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INTRODUCTION TO THE PHYSICS OF DIAGNOSTIC IMAGING

• Outline of Course

• Brief History

• Common Terminology

• Imaging Modalities

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TECHNOLOGICAL DEVELOPMENTS

• 1895 Roentgen discovers x-rays

x-ray tubes

Film

Film/screen

• 1950's Image Intensifiers

• 1960’s Mammography

• 1970's Computed Tomography (CT)

Ultrasound (US)

• 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

• 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:.1 ∞small

.2 ∞intense.3Monoenergetic/tunable

Detector:

.1No image blurring .2No added noise

.3Complete absorption of photons

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Emission Imaging

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• The following provides definitions of some common terms.

• RadiographyThe 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.

• FluoroscopyThe generation of a continuous stream of images using continuous x-rays (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.

Examples:Patient positioning for GI radiographs Catheter placementInterventional procedures

• 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 angiographyDigital Subtraction Angiography (DSA) l100-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.

• 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

• 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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