However, we would like to ask all visitors to inform us of any errors of omission or commission. We realize that many valuable items could have been overlooked. This material has previously been published in various journals and books we have made every attempt to reproduce this information accurately and to cite references. "Normal measurements in pediatric radiology" is being compiled by pediatric radiologists from several teaching hospitals across North America. This website will demonstrate a developing database which includes selections of all major organ systems and all imaging modalities. This site is intended to allow the information to be accessible to any radiologist with internet access. However, normal measurements are not always easily accessible to radiologists in their daily practice. This is particularly true in pediatric radiology, where normal growth and development create a broader spectrum of normal values. Comparison to Other Imaging Techniquesīelow is a summary table of the common imaging modalities.Knowledge of normal anatomy and its variants is critical in diagnostic radiology. Fig 2 - Illustration of the mediastinal structures in a normal chest radiograph. In this article, we shall look at the basic science underpinning x-rays, and the principles of their interpretation. Plain film x-ray is the most common diagnostic radiological modality used in hospitals today. They were first discovered and used for imaging purposes by Wilhelm Röntgen on 8th November 1895, when he took an image of his wife's hand. Depending on the tissue being imaged, the urgency of the investigation and the level of detail required, any of these techniques may be preferred: Factor There are CT scanners available on the market now that offer radiation dosage levels as low as plain film X-rays.īelow is a summary table of the common imaging modalities. However, plain film X-rays procedures are being replaced by CT and MR due to advancements in technology. They are often used as an initial screening to rule out anything obvious before an advanced modality is used such as CT or MR. It offers lower dosage compared to CT, and certain studies are performed relatively quickly (Chest X-rays). The biggest advantage with plain film X-rays is the amount of radiation involved. These receptors are placed behind the patient to capture the x-ray photons that are transmitted through the patient and ultimately form the image. With technological advancements, many instutions will be using a cassette receptor or if newer technology is available, a digital plate receptor may be used instead. Traditionally, radiographic film was used known as double emulsion film containing silver nitrate. These X-rays then travel through a focusing cup, focusing and accelerating the photons towards the area of the body to be imaged. Energy levels of the X-ray photon will vary and can be adjusted when selecting a parameter known as kVP or kilovolts peak. One of these interactions causes electrons to be expelled from the outer orbits of the atoms releasing a X-ray photon. When the electrons collide with the tungsten, several interactions occur at the atomic level. The electrons emitted by the cathode rush towards the anode, which holds a disc made of tungsten. This process is known as thermionic emission. These electrons are emitted from a filament on the cathode and rush towards a target material known as the anode. This causes electrons to “boil-off” from the cathode end of an X-ray tube assembly. The radiation is created when an electric current is generated from a high voltage generator.
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