CT image acquisition

CT image acquisition

1. CT IMAGE ACQUISITION Kezia Tyagi CT IMAGE ACQUISITION DR . Pradeep Patil Prof . Department of Radio-diagnosis, DY Patil medical college, hospital & research institute Kolhapur

2. Introduction to ct Invented in 1972 by Godfrey Hounsfield First CT scanner was installed between 1974- 1976 Overtime, many improvements have been made in speed, patient’s comfort and resolution. Tomographic Slice Scintillation detector Analysis Reconstruction

3. CT generations First Generation Second Generation Multiple detectors (Around 30) are arranged in a row, translation and rotation movement, fan beam is used.

4. Third Generation Fourth Generation

5. ct acqusition process

6. image acquisition A method by which the patient is systematically scanned by the x-ray tube and detectors to collect information for image reconstruction

7. overview of process 1) Patient preparation 2) Patient positioning 3) X-Ray tube rotation 4) Data Acquisition 5) Image Reconstruction

8. components of ct scanner 1) X-ray Tube Source of x-rays radiation source should supply a monochromatic x-ray beam Earlier CT scanners used radionuclides Earlier x-ray tube models used oil-cooled fixed anode, large spot tubes of about 120kV and 30 mA New fan beam units

9. components of CT scanner 2) Detector Array series of sensors that detect the x-rays 2 types: Scintillation Crystals Xenon gas ionization chambers

10. components of ct scanner 3) Collimator Used to reduce the size and shape of the beam as well as remove the scattered photons. Types: Pre-Patient Post- Patient

11. components of Ct scanner 3) Gantry large circular structure that houses the x-ray tube and detector array. rotates around the patient during scan to capture x-ray projections from multiple angles. 4) Patient table long narrow bed that patient lies on during the scan can be moved horizontally or vertically to position the area of interest within the scanner’s field of view.

12. components of ct scanner 5) Computer “brain” of the CT scanner receives data and uses algorithims for image reconstruction 6) Console control center of the CT scanner

13. process of image acquisition

14. x-ray Generation x-rays produced when high energy electrons are accelerated and collide with metal target X-ray beam is produced, detected and converted into electrical signals x-ray tube consists of cathode and anode. Collimation Dosing

15. Analog- to - digital conversion converts analog signals produced by the detector array into digital signals that can be processed by the computer system of the CT scanner. Continous electrical signals varying in ampltitude Data Acquisition System

16. DAta Collection Collects the digital signals produced by ADC and organizing them into matrix of data points. As the x-ray beam beam passes through the patient’s body, it is absorbed to varying degrees by different tissues, producing a unique pattern of x-ray attenuation that is detected by the detector array. Divided into three stages: Pre-scan Scan Post Scan

17. In computed tomography a cross-sectional layer of the body is divided into many tiny blocks Each block is assigned a number proportional to the degree that the block attenuated the x-ray beam. Individual blocks are called voxel. Their composition and thickness, along with the quality of the beam, determine the degree of attenuation

18. Types of CT Scans Helical Multislice Cone Beam Dual Energy

19. Data processing Raw data is processed by the CT scanner’s computer system to produce a series of cross-sectional images. has 3 substeps : Image reconstruction Image enhancement Image analysis

20. Image reconstruction Involves- Filtering backprojection interpolation

21. Thank you