[Contact gel as a source of error in roentgen images of the skull]

This paper sounds a note of warning in respect of simulation of non-existent osseous densifications or calcifications on x-ray film due to the use of contact gels that are common in sonography and electro-encephalography for the fixation of leads. If lumps of these gels adhere to the scalp, especially to the hair of the head and thus remain unnoticed, their roentgenographic density will falsify the subsequent x-ray (for example, marginal calcifications are simulated that are not necessarily visualised on the second plane).