Imaging procedure is a generic term for various apparative diagnostic methods in medicine. Commonly used imaging methods are X-ray and ultrasound diagnosis.
What is an imaging procedure?
Imaging procedure is a generic term for various apparative diagnostic methods in medicine. Commonly used imaging methods are X-ray and ultrasound diagnosis. In almost all medical specialties, various apparative imaging methods are used to image organs and tissue structures of the patient. The resulting two- or three-dimensional images provide important information for the diagnosis of diseases. It is therefore impossible to imagine today’s medicine without the diagnostic imaging procedures.
Function, effect, and goals
As early as 1895, X-rays, a high-energy electromagnetic radiation, were discovered by Wilhelm Conrad Röntgen and have been used in the diagnosis of diseases ever since. Today, radiology plays an important role, especially in trauma medicine and in the diagnosis of lung diseases. A so-called X-ray tube serves as the radiation source in X-rays. The radiation leaves the X-ray machine and hits the X-ray film or, in more modern radiography, an X-ray storage film or electronic sensors. This is where the actual X-ray image is produced. The patient stands between the X-ray machine and the X-ray film. The X-rays strike the patient’s body and are absorbed there to varying degrees, depending on the nature of the tissue in question. The part of the radiation that has penetrated the body and has not been absorbed hits the X-ray film. The different levels of absorption, and thus the shadows and brightenings that appear on the X-ray film, make it possible to create images of the body’s structures. For example, X-ray dense tissues, such as bone, allow only a small amount of radiation to pass through. The X-ray film is only slightly blackened and the bones appear bright in the X-ray image. Patients are often given contrast agents before the X-ray. This allows structures to be made visible that would otherwise be difficult to delineate. A modern X-ray procedure is computed tomography. In this imaging procedure, the body is X-rayed layer by layer. A computer then creates a cross-sectional image of the body. Contrast agents are also used here to provide a more meaningful image. An important field of application of computed tomography is neurological diagnostics. Thus, CT is used in cases of suspected tumor, craniocerebral injury or stroke. Computed tomography is also used to search for metastases in cases of known cancer. Another imaging technique is magnetic resonance imaging, also known as nuclear spin or MRI for short. MRI also allows slice-by-slice imaging, but does not use ionizing radiation for this purpose; instead, it is based on the principle of nuclear magnetic resonance. The basis of magnetic resonance imaging is the spin of atomic nuclei with odd numbers of protons or neutrons. These atomic nuclei rotate independently and thus have what is known as spin. This physical property makes them magnetic. In the normal state, these spins are present in a disordered fashion. However, when a strong magnetic field is applied in MRI, all atomic nuclei align in parallel. Short radio frequency pulses disrupt the alignment of the atomic nuclei. When they return to their original state, the atomic nuclei emit electromagnetic waves that are registered by special sensors. From these electromagnetic waves, the computer then creates an analyzable image that shows the body structures in layers. MRI is used primarily for the diagnosis of CNS disorders. Ultrasound diagnostics, also known as sonography, is based on the fact that ultrasound is partly absorbed and partly reflected by human tissue. The ultrasound waves are generated by a transducer and transmitted at short intervals or as continuous sound. In order to avoid disturbing air bridges, a gel is used as a transmission medium. The sound waves reflected by the tissues are picked up again as an echo by the transducer. An image is generated by further electronic processing within the ultrasound device.Sonography is used as a diagnostic tool primarily for thyroid disorders, abdominal complaints and for clarifying diseases affecting the heart. Ultrasound is also used for prenatal care. Ultrasound does not produce any radiation. In addition, the examination is painless. A variation of sonography is the Doppler method. Here, the ultrasound probe constantly emits waves. If these waves hit moving surfaces, e.g. the cell wall of a blood cell, the waves are reflected. When the transmitted and reflected waves collide, a sound is generated. This is made audible by amplification. The Doppler method is used, for example, during pregnancy. The procedure is used to monitor the heartbeat of the child. Doppler ultrasound is also used in vascular medicine to test flow conditions in arteries or veins.
Risks, side effects, and hazards
For the body, X-ray is the most harmful imaging procedure. Radiation doses in radiology are quite low, but can cause damage within a shorter period of time, especially with repeated X-rays. Around one and a half percent of annual cancer cases are said to be due to radiation exposure from X-ray diagnostics. A study in the journal “Cancer” reported that the risk of contracting a brain tumor is greatly increased by regular X-ray examinations at the dentist. In children, the risk of a brain tumor even increased fivefold due to dental X-ray diagnostics. Scientists agree that X-ray examinations, including computer tomography, should be reduced to a necessary minimum. For this purpose, the X-ray passport was introduced in Germany. All of the patient’s X-ray examinations are recorded here in order to avoid nonsensical and duplicate examinations. X-rays are absolutely contraindicated in pregnant women, as they can harm the unborn child. Magnetic resonance imaging and ultrasound do not use radiation and are therefore considered well tolerated.