MCCCD Official Course Competencies:

ICE263  2008 Spring – 2011 Fall

Physics and Instrumentation of Computed Tomography

1.

Describe the history of Computed Tomography (CT) imaging and the components of a typical system. (I, II)

2.

Review the characteristics of radiation and the interaction of x-rays with matter. (III)

3.

Define CT terms pertaining to attenuation, scanning, displaying and annotating an image. (IV)

4.

Describe the CT computer data processing steps, the function of data acquisition system and the array processor. (V)

5.

Identify and define algorithms and kernel settings to include raw data, image data, and scan data. (VI, VIII)

6.

Describe the types of CT detectors, their function, location, and common materials use in those detectors. (VII)

7.

Explain post processing techniques to include the difference between reconstructing and reformatting an image. (IX)

8.

Identify the scan factors and explain how they affect image quality to include the steps needed to assure high image quality. (X)

9.

Describe the types of artifacts, their appearance on images, and how they may be eliminated or reduced. (XI)

10.

Describe how the selection of scan factors can affect patient dose and the correct application of each. (XII)

11.

Describe the scanner design that led to the development of spiral CT and the differences between conventional and spiral. (XIII)

12.

List and describe current data storage techniques. (XIV)

MCCCD Official Course Outline:

ICE263  2008 Spring – 2011 Fall

Physics and Instrumentation of Computed Tomography

I. Historical Development of Computed Tomography

A. Definition

1. Evolution of terms

a. Computerized transaxial tomography

b. Computerized axial tomography

c. Computed tomography

B. Research contributors

1. Johann Radon

2. Dr. Godfrey Hounsfield

3. James Ambrose and Louis Kreel

4. Allen MacLeod Cormack

C. Historical Events

1. 1917 - Radon proved 2-Dimensional or 3-Dimensional images reconstruction was possible

2. 1967- Working for Electric and Musical Industries (EMI), Hounsfield develops first CT scanner

3. 1970- Construction of CT units that could be used to examine patients begins

4. 1971- First clinical machine is installed - Atkinson Morley Hospital, Wilmington, England

5. 1973- EMI commercial head scanners become available

6. 1974- Whole body scanners become available

7. 1989- Spiral CT units become available

II. Computed Tomography Generations

A. First:Pencil beam geometry

B. Second:Narrow fan beam; multiple detector bank

C. Third:Fan beam, rotating detectors- 3600 of detectors

D. Fourth:Fan beam, fixed detectors

E. Fifth:Scanning electron beam

III. Characteristics of X-radiation

A. Sources

1. Natural

2. Artificial

B. Electromagnetic radiation

1. Ionization

2. Interactions with matter

a. Attenuation

i. Compton effect

ii. Photoelectric effect

IV. Definition of CT Terms

A. Terms relating to equipment hardware

B. Terms relating to image acquisition

C. Terms relating to quality control

D. Terms relating to dosage

E. Terms relating to image archival, storage, display

F. Terms relating to image reconstruction

G. Terms relating to software

V. CT Scanner Components and Operations

A. Radiographic tube

B. Filters

C. Collimators

D. Detectors

E. Data acquisition system

F. Computer and array processor

G. Consoles

H. Monitors and archival devices

VI. Digital Imaging

A. Process

1. Scanning

2. Sampling

3. Quantization

B. Image characteristics

C. Scan projection radiography

D. Beam configuration

E. Picture Archival and Communication Systems (PACS)

VII. Computed Tomography Process

A. Data acquisition

1. Methods

a. Slice-by-slice

b. Volumetric

2. Elements

a. Beam geometry

i. Pencil

ii. Fan

iii. Cone

iv. Slip rings vs. cables

3. Data acquisition system(DAS)

a. Components

i. Tube

ii. Detectors

iii. Filters

iv. Collimators

v. Analog-to-digital converter (ADC)

