Radiology & Nuclear Medicine Chapter 20 Pages 849 – 880

Introduction Page 850 Radiology X-rays Nuclear medicine Education of professionals Radiology = medical specialty concerned with the study and application of x-rays and other technology (such as ultrasound and magnetic resonance) to produce and interpret images of the human body for the diagnosis of disease. X-rays = invisible waves of energy that are produced by an energy source (such as an x-ray machine or cathode ray tube) and are useful in the diagnosis and treatment of disease. Nuclear medicine = medical specialty that uses radioactive substances (radionuclides) in the diagnosis and treatment of disease. The professionals involved in these medical fields differ in practice and level of education or training.

Personnel in Radiology and Nuclear Page 850 Personnel in Radiology and Nuclear Radiologist Nuclear medicine physician Radiologic technologists Radiographers Nuclear medicine technologists Sonographers Radiologist = a physician who specializes in the practice of diagnostic radiology. Nuclear medicine physician = specializes in diagnostic radionuclide scanning procedures. Radiologic technologists = allied health care professionals who work with physicians in the fields of radiology & nuclear medicine. Different types radiologic technologists are: Radiographers; Nuclear medicine technologists; & Sonographers

Characteristics of X-Rays Pages 850 – 851 Characteristics of X-Rays Ability to cause exposure of a photographic plate Ability to penetrate different substances to varying degrees Invisibility Travel in straight lines Scattering of x-rays Ionization 1) Ability to cause exposure of a photographic plate – used to take x-rays! 2) Ability to penetrate different substances to varying degrees – this along with the preceding makes x-rays useful for seeing structures in the body without surgery. 3) Invisibility – this makes x-rays dangerous because x-rays can cause damage to DNA. To much exposure can hurt you and you can see them so people who work in this field wear an indicator to keep track of how much they are being exposed to. If exposed to too much they must find an new profession. (This is just a precaution) 4) Travel in straight lines – can control where the x-rays travel 5) Scattering of x-rays – when it hits anything. This is doesn’t really serve a purpose but it is a property of x-ray that must be taken into account when taking an x-ray so that it doesn’t mess up the x-ray image. (I.E. a grid contain thin lead strips is arranged parallel to the x-ray beams to absorb scatted radiation before it strikes the x-ray film) 6) Ionization – helps kill cancer cells, but it can also harm healthy cells. A person exposed to high doses of x-rays is at risk for the development of leukemia, thyroid tumors, breast cancer, or other malignancies.

Diagnostic Techniques: X-Ray Studies Page 852 – 853 Diagnostic Techniques: X-Ray Studies Digital radiography Computed tomography (CT) X-ray imaging is used in a variety of ways to detect pathologic conditions. The chest x-ray is the most commonly performed diagnostic x-ray examination. Another common use of x-rays is in dental practice to locate caries in teeth. Mammography uses low-dose x-rays to visualize breast tissue. Digital radiology = digital x-ray sensors are used instead of traditional photographic film. Thus images can be enhanced and transferred easily, and less radiation can be used than in conventional radiography. Computed Tomography (CT) = The CT scan is made by beaming x-rays at multiple angles through a section of the patient’s body. The absorption of all of these x-rays, after they pass through the body, is recorded and used by a computer to create multiple cross-sectional images. The ability of a CT scanner to detect abnormalities is increased with the use of iodine-containing contrast agents, which outline blood vessels and confer additional density to soft tissues. CT scanners are highly sensitive in detecting disease in bones & can actually provide images of internal organs that are impossible to visualize with ordinary x-ray technique. New ultrafast CT scanners can produce a 3D image of a beating heart & surrounding blood vessels. State of the art scanners produce 64, 128, 256, & 320 images per rotation & are called multi-detector CT or MDCT scanners.

