Ultrasound in diagnostic medicine has been used for a very long time. Almost every one has faced it: during the examination of the abdominal cavity organs, heart, blood vessels, skin, breast, gynaecological examination, and in the baby's development monitoring during pregnancy. Elastography or sonoelastography is the most recent method of ultrasound, based on on-line measurements of tissue elasticity. Elasticity images are analysed using an autocorrelation method, and they are coded in colours. The method was originally created for early diagnosis of breast cancer, but now it is used for examination of other organs.
Based on the various characteristics of tissue elasticity, they allow distinguishing malignant tumour tissues from other healthy tissues. Elastography is not a separate type of examination; it is a new mode of ultrasound examinations which supplements the "normal" B ultrasound mode.
Two main types of elastography are applied in clinical practice:
•deformation or Strain elastography;
•Shear Wave elastography.
In deformation elastography, images are made by using the data obtained due to tissue deformation by external palpation or internal tissue movements.
Shear Wave elastography is based on internal changes in tissue elasticity, caused by the impulse of focused ultrasound waves - the so-called acoustic power radiation generated by the ultrasound device which allows carrying out a much more objective and more quantitative measurements of internal tissue elasticity. Shear Wave elastography is much more objective, which is also related to the fact that it uses ultrasound impulses with certain parameters, therefore this examination does not subjectively depend on the ultrasound specialist – strength and frequency of his palpatory movements. Shear Wave elastography required specialised ultra-fast ultrasound devices.
New Philips technology
Ultrasound devices Philips Epique 5 and Philips Epique 7 of premium segment applied by HC4 physicians contain ElastPQ Shear Wave transverse wave elastography technology. It is based on the unique patterns of pulsatile activity which can ensure absolute tissue density measurements. It is currently the most effective of the commercially available elastography technologies.
Combination of the elastography method and conventional ultrasound improves the diagnostic accuracy and allows to:
•assess malignity risk for growths in various organs;
•assess tumour spread, possible tumour capsule invasion;
•differentiate between serous and haemorrhagic cystic growth content.
When the structure of the growth is known more precisely, it helps to avoid puncture biopsy in some cases.
Elastography is applied for the examination of abdominal organs – liver, spleen and kidney, examination of the thyroid gland, soft tissues of the neck, breast, and for diagnostics of muscle and tendon injuries. It is also applied to examine growths in prostate, urinary bladder, rectum, uterus and ovaries, when using special endocavital (gynaecological and rectal) probes. Elastography allows estimating possible muscle and tendon injuries.
The examination is carried out just like a standard ultrasound examination. The examined organs are scanned by a physician; when nodes or other suspicious structures are found, the physician includes elastography mode of the device, makes focused measurements of tumour tissue elasticity, and compares their elasticity to the surrounding tissues. For the patient this examination is the same as a regular – he experiences no pain or discomfort. This examination involves no significant restrictions – it can be performed in all age groups and in pregnant women. Previous preparation for the examination is the same as for any other ultrasound examination. If ultrasound and elastography of the abdominal cavity is planned, the patient should not eat for 6 hours before the examination.
When going to the examination, it is recommended to bring the findings of all previous examinations and all other radiological examinations, so that a physician could compare the changes in the examined structures over time. The duration of the examination is the same as for other ultrasound examination (perhaps a little longer), depending on the type of sonoelastography. Physician's referral is required to undergo sonoelastography examination paid by the insurance company.
The most common elastography examinations:
Liver elastography allows assessing the status of the liver (degree of liver fibrosis) in patients suffering from viral hepatitis and liver cirrhosis of different etiology. The studies show that this method is a good alternative for the liver puncture biopsy. The patient and physician can identify liver density, which is increased in patients with cirrhosis (connective tissue is formed in the liver; the liver becomes non-elastic).
Thyroid examination helps to differentiate cystic growths and benign nodes of the thyroid gland from malignant thyroid tumours (papillary, follicular, parafollicular cell cancer). Density of nodes can be established, as it is important for to determine malignancy risk of nodes – the physician can get more information by applying elastography. Node density is also one of the points in TIRADS classification of the standard assessment system of thyroid node malignancy risk.
Breast examination improves accuracy of the diagnostics, helps to differentiate benign breast growths (cysts, lipomas, fibroadenomas) from abnormal processes (mastitis) and malignant tumours (infiltrating ductal carcinoma, papillary carcer, etc.).