Imaging using X-rays

When imaging with X-rays, an X-ray beam produced by a so-called X-ray tube passes through the body. On it’s way through the body, parts of the energy of the X-ray beam are absorbed. This process is described as attenuation of the X-ray beam. On the opposite side of the body, detectors or a film capture the attenuated X-rays, resulting in a clinical image. In conventional radiography, one 2D image is produced. In Computed Tomography, the tube and the detector are both rotating around the body during the examination so that multiple images can be acquired, resulting in a 3D visualization.

The most common methods of X-ray in medical imaging are X-ray radiography, computed tomography (CT), mammography, angiography and fluoroscopy.

Fig. 1: Chart comparing typical effective doses of medical examinations with the average natural background radiation.

Fig. 1: Chart comparing typical effective doses of medical examinations with the average natural background radiation.

Different organs and tissues have a different sensitivity to radiation. This is why the actual risk to the body from X-ray procedures varies depending on the part of the body being X-rayed. “Effective dose” is a parameter of the dose absorbed by the entire body that takes account of these differing sensitivities.

Doctors and manufacturers are well aware of the risks and do everything possible to minimize radiation dose. Guided by technical standards that are set and continually updated by national and international radiology protection councils, they take special care during X-ray examinations to use the lowest radiation dose possible while producing the images for. Advanced X-ray systems contain special features that help reduce the radiation dose. For example there are technologies developed to ensure that those parts of a patient’s body not being imaged receive no or only minimal radiation exposure.

  • Fig. 1: The basic setup for X-ray imaging. The collimator restricts the beam of X-rays so as to irradiate only the region of interest. The antiscatter grid increases tissue contrast by reducing the number of detected X-rays that have been scattered by tissue.

    Radiography (Plain X-rays)

    Conventional X-rays have advanced considerably since the earliest radiological imaging and, today, digital X-ray techniques are replacing film.

  • Fig. 1: The principle of computed tomography with an X-ray source and detector unit rotating synchronously around the patient. Data are acquired continuously during rotation.

    Computed Tomography (CT)

    Computed tomography (CT) scanners produce detailed images of the body. Due to their high resolution, these images can provide additional information compared to conventional radiography.

  • Fig. 1: In mammography each breast is compressed horizontally, then obliquely and an X-ray is taken in each position


    Mammography is a special type of X-ray imaging used to create detailed images of the breast and is commonly used in screening for breast cancer.

  • Fig. 1: Angiogram of a blood vessel in the region of the knee.


    Angiography is a specific type of X-ray technique for viewing blood vessels and organs, especially the heart, by injecting a contrast agent into the blood that enhances its visibility on the X-ray image.

  • fluoroscopy


    Fluoroscopy is a type of medical imaging that produces a continuous ‘live’ X-ray image of the patient’s internal structures on a monitor.

Last updated: Nov 9, 2011

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