In Vivo Reflectance Confocal Microscopy (RCM)
What is Confocal Imaging?
Handheld in vivo reflectance confocal microscopy (RCM) is a non-invasive imaging procedure that allows real-time viewing of cells, resulting in virtual biopsies.
RCM uses a laser diode as the source of the light. An operator uses a handheld wand while light passes through optics and illuminates a small area of tissue. Light reflected back through the lens, at a given focal point, is recorded digitally. The wavelength of the light does not cause injury and is only slightly warm to the patient.
The operator can control the depth of the images and can record video or stacks of images as they view a screen showing the patient’s cell structure in real-time. Since RCM is noninvasive, it can allow the same area to be reviewed over time without impacting the tissue.
Handheld RCM allows viewing of the epidermis down to the papillary dermis. RCM allows physicians to cover a larger area than other techniques and without any pain to the patient. RCM can also record images in difficult to reach or sensitive locations. The downside of the process is that RCM requires a highly trained and skilled pathologist as the operator must view a screen in real-time to determine where the handheld wand should be placed.
The confocal microscope was invented in the 1950’s but it took until the 1990’s for the technology to mature to a point were portability and digital recording of images was possible.
Handheld RCM works well as an adjunct to traditional scouting biopsies in extramammary Paget's disease (EMPD) treatment and diagnostics. However, since RCM has a small field of view and limited depth it has does have limitations in some applications.
In vivo reflectance confocal microscopy was approved by the FDA for skin use in the United States in 2018. RCM acceptance and use with EMPD is limited. Currently Memorial Sloan Kettering Cancer Center (MSKCC) in New York is the only medical institution in the United States with an EMPD diagnostic program.