Evaluation of the clinical practicability of intraoperative optical imaging comparing three different camera setups

Abstract

Intraoperative optical imaging (IOI) is a method to visualize functional activated brain areas during brain surgery using a camera system connected to a standard operating microscope. Three different high-resolution camera systems (Hamamatsu EB-CCD C7190-13W, Hamamatsu C4742-96-12G04, and Zeiss AxioCam MRm) have been evaluated for suitability to detect activated brain areas by detecting stimulation-dependent blood volume changes in the somatosensory cerebral cortex after median nerve stimulation. The image quality of the camera systems was evaluated in 14 patients with tumors around the somatosensory cortex. The intraoperative images of the brain surface were continuously recorded over 9 min. With all three camera systems, the activity maps of the median nerve area could be visualized. The image quality of a highly sensitive electron-bombarded camera was up to 10-fold lower compared with two less sensitive standard cameras. In each IOI-positive case, the activated area was in accordance with the anatomical and neurophysiological location of the corresponding cortex. The technique was found to be very sensitive, and several negative influencing factors were identified. However, all possible artifacts seem to be controllable in the majority of the cases, and the IOI method could be well adapted for routine clinical use. Nevertheless, further systematic studies are needed to demonstrate the reliability and validity of the method.

Photon Counting Imaging with an Electron-Bombarded Pixel Image Sensor

“…In X-ray digital radiography and computed tomography, the low light level imaging capability of an EBCCD allows the reduction of the irradiation dose to the patient [ 18 , 19 ]. EBCCDs have also been evaluated for visualising stimulated functional brain areas during surgery [ 16 ].…”

“…Single photon detection is also possible with electron-bombarded (EB) sensors, where a photocathode is placed in front of the sensor, and a single photoelectron is accelerated through a high voltage directly into a solid state sensor. EB sensors are conceptually similar to old silicon intensified target television cameras, and have found applications in microscopy [ 12 , 13 ] and biological low-light imaging [ 14 , 15 , 16 ], optical spectroscopy [ 17 ] and radiography [ 18 , 19 ]. The advantages of EB sensors over intensified camera systems include reduced sensor size and weight, increased sensitivity and dynamic range, faster response time, and better contrast and resolution.…”

Intraoperative optical imaging in neurosurgery

“…On the other hand, a suitable camera setup with an easy and safe handling of the equipment is required for any intraoperative neurosurgical application. Therefore, in the third paper of this journal, Sobottka et al [ 6 ] describe three different high-resolution camera systems connected to the standard operating microscope. The systems are evaluated in 14 brain tumor patients and prove suitability to detect activated brain areas in the somatosensory cerebral cortex after median nerve stimulation.…”

“…The systems are evaluated in 14 brain tumor patients and prove suitability to detect activated brain areas in the somatosensory cerebral cortex after median nerve stimulation. Several possible causes and influencing factors for no or negative optical imaging results were observed that, however, could be controlled with a suitable image acquisition and data analysis technique in the great majority of cases [ 6 ]. Recently, it could be shown that intraoperative optical imaging is highly reliable for the identification and visualization of functionally intact somatosensory cortex with a sensitivity of 94.4% and a specificity of close to 100% [ 7 ].…”

“…In the fourth article of this journal [8], for the first time the functional integrity of the visual cortex was mapped in a brain tumor patient after visual stimulation of the eyes using strobe-light flashes. Using the previously described contact-free imaging technique [3,6,7], the individual visual cortex of the patient could be visualized on the surgically exposed brain surface. The computed activity maps were reproducible using independent image acquisitions.…”