Dual-Energy CT

Dual-energy CT is a computed tomography technique that captures two sets of measurements at once, using a low and a high X-ray energy. Because materials in the body absorb low and high-energy X-rays differently, comparing the two sets reveals their composition, not just their shape. The scan is performed on a CT scanner much like a standard one: the patient lies on a table that passes through a ring-shaped opening, and the machine builds detailed cross-sectional images. The extra energy information is processed by the computer, giving doctors a richer picture than a single-energy scan.

During the scan, X-rays at two different energy levels pass through the body and are recorded by detectors as the scanner rotates around the patient. The computer compares how each area absorbed the low-energy and high-energy X-rays and uses this difference to identify what materials are present. For example, it can highlight iodine from a contrast agent, separate calcium from other tissues, or pick out the chemical make-up of a kidney stone. The patient simply lies still while the table moves smoothly through the scanner, and in many studies a contrast agent is given through a small vein.

Dual-energy CT improves the detection and characterisation of tumours, helping to clarify whether a finding is likely to be significant. It is particularly useful for analysing kidney stones, where it can suggest their composition and guide treatment, and for identifying gout deposits in joints. It also helps assess the blood supply to organs and tissues, which is valuable in many conditions. Because it can reduce the amount of contrast and radiation needed, it is helpful for patients who require detailed imaging while keeping exposure as low as possible.

The main benefit of dual-energy CT is precision: by reading two energy levels at once, it characterises tissues and materials more accurately than standard CT, often answering a question that would otherwise need a further test. It can frequently do this with less contrast agent and a lower radiation dose. The examination is painless and similar to a standard CT. The patient lies on a table that passes through the open ring, stays still and may hold their breath briefly. If contrast is used, it is given through a small vein and may cause a brief warm feeling. There is no recovery time, and a specialist reviews the images and reports to the treating doctor.