Arrival time correction for dynamic susceptibility contrast MR permeability imaging in stroke patients

Abstract

Purpose: To determine if applying an arrival time correction (ATC) to dynamic susceptibility contrast (DSC) based permeability imaging will improve its ability to identify contrast leakage in stroke patients for whom the shape of the measured curve may be very different due to hypoperfusion.

Materials and methods: A technique described in brain tumor patients was adapted to incorporate a correction for delayed contrast delivery due to perfusion deficits. This technique was applied to the MRIs of 9 stroke patients known to have blood-brain barrier (BBB) disruption on T1 post contrast imaging. Regions of BBB damage were compared with normal tissue from the contralateral hemisphere. Receiver operating characteristic (ROC) analysis was performed to compare the detection of BBB damage before and after ATC.

Results: ATC improved the area under the curve (AUC) of the ROC from 0.53 to 0.70. The sensitivity improved from 0.51 to 0.67 and the specificity improved from 0.57 to 0.66. Visual inspection of the ROC curve revealed that the performance of the uncorrected analysis was worse than random guess at some thresholds.

Conclusions: The ability of DSC permeability imaging to identify contrast enhancing tissue in stroke patients improved considerably when an ATC was applied. Using DSC permeability imaging in stroke patients without an ATC may lead to false identification of BBB disruption.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. The top row of images show a stroke on DWI/ADC which has some enhancement on post contrast T1 imaging.

The bottom row shows the perfusion deficit on a TTP map, the permeability image when not corrected for arrival time, and the permeability image after arrival time correction. The green circles show corresponding areas of contrast leakage on the T1 post contrast and ATC permeability images. (DWI = diffusion weighted image, ADC = apparent diffusion coefficient, PWI = perfusion weighted image, TTP = time to peak, ATC = arrival time corrected).

Figure 2. The two graphs show the ΔR2* for non-enhancing (control) and enhancing hypoperfused regions before and after arrival time correction (ATC).

In the first graph, due to even a small delay in time-to-peak, the control signal appears to approach baseline faster thus obscuring the phenomenon being measured. However, in the second graph, after the ATC has been applied to the control, it becomes evident that the enhancing region signal is approaching the baseline faster due to the T1 effect of contrast accumulation in the parenchyma.

Figure 3. The receiver-operator characteristic (ROC) curves, which demonstrate the ability to correctly identify enhancing tissue, are plotted before and after arrival time correction (ATC).

Prior to correction the technique performs worse than random chance at some thresholds due to perfusion deficits.