The term “liver scan” is a general phrase used to describe several different medical imaging procedures aimed at examining the liver’s size, shape, and overall health. These tests are performed for various reasons, such as investigating symptoms, monitoring known conditions, or checking for abnormalities found on other exams. Because the liver performs many complex functions, no single imaging test can provide all the necessary information. Different technologies are used to focus on either the organ’s physical structure or its functional processes, requiring a doctor to select the right procedure for a specific clinical question.
Standard Methods for Visualizing Liver Anatomy
The most common initial method for examining the liver is an Ultrasound, a non-invasive procedure using high-frequency sound waves. A probe placed on the patient’s abdomen sends these waves into the body, and the returning echoes create a real-time image of the internal organs. This technique is frequently used for a quick assessment of the liver’s size and texture, and to look for fluid collection, masses, or blockages in the bile ducts. Ultrasound can also utilize Doppler technology to evaluate blood flow, which is important for assessing certain liver diseases.
Another standard imaging method is the Computed Tomography (CT) scan, which uses X-rays and computer processing to produce cross-sectional images of the liver. The X-ray source rotates around the patient, taking pictures from many angles to build a detailed three-dimensional view of the organ. CT scans are useful for quickly identifying large lesions, tumors, or signs of internal trauma. Often, an intravenous contrast agent is injected to enhance the visibility of blood vessels and specific tissues, helping to detect abnormalities.
Detailed Imaging for Structure and Function
For more detailed visualization of soft tissues, Magnetic Resonance Imaging (MRI) is often performed as a follow-up to standard scans. This technique uses strong magnetic fields and radio waves to generate highly detailed images, offering better soft tissue contrast than a CT scan without using ionizing radiation. MRI is excellent for characterizing masses in the liver, helping to determine if a lesion is benign or malignant. Specialized contrast agents can track blood flow and assess liver cell function, providing both structural and physiological information.
A different approach is the Positron Emission Tomography (PET) scan, which focuses on the metabolic activity of the liver rather than just its structure. A small amount of a radioactive tracer, typically fluorodeoxyglucose (FDG), is injected into the bloodstream. Since metabolically active cells, such as those in many tumors, absorb more glucose, they take up more tracer and “light up” on the PET image. This scan is primarily used in oncology to detect cancer, determine if it has spread, and monitor treatment response. PET scans are frequently combined with CT scans (PET-CT) to overlay functional information onto a precise anatomical map.
Non-Invasive Assessment of Liver Stiffness
A specialized procedure known as Transient Elastography, often marketed under the brand name FibroScan, is used to measure the stiffness of the liver tissue. This method is distinct from standard structural imaging because its specific purpose is to quantify the degree of scarring, or fibrosis, that has occurred. The device uses a specialized ultrasound probe to send a low-frequency mechanical vibration, or shear wave, into the liver.
Measuring Stiffness
The speed at which this shear wave travels through the tissue is measured; the faster the wave moves, the stiffer the liver is. Since scar tissue is firmer than healthy liver tissue, the measured stiffness, expressed in kilopascals (kPa), directly relates to the severity of fibrosis or cirrhosis. This non-invasive test offers a convenient way to stage chronic liver disease and monitor its progression, reducing the need for an invasive liver biopsy.