The present invention relates to a device for fixation to a patient during neurological diagnosis, therapy or surgery, in particular during MRI diagnosis. For retrieval, the aircraft drops a weighted cable, and pulls it at low relative speed into a broad aperture of the apparatus. The cross-section of the horizontal handgrip rungs is substantially round and should not exceed 2 inches in diameter. The source driver further comprises a control circuit for generating the control signal, the control circuit comprising: a delay circuit delaying a switch signal and generating a delayed switch signal; and a multiplexer selecting one of the switch signal and the delayed switch signal in response to a selection signal and outputting the selected signal as the control signal. Information concerning the sensed temperature is sent to a regulator which derives the local power supply voltage from the master power supply voltage, Vcc, of the integrated circuit. Then, image data corresponding to the illumination field and the illumination structures may be received and a feature of the article may be analyzed based on the illumination field and the illumination structures.