A Computed Tomography (CT) scan uses a series of X-ray images taken from different angles around the body. A computer processes these images to create detailed cross-sectional pictures, or slices, of bones, blood vessels, and soft tissues, providing more detail than a standard X-ray. Patients often ask if the scanner is open or closed, especially due to concerns about feeling confined compared to devices like Magnetic Resonance Imaging (MRI) machines.
The Standard CT Gantry Structure
The physical structure of a CT scanner is defined by its gantry, the large, circular housing that contains the X-ray components. This gantry is shaped like a hollow ring, and the patient table slides through the central opening, known as the bore. The design requires the X-ray source and the detectors to be opposite each other for image acquisition.
Inside this circular gantry, the X-ray tube and detectors are mounted on a rotating frame. To capture the necessary cross-sectional data, this assembly must spin 360 degrees around the patient as they pass through the bore. Standard diagnostic CT scanners typically have a bore diameter, or aperture, ranging from 65 to 70 centimeters.
The patient table moves the patient into the center of the gantry for imaging, but the machine is open on both the front and back. Unlike some magnetic resonance machines, a CT scan often involves only the section of the body being examined passing through the ring, not full enclosure within a long, narrow tunnel.
Wide-Bore CT Technology
The question of whether a CT scanner is “open” or “closed” is complicated because the technology requires a continuous ring structure for X-ray beam rotation. True open designs, such as those found in some Open MRI machines, are not feasible for CT. To address patient comfort and physical accommodation, manufacturers have developed wide-bore CT scanners.
These wide-bore systems feature a significantly larger opening than traditional units, with apertures commonly measuring between 80 and 90 centimeters, compared to the standard 70 centimeters. This increased diameter is beneficial for patients experiencing claustrophobia, as the extra space reduces the feeling of confinement.
The larger bore also provides practical advantages for accommodating bariatric patients or those requiring specialized positioning equipment. For instance, the wider gantry aperture can allow for complex immobilization devices or specific arm positions that would be impossible in a narrower machine. While still a ring, the increased size of the wide-bore CT provides a more comfortable experience and expands the types of patients who can be safely and effectively scanned.
Patient Comfort and Preparation
Despite the typically faster and more open nature of a CT scanner compared to an MRI, some patients still experience anxiety when anticipating the procedure. A helpful factor in managing this is the speed of modern CT technology, with many scans completed in just a few minutes or even seconds. The technologist can often see and hear the patient throughout the process, allowing for continuous communication.
Patients who feel anxious can proactively discuss their concerns with their physician or the imaging center staff beforehand. Simple, non-technical strategies can be employed, such as closing the eyes before entering the gantry to minimize the visual trigger of the confined space. Focusing on slow, deep breathing exercises can also help maintain a sense of calm during the brief imaging sequence.
In situations of high anxiety or severe claustrophobia, a mild sedative, such as a low dose of an anti-anxiety medication like lorazepam or diazepam, may be prescribed for use before the scan. Patients should confirm this option with their referring physician and the imaging center well in advance. Understanding that the scan time is short, and that the machine is open on both ends, can also help patients feel more prepared.