Transluminescence (also called “transillumination“) has been used in medicine as a complement to radiography and other imaging techniques. Basically, it uses a beam of visible light to analyse the opacity patterns of solid object, associated with its thickness or composition. It was used in early craniological studies, and it is practical when you can’t rely on computed tomography. Putting a light behind an object, thinner or less dense areas will transmit more light than thicker or denser parts. We have tried to evaluate the actual efficiency of this methods designing a basic equipment for trans-luminescence, and appling this technique to a sample of robust modern humans sample. The equipment was made with two LED bulbs located on a 1.5 x 2.0 cm PCB (printed circuit board). The pieces were connected to a flexible aluminium arm, joined to a support of the same material which also contained the battery power source. The high luminescence LEDs requires thermal management, so it was necessary to attach an external ventilation system to the PCB bottom. The luminous flux was provided by two Cool-White LEDs, of 1500 lumens each, according to their data sheet specifications. The predominant wavelengths were 450 nm and 600 nm, with a minimum peak at 490 nm and the CCT (correlated color temperature) was in the range of 5000-8300 K. The equipment was introduced into ten skulls, males and females of a modern European population. Although they belong to a recent population, the skulls were robust and heavy, suggesting thick walls and dense bones. In most individuals only the vertex, pterion, and lower part of the temporal squama display a visible and patent light signal. In some cases part of the imprints of the middle meningeal vessels were visible. Generally, it seems that this approach is not much informative, at least with skulls presenting a robust morphology.
Gizéh Rangel de Lázaro