DT: X-Ray Studies (Cont’d) Page 852 – 854 DT: X-Ray Studies (Cont’d) Contrast studies – Barium sulfate: upper GI small bowel follow-through barium enema double-contrast study Contrast Studies - In radiography, the natural differences in the density of body tissues produce contrasting shadows on the radiographic image. However, when x-rays pass through two adjacent body parts composed of substances of the same density, their shadow cannot be distinguished from one another on the film or on the screen. It is necessary, then, to place a contrast medium into the structure or fluid to be visualized so that a specific part, organ, tube, or liquid can be seen as a negative imprint on the dense contrast agent. density of body tissues (e.g., from air in lung or from calcium in bone) same density (e.g., different digestive organs in the abdomen), Barium sulfate is often used as contrast material – in a double contrast study both barium & lumen is used. Barium sulfate: upper GI (UGI) – involves oral ingestion of barium sulfate so that the esophagus, stomach, and duodenum, can be visualized. Small bowel follow-through (SBFT) – series traces the passage of barium in a sequential manner as it moves through the small intestine barium enema (BE) – study is a lower GI series that opacifies the lumen (passageway) of the large intestine using an enema containing barium sulfate. However this test has been replaced by endoscopy, which allows visualization of the inside of the bowels. Double-contrast study – uses both a radiopaque and a radiolucent contrast medium. For example, the walls of the stomach or intestine are coated with barium and the lumen is filled with air. These radiographs show the pattern of mucosal ridges.

DT: X-Ray Studies (Cont’d) Page 854 DT: X-Ray Studies (Cont’d) Contrast studies – Iodine compounds: angiography arthrography Iodine compounds. Radiopaque fluids containing up to 50% iodine are used in the following tests: angiography – x-ray image (angiogram) of blood vessels and heart chambers is obtained after contrast is injected through a catheter into the appropriated blood vessel or heart chamber. (Picture AB) arthrography - a type of medical imaging used to help evaluate and diagnose joint conditions and unexplained pain. It is very effective at detecting disease within the ligaments, tendons and cartilage. It may be indirect, where contrast material is injected into the bloodstream, or direct, where contrast material is injected into the joint. Arthrography may use computed tomography (CT) scanning, magnetic resonance imaging (MRI) or fluoroscopy – a form of real-time x-ray. With direct arthrography, however, the contrast material is injected directly into the joint by a radiologist. Direct arthrography is preferred over indirect arthrography because it distends or enlarges the joint thus allowing for enhanced imaging of small internal structures. This leads to improved evaluation of diseases or conditions within the joint. It is often performed only if a non-arthrographic exam is felt to be inadequate in assessing a joint abnormality.

DT: X-Ray Studies (Cont’d) Page 854 – 856 DT: X-Ray Studies (Cont’d) Contrast studies – Iodine compounds: cholangiography digital subtraction angiography (DSA) hysterosalpingography myelography pyelography cholangiography – x-ray imaging after injection of contras into bile ducts. (Picture – percutaneous transhepatic cholangiography) digital subtraction angiography (DSA) – x-ray image of contrast-injected blood vessels is produced by taking two x-ray pictures (the first without contrast) 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 (myel/o) after injection of contrast agent into the subarachnoid space surrounding the spinal cord. pyelography – x-ray imaging of the renal pelvis and urinary tract.

Diagnostic Techniques: X-Ray Studies Page 856 – 857 Diagnostic Techniques: X-Ray Studies Digital imaging techniques Interventional radiology Fluoroscopy Radiofrequency ablation Ultrasound Digital imaging techniques – can be used to enhance conventional and fluoroscopic x-ray images. Interventional radiology – Invasive procedures (therapeutic or diagnostic) usually under CT or ultrasound guidance or with fluoroscopic imaging. Fluoroscopy – use of x-rays and a fluorescent screen to produce real-time video images. Procedures include: percutaneous biopsy, placement of drainage catheters, drainage of abscesses, occlusion of bleeding vessels, and catheter instillation of antibiotics or chemotherapy agents. Radiofrequency ablation – destruction of tumors and tissues (liver, kidney, lungs, and adrenals). Ultrasound – uses high frequency inaudible sound waves that bounce off body tissues and are then recorded to give information about the anatomy of an internal organ. The record produced by ultrasound imaging is called a sonogram. (picture A – Doppler ultrasound scan showing an image of the vena cava (in blue).) (picture B – Color flow imaging in a patient with aortic regurgitation. The brightly colored, high-velocity jet (arrow) can be seen passing from the aorta (AO) to the left ventricle (LV). The center of the jet is white, and the edges are shades of blue.)

