Mobile CT
Computed Tomography
Computed Tomography (CT), also known as Computed Axial Tomography (CAT), is a medical imaging technique that uses X-ray technology to create detailed cross-sectional images of the body.
Key Components
X-ray Tube
Function: The X-ray tube generates X-rays, which are emitted in a controlled manner through the patient’s body.
Rotation: It rotates around the patient, emitting X-rays from various angles to capture comprehensive data.
Detector Arrays
Function: Detectors capture the X-rays that pass through the body. They are positioned opposite the X-ray tube in a ring or array.
Materials: Detectors are typically made from scintillation materials like bismuth germanate (BGO) or lutetium oxyorthosilicate (LSO), which convert X-ray photons into visible light and then into electrical signals.
Gantry
Structure: The gantry is the large, circular part of the CT scanner that houses the X-ray tube and detectors. It rotates around the patient during the scan.
Features: It includes mechanical components that enable the rotation of the X-ray tube and detector array, as well as the movement of the patient table through the gantry.
Patient Table
Function: The table moves the patient through the gantry. It is motorized to allow precise control over the movement during the scan.
Movement: The table can move in and out of the gantry and, in some designs, along the Z-axis (longitudinal direction).
Control Console
Function: The control console is used by the radiologic technologist or radiologist to operate the CT scanner, set scan parameters, and monitor the scan process.
Software: It includes software for planning scans, adjusting scan parameters, and managing patient data.
Computer System
Function: The computer system reconstructs the raw data from the detectors into cross-sectional images. It performs complex algorithms to process and analyze the data.
Reconstruction Techniques: Common techniques include filtered back projection and iterative reconstruction. These methods help convert the X-ray data into detailed images.
Operational Principles
X-ray Generation and Detection
X-ray Emission: During a CT scan, the X-ray tube rotates around the patient, emitting a beam of X-rays. The X-rays pass through the body and are attenuated differently by various tissues (e.g., bone, muscle, fat).
Detection: Detectors measure the X-rays that pass through the body. The intensity of the X-rays detected varies based on the density and composition of the tissues they pass through.
Data Acquisition
Data Collection: The detectors convert the X-ray photons into electrical signals, which are then digitized. This data represents the attenuation of X-rays through different tissue densities.
Projection Data: Multiple X-ray projections are collected from different angles around the body, providing comprehensive information on the tissue densities.
Image Reconstruction
Algorithms: The digitized data is processed using algorithms to reconstruct cross-sectional images (slices) of the body. The images represent the internal structure based on the differential attenuation of X-rays.
Slice Thickness: The thickness of the slices can vary, typically ranging from 0.5 to 5 mm, depending on the scan protocol and the desired level of detail.
Image Processing and Visualization
Post-Processing: The reconstructed images can be enhanced, manipulated, and analyzed using various post-processing techniques. This includes adjusting contrast, zooming, and generating 3D reconstructions.
Display: Images are displayed on high-resolution monitors for interpretation by radiologists. Advanced visualization tools help in assessing and diagnosing conditions.
Safety and Operational Considerations
Radiation Dose: CT scans involve exposure to ionizing radiation. Efforts are made to minimize the radiation dose while ensuring diagnostic quality. Techniques like dose modulation and optimization are used to reduce exposure.
Contrast Agents: Sometimes, iodinated contrast agents are used to enhance the visibility of certain structures or abnormalities. These agents are injected into the bloodstream or administered orally, depending on the type of scan.
Patient Preparation: Preparation may include fasting, hydration, or the administration of oral contrast agents, depending on the type of scan and the area being examined.
In summary, a CT scanner combines X-ray technology with advanced computer algorithms to produce detailed cross-sectional images of the body. It is a crucial tool in medical diagnostics, providing clear views of internal structures and helping in the diagnosis and monitoring of various conditions.