Evaluation of a novel 2D perfusion angiography technique independent of pump injections for assessment of interventional treatment of peripheral vascular disease

Quantification of Iliac Arterial Blood Velocity in Stenotic Phantom and Porcine Models Using Quantitative Digital Subtraction Angiography

PURPOSE

To assess the feasibility of using quantitative digital subtraction angiography (qDSA) to quantify arterial velocity in phantom and porcine stenotic iliac artery models.

MATERIALS AND METHODS

Varying degrees of stenoses (mild, <50%; moderate, 50%-70%; and severe, >70%) were created in a silicone iliac artery phantom using vessel loops. Two-dimensional digital subtraction angiography (DSA) was performed, with velocities calculated using qDSA. qDSA velocities were compared with flow rates and velocities measured with an ultrasonic flow probe. Two-dimensional DSAs of the common and external iliac arteries were then performed in 4 swine (mean weight, 63 kg) before and after a severe stenosis (>70%) was created in the iliac artery using 3-0 silk suture. Peak systolic velocities on pulsed wave Doppler ultrasound (US) before and after stenosis creation were correlated with the qDSA velocities. Pearson correlation, linear regression, and analysis of variance were used for analysis.

RESULTS

In the phantom study, ultrasonic probe velocities positively correlated with downstream qDSA (r = 0.65; P < .001) and negatively correlated with peristenotic qDSA velocities (r = -0.80; P < .001). In the swine study, statistically significant reductions in external iliac arterial velocity were noted on US and qDSA after stenosis creation (P < .05). US and qDSA velocities strongly correlated for all flow states with both 50% and 100% contrast concentrations (r = 0.82 and r = 0.74, respectively), with an estimated US-to-qDSA ratio of 1.3-1.5 (P < .001). qDSA velocities with 50% and 100% contrast agent concentrations also strongly correlated (r = 0.78; P < .001).

CONCLUSIONS

In both phantom and swine stenosis models, changes in iliac arterial velocity could be quantified with qDSA, which strongly correlated with standard-of-care US.

Association of 2D Perfusion Angiography and Wound Healing Rate in Combined Femoro-popliteal and Below-the-Knee Lesions in Ischemic Patients Undergoing Isolated Femoro-popliteal Endovascular Revascularization

The aim of this study was to demonstrate the association between 2-dimensional (2D) perfusion angiography and wound healing rate in patients with combined femoro-popliteal and below-the-knee lesions in critical limb-threatening ischemia (CLTI) and foot wounds undergoing isolated femoro-popliteal endovascular revascularization. Between January and June 2019, 24 patients with multilevel CLTI and foot wounds underwent isolated femoro-popliteal endovascular revascularization. In all of them, an assessment of foot perfusion by 2D perfusion angiography was performed. To evaluate the foot perfusion, a region of interest was identified, and time-density curves were calculated. Changes of the overall time-density curves were evaluated together with transcutaneous oximetry (TcPO2) using bivariate correlation (Pearson correlation coefficient) and associated with 6-month wound healing. The mean increase of time-density curves was 212.2% (range from +9.8% to +1984.9%) and the mean increase of TcPO2 was 116.4% (range from -4.7% to 485.7%). No significant association between time-density curves and TcPO2 values (Pearson correlation coefficient: -0.24) was observed (P = .3). At 6 months, wound healing occurred in 15 of 24 (62.5%) patients. In conclusion, this preliminary experience confirmed that 2D perfusion angiography associates with wound healing rate in CLTI patients with ischemic foot wounds and combined femoro-popliteal and below-the-knee lesions who are undergoing isolated femoro-popliteal endovascular revascularization. No association between time-density curves and TcPO2 values was observed.

Clinical Applications of Quantitative Perfusion Imaging with a C-Arm Flat-Panel Detector-A Systematic Review

C-arm systems with digital flat-panel detectors are used in interventional radiology and hybrid operating rooms for visualizing and performing interventions on three-dimensional structures. Advances in C-arm technology have enabled intraoperative quantitative perfusion imaging with these scanners. This systematic review provides an overview of flat-panel detector C-arm techniques for quantifying perfusion, their clinical applications, and their validation. A systematic search was performed for articles published between January 2000 and October 2022 in which a flat-panel detector C-arm technique for quantifying perfusion was compared with a reference technique. Nine articles were retrieved describing two techniques: two-dimensional perfusion angiography (n = 5) and dual-phase cone beam computed tomography perfusion (n = 4). A quality assessment revealed no concerns about the applicability of the studies. The risk of bias was relatively high for the index and reference tests. Both techniques demonstrated potential for clinical application; however, weak-to-moderate correlations were reported between them and the reference techniques. In conclusion, both techniques could add new possibilities to treatment planning and follow-up; however, the available literature is relatively scarce and heterogeneous. Larger-scale randomized prospective studies focusing on clinical outcomes and standardization are required for the full understanding and clinical implementation of these techniques.

Changes in perfusion angiography after IVC filter placement and retrieval

Inferior vena cava (IVC) filters are posited to effect flow dynamics, causing turbulence, vascular remodeling and eventual thrombosis; however, minimal data exists evaluating hemodynamic effects of IVC filters in vivo. The purpose of this study was to determine differences in hemodynamic flow parameters acquired with two-dimension (2D)-perfusion angiography before and after IVC filter placement or retrieval. 2D-perfusion images were reconstructed retrospectively from digital subtraction angiography from a cohort of 37 patients (13F/24M) before and after filter placement (n = 18) or retrieval (n = 23). Average dwell time was 239.5 ± 132.1 days. Changes in the density per pixel per second within a region of interest (ROI) were used to calculate contrast arrival time (AT), time-to-peak (TTP), wash-in-rate (WIR), and mean transit time (MTT). Measurements were obtained superior to, inferior to, and within the filter. Differences in hemodynamic parameters before and after intervention were compared, as well as correlation between parameters versus filter dwell time. A P value with Bonferroni correction of <.004 was considered statistically significant. After placement, there was no difference in any 2D-perfusion variable. After retrieval, ROIs within and inferior to the filter showed a significantly shorter TTP (1.7 vs 1.4 s, P = .004; 1.5 vs 1.3 s, P = .001, respectively) and MTT (1.7 vs 1.4 s, P = .003; 1.5 vs 1.2 s, P = .002, respectively). Difference in variables showed no significant correlation when compared to dwell time. 2D-perfusion angiography is feasible to evaluate hemodynamic effects of IVC filters in vivo. TTP and MTT within and below the filter after retrieval were significantly changed, without apparent correlation to dwell time, suggesting a functional hemodynamic delay secondary to filter presence.

