X-Ray Studies



X-Ray Studies






OVERVIEW OF X-RAY STUDIES

X-ray studies, also known as radiographs, are used to examine soft and bony tissues of the body. X-rays are short-wavelength electromagnetic waves produced when fast-moving electrons collide with substances in their pathways. X-rays travel in straight lines at the speed of light (186,000 miles/second). When an x-ray beam passes through matter, some of its intensity is absorbed—the more dense the matter, the greater the degree of x-ray absorption. The composite image produced represents these varying degrees of tissue density in shades of black, white, and gray. Images may be captured on photographic film, displayed on a video screen, or recorded on digital media. The basic principle of radiography is that differences in density among various body structures produce images of varying light or dark intensity, much like the negative print of a photograph. Dense structures appear white, whereas air-filled areas are black.


USE OF CONTRAST AGENTS

Many radiographic techniques use the natural contrasts and varying densities that exist in body tissues representing air, water (in soft tissue), fat, and bone. The lungs and gastrointestinal (GI) tract normally contain air or gases. Other body structures are encased in a fatty envelope. Bone contains naturally occurring mineral salts. However, diagnosis of certain pathologic conditions requires visualization of details that cannot be revealed through plain x-rays. In these cases, details can be highlighted by the presence of contrast media in the area. These contrast substances can be administered through oral, rectal, or injection administration.

The ideal contrast agent should be relatively harmless (low toxicity, nonantigenic, nonallergenic, and inert), should not interfere with any physiologic functions, and should allow high and repeated dosing at a moderate cost. A contrast medium may be classified as either radiopaque (not permitting the transmission of x-rays) or radiolucent (permitting partial transmission of x-rays). The adverse pharmacodynamics of contrast media causes death in an estimated 1 of every 20,000 to 40,000 administrations. The most commonly used contrast agents are water-soluble noniodine agents for GI examinations and intravascular procedures. Ultimately, one must always be alert to the possibility of an adverse reaction to contrast media. Consequently, emergency supplies and equipment should be readily available when using these agents.

The following contrast agents are used routinely in x-ray studies:



  • Alimentary canal contrast agents



    • Water-soluble agents (e.g., Gastrografin, Gastroview, Hypaque sodium oral powder)


    • Water-insoluble agents (e.g., BaSO4, Polibar Plus, Esophotrast, Anatrast)


    • Gases (CO2 gas, gas-producing calcium citrate and magnesium citrate)


  • Injectable contrast agents



    • Nonionic iodinated contrast (low osmolar agents; e.g., Omnipaque, Optiray)


    • Ionic iodinated contrast (high osmolar agents; e.g., Renavest, Hypaque, Conray)


  • Specific-use agents



    • Bile agents (Cholebin, Conray)


    • Iodized oil contrast agents


ADVERSE REACTIONS TO CONTRAST AGENTS

All contrast agents have the potential for causing allergic reactions that can range from mild (e.g., nausea and vomiting) to severe anaphylaxis (e.g., cardiovascular collapse and central nervous system depression leading to death if untreated). Table 10.1 lists the range of possible adverse reactions to iodine contrast media. Reactions happen quickly and usually occur within minutes of administration of the contrast agent. Such reactions can occur in anyone.









TABLE 10.1 Signs, Symptoms, and Incidence of Reactions to Iodine Contrast Media



































































































Cardiovascular


Respiratory


Cutaneous


Gastrointestinal


Neurologic


Genitourinary


Pallor


Sneezing


Erythema


Nausea


Anxiety


Flank pain


Diaphoresis


Coughing


Feeling of warmth


Vomiting


Headache


Hematuria


Tachycardia


Rhinorrhea


Parotitis


Metallic taste


Dizziness


Oliguria


Bradycardia


Wheezing


Urticaria


Abdominal cramps


Agitation


Albuminuria


Palpitations


Acute asthma attack


Pruritus


Diarrhea


Vertigo


WBCs in blood


Arrhythmia


Laryngospasm


Pain at the injection site


Paralytic ileus


Slurred speech


Acute renal failure


Acute pulmonary edema


Cyanosis


Angioneurotic edema


@


Disorientation


Uterine cramps


Shock


Laryngeal edema


Swelling of eyes


@


Stupor


Urgency to urinate


Congestive heart failure


Apnea


@


@


Coma


Cardiac arrest


Respiratory arrest


@


@


Convulsions


@


Dyspnea


All Iodine Contrast Reactions


Incidence (%)


