X-ray, what it is and what it is used for

Making the invisible visible: the extraordinary power of X-rays was discovered in 1895 by Wilhelm Conrad Röntgen, the physicist who described its properties by “impressing” his wife’s hand on film. An invention that changed the history of medicine and that, in its essential characteristics, has remained the same to this day, as often happens to truly revolutionary ingenuity products.

“Radiography is an examination that is part of diagnostic imaging and uses ionizing radiation, the famous X-rays, which pass through the patient’s body and allow to obtain information on internal organs“, explains Luca Sconfienza, head of the Diagnostic and Interventional Radiology Unit at the IRCCS Galeazzi Orthopedic Institute and full professor of Diagnostic Imaging and Radiotherapy at the University of Milan.

“X-rays very easily pass through soft tissues – such as muscles or abdominal organs – that is, those that offer low resistance to the passage of radiation, while they pass more difficult hard tissues, such as bones and teeth that are so very highlighted and can be studied easily. And this is why bones were the first field of application of radiography, where it continues to be widely used.”

However, there are also other areas of use: “For example, in the study of the lungs: the large amount of air they contain works as a natural contrast medium for the lung tissue, allowing to highlight the presence of nodules or thickenings that can be a sign of a pathology”.

From a conceptual point of view, radiography is still the same as at the end of the nineteenth century: “As it was invented, it arrived until 2020, without substantial changes”, confirms the expert. “However, a series of technical aspects have evolved: in the past, slightly modified radiographic films were used, which today have been replaced by digital equipment – software and hardware exactly like those of a mobile phone – which report the images on an electronic device, that is, the screen of a computer. The advantage is, as with all digital images, that X-rays can be stored forever, without the risk of damage. But, above all, this has made it possible to drastically reduce the dose of radiation that is administered to the patient, also significantly improving the quality of the examination itself».

The principle of making the invisible visible, in short, remains unchanged. What has changed have been the tools through which the image obtained is displayed, which have evolved hand in hand with the technology in common use. And so, even in the hospital, the photographic film plate has given way to more innovative reports, such as CDs and DVDs.

The fields of use of radiography

“The radiographic investigation is always the first in the study of the lung, as has become evident even during the pandemic”, continues Luca Sconfienza. “The air that acts as a contrast medium allows to highlight even minimal alterations, for example the presence of interstitial pneumonia or common pneumonia, as well as nodules, which can be possible indicators of tumors, pleural effusion and so on. The radiogram also plays a fundamental role in the study of the musculoskeletal system because the bones have an excellent contrast with the surrounding tissues and therefore represents the first diagnostic approach in the case of osteoarthritis or fractures. It is the first choice examination because it has a very low economic and biological cost: compared to the CT scan, the radiation dose is a hundred times lower, compared to a very good diagnostic result in some areas».

Lung disorders and degenerative changes, however, are not the only pathologies for which this diagnostic method is effective. The radiographic examination, in fact, is also used in the following cases:

• in the examination of stones, perforations, inflammatory states and alterations of the abdomen;
• in the diagnostic deepening of suspected inflammatory alterations (arthritis);
• in case of trauma and injury;
• in the field of dental health.

The reading of the radiography is possible thanks to the process of “attenuation of the radiation beam”: “In simple words, there are tissues that let more radiation pass and tissues that let less of it through, and the difference resembles that between sunglasses and prescription glasses: the latter let all the light through, While the former are more “dense”, they let less light through and therefore protect our eyes. The radiologist who examines the X-ray goes to look for these differences in opacity: in a lung that should be transparent, because the air does not retain X-rays but lets them through, if there is a clearer area, more “radio-opaque” in technical terms, there may be a thickening or a lump. In the same way, the bone is normally a continuous white spot: if the radiography shows areas with a different density, therefore a different attenuation of the radiation beams, it is possible that there is a pathology. In short, there are a series of specific “signs”, depending on the body district concerned, which the expert interprets and reports to the specialist (pulmonologist, orthopedist, surgeon, sports doctor, etc.).

The accuracy of the examination depends very much on the operator, and therefore on the experience of the radiologist: “This applies in general to all medical techniques or methods, including laboratory tests. More than in the execution of the radiography, for which there are standard technical guidelines, the type of equipment with which it is performed is important, because it affects its quality, and the experience of the operator who reads the examination. Radiology embraces many specialties, so the radiologist is trained to read an examination of both the chest and the femur, but since human pathology is very vast, it is clear that there are centers and radiologists more specialized in one field than in another. An element that must be considered to obtain an examination that is as accurate as possible: depending on the need, it is good to contact a center of excellence for orthopedic or pulmonary pathology and so on».

