assisting with diagnostic imaging

Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc.

Assisting with Diagnostic Imaging

Chapter 49

Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 2

Radiography

Process of recording of x-ray images or radiographs.

X-rays are produced in a vacuum tube, creating a radiation field that can penetrate most substances and form an image on film.

Radiopaque—substance that is not easily penetrated by radiation and so appears light on the radiograph (bone).

Radiolucent—substance that is easily penetrated (air, soft tissue) and so appears dark on the radiograph.

Latent image—invisible changes in exposed film that become visible when film is processed.


X-Ray


Chest X-Ray


Radiographic Equipment

Principal components of the x-ray machine are:– X-ray tube, which is the source of radiation in its barrel-shaped

protective housing

– Collimator mounted beneath the housing, which varies the radiation field size

– Tube support, suspended from ceiling or attached to tube stand, which provides support and mobility for the tube

– Adjustable radiographic table

– Bucky, which moves grid device to prevent scatter radiation

– Within the grid device is the cassette tray, which holds the x-ray film

– Control console, in the control booth, where operator selects exposure settings and takes the x-ray film


Radiographic Equipment


Image Receptor Systems

Cassette—holds film during the x-ray examination Rigid structure protects film from light and houses

intensifying screens

Intensifying screens—one front and back of the film

Coated with phosphors—to give off light when exposed to x-rays

Used to reduce amount of radiation exposure needed to get x-ray image

Keep clean and avoid touching to prevent damage and x-ray artifacts

Film—sensitive to light emitted by intensifying screens


Handling Cassettes

Cassettes are unloaded and reloaded in the darkroom under safelight illumination only.

Ensure that the door is locked, your hands are clean and dry, and the film is not creased, bent, or scraped in loading and unloading.

Reload the cassette with only one fresh film, and latch securely.

Keep the loading bench clean to prevent dirt from getting into the cassette.


Film Identification

Record the identity of the patient in the image and the date and location of the examination. Serious errors in diagnosis and treatment might occur if films are not correctly identified.

Type identification information on a card that is inserted into a photographic printer in the darkroom. The printer stamps the information on the film after it is removed from the cassette and before it is processed.


Film Identification


Anatomic Locations and Positions Anatomic position

Anterior

Cephalic

Caudal

Distal

External

Inferior

Internal

Medial

Lateral

Palmar

Plantar

Posterior

Proximal

Superior

Positions

– Prone

– Dorsal recumbent

– Lateral recumbent

– Ventral recumbent

– Supine

– Upright


Body Planes

Sagittal plane – Midsagittal plane

Coronal or frontal plane– Midcoronal plane

Transverse plane


Radiographic Projections

Indicates the position of the body part in relation to the film and x-ray tube

Anteroposterior (AP)

Posteroanterior (PA)



Lateral projection—sagittal plane of the body is parallel to the film



Oblique projection—body rotated so projection is neither frontal nor lateral


Fluoroscopy

Enables the radiologist to view x-ray images in motion.

Most fluoroscopy units can also take “spot films.” – x-ray films taken during the procedure that record the

fluoroscope image

Typical fluoroscopic studies are UGI series and LGI series.


X-Ray Studies Using Contrast Media Contrast media—radiopaque substances (barium

sulfate and iodine compounds) that enhance visualization of soft tissues

Used in the following studies:– UGI series (barium swallow)

– LGI series (barium enema)

– Intravenous urogram—IVU (intravenous water-soluble iodine)

– Arthrogram (iodine compound)

– Myelography (iodine into spinal canal)

– Angiography—arteriogram or venogram (iodine into vessel) Angioplasty Embolization


Computed Tomography (CT)

Computerized x-ray imaging that provides axial (slices of views in the transverse plane) and three-dimensional scans.

Noninvasive but may cause patient apprehension.

Patient lies on a movable table with a circular gantry that rotates the x-ray tube around the patient to get images.

Contrast medium improves imaging.

Used to visualize the brain, abdomen, spine, joints, chest, blood vessels, and so on.


