Interrater Reliability in the Measurement of Flow Characteristics on Color-Coded Quantitative DSA of Brain AVMs

cDSA with high variance among raters in MTT results. Left vertebral arteriogram in a lateral projection shows a cerebellar AVM with arterial supply from the left SCA and left PICA and venous drainage into vermian and tentorial veins. A and B, Raters 1 and 2 placed ROIs on the same vessels, the SCA and tentorial vein, at nearly the same location, yet the MTT for rater 1 (A) is 3.6 seconds, while the MTT for rater 2 is 0.7 seconds. The venous time-density curve for rater 1 (A) has a larger second peak, which increased the calculated venous TTP. Rater 1 (A) placed the ROI on a draining vein where it overlaps with a normal draining vein, and the second peak is a manifestation of the normal venous phase of the angiogram. C, Rater 3 selected an inferior vermian vein rather than a tentorial vein for venous ROI placement. D, Rater 4 selected the left PICA rather than the SCA for arterial ROI placement. Differences in ROI placement result in different time-density curves (E) and calculated AUCs (F).

cDSA with variation among raters in vessels selected for analysis. Left vertebral arteriogram in a lateral projection shows a right occipital lobe AVM supplied by the calcarine and parieto-occipital branches of the right PCA, with dominant drainage into 2 internal occipital veins superior to the nidus and minor drainage into a tentorial vein inferiorly. A, Rater 1 placed the arterial ROI on the calcarine branch of the PCA distal to the overlapping minor venous egress and placed the venous ROI on the more superior internal occipital vein. B, Rater 2 placed the arterial ROI on the calcarine branch of the PCA proximal to the overlapping minor venous egress and placed the venous ROI on the more superior internal occipital vein. C, Rater 3 placed the arterial ROI on the calcarine branch of the PCA proximal to the overlapping minor venous egress and placed the venous ROI on the more superior internal occipital vein, though distal relative to rater 2. D, Rater 4 placed the arterial ROI on the calcarine branch of the PCA distal to the overlapping minor venous egress, similar to rater 1. Rater 4 also placed the venous ROI on the more inferior internal occipital vein, unlike the other raters. Despite differences in the vessels selected for analysis, time-density curves (E) and AUCs (F) were largely reproducible because the ROIs were placed so close to the nidus by all raters.

Interrater agreement between 2 representative raters. The calculated MTTs for raters 1 and 2 were compared (horizontal axis = rater 1, vertical axis = rater 2). A dashed diagonal line represents perfect agreement between the 2 raters. When the same image, feeding artery, and draining vein are used for analysis, agreement improves. Similar interrater agreement was observed in other pair-wise comparisons of raters.

Variations in ROI placement can alter time-density curves and calculated peak times due to overlapping vessels. A right internal carotid arteriogram in a lateral projection demonstrates a right frontal lobe AVM supplied by the frontopolar branch of the right anterior cerebral artery with venous drainage into a frontal cortical vein, which drains into the superior sagittal sinus. A, Four arterial ROIs were placed along the course of the arterial feeder with varying proximity to the nidus. B, Four venous ROIs were placed along the course of the draining vein with varying proximity to the nidus. C, The resulting time-density curves are not reproducible. D, The resulting peak times are not reproducible.