CT perfusion with acetazolamide challenge in C6 gliomas and angiogenesis

Abstract

Background: This study was performed to investigate the correlation between CT perfusion with acetazolamide challenge and angiogenesis in C6 gliomas.

Methods: Thirty-two male Sprague-Dawley rats were evaluated. The rats were divided randomly to four groups: eight rats with orthotopically implanted C6 gliomas at 10-days old (Group A), eight rats with gliomas at 14-days old (Group B), eight rats with gliomas at 18-days old (Group C), eight rats with orthotopically injected normal saline served as controls. CT perfusion was performed before and after administration of acetazolamide. Changes in perfusion parameters due to acetazolamide administration were calculated and analyzed.

Results: Elevated carbon dioxide partial pressure and decreased pH were found in all 32 rats post acetazolamide challenge (P<0.01). Cerebral blood flow(pre-challenge) was increased in group C (95.0±2.5 ml/100 g/min), as compared to group B (80.1±11.3 ml/100 g/min) and group A (63.1±2.1 ml/100 g/min). Cerebral blood flow percentage changes were detected with a reduction in group C (54.2±4.8%) as compared to controls (111.3±22.2%). Cerebral blood volume(pre-challenge) was increased in group C (50.8±1.7 ml/100 g), as compared to group B (45.7±1.9 ml/100 g) and group A (38.2±0.8 ml/100 g). Cerebral blood volume percentage changes were decreased in group C (23.5±4.6%) as compared to controls (113.5±30.4%). Angiogenesis ratio = [(CD105-MVD) / (FVIII-MVD)] ×100%. Positive correlations were observed between CD105-microvessel density, angiogenesis ratio, vascular endothelial growth factor, proliferation marker and cerebral blood flow(pre-challenge), cerebral blood volume(pre-challenge). Negative correlations were observed between CD105-microvessel density and cerebral blood flow percentage changes (P<0.01, correlation coefficient r=-0.788), cerebral blood volume percentage changes (P<0.01, r=-0.703). Negative correlations were observed between angiogenesis ratio, vascular endothelial growth factor, proliferation marker and cerebral blood flow percentage changes, cerebral blood volume percentage changes.

Conclusion: Our findings suggest that CT perfusion with challenge can provide new insight into non-invasive assessment of rat C6 glioma angiogenesis.

Fig 1. CT perfusion time density curves in a rat with C6 gliomas (group B) pre challenge.

ROI of the red artery curve was placed on the right middle cerebral artery. ROI of the blue vein curve was placed on the superior sagittal sinus. ROI of the yellow curve (curve one) was placed on C6 glioma. ROI of the green curve (curve two) was placed on contralateral normal brain tissue. Time density curves showed the peak of the yellow curve was higher than that of the green curve.

Fig 2. CT perfusion color maps in a rat with C6 gliomas (group B) pre and post acetazolamide challenge.

(A-C) Maximun intensity projection image, perfusion maps for cerebral blood flow, cerebral blood volume of C6 glioma pre acetazolamide stimuli. (D-F) Maximun intensity projection image, perfusion maps for cerebral blood flow, cerebral blood volume of C6 glioma post acetazolamide challenge. Glioma was obviously enhanced in maximum intensity projection map on right caudate area (A). Higher CBF of glioma on right caudate was shown on CBF map than contralateral normal tissue (B). Higher CBV of glioma on right caudate was shown on CBV map than contralateral normal tissue (C). CT perfusion maps post challenge showed higher density, CBF and CBV than pre challenge (D-F).

Fig 3. Correlation diagrams between CD105-MVD, VEGF and CBF percentage changes, CBV percentage changes.

Negative correlation was shown in C6 gliomas between CBF percentage changes and CD105-MVD (A). Negative correlation was shown in C6 gliomas between CBV percentage changes and CD105-MVD (B). Negative correlation was shown between CBF percentage changes and VEGF (C). Negative correlation was shown in C6 gliomas between CBV percentage changes and VEGF (D). The middle lines on each graph showed the mean value of correlation. The upper and lower lines which were on both sides of the middle lines on each graph showed the 95% confidence interval of the correlation.

Fig 4. Histologic images of group A, B and C.

CD105-MVD in rat C6 glioma group A(A), group B(B) and group C (C). VEGF in rat C6 glioma group A(D), group B(E) and group C (F). FVIII-MVD in rat C6 glioma group A(G), group B(H) and group C (I). Scale bar = 50um.