abscesses. Gallium also has an

affinity for areas of inflammation as occurs in pneumonitis.

Liver and spleen scans: To visualize the liver and spleen, a radiopharmaceutical is

injected intravenously, and images are taken with a gamma camera. Areas of tumor

or abscess are shown as photopenic areas (regions of reduced uptake).

Positron emission tomography (PET): It is similar to the CT scan, but

radioisotopes are used instead of contrast and x-rays.

Single photon emission computed tomography (SPECT): This technique

involves an intravenous injection of radioactive tracer and the computer

reconstruction of a 3D image based on a composite of many views.

Technetium Tc-99m sestamibi (Cardiolite) scan: The radiopharmaceutical is

injected intravenously and traced to heart muscle. An exercise tolerance test is used

with it for an ETT-MIBI scan.

MUGA: In a Multiple Gated Acquisition Scan, 99mTc is injected intravenously to study

the motion of the heart wall muscle and the ventricle’s ability to eject blood.

Thallium scan: Thallium-201 (201TI) is injected intravenously to evaluate myocardial

perfusion. A high concentration of 201TI is present in well-perfused heart muscle

cells, but infracted or scarred myocardium does not extract any thallium, showing up

as “cold spots”.

Thyroid scan: An iodine radionuclide, usually iodine-131 is administered

intravenously, and the scan reveals the size and shape of the thyroid gland.

Interventional radiology: Therapeutic procedures performed by a radiologist.

Scan: Image of an area, organ or tissue of the body obtained from ultrasound,

radioactive tracer studies, computed tomography, or MRI.

Ventilation-perfusion studies: Radiopharmaceutical is inhaled and injected

intravenously followed by imaging its passage through the respiratory tract.