Imaging Highlights

Imaging Techniques

• Used to visualize and examine internal body structures

The three most common:

1.Radiography (x-ray)

2.Computed Tomography (CT)

3.Magnetic resonance imaging (MRI)

X-ray

• Many imaging techniques use x-ray which is invisible, odorless, and can’t be felt.

• Used to radiate cancer- yet overexposure can cause death.

• (See x-ray PP Google docs)

X-ray

• Image of hard-tissue. Internal structures created by the exposure of sensitized film to x-radiation. Resulting film known as an x-ray or radiograph

• Radiograph made up of shades of gray• Radiopaque hard tissues, such as bone and tooth

enamel, do not permit x-rays to pass through and appear white or light gray on radiograph

• Radiolucent air and soft tissues do permit x-rays to pass through, and appear as shades of gray to black on the radiograph

Positioning

• Describes the body placement and the part of the body closest to the film.

• Example: left lateral position, the left side of the body is placed nearest the film

• http://www.rtstudents.com/radiology-positions.htm

• Hand out

PROJECTION

• Refers to the path the beam takes through partAnteroposterior projection

(AP)• Beam enters the front surface

and exits the back surface of the part

Posteroanterior projection (PA)• Beam enters the back and

exits the front of the part

AP projection in supine position

PA projection in prone position

Lateral Projections• Normally the

positioning terminology is used rather than projection– torso and head

• Right to left lateral projection• Left to right lateral projection

– extremities• Mediolateral projection• Lateromedial projection

L lateral erect positionR to L lateral projection

Oblique Projections

• Normally the positioning terminology is used– example

RPO position = right anterior to right posterior projection (oblique AP)

Radiographpy vs Nuclear Medicine

Radiography – source of radiation is external. Gamma rays pass through body and form radiograph

Nuclear Medicine – source of radiation is radiopharmaceutical taken internally. X-rays pass out of body and form scan image.

Ionization• Ability of x-rays to

change substances thru which they pass

• Used to make radiographs and treat cancer

• May cause cell damage and even death

Nuclear Scan• Radioactive isotope

tagged to substance absorbed by specific tissue and injected into the blood

• Shows gross fx of organ

• Good for images of tumors or lesions

Common Scans• Bone – fractures, tumors,

inflammation, bone growth

• Brain – tumors, blood flow

• Liver – cirrhosis, hepatitis, tumors, cysts, abscesses

• Lung – blood clots, tumors

• Thyroid – function, tumors

• heart

Radioimmunoassay

• Mix blood with radioactive substance to determine specific blood protein concentrations

• Find antibodies and antigens (titers)

Radiation Therapy• Treatment of CA

with external radiation

• Stereotactic – focusing multiple beams at the same spot

Teletherapy vs Bradytherapy

Bradytherapy – radiation source is internal

Teletherapy – radiation source is external

Tomography• Imaging method that

produces tomes (cross sections) of body along any plane

• Shows structure

• Good for images of tumors- especially when contrast medium used

Mammography

• X-ray examination of the internal breast tissue

• Helps in diagnosing breast abnormalities

PET Scan

• Positron Emission Tomography

• Radioactive isotope is tagged to substance used by specific cells and injected into the blood

• Best way to show metabolism or specific functional areas, good for determining how well an organ is functioning, especially the brain and heart

CAT vs PET• CAT – 2D tomes are

reconstructed to show 3D images of structure

• PET – radiopharmecuticals are used to give 2D and 3D images of function

Magnetic Resonance Imaging

• Image produced when body is surrounded by powerful electromagnetic waves

• Best way to show structure in minute detail

Magnetic Resonance Imaging

• Gives good image of soft tissues

• Cannot use if metal is implanted in body

• Good for images of any type of structural damage

Sonogram• sound waves

bounced off organs produces image of deep structures

• Only imaging procedure safe for fetus

• Also used for thyroid, abdominal masses, inner heart structure, blood vessels

Contrast Medium• Radio-opaque substance used to make

hard-to-see structure show up on image

• Used in CAT scans and fluoroscopy

Radio-opaque vs Radiolucent

Radio-opaque -Block x-raysShows up as light color

Radiolucent –Passes x-rays throughShows up as dark color

FluoroscopyVisualization of moving structures as contrast medium moves through body

Used with radio-opaque substances

GI series, arteriograms

Cineradiography

• Filming images on fluroscope screen with a video camera

How to process an imaging request

• Check for allergies- if allergic to seafood the pt. might be allergic to iodine found in many radio-opaque dyes

• Age- below 12 may need extra help or sedation• Weight- older MRI machines limited to max 300lb• Pacemaker- may be damaged by exposure to

MRI• Metal items in body- artificial joints or internal

fixation devices may contain metal that will heat up or be dislodged by the test

Image quality

• Target structures must be visualized

• Proper view must be shown

• Image must be clear

***The imager must make sure the image is of good quality before releasing the patient from the unit****

Unit Preparation

• Safety- equipment and safety monitors working properly

• Supplies- everything needed on hand

Commonly Visualized structuresradiographic and fluoroscopic

• Chest x-ray (CXR)- heart lungs ribs

• Upper GI series- esophagus, stomach, small intestine

• Lower GI - colon

Patient Safety

• Check for previous imaging to prevent repeat exposure

• Give instructions and check for understanding

• Position correctly to prevent repeat

• Use gonadal shielding on children and patients of reproductive age

• Ask all women for LMP

Worker safety• Reduce exposure time• Stay as far from radiation source as possible and

position body at right angle• Use shielding appropriate for the test- lead apron,

lead gloves• Wear appropriate radiation detection device

(dosimeter on front of body

1.Film badge- least accurate, good for 1 month

2.Thermoluminescent dosimeter- good for 3 months

3.Pocket ionizing chamber- most accurate

Workplace safety

• Geiger-Muller detector- detects quantity of radiation in the workplace

• Victoreen condenser R-meter- used to calibrate radiography equipment

Thermogram

• Media – infrared camera captures surface body heat

• Newer forms relate metabolic activity (function) to heat given off