A Continuous Glucose Monitor (CGM) is a small medical device worn on the skin that automatically tracks glucose levels throughout the day and night. Mammography is an X-ray imaging procedure designed to screen for breast cancer by using compression to flatten the breast tissue and obtain a clear image. The presence of a CGM introduces a conflict with diagnostic breast imaging procedures, concerning both the effect of the imaging technology on the sensor and the sensor’s physical presence on the final image quality.
The Direct Answer: CGM and Mammogram Compatibility
The immediate answer is that it is usually recommended to remove the CGM sensor before a mammogram. This guidance is standard for most radiology departments and device manufacturers due to concerns about image quality and device integrity. However, the necessity for removal depends on the sensor’s placement. If the sensor is located outside the imaging field (e.g., on the back of the arm or abdomen), removal may not be mandatory. Some manufacturers, such as Abbott for the FreeStyle Libre 2 and 3 systems, now allow their sensors to be worn during certain diagnostic X-ray procedures, but patients must confirm the specific policy with their imaging center and the device manufacturer.
Understanding the Imaging Conflict
The primary concern is the potential for the sensor to create an imaging artifact that could obscure a small abnormality. Continuous glucose monitors contain electronic components, wires, and plastic housing that interact with the X-ray beam differently than human tissue. These materials can generate bright spots or shadows on the resulting mammogram image. The diagnostic value of a mammogram relies on detecting minute signs of cancer, such as clustered microcalcifications or subtle masses. Artifacts from a CGM can mimic or hide these structures, potentially leading to a missed diagnosis and often necessitating a repeat scan.
Physical Risk to the Sensor and Skin
Leaving a CGM sensor in the direct path of the compression paddles introduces a physical risk to both the device and the patient’s skin. Mammography requires significant force to flatten the breast tissue for optimal imaging, with compression forces ranging between 111 and 200 Newtons (or up to 45 pounds of force). This extreme pressure is designed to spread the tissue evenly, but it is far beyond what a skin-worn device is engineered to withstand. If a sensor is compressed, the mechanical stress could lead to internal damage, such as a broken filament or electronic malfunction, rendering the device inaccurate or inoperable. For the patient, this compression could cause pain, bruising, or trauma to the skin where the sensor’s adhesive and cannula are inserted.
Managing Glucose Monitoring During Removal
For patients who must remove their CGM, proactive planning minimizes disruption to their diabetes management. A recommended strategy is to schedule the mammogram near the end of the sensor’s wear cycle to avoid wasting a new device. Most manufacturers have programs to replace sensors removed early for a medically necessary procedure. During the gap before applying a new sensor, patients should temporarily revert to traditional finger-stick blood glucose testing to ensure continuous, accurate monitoring. Proper skin care is also important after removal, including using an adhesive remover and rotating the application site.