Accounting for Truncation Artifacts in Angiographic Perfusion.

Unlocking perfusion metrics from routine digital subtraction angiography could transform how neurovascular disease is managed. Truncation artifact, defined as premature termination of image acquisition, is a key source of error in CT and MR perfusion imaging. However, length requirements for deriving perfusion metrics from angiography remain undefined. This study investigates the minimum image acquisition length required for interpreting mean transit time from digital subtraction angiography. We analyzed 55 outpatient angiograms performed for surveillance an average of 687 days after aneurysmal rupture. Truncation artifact was simulated by progressively shortening the angiography runs after bolus arrival. A gamma-variate function was used to assess if extrapolation of the truncated data could approximate full length acquisitions. Extrapolation of the truncated datasets with the gamma-variate function produced highly reliable estimates of the mean transit time with at least seven seconds of post-bolus data (mean difference between truncated/extrapolated MTT and original MTT 0.003 ± 0.047 s, mean ± SD). The fraction of pixels fit by the gamma-variate function was also sensitive to truncation and at least seven seconds of data was required to fit > 90% of the pixels. These findings provide a framework for evaluating the adequacy of image acquisition time and lay the foundation for retrospective perfusion analysis using digital subtraction angiography.