Angiosome-directed endovascular intervention and infrapopliteal disease: Intraoperative evaluation of distal hemodynamic changes and foot blood volume of lower extremity

Objectives

To evaluate foot blood volume and hemodynamics and explore whether quantitative techniques can guide revascularization.

Materials and methods

A prospective single-center cohort study included thirty-three patients with infrapopliteal artery occlusion who underwent percutaneous transluminal angioplasty (PTA) between November 2016 and May 2020. The time-to-peak (TTP) from color-coded quantitative digital subtraction angiography (CCQ-DSA) and parenchymal blood volume (PBV) were used to evaluate the blood volume and hemodynamic changes in different regions of the foot before and after the operation.

Results

After the intervention procedure, the overall blood volume significantly increased from 25.15 ± 21.1 ml/1,000 ml to 72.33 ± 29.3 ml/1,000 ml (p &lt; 0.001, with an average increase of 47.18 ml/1,000 ml. The overall TTP decrease rate, postoperative blood flow time significantly faster than those preoperatively, from 22.93 ± 7.83 to 14.85 ± 5.9 s (p &lt; 0.001, with an average decrease of 8.08 s). Direct revascularization (DR) resulted in significant blood volume improvement than compared with indirect revascularization (IR) [188% (28, 320) vs.51% (10, 110), p = 0.029]. Patients with DR had a significantly faster blood flow time than those with IR [80% (12, 180) vs. 26% (5, 80), p = 0.032]. The ankle-brachial index (ABI) of the affected extremity also showed an significant change from 0.49 ± 0.3 to 0.63 ± 0.24 (p &lt; 0.001) after the intervention. The relative values of ΔTTP and ΔABI showed a weak correlation (r = −0.330).

Conclusions

The quantitative measurement results based on PBV and CCQ-DSA techniques showed that the overall blood volume increased significantly and that the foot distal hemodynamics were significantly improved after endovascular treatment. DR in the ischemic area could r improve foot perfusion.

Perfusion imaging techniques in lower extremity peripheral arterial disease

Lower limb peripheral arterial disease (PAD) characterizes the impairment of blood flow to extremities caused by arterial stenoses or occlusions. Evaluation of PAD is based on clinical examination, calculation of ankle-brachial index and imaging studies such as ultrasound, CT, MRI and digital subtraction angiography. These modalities provide significant information about location, extension and severity of macrovasular lesions in lower extremity arterial system. However, they can be also used to evaluate limb perfusion, using appropriate techniques and protocols. This information may be valuable for assessment of the severity of ischemia and detection of hypoperfused areas. Moreover, they can be used for planning of revascularization strategy in patients with severe PAD and evaluation of therapeutic outcome. These techniques may also determine prognosis and amputation risk in patients with PAD. This review gives a basic overview of the perfusion techniques for lower limbs provided by imaging modalities such as ultrasound, CT, MRI, digital subtraction angiography and scintigraphy and their clinical applications for evaluation of PAD and revascularization outcome.

2D-perfusion angiography for intra-procedural endovascular treatment response assessment in chronic mesenteric ischemia: a feasibility study

BACKGROUND

Endovascular revascularization has become the first-line treatment of chronic mesenteric ischemia (CMI). The qualitative visual analysis of digital subtraction angiography (DSA) is dependent on observer experience and prone to interpretation errors. We evaluate the feasibility of 2D-Perfusion Angiography (2D-PA) for objective, quantitative treatment response assessment in CMI.

METHODS

49 revascularizations in 39 patients with imaging based evidence of mesenteric vascular occlusive disease and clinical signs of CMI were included in this retrospective study. To assess perfusion changes by 2D-PA, DSA-series were post-processed using a dedicated, commercially available software. Regions of interest (ROI) were placed in the pre- and post-stenotic artery segment. In aorto-ostial disease, the inflow ROI was positioned at the mesenteric artery orifice. The ratios outflow to inflow ROI for peak density (PD), time to peak and area-under-the-curve (AUC) were computed and compared pre- and post-interventionally. We graded motion artifacts by means of a four-point scale. Feasibility of 2D-PA and changes of flow parameters were evaluated.

RESULTS

Motion artifacts due to a mobile vessel location beneath the diaphragm or within the mesenteric root, branch vessel superimposition and inadequate contrast enhancement at the inflow ROI during manually conducted DSA-series via selective catheters owing to steep vessel angulation, necessitated exclusion of 26 measurements from quantitative flow evaluation. The feasibility rate was 47%. In 23 technically feasible assessments, PDoutflow/PDinflow increased by 65% (p < 0.001) and AUCoutflow/AUCinflow increased by 85% (p < 0.001). The time to peak density values in the outflow ROI accelerated only minimally without reaching statistical significance. Age, BMI, target vessel (celiac trunk, SMA or IMA), stenosis location (ostial or truncal), calcification severity, plaque composition or the presence of a complex stenosis did not reach statistical significance in their distribution among the feasible and non-feasible group (p > 0.05).

CONCLUSIONS

Compared to other vascular territories and indications, the feasibility of 2D-PA in mesenteric revascularization for CMI was limited. Unfavorable anatomic conditions contributed to a high rate of inconclusive 2D-PA results.

A Systematic Review and Critical Appraisal of Peri-Procedural Tissue Perfusion Techniques and their Clinical Value in Patients with Peripheral Arterial Disease

OBJECTIVE

Many techniques have been introduced to enable quantification of tissue perfusion in patients with peripheral arterial disease (PAD). Currently, none of these techniques is widely used to analyse real time tissue perfusion changes during endovascular or surgical revascularisation procedures. The aim of this systematic review was to provide an up to date overview of the peri-procedural applicability of currently available techniques, diagnostic accuracy of assessing tissue perfusion and the relationship with clinical outcomes.

DATA SOURCES

MEDLINE, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials.

REVIEW METHODS

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic review and Meta-Analysis (PRISMA) guidelines. Four electronic databases were searched up to 31 12 2020 for eligible articles: MEDLINE, Embase, CINAHL and the Cochrane Central Register of Controlled Trials. Eligible articles describing a perfusion measurement technique, used in a peri-procedural setting before and within 24 hours after the revascularisation procedure, with the aim of determining the effect of intervention in patients with PAD, were assessed for inclusion. The QUADAS-2 tool was used to assess the risk of bias and applicability of the studies.

