Role of Permeability Surface Area Product in Grading of Brain Gliomas using CT Perfusion

Abstract

Purpose The aim of this study was to evaluate the role of permeability surface area product in grading brain gliomas using computed tomography (CT) perfusion Materials and Methods CT perfusion was performed on 33 patients with brain glioma diagnosed on magnetic resonance imaging. Of these, 19 had high-grade glioma and 14 had low-grade glioma on histopathological follow-up. CT perfusion values were obtained and first compared between the tumor region and normal brain parenchyma. Then the relative values of perfusion parameters were compared between high- and low-grade gliomas. Cut-off values, sensitivity, specificity, and strength of agreement for each parameter were calculated and compared subsequently. A conjoint factor (permeability surface area product + cerebral blood volume) was also evaluated since permeability surface area product and cerebral blood volume are considered complimentary factors for tumor vascularity. Results All five perfusion parameters namely permeability surface area product, cerebral blood volume, cerebral blood flow, mean transit time, and time to peak were found significantly higher in the tumor region than normal brain parenchyma. Among these perfusion parameters, only relative permeability surface area product and relative cerebral blood volume were found significant in differentiating high- and low-grade glioma. Moreover, relative permeability surface area product was significantly better than all other perfusion parameters with highest sensitivity and specificity (97.74 and 100%, respectively, at a cut-off of 9.0065). Relative permeability surface area product had a very good agreement with the histopathology grade. The conjoint factor did not yield any significant diagnostic advantage over permeability surface area product. Conclusion Relative permeability surface area product and relative cerebral blood volume were helpful in differentiating high- and low-grade glioma; however, relative permeability surface area product was significantly better than all other perfusion parameters. Grading brain gliomas using relative permeability surface area product can add crucial value in their management and prognostication; hence, it should be evaluated in the routine CT perfusion imaging protocol.

Keywords: CT perfusion; brain glioma; cerebral blood flow; cerebral blood volume; conjoint factor; mean transit time; permeability surface area; time to peak.

Fig. 1

( A ) A 20-year-old male presented with pilocytic astrocytoma (World Health Organization grade I). T2-weighted imaging, ( B ) histopathology, ( C ) computed tomography perfusion (CTP) maps, ( D ) and CTP parameters ( D ). CBF, cerebral blood flow; CBV, cerebral blood volume; MIP, maximum intensity projection; MTT, mean transit time; PMB, permeability; TTP, time to peak.

Fig. 2

( A ) A 46-year-old male presented with diffuse astrocytoma (World Health Organization grade II). T2-weighted imaging, ( B )histopathology, ( C ) computed tomography perfusion (CTP) maps, ( D ) and CTP parameters. CBF, cerebral blood flow; CBV, cerebral blood volume; MIP, maximum intensity projection; MTT, mean transit time; PMB, permeability; TTP, time to peak.

Fig. 3

( A ) A 58-year-old female presented with oligodendroglioma (World Health Organization grade II). T2-weighted imaging, ( B ) histopathology, ( C ) computed tomography perfusion (CTP) maps, ( D ) and CTP parameters. CBF, cerebral blood flow; CBV, cerebral blood volume; MIP, maximum intensity projection; MTT, mean transit time; PMB, permeability; TTP, time to peak.

Fig. 4

( A ) A 42-year-old male presented with anaplastic oligodendroglioma (World Health Organization grade III). T2-weighted imaging, ( B ) histopathology, ( C ) computed tomography perfusion (CTP) maps, ( D ) and CTP parameters. CBF, cerebral blood flow; CBV, cerebral blood volume; MIP, maximum intensity projection; MTT, mean transit time; PMB, permeability; TTP, time to peak.

Fig. 5

( A ) A 21-year-old male presented with nonenhancing anaplastic astrocytoma (World Health Organization grade III). T2-weighted imaging, ( B ) histopathology, ( C ) computed tomography perfusion (CTP) maps, ( D ) and CTP parameters. CBF, cerebral blood flow; CBV, cerebral blood volume; MIP, maximum intensity projection; MTT, mean transit time; PMB, permeability; TTP, time to peak.

Fig. 6

( A ) A 60-year-old male presented with enhancing anaplastic astrocytoma (World Health Organization grade III). T2-weighted imaging, ( B ) histopathology, ( C )computed tomography perfusion (CTP) maps, ( D ) and CTP parameters. CBF, cerebral blood flow; CBV, cerebral blood volume; MIP, maximum intensity projection; MTT, mean transit time; PMB, permeability; TTP, time to peak.

Fig. 7

( A ) A 45-year-old male presented with glioblastoma (World Health Organization grade IV). T2-weighted imaging, ( B ) histopathology, ( C ) computed tomography perfusion (CTP) maps, ( D ) and CTP parameters. CBF, cerebral blood flow; CBV, cerebral blood volume; MIP, maximum intensity projection; MTT, mean transit time; PMB, permeability; TTP, time to peak.

Fig. 8

Comparison of area under curve of permeability surface area product with other perfusion parameters to predict high-grade from low-grade gliomas. CBF, cerebral blood flow; CBV, cerebral blood volume; IQR, interquartile range; MTT, mean transit time; TTP, time to peak; PS, permeability surface area; ROC, receiver operating characteristic.