Minor reactions requiring no treatment: sensation of heat, nausea, vomiting, local urticaria, rash, dizziness, light-headedness, transient arrhythmia, pain at injection site, mild pallor, pruritus, facial swelling


1:20 (5)


Intermediate reactions that require treatment but no hospitalization and are not life-threatening: vomiting, extensive urticaria, bronchospasm, faintness, dyspnea, mild chest pain, headache, chills, and fever


1:100 (1)


Severe reactions that require hospitalization and are life-threatening: syncope, laryngeal and pulmonary edema, hypotension, convulsions, circulatory collapse, pulmonary edema, severe angina, myocardial infarction, cardiac arrhythmia, coma, respiratory arrest


1:2000 (0.05)


Cardiac arrest


1:6000 (0.017)


Death


1:40,000 (0.0025)




Clinical Considerations When Iodine Contrast Agents Are Used



  • Know the patient’s age and health status. Children and elderly people, especially those with medical problems, may be especially sensitive to contrast agents. This sensitivity may increase the chance for side effects.


  • The presence of other medical problems may increase the risk for side effects.



    • Individuals with asthma or hay fever are at a greater risk for having an allergic reaction to the contrast agent.


    • Diabetic patients have a greater risk for developing kidney problems.


    • Those with severe hypertension may experience a dangerous rise in blood pressure and tachycardia.


    • Patients with kidney and liver disease may experience exacerbation of their disease.


    • Individuals with multiple myeloma may develop severe kidney problems.


    • Those with overactive thyroid may experience a sudden increase in symptoms or thyroid storm.


    • Those with sickle cell disease may experience the formation of abnormal blood cells.


    • Patients using β blockers may have a higher risk for developing anaphylactoid reactions.


    • Patients with chronic obstructive pulmonary disease (COPD) have an increased risk for postinjection dyspnea.


  • Patients who are allergic to iodine contrast media must have this information documented in their health care records. The risk for subsequent reactions increases three to four times after the first reaction; however, subsequent reactions will not necessarily be more severe than the first. The patient must be made aware of the implications of the situation. Assess for and document allergies to iodine-containing substances (e.g., seafood, cabbage, kale, raw leafy vegetables, turnips, iodized salt). Also determine each person’s reaction to penicillin or skin test for allergies because these patients have a greater chance of having a reaction.


  • Check the patient’s fasting status before the x-ray procedure has begun. Except in an extreme emergency, iodine contrast media should never be administered intravenously sooner than 90 minutes after the patient has eaten. In most instances, the patient should fast the night before undergoing any x-ray procedure using an iodine contrast agent.


  • Death from an allergic reaction can occur if severe symptoms go untreated. Staff in attendance must be qualified to administer cardiopulmonary resuscitation should it be necessary. Emergency equipment and supplies must be readily available.


  • Promptly administer antihistamines per physician’s order if mild to moderate reactions to iodine contrast substances occur (see Table 10.1).


  • When coordinating x-ray testing with a contrast agent, keep in mind that studies using iodine and those using barium should be scheduled at different times.


  • Some physiologic change can be expected when an iodine contrast substance is injected, as during an intravenous pyelogram (IVP). Physiologic responses to iodine given intravenously include hypotension, tachycardia, and arrhythmias. For this reason, always check blood pressure, pulse, and respiration before and after these tests are performed.


  • If appropriate for the patient, encourage intake of large amounts of oral fluids after the test to promote frequent urination. This flushes the iodine out of the body.


  • Possible contraindications to the administration of iodine contrast substances include the following conditions:



    • Hypersensitivity to iodine


    • Sickle cell anemia (use may increase sickling effect)


    • Syphilis (use may lead to nephrotic syndrome)


    • Long-term steroid therapy (iodine substances may render part of the drug inactive)


    • Pheochromocytoma (may produce sudden, potentially fatal rise in blood pressure)


    • Hyperthyroidism


    • COPD



    • Multiple myeloma


    • Acute asthma


    • History of renal failure


    • Pregnancy


    • Diabetes mellitus


    • Severe dehydration


    • Congestive heart failure


    • Drug therapy known to be nephrotoxic (e.g., cisplatin)


  • Nonionic contrast agents tend to produce fewer side effects than do ionic materials.


  • Patients with renal failure may develop acidosis when iodine contrast is administered.



