Exam IV: Radiology Flashcards Preview

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Flashcards in Exam IV: Radiology Deck (58)
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1

Wilhelm Conrad Roentgen

Discovered X-rays
November 8th, 1895
Received the First Nobel Prize in Physics in 1901

2

Early X-Ray

Light-tight cathode tube produced fluorescence of nearby chemical-coated cardboard screen
Roentgen realized that cathode ray tube emitted “something” new
“Something” passed through objects opaque to light, was invisible, and caused fluorescence
Roentgen saw bones in his hand on cardboard screen
He decided to call it X-ray for “unknown ray”
A form of electromagnetic energy with a very short wavelength of .5 to .06 Angstrom
Short wavelength allows x-rays to penetrate matter, unlike light rays
Smaller wavelength = more energy

3

Characteristics of X-Rays

X-rays have short wavelength, travel at speed of light, in straight path and cause ionization of matter
X-rays can be absorbed, pass through, or be scattered by tissue
Shades of gray are produced in relation to the amount of x-rays which are absorbed by the object being imaged and the remaining x-rays which reach the imaging medium

4

Production of X-Rays

X-ray tube consists of an evacuated glass tube with cathode and anode terminals
Cathode tungsten filament is heated to incandescence, giving off electrons
Electrons bombard positively charged anode target, and x-rays are emitted

5

Ionizing Radiation

Ionizing radiation is radiation that has enough energy to remove electrons from atoms or molecules.
Forms of ionizing radiation include X-Rays, Gamma Rays, Alpha particles, Beta particles and Neutrons.
X-Rays, nuclear medicine studies, fluoroscopy and CT involve ionizing radiation

6

Radiographs

Photographic effect of x-rays produces film image, a representation of variable tissue densities and contours
Scattered x-rays darken film and degrade image
Radio-opaque tissue is denser, absorbs more x-rays, and appears as whiter image on film
Radiolucent tissue is less dense, absorbs less x-rays and appears as darker image on film
We don’t see x-rays, we see the radiograph
Radio-opaque = basically a denser material, soaks up the energy and leaves the film white

7

Principles of Density

A black film would be overexposed
A white film would be underexposed
Look for different densities in any film you are reading be it plain film or CT. For example you are reading a film of the pelvis, the pelvic girdle would white, pelvic organs shades of gray, bowel gas black

8

Magnification Concept

The image “spreads” or magnifies causing detail to be lost
When the object creating the image is closer = more detail and closer to actual size

9

Film Cassette

Patients cannot hold still long enough to obtain an image from x-rays alone
Cassette contains fluorescent screens which glow when activated by x-rays and this light is used to expose the film
Less radiation and exposure times are needed
The “grid” cuts down on scatter effect on film – like a lens

Can’t use glass, so need to use lead grid “honeycomb” for x-rays to go through to focus the beam and gets rid of scattering to make a clear image
The image is taken much quicker than when it was first developed, which also clears up the image

10

Plain Films

What we study are radiographs, images, or films, not X-rays or electromagnetic waves
The patient is placed between the x-ray tube and the film cassette.
The body part closest to the cassette is magnified the least and has the sharpest boundaries

11

Positioning for Imaging

PA chest film, the x-rays pass posterior to anterior body part studied is closest to film, less magnification
Lateral films are named for part closest to the film

Posterior to anterior position: for heart and lung clear imagine (PA x-ray)
Anterior to posterior position: for spine and muscles around it (AP x-ray)
*describes the way the rays are going
Left side: for best heart image or left lung
Right side: for best right side tissues

12

Portable X-Ray Studies

Portable x-ray machine
Chest X-ray must be Anterior posterior (AP)
Images are never as good as in department
Limited information- not as precise
More expensive – but don’t tell the patient that
Only reason for x ray in the room: if the patient cannot leave the room
Since AP x ray, can’t see heart and lungs because it is directed towards spine and musculature

13

Chest X-Ray

PA (posterior to anterior)
1. Radiolucent lungs
2. Radio-opaque bony thorax
3. Intermediate density mediastinum with important contours

14

Abdominal Film

KUB- kidneys, ureter, bladder
1. Radiolucent bowel gas pattern
2. Radiodense spine and pelvis or calcifications
3. Intermediate density soft tissue viscera with important contours

15

Digital Radiography

No actual “film” is required
X-rays strike a phosphor plate and a photomultiplier intensifies the image.
Data is recorded in a digital format, just like digital photography
Resulting image can be viewed on a monitor screen or can be transferred to radiographic film
Digital allows to send it anywhere, make many copies, and easier to store

