Abstract No. 377 A quantitative angiography technique using time-resolved two-dimensional digital subtraction angiography for determining treatment endpoints during partial splenic embolization

Abstract

There is a relationship between extent of embolization and severity of post procedure complications for partial splenic embolization (PSE), but determining appropriate treatment endpoints is difficult due to the use of subjective angiographic assessments. The objective of this study was to determine the feasibility of using time-resolved two-dimensional digital subtraction angiography (2D-DSA, qDSA) for quantifying changes in splenic arterial and venous flow rates during PSE as a flow-based endpoint rather than a volume based one. Two female domestic swine underwent splenic artery embolizations using 100- to 300-um embolic particles reconstituted in 20 mL of iohexol 300 contrast and delivered in 1-mL aliquots. In the first embolization, blood velocity changes were assessed using DSA (2 mL/s injections) and indwelling intravascular Doppler wires (in the splenic artery and vein) after each incremental delivery of particles. In the 2nd embolization, DSAs and 4D Flow MRIs were acquired before and after embolization to analyze blood velocity changes. A post-hoc analysis of the DSA sequences used a shifted least-squares approach for calculating blood velocities1. Exceptionally high velocities were excluded from analysis due to sampling insufficiency. During incremental embolization, qDSA calculations showed a linear decrease in splenic arterial blood velocity. There was a 7.4% calculated reduction (from baseline) in velocity per 1 mL of particles delivered (R2 = 0.90). Indwelling Doppler wires in the splenic artery and vein showed correlative changes of 11.0% (R2 = 0.98) and 9.7% (R2 = 0.94) reductions in velocities per 1 mL of particles delivered respectively. In multimodal comparison, a 40.3% reduction in splenic arterial velocity was calculated via qDSA corresponding to a 64.1% reduction in velocity on MRI, and a 23.2% reduction in portal vein cross-sectional area. The calculated splenic arterial velocity decreased progressively during PSE as the degree of embolization increased. The qDSA calculations correlated with changes in splenic and portal hemodynamics measured via intravascular Doppler and MRI. With further development, qDSA may be useful for intraprocedural quantification of the degree of embolization in PSE.