b. Functions

i. Measurement of transmitted beam

ii. Encoding measurements into binary data

iii. Logarithmic conversion of data

iv. Transmission of data to computer

VIII. Data acquisition process

A. Scanning/raw data/image data

1. Rays

2. Views

3. Profiles

a. Pixels

b. Matrices

c. Voxels

4. Sampling

a. Angular

b. Ray

B. Attenuation

1. Lambert-Beer Law

2. Linear attenuation coefficients

3. CT/Hounsfield numbers

C. Selectable scan factors

1. Scan field of view

2. Display field of view

3. Matrix size

4. Slice thickness

5. Window width

6. Window level

7. Millianperage Seconds (MaS) and Kilovoltage Peak (KvP)

8. Algorithm

9. Scan time and rotational arc

10. Radiographic tube output

11. Regional interest (ROI)

12. Magnification

13. Focal spot size and tube geometry

IX. Image reconstruction

A. CT computer

1. Minicomputer and microprocessor

2. Array processors

B. Reconstruction algorithms

1. Back-projection (historical only)

2. Filtered back-projection

3. Fourier reconstruction

4. 3-Dimensional

5. Interpolation

X. Image display, manipulation

A. Display

1. Cathode ray tube (CRT)

B. Manipulation

1. Image reformation

2. Image smoothing

3. Edge enhancement

4. Gray-scale manipulation

5. Three-dimensional processing

6. Multiplanar reformation

7. Shaded surface rendering

8. Stereotaxis

9. Radiation oncology treatment planning

10. Fusion

XI. Image Quality in CT

A. Definition

B. Determiners

1. Artifacts

2. Contrast resolution

3. Distortion

4. Noise

5. Spatial resolution

C. Influencing factors

1. Film contrast

2. Focal spot size

3. Beam geometry

4. Image receptor

5. Motion

6. Subject contrast

7. Viewing conditions

8. Selectable factors

a. Millianperage (mA)

b. Scan time

c. Slice width

d. Kernal

e. Kilovoltage (KV)

f. Presets Organ mode

D. Measurements by physicists

1. Contrast transfer and response function

2. Line spread function

3. Point spread function

4. Modulation transfer function

5. Edge response function

E. Quality control programs in CT

1. Definition of Quality Control (QC)

2. Principles

a. Regular performance

b. Prompt interpretation of results

c. Accurate and faithful bookkeeping

3. Common QC tests

a. Choosing techniques

b. Determining frequency of performance

c. Establishing acceptable limits from test results

d. Types

i. CT number calibration

ii. Standard deviation of CT number in water

iii. High-contrast resolution

iv. Low-contrast resolution

v. Accuracy of distance measuring device

vi. Distortion of video monitor

vii. Hard copy output distortion

viii. CT number flatness

ix. Hard copy output

x. Localization device accuracy

xi. CT couch indexing

xii. CT couch backlash

xiii. Light field accuracy

xiv. Slice width

xv. CT number vs. patient position

xvi. CT number vs. Patient size

xvii. CT number vs. algorithm selection

xviii. CT number vs. slice width

xix. Radiation leakage and scatter

xx. Kilovoltage Peak (KvP) wave form

XII. Radiation Protection Practices for the CT

A. Measuring patient radiation dose

1. Methods

2. Procedures

3. CT dose index (CTDI)

4. Multislice average does (MSAD)

B. Reducing radiation dose

1. Methods

a. Technical factor selection

b. Scanner dosimetry survey

c. Operator dependent

i. Shielding

ii. Positioning

XIII. Spiral Computed Tomography

A. Definition

B. Historical development

C. Differences between conventional and spiral CT

1. Operation

2. Advantages

3. Disadvantages

D. Scanner designs

1. High-voltage and low-voltage scanners

2. Slip-ring cylinders and slip-ring disk

XIV. Recording and Archiving

A. Film

1. Laser cameras

B. Archiving

1. Laser and optical disks

2. Digital Acquisition Tape (DAT) Tapes

3. Magnetic Tapes

4. Digital video disc (DVD)

5. Compact disc (CD) Rom

C. Picture Archival and Communication Systems (PACS)

1. Jukebox