Clinical Considerations When Barium Contrast Is Used

There is always some risk when introducing barium sulfate or a similar contrast agent into the GI tract.



  • Barium radiography may interfere with many other abdominal examinations. A number of studies—including other x-rays, tests using iodine, ultrasound procedures, radioisotope studies, tomograms, computed tomography (CT), and proctoscopy—must be scheduled before or several days following barium studies. Consult with the radiography department for the proper sequencing of studies.


  • Increased consumption of fluids will help to clear the bowel of barium.


  • Elderly, inactive persons should be checked for stool impaction if they fail to defecate within a reasonable length of time after a barium procedure. The first sign of impaction in an elderly person is fainting.


  • Observe and record findings regarding stool color and consistency for at least 2 days to determine whether barium has been evacuated. Stools will be light in color until all barium has been expelled. Outpatients should be given a written reminder to inspect their stools for at least 2 days following barium administration.


  • If possible, avoid giving narcotics, especially codeine, when barium x-rays are ordered because these drugs can cause decreased bowel motility that can compound possible barium-associated constipation.




RISKS OF RADIATION

Exposure of the human body to radiation carries certain risks. The biologic effects of ionizing radiation change the chemical makeup of cells, causing cell damage and mutation and promoting carcinogenesis. However, not all forms of radiation are equal in the potential for causing damage, and often no perceptible or long-lasting damage occurs. As a general rule, the higher the dose, as determined by the “strength” of the radiation and the duration of the exposure, the greater the risk.

Deterministic effects, such as erythema, nausea, fatigue, depressed sperm count, and temporary sterility occur due to significant cell damage or death that occurs after a threshold amount of radiation has been exceeded. The severity of deterministic effects increases as the exposure dose increases. Stochastic effects, such as cancer, are associated with long term low-level exposure to radiation. Low doses of radiation received over a period of time can lead to radiation-induced malignancy and genetic effects and are of most concern in diagnostic radiology. Because the embryo is most radiosensitive during the first trimester of pregnancy, special precautions must be taken to prevent or minimize radiation exposure to the pregnant uterus (Tables 10.2, 10.3, 10.4 and 10.5).








TABLE 10.2 Principal Early Effects of Radiation Exposure on Humans and Approximate Threshold Dose

































Effect


Anatomic Site


Minimum Dose (Gray)


Death


Whole body


2


Hematologic depression


Whole body


0.25


Skin erythema


Small field


3


Epilation


Small field


3


Chromosome aberration


Whole body


0.05


Gonadal dysfunction


Local tissue


0.1


Reprinted with permission from Bushong SC: Radiologic Science for Technologists, 9th ed. Philadelphia, Elsevier Saunders, 2008.










TABLE 10.3 Relative Risk for Childhood Leukemia After Irradiation in Utero by Trimester




















Time of X-Ray Examination


Relative Risk


First trimester


8.3


Second trimester


1.5


Third trimester


1.4


Total


1.5


Reprinted with permission from Bushong SC: Radiologic Science for Technologists, 9th ed. St. Louis, CV Mosby, 2008.



Safety Measures

Certain precautions must be taken to protect patients, visitors, and staff from unnecessary exposure to radiation.


General Precautions



  • The patient’s medical records should be reviewed for previous radiological studies to minimize the potential for unwarranted repeat studies.


  • The size or area irradiated must be carefully adjusted so that no extra tissue than necessary is exposed to the x-irradiation. Collimators (shutters), cones, or lead diaphragms can ensure proper sizing and x-ray exposure area.


  • Fluoroscopy yields a higher dose than radiographs or CT studies. Significant dose reduction is achieved by employing pulsed digital fluoroscopy.


  • The gonads should be shielded in both female and male patients of childbearing age unless the examination involves the abdomen or gonad areas.


  • The primary x-ray beam should pass through layers of aluminum adequate to filter out low energy radiation while still providing detailed images.


  • Staff in the radiology department should wear lead aprons (and gloves if indicated) when not within a shielded booth during x-ray exposures. Patients should be shielded appropriately insofar as the procedure allows.


  • The x-ray tube housing should be checked periodically to detect radiation leakage and to indicate when repairs or adjustments are necessary.