RESULTS

An overview of 10 techniques found in 26 eligible articles focused on study protocols, research goals, and clinical outcomes is provided. Non-invasive techniques included laser speckle contrast imaging, micro-lightguide spectrophotometry, magnetic resonance imaging perfusion, near infrared spectroscopy, skin perfusion pressure, and plantar thermography. Invasive techniques included two dimensional perfusion angiography, contrast enhanced ultrasound, computed tomography perfusion imaging, and indocyanine green angiography. The results of the 26 eligible studies, which were mostly of poor quality according to QUADAS-2, were without exception, not sufficient to substantiate implementation in daily clinical practice.

CONCLUSION

This systematic review provides an overview of 10 tissue perfusion assessment techniques for patients with PAD. It seems too early to appoint one of them as a reference standard. The scope of future research in this domain should therefore focus on clinical accuracy, reliability, and validation of the techniques.

Repeatability, and Intra-Observer and Interobserver Agreement of Two Dimensional Perfusion Angiography in Patients with Chronic Limb Threatening Ischaemia

OBJECTIVE

Two dimensional (2D) perfusion angiography is a method that provides quantitative foot perfusion information from standard digital subtraction angiography acquisitions. The aim of this study was to test the reliability of this method in patients with chronic limb threatening ischaemia (CLTI) by investigating repeatability, and intra-observer and interobserver agreement.

METHODS

Twenty patients with CLTI and a below the knee endovascular revascularisation were included in a prospective clinical study. Prior to treatment two perfusion angiography runs were acquired with a five minute interval without performing an intervention. In these recordings, regions of interest were selected and time density curves and perfusion parameters were determined. To investigate intra-observer agreement one observer performed five measurements on the same acquisition for each patient. To investigate interobserver agreement three observers performed measurements on the same acquisition for each patient. Results were presented in Bland-Altman plots and as the intraclass correlation coefficient per parameter.

RESULTS

Two patients were excluded from repeatability analyses because of major motion artefacts. Repeatability analyses of the 18 remaining patients showed excellent correlation for every parameter (> .96). Intra-observer and interobserver agreement for all 20 patients were excellent for all parameters (1.00).

CONCLUSION

Repeatability and intra-observer and interobserver agreement of 2D perfusion angiography in patients with CLTI were found to be excellent. It is therefore a reliable tool when used according to the standardised methods described in this study.

Evaluation of perfusion changes using a 2D Parametric Parenchymal Blood Flow technique with automated vessel suppression following partial spleen embolization in patients with hypersplenism and portal hypertension

To evaluate the feasibility and potential value of 2D Parametric Parenchymal Blood Flow (2D-PPBF) for the assessment of perfusion changes following partial spleen embolization (PSE) in a retrospective observational study design.Overall, 12 PSE procedures in 12 patients were included in this study. The outcome of the study was the platelet response (PR), calculated as the percentage increase of platelet count (PLT), following PSE. To quantify perfusion changes using 2D-PPBF, the acquired digital subtraction angiography series were post-processed. A reference region-of-interest (ROI) was placed in the afferent splenic artery and a target ROI was positioned on the embolization territory of the spleen on digital subtraction angiography series pre- and post-embolization. The ratios of the target ROIs to the reference ROIs were calculated for the Wash-In-Rate (WIR), the Time-To-Peak (TTP) and the Area-Under-the-Curve (AUC). Comparisons between pre- and post-embolization data were made using Wilcoxon signed-rank test and Spearman's rank correlation coefficient (r). Afterwards, the study population was divided by the median of the TTP before PSE to analyze its value for the prediction of PR following PSE.Following PSE, PLT increased significantly from 43,000 ± 21,405 platelets/μL to 128,500 ± 66,083 platelets/μL with a PR of 255 ± 243% (P = .003). In the embolized splenic territory, the pre-/post-embolization 2D-PPBF parameter changed significantly: WIRpre-PSE 1.23 ± 2.42/WIRpost-PSE 0.09 ± 0.07; -64 ± 46% (p = 0.04), TTPpre-PSE 4.41 ± 0.99/TTPpost-PSE 5.67 ± 1.52 (P = .041); +34 ± 47% and AUCpost-PSE 0.81 ± 0.85/AUCpost-PSE 0.14 ± 0.08; -71 ± 18% (P = .002). A significant correlation of a 2D-PPBF parameter with the PLT was found for TTPpre-PSE/PLTpre-PSE r = -0.66 (P = .01). Subgroup analysis showed a significantly increased PR for the group with TTPpre-PSE >4.44 compared to the group with TTPpre-PSE ≤4.44 (404 ± 267% versus 107 ± 76%; P = .04).2D-PPBF is an objective approach to analyze the perfusion reduction of embolized splenic tissue. TTP derived from 2D-PPBF has the potential to predict the extent of PR during PSE.

A technique for intra-procedural blood velocity quantitation using time-resolved 2D digital subtraction angiography

BACKGROUND

2D digital subtraction angiography (DSA) is utilized qualitatively to assess blood velocity changes that occur during arterial interventions. Quantitative angiographic metrics, such as blood velocity, could be used to standardize endpoints during angiographic interventions.

PURPOSE

To assess the accuracy and precision of a quantitative 2D DSA (qDSA) technique and to determine its feasibility for in vivo measurements of blood velocity.

MATERIALS AND METHODS

A quantitative DSA technique was developed to calculate intra-procedural blood velocity. In vitro validation was performed by comparing velocities from the qDSA method and an ultrasonic flow probe in a bifurcation phantom. Parameters of interest included baseline flow rate, contrast injection rate, projection angle, and magnification. In vivo qDSA analysis was completed in five different branches of the abdominal aorta in two 50 kg swine and compared to 4D Flow MRI. Linear regression, Bland-Altman, Pearson's correlation coefficient and chi squared tests were used to assess the accuracy and precision of the technique.

RESULTS

In vitro validation showed strong correlation between qDSA and flow probe velocities over a range of contrast injection and baseline flow rates (slope = 1.012, 95% CI [0.989,1.035], Pearson's r = 0.996, p < .0001). The application of projection angle and magnification corrections decreased variance to less than 5% the average baseline velocity (p = 0.999 and p = 0.956, respectively). In vivo validation showed strong correlation with a small bias between qDSA and 4D Flow MRI velocities for all five abdominopelvic arterial vessels of interest (slope = 1.01, Pearson's r = 0.880, p = <.01, Bias = 0.117 cm/s).

