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Ct scan

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Rabia Iqbal

CT or CAT scanners use X-rays and computer technology to create cross-sectional images of the body. Godfrey Hounsfield invented the first commercially viable CT scanner in 1967. A CT scanner is composed of a gantry with an X-ray tube that rotates around the patient, detectors, and a data system. X-rays pass through the body and are measured by detectors. A computer uses reconstruction algorithms to generate images from the data. CT scans provide detailed images and have advantages like detecting multiple types of tissues, being fast and painless, and helping diagnose many conditions.

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Rabia iqbal 2013-BM-114
Computed tomography (or computerized axial tomography) is an examination that uses X-ray and computer to obtain a cross- sectional images of the human body.
The first commercially viable CT scanner was invented by Godfrey Newbold Hounsfield in Hayes, England at Thorn EMI Central Research Laboratories using X-rays. Hounsfield conceived his idea in 1967, and it was publicly announced in 1972.
CT Scanner Gantry Data Acquisition System Operating Console
The gantry assembly is the largest of these systems. It is made up of all the equipment related to the patient, including the patient support, the positioning couch, the mechanical supports, and the scanner housing. It also contains the heart of the CAT scanner, the x-ray tube, as well as detectors that generate and detect x rays.
High Voltage Generator X-ray tube Pre Patient Collimator Patient Post Patient Collimator Detector X ray source Pre Patient Collimation Post Patient Collimation X-ray Detector
Two types of detectors are used Scintillation Detectors Gas Filled Detectors Scintillation Detectors Materials Used Sodium Iodide Bismuth Germanium Oxide Cesium Iodide Cadmium Tungstate Scintillator Crystal Photo Multiplier Detector Rings
Gas Filled Detectors Materials Used Xenon Krypton Xenon + Krypton Since 90% of 50 is 45, the output is same. The overall efficiency of both the detectors is same. Gas Filled Detectors Scintillation Detectors Sensitive face: 100% Detection Efficiency: 45% Sensitive face: 50% Detection Efficiency: 90%
The DAS consists of the following parts X-ray photons come on the detector. The detector detects the intensity in form of current. The current is converted into voltage. The analog integrator removes spikes. The analog signal is converted into digital form. This signal can now be processed and reconstructed in the computer. Detector Current to Voltage Convertor Pre Amplifier Analog Integrator Analog to Digital Convertor Computer
After enough transmission measurements (detector) Sent to the computer for processing A software called Fourier Slice Transform is used. More than 250,000 reconstruction algorithms are used (example: algebraic reconstruction technique) to compute the image.
The operating console is the master control center of the CAT scanner. It is used to input all of the factors related to taking a scan. Typically, this console is made up of a computer, a keyboard, and multiple monitors. Often there are two different control consoles, one used by the CAT scanner operator, and the other used by the physician. The operator's console controls such variables as the thickness of the imaged tissue slice, mechanical movement of the patient couch, and other radiographic technique factors.
Ct scan
generation configuration detector beam Min scan time first Translate -rotate 1-2 Pencil thin 2.5min second Translate -rotate 3-52 Narrow fan 10sec Third Rotate- rotate 256-1000 Wide fan 0.5sec fourth Rotate- fixed 600-4800 Wide fan 1sec fifth Electron beam 1284 Wide fan electron beam 33ns Generations of CT scan
Advantages First ,CT completely eliminates the superimposition of images of structures outside the area of interest. Second, because of the inherent high-contrast resolution of CT, differences between tissues that differ in physical density by less than 1% can be distinguished. Third, data from a single CT imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as images in the axial, coronal, or sagittal planes, depending on the diagnostic task. This is referred to as multiplanar reformatted imaging.
CT scanning is painless, non- invasive and accurate. A major advantage of CT is its ability to image bone, soft tissue and blood vessels all at the same time. Unlike conventional x-rays, CT scanning provides very detailed images of many types of tissue as well as the lungs, bones, and blood vessels. CT examinations are fast and simple; in emergency cases, they can reveal internal injuries and bleeding quickly enough to help save lives. CT has been shown to be a cost-effective imaging tool for a wide range of clinical problems. CT is less sensitive to patient movement than MRI. Benefits Vs. Risks
Ct scan

