Microscope detects cancer cells spreading through the bloodstream
1 October 2013
A team at Stanford University is developing a pen microscope that
could noninvasively detect cancer seed cells circulating in the
bloodstream, allowing for earlier interventions than current
Currently, a blood sample is analysed using special antibodies to
detect the presence of these seed cells, called circulating tumour
cells (CTCs). This works well if CTCs are present in large numbers,
but may fail to detect smaller numbers in the early phase of tumour
In the new technique, a patient is injected with a dye that
causes the CTCs to fluoresce. A pen-sized microscope focusses a
low-power laser light on a blood vessel just a few hair-widths below
the patient's skin.
As the dyed cancer cells pass through the laser, the light
excites them and causes them to stand out from normal cells. The
microscope registers each of these cells and a computer logs each
observation. The improved sensitivity of the technology and the
ability to noninvasively scan blood for long periods will help
create a fuller picture of the number of CTCs in a person's body.
To date, the research has focused on developing the method in
mice, taking advantage of the thin transparent tissue of the ear to
image fluorescent cells traversing the small blood vessels below the
"There has been a huge push to increase sensitivity," said Bonnie
King, an instructor at Stanford School of Medicine. "We suspect that
CTCs often circulate in numbers below our current threshold of
A pen-sized microscope focuses a low-power
laser light on a
blood vessel just below the patient's skin to
cancer cells. (Photo credit: Linda A. Cicero / Stanford
A major advantage with the microscopic technique, King said, is
the ability to screen much larger volumes of blood, rather than just
a small vial collected from a patient. This will be done using a
method called in vivo flow cytometry, a laser-based
technology for counting cells in a live subject.
"At present we will not screen all of a person's blood [with the
microscope], but we are aiming to increase the amount of blood
screened compared to a 7-milliliter blood draw," said Christopher
Contag, Professor of Pediatrics at the School of Medicine.
The work is a collaborative effort of Olav Solgaard, a professor
of electrical engineering; Geoffrey Gurtner, a professor of surgery;
and Michael Clarke, a professor of oncology.
Soon the researchers will move the microscope to a clinical
setting to conduct a proof-of-principle test of the technique in
humans. Gurtner is currently conducting a clinical trial to evaluate
the FDA-approved green dye for defining skin vasculature during
post-mastectomy breast reconstruction surgeries. The researchers are
piggybacking on this trial to test the miniature microscope's
ability to detect blood vessels and circulating cells.