Introduction
Regular abdominal dual-energy computed tomography (CT) can improve the accuracy of cancer imaging diagnoses and detect problems connected to the pancreas, liver, and urinary system. This technique is very useful in detecting certain diseases, such as gallstones without calcium, kidney stone comprehension, kidney cyst classification, and improved bowel problem detection.
What Is the Principle of Dual Energy Computed Tomography?
X-rays are used in routine CT scans to view the inside of the body. They quantify the radiation absorbed by various tissues and express the results as CT values in Hounsfield units (HU), adjusted for water content. These CT values, however, can vary since different materials absorb X-rays in different ways, making it challenging to distinguish between them precisely.
Conversely, dual-energy CT examines the response of materials to X-rays at several energy levels. To achieve this, the photoelectric effect and the Compton effect are considered. The photoelectric effect is significant for materials with high atomic numbers (such as calcium and iodine). Still, the Compton effect is more pertinent for materials with low atomic numbers (such as soft tissue).
Dual-energy CT uses the differences in how various materials absorb X-rays at high and low energies. This makes it more accurate in differentiating between materials, which is a problem with routine CT scans.
What Are the Principles Used in Different Types of Dual Energy Computed Tomography?
The principles of dual-energy CT systems are:
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Dual-Energy, Dual-Source CT:
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The two tubes or sources use different energy levels (high and low voltage settings).
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A unique set of detectors is attached to each tube and is angled at a right angle to the tubes.
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Fast Voltage Shifts:
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Fast switching between two voltage settings (often between 80 and 140 kVp) is possible with a single-source CT.
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Collecting the data makes use of a single-layer detector.
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- Using Detectors for Spectral Imaging:
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A single-source CT with a set voltage is used in this technique.
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Two layers comprise the detector: A thick outer layer for high-energy photons and a thin inner layer for low-energy ones.
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How Does Dual-Energy CT Improve Imaging Precision and Visualization Compared to Conventional CT Scans?
1. Common Dual-Energy CT Scanning:
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Basic Images: The scan may produce generic images depending on the materials.
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Unique Pictures:
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Virtual Unenhanced Images: These simulate images without using a contrast agent. They could lessen radiation exposure and take the role of a pre-contrast scan.
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Iodine-Enhanced Images: These images use contrast to emphasize places that contain iodine. It can be displayed as a color map for improved viewing, and the iodine content can be calculated.
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Virtual Monoenergetic Images: They lessen artifacts and increase contrast. Elevated-energy images minimize artifacts, while low-energy images emphasize components with large atomic numbers (such as calcium and iodine).
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2. The Spectrum HU Curve
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Explanation of the Curve: This curve, which resembles a graph, illustrates the reactions of various materials at different energies.
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Material Conduct: Bones and high-atomic-number materials (calcium and iodine) exhibit greater attenuation at lower energies. Water's attenuation remains constant while that of fat reduces. The soft tissues (muscles, organs) are not affected much by energy levels.
Stated more simply, dual-energy CT scans can produce various image types to aid in better visualization for medical professionals, such as highlighting locations that require contrast material or minimizing side effects. Like a map, the spectral HU curve illustrates how body materials react to various energies.
What Are the Clinical Applications of Dual Energy Computed Tomography in Abdomen?
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Gallbladder: Bile, which aids in the digestion of fats, is kept in reserve in the gallbladder, a tiny organ. The gallbladder may occasionally contain cholesterol-containing tiny, soft, non-calcified stones. While these stones might not appear on standard CT scans, they can be seen with a specialized method that uses several X-ray energies. These stones are simpler to spot since they appear brighter in some photos and darker than bile in others.
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Bowel: An advanced imaging method that uses several X-ray energies can assist in pinpointing the portions of the gut that are impacted when there is a problem with the blood supply to those parts. This method also reveals whether the colon wall is inflamed or bleeding. By giving more precise information than traditional imaging, it aids medical professionals in confirming diseases such as bowel ischemia (a dangerous illness that can hurt and interfere with the normal function of the intestines).
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Oncology: Low-energy X-rays can provide specialized images that enhance the visibility of tumors and their relationship to surrounding tissues in cancer detection. This facilitates identifying tumors, comprehending their features, and detecting metastases (spread) to other bodily regions.
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Hemorrhage: In cases of hemorrhagic lesions or abrupt bleeding, special pictures can assist in confirming whether blood is present in the abdomen or pelvis. Diagnosing disorders involving internal bleeding is aided by these images, which display blood as brighter spots.
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Adrenal: Certain forms of growth can be identified by examining the adrenal glands by using a technique that considers the amount of fat in the tissue. This method increases the diagnostic precision for fat-containing, non-cancerous lumps called adrenal adenomas.
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Renal: Using various X-ray energies during the kidney evaluation can yield more detailed information about some lesions, such as hyperdense cysts. This method is particularly useful in individuals with diseases such as polycystic kidney disease (a hereditary condition where kidneys are the primary site of cyst development, leading to gradual enlargement and loss of renal function) when it is important to differentiate between benign lesions and those that could be malignant.
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Bone: An advanced CT scan can produce images showing areas of bone marrow edema (swelling), which is helpful for early bone fracture detection. This aids in the early detection of fractures by helping to identify bone injuries that may not be seen on routine scans.
What Are the Limitations of Dual-Energy Computed Tomography?
Iodine mixed with fatty acids from poppy seed oil is known as Lipiodol. It is applied through a process known as chemoembolization to treat liver cancer. Because of its high iodine level, lipiodol appears extremely bright in liver imaging. It appears less bright on another kind of image, known as virtual unenhanced images.
These photos are not particularly useful for identifying kidney stones in cases where the stone size is less than 3 millimeters. This results from the small stones' poor visibility in these images.
Conclusion
For abdominal CT scans, dual-energy CT provides radiologists with more helpful information than standard single-energy CT scans. In their daily work, radiologists must be aware of the various methods in which they might employ dual-energy CT to assess a large number of processed pictures quickly. To prevent misinterpreting the outcomes, they must understand the limitations of these processed images.
