Efficacy of Perfusion Computed Tomography (PCT) in Differentiating High-Grade Gliomas from Low Grade Gliomas, Lymphomas, Metastases and Abscess

Abstract

Introduction: Tumoural angioneogenesis and its quantification are important in predicting the tumour grade and in the management with respect to the treatment available and to assess the response to treatment and the prognosis. It also plays major role in the growth and spread of tumours. Hence, a need arises for non-invasive in vivo methods to assess tumour angioneogenesis and tumour grade at the time of presentation and for monitoring the response during treatment and follow up. In this regard Perfusion Computed Tomography (PCT) can be easily added into routine CT studies to obtain such information on lesion physiology along with its morphology.

Aim: Prospective evaluation of the efficacy of PCT in differentiating high grade gliomas from low grade glioma lymphomas, metastases and abscess.

Materials and methods: Perfusion CT was performed in 68 patients (17 high-grade gliomas, 10 low-grade gliomas, 7 lymphomas, 27 metastases and 7 abscess). Perfusion parameters which include Cerebral Blood Volume (CBV), Cerebral Blood Flow (CBF), Mean Transit Time (MTT) and Time To Peak (TTP) were derived both from the lesion and the normal parenchyma and were Normalized (n) by obtaining the ratio. Statistical analysis for high grade versus low-grade gliomas, high grade gliomas versus lymphomas, metastases and abscess was performed.

Results: Difference in the mean nCBV and nCBF in high grade gliomas were statistically significant from low grade gliomas with cut off of > 3.07 for nCBV and > 2.08 for nCBF yielding good sensitivity and specificity. Difference in the mean nCBV and nMTT in the lymphomas were statistically significant from high grade gliomas (p<0.05) with cut off of <3.40 for nCBV and >1.83 for nMTT yielding good sensitivity and specificity. Difference in the mean nCBV and nMTT in the metastases were statistically significant from high grade gliomas (p<0.05) with cut off of >4.95 for nCBV and >1.88 for nMTT yielding a fair sensitivity and specificity. No statistical significant difference seen among the parameters in differentiating high grade gliomas and abscess.

Conclusion: Cerebral PCT greatly adds to the diagnostic accuracy when the diagnosis of a common intra-axial lesion based on morphological characters becomes uncertain.

Keywords: Cerebral blood flow; Cerebral blood volume; Mean transit time; Time to peak.

[Table/Fig-4]:

Boxplot showing the range of nCBV and nCBF among low- and high-grade tumours (HGG: High Grade Glioma, LGG: Low Grade Glioma).

[Table/Fig-5]:

ROC curves showing the area under the curve for nCBV (A) and nCBF (B) in differentiating high grade gliomas and low grade gliomas.

[Table/Fig-7]:

Boxplot showing the range of nCBV and nMTT among high-grade gliomas and lymphomas (HGG: high grade glioma).

[Table/Fig-8]:

ROC curves showing the area under the curve for nCBV (A) and nMTT (B) in differentiating high grade gliomas and lymphomas.

[Table/Fig-10]:

Boxplot showing the range of nCBV and nMTT among metastasis and high-grade gliomas (HGG: high grade glioma).

[Table/Fig-11]:

ROC curves showing the area under the curve for nCBV(A) and nMTT (B) in differentiating high grade gliomas and metastases.

[Table/Fig-13]:

Image [1] CT perfusion image showing histologically proven case of glioblastoma multiforme involving the right frontal lobe and the corpus callosum. Image (2) shows corresponding CBV, CBF, MTT and TTP colour maps of the lesion. Image (3) shows arterial (red), venous (blue), tumoural (yellow) and normal parenchymal (white) time attenuation curves. As compared to the normal parenchyma the lesion shows increased CBV, CBF, MTT & TTP values as seen in the ROI table.

[Table/Fig-14]:

Image (1) shows CT perfusion image showing histologically proven case of low grade glioma in the left frontal lobe. Image (2) shows corresponding CBV, CBF, MTT and TTP colour maps of the lesion. Image (3) shows arterial (red), venous (blue), tumoural (yellow) and normal parenchymal (light blue) time attenuation curves. As compared to the normal parenchyma the lesion shows mild increased CBV decreased CBF, increased MTT and TTP values as seen in the ROI table.

[Table/Fig-15]:

Image (1) shows CT perfusion image showing a histologically proven case of Primary CNS lymphoma in the left thalamus. Image (2) shows corresponding CBV, CBF, MTT and TTP colour maps of the lesion. Image (3) shows arterial (red), venous (blue), tumoural (yellow) and normal parenchymal (light blue) time attenuation curves. As compared to the normal parenchyma the lesion shows increased CBV, CBF, MTT and TTP values as seen in the ROI table.

[Table/Fig-16]:

Image (1) shows CT perfusion image showing metastatic lesions in bilateral parietal lobes in a patient with bronchogenic carcinoma. Image (2) shows corresponding CBV, CBF, MTT and TTP colour maps of the lesions. Image (3) shows arterial (red), venous (blue), tumoural (yellow) and normal parenchymal (light blue) time attenuation curves. As compared to the normal parenchyma the lesion shows increased CBV, CBF, MTT and TTP values as seen in the ROI table.

[Table/Fig-17]:

Image (1) shows CT perfusion image showing a proven case of abscess in the posterior fossa. Image (2) shows corresponding CBV, CBF, MTT and TTP colour maps of the lesion. Image (3) shows time attenuation curves of the artery (red), vein (blue), lesion (yellow) and normal parenchymal (light blue). As compared to the normal parenchyma the lesion shows increased CBV, CBF, MTT and TTP values as seen in the ROI table.