Non-invasive 'brain palpation' may detect Alzheimer's

London: The brain cannot be palpated without using a highly invasive procedure, but researchers have now developed a noninvasive brain imaging method using magnetic resonance imaging (MRI) that provides the same information as physical palpation.

Ultimately, it could be used in the early diagnosis of brain tumours or Alzheimer's disease, the study noted.

"Alzheimer's disease, epilepsy, multiple sclerosis and hydrocephalus involve changes in the stiffness of the brain tissues. This new technique allows their detection, and could be used to avoid brain biopsies," said one of the study authors Stefan Catheline from French Institute of Health and Medical Research (Inserm). 

Many diseases involve structural changes in tissues, which are reflected in a change in their mechanical properties, such as elasticity. 

Using the sensitivity of their hands, and their detailed knowledge of the body, physicians, through an examination known as palpation, can assess the size and stiffness of a tumour, the presence of inflamed lymph nodes, or the size and position of the foetus in a pregnant woman, to mention a few examples.

This palpation has been supplemented or replaced by modern techniques that give the physician an indication of the elasticity of a biological tissue. 

They are based on the generation and detection of waves that propagate through the body at varying speeds depending on the stiffness of the organs (the stiffer the tissue, the slower the wave propagation, and vice versa). 

However, this method cannot be applied to the brain, which, doubly protected by the cranium and cerebrospinal fluid, is difficult for externally applied waves to access. 

In this study,the researchers, using MRI, have succeeded in detecting natural shear waves in the brain using computational techniques borrowed from seismologists and known as "noise correlation".

They were thus able to build images of the brain's elasticity.

"If this method can be developed for clinical use, it will be a boon for both the patient and the physician, since making the brain vibrate is quite painful at the moment. Of course, this method will be complementary to those that already exist, and the future is in a multimodal medical diagnosis," Catheline noted.

The study was published in the journal PNAS.