CONT...REVOLUTION OF CT SCANNERS...

SPIRAL/HELICAL CT SCANNER

      This is the latest generation of CT.

        It allows for continuous rotation of the tube for spiral CT

      Spiral CT is made possible by slip-ring technology. 

      The tube can continuously rotate 360 degrees, where it must stop     

        after each rotation with conventional CT

    The detector array may contain as many as 14,600 detectors that are 1.25mm wide.

     

      This allows multiple slice to be made with one scan and more tissue volume to be imaged.

CONT...REVOLUTION OF CT SCANNERS...

 

             FIFTH GENERATION CT SCANNER

Electron beam computed tomography (EBCT)

This 5th generation is uses a flying electron beam, steered electromagnetically and to hit one of the anode strips that encircle the patient. No moving parts, therefore very fast (about 50 ms). It developed specifically for cardiac tomographic imaging

The advantage of this 5th generation ct scan are extremely fast and capable of imaging the beating heart.

The disadvantage of this 5th generation ct scan are high costs and difficult to calibrate, therefore it is not clinically used.

CONT...REVOLUTION OF CT SCANNERS...

THIRD GENERATION CT SCANNER

If one detector fails, a ring artifact will appears.

It is a1 second scan times

It is glad to say that it is superior reconstruction and resolution than 1st and 2nd generation CT scanner.

FORTH GENERATION CT SCANNER

The tube rotates around stationary ring of detectors.

It uses fan beam of the x-ray.

Variable slice thickness with pre and post patient collimation.

Avoids ring artefact problems of 3rd generation scanners.


It uses as many as 8000 detectors.

•1 second scan time.

•Auto-detector calibration so no ring artifact.

•High radiation dose compared to earlier scanners.

will be proceeded to the next post......

Revolution Of CT Scanners....

FIRST GENERATION CT SCANNER

This type of CT generation uses pencil beam.

It is a Translate-Rotate Design with the used of 180 one degree images or translations. 

It also utilizes one or two detectors.

That's why it takes about 5 minutes per scan time.

SECOND GENERATION CT SCANNER

Just like the 1st generation, this 2nd generation CT Scanner was also designed asTranslate-Rotate.

The differences from the 1st generation are : 

1) it applies fan beam collimation so there is more scatter radiation.

2) it uses 5 to 30 detectors.

3)10 degrees /translation 18 per scan, which is about 30 second scan times.

4) it is faster scan time if compared to 1st generation CT scan.

continue........

Basic Principles Of CT Scan

Instead of film, radiation detectors  measure the radiation attenuation as the beam passes through the body.

     The detectors are connected to a computer that uses algorithms to process the data into useful images that are then recorded on film and viewed on a computer monitor.

     

      Conventional tomography has the image parallel to the long axis of the body. This is referred to as Axial Tomography.


      Computed Tomography has the x-ray tube move across the so the image is called a transverse  image or one perpendicular to the long axis of the body.

Computed Tomography...ever heard about it???????

      Computed Tomography is the most significant development in radiology in the past 40 years. MRI and Ultrasound are also significant developments but they do not use x-ray to produce the image. The x-ray tube spins around the patient.

      Godfrey Hounsfield of EMI, LTD demonstrated the principle for computed tomography in 1970. Alan Cormack developed the mathematics used to reconstruct the CT images. They shared the 1982 Nobel Prize for physics.