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Ct scan

  • 2. Computed tomography (or computerized axial tomography) is an examination that uses X-ray and computer to obtain a cross- sectional images of the human body.
  • 3. The first commercially viable CT scanner was invented by Godfrey Newbold Hounsfield in Hayes, England at Thorn EMI Central Research Laboratories using X-rays. Hounsfield conceived his idea in 1967, and it was publicly announced in 1972.
  • 5. The gantry assembly is the largest of these systems. It is made up of all the equipment related to the patient, including the patient support, the positioning couch, the mechanical supports, and the scanner housing. It also contains the heart of the CAT scanner, the x-ray tube, as well as detectors that generate and detect x rays.
  • 6. High Voltage Generator X-ray tube Pre Patient Collimator Patient Post Patient Collimator Detector X ray source Pre Patient Collimation Post Patient Collimation X-ray Detector
  • 7. Two types of detectors are used Scintillation Detectors Gas Filled Detectors Scintillation Detectors Materials Used Sodium Iodide Bismuth Germanium Oxide Cesium Iodide Cadmium Tungstate Scintillator Crystal Photo Multiplier Detector Rings
  • 8. Gas Filled Detectors Materials Used Xenon Krypton Xenon + Krypton Since 90% of 50 is 45, the output is same. The overall efficiency of both the detectors is same. Gas Filled Detectors Scintillation Detectors Sensitive face: 100% Detection Efficiency: 45% Sensitive face: 50% Detection Efficiency: 90%
  • 9. The DAS consists of the following parts X-ray photons come on the detector. The detector detects the intensity in form of current. The current is converted into voltage. The analog integrator removes spikes. The analog signal is converted into digital form. This signal can now be processed and reconstructed in the computer. Detector Current to Voltage Convertor Pre Amplifier Analog Integrator Analog to Digital Convertor Computer
  • 10. After enough transmission measurements (detector) Sent to the computer for processing A software called Fourier Slice Transform is used. More than 250,000 reconstruction algorithms are used (example: algebraic reconstruction technique) to compute the image.
  • 11. The operating console is the master control center of the CAT scanner. It is used to input all of the factors related to taking a scan. Typically, this console is made up of a computer, a keyboard, and multiple monitors. Often there are two different control consoles, one used by the CAT scanner operator, and the other used by the physician. The operator's console controls such variables as the thickness of the imaged tissue slice, mechanical movement of the patient couch, and other radiographic technique factors.
  • 13. generation configuration detector beam Min scan time first Translate -rotate 1-2 Pencil thin 2.5min second Translate -rotate 3-52 Narrow fan 10sec Third Rotate- rotate 256-1000 Wide fan 0.5sec fourth Rotate- fixed 600-4800 Wide fan 1sec fifth Electron beam 1284 Wide fan electron beam 33ns Generations of CT scan
  • 14. Advantages First ,CT completely eliminates the superimposition of images of structures outside the area of interest. Second, because of the inherent high-contrast resolution of CT, differences between tissues that differ in physical density by less than 1% can be distinguished. Third, data from a single CT imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as images in the axial, coronal, or sagittal planes, depending on the diagnostic task. This is referred to as multiplanar reformatted imaging.
  • 15. CT scanning is painless, non- invasive and accurate. A major advantage of CT is its ability to image bone, soft tissue and blood vessels all at the same time. Unlike conventional x-rays, CT scanning provides very detailed images of many types of tissue as well as the lungs, bones, and blood vessels. CT examinations are fast and simple; in emergency cases, they can reveal internal injuries and bleeding quickly enough to help save lives. CT has been shown to be a cost-effective imaging tool for a wide range of clinical problems. CT is less sensitive to patient movement than MRI. Benefits Vs. Risks