4D-DSA: Development and Current Neurovascular Applications

Abstract

Originally described by Davis et al in 2013, 4D-Digital Subtraction Angiography (4D-DSA) has developed into a commercially available application of DSA in the angiography suite. 4D-DSA provides the user with 3D time-resolved images, allowing observation of a contrast bolus at any desired viewing angle through the vasculature and at any time point during the acquisition (any view at any time). 4D-DSA mitigates some limitations that are intrinsic to both 2D- and 3D-DSA images. The clinical applications for 4D-DSA include evaluations of AVMs and AVFs, intracranial aneurysms, and atherosclerotic occlusive disease. Recent advances in blood flow quantification using 4D-DSA indicate that these data provide both the velocity and geometric information necessary for the quantification of blood flow. In this review, we will discuss the development, acquisition, reconstruction, and current neurovascular applications of 4D-DSA volumes.

FIG 1.

4D-DSA reconstruction workflow. Starting at the upper left, projection images from a rotational acquisition are reconstructed into a 3D-DSA. Following a threshold approach, a constraint volume is generated, which provides the geometric information for the 4D-DSA. Combining the constraint volume with the angle-specific temporal information results in the volumetric, time-resolved 4D-DSA volume.

FIG 2.

Three views from 3D-DSA of a patient with an AVM supplied by the lenticulostriate arteries (upper row). While the anatomic detail is excellent, vascular overlap in and around the nidus makes it impossible to see the angioarchitecture and to understand the sequences of blood flow into and out of the AVM. Early timeframes of the 4D-DSA (lower row) show details of the AVM nidus that are not visible on 3D-DSA. Note the small aneurysm on one of the lenticulostriate arteries (white arrow). No intranidal aneurysms are seen. Although the 4D-DSA images provided here are at 1 angle (angle B), these images may be viewed at any desired angle at any time of bolus passage.

FIG 3.

Three 4D-DSA images from early timeframes (t1–t3) of the filling of an AVF located along the intracranial surface of the petrous bone (blue circle). t1 shows several small arteries supplying the AVF (blue arrow). In the image from t3, acquired less than a second later, these arteries are obscured. This information is helpful when trying to plan an endovascular approach to this abnormality.

FIG 4.

An anterior communicating artery aneurysm viewed from the anterior, posterior, and cranial-caudal positions of a 3D-DSA (upper row) and a 4D-DSA (lower row). The branches that obscure the view of the aneurysm (yellow circle) in the 3D-DSA are not yet filled in the 4D-DSA image, making the aneurysm neck and its relationship to adjacent branches visible. This information aids in the endovascular treatment of intracranial aneurysms.

FIG 5.

Simplified schematic of how flow is quantified using 4D-DSA: 1) Variations in the contrast density are due to the mixing of contrast with nonopacified blood at and downstream from the injection site with each cardiac cycle. These variations can be tracked in a time density curve (TDC) at any point along the vessel. 2) The time it takes the contrast bolus to arrive at a more distal location is quantified by the time-shift between the peak of the curves (Δt). 3) Velocity is calculated by knowing the distance and time between 2 points in the vasculature. 4) The area of the vessel is calculated from the 4D-DSA geometry. 5) The flow is quantified using the velocity and area.