Diagnostic Techniques: X-Ray Studies Page 858 Diagnostic Techniques: X-Ray Studies Magnetic imaging or magnetic resonance imaging (MRI or MR) Magnetic imaging or magnetic resonance imaging (MRI or MR) - uses magnetic fields & radio-waves rather than x-rays. Hydrogen protons are aligned & synchronized by placing the body in a strong magnetic field & exposing it to radio-waves. The rates of alignment & relaxation vary from one tissue to the next, producing a sharply defined picture. Because bone is virtually devoid of water, it is not well visualized on MRI. This technique produces sagittal (lateral), frontal (coronal), & axial (cross-sectional) images as well as images in oblique (slanted) planes. MRI provides excellent soft tissue images, detecting edema in the brain, providing direct imaging of the spinal cord, detecting tumors in the chest & abdomen, & visualizing the cardiovascular system. MRI is contraindicated for patients with pacemakers or metallic implants because the powerful magnet can alter position & functioning of such devices. However, the FDA has recently approved new pacemakers that can be safely used with MRI. The sounds (loud tapping) heard during the test are caused by the pulsing of the magnetic field components as the device scans the body. (picture A – Frontal (coronal) view of the upper body. White masses in the chest are Hodgkin lymphoma lesions.) (Picture B – Axial (cross-sectional) view of the upper body in the same patient, who had a chest mass.) (Picture C – Sagittal (lateral) view of head showing cerebrum, ventricles, cerebellum, and medulla oblongata)

X-Ray Positioning Page 859 In order to take the best picture of the part of the body being radiographed, the patient, detector, and x-ray tube must be positioned in the most favorable alignment possible. Radiologist use special terms to refer to the direction of travel of the x-rays through the patient’s body. Radiographic views that are defined by the direction of the x-ray beam relative to the patient, who is positioned between the source and the detector. Posteroanterior (PA) view = posterior source to anterior detector. The posteroanterior view of the chest is the most commonly requested chest x-ray. Anteroposterior (AP) view - anterior source to posterior detector. Lateral view = in left lateral view, source at right of patient, to detector at left of patient Oblique view = source slanting direction at angle from perpendicular plane. X-rays travel in a slanting direction at an angle from the perpendicular plane. Oblique view show regions or structures ordinarily hidden or superimposed in routine PA & AP views.

X-Ray Positioning (Cont’d) Page 860 X-Ray Positioning (Cont’d) abduction inversion adduction recumbent decubitus prone eversion supine extension flexion abduction – movement away from the midline of the body adduction – movement away toward the midline of the body decubitus – Lying down eversion – Turning outward extension – Lengthening or straightening a flexed limb flexion – Bending a part of the body inversion – Turning inward recumbent – Lying down (may be prone or supine) prone – Lying on the belly (face down) supine – Lying on the back (face up)

