Computed Tomography (CT) is an imaging modality that has revolutionized the field of medical imaging. It provides detailed and accurate images of internal structures of the body that were previously impossible to visualize. The basic principle of CT involves using X-rays to produce multiple cross-sectional images of the body, which are then reconstructed into a 3D image. In this article, we will delve into the basics of the technical principles of CT, mathematics involved, and image reconstruction.
The Basic Principles of CT
The fundamental principle of CT is based on the interaction of X-rays with matter. When an X-ray beam passes through the body, it is attenuated to varying degrees depending on the tissue through which it passes. The amount of attenuation is measured by a detector, which produces an electrical signal proportional to the amount of radiation detected. The detector is mounted opposite to the X-ray source, and both are rotated around the patient. By capturing multiple projections of the body from different angles, CT can provide a detailed image of the internal structures.
Image reconstruction
In CT, the X-ray source emits a fan-shaped beam of X-rays that pass through the patient's body and are detected by a set of detectors placed opposite the source. The detectors measure the intensity of the X-rays that pass through the body at various angles, producing a set of 1D projections that represent the attenuation of X-rays along a line through the body.
These projections are then combined to form a 2D image of the internal structures of the body. The Radon transform is used in the reconstruction process to convert the set of 1D projections back into a 2D image. The full mathematics involved in the image recons process is beyond the scope of this article and will be explained in other articles. But to get a good grasp of the topic, I highly recommend to read the chapter on CT Scan of the book, "Digital Image Processing (Book by Rafael C. Gonzalez and Richard E. Woods )"
Common Applications of CT Scan
CT is widely used in oncology, neurology, and cardiology, as well as in trauma and emergency medicine. It is an essential tool for the diagnosis and management of cancer, heart disease, stroke, and other conditions.
Summary
Computed tomography is a valuable imaging modality that has revolutionized the field of medical imaging. It is based on the principle of using X-rays to produce multiple cross-sectional images of the body that are reconstructed into a 3D image. The mathematical foundation of CT is the Radon transform, which is used to calculate the attenuation of X-rays along a line that passes through the body. The reconstruction process involves using filtered back projection to convert the sinogram data into a 3D image. CT has numerous applications in clinical practice and is an essential tool for the diagnosis and management of a wide range of medical conditions.
