Chapter 20 Goals Page 849 Students will be able to: List the physical properties of x-rays. Identify diagnostic techniques use by radiologist & nuclear physicians Name the x-ray views & patient position used in x-ray examinations Describe the role of radioactivity in the diagnosis of disease Recognize medical terms used in the specialties of radiology & nuclear medicine Apply your new knowledge to understanding medical terms in their proper contexts, such as medical reports & records.

Radiology & Nuclear Medicine Chapter 20 Pages 849 – 880

Page 850 Introduction Radiology is the medical specialty concerned with the study & application of x-rays & other technology (such as ultrasound & magnetic resonance) to produce & interpret images of the human body for the diagnosis of disease. Nuclear medicine is the medical specialty that uses radioactive substances in the diagnosis & treatment of disease. The professionals involved in these medical fields differ in practice & level of education or training. radioactive substance (radionuclides) X-rays are invisible waves of energy that are produced by an energy source (such as an x-ray machine or cathode ray tube) & are useful in the diagnosis & treatment of disease. These radioactive substance are materials that emit high-speed particles & energy-containing rays from the interior of their matter. The emitted particles & rays are called radioactivity & can be of three types: alpha particles, beta particles, & gamma rays. Gamma rays use effectively as a diagnosis label to trace the path & uptake of chemical substances in the body.

Introduction: Cont. Page 850 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 Radiographers = who aid physician in administering diagnostic x-ray procedures; Nuclear medicine technologists = who attend to patients undergoing nuclear medicine procedures & operate devices under the direction of a nuclear physician Sonographers = who aid physicians in performing ultrasound procedures.

Radiology 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

Radiology: Cont. Page 852 Diagnostic Techniques – X-Ray Studies X-ray imaging is used in a variety of ways to detect pathologic conditions. Digital radiology is a form of x-ray imaging in which digital x-ray sensors are used instead of traditional photographic film. Thus images can be enhanced & transferred easily, & less radiation can be used than in conventional radiography. 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.

Radiology: Cont. Page 852 Diagnostic Techniques – X-Ray Studies 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 & 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 & 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.

Radiology: Cont. Pages 852 – 854 Diagnostic Techniques – X-Ray Studies 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.

Page 854 Radiology: Cont. Diagnostic Techniques – X-Ray Studies Contrast Studies – Iodine Compounds angiography X-ray image of blood vessels & heart chambers is obtained after contrast is injected through a catheter into the appropriate blood vessel or heart chamber cholangiography X-ray imaging after contrast injection into bile ducts

Page 855 Radiology: Cont. Diagnostic Techniques – X-Ray Studies Contrast Studies – Iodine Compounds digital subtraction angiography (DSA) X-ray image of contrast-injected blood vessels is produced by taking two x-ray pictures (first without contrast) & using a computer to subtract obscuring shadows from the second image myelography X-ray imaging of the spinal cord after injection of contrast agent in the subarachnoid space surrounding the spinal cord.

Radiology: Cont. Pages 855 – 856 Diagnostic Techniques – X-Ray Studies Contrast Studies – Iodine Compounds hysterosalpingography X-ray record of endometrial cavity & fallopian tubes is obtained after injection of contrast material through the vagina & into the endocervical canal pyelography X-ray imaging of the renal pelvis & urinary tract Patients can have a mild to sever reaction to the contrast X-ray imaging techniques can be used in real time to perform surgeries.

Radiology: Cont. Page 856 Diagnostic Techniques – Ultrasound Imaging A transducer (probe) is placed near or on the skin, which is covered with a thin coating of gel to ensure good transmission of sound waves. The transducer emits sound waves in short, repetitive pluses. The ultrasound waves move through body tissues & detect interfaces between tissues of different densities. An echo reflection of the sound waves is formed as they hit the various body tissues & bounce back to the transducer. Ultrasound imaging = ultrasonography Ultrasound imaging uses high-frequency inaudible sound waves that bounce off body tissues & are then recorded to give information about the anatomy of an internal organ.

Radiology: Cont. Pages 856 – 858 These ultrasonic echoes are then recorded as a composite picture of the area of the body over which the instrument has passed. The record produced by ultrasound imaging is called a sonogram. Ultrasound imaging has several advantages in that the sound waves are not ionizing & do not injure tissues at the energy ranges used for diagnostic purpose. Because water is an excellent conductor of the ultrasound beams, patients are requested to drink large quantities of water before examination so that the urinary bladder will be distended, allowing better viewing of pelvic & abdominal organs. Ultrasound imaging is used as a diagnostic tool not only by radiologist but also by neurosurgeons & ophthalmologists to detect intracranial & ophthalmic lesions. Cardiologists use ultrasound techniques to detect heart valve & blood vessel disorders, & gastroenterologists use it to locate abdominal masses outside the digestive organs. Similarly, pulmonologists use ultrasound procedures for locating & sampling lesions outside the bronchial tubes. Obstetricians & gynecologists use ultrasound imaging to differentiate single from multiple pregnancies, as well as to help in performing amniocentesis. Other uses are to image benign & malignant tumors & to determine the size & development of the fetus. Measurements of the head, abdomen, & femur are made from ultrasound images obtained in various fetal planes. Can be used to help with surgery

Page 858 Radiology: Cont. Diagnostic Techniques – Magnetic Resonance Imaging MRI 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.

Page 859 Radiology: Cont. 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. MRI examinations are performed with & without contrast. The contrast agent most commonly use is gadolinium (Gd). As iodine contrast does with CT, gadolinium enhances vessels & tissues, increases the sensitivity for lesion detection, & helps differentiate between normal & abnormal tissues & structures. contraindicated = this procedure should not be done

Radiology: Cont. Page 859 X-Ray Positioning In order to take the best picture of the part of the body being radiographed, the patient, detector, & 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. Listed next are terms for radiographic views that are defined by the direction of the x-ray beam relative to the patient, who is positioned between the source & the detector.

Page 859 Radiology: Cont. Posteroanterior (PA) view X-rays travel from a posteriorly placed source to an anteriorly placed detector Anteroposterior (AP) view X-rays travel from an anteriorly placed source to a posteriorly placed detector Lateral view X-ray travel from a source located to the right of the patient to a detect placed to the left of the patient Oblique view 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.

Radiology: Cont. Page 860 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 prone Lying on the belly (face down) recumbent Lying down (may be prone or supine) supine Lying on the back (face up)

Nuclear Medicine Page 860 Radioactivity & Radionuclides Radioactivity = the spontaneous emission of energy in the form of particles or rays coming from the interior of a substance. Radionuclide = a substance that gives off high- energy particles or rays as it disintegrates. Radionuclides emit three types of radioactivity: alpha particles, beta particles, & gamma rays. Gamma rays, which have greater penetrating ability than alpha & beta particles, & more ionizing power, are especially useful to physicians in both the diagnosis & the treatment of disease. radionuclide (or radioisotope) 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. Pages 860 – 864 Nuclear Medicine: Cont. Nuclear Medicine Tests: In Vitro & In Vivo Procedures Nuclear medicine physicians use two types of tests in the diagnosis of disease: in vitro (in the test tube) procedures & in vivo (in the body) procedures. In vitro procedures involve analysis of blood & urine specimens using radioactive chemicals. In vivo tests 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. Bone scan Lymphoscintigraphy Positron emission tomography (PET) PET-CT scan Single photon emission computed tomography (SPECT Technetium Tc99 sestamibi (Cardiolite) scan Thallium Scan Thyroid scan Radioactive iodine uptake (RAIU)