16

Advantages of Digital Radiography

Digital images require less storage space
Multiple monitors can look at the same image at the same time
Much more difficult to “lose the films”
Images can be transmitted electronically and copies are easily generated.
The view that is generated can be altered by the computer (Contrast and Brightness)

17

Disadvantages of Digital Radiography

Hospitals already have fully functional film based imaging equipment and film library
The new equipment is expensive – you cannot read diagnostic studies on a simple computer monitor
Images may not quite as sharp and precise

18

Fluoroscopy

Common radiological technique that allows real-time visualization
A continuous beam of x-rays pass through the patient to form an image on a fluorescing screen which is amplified electronically and viewed on a television screen
Common procedures include: Upper GI, Lower GI (barium enema) and many interventional procedures

X-ray tube is below patient
Film changer and image intensifier above patient
Table can be tilted, patient can be rolled side to side

19

Contrast Media

Any substance that is radio-opaque will absorb x-rays and show up as white in radiographs
Different types of contrast material can be given orally, rectally, intravenously or injected into a specific space
All forms of contrast have advantages and disadvantages

20

GI Contrast

Outlines structures in the GI tract
Can be administered from either end, depending on what you want to see
Barium sulfate or iodinated water soluble
Goes into the GI tract, stays in the GI tract – is not absorbed

21

Barium Sulfate

Type of GI contrast

Barium sulfate
Extremely dense, provides good images
Slow to be excreted - sticky stuff
Contra-indicated where spillage into a body cavity is possible
Must be dilute for CT scan – Redi Cat®
Tastes terrible

22

Iodine Based Water Soluble Contrast

Type of GI contrast

Iodine based water soluble contrast
OK if spilled into peritoneum or mediastinum
Somewhat less dense, therefore gives slightly less detail
Toxic to lung tissue, must be used carefully if there is a risk of aspiration
Tastes terrible

23

IV Contrast

Allows precise imaging of blood vessels or urinary tract
Shows shape of vessels and any extravasation
Iodinated compounds are most common, carbon dioxide can be used for angiography
Materials containing Iodine are toxic to the kidneys
Goes into the bloodstream, excreted in urine, does not transfer to any other location
No taste

Shows leaks (extravasation) and spaces of urinary tract
Why do we choose CO2? Most other gases are dangerous (N for example can prevent heart from beating), CO2 is instantly removed from the body (O2 is slower) because attaches to Hb and taken out of circulation

Examples: Renal Artery Arteriogram and Intravenous Pyelogram

24

Digital Subtraction Angiography

Initial image to identify surrounding structures
Repeat images with IV contrast have static portions of image removed
Clarifies images of structures being studied
Characteristic appearance

Skull is very dense, so getting a clear picture of arteries using x rays= hard
No contrast photo than photo with contrast and the computer subtracts the first image from the second one

25

Ultrasound (US)

Narrow beam of high frequency sound waves is produced by a vibrating crystal
Sound waves are directed into the body and reflected back dependent upon tissues differing acoustic impedance
The crystal in the transducer acts as a transmitter and a receiver
Crystal that gives off and receives wanes and get photo from it
Acoustic impedance: how sound “bounces”
The tech’s hand is controlling the transmitter and receiver (acts as both)

26

Image Formation: US

The transducer records echoes reflected back when the sound wave strikes an interface between two tissues that have different acoustic properties
This data is then analyzed by a computer to create a digital image
Ultrasound can displayed as static images or as multiple video images that permit movement in real time
US works well with fluid filled cavities

27

Echogenic Ultrasound

Images are based on internal echoes due to acoustic interfaces
May be described as hypoechoic, isoechoic, or hyperechoic
Solid tissue, tumors, fat or fibrous tissue show as light areas

Anechoic – echo-free due to absence of acoustic interfaces; no sound interfaces
Sonolucent - cyst or fluid-filled viscus shows as a dark area
Acoustic Shadowing: Echogenic objects have differing amounts of acoustic shadowing – This may be described as “characteristic”

28

Advantages of US

No ionizing radiation – freely used in obstetrics, pediatrics, and multiple evaluations
Safe - no evidence as yet to indicate adverse effect on human tissue at intensity level currently used
Multi-planar imaging – axial, sagittal, oblique planes
Ability to differentiate cystic, solid, and complex tissue
Cost-effective (cheap)
Easily portable
“Real-time” analysis and procedures

29

Disadvantages of US

Air and bone produce extreme acoustic impedance; most sound is reflected prohibiting sound penetration
Images not as clear as CT or MRI
Very operator dependent- clarity of objects/objects' views

30

Ultrasound Guided Biopsy

Ultrasound-guided biopsy of a breast mass for example
Shows the needle entering, inserting, and exiting the tissue