TABLE 10.4 Summary of Effects After 10-rad in Utero








































Time of Exposure


Type of Response


Natural Occurrence


Radiation Response


0-2 wk


Spontaneous abortion


25%


0.1%


2-10 wk


Congenital abnormalities


5%


1%


2-15 wk


Mental retardation


6%


0.5%


0-9 mo


Malignant disease


8/10,000


12/10,000


0-9 mo


Impaired growth and development


1%


Nil


0-9 mo


Genetic mutations


10%


Nil


Reprinted with permission from Bushong SC: Radiologic Science for Technologists, 9th ed. St. Louis, CV Mosby, 2008.










TABLE 10.5 Representative Radiation Quantities From Various Diagnostic X-Ray Procedures

































































Examination


Technique (kVp/mAs)


Entrance Skin Exposure (mrad)


Mean Marrow Dose (mrad)


Gonad Dose (mrad)


Skull


76/50


200


10


<1


Chest


110/3


10


2


<1


Cervical spine


70/40


150


10


<1


Lumbar spine


72/60


300


60


225


Abdomen


74/60


400


30


125


Pelvis


70/50


150


20


150


Extremity


60/5


50


2


<1


CT (head)


125/300


4000


20


50


CT (pelvis)


124/400


2000


50


2000


Reprinted with permission from Bushong SC: Radiologic Science for Technologists, 9th ed. St. Louis, CV Mosby, 2008.



Precautions to Be Used With Pregnant Patients



  • Women of childbearing age who could possibly be in the first trimester of pregnancy should not have x-ray examinations involving the trunk or pelvic regions. A brief menstrual history should be obtained to determine whether a possible pregnancy exists. If pregnancy is possible, a pregnancy test should be done before proceeding with x-ray examination.


  • All pregnant patients, regardless of trimester, should avoid radiographic, fluoroscopic, and serial film studies of the pelvic region, lumbar spine, and abdomen if at all possible.


  • Should x-ray studies be necessary for obstetric regions, repeat images should be avoided.


  • If x-ray studies of nonreproductive tissues are necessary (e.g., dental x-rays), the abdominal and pelvic region should be shielded with a lead apron.


Responsibilities in Ordering, Scheduling, and Sequencing X-Ray Examinations

Correct and complete information should be entered into the computer or on the x-ray requisition. An appropriate order will include the name of the exam, the ordering physician’s name, and the clinical indication for the exam. Explain to the patient the purpose and procedure of the x-ray examination. Written patient instructions may be helpful.

When a complete genitourinary (GU) and gastrointestinal (GI) workup is scheduled, the sequence of x-ray procedures should follow a definite order:



  • First day: intravenous pyelogram (IVP) and barium enema


  • Second day (or subsequent day): upper GI (UGI) series

Barium studies should be scheduled after the following procedures:



  • Abdominal or pelvic ultrasound examination


  • Lumbar-sacral spine x-rays


  • Pelvic x-rays


  • Hysterosalpingogram


  • IVP

As a general rule, examinations that do not require contrast should precede examinations that do require contrast. All examinations that require contrast agents should be completed before those that require barium contrast. In addition, examinations that require contrast agents must precede nuclear medicine examinations that require radioactive iodine administrations (e.g., thyroid scans). Other x-ray
examinations that do not require preparation can be performed at any time. Such examinations include the following:



  • X-rays of the head, spine, and extremities


  • Noncontrast abdominal x-rays (e.g., kidney, ureters, bladder [KUB], abdomen series)


  • Mammograms



PLAIN CONVENTIONAL X-RAYS/RADIOGRAPHY


Chest X-Ray

The chest x-ray is the most frequently requested radiograph. It is used to diagnose cancer, tuberculosis and other pulmonary diseases, and disorders of the mediastinum and bony thorax. The chest x-ray provides a record of the sequential progress or development of a disease. It can also provide valuable information about the condition of the heart, lungs, GI tract, and thyroid gland. A chest x-ray must be done after the insertion of chest tubes or subclavian catheters to determine their anatomic position as well as to detect possible pneumothorax related to the insertion procedure. A postbronchoscopy chest x-ray is done to ensure there is no pneumothorax following a biopsy.


