Computed tomography (CT) scans use X-rays to generate detailed cross-sectional images of the body. Spiral CT, also known as helical CT, is an advancement in this technology. It captures images with enhanced efficiency and comprehensiveness.
Understanding CT Technology
A conventional CT scanner uses an X-ray source that rotates around a patient on a table. The rotating X-ray source takes measurements from various angles. A computer processes these measurements to reconstruct detailed cross-sectional images, or “slices,” of internal structures. In traditional CT, the patient’s table moves incrementally, pausing for each scan.
This method provided valuable diagnostic information but had limitations. The stop-and-go motion made scans slow, and patient movement during pauses could lead to blurry images. The sequential data collection also challenged creating continuous, three-dimensional views of organs or vascular structures.
The Innovation of Spiral CT
Spiral CT revolutionized medical imaging with continuous scanning. The X-ray tube rotates continuously around the patient while the table moves steadily through the gantry. This coordinated movement causes the X-ray beam to trace a helical, or spiral, path. This continuous data acquisition allows rapid and comprehensive coverage.
This approach offers several advantages over conventional CT. Scan times are reduced, often by a factor of 5 to 10, minimizing motion artifacts from patient breathing or involuntary movements. The continuous data stream enables image reconstruction at any point along the scanned volume, providing flexibility for diagnostic evaluation. The complete volumetric data allows creation of high-quality 3D images, offering a detailed view of anatomical structures. This increased efficiency also optimizes radiation dose, as less time is spent scanning.
When Spiral CT is Used
Spiral CT is used across medical specialties due to its speed and detailed images. It images the chest effectively, diagnosing lung nodules, infections, or pulmonary embolisms. In the abdomen, it assesses organs like the liver, kidneys, pancreas, and gastrointestinal tract for tumors, inflammation, or injuries. Its rapid acquisition is invaluable in emergencies, evaluating trauma patients for internal bleeding or stroke victims for brain bleeds or blockages.
Its speed is critical in time-sensitive scenarios, allowing quick and accurate diagnosis to guide immediate medical intervention. For vascular imaging (CT angiography), continuous data acquisition allows precise visualization of blood vessels, crucial for detecting aneurysms, blockages, or dissections. Detailed 3D reconstructions are also beneficial for surgical planning, enabling surgeons to visualize complex anatomy before an operation.
Preparing for and Undergoing a Spiral CT
Preparation for a spiral CT scan involves specific instructions from the healthcare team. Patients may fast for a few hours before the scan, especially if an intravenous contrast agent is planned to enhance tissue or blood vessel visibility. Patients must also remove all metal objects like jewelry, eyeglasses, or dentures, as these interfere with X-ray beams and create image artifacts. In some cases, a contrast agent may be administered orally or intravenously to highlight structures like the digestive tract or blood vessels.
During the procedure, the patient lies still on a motorized table that slides into the CT scanner’s donut-shaped opening. A technologist operates the scanner from a control room, communicating with the patient through an intercom. Patients may hold their breath briefly during the scan to minimize motion and ensure clear images. While the scanner can be noisy, the procedure is generally painless, with scan times ranging from seconds to minutes depending on the area examined.
References
1. American College of Radiology. (2024). Computed Tomography (CT) Scan. [Online]. Available at: https://www.radiologyinfo.org/en/info/ct [Accessed 28 August 2025].