A mammogram is a specialized X-ray used to create images of the breast tissue, primarily for screening and early detection of cancer. The procedure requires the breast to be firmly compressed between two plates. While this compression causes temporary discomfort, it is a non-negotiable step necessary for acquiring a diagnostic quality image.
The Medical Necessity of Breast Compression
The primary purpose of flattening the breast is to separate and spread out the internal tissue structures. Breasts contain a mix of fatty and glandular tissue, and without compression, these overlapping layers can hide small abnormalities, such as tiny calcifications or masses.
Compression also ensures the breast remains completely still throughout the brief X-ray exposure, which prevents motion artifacts or blurring on the final image. Even slight movement can compromise image clarity, necessitating a repeat scan.
Achieving a uniform thickness across the entire image field is another technical requirement, as it allows the X-ray beam to penetrate the tissue evenly. If the tissue thickness is inconsistent, some areas may be under-exposed while others are over-exposed, leading to a non-diagnostic image.
Quantifying the Flattening
The degree of flattening a breast undergoes is quantified by the amount of force applied and the resulting tissue thickness. The force is delivered by the machine’s compression paddle and is measured in Newtons (N) or pounds of force. The maximum force applied during a mammogram is regulated not to exceed 200 N, which is roughly equivalent to 45 pounds of force.
In practice, the applied force generally falls within a range of 100 to 200 N. This force reduces the original breast tissue to a final compressed thickness that typically falls between 10 mm and 88 mm.
Technologists aim for a compression level that achieves optimal tissue separation and immobility, determined by tissue density and patient tolerance, rather than a fixed number. A smaller, denser breast may require a similar force to a larger, fattier breast to achieve the necessary diagnostic flattening.
Compression’s Role in Image Quality and Safety
The physical act of flattening the breast translates into two technical benefits: increased image quality and reduced patient exposure to radiation. When the breast is compressed, the X-rays travel through a thinner layer of tissue, which significantly lowers the required radiation dose. This is a direct safety measure, allowing the equipment to use a lower-energy X-ray beam while still capturing a high-quality image.
Furthermore, compression enhances image clarity by minimizing scatter radiation. Scatter radiation occurs when X-ray photons deflect off dense tissue and travel in random directions, creating a hazy or blurred effect. By reducing the volume of tissue the beam must penetrate, compression limits this scatter, thereby improving the contrast between healthy tissue and potential lesions.
A sharper contrast allows the radiologist to detect subtle indications of disease, such as microcalcifications. Inadequate compression is a known cause of poor image quality, which can lead to a patient being called back for additional imaging.
Patient Experience and Minimizing Discomfort
While compression is necessary, there are practical ways to minimize associated discomfort. Patients can help reduce breast tenderness by scheduling their mammogram for a time when their breasts are least hormonally sensitive, such as the week following their menstrual period.
Before the exam, patients can consider taking an over-the-counter pain reliever, such as ibuprofen or acetaminophen, after consulting with their physician. Communication with the technologist is also a factor, as they can adjust the compression level based on the patient’s tolerance while still aiming for a diagnostic image.
The pressure is only applied for a very short duration, typically lasting only 10 to 15 seconds per view. Studies show that patient involvement in the process can lead to adequate pressure application with less reported pain.