Ch. 46 Radiology (My Notes)

Safety

Any person working in a facility that performs radiologic tests can be at risk for excessive radiation exposure. Therefore, standard safety precautions must be followed to ensure protection for yourself and patients from radiation exposure. All staff working in the radiology department or taking radiographs must wear a personnel monitoring device to evaluate radiation exposure.

Each worker has a maximum permissible dose (MPD) they are allowed to be exposed to, and the limitations are determined by the age of the worker. There are many different kinds of devices used. One of the most widely used radiation monitoring devices is the optically stimulated luminescence (OSL) dosimeter.

These devices can detect radiation exposures as low as 1 millirem, and a read-out can be made without losing stored information.

note

Film badges are also frequently used dosimeters (Figure 46-1). This dosimeter has a sensitized piece of film in it that monitors the amount of radiation you are exposed to. They are economical and can detect both small and large exposures. The badges are sent in to the monitoring company they were purchased from and measured for exposure, and a report is sent back to the facility.

Thermoluminescent dosimeters (TLD)

look similar in appearance to film badges; however, they have a monitoring system that is quite different. When struck by ionizing radiation, special crystals inside them experience physical property changes. When heated up, the crystals give off light. The light is measured using a TLD analyzer and is proportional to the amount of radiation received. These devices are much more expensive than film badges but give a more accurate reading.

Film badges generally are good for up to a month, whereas other dosimeters can last up to three to four months depending on the type.

With technological changes being made, it is predicted that film badges will soon be a thing of the past due to a device known as the instadose dosimeter. These devices have a USB-compatible detector and can be plugged into any PC for precise radiation exposure readings at any time and also track accurate long-term exposure.

All radiology departments have safety signs prominently displayed in several areas of their facility that tell female patients to inform the radiology technologist or radiologist provider whether they are pregnant or if they possibly could be pregnant.

Many X-ray examinations, such as imaging the arms, legs, head, and chest, do not involve exposing your reproductive organs or unborn baby to the direct X-ray beam. In these cases, lead shielding can block any scattered radiation.

However, X-ray examinations of your abdominal area, such as the stomach, lower back, pelvis, and kidneys, are more of a concern because they expose the developing fetus to the direct X-ray beam. There has been disagreement about the exact amount of risk to the unborn child from the radiation from X-ray examinations, but it is believed to be small. Yet, even small risks should not be taken if they are unnecessary. Any pregnant patient must be informed to discuss the risks with her provider and make a decision based on whether the risk of having the X-ray is less of a danger than not having one at all.

X-Rays and Radiation Therapy

Radiologic studies are made by the use of X-rays (roentgen rays), which are high-energy electromagnetic radiation produced by the collision of a beam of electrons with a metal target in an X-ray tube.

Another type of radiology, known as therapeutic radiation or radiation therapy, is used in the treatment of cancer by preventing cellular reproduction.

Two main types of this therapy are teletherapy, which allows deep penetration for deep tumors and is performed on an outpatient basis,

and brachytherapy, by which radioactive implants are placed by the radiologist close to or into the cancerous tissue. Some of the most commonly ordered radiologic studies for which you might be responsible in scheduling and preparing patients will be addressed in this chapter.

Gallbladder Imaging

The gallbladder stores bile produced in the liver to break down fat in the digestive process. When the gallbladder malfunctions, the patient experiences abdominal discomfort (nausea) and pain. The cholecystogram enables the provider to diagnose the cause of the patient's distress. The oral cholecystogram is also referred to as a gallbladder series and a double-dose gallbladder. Refer to Figure 46-6, which shows gallstones present on the permanent film of the cholecystogram.

Prescribed Diet

In preparation for this study of the gallbladder, the patient must follow a prescribed diet and take prescribed medications (a contrast medium) to make the gallbladder visible on the X-ray digital images. Generally, the patient is advised to avoid drinking alcoholic and carbonated beverages the day before the exam because these drinks can produce flatus (gas). Unless otherwise specified by the provider, remind patients to take their regularly prescribed medications.

note

The abdominal ultrasound, an imaging technique, is also being used by some in place of the cholecystogram. Ultrasound, or sonography, is a process of using sound waves with a frequency of over 20,000 vibrations per second to produce images of the internal structures of the body. An image (sonogram) is produced when continuous sound waves are projected toward the desired area to measure and record the reflected image. The abdominal ultrasound includes the gallbladder, pancreas, liver, and other visceral organs. The preparation for the gallbladder or abdominal ultrasound is minimal in comparison with the cholecystogram. The preparation for the sonogram is much easier for the patient because it requires preparation only on the same day as the appointment. You should still advise patients regarding their diet and what to expect during the visit to the radiology facility. Sonograms as discussed in more detail later in the chapter are very useful in aiding in the diagnosis of gallstones, tumors, heart defects, and fetal abnormalities.

