Parametric color coding of digital subtraction angiography

Abstract

Background and purpose: Color has been shown to facilitate both visual search and recognition tasks. It was our purpose to examine the impact of a color-coding algorithm on the interpretation of 2D-DSA acquisitions by experienced and inexperienced observers.

Materials and methods: Twenty-six 2D-DSA acquisitions obtained as part of routine clinical care from subjects with a variety of cerebrovascular disease processes were selected from an internal data base so as to include a variety of disease states (aneurysms, AVMs, fistulas, stenosis, occlusions, dissections, and tumors). Three experienced and 3 less experienced observers were each shown the acquisitions on a prerelease version of a commercially available double-monitor workstation (XWP, Siemens Healthcare). Acquisitions were presented first as a subtracted image series and then as a single composite color-coded image of the entire acquisition. Observers were then asked a series of questions designed to assess the value of the color-coded images for the following purposes: 1) to enhance their ability to make a diagnosis, 2) to have confidence in their diagnosis, 3) to plan a treatment, and 4) to judge the effect of a treatment. The results were analyzed by using 1-sample Wilcoxon tests.

Results: Color-coded images enhanced the ease of evaluating treatment success in >40% of cases (P < .0001). They also had a statistically significant impact on treatment planning, making planning easier in >20% of the cases (P = .0069). In >20% of the examples, color-coding made diagnosis and treatment planning easier for all readers (P < .0001). Color-coding also increased the confidence of diagnosis compared with the use of DSA alone (P = .056). The impact of this was greater for the naïve readers than for the expert readers.

Conclusions: At no additional cost in x-ray dose or contrast medium, color-coding of DSA enhanced the conspicuity of findings on DSA images. It was particularly useful in situations in which there was a complex flow pattern and in evaluation of pre- and posttreatment acquisitions. Its full potential remains to be defined.

Fig 1.

A−D, Top row: AP and lateral left carotid angiograms pre- (A and B) and postinfusion (C and D) and angioplasty for treatment of subarachnoid hemorrhage vasospasm. Bottom row: Corresponding AP and lateral color-coded images of the DSA acquisitions shown in the top row. E−H, Pretreatment (E and F) and posttreatment (G and H). In addition to improvements in the caliber of the proximal arteries easily seen on the standard DSA images, the color-coded composites show faster and more complete contrast filling of the parenchyma. A red arrow (G) shows that a small middle cerebral artery has been occluded during the treatment. A wedge of no filling in this arterial distribution is easily seen on the color-coded image.

Fig 2.

A, AP and lateral color-coded images obtained before (left column) and after (right column) angioplasty and stent placement of a left middle cerebral artery stenosis. The posttreatment images clearly show faster arterial filling with greater opacification of the middle cerebral artery distribution. B, Color-coded images of lateral projections of the left internal carotid angiogram obtained before (left image) and after (right image) angioplasty and stent placement. Notice the greater extent of parenchyma opacification and more normal filling on the posttreatment image.

Fig 3.

AP and lateral DSA images from a right internal carotid angiogram from a patient with a large frontal AVM (top and bottom rows). AP and lateral color-coded images from these acquisitions (middle row). The complex circulation of this AVM is clearly depicted on the color-coded composite images.