gms | German Medical Science

Objective: Intraoperative ultrasound (IOUS) helps to estimate the extent of resection and to image tumor remnants in glioma surgery. However, it has been demonstrated that IOUS images obtained within radiated cerebral tissue may be very difficult to interprete and boundaries are ill-defined. Aim of this study was to investigate whether: 1. IOUS is capable to navigate the surgeon towards the tumor as seen in the preoperative MRI image. 2. IOUS can distinguish between a tumor margin and the surrounding tissue in these tumors.

Method: 18 Patients suffering from high-grade-gliomas, who were previously treated by operation and radiotherapy were enclosed in the study. Intraoperatively, two histopathologic samples were obtained: #1 was definded as unequivocal tumor tissue (according to the surgeons visual and tactile impression, led by the intraoperative landmarks such as the first tumour approach and by ultrasound). #2: a small tissue sample was obtained, when the surgeon was not sure about the dignity of the tissue and decided to stop the resection. This specimen was considered as boundary, “no appearant tumor tissue”. While obtaining #2, IOUS was not used for surgical decisions. The aspect of the ultrasound image was analysed semi-quantitatively.

Results: #1: Seventeen out of the 18 samples which were obtained out of “unequivocal tumour tissue” were classified as tumor on histopathological examination. All samples were resected from tissue, which had a hyperechoic aspect on ultrasound examination. #2: Four samples were taken from resection borders, which were isoechoic to brain on ultrasound, whereas fourteen were slightly hyperechoic on IOUS. Isoechoic as well as slightly hyperechoic tisues harboured all possible histologies, i.e. tumor, infiltration or no tumor.

Conclusions: In our study on 18 patients, we proved that during surgery of relapsing, radiated gliomas, IOUS is not capable to distinguish between tumor remnants or tumor-free tissue. Even isoechoic tissue can contain tumor tissue. Thus, resection control is not possible. The tumor core could be identified as hyperechoic tissue in all cases. Navigation towards the core of the tumor can be performed by using IOUS.