Reference Values


Normal

Normal-appearing and normally positioned chest, bony thorax (all bones present, aligned, symmetrical, and normally shaped), soft tissues, mediastinum, lungs, pleura, heart, and aortic arch




Interfering Factors

An important consideration in interpreting chest radiographs is to ask whether the film was taken in full inspiration. Certain disease states do not allow the patient to inhale fully. The following conditions may alter the patient’s ability to breathe properly and should be considered when evaluating radiographs:



  • Obesity


  • Severe pain


  • Congestive heart failure


  • Scarring of lung tissues



Mammography (Breast X-Ray)

Soft tissue mammography visualizes the breast to detect small abnormalities that could suggest a malignancy or benign disease. Its primary use is to screen for and discover cancers that escape detection by other means such as palpation. Typically, lesions <1 cm cannot be detected by routine clinical or self-examinations. Although the average breast cancer has probably been present for some time before it reaches the clinically palpable 1-cm size, the prognosis for cure is excellent if detected in this preclinical or presymptomatic phase.

The low-energy x-ray beam used for this procedure is applied to a tightly restricted area and consequently does not produce significant radiation exposure to other areas of the body. Therefore, it is quite acceptable from a radiation safety standpoint to recommend routine screenings. Diagnosis by mammography is based on the radiographic appearance of gross anatomic structures. Benign lesions tend to push breast tissue aside as they expand, whereas malignant lesions may invade surrounding breast tissue. Although false-negative and false-positive readings can occur, mammography is highly accurate.

Most breast lumps are not malignant; many are benign cysts. For women >40 years of age, the benefits of using low-dose mammography to find early, curable cancers outweigh possible risks from radiation exposure (Table 10.6).

The American College of Radiology (ACR) accredits mammography machines, and the U.S. Food and Drug Administration (FDA) certifies mammographic facilities. To earn accreditation, mammograms must be performed by specially trained and credentialed radiographers, and the resulting images must be interpreted by radiologists who meet criteria for continuing education in mammography. Additionally, the ACR has stringent standards for equipment, image quality, and radiation dose. Health insurers, including Medicare, require mammographic services to be performed at an accredited institution. The FDA has approved certain digital systems to record breast anatomy electronically— that is, on a computer, rather than on film.


Indications for Mammography



  • To detect clinically nonpalpable breast cancer in women >40 years of age, younger women at high risk, or those with a history of breast cancer


  • When signs and symptoms of breast cancer are present



    • Skin changes (e.g., “orange peel” skin associated with inflammatory-type cancer)


    • Nipple or skin retraction


    • Nipple discharge or erosion


  • Breast pain








    TABLE 10.6 Likelihood of Breast Cancer




















    Age (yr)


    Odds


    30-39


    1 in 233


    40-49


    1 in 69


    50-59


    1 in 38


    60-69


    1 in 27


    Source: National Cancer Institute, 2006.




  • “Lumpy” breast; multiple masses or nodules


  • Pendulous breasts that is difficult to examine


  • Survey of opposite breast after mastectomy


  • Patients at risk for having breast cancer (e.g., family history of breast cancer)


  • Adenocarcinoma of undetermined origin


  • Previous breast biopsy


  • Tissue samples removed from the breast may be imaged using detailed mammography techniques


  • Follow-up studies for questionable mammographic images



Reference Values


Normal

Essentially normal breast tissue: calcification, if present, should be evenly distributed; normal ducts with gradual narrowing ductal system branches





Orthopedic X-Ray: Bones, Joints, and Supporting Structures

Orthopedic radiography examines a particular bone, group of bones, or joint. The bony or osseous system presents five functions of radiologic significance: structure support of the body, locomotion,
red marrow storage, calcium storage, and protection of underlying soft tissue and organ structures. Orthopedic radiography is performed on the following structures:



  • The extremities (e.g., hand, wrist, shoulder, foot, knee, hip)


  • The bony thorax (e.g., ribs, sternum, clavicle)


  • The spine (e.g. cervical, thoracic, lumbar, sacrum, coccyx)


  • The head and skull (e.g. facial bones, mastoids, sinuses)

Optimal results from orthopedic x-ray examinations depend on proper immobilization of the area being studied. To produce a thorough image of the body part, at least two projections are required. These are taken at angles of 90° to one another (e.g. anteroposterior and lateral views).

To examine more complex structures such as the spine and skull, or to examine a structure in greater detail, several projections from various angles may be required.


Reference Values


Normal

Normal osseous (bone) and supporting tissue structures




Interfering Factors

Images of the lumbosacral spine, coccyx, or pelvis must be completed before barium studies because residual barium may interfere with proper visualization. Jewelry and accessories, heavy clothing, metallic objects, zippers, buttons, snaps, cables, and monitoring equipment and supplies can interfere with optimal views and need to be removed before the examination.

Jun 11, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on X-Ray Studies
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