CONCLUSION

The proposed method allows for accurate and precise calculation of blood velocities, in near real-time, from time resolved 2D DSAs.

2D-Perfusion Angiography Using Carbon Dioxide (CO2): A Feasible Tool to Monitor Immediate Treatment Response to Endovascular Therapy of Peripheral Arterial Disease?

PURPOSE

Patients with peripheral arterial disease (PAD) or critical limb ischemia (CLI) require revascularization. Traditionally, endovascular therapy (EVT) is performed with iodinated contrast agent (ICM), which can provoke potential deterioration in renal function. CO2 is a safe negative contrast agent to guide vascular procedures, but interpretation of CO2 angiography is challenging. Changes in blood flow following iodine-aided EVT are assessable with 2D-perfusion angiography (2D-PA). The aim of this study was to evaluate 2D-PA as a tool to monitor blood flow changes during CO₂-aided EVT.

MATERIAL AND METHODS

2D-PA was performed before and after ten EVTs (nine stents; one endoprosthesis; 10/2012-02/2020) in nine patients (six men; 65 ± 10y) with Fontaine stage IIb (n = 8) and IV (n = 1). A reference ROI (ROI_INFLOW) was placed in the artery before the targeted obstruction and a target ROI (ROI_OUTFLOW) distally. Corresponding ROIs were used pre- and post-EVT. Time to peak (TTP), peak density (PD) and area under the curve (AUC) were computed. The reference/target ROI ratios (TTP_OUTFLOW/TTP_INFLOW; PD_OUTFLOW/PD_INFLOW; AUC_OUTFLOW/AUC_INFLOW) were calculated.

RESULTS

2D-PA was technically feasible in all cases. A significant increase of 82% in PD_OUTFLOW/PD_INFLOW (0.44 ± 0.4 to 0.8 ± 0.63; p = 0.002) and of 132% in AUC_OUTFLOW/AUC_INFLOW (0.34 ± 0.22 to 0.79 ± 0.59; p = 0.002) was seen. A trend for a decrease in TTP_OUTFLOW/TTP_INFLOW was observed (- 24%; 5.57 ± 3.66 s-4.25 ± 1.64 s; p = 0.6).

CONCLUSION

The presented 2D-PA technique facilitates the assessment of arterial flow in CO2-aided EVTs and has the potential to simplify the assessment of immediate treatment response.

Two-dimensional parametric parenchymal blood flow in transarterial chemoembolisation for hepatocellular carcinoma: perfusion change quantification and tumour response prediction at 3 months post-intervention

AIM

To evaluate the feasibility and potential value of two-dimensional (2D) parametric parenchymal blood flow (2D-PPBF) for the assessment of perfusion changes during transarterial chemoembolisation with drug-eluting beads (DEB-TACE) and to analyse correlations of 2D-PPBF parameters and tumour response.

MATERIALS AND METHODS

Thirty-two patients (six women, 26 men, mean age: 67±8.9 years) with unresectable hepatocellular carcinoma (HCC) who underwent their first DEB-TACE were included in this study. To quantify perfusion changes using 2D-PPBF, the acquired digital subtraction angiography (DSA) series were post-processed. Ratios were calculated between the reference region of interest (ROI) and the wash-in rate (WIR), the arrival to peak (AP) and the area under the curve (AUC) of the generated time-density curves. Comparisons between pre- and post-embolisation data were made using the Wilcoxon signed-rank test. Tumour response was assessed at 3 months using the modified Response Evaluation Criteria in Solid Tumours (mRECIST) and correlated to changes of 2D-PPBF parameters.

RESULTS

All 2D-PPBF parameters derived from the ROI-based time-attenuation curves were significantly different pre-versus post-DEB-TACE. Although the AUC, the WIR and target lesion size measured in accordance with mRECIST decreased (p≤0.0001) significantly, AP values showed a significant increase (p = 0.0033). Tumour response after DEB-TACE correlated with changes in the AUC (p = 0.01, r = -0.45).

CONCLUSION

2D-PPBF offers an objective approach to analyse perfusion changes of embolised tumour tissue following DEB-TACE and can therefore be used to predict tumour response.

Three-dimensional regions-of-interest-based intra-operative four-dimensional soft tissue perfusion imaging using a standard x-ray system with no gantry rotation: A simulation study for a proof of concept

PURPOSE

Many interventional procedures aim at changing soft tissue perfusion or blood flow. One problem at present is that soft tissue perfusion and its changes cannot be assessed in an interventional suite because cone-beam computed tomography is too slow (it takes 4-10 s per volume scan). In order to address the problem, we propose a novel method called IPEN for Intra-operative four-dimensional soft tissue PErfusion using a standard x-ray system with No gantry rotation.

METHODS

IPEN uses two input datasets: (a) the contours and locations of three-dimensional regions-of-interest (ROIs) such as arteries and sub-sections of cancerous lesions, and (b) a series of x-ray projection data obtained from an intra-arterial contrast injection to contrast enhancement to wash-out. IPEN then estimates a time-enhancement curve (TEC) for each ROI directly from projections without reconstructing cross-sectional images by maximizing the agreement between synthesized and measured projections with a temporal roughness penalty. When path lengths through ROIs are known for each x-ray beam, the ROI-specific enhancement can be accurately estimated from projections. Computer simulations are performed to assess the performance of the IPEN algorithm. Intra-arterial contrast-enhanced liver scans over 25 s were simulated using XCAT phantom version 2.0 with heterogeneous tissue textures and cancerous lesions. The following four sub-studies were performed: (a) The accuracy of the estimated TECs with overlapped lesions was evaluated at various noise (dose) levels with either homogeneous or heterogeneous lesion enhancement patterns; (b) the accuracy of IPEN with inaccurate ROI contours was assessed; (c) we investigated how overlapping ROIs and noise in projections affected the accuracy of the IPEN algorithm; and (d) the accuracy of the perfusion indices was assessed.

