Predicting Grade of Cerebral Glioma Using Vascular-Space Occupancy MR Imaging

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Fig 1.
Schematic diagram of the VASO scans and the VASO pulse sequence. VASO uses a nonselective inversion recovery sequence, and the TI is chosen to null the precontrast blood signal intensity. Two scans using identical parameters are performed before and after the contrast agent administration, the signal intensity difference of which can be used to calculate absolute CBV.
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Fig 2.
T2-weighted, CE-T1-weighted, and FLAIR images, as well as VASO maps for WHO grade II, III, and IV gliomas.
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Fig 3.
Three VASO indices, that is, VASO_Tumor, VASO_Contra, and VASO_Ratio, in grade II (n = 9), III (n = 20), and IV (n = 10) gliomas. Error bars indicate SDs. The units for VASO_Tumor and VASO_Contra are percentages. The index VASO_Ratio is dimensionless. Significant differences (P < .05) for each pair are indicated by asterisks.
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Fig 4.
ROC curves using VASO_Tumor or VASO_Ratio. The sensitivity and specificity (in fractions) in terms of distinguishing grade II from higher-grade (grade III and grade IV) tumors are plotted at different thresholds. If the 2 categories have identical distributions of the VASO parameters, the ROC curve would have been a 45° straight line (dotted line). The AUCs are 0.974 and 0.985 for VASO_Tumor and VASO_Ratio, respectively.

Table 1:

Mean ± SD of each of the VASO and DSC parameters stratified by tumor grade

Grade	VASO_Tumor, %	VASO_Contra, %	VASO_Ratio	CBF, mL of Blood per 100 g of Tissue per Minute	CBV, mL of Blood per 100 g of Tissue	rCBV	K^Trans, s⁻¹	V_P, %	MTT, s
II	7.5 ± 3.2	5.4 ± 2.9	1.5 ± 0.5	60.1 ± 25.8	4.2 ± 1.9	1.4 ± 0.5	0.011 ± 0.009	2.0 ± 1.2	4.2 ± 0.6
III	41.3 ± 23.6	6.3 ± 4.2	8.2 ± 5.5	197.8 ± 80.7	15.3 ± 6.9	3.8 ± 1.4	0.019 ± 0.018	2.9 ± 2.3	4.8 ± 1.0
IV	56.1 ± 32.7	4.8 ± 2.3	11.6 ± 3.7	251.9 ± 160.8	17.9 ± 9.5	5.7 ± 2.1	0.022 ± 0.037	3.3 ± 2.7	4.5 ± 0.8

Note:—VASO_Tumor indicates vascular-space occupancy values in the tumoral regions; VASO_Contra, vascular-space occupancy signal intensity in regions contralateral to tumor; VASO_Ratio, ratio between tumor side and contralateral side of the vascular-space occupancy; CBF, cerebral blood flow; CBV, cerebral blood volume; rCBV, relative cerebral blood volume; K^trans, vascular permeability; V_p, fractional plasma volume; MTT, mean transit time.

Table 2:

P values from pairwise comparison between different tumor grades using the VASO and DSC parameters

Variable	VASO_Tumor	VASO_Contra	VASO_Ratio	CBF	CBV	rCBV	K^trans	V_P	MTT
II vs III	0.0003^*	0.685	0.0002^*	<0.0001^*	<0.0001^*	<0.0001^*	0.248	0.423	0.170
II vs IV	<0.0001^*	0.508	<0.0001^*	0.0006^*	0.0004^*	<0.0001^*	0.858	0.400	0.509
III vs IV	0.194	0.356	0.0098^*	0.442	0.650	0.025^*	0.367	0.787	0.522

Note:—VASO_Tumor indicates vascular-space occupancy values in the tumoral regions; VASO_Contra, vascular-space occupancy signal intensity in regions contralateral to tumor; VASO_Ratio, ratio between tumor side and contralateral side of the vascular-space occupancy; CBF, cerebral blood flow; CBV, cerebral blood volume; rCBV, relative cerebral blood volume; K^trans, vascular permeability; V_p, fractional plasma volume; MTT, mean transit time.
* Significant differences (P < 0.05, not corrected for multiple comparisons).