Tomography: From the Greek word “tomos” section. The process for generating a tomogram, a two- dimensional image of a section through a three- dimensional object. Tomography achieves this result by simply moving an x-ray source in one direction as the x-ray film is moved in the opposite direction during the exposure to sharpen structures in the focal plane, while structures away from the focal plane appear blurred.
CONVENTIONAL RADIOGRAPHY HAS LIMITATIONS: TWO DIMENSIONAL IMAGE WITH INFINITE DEPTH - SUPERIMPOSITION OF UNDERLYING STRUCTURES (LATERAL AND OBLIQUE VIEWS DON’T SOLVE IT COMPLETELY). INABILITY TO DEMONSTRATE SLIGHT DIFFERENCES IN SUBJECT CONTRAST CHARACTERISTIC OF SOFT TISSUE.
TOMOGRAPHY – SOLUTION? CONVENTIONAL TOMOGRAPHY ATTEMPTED TO ELIMINATE THE SUPERIMPOSITION PROBLEM BY BLURRING THE STRUCTURES ABOVE AND BELOW THE TOMOGRAPHIC FOCAL PLANE. CONTRAST OF AN IMAGE CAN ALSO BE CHANGED BY VARYING TOMOGRAPHIC ANGLE (DISTANCE OF A TUBE TRAVEL) MULTIDIRECTIONAL TUBE MOVEMENT MAKES THE BLURRING OF UNWANTED STRUCTURES EVEN MORE EFFECTIVE.
TOMOGRAPHY STILL LIMITED IMAGE BLURR PRESENT EXCESSIVE SCATTER RADIATION – FILM FOG
RADIOGRAPHY AND TOMOGRAPHY TISSUE DIFFERENCE SENSITIVITY 5-10%
IMAGE RECONSTRUCTION TRANSMISSION MEASUREMENTS COLLECTED BY THE CT DETECTORS ARE SENT TO THE COMPUTER FOR THE PROCESSING. COMPUTERS USES MATHEMATICAL ALGORITHM TO RECONSTRUCT THE IMAGE.
IMAGE DISPLAY, MANIPULATION, STORAGE, COMMUNICATION. AFTER RECONSTRUCTION IMAGE CAN BE DISPLAYED ON THE MONITOR IMAGE CAN BE MANIPULATEDIMAGE CAN BE STORED – ON MOD OR CD. DURING COMMUNICATION PHASE IMAGE MAY BE TRANSMITTED TO A REMOTE LOCATION
Sir Godfrey Newbold Hounsfield CBE, FRS, (28 August 1919 – 12 August 2004) was an English electrical engineer who shared the 1979 Nobel Prize for Physiology or Medicine with Allan McLeod Cormack for his part in developing the diagnostic technique of X-ray computed tomography (CT).FRS28 August191912 August2004English electrical engineerNobel Prize for Physiology or MedicineAllan McLeod CormackX-ray computed tomography
CONSTRUCTION OF FIRST CT RADIATION SOURCE – AMERICUM GAMMA SOURCE SCAN—9 DAYS COMPUTER PROCESSING—2.5 HOURS PICTURE PRODUCTION 1 DAY