Elastography
Elastography helps to noninvasively visualize the difference between the biomechanical properties of normal and diseased tissues. Normal tissue is softer than diseased tissue. In that sense, elastography is similar to palpation. Hard tissue is palpable by external touch. To be palpable, the object must be harder or softer than the tissue surrounding it. Fingers can displace tissue downward during palpation, and the pressure receptors on the skin of the fingers can sense the local stress values. Stress is higher on the fingers overlying a superficial hard lesion and lower on the fingers overlying softer tissues. This principle is used in elastography where the ultrasound transducer can be used to “feel” how hard or soft a particular tissue is and hence differentiates between normal and diseased tissue.
We perform ultrasound elastography as a technique to replace liver biopsy in patients with suspected liver disease.
US elastography of the liver done instead of a biopsy. The liver was not stiff with a very low value of 1.16m/s and hence the patient did not have cirrhosis.
We also perform ultrasound elastography for research in the thyroid. The example given illustrates this technique.
Ultrasound of the neck in a 34 year old patient shows a small nodule in the thyroid gland (arrow). The carotid artery (c) is seen adjacent to the nodule.
Ultrasound elastography image shows the nodule to be predominantly soft (blue color – arrows) indicating a lesion that has less likelihood of being malignant.
A blend of ultrasound and ultrasound elastography image makes it easy to see the nodule and the color map in this nodule (arrows).