Full-Volume Assessment of Abdominal Aortic Aneurysm by Improved-Field-of-View 3-D Ultrasound Performs Comparably to Computed Tomographic Angiography

A comparison of ultrasound volume navigation, O-arm navigation, and X-ray guidance for screw placement in minimally invasive transforaminal lumbar interbody fusion: a randomized controlled trial

OBJECTIVE

To compare the differences between Ultrasound Volume Navigation (UVN), O-arm Navigation, and conventional X-ray fluoroscopy-guided screw placement in Minimally Invasive Transforaminal Lumbar Interbody Fusion (MIS-TLIF) surgeries.

METHODS

A total of 90 patients who underwent MIS-TLIF due to lumbar disc herniation from January 2022 to January 2023 were randomly assigned to the UVN group, O-arm group, and X-ray group. UVN, O-arm navigation, and X-ray guidance were used for screw placement in the respective groups, while the remaining surgical procedures followed routine MIS-TLIF protocols. Intraoperative data including average single screw placement time, total radiation dose, and average effective radiation dose per screw were recorded and calculated. On the 10th day after surgery, postoperative X-ray and CT examinations were conducted to assess screw placement accuracy and facet joint violation.

RESULTS

There were no significant differences in general characteristics among the three groups, ensuring comparability. Firstly, the average single screw placement time in the O-arm group was significantly shorter than that in the UVN group and X-ray group (P<0.05). Secondly, in terms of total radiation dose during surgery, for single-level MIS-TLIF, the O-arm group had a significantly higher radiation dose compared to the UVN group and X-ray group (P<0.05). However, for multi-level MIS-TLIF, the X-ray group had a significantly higher radiation dose than the O-arm group and UVN group (P<0.05). In terms of average single screw radiation dose, the O-arm group and X-ray group were similar (P>0.05), while the UVN group was significantly lower than the other two groups (P<0.05). Furthermore, no significant differences were found in screw placement assessment grades among the three groups (P>0.05). However, in terms of facet joint violation rate, the UVN group (10.3%) and O-arm group (10.7%) showed no significant difference (P>0.05), while the X-ray group (26.7%) was significantly higher than both groups (P<0.05). Moreover, in the UVN group, there were significant correlations between average single screw placement time and placement grade with BMI index (r = 0.637, P<0.05; r = 0.504, P<0.05), while no similar significant correlations were found in the O-arm and X-ray groups.

CONCLUSION

UVN-guided screw placement in MIS-TLIF surgeries demonstrates comparable efficiency, visualization, and accuracy to O-arm navigation, while significantly reducing radiation exposure compared to both O-arm navigation and X-ray guidance. However, UVN may be influenced by factors like obesity, limiting its application.

One-year follow-up after active aortic aneurysm sac treatment with shape memory polymer devices during endovascular aneurysm repair

OBJECTIVE

To determine the safety and efficacy of treating abdominal aortic aneurysm (AAA) sacs with polyurethane shape memory polymer (SMP) devices during endovascular aneurysm repair (EVAR), using a technique to fully treat the target lumen after endograft placement (aortic flow volume minus the endograft volume). SMP devices self-expand in the sac to form a porous scaffold that supports thrombosis throughout its structure.

METHODS

Two identical prospective, multicenter, single-arm studies were conducted in New Zealand and the Netherlands. The study population was adult candidates for elective EVAR of an infrarenal AAA (diameter of ≥55 mm in men and ≥50 mm in women). Key exclusion criteria were an inability to adequately seal a common iliac artery aneurysm, patent sac feeding vessels of >4 mm, and a target lumen volume of <20 mL or >135 mL. Target lumen volumes were estimated by subtracting endograft volumes from preprocedural imaging-based flow lumen volumes. SMP devices were delivered immediately after endograft deployment via a 6F sheath jailed in a bowed position in the sac. The primary efficacy end point was technical success, defined as filling the actual target lumen volume with fully expanded SMP at the completion of the procedure. Secondary efficacy outcome measures during follow-up were the change in sac volume and diameter, rate of type II endoleak and type I or III endoleaks, and the rate of open repair and related reinterventions, with data collection at 30 days, 6 months, and 1 year (to date). Baseline sac volumes and diameters for change in sac size analyses were determined from 30-day imaging studies. Baseline and follow-up volumes were normalized by subtraction of the endograft volume.

