Chapter 20 - Radiology and Nuclear Medicine

Gadolinium

contrast agent most commonly used, if used at all, in MRIs that enhances vessels and tissues, increases sensitivity for lesion detection, and helps differentiate between normal and abnormal tissues and structures

Radiofrequency Ablation

destruction of tumors and tissues performed by interventional radiologists

Coronary Angiography

determines degree of obstruction of arteries that supply blood to heart

Uptake

rate of absorption of radiopharmaceutical into organ or tissue

Sonogram

record produced by ultrasound imaging as ultrasound waves move through body and echo reflection of sound waves is formed as they hit various body tissues of different densities and bounce back to transducer; echoes are recorded as composite picture of area of body over which instrument passes

ETT-MIBI

scan where exercise tolerance test is used with technetium

Multiple Gated Acquisition

scan where technetium is intravenously injected to study motion of heart wall muscle and ventricle's ability to eject blood

Retrograde Pyelography

catheter is placed through urethra, bladder, and ureter and into renal pelvis to inject contrast

Upper GI Series

involves oral ingestion of barium sulfate so that esophagus, stomach, and duodenum can be visualized

Interventional Radiology

involves performing invasive procedures usually under CT or ultrasound guidance or with fluoroscopic imaging, such as fluoroscopy and radiofrequency ablation

Radionuclide Scanning

procedure of making image by tracking distribution of radioactive substance in body

Scintigraphy

process of obtaining images using radionuclide

Urography

process of recording x-ray. Images of urinary tract after introduction of contrast

Characteristics of X-Rays

1. Ability to cause exposure of photographic plate/image detector, so that x-rays traveling unimpeded through air expose silver coating of photographic plate and cause it to blacken 2. Ability to penetrate different substances to varying degrees, so that less dense substances allow greater transmission, while more dense materials have less transmission and absorb x-rays, preventing rays from reaching photographic plate and leaving white areas in plate (from least dense to most dense - air, water, fat, and metals like Ca2+ in bones) 3. Invisibility as x-rays can't be detected by sight, hearing, or touch, so workers must wear film badge 4. Travel in straight lines allowing formation of precise shadow images on plate and permits x-ray beams to be directed accurately at tissue site 5. Scattering of x-rays that occurs when x-rays come in contact with any material, so occurs more with radiopaque (dense) objects than radiolucent objects; can cause blurring on images, so grid with thin lead strips is placed in front of image detector to absorb scattered radiation before it strikes x-ray film 6. Strong ability to ionize substances through which x-rays pass, an effect that can help kill cancerous cells/stop tumor growth, but can negatively affect normal body cells by causing tissue damage and malignant changes (high exposure comes with risk of malignancies)

Pyelography

x-ray imaging of renal pelvis and urinary tract with injection of iodine contrast material

Barium Sulfate

radiopaque substance/contrast material that is mixed with water and used for examination of upper and lower GI tract

Perfusion Study

radiopharmaceutical is given intravenously in a lung scan so that radioactive compound travels through lung capillaries

Radiologic Technologists

allied health care professionals who work with physicians in fields of radiology and nuclear medicine, such as radiographers (help administer diagnostic x-ray procedures), nuclear medicine technologists (help with patients undergoing nuclear medicine procedures and operate devices), and sonographers (aid in performing ultrasound procedures)

Ionization

chemical process in which energy of x-ray beam causes rearrangement and disruption within a substance, so that previously neutral particles are changed to charged particles (ions)

Radiopharmaceutical

combination of radionuclide and drug/chemical given in trace studies; each is designed to concentrate in certain organ, which can be imaged using radiation given off by radionuclide; amount of this at given location is proportional to rate at which gamma rays are emitted

Digital Radiography

form of x-ray imaging where digital x-ray sensors are used instead of traditional photographic film, enhancing images and allowing for easy transfer; uses less radiation than in conventional radiography; ex: chest x-ray, x-rays to locate cavities

CT Scan Advantages

highly sensitive in detecting bone diseases and provides images of internal organs that are impossible to visualize with ordinary x-ray technique; useful for visualizing bones, lungs, and solid masses of chest and abdomen

X-Ray Positioning

important in order to take best picture of part of body being radiographed; terms for most favorable alignments define direction of x-ray beam relative to patient who is positioned between source and image detector (photographic plate)

In Vivo

in body procedure used by nuclear medicine physician; given directly to patient to evaluate function of or to image organ by tracing amounts of radioactive substances within body

Lateral View

in left version of this, x-rays travel from source located to right of patient to detector placed to left of patient

In Vitro

in test tube procedure used by nuclear medicine physicians, involving analysis of blood and urine specimens using radioactive chemicals

Radioimmunoassay

in vitro procedure combining use of radioactive chemicals and antibodies to detect hormones and drugs in patient's blood; test allows detection of minute amounts of substances or compounds; monitors amount of digitalis drug used to treat heart disease in bloodstream and detects hypothyroidism in newborn

