What is Imaging and Radiation?
#radioactive#overplayed
The BASICS
 Anatomic imagine began at the turn of the
century with Roentgen's discover of x-rays in
1896
 Advancements have allowed physicians (scientists)
to look inside the body without the trauma and
risk of explanatory surgery.
Modern Techniques
 Traditional x-rays
 Computer Tomography (CT)
 Magnetic Resonance Imaging (MRI)
 Dynamic Spatial Reconstruction (DSR)
 Digital Subtraction Angiography (DSA)
 Positron Emission Tomography (PET)
optical Coherent Tomography (OCT)
 Echo-planar MIR/Ultrasound
Radiation Basics
 Radiation is energy that comes from a source and travels through
any kind of material and through space
 Ionizing Radiation produces charged particles (Ions)
 Ionizing radiation is produce by unstable atoms; unstable atoms are
said to be Radioactive
 To reach stability, these atoms give off energy; called Radiation
Types of Radiation
 One typically encounters one of Three types: Alpha, Beta and
Gamma Radiation
 Neutron radiation is also encountered in nuclear plants, high
altitude flights and emitted from industrial radioactive
sources
Alpha Radiation
 Heavy, very short range particle and actually an ejected
helium nuclease
 Characteristic;
- Radiation Not able to penetrate human skin or clothing
- Emitted materials can be harmful to humans
- Very short distance; few inches
Beta Radiation
 Light, short range particle, and ejected electron
 Characteristics:
- May travel several feet in air and moderately penetrating
- Can penetrate human skin to germinal layer
- May be harmful if deposited internally
- Clothing provides some protection
Gamma Radiation
 Or X-Rays, very long range, penetrating electromagnetic radiation
 Characteristics:
- Able to travel many feet in air and many inches in human tissue
- Sealed radioactive sources that emit gamma radiation and an
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external hazard to humans
Visible light, radio waves and ultraviolet light
Electromagnetic radiations differ only in about of energy they
have
Gamma/X-rays have most energetic
Clothing provides little shielding
Radiography or X-Rays
Radiography
 Radiography, known by most as X-Ray, uses electromagnetic
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radiation to make images of your bones, teeth, and internal
organs
X-rays allow DRs to take pictures inside the body
They Type of X-Ray depends on what part of the body needs
examining and the purpose of the scan
Different tissues absorb different amounts of radiation
bones=dense, absorb X-Rays well; Appear White
Soft tissues; skin, fat, muscles and organs allow rays to pass,
appear in varying shades of gray
Air appears black; lungs
Uses are as follows
 Determine whether a bone is chipped, dislocated or broken (Fractured)
 Evaluate Joint injuries and bone infections
 Diagnose/monitor degenerative conditions; arthritis
 Screen for lung and heart disease
 Find and treat artery blockage
 Diagnose cause of persistent couching or chest pain
 Check from broken ribs/punctured lung
 Evaluate unexplained abdominal pain
 Help locate objects; maybe swallowed by a child
 Detect scoliosis
 Evaluate infection of the sinuses
 Locate dental problems
 Detection of Cancer
Preparations
 In general:
- Undress area of body needing examination; may wear gown
- Remove jewelry, glasses, metal objects; Why?
- May need to wear a lead apron; to shield sex organs, Why?
- Medium Contrast; Barium and Iodine
Results
 Image films usually developed or viewed on-screen within
minutes
 Radiologist typically views and interprets the results
 Sends findings to doctor and than explain results
 RISKS:
 What are some risks?
- Amount of radiation exposed to is extremely low—cancer?
Looking Ahead
 X-Ray Technology has highly advanced from 1895
 X-ray Technology has specialized its imaging; such as
mammography and Computerized Tomography Scanning
(CT)
 Fluoroscopy; real-time imaging of body on video
 X-Ray Therapy: kill cancer cells and shrink tumors
 Thoughts?
 Typically the views of the body by these technologies are:
- Transverse
- Sagittal or
- Frontal sections
 Sagittal and Frontal are less difficult to understand; however
most CT & MRI images are transverse
- Which is why understanding cross-section anatomy is highly
important
Computerized Tomography (CT)
 Patient placed into a scanner and is exposed to a narrowly
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focused x-ray beam
Radiation not absorbed is called Remnant Radiation
Data is collected by a computer and converted into Pixels
(these make a digital picture)
Image Reconstruction is when the computer combines the
pixels to form an image (cross-Section)
Takes over 262.000 pixels to form a single CT Image
 A Contrast Medium is a dense liquid that prevents the passage
of remnant radiation and appears white in a CT image
 This process is used to help with hollow organs (Blood vessels) to
see contrast
 New CT technology is able to produce an image so fast that
physiological motions, respiratory or cardiac movements, do not
blur the image
 Where are the most commonly used?
- Chest
- Abdomen
- Pelvis
- Soft tissues of the neck
- brain
Magnetic Resonance Imaging (MRI)
 Patient is placed into a scanner that produces a very powerful magnetic
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field
Affects the nuclei of the atoms in patient's body to align
Once aligned a Radiofrequency Pulse is used to establish a second
field
Data is collected by a computer by sensors to form pixels image
reconstruction
Can produces transverse, sagittal or frontal sections
When pulse ends the hydrogen protons release an energy signal to
realign with first magnetic field
Time required is called Relaxation Time
- Two relaxation times: T1 (1st second image) and T2 (any time)
Appearance of Different Tissues in CT & MRI
Images
Tissue
CT Image
T1 MRI Image
T2 MRI Image
Bone
White
Black
Black
Muscle
Gray
Gray
Dark Gray
Brain
White Matter
Gray Matter
Dark Gray
Gray
Gray
Dark Gray
Dark Gray
Gray
Fat
Dark Gray to Black
White
Gray
Cerebrospinal Fluid
Black
Black
White
Blood
Flowing
Non-Flowing
White*
White*
Black
Gray
Black
White
Contrast Media
White
White
Not Used
Black
black
Air-Filled Structures (lungs, Black
stomach, etc.)
*Only if iodinated contrast media is present; otherwise appears gray