RESULTS

The TECs estimated by IPEN were sufficiently accurate at a reference dose level with the root-mean-square deviation (RMSD) of 0.0027 ± 0.0001 cm^-1 or 13 ± 1 Hounsfield unit (mean ± standard deviation) for the homogeneous lesion enhancement and 0.0032 ± 0.0005 cm^-1 for the heterogeneous enhancement (N = 20 each). The accuracy was degraded with decreasing doses: The RMSD with homogeneous enhancement was 0.0220 ± 0.0003 cm^-1 for 20% of the reference dose level. Performing 3 × 3 pixel averaging on projection data improved the RMSDs to 0.0051 ± 0.0002 cm^-1 for 20% dose. When the ROI contours were inaccurate, smaller ROI contours resulted in positive biases in TECs, whereas larger ROI contours produced negative biases. The bias remained small, within ± 0.0070 cm^-1 , when the Sorenson-Dice coefficients (SDCs) were larger than 0.81. The RMSD of the TEC estimation was strongly associated with the condition of the problem, which can be empirically quantified using the condition number of a matrix A z that maps a vector of ROI enhancement values z to projection data and a weighted variance of projection data: a linear correlation coefficient (R) was 0.794 (P < 0.001). The perfusion index values computed from the estimated TECs agreed well with the true values (R ≥ 0.985, P < 0.0001).

CONCLUSION

The IPEN algorithm can estimate ROI-specific TECs with high accuracy especially when 3 × 3 pixel averaging is applied, even when lesion enhancement is heterogeneous, or ROI contours are inaccurate but the SDC is at least 0.81.

Non-occlusive mesenteric ischemia (NOMI): evaluation of 2D-perfusion angiography (2D-PA) for early treatment response assessment

Purpose

To evaluate the feasibility of 2D-perfusion angiography (2D-PA) for the analysis of intra-procedural treatment response after intra-arterial prostaglandin E1 therapy in patients with non-occlusive mesenteric ischemia (NOMI).

Methods

Overall, 20 procedures in 18 NOMI patients were included in this retrospective case–control study. To evaluate intra-procedural splanchnic circulation changes, post-processing of digital subtraction angiography (DSA) series was performed. Regions of interest (ROIs) were placed in the superior mesenteric artery (SMA; reference), the portal vein (PV; ROI_PV), as well as the aorta next to the origin of the SMA (ROI_Aorta). Peak density (PD), time to peak (TTP), and area under the curve (AUC) were assessed, and parametric ratios ‘target ROI_{PD, TTP, AUC}/reference ROI’ were computed and compared within treatment and control group. Additionally, a NOMI score was assessed pre- and post-treatment compared to 2D-PA.

Results

Vasodilator therapy leads to a significant decrease of the 2D-PA-derived values PD_Aorta (p = 0.04) and AUC_Aorta (p = 0.03). These findings correlated with changes of the simplified NOMI score, both for overall (4 to 1, p < 0.0001) and for each category. Prostaglandin application caused a significant increase of the AUC_PV (p = 0.04) and TTP_PV was accelerated without reaching statistical significance (p = 0.13). When compared to a control group, all 2D-PA values in the NOMI group (pre- and post-intervention) differed significantly (p < 0.05) with longer TTP_Aorta/PV and lower AUC_Aorta/PV and PD _Aorta/PV.

Conclusion

2D-PA offers an objective approach to analyze immediate flow and perfusion changes following vasodilatory therapies of NOMI patients and may be a valuable tool for assessing treatment response.

Clinical validation of 2D perfusion angiography using Syngo iFlow software during peripheral arterial interventions

OBJECTIVE

Endovascular surgery is an important treatment modality in peripheral arterial disease. Digital subtraction angiography is the standard post revascularisation diagnostic tool to locate lesions and to evaluate the effect of an intervention. However, interpretation of digital subtraction angiography images is subjective and it is difficult to determine whether revascularisation has been sufficient for clinical improvement. A new technique is 2D perfusion angiography, which creates a 2D colour map and time density curve from the digital subtraction angiography scan for an objective evaluation of the results. However, its clinical relevance is unknown. The aim is to evaluate the association between 2D perfusion angiography parameters and clinical outcome after peripheral arterial interventions.

METHODS

In this retrospective study, post revascularisation angiographic data and clinical data were reviewed of patients who underwent treatment of femoral-popliteal or femoral-tibial arteries. The outcome was assessed at three time points using three classification systems for peripheral arterial disease: Fontaine classification, American Medical Association whole person impairment classification (AMA) and average wound, ischemia, foot infection score. Post revascularisation angiographic data consisted of time density curves of the foot and lower leg which were extracted from the Syngo iFlow system (Siemens Healthineers). For each time density curve, five descriptive parameters were calculated: time of arrival, time to peak, mean transit time, wash-in rate and area under the curve. The association between the time density curve parameters and peripheral arterial disease classification systems was assessed using a regression analysis.

RESULTS

Between July 2016 and December 2018, 103 patients underwent peripheral endovascular interventions in the hybrid operating room; 39 patients were suitable for analysis, of which 28 patients underwent digital subtraction angiography of the lower leg, 3 patients underwent digital subtraction angiography of the foot and 8 patients underwent digital subtraction angiography of both regions. Limited significant relations were found for time of arrival with Fontainde classification (B = 0.806, p = 0.043) and area under the curve with AMA classification (B = -0.027, p = 0.047).

CONCLUSION

In this retrospective study, time density curve parameters (time of arrival and area under the curve), measured in the lower leg, showed a limited significant association with two classification systems for peripheral arterial disease. Future prospective studies to determine the clinical relevance of this 2D perfusion angiography method should focus on standardisation of angiography protocols and comparison of pre- and post-intervention parameters.

New Innovations and Devices in the Management of Chronic Limb-Threatening Ischemia

As the number of patients afflicted by chronic limb-threatening ischemia (CLTI) continues to grow, new solutions are necessary to provide effective, durable treatment options that will lead to improved outcomes. The diagnosis of CLTI remains mostly clinical, and endovascular revascularization remains mostly balloon-based. Multiple innovative techniques and technologies are in development or in early usage that may provide new solutions. This review categorizes areas of advancement, highlights recent developments in the management of CLTI and looks forward to novel devices that are currently under investigation.

Physiologic perfusion monitoring methods during endovascular revascularization for atherosclerotic peripheral arterial disease: protocol for a systematic review

BACKGROUND

Endovascular therapy is a fundamental treatment for peripheral arterial disease. However, the success rate of endovascular therapy remains poor, as a third of patients with critical limb ischemia ultimately require a major amputation for gangrene despite endovascular treatment. This failure rate has prompted investigation into methods of determining physiologic procedural success before and after treatment, before clinically apparent outcomes occur such as gangrene. The aim of this systematic review is to evaluate if in patients undergoing endovascular surgery for lower extremity atherosclerotic peripheral arterial disease, do changes in physiologic measures of perfusion during surgery correlate with clinical outcomes.

