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RADT 411

CT Physics- unit 1

QuestionAnswer
Central Processing Unit (CPU) directs info to and from the various components of the computer
Arithmetic logic unit (ALU) performs calculations in computer
Input devices devices used to enter info into the computer for processing; ex: keyboards, mouse, camera, etc
Output devices devices that displays info generated in a computer; ex: printers, CRT screen, video monitors
Hospital Information Systems (HIS) comprehensive info system dealing with all aspects of info processing in a hopital; focuses on admin issues, pt demographics, financial data, etc
Radiology Information Systems (RIS) computer system used to manipulate and distribute pt radiologic data; stored radiology reports, scheduling of pts, etc
PACS computer or networks dedicated to the storage, retrieval, distribution, and presentation of images
EHR digital pt health records
Beam attenuation measures what comes out of pt.
Digital image image converted into numerical values for transmission or processing
Matrix arrangement of columns and rows
Pixel picture element (2D)
Voxel volume element (3D)
Smaller the pixels... the better spatial resolution
Pixel size= FOV(mm)/matrix; be sure to convert to cm if in the question
Increase matrix... better spatial resolution
Increase FOV... improve image quality
Decreased FOV= increased matrix size
Spatial resolution ability to represent small objects and differentiate between closely spaced objects
NM 64x64
US 512x512
Digital fluoro 1000x1000
Digital radiography 2000x2000
CT 512x512
MRI 256x256
Mammography 4000x4000
Algorithm set of rules for getting a specific output from a specific input
Convolution process of filtering data
Contrast revolution ability to differentiate small differences in density on the image
Noise random background info that is detected, but does not contribute to the image quality
Thermal regulation your bodies way to regulate body temp; hypothalamus controls it
"Tomos" means cross section
Why CT is better than Diagnostic removes superimposition of tissues, improved contrast resolution, view body in axial, sagittal, and coronal planes, and contrast scale of tissues can be changed
Limitations of CT compared with Diagnostic high pt dose, poor spatial resolution (good contrast res), artifacts
Cormack studied nuclear physics
Hounsfield theorized if an x-ray beam passed through an object, measurements could be taken and with computer reconstructions and image produced; EMI scanner 1971 (used gamma rays and only scanned brains, took 20 mins)
Dr. Ledley jack of all trades, developed whole body scanner in 1974;
1st gen scanner pencil beam, parallel beam, 1-2 detectors, 180 degree arc around pt (1 deg at a time), water made image more uniform
2nd gen scanner fan beam geometry, linear array of detectors, only 6 rotations of tube instead of 180, 180 degree arc around pt (30 deg at a time); 1st whole body scanner
3rd gen scanner wide fan beam, curved array of detectors (biggest change), continuous scanning motion, 360 deg rotation slice by slice, reduced scan time, con: "ring artifacts" caused by bad detector
4th gen scanner wide fan beam, stationary ring of detectors, rotating tube, 360 deg rotations, interspaces (spaces between detectors cause lost info, half scans, full scan (most accurate of 3), or over scans (scan 360 and then another 180 deg), and more pt dose
5th gen scanner AKA cardiac unit, electron beam tomography (EBT), or cardiac cine CT (only scanned heart), images like movies, faster scan (less than 100 ms), no moving parts
6th gen scanner
7th gen scanner
Created by: meechthebeech91
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