RESULTS

Of 34 patients treated with SMP devices and followed per protocol, 33 patients were evaluable at 1 year. Preprocedural aneurysm volume was 181.4 mL (95% confidence interval [CI], 150.7-212.1 mL) and preprocedural aneurysm diameter was 60.8 mm (95% CI, 57.8-63.9 mm). The target lumen volume was 56.3 mL (95% CI, 46.9-65.8 mL). Technical success was 100% and the ratio of SMP fully expanded volume to estimated target lumen volume was 1.4 ± 0.3. Baseline normalized sac volume and diameter were 140.7 mL (95% CI, 126.6-154.9 mL) and 61.0 mm (95% CI, 59.7-62.3 mm). The adjusted mean percentage change in normalized volume at 1 year was -28.8% (95% CI, -35.3 to -22.3%; P < .001). The adjusted mean change in sac diameter at 1 year was -5.9 mm (95% CI, -7.5 to -4.4 mm; P < .001). At 1 year, 81.8% of patients (95% CI, 64.5%-93.0%) achieved a ≥10% decrease in normalized volume and 57.6% of patients (95% CI, 39.2%-74.5%) achieved a ≥5 mm decrease in diameter. No device- or study procedure-related major adverse events occurred through 1 year after the procedure.

CONCLUSIONS

Treatment of AAA sacs with SMP devices during EVAR resulted in significant sac volume and diameter regression at 1 year with an acceptable safety profile in this prospective study.

Increasing abdominal aortic aneurysm curvature visibility using 3D dual probe bistatic ultrasound imaging combined with probe translation

High frame rate ultrasound (US) imaging techniques in 3D are promising tools for capturing abdominal aortic aneurysms (AAAs) over time, however, with the limited number of channel-to-element connections current footprints are small, which limits the field of view. Moreover, the maximal steering angle of the ultrasound beams in transmit and the maximal receptance angle in receive are insufficient for capturing the curvy shape of the AAA. Therefore, an approach is needed towards large arrays. In this study, high frame rate bistatic 3D US data (17 Hz) were acquired with two synchronized matrix arrays positioned at different locations (multi-aperture imaging) using a translation stage to simulate what a larger array with limited channel-to-element connections can potentially achieve. Acquisitions were performed along an AAA shaped phantom with different probe tilting angles (0 up to ± 30°). The performance of different multi-aperture configurations was quantified using the generalized contrast-to-noise ratio of the wall and lumen (gCNR). Furthermore, a parametric model of the multi-aperture system was used to estimate in which AAA wall regions the contrast is expected to be high. This was evaluated for AAAs with increasing diameters and curvature. With an eight-aperture 0° probe angle configuration a 69 % increase in field of view was measured in the longitudinal direction compared to the field of view of a single aperture configuration. When increasing the number of apertures from two to eight, the gCNR improved for the upper wall and lower wall by 35 % and 13 % (monostatic) and by 36 % and 13 % (bistatic). Contrast improvements up to 22 % (upper wall) and 12 % (lower wall) are achieved with tilted probe configurations compared to non-tilted configurations. Moreover, with bistatic imaging with tilted probe configurations gCNR improvements up to 4 % (upper wall) and 7 % (lower wall) are achieved compared to monostatic imaging. Furthermore, imaging with a larger inter-probe distance improved the gCNR for a ± 15° probe angle configuration. The gCNR has an expected pattern over time, where the contrast is lower when there is more wall motion (systole) and higher when motion is reduced (diastole). Furthermore, a higher frame rate (45 Hz) yields a lower gCNR, because fewer compound angles are used. The results of the parametric model suggest that a flat array is suitable for imaging AAA shapes with limited curvature, but that it is not suitable for imaging larger AAA shapes with more curvature. According to the model, tilted multi-aperture configurations combined with bistatic imaging can achieve a larger region with high contrast compared to non-tilted configurations. The findings of the model are in agreement with experimental findings. To conclude, this study demonstrates the vast improvements in field of view and AAA wall visibility that a large, sparsely populated 3D array can potentially achieve when imaging AAAs compared to single or dual aperture imaging. In the future, larger arrays, less thermal noise, more steering, and more channel-to-element connections combined with carefully chosen orientations of (sub-) apertures will likely advance 3D imaging of AAAs.

