digital integrated circuit that processes data and controls the general workings of the computer
Analog computers operate how?
on continuous physical quantities that are not digital
Digital computers operate how?
on digital data through math and logical operations
Does digital or analog use the binary system?
Elements of digital signal processor
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
What does PACS stand for?
Dow does Tomography work?
Film and Tube move simultaneously in opposite directions to produce an image based on a focal plane and thickness chosen by the technologist
How early did Tomography start?
What is Pluridirectional Tomography?
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)
What is tomosynthesis?
uses digital flat-panel technology
combines digital processing techniques & conventional tomographic acquisitions
What can the tomosynthesis possibly be used for?
Potential to be used as a low dose imaging alternative to CT
What was Godfrey Newbold Hounsfield working on in 1951?
EMI Limited-beginning to work on radar systems and computer technology
What was Godfrey Hounsfield doing in 1967?
He was investigating pattern recognition and reconstruction techniques using the computer
Who is Godfrey Hounsfield?
Discoverer of CT
The original lathe bed scanner took how long to scan an object?
What type of radiation did the Lathe Bed scanner use?
americium gamma radiation
Who is Allan MacLeod Cormack?
He developed solutions to the mathematical problems in CT
Who is Dr. Robert Ledley?
He developed the 1st whole body CT scanner
1st Generation Scanners produced in which year?
1st Gen CT-used what type of beam?
1st Gen CT-had how many detectors?
1 (single detector)
How long was the total scan time per image on 1st Gen CT?
5min per image (would result in patient motion-of course)
How did 1st Gen CT work?
Would rotate 1* to the next angular position to acquire the next set of images
What type of beam is used in 2nd Gen CT?
Fan beam geometry
What year did the 2nd Gen CT come out?
How many detectors are used in the 2nd Gen CT?
How long did the 2nd Gen take to acquire an image?
2nd Gen CT uses multiple detectors, how?
in a Straight line
How does the 2nd Gen CT work?
the tube/detector assembly moves across the patient and then rotates by 5* (unlike the 1st Gen-1*)
3rd Gen CT was introduced in which year?
3rd Gen CT uses what type of beam?
How are the detectors place in 3rd Gen CT?
in an arc (opposed to 2nd Gen where they were a straightline)
Total scan time of a 3rd Gen CT?
less than 1sec per image
3rd Gen CT started using new technology known as?
3rd Gen CT was AKA?
4th Gen CT uses what type of beam?
4th Gen CT how do the detectors work?
The detectors encircle the patient but do not rotate
What does rotate in 4th Gen CT?
the tube rotates around the patient (not the detectors)
What was a disadvantage to 4th Gen CT?
more scatter radiation-a single slice requires 4800 detectors
5th Gen CT built when?
What was the 5th Gen CT mainly used for?
Cardiac applications (able to "freeze" a beating heart)
6th Gen CT is a what?
Dual source scanner
How does a 6th Gen CT work?
2 xray tubes, & 2 sets of detectors that are offset by 90*.
What is 6th Gen CT mainly used for?
Cardiac imaging & some CTA's
7th Gen CT uses what?
Flat-panel digital detectors similar to the ones used in DR
Is 7th Gen CT used today?
No, it is still a prototype
What are the detectors made of in 7th Gen CT?
Cesium Iodide Scintillator which is coupled to an amorphous silicon thin-film transistor array
What is Slip Ring Technology?
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.
Where are the generators located?
Within gantry (instead of in control room)
Low voltage slip ring uses how much AC (alternating current)
How does a Low voltage Slip ring work?
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.
How does a High-Voltage Slip Ring work?
AC delivers power to the high-voltage generator, which then provides power to the slip ring.
This is then transferred to the Xray Tube
What are the advantages to Slip Rings?
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
How Does CT work?
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
What happens within the Console?
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
High Voltage Generator?
(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.
Aperture of Gantry?
Usually 70cm (available scan area=50cm)
Gantry tilting range=
12-30 degrees in either direction
Patient Coordinating System-Assume the Patient is lying how?
On table in Supine-head first position
in Patient Coordinating System what is Z-axis?
Extends along the patient table-head to toe
in Patient Coordinating System what is X-axis?
Extends from patients right to left
in Patient Coordinating System what is Y-axis?
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