Purpose Color coding of digital subtraction angiography (DSA) is a temporal and intensity post-processing color coded algorithm that generates a single composite image containing all information contained in a standard DSA acquisition. The composite image enhances the conspicuity of findings on DSA images done before and after therapeutic interventions. To date, analysis of images processed with this algorithm has been entirely qualitative. In a series of patients, we sought to add quantification to the color coded images.
Materials and methods Angiographic acquisitions were obtained by a single operator using the same volume of contrast medium injected through a catheter at the same location before and after treatment. Using the time to peak parameter, the effect of neuroendovascular treatment of cerebral artery vasospasm and intracranial stenosis was quantified in three patients. A time contrast concentration curve was generated from a group of pixels in the extracranial segment of the vertebral artery or internal carotid artery (proximal to the area of pathology) to confirm that delivery of the contrast bolus was equivalent before and after treatment. Next, a time contrast concentration curve from a group of pixels in a vessel distal to the lesion was used to quantify the treatment effect. Quantitative analysis was obtained by directly comparing the time to peak before and after treatment at these two locations.
Results Color coded DSA was quantified in two patients treated for vasospasm and in one with an intracranial stenosis. In all cases, composite color images were generated with the only variable between pretreatment and post-treatment images being the treatment itself. In all cases, time–concentration curves distal to the lesion demonstrated quantifiable changes in time to peak following treatment. Overall, there was a 1–1.25 s decrease in time to peak after verapamil infusion for vasospasm. There was a 0.5 s decrease in time to peak after angioplasty for intracranial stenosis.
Conclusions Color coded DSA not only presents all the information from a standard acquisition as a composite qualitative image but also contains readily quantifiable parametric data. The full usefulness of these data remains to be determined and is the topic of ongoing investigations. Furthermore, animal experiments on the effects of varying stenosis on quantitative data proximal and distal to the stenosis are ongoing and will be presented.
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Competing interests None.
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