7 physical principles of CT

THÔNG TIN TÀI LIỆU

Cấu trúc

PHYSICAL PRINCIPLES OF COMPUTED TOMOGRAPHY
RADIOGRAPHY LIMITATIONS
SUPERIMPOSITION
TISUE DIFFERENCE SENSITIVITY 5%-10%
TOMOGRAPHY ( CONVENTIONAL)
PowerPoint Presentation
TOMOGRAPHY
Slide 8
Slide 9
Slide 10
CT ADVANTAGES
LIMITATIONS OF CT
Slide 13
GOALS OF CT
CT DATA AQUISITION
Slide 16
SLIP RINGS
Slide 18
SEQUENTIAL-SLICE BY SLICE SCANNING
SCANNING
TRANSMISSION
Slide 22
Slide 23
Total # of trans. measurements= # of views X # of rays in each view
ATTENUATION
Slide 26
DATA AQUSITION GEOMETRIES
CONTINUOUS
STATIONARY
CT 120-140 KVP
ORIGINAL CLINICAL CT SCANS COMPOSED OF
Slide 32
Slide 33
Slide 34
Slide 35
SCAN FOV
SCAN FOV-SMALL
SFOV - HEAD
Slide 39
TOO SMALL OF SFOV – OUT OF FIELD ARTIFACT
SCAN FOV-RESOLUTION
RECONSTRUCTION
Slide 43
DISPLAY FOV vs SCANNING FOV
PIXEL SIZE
MOST SCANNERS PIXEL SIZE 1 TO 10mm
EXAMPLE:
EACH PIXEL IN CT HAS RANGE OF GRAY SHADES
PIXEL vs VOXEL
PIXEL SIZE DEPENDS ON:
VOXEL SIZE DEPENDS
IMAGE DISPLAY
GRAY SCALE DISPLAY MONITOR RESOLUTION IS RELATED TO THE SIZE OF THE PIXEL MATRIX
MATRIX
PIXEL MATRIX
IN CT DIGITAL RECONSTRUCTED IMAGE IS CONVERTED IMAGE IS CONVERTED INTO A GRAY SCALE IMAGE.
Slide 57
The high performance video display of the microcomputer is connected to the system via an interface board. The video display is a form of cathode ray tube sometimes referred to as a raster display. The term raster describes the technique of producing the picture or text which is formed by a beam of electrons that repeatedly scans across the screen to form a uniform pattern of closely spaced, horizontal lines (the raster), covering the entire screen. The screen consists of a phosphor that converts the energy of the electron beam into visible light. A picture is formed by "turning on and off" the electron beam at appropriate points in the scanning of the screen surface.
CRT OPERATION
IMAGE FORMATION ON THE MONITOR
Slide 61
Slide 62
CT NUMBER
Slide 64
LINEAR ATTENUATION COEFFICIENT ( cm-1)
CT # vs BRIGHTNESS LEVEL
CT #
CT #
CT # OF CYST
CT # OF LIPOMA ( FATTY TUMOR)
Slide 71
Slide 72
Slide 73
Slide 74
Slide 75
DATA FLOW IN CT
CT ADVANTAGES AND DISADVANTAGES

Nội dung

PHYSICAL PRINCIPLES OF COMPUTED TOMOGRAPHY RADIOGRAPHY LIMITATIONS  SUPERIMPOSITION  DIFFICULTY IN DISTINGUISHING BETWEEN HOMOGENOUS OBJECTS OF NON-UNIFORM THICKNESS SUPERIMPOSITION TISUE DIFFERENCE SENSITIVITY 5%-10% TOMOGRAPHY ( CONVENTIONAL)  ELIMINATES TISSUE SUPERIMPOSITION  INCREASES CONTRAST OF LOW SUBJECT CONTRAST TISSUES TOMOGRAPHY TOMOGRAPHY TOMOGRAPHY CT NUMBER LINEAR ATTENUATION COEFFICIENT ( cm-1)         BONE BLOOD G MATTER W MATTER CSF WATER FAT AIR 0.528 0.208 0.212 0.213 0.207 0.206 0.185 0.0004 CT # vs BRIGHTNESS LEVEL + 1000 -1000 CT # 1000 CT # - 500 CT # OF CYST CT # OF LIPOMA ( FATTY TUMOR) -100 W 120 L 40 W 80 L 40 DATA FLOW IN CT REFERENCE DETECTOR REFERENCE DETECTOR PREPROCESSOR ADC COMPUTER RAW DATA PROCESSORS RECONSTRUCTED DATA DISK TAPE BACK PROJECTOR CONVOLVED DATA DAC CRT DISPLAY CT ADVANTAGES AND DISADVANTAGES          EXCELLENT LOW CONTRAST RESOLUTION WINDOWING- IMAGE MANIPULATION TAILORED TO OBSERVER NEEDS SPIRAL CT-SINGLE BREATH HOLD STUDIES ( CTA, MPR, VIRTUAL REALITY CT, CT ENDOSCOPY) CT ASISST IN RADIATION THERAPY BONE SCAN PACKAGE XENON CT PERFUCION CT DIGITAL PROCESSING ABILITY ... ISOCENTER SCAN FOV SFOV DETECTORS SCAN FOV-SMALL SFOV DETECTORS SFOV - HEAD TOO SMALL OF SFOV – OUT OF FIELD ARTIFACT SCAN FOV-RESOLUTION SFOV RECONSTRUCTION Ц RECONSTRUCTION CT# SCAN FOV-RESOLUTION... TISSUES TOMOGRAPHY TOMOGRAPHY TOMOGRAPHY CT ADVANTAGES LIMITATIONS OF CT  UNABLE TO DIFFERENTIATE BETWEEN TISSUES WITH SLIGHT CONTRAST DIFFERENCES < 1% GOALS OF CT  MINIMAL SUPERIMPOSITION  IMAGE... DIFFERENCE RECORDING CT DATA AQUISITION SLIP RINGS SEQUENTIAL-SLICE BY SLICE SCANNING SCANNING TRANSMISSION RELATIVE TRANSMISSION=Io/I Total # of trans measurements= # of views X # of rays in each

Ngày đăng: 13/08/2020, 09:23