A Continuous Glucose Monitor (CGM) uses a small sensor inserted under the skin to track glucose levels throughout the day. A Computed Tomography (CT) scan is an imaging procedure that uses X-rays and computer processing to create cross-sectional images of the body. While the CGM is an important tool for diabetes management, any medical procedure involving powerful imaging technology requires careful consideration. The question of whether a CGM can remain in place during a CT scan depends on balancing diagnostic needs with the device’s integrity and the resulting image quality.
Why Removal is the Standard Protocol
The general recommendation from most manufacturers and medical institutions is to remove the CGM sensor and transmitter prior to undergoing a CT scan. This protocol prioritizes the accuracy of the imaging procedure and the functional safety of the monitoring device. Although the X-ray radiation used in a CT scan poses an extremely low physical risk to the patient, the primary concern is the potential for device malfunction. Exposure to ionizing radiation can potentially affect the small electronic components and data storage within the CGM transmitter.
While the probability of permanent device damage is considered low, this guidance ensures that the patient does not rely on potentially inaccurate readings from a compromised sensor following the scan. However, some newer CGM systems have undergone testing and have had their contraindications for CT scanning removed by the manufacturer. Patients using these specific systems may be cleared to leave the sensor on, but they must check the device’s current labeling and consult with their physician.
Understanding CT Scan Artifacts
The requirement to remove the device is also driven by the physics of how CT scans work and the creation of image imperfections known as artifacts. CT scanning relies on the differential absorption of X-ray beams as they pass through various tissues in the body. The CGM sensor contains dense materials, including a small metallic filament and internal wiring, which strongly absorb or completely block the X-rays.
When the X-ray beam encounters this dense material, the CT detector is unable to accurately measure the radiation that passed through that area. This blockage creates bright streaks or star-like distortions radiating outward from the device’s location on the resulting image. These artifacts obscure the surrounding anatomical structures, which can significantly compromise the diagnostic quality of the scan. The size of this distortion can be substantial, potentially measuring several centimeters across. For example, a sensor placed on the abdomen during an abdominal CT scan may produce an artifact large enough to hide a small tumor or a section of the bowel.
Practical Preparation Steps Before Your Scan
Patients should inform the ordering physician and the CT technologist that they wear a CGM as soon as the imaging appointment is scheduled. This communication allows the care team to make an informed decision regarding the imaging area, the need for removal, and the timing of the procedure. If removal is required, the best practice is to coordinate the CT appointment with the end of the sensor’s current wear cycle. This minimizes the loss of sensor life and reduces the financial burden of replacing a partially used sensor.
The patient must remove the sensor and transmitter from the skin before entering the scanning room and store it safely outside the procedure area. Since there will be a gap in continuous glucose monitoring data, the patient must be prepared to use a standard finger-stick blood glucose meter for temporary monitoring. After the CT scan is complete, a new sensor can be inserted, but the patient must account for the typical warm-up period required before the new sensor begins providing accurate readings.