Positron Emission Tomography

in vivo radionuclide technique that produces images of distribution of radioactivity in body through emission of positrons; after intravenous injection, radionuclides are incorporated into tissues and image is made showing where radionuclide is or is not being metabolized; identifies areas of metabolic deficiency, which is important for diagnosing and treating neurologic disorders; areas of infection, inflammation, and tumor have increased metabolic activity as highlighted by this

Trace Studies

in vivo test where specific radiopharmaceutical is administered to patient and target organ is imaged as radiation is given off by radionuclide

PET-CT Scan

in vivo trace studies that combine PET and CT techniques to produce more accurate image than either alone; used to detect cancer/metastases and if cancer is responding to treatment

Single Photon Emission Computed Tomography

in vivo trace study technique that involves intravenous injection of radioactive tracer and computer reconstruction of 3D image based on composite of many views; used to detect liver tumors, brain function, cardiac ischemia, and bone disease of spine

Lymphoscintigraphy

in vivo trace study that provides pictures of lymphatic system; small needle injects radiotracer under skin or deeper and gamma camera takes series of images of area of body; performed to identify sentinel lymph node, identify areas of lymph node blockage, or evaluate lymphedema

Bone Scan

in vivo trace study where Technetium-99m labels phosphate-containing substance, which gets injected intravenously; radioactive phosphate compound is taken up by bone and skeleton is imaged after 2-3 hours to allow time for most of radiopharmaceutical to be excreted in urine, allowing better visualization of radioactive material remaining in skeleton; detects infection, inflammation, or tumors involving skeleton, appearing as areas of high uptake on scan

Thyroid Scan

in vivo tracer studies where iodine radionuclide is given orally and scan reveals size, shape, and position of thyroid; hyperfunctioning thyroid nodules (adenomas) accumulate higher amounts of radioactivity (hot spots), while thyroid carcinoma does not concentrate radioiodine well (cold spot)

Technetium 99m Sestamibi Scan

in vivo tracer studies where technetium radiopharmaceutical is intravenously injected and traced to heart muscle

Thallium Scan

in vivo tracer studies where thallium-201 is intravenously injected to evaluate myocardial perfusion; high concentration of thallium-201 is present in well-perfused heart muscle cells but infarcted or scarred myocardium doesn't take thallium up and shows as cold spots (if defective area is ischemic, cold spot fills in on delayed images)

Contrast Studies

natural differences in density of body tissues produce contrasting shadows, but x-rays passing through 2 adjacent body parts composed of substances of same density doesn't allow for distinguishable shadows on film/screen, so it is necessary to place contrast medium (barium sulfate, iodine compounds) into a structure or fluid to be visualized so that a specific part, organ, tube, or liquid can be seen as negative imprint on dense contrast agent

X-Rays

invisible waves of energy produced by an energy source (machine, cathode ray tube) and are useful in diagnosis and treatment of disease; imaging form used to detect pathologic conditions

Recumbent

lying down in prone or supine position

Supine

lying on back, face up

Prone

lying on belly, face down

CT Scan

made by beaming x-rays at multiple angles through section of patient's body (rotating x-ray source/detectors) and absorption of x-rays after passing through body is recorded and used by computer to create multiple cross-sectional images; ability to detect abnormalities is increased with use of iodine-containing contract agents that outline blood vessels and confer additional density to soft tissues

Functional MRI

measures brain activity by detecting changes associated with blood flow as brain regions in use involve increase in blood flow to that area; evaluates effects of stroke/brain diseases and can determine parts of brain that are functioning (in thought, speech, movement, and sensation)

Radiology

medical specialty concerned with study and application of x-rays and other technologies (ultrasound, MRI) to produce and interpret images of human body for diagnosis of disease

Nuclear Medicine

medical specialty that uses radionuclides in diagnosis and treatment of disease; studies depict physiologic behavior rather than anatomy

Decubitus

patient is lying down

Lateral Decubitus

patient is lying down on the side

Ventilation Perfusion Study

permits sensitive and specific diagnosis of clots in lung arteries (pulmonary emboli)

Radiologist

physician specializing in practice of diagnostic radiology

MRI Advantages

provides excellent soft tissue images, detecting edema in brain, providing direct imaging of spinal cord, detecting tumors in chest/abdomen, and visualizing cardiovascular system; better at detailing soft tissues that have more water molecules

Technetium-99m

pure gamma emitter with 6 hour half life, making it most frequently used radionuclide in diagnostic imaging

Radioiodine

radioactive iodine that is absorbed into bloodstream after swallowing and travels to thyroid gland where it destroys overactive thyroid tissue in order to treat hyperthyroidism; used in radioactive iodine uptake studies to assess thyroid

Radionuclides

radioactive substances used in nuclear medicine that are materials that emit radioactivity (high-speed particles and energy-containing rays) from interior of their matter as they disintegrate; types are alpha particles, beta particles, and gamma rays AAK radioisotope

Double Contrast Study

radiograph using radiopaque and radiolucent contrast medium, showing pattern of mucosal ridges; ex: walls of stomach or intestines are coated with barium and lumen is filled with air