X-ray, CT scan or resonance?

Radiography remains irreplaceable despite the fact that today we have diagnostic imaging techniques – ultrasound, resonance, CT scan, etc. – that may seem more advanced: «Meanwhile, it is not, as many think, “more in-depth examinations” or “more accurate”: if anything, for each diagnostic question there is a more appropriate examination», explains Luca Sconfienza. “CT scan of the lung may be more accurate than chest X-ray in the study of a specific pathology, but the most technologically advanced machine is not always “better” than the basic investigation. X-rays remain indispensable in many cases for the reasons already pointed out, namely low cost and low dose of radiation. A persistent cough may require an investigation for a suspected pneumonia, and in this case an X-ray is more than enough to confirm or disprove. In case of more nuanced symptoms, a more sophisticated examination, such as a CT scan, may be necessary. The same applies to MRI: it can be the first examination in a young athlete with knee pain and a suspected injury at an early stage, for example of cartilage; But for the sedentary adult or the elderly with a similar problem in which the most likely cause is a degenerative arthritic disease, the radiography is the correct examination from which to start the diagnostic investigation».

It is true, however, that the advent of new technologies and methods, such as CT, CT, and digital radiology, has made the use of radiography carried out with contrast medium almost completely outdated, which remains confined to some areas and in a few cases. It is still used for the digestive tract, for example, whose examination requires the administration – orally, intravenously or rectally – of a substance, the radiopaque contrast medium, capable of making the tissues of the esophagus, stomach and duodenum “whiter”.

On the other hand, the role and usefulness of X-rays in the diagnosis and prevention of breast cancer remain undisputed, so mammography continues to be used both in screening campaigns and in specialist visits.

In general, since (unlike the dreaded endoscopy) radiography is a quick and painless examination, minimally invasive, patients “like” it and sometimes they themselves request it from the general practitioner. But are there also cases in which it is not the right one? “They are rare, and concern a selected percentage of patients. In 90% of cases where a diagnostic imaging test is required, radiography is appropriate as the first choice,” replies the radiologist. “There are cases, however, in which radiology, and diagnostic imaging in general, are not needed. For example, in the case of back pain: a known fact is that for a generic low back pain, an X-ray in the first 6-8 weeks from the onset of pain does not modify the therapy because it does not provide relevant information.

Contraindications

Are there any contraindications to radiography or its frequent repetition, as happens in the case of Moc to assess the state of bone health for those suffering from osteoporosis? “In everyday life we are already exposed to a certain amount of environmental radiation, which corresponds to about fifty chest X-rays a year. In general, there is attention to radiation protection and there is an ad hoc legislation, Law 101 of 2020, which protects patients: all exposures to ionizing radiation must be justified and the exposure must be optimized, that is, the least amount of radiation necessary to make the diagnostic examination must be used. From a practical point of view, the dose is globally very low and therefore if there is an indication to an X-ray there is no need to worry, and so even if an annual check for a pathology is necessary. The same applies to the Moc (Computerized Bone Mineralometry), which is repeated every 18-24 months and provides an amount of radiation about fifty times lower than those necessary for a chest X-ray».

In general, there are a series of assessments that take into account sex, age, reproductive health, life expectancy and so on: for example, there are legal limits that establish that the pregnant woman should not be subjected to diagnostic investigations with radiation, to protect the embryo and the fetus. “But there are considerations on the single event: if the pregnant patient has knee pain, probably the x-ray can be postponed until after delivery; But if the woman has a car accident that causes her a serious danger, the need for an X-ray must be assessed in the specific case. Finally, taking into account that any harmful effects of radiation can occur even after years, particular caution is applied in young subjects and in particular in girls to protect their reproductive health.

Some practical advice

It must be reiterated: the radiological examination is not a painful or invasive procedure.

Depending on the part of the body to be examined, it can be performed in an upright position (chest X-ray) or supine (renal X-ray), lying on one side (RX lumbosacral spine) or sitting (RX foot).

It does not require any physical preparation, except in special cases (such as for the abdomen) for which, however, the structure where the reservation is made provides specific instructions through brochures and dedicated web pages.

The only precaution to have is to remove clothing and metal objects from the area to be examined at the time of the examination.