ct

• Computed Tomography (CT) scan technology evolution:

  • 1973: Computerized Transverse Axial Scanning introduced in the British Journal of Radiology
  • Radiological Society of North America later accepted the term Computed Tomography
  • Godfrey Newbold Hounsfield developed the first clinical prototype CT Brain scanner (EMI Mark 1) in 1971
  • Allan MacLeod Cormack developed a solution to the mathematical problem in CT in 1963-1964 and later shared the Nobel Prize with Hounsfield
• Types of CT Scanners:

  • First-generation scanner: one or two detectors, 4½-minute scan
  • Second-generation scanner: 30 or more detectors, 40 slices in 10 minutes
  • Third-generation scanner: bank of up to 960 detectors, detectors and x-ray tube rotate 360°
  • Fourth-generation scanner: up to 4800 or more detectors on a fixed ring, only x-ray tube rotates, shorter scan times
• Volume Scanning in CT:

  • Introduced by Dr. Willi Kalender in 1989 with slip-ring technology for continuous 360° rotation
  • Evolution from 1 slice per revolution in 1989 to 320 Slice in 2006-2007
  • Dual Source CT-Scanner introduced in 2006 with 256 slices
• Digital Image Processing in CT:

  • Image digitization involves scanning, sampling, and quantization
  • Analog-to-Digital Conversion improves representation accuracy
  • Image-Processing Techniques include point operations, local operations, and global operations
  • Point Operations involve gray-level mapping, contrast enhancement, and histogram modification
  • Local Operations include spatial location filtering (convolution) and spatial frequency filtering (high-pass and low-pass filtering)
  • Global Operations like Fourier domain processing offer edge enhancement, image sharpening, and restoration
• Radiation Dose Studies in CT:

  • Radiation dose optimization follows the ALARA philosophy for dose reduction
  • Various methods like ionization chambers and thermoluminescent dosimeters are used to measure and describe doses
  • Quality control procedures ensure optimal image quality and minimize artifacts in CT scanners
• Applications of CT Technology:

  • CT fluoroscopy, CT angiography, 3D imaging, virtual reality imaging, and cardiac CT imaging
  • In nuclear medicine, CT scanners are combined with Positron Emission Tomography (PET) and Single-photon Emission Tomography (SPECT) scanners to form PET/CT and SPECT/CT scanners
  • Portable CT scanners are available for remote imaging in operating rooms, intensive care units, and emergency trauma units
• Major Technology Trends in CT:

  • Iterative Reconstruction Algorithms aim to reduce image noise and radiation dose
  • Detector Technologies like solid-state detectors and gas-ionization detectors are crucial for image conversion
  • Spectral CT Imaging uses dual-energy CT for optimal visualization and demonstration of structures
• Characteristics of Digital Images in CT:

  • Digital images are composed of a 2D matrix of numbers representing pixel regions
  • Pixels are square elements with discrete brightness levels
  • Voxels represent tissue volume in digital images
  • Bit Depth determines the color representation accuracy in digital imaging
• Image Digitization Process in CT:

  • Involves scanning, sampling, and quantization for accurate representation
  • Analog-to-Digital Conversion improves signal representation accuracy
  • Image-Processing Techniques include point operations, local operations, and global operations
• Image-Processing Techniques in CT:

  • Point Operations involve gray-level mapping, contrast enhancement, and histogram modification
  • Local Operations include spatial location filtering (convolution) and spatial frequency filtering (high-pass and low-pass filtering)
  • Global Operations like Fourier domain processing offer edge enhancement, image sharpening, and restoration
• Why Digitize Images in CT:

  • Image enhancement, restoration, analysis, compression, and synthesis
  • Image-Processing Techniques include point operations, local operations, and global operations
• Geometric Operations in CT:

  • Modify spatial position or orientation of pixels without affecting pixel intensity
  • Include scaling, sizing, rotation, and translation operations
• Tomos is a Greek/Latin word meaning "section of larger work"
• Radon, an Australian mathematician, probed the possibility to reconstruct a 2D or 3D image from a large number of projections
• Types of CT systems:

  • Emission CT (Nuclear Medicine)
  • Transmission CT (X-ray imaging)
• In 1973, Computerized Transverse Axial Scanning was introduced in the British Journal of Radiology
• Godfrey Newbold Hounsfield, an inventor of computed tomography, was from Nottinghamshire, England
• Dr. Robert Ledley developed the first whole-body CT scanner
• Evolution of terms and how CT scan works
• Dynamic Special Reconstructor was first installed in Mayo Clinic for dynamic function of organs in the Cardiovascular and Pulmonary System
• Dr. Willi Kalender introduced and developed volume spiral CT Scanning in 1989
• Comparison of single and multislice scanners
• Dual-energy CT uses two different x-ray spectra to acquire two image datasets for the same region
• Applications of volume scanning include CT fluoroscopy, CT angiography, 3D imaging, virtual reality imaging, and improved cardiac CT imaging
• CT scanners are combined with Positron Emission Tomography (PET) Scanner and Single-photon Emission Tomography (SPECT) to form PET/CT and SPECT/CT scanners
• CT is effective in diagnosing central nervous system diseases, detecting disorders like gliomas, metastases, and atrophy
• High-speed CT scanners were introduced in 1975
• CT scanners undergo quality control procedures and tests to ensure optimal image quality and minimize image artifacts
• Other uses of CT include internal log defect detection, paleontology, and poultry meat inspection
• Image processing techniques, characteristics of digital images, and image digitization
• Image enhancement, restoration, analysis, compression, and synthesis are reasons for digitizing images
• Image-processing techniques include point operations, local operations, and global operations
• Geometric operations modify the spatial position or orientation of pixels in images
• Analog-to-digital conversion involves dividing a picture into small regions, sampling, and quantization to assign brightness values to gray levels
• Data Acquisition involves collecting patient information, such as electron density and linear attenuation coefficient, for imaging modalities like projection digital radiography and CT, using x-ray tubes and digital image detectors
• Image Processing involves a digital computer processing an input image to produce an output image using the binary number system
• Analog Images are continuous light intensity distributions on radiographs formed when light is focused on film or x-rays are projected onto x-ray film, or through photoelectronic means
• Digital Images are numerical representations of objects created by converting information into digital form using an ADC. The computer processes the data, resulting in digital images that can be displayed
• Digital images are composed of a 2D matrix of numbers, with columns (M) and rows (N) defining pixel regions. The dimension of the image is M, N, and its size is given by the relationship
• Pixels are square elements with discrete brightness levels representing tissue characteristics being imaged