Introduction
Medical science and diagnostic imaging are advancing frontiers that help acquaint doctors and researchers with novel conditions and their management. Various imaging techniques have seen variations in their principle and usage, thus enhancing their applications in the clinical field. However, to ensure their appropriate use, radiologists should be well aware of the procedure's working principle, risks, and limitations.
Computed tomography is a diagnostic imaging technique that utilizes X-rays and a computer system to generate images of the body's organs and tissues. The invention of the CT scan was a revolution in the medical field, considering its ability to view body parts in multiple planes with the possibility of obtaining a series of images. This helped to view the minute details in a three-dimensional format. Being non-invasive, cost-effective, and relatively straightforward, the CT scan is the most sought-after diagnostic imaging technique. Considering the ease of handling the scanning technique, various modifications and innovations were experimented with in CT scans. One such variation is the dual-energy CT scan (DECT).
What Is Dual-Energy Computed Tomography (DECT)?
A conventional computed tomography scan uses a single X-ray photon (standard X-rays) to create the images, whereas DECT uses two distinct X-rays to create the images. It uses one normal X-ray and a second with less energy to capture the images. As a result, it provides more detailed morphologic images than a conventional CT scan. It also aids in functional imaging of the body parts, thereby assessing and evaluating the disease's etiology and progression.
What Are the Clinical Applications of DECT?
To ensure prompt and accurate treatment, it is essential to diagnose the condition early. Understanding the cause of the disease, its progression, and the biochemical reactions behind the occurrence of the disease helps in detecting the condition. Furthermore, precise data acquisition and analysis can help researchers work their way to novel treatment procedures and preventive measures. Hence advanced imaging techniques are a boon to clear-cut diagnosis. DECT is far superior to conventional CT in obtaining the images, thereby assessing the structural and functional abnormalities.
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It has found wide applications in diagnosing various liver, kidney, heart, lungs, breast, pancreas, and brain conditions.
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A contrast DECT can be used to evaluate the blood vessels. In addition, it can be used to assess the functioning of organs.
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DECT can efficiently increase or decrease the effect of the contrast agents used, thus producing high-quality images. Hence more widely used in a procedure like CT angiography, where contrast agents are used to analyze the blood vessels.
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Contrast images can be obtained using a single examination, unlike conventional CT, where two separate analyses are required.
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It has proved a valuable tool for patients with metal implants or joint replacements.
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It is a vital tool in neuroimaging in traumatic or hemorrhagic conditions.
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In breast implant patients, DECT helps identify silicone leaks.
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To detect bone marrow edema, quantify and evaluate the urate crystals in gout.
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It is helpful to identify and diagnose pulmonary nodules, pulmonary perfusion, and thromboembolism in the lungs.
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It can help determine the composition of renal stones to aid in appropriate treatment.
What Are the Instructions Before the Procedure?
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Instructions for a DECT scan are similar to that of a conventional CT scan. It is carried out as an outpatient procedure.
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Abdominal scanning may require fasting for four to six hours before the procedure.
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Patients need to wear loose, comfortable clothes.
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Any metallic accessories or jewelry should be removed before the procedure. In addition, patients should ensure their clothes are devoid of metallic buttons, buckles, or belts.
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Before entering the procedure room, they should remove eyeglasses, removable dentures, hairpins, hearing aids, or other electronic devices like mobile phones.
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Ladies who are pregnant or might be pregnant should inform the doctor before the procedure.
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Patients with a history of allergy to drugs, latex, or other medical substances should inform the doctor. The previous history of allergy to contrast material should also be notified.
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It is crucial to assess renal functioning if a contrast DECT is advised.
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Patients with medical histories such as cardiac diseases, renal conditions, or other medical issues should inform the doctor before the procedure.
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They should also carry their recent reports and prescription medicine to the diagnostic center.
What Is the Principle Behind DECT?
A conventional CT scan works similarly to an X-ray. The X-ray is absorbed in different amounts by various body parts. The X-ray detectors in the scanning unit quantify the radiation absorbed and process it into images in a computer. In DECT, two different energy photons (X-ray) are projected. When the body is exposed to the first beam, the various body parts may show a similar attenuation; however, the attenuation value differs when exposed to the second beam of lower energy. Substrates or tissues closer to the energy values may vary in attenuation value from the first energy beam. This difference can be used to diagnose the condition, or the chemical composition of the tissue analyzed.
What Are the Types of DECT?
Based on the energy spectrum used, two different models have been proposed:
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Low-Energy Spectrum: 80-100 kVp (kilovoltage peak).
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High-Energy Spectrum: 140-150 kVp.
What Are the Instructions After the Procedure?
DECT is a simple procedure as conventional CT. No special instructions are required. Patients can resume their regular diet and activities after the procedure. However, patients who have received the contrast material will be advised to drink plenty of fluids to help expel the contrast material from the body.
What Are the Risks Associated with DECT?
Some DECT scanners use slightly higher radiation as compared to others. Though with the recent computerized dose-saving in-built techniques in the most scanning unit, the risk of radiation exposure has considerably reduced.
What Are the Benefits of DECT?
DECT has all the benefits of a conventional CT. In addition, it also has some added advantages, such as:
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Increasingly beneficial to assess blood vessels considering the high-resolution and high-precision images.
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Decreased number of scans.
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An added advantage of evaluating the chemical constitution of the disease.
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Better images with implant transplants with high-quality images of the metal used.
Conclusion
Dual-energy CT scan is an emerging horizon in medical imaging. Properly understanding its principle and usage can widen its clinical applications and may prove to be a valuable tool in therapeutic research.
