gms | German Medical Science

Objective: Intraoperative 1.5T high-field MRI (iMRI) is a unique imaging tool that contributes to an increased extent of resection (EOR) in glioma surgery. In routine use, continued resections after iMRI are frequent and can be observed in up to 70% of cases. In this study we intended to analyze in how far surgical experience influences the rate of additional resections and how reliably the surgeon can predict residual tumor on iMRI.

Method: IMRI cases operated by consultant neurosurgeons during 2011/2012 were identified from a prospective data-base. For each surgeon, frequencies of additional resections after iMRI were calculated and compared with the perception of EOR documented prior to iMRI. In a contingency table, positive predictive values (PPV) and negative predictive values (NPV) of the surgeon’s perception were calculated.

Results: Seven neurosurgeons (A-G) treated 190 gliomas WHO°I-IV of various locations (n; A=12, B=29, C=18, D=15, E=18, F=87, G=11). Mean initial tumor volumes of surgeons A-G showed no significant difference (33,09±28,83cm³, p=0,66). Resections were continued in 68,8% after iMRI, surgeon-specific frequencies showed no significant difference (A=75%, B=62,1%, C=61,1%, D=80%, E=72,2%, F=67,8%, G=63,6%). Before iMRI, an additional resection was expected in 46,4% of cases. When expected, resection was commonly continued after iMRI (PPV=83,3%; A=83,3%, B=77,8%, C=60%, D=80%, E=100%, F=87,2%, G=60%). Against the surgeon’s initial expectation, resection was continued in 54,6% after iMRI. Consequently, NPV of the surgeon’s perception was low, i.e. overall NPV=45,4% (NPV; A=20%, B=75%, C=34%, D=22,2%, E=38,5%, F=51,1%, G=33,3%). The distribution of NPVs among the surgeons involved points to a possible correlation with surgical experience (A, G vs. C, D, E vs. B, F; least vs. mid vs. most experienced, respectively). Mean final EOR was high and showed no significant difference between surgeons (99,4±1,69%, p=0,60).

Conclusions: As a surgical tool, iMRI reliably guides surgeons of different experience levels towards the goal of achieving a maximized EOR in glioma surgery. Frequency of additional resections after iMRI is high in all surgeons involved, regardless of their experience. The ability to evaluate the resection progress seems to increase with surgical experience, but EOR still is regularly overestimated from the intraoperative impression. This frequently has to be revised after iMRI and resection is extended against the surgeon’s expectation in 54,6% of cases.