Ventilation Study

radiolabeled gas or aerosol is inhaled to fill air alveoli before imaging

Gamma Rays

radionuclide used effectively as diagnostic label to trace path and uptake of chemical substances in body; have greater penetrating ability than alpha and beta particles and have more ionizing power

Iodine Compounds

radiopaque fluids/contrast materials containing up to 50% iodine use in angiography, cholangiography, digital subtraction angiography, hysterosalpingography, myelography, and pyelography

Gamma Camera

sensitive, external detection instrument used to determine distribution and localization of radiopharmaceutical in various organs, tissues, and fluids

Endoscopic Ultrasonography

small ultrasound transducer is attached to tip of endoscope inserted into body; technique used by gastroenterologists and pulmonologists to obtain high-quality and accurate detailed images of digestive and respiratory systems

Ultrasound Advantages

sound waves are not ionizing and do not injure tissues at energy ranges used for diagnostic purposes

Nuclear Medicine Physician

specializes in diagnostic radionuclide scanning procedures

Radioactivity

spontaneously emitted energy in form of particles or rays from radionuclides

Multidetector CT Scanners

state of the art CT scanners that produce certain number of images per rotation

Barium Enema

study of lower Gi series that opacifies lumen of large intestine using enema containing barium sulfate; replaced by endoscopy, allowing for visualization of inside of bowel

Radioactive Iodine Uptake

study performed to assess thyroid gland function as patient receives radioactive iodine (radioiodine) in liquid or capsule form and sensor is placed over thyroid, detecting gamma rays emitted from radioactive tracer

Radiolucent

substance that permits passage of most x-rays and appears dark on x-ray image; ex: lung tissue filled with air

Radiopaque

substances that absorb most x-rays and only allow small fraction of x-rays to reach photographic plate, appearing white on x-ray image; ex: calcium-containing bones

Half Life

time required by radionuclide to lose half of its radioactivity by disintegration; must be long enough to allow for diagnostic imaging but as short as possible to minimize exposure to radiation

Small Bowel Follow Through Series

traces passage of barium in sequential manner as it moves through small intestine

Inversion

turning inward

Eversion

turning outward

Doppler Ultrasound and Color Flow Imaging

two ultrasound techniques that make it possible to record blood flow velocity; used to image major blood vessels to detect obstructions caused by atherosclerotic plaques in at-risk stroke patients

Ultrasonography

use of high-frequency inaudible sound waves that bounce off body tissues and are then recorded to give info about anatomy of internal organ; transducer/probe is placed under skin, which is covered with thin coating of gel to ensure good transmission of sound waves, and emits sound waves in short repetitive pulses

Fluoroscopy

use of x-rays and fluorescent screen to produce real time video images during procedures such as percutaneous biopsy, placement of drainage catheters, drainage of abscesses, occlusion of bleeding vessels, and catheter instillation of antibiotics/chemotherapeutic agents

Digital Imaging Techniques

used to enhance conventional and fluoroscopic x-ray images; use lower dose of x-rays to achieve higher quality images, which can be sent to other people to share info and assist in diagnostic process

Mammography

uses low-dose x-rays to visualize breast tissue

Magnetic Resonance Imaging

uses magnetic fields and radiowaves rather than x-rays; hydrogen protons are aligned and synchronized by placing body in strong magnetic field and exposing it to radiowaves, producing sharply defined pictures in sagittal, frontal, axial, and oblique (slanted) planes; doesn't visualize bones well since they're mostly devoid of water and can't be used for patients with pacemakers/metallic implants

Film Badge

worn by workers exposed to x-rays to detect and record amount of radiation they're exposed to; contains special film that reacts when exposed to x-rays and amount of blackness on film indicates amount of x-rays/gamma rays received by wearer

Angiography

x-ray image of blood vessels and heart chambers is obtained after iodine contrast is injected through catheter into appropriate blood vessel or heart chamber

Digital Subtraction Angiography

x-ray image of iodine contrast-injected blood vessels produced by taking 2 x-ray pictures where first is taken without contrast and then a computer subtracts obscuring shadows from second image with contrast

Cholangiography

x-ray imaging after injection of iodine contrast into bile ducts; contrast is injected directly into common bile duct in endoscopic retrograde cholangiopancreatography or after surgery of gallbladder or biliary tract in intraoperative cholangiography

Percutaneous Transhepatic Cholangiography

x-ray imaging of contrast into bile ducts using needle through skin and into liver with goal of visualizing biliary tree

Myelography

x-ray imaging of spinal cord after injection of iodine contrast material into subarachnoid space surrounding spinal cord (CT scans are also obtained)

Hysterosalpingography

x-ray record of endometrial cavity and fallopian tubes obtained after injection of iodine contrast material through vagina and into endocervical canal; determines patency of fallopian tubes

Anteroposterior View

x-rays travel from anteriorly placed source to posteriorly placed detector

Posteroanterior View

x-rays travel from posteriorly placed source to anteriorly placed detector; most commonly requested chest x-ray view

Oblique View

x-rays travel in slanting direction at angle from perpendicular plane; shows regions or structures ordinarily hidden or superimposed in routine posteroanterior or anteroposterior views