METHODS

We registered and designed a study protocol for a systematic review. Literature searches will be conducted in MEDLINE, EMBASE, and CENTRAL (from January 1977 onwards). Grey literature will be identified through OpenGrey and clinical trial registries, and supplemented by citation searches. We will include randomized controlled trials, quasi-experimental trials, and observational (cohort, case-control) studies conducted in human adults (age 18 or older) who received elective arterial angioplasty for atherosclerotic peripheral vascular disease. The primary outcome of interest will be major adverse limb events. Two investigators will independently screen all citation, full-text articles, and abstract data. The study quality (risk of bias) will be appraised appropriate tools. Data analysis and synthesis will be qualitative; no meta-analysis is planned, as the anticipated homogeneity of measurement and outcome reporting standardization is low.

DISCUSSION

The treatment of peripheral arterial disease is unique in that the tissue of the ischemic leg is easily accessible for direct monitoring during procedures. This is contrasted with cardiac and neurologic monitoring during cardiac and cerebral procedures, where indirect or invasive measures are required to monitor organ perfusion. Currently synthesized evidence describing limb perfusion focuses on static states of ischemia, and does not evaluate the value of change in perfusion measurement as an indicator of endovascular treatment success. These methods could potentially be applied to optimize procedural outcomes by guiding perfusion-based decision-making during surgery.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019138192.

Assessment of foot perfusion: Overview of modalities, review of evidence, and identification of evidence gaps

Patients with critical limb ischemia have nonhealing wounds and/or ischemic rest pain and are at high risk for amputation and mortality. Accurate evaluation of foot perfusion should help avoid unnecessary amputation, guide revascularization strategies, and offer efficient surveillance for patency. Our aim is to review current modalities of assessing foot perfusion in the context of the practical clinical management of patients with critical limb ischemia.

2D perfusion-angiography during endovascular intervention for critical limb threatening ischemia - A feasibility study

Purpose

Two-dimensional perfusion angiography is a new method to quantify and evaluate tissue perfusion during endovascular intervention. The aim was to evaluate time-patterns and dynamics of contrast arrival and distribution before and after endovascular intervention in patients with critical limb threatening ischemia.

Methods

Data were collected from 37 patients with critical limb threatening ischemia due to infra-inguinal occlusive disease having a successful endovascular procedure. two-dimensional perfusion angiography was used as a post-processing software with analysis of numeric parameters related to arrival and distribution patterns of contrast.

Results

Thirty-three patients were successfully analysed whereas four patients were excluded due to motion artefacts. All patients were successfully treated with recanalization of the superficial femoral, popliteal, below the knee-vessels or a combination. Short-term improvement at 30-day follow-up was noted both clinically and by ankle-brachial index and toe pressure measurements. A significant reduction in contrast arrival time between pre-and post-angioplasty runs was noted as measured by arrival time median 3.2 and interquartile range (2.5–4.2) vs. 2.6 (1.6–3.4) and time-to-peak 4.1 (3.6–5.0) vs. 3.1 (2.3–3.9) p = 0.009. An increased wash-in rate was also observed 18.3 (12.6–21) vs. 30.1 (22–30.5) p = 0.001 between pre-and post-angioplasty runs.

Conclusions

The use of perfusion angiography for evaluation of foot-circulation during endovascular interventions provides new information regarding quantitative assessment of contrast inflow before and after endovascular intervention without the need for extra contrast or runs. No selective catheterisation is necessary. The technique is easily adopted in a clinical setting. Further studies are necessary to create robust clinical endpoints.

Below-the-Ankle Arrival Time as a Novel Limb Tissue Perfusion Index: Two-dimensional Perfusion Angiography Evaluation

Purpose: To identify lower limb 2-dimensional (2D) perfusion angiographic parameters that are related to skin perfusion pressure (SPP), a predictor of wound healing in patients with chronic limb-threatening ischemia (CLTI) undergoing below-the-knee (BTK) endovascular treatment (EVT). Materials and Methods: Thirty-three consecutive patients (mean age 74.5 years; 18 men) with 47 isolated BTK lesions in 33 limbs (Rutherford category 3–5) underwent EVT. Dorsal and plantar SPPs were measured before EVT and the day after. The indexed blood flow below the ankle was measured using 2D perfusion angiography before and after EVT to determine changes in perfusion parameters [arrival time (AT), time to peak, wash-in rate, mean transit time, and width and area under the time-density curve] at rest vs during hyperemia induced with a 20-mg intra-arterial papaverine infusion. Correlations between the 2D perfusion parameters and SPPs were assessed using the Pearson coefficient. The cutoff points to predict mean SPPs >40 mm Hg were analyzed using a receiver operating characteristic curve; outcomes are reported as the area under the curve (AUC) with 95% confidence interval (CI). Results: After EVT at rest and during hyperemia, only AT was significantly changed, although hyperemia produced significant changes in all the pre-/post-EVT 2D perfusion parameters except the wash-in rate. Dorsal and plantar SPPs after EVT were significantly increased and correlated with hyperemic AT and the AT ratio (hyperemia/at rest values) below the ankle. Hyperemic ATs <6.3 seconds and AT ratios <0.78 were predictive factors for a mean SPP >40 mm Hg, with AUCs of 0.83 (95% CI 0.67 to 0.99) and 0.78 (95% CI 0.61 to 0.95), respectively. Conclusion: Hyperemic ATs <6.3 seconds or AT ratios <0.78 below the ankle may be essential to obtain sufficient SPPs for limb salvage in BTK lesions. Thus, the use of 2D perfusion angiography enabled the monitoring of lower limb tissue perfusion throughout EVT and may thereby optimize treatment of CLTI.

Quantitative evaluation of postintervention foot blood supply in patients with peripheral artery disease by computed tomography perfusion

OBJECTIVE

The aim of this study was to quantitatively evaluate the changes of the foot's blood supply after endovascular treatment in patients with peripheral artery disease (PAD) using foot computed tomography (CT) perfusion.

METHODS

Nineteen patients who underwent endovascular treatment for PAD between January 2018 and November 2018 were included in the study. Perfusion CT scanning was performed before and after intervention with the measurement of ankle-brachial index. Regions of interest were selected from two arteries and four different tissues per foot. Perfusion maps of blood volume, blood flow, permeability surface area product, time to peak (TTP), mean transit time (MTT), mean slope of increase (MSI), Tmax, and impulse response function (IRFt₀) were constructed and calculated by the perfusion analysis software. Wilcoxon signed rank test was performed on the eight parameter pairs of the limbs on the treated and untreated sides before and after intervention in the 19 patients.

