Comparison of normalized cerebral blood flow between different post-processing methods of dynamic susceptibility contrast perfusion-weighted imaging and arterial spin labeling in gliomas with different grading

Abstract

Background: Two post-processing methods of dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI), arterial input function (AIF) and gamma-variate fitting (GVF), can both derive cerebral blood flow (CBF). Moreover, AIF can provide T2* and T1 leakage indicators. This study aimed to compare the consistency of normalized CBF between different post-processing methods of DSC-PWI and arterial spin labeling (ASL) in gliomas, and take the quantitative metrics percentage of signal recovery (PSR) as a reference to verify the value of T2* and T1 leakage indicators in characterizing leakage effect and evaluating the grading of gliomas.

Methods: From 1 January 2020 to 15 December 2023, 56 consecutive inpatients were retrospectively enrolled, comprising 24 patients with low-grade glioma (LGG) and 32 patients with high-grade glioma (HGG). The normalized CBF was derived from AIF, GVF and ASL. The T2* and T1 leakage indicators of AIF were graded by 4-point scale. The consistency and difference of normalized CBF between DSC-PWI and ASL were tested by linear correlation/regression analysis, Bland-Altman plots, and Student's t-test. The correlation between the difference of point for both leakage indicators and PSR was tested by Spearman correlation analysis, then inter-group difference of PSR was compared by t-test. The intra-group and inter-group differences of point for T2* and T1 leakage indicators were compared by χ²/Fisher's exact test.

Results: The normalized CBF derived from AIF and GVF were correlated with ASL in both groups (all r>0.7, all P<0.001), and linear regressions were not significantly different in each group (all P>0.05). The difference of normalized CBF between ASL and AIF in the HGG group was larger than that in the LGG group (P=0.017); however, the difference of normalized CBF between ASL and GVF was not significant (P=0.085). The strong correlation between the difference of point for both leakage indicators and PSR was verified (r=-0.739, P<0.0001), and the HGG group was shown to have higher PSR compared with the LGG group (t=2.043, P=0.04). The comparison of intra-group and inter-group differences in T2* leakage and T1 indicators showed that the HGG group was more prone to T1 leakage than the LGG group (P<0.05), and weight of T1 leakage was greater than that of T2* leakage (χ²=11.28, P=0.004).

Conclusions: The normalized CBF derived from DSC-PWI has good consistency with ASL in gliomas, regardless of post-processing methods. GVF can provide less bias of normalized CBF between HGG and LGG groups. However, T2* and T1 leakage indicators of AIF can be utilized as a surrogate of PSR to characterize both leakage effects and evaluate glioma grading.

Keywords: Cerebral blood flow (CBF); T1 leakage; T2* leakage; arterial spin labeling (ASL); dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI).

Figure 1

The flowchart of enrolled patient in the study. ASL, arterial spin labeling; LGG, low-grade glioma; HGG, high-grade glioma; MRI, magnetic resonance imaging.

Figure 2

The TIC derived from AIF and GVF of the three representative cases were presented (the yellow dotted line represents raw TIC and the pink dotted line represents the corrected TIC. The blue or gray dotted lines represent TIC of mirror region of interest). The TIC of patient with pilocytic astrocytoma graded as LGG, diffusion astrocytoma graded as HGG, and glioblastoma graded as HGG present balanced (A), sightly descending (B), and markedly ascending (C) after the negative enhancement. TIC, time-intensity curve; AIF, arterial input function; GVF, gamma-variate fitting; LGG, low-grade glioma; HGG, high-grade glioma.

Figure 3

The fused images of T2* and T1 leakage indicators obtained from the 3 representative cases with LGG (A,D), HGG graded as 4 (B,E), and HGG graded as 3 (C,F), respectively, the leakage indicator maps were fused with T1WI (A-C) and GRE-EPI (D-F), respectively. The three gliomas were located in the left cerebral hemisphere, and the manually delineated ROI on the right cerebral hemisphere was the mirror ROI of the gliomas (blue lines). The point of both leakage indicators of three cases interpretated by two radiologists using 4-point scale is provided in the bottom of the drawing. The LGG (A,D) and HGG (B,E) exhibited positive difference of point between T2* leakage indicator and T1 leakage indicator, moreover, the other HGG (C,F) exhibited negative difference of point between both leakage indicators. LGG, low-grade glioma; HGG, high-grade glioma; T1WI, T1 weighted imaging; GRE-EPI, gradient recalled echo-echo planar imaging; ROI, region of interest; GR, gradient recalled.

Figure 4

The correlation and linear regression analysis of normalized CBF between AIF, GVF and ASL in LGG group (r=0.744, P<0.001; r=0.763, P<0.001) (A) and HGG group (r=0.871, P<0.0001; r=0.757, P<0.0001) (B). Meanwhile, there was no significant difference in linear regressions in LGG (F=0.456, P=0.503) and HGG groups (F=2.806, P=0.099). The solid line represents the regression equations lines, and the dashed line represents the 95% confidence interval of the regression equations. CBF, cerebral blood flow; ASL, arterial spin labeling; AIF, arterial input function; GVF, gamma-variate fitting; LGG, low-grade glioma; HGG, high-grade glioma; rCBF, relative cerebral blood flow.

Figure 5

Bland-Altman plots analysis of agreement of normalized CBF between AIF, GVF and ASL in LGG group (A,B) and HGG group (C,D). Compared with AIF (A,C) and GVF (B,D), ASL overestimates the normalized CBF in LGG and HGG groups, and the difference of normalized CBF, which is presented as mean ± standard deviation, between ASL and AIF was significant between LGG and HGG groups (0.02±0.49 vs. 0.28±0.29, P=0.017); however, the difference of normalized CBF between ASL and GVF was not significant between two groups (0.06±0.39 vs. 0.24±0.38, P=0.085). CBF, cerebral blood flow; AIF, arterial input function; GVF, gamma-variate fitting; ASL, arterial spin labeling; LGG, low-grade glioma; HGG, high-grade glioma.

Figure 6

The correlation between the difference of point for T2* and T1 leakage indicators and PSR is negative (r=−0.739, P<0.0001) (A), and the HGG with higher PSR compared with LGG (t=2.043, P=0.04) (B). *, P<0.05. The dashed blue line represents that the PSR is 1 (A). PSR, percentage of signal recovery; LGG, low-grade glioma; HGG, high-grade glioma.

Figure 7

The comparison of grading between T2* leakage and T1 leakage in LGG (A) and HGG (B), respectively. The difference of point between T2* leakage and T1 leakage is significant in HGG group (χ²=12.45, P=0.006); however, the difference of point between T2* leakage and T1 leakage is not significant in LGG group (χ²=3.700, P=0.296). LGG, low-grade glioma; HGG, high-grade glioma.

Figure 8

The comparison of point for T2* leakage indicator and T1 leakage indictor between LGG (A) and HGG (B), and the inter-group comparison of the difference of point between T2* leakage indicator and T1 leakage indicator (C). The proportion of gliomas with T2* leakage and T1 leakage in HGG group was larger than that without T2* leakage and T1 leakage in LGG group, respectively (all P<0.001) (A,B). The difference of point between T2* leakage and T1 leakage is significant between the LGG and HGG groups (χ²=11.28, P=0.004) (C). LGG, low-grade glioma; HGG, high-grade glioma.