Upper GI Series - Barium Swallow

For an upper GI series study, the patient must drink the contrast medium during the examination while the radiologist observes the flow of the substance directly by means of a fluoroscope. The contrast medium is a milkshake-like drink that contains a substance called barium. It is usually flavored to increase palatability. Radiologic images are taken for a permanent record of the upper digestive tract. During the study, the patient is positioned so that different angles of the digestive organs can be seen. If needed, further enhancement of the different structures can be obtained by having air as well as barium in the stomach. This can be done by using crystals similar to Alka-Seltzer combined with a small amount of water to add air to the stomach. This is called double contrast. Next, a thickened barium mixture is ingested by mouth. Then to further examine the esophagus and duodenal bulb, a thin barium mixture is given to the patient. This allows for better images. Permanent radiographs are taken periodically during the procedure.

Lower GI Series - Barium Enema

Patients who are scheduled for a lower GI series study should follow the preparation listed in Table 46-1 very strictly. Stress the avoidance of milk and all dairy products for better visualization of the colon (Figure 46-7). Be sure to explain the importance of adequate preparation for these studies. Improper preparation could result in the need to repeat the tests.

In this examination, barium sulfate is used as the contrast medium. It is introduced into the colon by an enema tube, and the radiologist observes the flow into the lower bowel. After barium is introduced into the large intestine, several permanent radiographs are performed. Many providers order a barium enema with air-contrast. Most of the barium is emptied from the colon, and air is introduced. This procedure distends the barium-filled colon with air to make the structures more visible by fluoroscopy. This is called a double contrast study. This study is helpful in diagnosing diseases of the colon, tumors, and lesions.

The barium enema procedure generally takes several minutes and produces discomfort and some pain. Patients should be told to breathe through the mouth slowly and deeply to help relax the abdominal muscles. A strong urge to defecate is normal, and patients often cannot resist the urge. After several images have been taken and the study of the lower bowel is completed, the patient is allowed to use the toilet.

Intravenous Pyelogram

In studies of the genitourinary system, the intravenous pyelogram (IVP) requires the patient to prepare with laxatives, enemas, and fasting (see Table 46-2). The IVP consists of an intravenous injection of iodine, the contrast medium, to define the structures of the urinary system.

retrograde pyelogram

is a study of the urinary tract done by inserting a sterile catheter into the urinary meatus, through the bladder, and up into the ureters. The radiopaque contrast medium then flows upward into the kidneys. This diagnostic test is usually done in conjunction with cystoscopy. A voiding cystogram might be ordered in conjunction with an IVP; if so, the contrast medium is injected into the bladder by catheter, and no special patient preparation is needed.

KUB

is an X-ray of the patient's abdomen, sometimes termed flat plate of abdomen (Figure 46-8). This requires no patient preparation and is used in the diagnosis of urinary system diseases and disorders. It can also be useful in determining the position of an intrauterine device (IUD) or in locating foreign bodies in the digestive tract. In some cases, surgery is indicated to remove an object that might block the normal digestive flow, but many small objects are easily passed with solid foods, especially in young children whose internal structures are more flexible. The provider ultimately makes this decision in patient care.

Mammography

Mammography aids in the diagnosis of breast masses, some of which can be as small as 1 cm in size or less. Women who practice self-examinations regularly each month and find lumps in breast tissue early have a much better cure rate if a malignancy is found. Breast self-examination (see Chapter 35) and regular examinations by the provider should be strongly reinforced to female patients in addition to their scheduled mammography. The American Cancer Society recommends a baseline mammography at the age of 40 for all women and continuing yearly for as long as a woman is in good health.

Remind patients again of the importance of breast self-examinations on a continuing basis. The mammography is not a substitute for this important means of detection. If at any time a lump is found, patients should be advised to see the provider immediately for examination. The mammography procedure requires the patient to move into various positions so that different angles of the breast tissue may be imaged (Figure 46-9). The X-ray pictures are called mammograms. Compression of the breasts during this procedure requires less radiation to be used. It also allows a much clearer picture to be taken of the breast tissue. Patients are usually advised to wear slacks or a skirt for ease in preparation for the procedure (see Table 46-3) because the patient must undress to the waist for the examination. The only preparation required is for the patient to wash the chest and underarms and rinse and dry thoroughly. No deodorants, perfumes, or powders are to be used on the day of the mammography because the film on the skin from these substances could interfere with the radiograph.

another type

Another type of mammogram known as a 3D mammogram, or breast tomosynthesis, is an imaging test that combines multiple breast X-rays to create a three-dimensional picture of the breast. It views the images in 3D images or slices and helps to view things better when there is overlapping tissue. It also acquires images at multiple angles and assists in finding smaller cancers amongst those with very fibrous or dense breasts. Due to this technology it is a better screening choice to look for breast cancer in people who have no signs or symptoms. This technology has reduced the need for additional imaging and slightly increases the number of cancers detected during screening, however the 3D mammogram is not yet available at all medical facilities.

