Why would cause the image to look this way? Small matrix Zoomed to excess

Spatial Resolution Which demonstrates better spatial resolution? 1 mm = 1 lp/mm of spatial resolution 1 cm = 8 lp/cm of spatial resolution By definition:The ability of imaging equipment to demonstrate two objects as two objects MR spatial resolution tops out at 1 lp/mm, or 2 lp/mm for surface coils

10 cm FOV 25 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 resolved by each image? 500 pixels/250 mm = 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 is is analog x-ray images Dynamic range What are CT numbers based on, and what number is it given? Water, 0 What is the range of CT numbers+1000 to What is another name for CT numbers? (after the inventor) Hounsfield units

What is the name of the function that 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 level For example: This window width of 5 has a ______or_____ of

Soft tissue windowBone windowLung window Three common window settings. What are they called?

How Digital Computers Work History of computational devices Bits Bytes Pixels Matrix Dynamic range Machine language Processors (8,10,12 bits etc.) Base 10 numbering Binary numbering system Hounsfield units (CT numbers)

Pascal’s calculator A series of gears, turned by hand, rotated a wheel with numbers that showed in a window. When the number in the ones column reached nine, it turned the wheel in the tens column to 1, and the ones column returned to zero. Pascal invented his device to relieve the fatigue of spirit associated with the work of doing arithmetic. A mechanical device, not programmable

Jacquard’s Loom Instructions for weaving patterns into cloth were fed into Jacquard’s machine by this early version of punched cards that were made of wood. The red arrows show the cards entering and leaving the machine. A mechanical device, that was programmable

Babbage’s Difference Engine 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 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 was programmable.

ENIAC The first fully electronic calculator used 18,000 vacuum tubes that replaced the switches of Mark I. Data was accomplished by turning knobs, reconfiguring telephone patch cords, and punched cards. “Computers of the future may weigh no more 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 electrons are repelled, and circuit is open (0). Transistors: Similar in principle to the operation of a vacuum tube. The solid state semi-conducting material allowed this switching device to use less energy and produce less heat in a smaller component. Vacuum Tubes and Transistors

3 rd Integrated Circuit (IC) 2 nd Transistors 1 st 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 was it 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 a pixel 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 up the bulb (pixel)

Row and columns of pixels form the matrix

Dynamic range of 2 (2 1 ) How is contrast added to an image? Switches. The more of them in the ON position, the brighter the light

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

ON A difference of.01 V is detectable in the MR signal.01V.02V

Dynamic range of 256 (2 8 )

OFF ON OFF ON OFF ON OFF ON OFF ON OFF ON OFF ON V.1V.3V.4V.5V.6V More bits, in various configurations, create a greater dynamic range (analogous to the radiographic scale of contrast)

ON OFF In computer circuitry 8 bits are grouped together 8 bits = 1 byte

ON An 8 bit processor displays a dynamic range of 256 (2 8 ) The maximum required voltage is only 2.55 V The two positions a switch can be in are numbered: 0 = OFF 1 = On

Machine language computer code OFF ON OFF ON 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 ones hundreds thousands tens ten thousands Ten is raised to every power of itself to create columns of higher orders

Binary numbering 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 = = = 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:

= one byte = 256 shades of gray An 8 bit processor displays a dynamic range of = = 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? bits bits bits What effect does increasing the dynamic range have? It increases the memory requirements dramatically! 512 shades of gray

OFF ON OFF ON ON = 55 A byte of memory in this midsagittal MRI of the head defines how brightly one pixel will be illuminated..

George Boole

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

Operation of a Half Adder = 1

Operation of a Half Adder = 1

Operation of a Half Adder = 2

Operation of a Half Adder = 0

Welcome to RAM Population: 376,243,101,765 RAM: addressable memory in an array of ICs

RAM (Random Access Memory) Altair’s 256 bytes of internal memory could hardly store a memo, so in 1979 George Morrow created a memory 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