RESULTS

Differences in blood flow, MTT, TTP, Tmax, MSI, and IRFt₀ on the treated side of the tissue perfusion group and statistical difference in blood flow, MTT, and MSI on the treated side of the arterial perfusion group were observed (all P < .05). Ankle-brachial index improved from 0.41 ± 0.11 to 0.76 ± 0.10 (P < .001). For the untreated side, TTP of the tissue perfusion group was significantly shortened (by 7.71 seconds) after surgery (P = .006), whereas there were no differences in the other parameters. In addition, no significant differences in parameters were observed on the untreated side of the arterial perfusion group. The average radiation dose per phase of perfusion scan was 0.00097 mSv. Moreover, the hyperperfusion zone in the plantar dermis and periosteum reappeared after revascularization.

CONCLUSIONS

Perfusion CT is a feasible and repeatable approach for quantifying blood supply in patients with PAD. The increase of blood flow, MSI, and MTT shortening suggest blood supply improvement after revascularization in both arterial perfusion and tissue perfusion. In addition, TTP may be a sensitive indicator of blood supply changes in tissue perfusion.

Protocol for a prospective observational diagnostic study: intraoperative simultaneous limb pressure monitoring (INSTANT) study

INTRODUCTION

Peripheral vascular disease (PVD) is a condition caused by arterial blockages causing inadequate blood flow, resulting in pain and gangrene of the legs. Endovascular therapy, such as angioplasty, can be used to treat PVD, however, the operator feedback during surgery is primarily anatomic based on the angiogram. Because physiologic blood perfusion can be difficult to determine based on anatomic images, we propose introducing physiological measurements into the operating room. This study will investigate whether the change in intraoperative monitoring of haemodynamic measurements such as the Toe-Brachial Index during endovascular surgery for lower extremity atherosclerotic PVD is associated with clinical outcomes such as major adverse limb events (MALEs).

METHODS AND ANALYSIS

This study will be a prospective, operator-blinded and blinded endpoint adjudicated observational diagnostic cohort study. A total of 80 legs will be enrolled in the study. Ankle and toe blood pressures will be measured non-invasively at predetermined time points before, during and after surgery, and we will assess associations between changes in intraoperative pressure measurements and postoperative clinical and haemodynamic outcomes. The primary outcome will be MALE within 1 year, and secondary outcomes include follow-up pressure measurements, vessel patency, reintervention, clinical staging improvement, amputation and death.

ETHICS AND DISSEMINATION

Regional hospital ethics approval has been granted (Ottawa Hospital Research Institute - Research Ethics Board, Protocol 20180656-01H). On completion of data analysis, the study will submitted for presentation at international vascular surgical society meetings, in addition to submission for publication in publicly accessible medical journals.

TRIAL REGISTRATION NUMBER

NCT03875846.

Evaluation of a newly developed 2D parametric parenchymal blood flow technique with an automated vessel suppression algorithm in patients with chronic thromboembolic pulmonary hypertension undergoing balloon pulmonary angioplasty

AIM

To evaluate the feasibility of two-dimensional parametric parenchymal blood flow (2D-PPBF) to quantify perfusion changes in the lung parenchyma following balloon pulmonary angioplasty (BPA) for treatment of chronic thromboembolic pulmonary hypertension.

MATERIALS AND METHODS

Overall, 35 consecutive interventions in 18 patients with 98 treated pulmonary arteries were included. To quantify changes in pulmonary blood flow using 2D-PPBF, the acquired digital subtraction angiography (DSA) series were post-processed using dedicated software. A reference region of interest (ROI; arterial inflow) in the treated pulmonary artery and a distal target ROI, including the whole lung parenchyma distal to the targeted stenosis, were placed in corresponding areas on DSA pre- and post-BPA. Half-peak density (HPD), wash-in rate (WIR), arrival to peak (AP), area under the curve (AUC), and mean transit time (MTT) were assessed. The ratios of the reference ROI to the target ROI (HPD_parenchyma/HPD_inflow, WIR_parenchyma/WIR_inflow; AP_parenchyma/AP_inflow, AUC_parenchyma/AUC_inflow, MTT_parenchyma/MTT_inflow) were calculated. The relative differences of the 2D-PPBF parameters were correlated to changes in the pulmonary flow grade score.

RESULTS

The pulmonary flow grade score improved significantly after BPA (1 versus 3; p<0.0001). Likewise, the mean HPD_parenchyma/HPD_inflow (-10.2%; p<0.0001), AP_parenchyma/AP_inflow (-24.4%; p=0.0007), and MTT_parenchyma/MTT_inflow (-3.5%; p=0.0449) decreased significantly, whereas WIR_parenchyma/WIR_inflow (+82.4%) and AUC_parenchyma/AUC_inflow (+58.6%) showed a significant increase (p<0.0001). Furthermore, a significant correlation between changes of the pulmonary flow grade score and changes of HPD_parenchyma/HPD_inflow (ρ=-0.21, p=0.04), WIR_parenchyma/WIR_inflow (ρ=0.43, p<0.0001), AP_parenchyma/AP_inflow (ρ=-0.22, p=0.03), AUC_parenchyma/AUC_inflow (ρ=0.48, p<0.0001), and MTT_parenchyma/MTT_inflow (ρ=-0.39, p<0.0001) could be observed.

CONCLUSION

The 2D-PPBF technique is feasible for the quantification of perfusion changes following BPA and has the potential to improve monitoring of BPA.

Transjugular intrahepatic portosystemic shunt (TIPS) dysfunction: quantitative assessment of flow and perfusion changes using 2D-perfusion angiography following shunt revision

PURPOSE

To analyze the feasibility of 2D-perfusion angiography (2D-PA) to quantify flow and perfusion changes pre- and post-transjugular intrahepatic portosystemic shunt (TIPS) revision.