CT Scans

Rapid scanning of single-tissue planes is performed by a process that generates images of the tissue in slices about 1 cm thick. Figure 46-10 illustrates how different parts of the body are sectioned for the image. This method of radiology is called computed tomography (CT) scan or previously known as computerized transverse axial tomography (CTAT). These procedures can be performed in seconds and aid in diagnosis of diseases and disorders of the breast, brain, and other internal organs (Figure 46-11). Chapter 7 on the nervous system discusses more on CT scans and when they may be warranted.

Nuclear Medicine

Nuclear medicine uses radionuclides in the diagnosis and treatment of disease. Almost any organ of the body can be viewed and recorded by having the patient ingest, or be injected with, radioactive material. Uptake studies refer to procedures in which patients ingest a radioactive substance under careful supervision and return within 24 hours to have the amount of radioactive substance in a particular organ measured. For example, the radioactive thyroid uptake determines the function of the thyroid gland. Tumors of the thyroid can also be determined by this method. In female patients, pregnancy should be determined prior to the radioactive thyroid uptake because it is seriously damaging to the fetus, especially within the first trimester of pregnancy.

Sonographic Studies

is a technique by which internal structures are made visible by recording the reflections of ultrasonic sound waves directed into the tissues. These high-frequency sound waves are conducted through a transducer (a handheld instrument resembling a microphone). While the transducer is held against the body area to be tested, it sends sound waves through the skin to various organs. As the sound waves are sent back, the transducer picks them up and changes them into electrical energy. This energy is transmitted into an image on a monitor or printed out on paper in wavy lines. The picture formed on the screen represents a cross section of the organ. Photos of these images are taken for permanent records. The provider interprets these images to aid in the diagnosis and treatment of the patient. Ultrasound technology does not use radiation, so it is considered to be very safe. Sonograms are not useful in viewing the lungs because sound waves are not created by structures containing air.

abdominal ultrasound

ultrasound procedure is an accurate and painless diagnostic tool. It involves lying on an examination table for 45 to 60 minutes. A gel or lotion is used to produce better sound wave conduction and to allow the transducer to glide more easily across the skin. Ultrasonography is useful in examination of the abdominopelvic cavity to locate aneurysms of the aorta and other blood vessel abnormalities. The size and shape of internal organs can also be determined with ultrasound. It can be valuable in the identification of cysts and tumors of the eye and in the detection of pelvic masses and obstructions of the urinary tract.

Magnetic Resonance Imaging (MRI)

Another technique to view the structures inside the human body is called magnetic resonance imaging (MRI). This method allows providers to examine a particular area of the body without exposing the patient to X-rays or surgery. This noninvasive procedure, which can range from 30 to 60 minutes, requires the patient to lie on a padded table that is moved into a tunnel-like structure (Figure 46-12). Some patients experience claustrophobia when a closed MRI is used; this can be handled by counseling or the use of a sedative administered by a provider before the procedure is begun. Open MRIs are now available for claustrophobic or obese patients; however, the image quality may not be as clear or accurate as the traditional MRI.

Positron Emission Tomography (PET) Scan

is an imaging test that uses a radioactive substance called a tracer to look for disease in the body and show how organs and tissues are working. To allow the provider to see certain areas of concern more clearly, the tracer is given intravenously (IV), which allows it to travel through the patient's blood and collect in their organs and tissues. After the tracer is administered, the patient must remain close by, usually for about an hour. The patient lies on a narrow table that slides into a large tunnel-shaped scanner. The PET detects signals from the tracer, and a computer changes the signals into 3-D pictures and displays the images on the monitor for the provider to review (Figure 46-14B). The patient is instructed to lie still during the test, as too much movement can blur images and cause errors. The specific body part that is being scanned will determine how long the test may take. PET scans are usually performed on specific body structures such as the brain, breast, heart, and lung. To prepare for a PET scan, patients should be advised to follow the recommendations in Table 46-5.