Instrumentation_CT

• 1: System software (Windows)
• 2: Applications software (Microsoft Works)
• 3: Software development Tools (BASIC)

• 1: Input device (keyboard, mouse)
• 2: CPU (brain)
• 3: Internal Memory (part of CPU)
• 4: Output device (printer, cd)
• 5: External Memory or Storage (PAC's)

digital integrated circuit that processes data and controls the general workings of the computer

on continuous physical quantities that are not digital

on digital data through math and logical operations

Digital

• Info is put into computer in analog form
• ADC converts the input to digital for processing
• Data is processed in digital form
• DAC converts the output to analog for viewing

• Picture
• Archiving &
• Communication
• Systems

Film and Tube move simultaneously in opposite directions to produce an image based on a focal plane and thickness chosen by the technologist

1921

• Tube and film moved in "figure 8" (opposite directions)
• Used to compensate for the traditional tomographies downfalls (elongating kidneys and having superimposition on planes close to focal plane)

• uses digital flat-panel technology
• combines digital processing techniques & conventional tomographic acquisitions

Potential to be used as a low dose imaging alternative to CT

EMI Limited-beginning to work on radar systems and computer technology

He was investigating pattern recognition and reconstruction techniques using the computer

Discoverer of CT

9 days

americium gamma radiation

He developed solutions to the mathematical problems in CT

He developed the 1st whole body CT scanner

1971

Pencil Beam

1 (single detector)

5min per image (would result in patient motion-of course)

Would rotate 1* to the next angular position to acquire the next set of images

Fan beam geometry

1975

30 detectors

20 seconds

in a Straight line

the tube/detector assembly moves across the patient and then rotates by 5* (unlike the 1st Gen-1*)

1975

Fan Beam

in an arc (opposed to 2nd Gen where they were a straightline)

less than 1sec per image

Slip Rings

Rotate-rotate scanners

Fan beam

The detectors encircle the patient but do not rotate

the tube rotates around the patient (not the detectors)

more scatter radiation-a single slice requires 4800 detectors

1980-1984

Cardiac applications (able to "freeze" a beating heart)

Dual source scanner

2 xray tubes, & 2 sets of detectors that are offset by 90*.

Cardiac imaging & some CTA's

Flat-panel digital detectors similar to the ones used in DR

No, it is still a prototype

Cesium Iodide Scintillator which is coupled to an amorphous silicon thin-film transistor array

• Electromechanical device consisting of circular electrical conductive rings and brushes that transmit electrical energy across a rotating interface
• It allows the tube to continuously rotate & provides electrical power to operate the x-ray tube.

Within gantry (instead of in control room)

480 AC

Xray controls are trasmitted to slip ring by means of low voltage brushes that glide in contact grooves on the stationary slip ring then power is provided to the high-voltage transformer which transmits high voltage to the tube.

• AC delivers power to the high-voltage generator, which then provides power to the slip ring.
• This is then transferred to the Xray Tube

• Faster scan times and minimal interscan delays
• Capacity for continuous acquisition protocols
• Eliminates the start-stop process with Conventional CT scanners
• Removal of cable wrap around the process

Photons of x-ray beam (that have passed through the patient) are measured. A series of these measurements is then used to create raw data. A construction process (interpolation) is then used to convert this data into cross-sectional images we look at. In the resulting images each tissue displays it's own characteristics or hounsfield units.

Console to Host Computer to Scan Controller to DAC or High Voltage Generator to Gantry Control to Gantry to Amplifier to S&H to ADC to Array Processor to Host Computer to Storage Device

• Instructional commands
• usually consists of: keyboard, touch panel, window controls, image display

• Primary link between Technologist & other components of Imaging system
• Translates each of Technologists commands entered at console into the "computer language" and passes it on to the scan controller or storage device
• Stores calculated image

• Stores images in digital form to preserve the wide dynamic range of images
• sores them in 2D pixel arrays
• Types: Magnetic Tape, Digital Videotape, Optical Disk, Optical Tape, CD

• Responsible for timing & operation of patient table, gantry & high voltage generator
• Allows operator to communicate with system to enable scanning

• (Can be housed in Gantry)
• Produces the high voltage potential that exists between the cathode & anode of CT x-ray tube
• Has 30-60 kilowatts

• Digital to Analog Converter
• used to convert electronic signals sent from the scan controller to the gantry control into the analog(continuous) waveform that the computer can understand.

Houses the x-ray tube, detectors & data acquisition system.

Usually 70cm (available scan area=50cm)

12-30 degrees in either direction

On table in Supine-head first position

Extends along the patient table-head to toe

Extends from patients right to left

Extends anterior to posterior

• X-rays have passed through the patients body & are measured by detectors
• The attenuation info is then converted into tiny electrical signals
• These tiny signals pass through the amplifier to do just that, greatly increase their strength

• Sample & Hold Component
• The Analog amplified electrical signals are sampled

• Analog to Digital Converter
• Amplified electrical signals are digitized (so we can view them)

• Stores the raw data file
• Calculates the image that is seen on console
• Final image is constructed & made available for viewing at the console