Introduction to Medical Imaging

Imagining Modalities

1. Discus the discovery of x-ray2. the origin of electromagnetic radiation3. Identify the different modalities

X-ray ( radiography/Fluoroscopy) Computerized Tomography (CT) Nuclear Medicine, PET and SPECT Ultrasound (U/S) Magnetic Resonance Imaging (MRI)

3. Understand the basic principles for each imaging modality

Learning Objectives

By the end of this Lecture the student will be able to:

3

References• Text book of radiographic positioning and related anatomy; by Kenneth L.Bontrager, 5th edition

Useful Websites

http://www.e-radiography.net/

http://faculty.ksu.edu.sa/74344/default.aspx

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On November 8th, 1895, German scientist Wilhelm Roentgen was conducting experiments in his laboratory on the effects of cathode rays. Specifically he was observing the effect of passing an electrical discharge through gases at a low pressure. While doing so, Roentgen noticed when passing current through the cathode ray, rays were given off that passed through materials such as wood, paper and aluminum. The Roentgen conclusion from his experiments is (unknown type of radiation)

For that he name it X-RAYS

Who discovered the x-ray?

X meaning unknown

electromagnetic radiation of short wavelength produced when high-speed electrons strike a solid target

• Radiography (X-Ray)Radiography (X-Ray)

• Fluoroscopy (guided procedures) Fluoroscopy (guided procedures)

• Diagnostic / Interventional Transmission imagingDiagnostic / Interventional Transmission imaging

• Computed Tomography (CT)Computed Tomography (CT)

• Ultrasound (US) Ultrasound (US)

Gray-Scale /Color Doppler Reflection imagingGray-Scale /Color Doppler Reflection imaging

• Magnetic Resonance Imaging (MRI)Magnetic Resonance Imaging (MRI)

• Nuclear Medicine (Gamma/ PET/SPECT ) Emission imaging Nuclear Medicine (Gamma/ PET/SPECT ) Emission imaging

Imagining Modalities

Conventional X-ray Imaging.X-ray Production.

Electrons from cathodefilament are acceleratedtowards and impact therotating anode.

Rapid decelerationproduces heat (~ 98%)and x-rays (~2%)

High Electrical Potential

Electrons

-+

Exposure Recording Device

Radiation Penetrate the Sample

Over couch X-ray Tube and Table

High TensionCables

X-ray Tube housing

Controls

Light Beam Diaphragm

Table, and cassette holder

Conventional X-ray Image of a Hand

Normal Arthritic

Chest X-ray

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Fluoroscopy is a study of moving body structures - similar to an x-ray "movie." A continuous x-ray beam is passed through the body part being examined, and is transmitted to a TV-like monitor so that the body part and its motion can be seen in detail.

Fluoroscopy

X-RAYTUBE

IMAGEINTENSIFIER

TV CAMERAOR

CCD ARRAY(for digital screening)

CONTROLS

Fluoroscopy

Allows dynamic imaging of blood vessels (angiography)

and ‘interventional’ procedures

Computerized Tomography (CT)CT imaging combines special x-ray equipment with sophisticated computers to produce multiple images of the inside of the body. These cross-sectional images of the area being studied can then be examined on a computer monitor or printed.

Brain Axial ImageBrain Axial Image

CT ScannerCT Scanner

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Computed Tomography (CT)

Rotation givesmultiple projections

Array of detectors(rare-earth doped ceramics

with photodiodes)

X-raytube

Thin fan beamof x-rays

Patient(stationary)

Gamma camera head

Radioisotope ImagingNuclear medicine(NM)

IN Radioisotope imaging the formation of images provides information about the function of various organs in the body, using internally administered radioisotopes as a radiation source. The technique is widely used in medicine to locate tumors or cancers and to examine the flow patterns of body fluids.

Gamma Camera Scan.

Positron Emission Tomography (PET)

Radioisotope Imaging

Positron emission tomography (PET) is a nuclear medicine imaging technique which produces a three-dimensional images of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. Images of tracer concentration in 3-dimensional space within the body are then reconstructed by computer analysis. In modern scanners, this reconstruction is often accomplished with the aid of a CT X-ray scan performed on the patient during the same session, in the same machine.

Radioisotope Imaging

Is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera. However, it is able to provide true 3D information. This information is typically presented as cross-sectional slices through the patient, but can be freely reformatted or manipulated as required.

Single Photon Emission Computed Tomography (SPECT)

“Dead” areas of brainNo glucose metabolism

Human Brain - Stroke

Ultrasound imaging is a common diagnostic medical procedure that uses high-frequency sound waves to produce images sonograms) of organs, tissues, or blood flow inside the body. The procedure involves using a transducer, which sends a stream of high-frequency sound waves into the body and detects their echoes as they bounce off internal structures. The sound waves are then converted to electric impulses, which are processed to form an image displayed on a computer monitor. It is from these images that videos and portraits are made.

Ultrasound Imaging (US)

Ultrasound Transducer

Ultrasound Image of 19 Week Old Foetus

3D Ultrasound

Magnetic Resonance Imaging

Big superconductingmagnet (~ 1.5 tesla).

Gradient coils.

Radiofrequency coils.

(MRI)MR imaging uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, and all other internal body structures. The images can then be examined on a computer monitor, printed or copied to CD. MRI does not use ionizing radiation (x-rays).

T1-weighted T2-weighted Proton densityweighted

Magnetic Resonance Imaging (MRI) Axial Brain Images

Safety

X-ray imaging

Radioisotope scanning

Ultrasound Imaging

MRI

IonisingRadiation

Non-ionisingRadiation

Biological effect , need protection against unnecessary doses }

}

Modality RadiationType

Comments

Less harmful effects.Better for the foetus.

Unit III 27