Computed Tomography and Radionuclide Imaging

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Introduction

Computed tomography (CT) and Radionuclide imaging (RNI) are both a form of diagnostic imaging. Since they have been first introduced in medical imaging they both suffered a huge development over the years in terms of image acquisition and also patient radiation protection. The following essay it is going to focus on just a few important things that make CT and RNI similar and different in the same time. However this subject can be discussed in much depth, the focus is going to be on the similarities and differences of the physics imaging methods and also a small awareness of biological effects and radiation protection.

As a starting point in CT diagnostic imaging the form of radiation used to provide an image are x-rays photons , this can also be called an external radiation dose which detect a pathological condition of an organ or tissue and therefore it is more organ specific. However the physics process can be described as the radiation passes through the body it is received by a detector and then integrated by a computer to obtain a cross-sectional image (axial). In this case the ability of a CT scanner is to create only axial two dimensional images using a mathematical algorithm for image reconstruction. In contrast in RNI the main property for producing a diagnostic image involves the administration of small amounts of radiotracers or usually called radiopharmaceutical drugs to the patient by injection or oral. Radio meaning the emitted of gamma rays and pharmaceutical represents the compound to which a nuclide is bounded or attached. Unlike CT has the ability to give information about the physiological function of a body system. The radiopharmaceutical often referred to as a nuclide has the ability to emit ga...

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...s in one direction to acquire a single image slice. For another slice to be imaged the x-ray tube would again rotate another 360 degrees but on opposite direction. However this has been changed over the years and has been implemented a Slip-Ring technology which replaced the old high tension cables. In this way the new CT scanner x-ray tube had the ability to rotate continuously around the patient and in the same time the table was moving through the gantry to acquire data in a form of a Spiral or Helical. Therefore the new generation of CT scanners is called Spiral or Helical CT. The advantages of the new scanners are that the volume data can be reconstructed in any other planes (sagittal, coronal and three dimensional images), also there is a short time scan therefore radiation to the patient is minimized and also the artefact caused by patient motion is reduced.

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