Development of modified Intraoperative Examination Monitor for Awake Surgery (IEMAS) system for Awake craniotomy during brain tumor resection

Gliomas represent the most frequent type of primary intracranial tumors, which originate from the brain tissue itself, have infiltrative growth, unclear borders, and usually affect functionally-important cerebral structures. From March 2000 till March 2010, 839 neurosurgical procedures directed on resection of such neoplasms were performed in the intelligent operating theater of Tokyo Women's Medical University with the use of intraoperative MRI, real-time updated neuronavigation system, and Hi-vision operative microscope. To facilitate maximal possible tumor resection with minimal risk of neurological morbidity a special device, called Intraoperative Examination Monitor for Awake Surgery (IEMAS) was developed by us. It provides an opportunity to visualize a wide spectrum of inraoperative information related to condition of the patient, nuances of the surgical procedure, and details of the cortical mapping. The wide set of both anatomical and functional parameters, such as view of the patient's mimic and face movements during answering on the specific questions, type of examination test, position of the surgical instruments, parameters of the bispectral index monitor, and general view of the surgical field through the operating microscope and/or endoscope, is presented compactly in one screen with several displays, which allows fast integrated real-time analysis of the multiple data, nearly without interruption of the surgical manipulations. All members of the surgical team can share this information using several in-room liquid crystal displays. However, the initially designed IEMAS system was occasionally affected by interruption or detachment of the connecting cables, which could interfere with effective advancement of the surgical procedure. To avoid this problem a modified device was created. Its specific feature is wireless information transmitting function attained by incorporation of transmitters with a frequency range of 2.4 GHz. The clinical testing of this system was initiated on February 1, 2010, but quickly revealed crossed line effect between transmitters and receivers. To overcome this obstacle and to isolate transmitters, one channel was changed from wireless connection into wired, which resulted in significant improvement of the clearness of both transmitted images and sounds, and provides an opportunity for effective clinical use of the device. In perspective we wish to make IEMAS system fully wireless, using several types of frequency range transmitters.