Nuclear Medicine Page 860 Radioactivity Radionuclide alpha particles beta particles gamma rays ➢ have greater penetrating ability than alpha and beta particles Radioactivity = the spontaneous emission of energy in the form of particles or rays coming from the interior of a substance. Radionuclide (radioisotope)= a substance that gives off high-energy particles or rays as it disintegrates. Radionuclides emit three types of radioactivity: alpha particles, beta particles, and gamma rays. Gamma rays, which have greater penetrating ability than alpha and beta particles, and more ionizing power, are especially useful to physicians in both the diagnosis and the treatment of disease. Radionuclides are produced in either a nuclear reactor or a charged-particle accelerator (cyclotron) or by irradiating stable substances, causing disruption & instability. Half-life is the time required for a radioactive substance (radionuclide) to lose half of its radioactivity by disintegration. Knowledge of a radionuclide’s half-life is important in determining how long the radioactive substance will emit radioactivity when in the body. The half-life must be long enough to allow for diagnostic imaging but as short as possible to minimize patient exposure to radiation. Technetium-99m (99mTc) is essentially a pure gamma emitter with a half-life of 6 hours. Its properties make it the most frequently used radionuclide in diagnostic imaging.

Nuclear Medicine (Cont’d) Pages 860 – 861 Nuclear Medicine (Cont’d) Two types of tests in the diagnosis of disease: in vitro procedures in vivo procedures Nuclear medicine physicians use two types of tests in the diagnosis of disease: in vitro (in the test tube) procedures: involve analysis of blood and urine specimens using radioactive chemicals. Radioimmunoassay (RIA) uses radioactive chemicals and antibodies to detect hormones and drugs in the patient’s blood (for example, digitalis detection, hypothyroidism in newborns). in vivo (in the body) procedures: involve trace the amounts of radioactive substances within the body. They are given directly to the patient to evaluate the function of an organ or to image it. Radiopharmaceutical (labeled compound) concentrates in organ. Amounts of radiopharmaceuticals detected at a given location or organ are proportional to the rate at which the gamma rays are emitted. Scintiscanner (gamma camera) detection instrument produces picture (scintiscan) (Picture A – Patient receiving IV injection of radionuclide for detection of heart function) (Picture B – Gamma camera moves around the patient, detecting radioactivity in heart muscle.)

Procedures Using Radionuclides Pages 861 – 862 Procedures Using Radionuclides Bone scan Lymphoscintigraphy Bone scan – Technetium-99m (Tc-99m) is used to label a phosphate-containing substance, which then is injected intravenously. Which is then taken up by the skeleton in approximately 2-3 hours. (pictures) Lymphoscintigraphy – This type of nuclear medicine imaging provides pictures (scintigrams) of the lymphatic system.

Procedures Using Radionuclides (Cont’d) Page 862 Procedures Using Radionuclides (Cont’d) Positron emission tomography (PET) scan PET-CT scan Single-photon emission computed tomography (SPECT) Positron emission tomography (PET) scan – this radionuclide technique produces images of radioactivity in the body through emission of positrons. It is similar to CT. Radioisotopes (emission of positrons) instead of contrast x-rays Intravenous injection Concentrates radioisotopes in tissues where the radionuclide is or is not being metabolized Useful in treating stroke, epilepsy, Alzheimer disease, brain tumors, abdominal and pulmonary malignancies (Picture A&B – Whole body sagittal PET images. Image B was obtained after chemotherapy.) PET is an acronym for positron emission tomography. PET-CT scan – combines PET and CT to produce a more accurate image than PET or CT alone. 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. Intravenous injection of radioactive tracer Computer reconstruction of 3-D image based on many views Detects liver tumors, cardiac ischemia, diseases of bone and spine SPECT is an acronym for single-photon emission computed tomography.

Procedures Using Radionuclides (Cont’d) Pages 862 – 863 Procedures Using Radionuclides (Cont’d) Technetium Tc-99m sestamibi (Cardiolite) scan Thallium (Tl) scan Thyroid scan Technetium Tc-99m sestamibi (Cardiolite) scan – for this scan, the technietium radiopharmaceutical is injected intravenously and traced to heart muscle. Thallium (Tl) scan – Tl-201 is injected intravenously to evaluate myocardial perfusion. Thyroid scan – an iodine radionuclide, usually iodine 123, is administered orally, and the scan reveals the size, shape, and position of the thyroid gland. (Picture) Radioactive iodine uptake (RAIU) study is performed to assess the function of the thyroid gland (such as hyperthyroidism).