MATERIALS AND METHODS

Fifteen consecutive patients (54 ± 14 years, seven men and eight women) scheduled for TIPS revision were included in this study. To quantify flow and perfusion changes caused by TIPS revision, digital subtraction angiography (DSA) series acquired during the revision were post-processed using a dedicated software. Reference region-of-interest (ROI) in the main portal vein (input function) and target ROIs in the TIPS lumen, the liver parenchyma and in the right atrium were placed in corresponding areas on DSA pre- and post-TIPS revision. 2D-PA evaluation included time to peak (TTP), peak density (PD), and the area under the curve (AUC) assessment. The ratios of reference ROI to target ROIs pre- and post-TIPS revision were calculated (TTP_parenchyma/TTP_inflow, PD_parenchyma/PD_inflow, AUC_parenchyma/AUC_inflow, TTP_TIPS/TTP_inflow, PD_TIPS/PD_inflow, AUC_TIPS/AUC_inflow, TTP_atrium/TTP_inflow, PD_atrium/PD_inflow, and AUC_atrium/AUC_inflow). Pressure measurements pre- and post-TIPS revision were performed and correlated to the 2D-PA parameters. Reproducibility of 2D-PA was assessed by the intra-class correlation coefficient (ICC).

RESULTS

The portosystemic pressure gradient was significantly reduced following TIPS revision (17.1 ± 6.3 vs. 8.9 ± 4.3 mmHg; p < 0.0001). PD_TIPS/PD_inflow (0.22 vs. 0.35; p = 0.0014) and AUC_TIPS/AUC_inflow (0.24 vs. 0.39; p = 0.0012) increased significantly. Likewise, PD_atrium/PD_inflow (0.32 vs. 0.78; p = 0.0004) and AUC_atrium/AUC_inflow (0.3 vs. 0.79; p < 0.0001) increased, whereas PD_parenchyma/PD_inflow decreased significantly (0.14 vs. 0.1; p = 0.0084). Pressure gradient changes correlated significantly with the increase in PD_atrium/PD_inflow (r = - 0.77, p = 0.0012) and AUC_atrium/AUC_inflow (r = - 0.76, p = 0.0018). ICC of the 2D-PA parameters was in the range of 0.88-0.99.

CONCLUSION

2D-PA offers a feasible approach to quantify flow and perfusion changes during TIPS revision. Therefore, 2D-PA may be a valuable amendment to mere pressure measurements.

Efficacy of Two-Dimensional Perfusion Angiography for Evaluations after Infrapopliteal Bypass Surgery for Critical Limb Ischemia

Two-dimensional perfusion angiography (2DPA) is utilized in hybrid operating rooms. 2DPA produces color map images and functional parameters to provide more robust visual and quantitative evaluations than conventional angiography. Its efficacy was suggested in five patients following bypass surgery; unexpected results were obtained in one patient, leading to a decision to perform surgical re-anastomosis. Furthermore, we found that the general anesthesia eliminates body movements that tend to disrupt 2DPA results. 2DPA was more useful during surgical revascularization than conventional angiography and provided more detailed information.

Quantification of perfusion reduction by using 2D-perfusion angiography following transarterial chemoembolization with drug-eluting beads

PURPOSE

To analyze the feasibility of 2D-perfusion angiography (2D-PA) for the quantification of perfusion reduction following transarterial chemoembolization with drug-eluting beads (DEB-TACE).

METHODS

Overall, 24 DEB-TACE procedures in 19 patients were included. To quantify changes in tumor perfusion following DEB-TACE using 2D-PA, the acquired digital subtraction angiography (DSA) series were post-processed. A reference region-of-interest (ROI) in a main hepatic artery and two, distal target ROIs in embolized tumor tissue and in non-target liver parenchyma were placed in corresponding areas on DSA pre- and post-DEB-TACE. The time to peak (TTP), peak density (PD), and the area under the curve (AUC) were assessed and the ratios reference ROI/target ROIs were calculated.

RESULTS

In the embolized tumor, the 2D-PA ratios changed significantly (p < 0.05) after DEB-TACE, whereas no significant change was observed for non-target liver parenchyma (p > 0.05). PD_tumor/PD_inflow differed significantly to PD_parenchyma/PD_inflow pre-DEB-TACE (p < 0.0001), likewise AUC_tumor/AUC_inflow to AUC_parenchyma/AUC_inflow (p < 0.0001) with higher values in tumor tissue. The post-DEB-TACE ratios of AUC decreased significantly in the tumor tissue compared to the non-target liver parenchyma (p < 0.05).

CONCLUSION

2D-PA offers an objective approach to quantify the immediate perfusion reduction of embolized tumor tissue following DEB-TACE and may therefore be used to monitor peri-interventional stasis and to quantify technical success.

Chronic thromboembolic pulmonary hypertension: Evaluation of 2D-perfusion angiography in patients who undergo balloon pulmonary angioplasty

OBJECTIVE

To evaluate the feasibility of 2D-perfusion angiography (2D-PA) in order to quantify perfusion changes of the lung parenchyma pre- and post-balloon pulmonary angioplasty (BPA).

METHODS

Thirty consecutive interventions in 16 patients with 99 treated pulmonary artery segments were included. To quantify changes in pulmonary blood flow using 2D-PA, the acquired digital subtraction angiographies (DSA) pre- and post-BPA were post-processed. A reference ROI in the treated pulmonary artery and a distal target ROI in the lung parenchyma were placed in corresponding areas on DSA pre- and post-BPA. Time to peak (TTP), peak density (PD) and area under the curve (AUC) were assessed. The ratios reference ROI to target ROI (TTP_parenchyma/TTP_inflow; PD_parenchyma/PD_inflow; AUC_parenchyma/AUC_inflow) were calculated. Relative differences of the 2D-PA parameters were correlated to changes in the pulmonary-flow-grade-score.

RESULTS

The pulmonary-flow-grade-score improved after BPA (p<0.0001). Likewise, the ratio TTP_parenchyma/TTP_inflow shortened by 10% (p=0.0002), the PD_parenchyma/PD_inflow increased by 46% (p<0.0001) and the AUC_parenchyma/AUC_inflow increased by 36% (p<0.0001). A significant correlation between changes in the pulmonary-flow-grade-score and changes in PD_parenchyma/PD_inflow (ρ=0.48, p<0.0001) and AUC_parenchyma/AUC_inflow (ρ=0.31, p=0.0018) was observed.

CONCLUSION

Quantification of pulmonary perfusion pre- and post-BPA using 2D-PA is feasible and has the potential to improve monitoring of BPA.

KEY POINTS

• Quantification of BPA results by use of 2D-PA is feasible. • 2D-PA allows objective assessment of changes in lung parenchymal perfusion. • 2D-PA has the potential to optimize BPA.