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Conventional and Computed Radiography

Fact checked by Esun Lim

Table of Contents

Conventional-and-Computed-Radiography-illustration-from-nmc

When it comes to radiography, there are several imaging methods available. These include conventional radiography, computed radiography, and digital radiography, amongst others. Each has pros and cons of digital radiography that practitioners should consider when deciding on the right solution.

Conventional radiography has for long been the most prevalent form of imaging and it is in no way obsolete. Computed radiography and digital radiography are slowly overtaking it. These deliver results faster, they offer more storage options, make sharing easier, and allow the enhancing of images.

The problem is that there is a lot of information available online. So, it is often difficult to know what the differences are between them or even where to start researching.

Luckily, we are here to help. With this short guide, we will provide some insight into conventional radiology and computed radiology. We will also look at what their differences are.

picture of a doctor looking at radiography image

What Is Conventional Radiography?

Conventional radiography involves the use of x-rays to visualize the internal structures of a patient. These X-rays are in the form of an x-ray beam or electromagnetic radiation which are made by an x-ray tube and projected into a film or detector.

As the radiation passes through the body, it’s captured behind the patient by this detector, film sensitive to x-rays, or a digital detector. This then, in effect, captures the image.

There is a difference in the amount of radiation that different parts, tissues, and structures of the body absorbs, so the amount of radiation that reaches the detector or film varies. For example, bone absorbs more radiation while soft tissue allows more radiation to pass through.

This difference in radiation then causes contrast in an image. The result is a two-dimensional representation of all the structures, tissues, and organs within the patient.

Common clinical applications of conventional radiology radiography include:

  • Chest x-rays to assess lung pathology.
  • Skeletal x-rays on any part of the body to examine the bone structure of a patient and to diagnose pathologies like fractures, dislocations, or other forms of bone pathology.
  • Abdomen x-rays are used to assess abdominal obstruction, free air, or free fluid inside the patient’s abdominal cavity.
  • Dental x-rays to assess and diagnose common dental pathologies like cavities or abscesses.
Conventional and Computed Radiography xray image

What Is Computed Radiography?

Computed radiography works much like conventional radiography. Instead of film, it uses a flexible phosphor imaging plate to capture digital images. In other words, it is one of the digital alternatives of conventional radiography.

During a computed radiography procedure the imaging plates are similarly exposed to x-rays. The energy of the incoming radiation is then stored in the special phosphor layer as opposed to a film layer is the case with conventional x-rays.

A specialized machine then reads these images from the phosphoric plate by using a very finely focused laser beam. When the laser stimulates the image, the plate emits blue light with an intensity proportional to the amount of radiation received during the exposure.

This means, that as is the case with normal x-rays, certain body structures, parts, or tissues allow certain a certain amount of radiation to pass through. In cases of bone, for example, the blue light will be of a lower intensity because less radiation passes through during the exposure.

A photomultiplier then detects the light and an analog to digital converter converts it is a digital signal. This enables the viewing of the image on a computer screen instead of on a lightbox.

After the image is read from the plate and converted into a digital image, it is erased by a high-intensity light source. The plate can then be used again for another procedure.

What Is the Difference Between Conventional and Computed Radiography?

Despite conventional radiography and computed radiography being remarkably similar in how they work, there are certain distinct differences between the two. These all have an impact on the efficiency, cost, quality, and safety of the system.

Image Acquisition

The first obvious difference between the two is the way in which they capture images. As we said before, both systems use cassettes, but conventional radiography relies on a film plate inside the cassette to capture the image.

In contrast, computed radiology relies on a photostimulable phosphor plate inside the cassette to capture the image. Now, with computed radiography, this method allows numerous benefits.

For one, once the image is captured, it is processed by a processing algorithm like that of a digital camera. This processing can take anything from 1 to 3 minutes, so it is a lot faster than conventional radiography can take up to 8 minutes.

Also, it does not require any chemicals or darkroom to process, and, unlike conventional radiography images, operators can further adjust and enhance the image after it is captured.

Cost

The initial costs for a conventional radiography system, cassettes, forms, chemicals, and other processing tools are relatively low. The running costs, however, are often higher than those for computed radiography systems.

In contrast, while computed radiography systems may be more expensive, the running costs are lower. This is because the phosphoric plates have a longer lifetime and can be reused. With conventional radiography, once the plate is used, this is not possible.

Because of this, it has become one of the preferred methods in many health institutions because of its cost-effectiveness in the long term.

Viewing

To view conventional radiography images, a lightbox has to be used with the option of also using a magnifying glass or bright light. One advantage of this is that they can be relatively easily handled and switched around on the lightbox for comparison. So, in other words, it is easy to put two images next to each other for comparison purposes.

Also, depending on the size of the lightbox, a large number of images can be viewed at one time. Another benefit is that a patient’s anatomy is represented in a size like the actual size.

Computed radiography images are viewed on a computer screen, and with cloud storage options available, they can basically be viewed from anywhere. So, for example, the x-ray facility may be in one location while the diagnosing doctor can be any different location and view the images on their computer.

Now, this also offers certain other benefits. For example, conventional radiology images can be easily digitally manipulated with software. This helps healthcare professionals to interpret the images, and they are also able to enhance the images by using certain processing algorithms.

Besides, they can also adjust the brightness and contrast and, in this way, increase the quality of the images. It is also possible to draw accurate measurements on the images without damaging the original image. Here, although measurements can be drawn on conventional radiography images, these are often permanent and cannot be removed.

Another benefit is the flexibility which manipulating images give healthcare professionals. This often results in fewer retakes of the image because of underexposure or overexposure. This not only results in a lower radiation dose to the patient but also a saving in costs for the facility.

Safety

One of the main concerns that people often have when it comes to x-rays, is exposure to radiation.

Traditional x-rays are considered safe by most healthcare specialists and they are commonly used in the healthcare industry. In simple terms, the chances of a patient developing any type of health issue because of having an x-ray done is extremely remote.

Computed radiography is even safer because, according to medical studies, these systems emit up to 80% less radiation than conventional radiography systems.

Archiving

Typically, x-rays taken by using conventional radiography need to be stored in film archive rooms that are humidity and temperature-controlled. Also, the image has a unique master copy, or, in other words, there is only one image available. If this image is lost, there’s no backup and another x-ray will need to be done.

In contrast, there are a variety of ways to store computed radiography images. Irrespective of which method of storage is chosen, all of them take up significantly less storage space and are less expensive than traditional conventional radiography images. These methods can include servers, disk storage, CD, DVD, and cloud storage.

This also means that computed radiography images can be easily and quickly shared digitally between healthcare professionals. This eliminates the need for couriers to deliver the images in person to the offices of a specialist. This results in faster interpretation of the images by a specialist, and it also saves the patient money.

The Bottom Line

Radiography is vital in the diagnosis and treatment of a range of conditions, some serious, and some not so serious. Nevertheless, to perform these procedures a radiography system is necessary and here, practitioners can choose between different options including conventional radiography and computed radiography.

We hope that this post was helpful to illustrate the differences between these two and make the decision easier.

For more information on radiography systems or what their advantages and disadvantages are, visit our website for more details.

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