The CAM1 measures blood cell velocity using a low power near infrared laser. This is focused to a 10 micron diameter beam which can be positioned onto the apex of any capillary that is visible, or barely visible through the skin surface. An in built CCD camera allows continuous monitoring of the capillary position either on a separate monitor or optionally on the computer screen.

The low power laser beam is reflected by blood cells at the focal point moving perpendicular to the skin surface. The frequency of the reflected beam is Doppler shifted, the shift being directly proportional to the velocity of the reflecting blood cell. This is detected in the CAM1.

An IBM compatible computer fitted with CAM1 interface cards digitally processes the signals and provides the user display, control and data storage.

Windows based software provides a common easy to use graphical interface for the user and makes use of Windows features for simple transfer of data between applications such as spreadsheets, word processors and graphic processing programs.

The CAM1 measures velocities from 0.02 mm/s to 14.6 mm/s. In practice the lower limit is determined by low frequency tissue movements which makes it difficult to determine velocities below about 0.1 mm/s. Velocities are measured with a resolution of eight bits ( one part in 256 ) of full scale. Full scale is selectable in steps from 1mm/s to 14 mm/s.

The CAM1 has a very well defined probing volume of only about 10 microns diameter so the velocity of a single capillary can be measured. It is very quick and easy to move between adjacent capillaries to acquire a number of measurements which can be averaged to give a more representative value.

The CAM1 calculates 20 independent measurements per second. This means that even the velocity variations from the cardiac pulse can be followed. The presence of a clean cardiac pulse in a measurement gives added confidence of and easy discrimination between a good signal and movement artifact or signal dropout. All the traces shown are raw data without any additional filtering or smoothing except where stated. The fast response time also means that movement artifacts do not influence any following readings, and recovery is instant.

Because the CAM1 measures velocities perpendicular to the surface , a wider range of measurement sites becomes possible. Anywhere where a section of capillary travels perpendicular to the surface then a measurement is possible. This does not need to be a long section, even a small kink in a capillary lying parallel to the surface can become a measurement point.

Since the CAM1 only requires an image for positioning the measurement point then image quality is not critical. Measurements on a wider range of capillaries is possible, and larger number of subjects become suitable. Also no disturbing preconditioning of the tissue surface is required just a drop of oil warmed to skin temperature to reduce surface reflections.

See the VCS Video Capillaroscopy pages to see images of capillaries taken with the CAM1. In some, individual red blood cells can be distinguished.

Here is a quick demonstration video on using the CAM1 demo1.mpg. (size 53 Mbyte). Apologies for the poor sound quality. We'll hopefully put up a better demo soon!