Computed Tomography (CT)


Magnetic Resonance Imaging (MRI) Noninvasive procedure that does not use

radiation. Uses a strong magnetic field and radiofrequency

pulses to create computer images of bones and soft tissue in multiple planes.– Excellent imaging of nervous system– Soft tissue of joints– Hazardous for patients with artificial heart valves,

pacemakers, IUDs, metal fragments in skin, orthopedic pins, and so on

Patient lies on table, which moves into gantry (5 to 8 feet long) that holds the magnet and radiofrequency coil.

Open gantry designs are better for large or claustrophobic patients but do not provide high-quality images.


Nuclear Medicine and Sonography Nuclear medicine studies demonstrate the function of

organs and tissues by mapping the radiation after radioactive tracers have been ingested or injected.– Do not provide clear anatomic images but give information about

tissue function

– Abnormal tissues show the tracer being metabolized at a different rate

– Examples: thallium scan; bone, brain, thyroid scans

Sonography (diagnostic ultrasound) demonstrates soft tissues by using high-frequency sound waves.– Transducer sends high-frequency sound waves through tissue

– Moved over surface of body, and real-time image is examined

– Used for fetal, gallbladder, breast, heart imaging


Scheduling Diagnostic Imaging Procedures

Multiple diagnostic procedures must be scheduled in a sequence so they do not interfere with one another.

Recommended sequence order:

1. X-ray studies not requiring contrast media and those using iodine uptake

2. Fiberoptic studies before those using barium contrast (colonoscopy before LGI series)

3. X-rays of urinary tract

4. X-rays of biliary system

5. LGI series (barium enema)

6. UGI series (barium swallow)


Patient Preparation for Radiography

Procedure explained to patient, and consent form signed.

Preparation for chest x-ray examination: undress to the waist and put on gown; remove all metal objects. Patient stands at an upright film holder.

UGI series—patient must fast; no water, chewing gum, or smoking for at least 8 hours before examination.

LGI series—extensive bowel cleansing; low-residue or clear liquid diet, forced fluids, cathartics, suppository, and low-volume enema.


Radiation Exposure Most cellular effects are short-lived.

Sometimes DNA changes occur because of cellular damage.

Cell sensitivity to radiation exposure is dependent on:– age

– differentiation

– metabolic rate

– mitotic rate

Sensitive cells include blood and bone marrow; skin; mucosal lining of mouth, nose, and GI tract; thyroid gland; breast; fetal tissue. Cells in children are sensitive. Nerve and bone cells are less sensitive.


Effects of Radiation Exposure

Somatic—occur to the body of the person exposed– Low-dose exposure causes long-term effects

– Causes increased risk of: Cataracts Carcinogenesis—skin, thyroid, breast, leukemia Shortened life span During pregnancy—abortions, congenital defects,

genetic abnormalities

Genetic—mutations in the hereditary material of reproductive cells– May be passed on to future generations


Radiation Protection Personnel Safety

– Scatter radiation present during x-ray examination

– Only time hazard exists is during x-ray examination

– Wear lead apron, gloves, and so on

– Avoid direct exposure from the primary x-ray beam

– Stand well behind protective lead barrier of control booth

– Close x-ray room door during exposure

– Exposure increases when assisting with fluoroscopy & using mobile x-ray units

Dose decreased when time of exposure is minimized Increase distance between you and x-ray machine Use lead shields—goggles, thyroid shields, and so on


Personnel Monitoring

Dosimeter—badge worn that monitors radiation exposure– Wear around collar and outside of lead apron.

– OSL type more accurate.


Personnel Monitoring (cont’d)


Personnel Monitoring

– Monitoring laboratories provide the badges, process and report results, and keep permanent records of radiation exposure for each person.

– Monthly monitoring recommended for fluoroscopy workers; quarterly if control booth protection consistently used.

– Employers required to provide radiation exposure history to all employees.

– Effective Dose Equivalent (EDE) calculates upper limit of safe occupational exposure (5 rem/year).


Patient Protection

Avoid errors.

Avoid repeat exposures because of careless errors.

Collimate.

Use highest kilovolts (kVp) of energy and lowest milliamperage (mA) to produce best picture.

Use at least 40 inches of source-to-image distance (SID).

Use fastest films and screens to get high-quality image.

Provide shields.

Warn all women of childbearing age of potential risks.

assisting with diagnostic imaging

Documents