INTRODUCTION TO THE PHYSICS
OF DIAGNOSTIC IMAGING
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Outline of Course
Brief History
Common Terminology
Imaging Modalities
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TECHNOLOGICAL DEVELOPMENTS
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1895
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1950's
Roentgen discovers x-rays
x-ray tubes
Film
Film/screen
Image Intensifiers
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1960’s
Mammography
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1970's
Computed Tomography (CT)
Ultrasound (US)
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1980's
Magnetic Resonance Imaging (MRI)
Digital Subtraction Angiography (DSA)
Computed Radiography (CR)
• 2000's Digital Radiography (DR)
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TRANSMISSION IMAGING
Image consists of a spatial
distribution of x-ray flux
(spatial modulation of the
source flux).
– Film Radiography
Fluoroscopy
– CT
– DSA
– CR & DR
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EMISSION IMAGING
Nuclear Medicine
Single Photon Emission
Computed Tomography
(SPECT)
Positron Emission
Tomography (PET)
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Transmission Imaging
This is the basic setup of x-ray imaging. We will spend a
semester discussing different aspect of such x-ray imaging
systems. Different arrangements, sources, detectors etc. will
be detailed.
Source:
∞ small
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∞ intense
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Monoenergetic/tunable
Detector:
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No image blurring
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No added noise
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Complete absorption of photons
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Emission Imaging
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The following provides definitions of some common terms.
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Radiography
The generation of an x-ray image using a single, short (typical 0.1
sec, range 0.005 - 2 sec) x-ray pulse. Several radiographs may be
taken for a complete diagnosis.
Examples: Chest "film"
Extremity "film"
Traditionally, radiography is performed with non-real-time
detectors. X-rays create a latent image which must be developed
(e.g. film and selenium plates (CR)). Very recently, "flat-panel"
digital detectors have been introduced in which the latent image is
"read" from the detector within a few seconds of formation.
Fluoroscopy
The generation of a continuous stream of images using continuous xrays (or a train of x-ray pulses (e.g. 30 pulses/sec)).
Fluoroscopy requires a real-time detector. Traditionally, this has
been an image intensifier coupled to a video camera.
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Examples:
Patient positioning for GI radiographs Catheter placement
Interventional procedures
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Fluorography
"Fluoroscopy" is generally used to describe procedures in which the
images, having been used during the procedure, are not recorded.
The same equipment can be used to record images for diagnostic
purposes. This is sometimes referred to as "fluorography".
Examples:
Cine angiography
Digital Subtraction Angiography (DSA) l
100-mm Photospot
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Mammography is the process of using low energy X-rays to
examine the human breast. It is used to detect different types
of tumors and cysts.
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Digital Radiography
Instead of using film, digital radiography converts x-ray
images to electronic data that can be viewed on a monitor
and stored on computer in digital formats. The technique
allows specific areas of the image to be enlarged, and the
contrast of the image can be adjusted to allow greater
visibility.
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Projection Imaging
Images in which the body's 3-dimensional distribution is
projected onto a 2-dimensional image.
Example:
Radiography
Fluoroscopy
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Tomographic Imaging
Images in which the body's 3-dimensional distribution is
retained.
Example:
CT
MRI
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Projection Imaging (Fluoroscopy)
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Tomographic Imaging
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Characteristics of Different Modalities
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