Basic of CT- scan Generation / Radiology

describe Ct scan history and genration

1. Ashutosh Mishra

2. COMPUTED TOMOGRAPHY Invented by Sir Godfrey N Hounsfield in 1971. It is special form of tomography in which a computer is used to mathematical reconstruction of a T omographic plane or slice. It generates images in transaxil section . Tomo – Cut/slice , Graphy - Images.

3. FIRST GENERATION Designed in 1971 only for evaluation of the Brain. Narrow Pencil Beam . Single Detector per Slice. Translate and rotate movement. Scan time 30 min.

4. SECOND GENERATION Designed in 1974 It is also used only for evaluation of the Brain . About 30 detectors are used. Narrow and fan beam. Linear detector array. Translate and rotate movement. Scan time 20-25 sec.

5. THIRD GENERATION Designed in 1975 by GE healthcare. It is used for whole body scan. Wide and fan beam. Rotate and rotate movement. Tube and detectors array are mechanically joint and rotate together. Number of detectors increased (>800) Detectors made up with xenon and scintillation . Scan time 5 sec.

6. Slip ring SLIP RING ARTIFACT- Its Disadvantage of third generation , Any drift or failure of single detectors are causing Ring artifact .

7. SLIP RING TECHNIQUE- In all generations gantry needs to be stopped to change projection , to over come this problem slip Ring Technique was introduce. It is electromechanical device that conduct continually rotation of gantry. The tube can continuously rotate 360 degree with continuous movement of couch within gantry. Three type of slip ring- 1 st slip Ring- Provide high voltage power to x ray tube. 2 nd Slip Ring- Provide low voltage to control system on rotating gantry. 3 rd Slip Ring- Transfer data from rotating detectors array .

8. FOURTH GENERATION Designed in 1976 . Wide and fan beam. Rings of detectors. Rotate and stationary movement. Scintillation detectors. Scan time 2 Sec.

9. FIFTH GENERATION Designed in 1979-80 . Also name of the generation EBCT/CVCT. Scan time- 50mSec. Its used for cardiac imaging. Component :- Electron Gun. EM Coils. Tungsten Target. Stationary Couch Detectors.

10. SIX GENERATION Designed in 1990. Also called Helical /Spiral CT. Based on Third and fourth + Slip ring +helical motion. X-ray tube move continuously. Scan reconstructed at any desired position. Multiple detectors are used.

11. SEVENTH GENERATION Designed in 1998 . Also called multi slice CT scan. Based on T hird Generation + slip ring technique. X-Ray with slip ring . Multi detectors array.