gms | German Medical Science

Objective: Intraoperative ultrasound (iUS) is an often employed surgical tool to increase extent of resection. Its navigated use and the option of a full 3D image acquisition allows for an “offline” use of the ultrasound images in the navigation system may facilitate detection of residual tumor. The aim of the study is to assess quality, accuracy and benefit of navigated 2D and 3D ultrasound for intraaxial tumor surgery in a prospective study.

Methods: As part of a prospective study protocol adult patients with a metastasis or WHO°II-IV glioma and intended gross total resection (GTR) are consecutively enrolled. Intraoperatively a 2D and 3D iUS based resection is performed (iUS=BK Medical; navigation software=Brainlab Origin). After assumed GTR, iMRI is performed to assess extend of resection. During surgery image quality, clinical benefit and navigation accuracy are recorded based on a standardized protocol using Likert’s scales from 1(best)-6(worst). KPS score and NANO score (Neurological Assessment in Neuro-Oncology) are also assessed. We used a descriptive assessment and Wilcoxon’s test to compare 2D and 3D results and Sign test for connected samples.

Results: A total of 8 consecutive patients were enrolled, 5 harboring a glioma and 3 a metastasis. Mean ratings of image quality in 2D iUS was significantly higher than 3D iUS (1.6 vs. 2.5 p>0.001). There was no relevant decrease during the course of surgery both in 2D and 3D (p>0.46). Benefit was rated 2.4 in 2D iUS and 3.0 in 3D iUS. No significant difference was found (p=0.19). Benefit remained stable in 2D while there was a slight decrease in 3D after complete tumor resection which was not statistically significant (p=0.28). Accuracy was similar both in 2D (mean 2.1) and 3D (mean 2) (p=0.5). Two out of 8 patients had a small remnant (mean 0.48 cm³) that was not appreciated with iUS. No significant differences between average NANO and KPS scores before and after surgery were recorded (2.7 vs. 2.9 and 78.7 vs. 77.5, respectively).

Conclusion: 3D reconstructed iUS allows for an accurate intraoperative update of imaging with slightly lower image quality than 2D US, but still rated as “satisfying” or “good”. Our preliminary data suggest that benefit and accuracy of 2D and 3D iUS navigation do not undergo significant variations during tumor resection. The future phase of the study may further elucidate impact of 3D navigated iUS on the extent of tumor resection by a retrospective matched pair control group using no iUS.

Figure 1 [Fig. 1], Figure 2 [Fig. 2]