PET scan tracer highlights areas of pain inside soft tissue
30 October 2013
Researchers at Uppsala University have developed a method to
image the areas of damage and pain in soft tissue following injury
such as tennis elbow.
It could provide a means to identify true cases of neck whiplash
injury in car crashes. This is an area of interest for insurance
companies due to the high number of claims for compensation,
especially in the UK where it has pushed up the cost of car
The method involves injecting a radioactive tracer that binds to
a signal receptor called NK1 that has been associated with tissue
damage. The distribution of radioactive tracer can then be captured
as an image using a PET scanner.
Following tissue damage there is an up-regulation of the
neuropeptide chemical P and its receptor NK1. This occurs not only
in the dorsal horn of the spinal cord, but also in the peripheral
painful tissue. This up-regulation is part of an interaction between
peripheral nerves, immune cells, and the tissue itself that seems to
help guide the body’s own repair process. In chronic tennis elbow,
this up-regulation of the substance P-NK1 system lingers on.
This is the first time an up-regulation of NK1 receptors has been
visualized by diagnostic imaging in painful tissue in humans. The
study clearly reveals an image of elevated levels of NK1 in the
painful area compared with the healthy arm.
PET image of NK1 receptor radioligand in an
Pain from soft tissues (muscles, tendons and ligaments) is still
lacking effective methods for localization and diagnosis of
underlying pathophysiological mechanisms. This means that diagnosis
still depends on clinical examination, which provides no guidance
regarding what mechanisms might underlie the pain. Consequently,
treatment proceeds purely on an empirical basis. An improved
diagnostic method that allows not only diagnosis of localisation of
the painful tissue processes, but also can provide guidance
regarding what pathophysiological mechanisms are involved, would
therefore be highly valuable. The new method is promising, but the
costs are still high.
"In the future, we hope to be able to develop less expensive
markers that enable us to use the method in everyday clinical
practice. We also aim to create markers for other physiological
processes that we know are active in chronic soft tissue pain," says
researcher Magnus Peterson.
Peterson M, Svärdsudd K, Appel L, Engler H, Aarnio M, et al.
PET-Scan Shows Peripherally Increased Neurokinin 1 Receptor
Availability in Chronic Tennis Elbow: Visualizing Neurogenic
Inflammation? PLoS ONE 2013 8(10): e75859.