By employing a new interleaved angiography technique, researchers have used quantitative digital subtraction angiography (qDSA) to simultaneously measure intraprocedural blood velocity and vessel morphology. According to authors of “Interleaved Angiography for Simultaneous Acquisition of Vessel Morphology and Blood Velocity Quantification,” radiation dosage rates for qDSA are similar to those of conventional DSA—a finding that could lead to clinical translation of the technique and standardization of treatment endpoints in procedures aimed at altering arterial blood flow. The Featured Abstract will be presented during Sunday’s Scientific Session 5, Imaging in IR, Room 224AB in the Phoenix Convention Center.
“Physicians often have to rely on subjective angiographic evaluation to determine the degree of flow alteration achieved in these procedures, making interpretations subject to inconsistencies,” said presenter Joseph Whitehead, MS, a graduate research assistant at the Wisconsin Institutes for Medical Research. “We set out to develop a method to provide intraprocedural quantitative feedback of the degree of flow alteration. Thanks to the members of the UW-Madison image-guided interventions lab, which is co-directed by Drs. Michael Speidel and Paul Laeseke, qDSA is now a potential solution.”
Interleaved acquisition captures both lower- and higher-dose images in a single image sequence, allowing for simultaneous visualization of vessel morphology and quantification of blood velocity. Tested at 27 frames per second (fps), every 10th image was taken at a high dose, and the rest were taken at a low dose.
The study then consisted of two parts: First, investigators assessed the accuracy of qDSA velocity in a vessel phantom compared to gold standard measurements from an ultrasound flow probe. Second, to evaluate angiographic quality, the researchers measured contrast-to-noise ratios of the gastroduodenal artery in porcine hepatic angiograms by using interleaved imaging and conventional 3 fps DSA.
For each interleaving protocol, blood velocity measurements were found to be highly accurate when compared to measurements from the ultrasound flow probe.
To employ the interleaved technique, the researchers used software capable of frame-by-frame modification of radiation dose. Because only this additional software is required, the researchers hope this will help with qDSA’s clinical translatability.
“After conceiving the idea of interleaved imaging, it was still unclear whether the current X-ray system could change the radiation dose at such a fast frequency,” he said. “After our initial tests, and a lot of refinement, we found that the clinical C-arm system in our lab was capable of interleaved imaging via additional software, not requiring any additional hardware modification. Since it only requires additional software, we think broad adoption of this interleaved technique will be simpler and aid in the clinical translatability of qDSA.”
The researchers were inspired to further prior work on qDSA conducted at the University of Wisconsin-Madison, with the end goal of clinical translation.
“Prior to me joining the image-guided interventional lab at UW-Madison, many others had worked on qDSA, and it would not be where it is today without them,” said Mr. Whitehead. “Still, hurdles remain to clinical translation. One of these hurdles is the associated high radiation dose required. Since I believe that qDSA could be an impactful technique, I chose to focus on solving this issue as part of my thesis work.”
While working to improve the high radiation dose required for qDSA, the researchers aimed for a solution that would involve minimal workflow disruptions.
“Being a part of an interventional lab, where the focus is on minimally invasive procedures, we wanted to develop an elegant solution that would be minimally disruptive to the existing clinical workflow,” said Mr. Whitehead. “This is where interleaved imaging was born, since it enables simultaneous acquisition of intraprocedural blood velocity and vessel morphology at dose rates comparable to conventional DSA imaging.”
These results are preliminary, Mr. Whitehead said, and more work must be done before the technique can be evaluated in human trials.
“While we have shown preliminary results of the interleaved imaging prototype, a lot of work remains,” he said. “We still need to ensure the interleaving can be performed at various dose levels and imaging frequencies. Furthermore, the efficacy of qDSA needs to be demonstrated in human trials; however, the development of this technique pushes us closer to being able to do these trials.”