Why would causethe image to lookthis way?

Small matrix

Zoomed to excess

Spatial Resolution

Which demonstrates better spatial resolution?1 mm

= 1 lp/mmof spatial resolution

1 cm

= 8 lp/cmof spatial resolution

By definition: The ability of imaging equipment to demonstratetwo objects as two objects

MR spatial resolution tops out at 1 lp/mm,or 2 lp/mm for surface coils

10 cm FOV25 cm FOV

Which image has the best spatial resolution? 10 cm: Prove it

If the monitor is 500 pixels across, how many lp/mm are resolvedby each image?

500 pixels/250 mm = 2250 mm/500 mm = .5

2 what? 2 pixels/mm or 1 lp/mm .5 is what? pixel size

500 pixels/100 mm = 5 pixels/mm or 2.5 lp/mm 100 mm/500 mm = .2 mm pixels

If there were 1000 pixels, how would resolution change?

______________ is to digital, what gray scale isis analog x-ray imagesDynamic range

What are CT numbers based on, and what number is it given? Water, 0

What is the range of CT numbers +1000 to -1000

What is another name for CT numbers?(after the inventor)

Hounsfield units

What is the name of the functionthat controls the range of displayed pixel values?

Windows

For example: A window ______ of 5 width

Window width describes the range of pixel values

What is (are) the name(s) of the function that sets the middle of the range of any given window width

Windows

center levelFor example: This windowwidth of 5 has a ______or_____of 20

+7

-7

12345

Soft tissue window Bone window Lung window

Three common window settings. What are they called?

How Digital Computers Work

History of computational devicesBitsBytesPixelsMatrixDynamic rangeMachine languageProcessors (8,10,12 bits etc.)Base 10 numberingBinary numbering systemHounsfield units (CT numbers)

Pascal’s calculator - 1642

A series of gears, turned by hand, rotated a wheel with numbersthat showed in a window. When the number in the ones columnreached nine, it turned the wheel in the tens column to 1, andthe ones column returned to zero. Pascal invented his device to relieve the fatigue of spiritassociated with the work of doing arithmetic.

A mechanical device, not programmable

Jacquard’s Loom - 1804

Instructions for weavingpatterns into cloth were fedinto Jacquard’s machine by this early version of punched cards that were made of wood.

The red arrows show thecards entering and leaving the machine.

A mechanical device, that was programmable

Babbage’s Difference Engine - 1822

A crank was turned to perform a mechanical progression of numbered gears in columns that, like Pascal’s calculator,represented increasing powers of ten.

Hollerith’s tabulator

Like Pacal’s calculator, and Babbage’s difference engine numbers were carried over from one column to the next. The great advantage of this device was the use of electric motors to drive mechanical parts, and punched cards to input data.

In 1880 it took 9 years to tally the results of the US census. Herman Hollerith built an electromechanical calculator that used punched cards to input data on the population (age, gender, numbers in family, etc), and reduced the time to do it in half, on a greater population, with a more detailed analysis.

Mark I - 1944

Banks of mechanical switches where driven by electric motors.Switches opened and closed to perform computations. Punched cards were used to input data.

An electromechanical device, that wasprogrammable.

ENIAC - 1946

The first fully electronic calculator used 18,000 vacuum tubesthat replaced the switches of Mark I. Data wasaccomplished by turning knobs, reconfiguring telephonepatch cords, and punched cards.

“Computers of the future may weigh nomore than 1.5 tons.”

Popular Science, 1949

Cathode Anode

Grid

Vacuum tube: When the grid is positively charged electrons are drawn from the cathode to the anode, creating a closed circuit (1).

When the grid is negatively charged electronsare repelled, and circuit is open (0).

Transistors: Similar in principle to theoperation of a vacuum tube. The solidstate semi-conducting material allowed this switching device to use less energyand produce less heat in a smaller component.

Vacuum Tubes and Transistors

3rd Integrated Circuit (IC)2nd Transistors1st Vacuum tube

Generations of Electronic Computers

Three Things a Computer Does

1. Arithmetic functions

2. Comparison functions

3. Memory

Accomplished with accuracy and speed

What is Digital Imaging?Digital Imaging is the transforming of energy: (from light photon, sonic, magnetic, x-ray, or gamma radiation sources) to electrical signals that are measured and assigned discrete binary values.

Binary data is processed into image information which may be displayed on a monitor, enhanced, printed, and stored as a computer file.

What is the name of the first electronic computer and when wasit completed?

What switching devices were used in the first three generations of electronic computers?

Define digital. How is it different from analog?

What is the name of the memory (registers of switching elements)that is being used when a program is being run?

How is RAM different than secondary memory?

At what point in the acquisition of image data does digital imaging and analog imaging differ

Step 1. Send the energy on its way

Step 2. Capture the remnant energy in an IR or digital detector

Step 3. Sample the captured energy and transform it to electrical signals

Step 4. Assign the signals discrete values in an Analog to Digital Converter (ADC)

Step 5. Use those values to set the registers in RAM (On/OFF)

Step 6. Display the image on a monitor

Step 7. Save the image on a secondary storage device

Random access memory (RAM) (345): Semiconductor switches in microchips have addresses: locations which may be accessed directly (randomly): a quick, electronic process. When a program (such as word processing) is loaded from a secondary storage device (such as a hard drive) it is copied into a RAM chip. As changes are made they are made in RAM. The program must be saved back to the hard drive to be retained. RAM is also called volatile memory, which means that when power is turned off data in RAM is lost.

Read only memory (ROM) (345): Memory that can only be read (used) and not written to (changed).

Integrated circuits (IC) have millions, billions, and trillions of AND, OR, and NOT gates embedded in the layers of the miniaturized circuits of the semi-conductor material.

The next seven slides demonstrate:Step 5. Use those values to set the registers in RAM (On/OFF)

Arithmetic Functions

OFF

The Basics of Digital Data Storage in Random Access Memory (RAM)

In this analogy the light bulb is apixel on a monitor

The switch is a bit (binary digit)in the computer circuitry

ON

The Basics of Digital Imaging

Flip the switch (binary digit or bit) and light upthe bulb (pixel)

Row and columns of pixelsform the matrix

Dynamic range of 2 (21)

How is contrast added to an image?

Switches.

The more of them in the ON position, the brighter the light

ONOFF

A difference of .01 V is detectable in the MR signal

.01V

ON ON A difference of .01 V is detectable in the MR signal

.01V .02V

Dynamic range of 256 (28)

OFF

ON

OFFOFFOFFOFF

ONON

OFFON

OFF

ONOFFOFF

ONONOFF

OFFON

OFFON

4 2 1

0

.2V

.1V

.3V

.4V

.5V

.6V

More bits, in various configurations,create a greater dynamic range (analogous to the radiographic scaleof contrast)

ON ON ONOFF OFF OFF OFF OFF

In computer circuitry 8 bits are grouped together

8 bits = 1 byte

ON ON ON ON ON ON ON ON

An 8 bit processor displays a dynamic range of 256 (28)The maximum required voltage is only 2.55 V

The two positions a switch can be in are numbered: 0 = OFF 1 = On

10011011111010010001011101011001

Machine language computer code

OFF OFFON ON

OFFON ON

0 0 1 1 0 1 1 1

ON

The language of computers is binary (two numbers)

Bits are either ON (1) or OFF (0)

Human beans count in decimals (base 10)

because

They have 10 fingers and 10 toes

0123410 10 10 10 10

ones

hund

reds

thou

sand

s

tensten

thou

sand

s

Ten is raised to every powerof itself to create columnsof higher orders

Binary numbering

20

21

22

23

24

By definition: Any number raised to the power of 0 is 1

Any number raised to the power of 1 is the number itself

* Count from right to left* Each column is twice the previous* Pick any column and it will be one more than the sum of all the previous columns

Binary numbering

1248163264128256

20

21

22

23

24

= 140 0 0 0 0 1 1 1 0= 421 0 1 0 1 0

1 1 1 1 1 1 1

= 127

Binary numbering system (344): In the base 2 numbering system all values are represented by 0 or 1. Zero = OFF when representing an open switch. One = ON.

Examples:

Columns are derived from:

Columns:

1248163264128256

28

= one byte = 256 shades of gray

An 8 bit processor displays a dynamic range of 256

1 1 1 1 1 1 1 1 = 255

0 0 0 0 0 0 0 0 = 0 When all the bits are ON a pixel is illuminated to max intensity There are 255 possibilities of bits being ON.

When all the bits are OFF the pixel is black.

8 bits store a dynamic range of 256 from dark to bright.

An 8 bit processor displays a dynamic range of 256

What will a 9 bit processor display? 10 bit?

12 bit?

16 bit?

102411 bits 2048 409613 bits 819214 1638415 bits 22768 44536

What effect does increasing the dynamic range have?

It increases the memory requirements dramatically!

512 shades of gray

10011011111010010001011101011001

OFF OFFON ON

OFFON ON

0 0 1 1 0 1 1 0

ON

1241632

= 55

A byte of memory in this midsagittal MRI of the head defines how brightly one pixel will be illuminated. .

George Boole

1815-1864

On + Off = Off

Off + Off = Off

On + On = On

AND Gate

On + Off = On

Off + Off = Off

OR Gate

On + On = On

On = Off

Off = On

NOT Gate

1+0

0 1

Operation of a Half Adder

= 1

0+1

0 1

Operation of a Half Adder

= 1

1+1

1 0

Operation of a Half Adder

= 2

0+0

0 0

Operation of a Half Adder

= 0

35013502

41074108

Welcome to RAM

Population: 376,243,101,765

RAM: addressable memoryin an array of ICs

RAM (Random Access Memory)

Altair’s 256 bytes of internalmemory could hardly storea memo, so in 1979George Morrow created amemory board to extend it.

Here he demonstrates how 8K of RAM is concealed in a trench coat.

In the early years of computing, memory was so precious years were entered without the century prefix (79 instead of 1979) to save two bytes. That led to the scare known as Y2K.

Question: What is the unit of measurement of frequency?

Examples:

Kilohertz Thousands of

Megahertz Millions of

Gigahertz Billions of

Terahertz Trillions of

Clue: It is also called cycles per second.

Answer: hertz

The same prefixes apply to bytes