3-D Contrast-Enhanced Fusion Ultrasound for Accurate Volume Assessment of Vessel Lumen and Plaque in Carotid Artery Disease as Compared With Computed Tomography Angiography

OBJECTIVE

Three-dimensional contrast-enhanced fusion ultrasound (CEFUS) of atherosclerotic carotid arteries provides spatial visualization of the vessel lumen, creating a lumenography. As in 3-D computed tomography angiography (CTA), 3-D CEFUS outlines the contrast-filled lumen. Plaque and vessel contours are distinguished in 3-D CEFUS, allowing plaque volume quantification as a valid estimate of carotid plaque burden. Three-dimensional CEFUS is unproven in intermodality studies, vindicating the assessment of 3-D CEFUS applicability and comparing 3-D CEFUS and 3-D CTA lumenography as a proof-of-concept study.

METHODS

Using an ultrasound system with magnetic tracking, a linear array transducer and SonoVue contrast agent, 3-D CEFUS acquisitions were generated by spatial stitching of serial 2-D images. From 3-D CEFUS and 3-D CTA imaging, the atherosclerotic carotid arteries were reconstructed with lumenography in an offline software program for lumen and plaque volume quantification. Bland-Altman analysis was used for inter-image modality agreement.

RESULTS

The study included 39 carotid arteries. Mean lumen and plaque volume in 3-D CEFUS were 0.63 cm3 (standard deviation [SD]: 0.26) and 0.62 cm3 (SD: 0.26), respectively. Lumen volume differences between 3-D CEFUS and 3-D CTA were non-significant, with a mean difference of 0.01 cm3 (SD: 0.02, p = 0.26) and limits of agreement (LoA) range of ±0.11 cm3. Mean plaque volume difference was -0.12 cm3 (SD: 0.19, p = 0.006) with a LoA range of ±0.39 cm3.

CONCLUSION

There was strong agreement in lumenography between 3-D CEFUS and 3-D CTA. The interimage modality difference in plaque volumes was substantial because of challenging vessel wall definition in 3-D CTA. Three-dimensional CEFUS is viable in quantifying carotid plaque volume burden and can potentially monitor plaque development over time.

Limb graft occlusion after endovascular aneurysm repair with the Cook Zenith Alpha abdominal graft

OBJECTIVE

Prior reports of the low profile Zenith Alpha abdominal graft (Cook Medical Inc, Bloomington, IN) have shown impaired limb graft patency to be the primary causes of reintervention. Special notices from the manufacturer have indicated certain instructions for use (IFU) violations as the main reasons for these complications. In the present study, we assessed the incidence of limb graft occlusion (LGO) and analyzed the effects of the detailed anatomic risk factors for LGO highlighted in the IFU and previously reported studies.

METHODS

A retrospective study was performed of 241 patients treated with the low profile Zenith Alpha at a single institution from October 1, 2015 to September 30, 2018. All computed tomography angiograms were analyzed using three-dimensional software. Data were extracted from the electronic medical records until the end of the study period (December 31, 2020). The cumulative incidence of LGO and LGO-related reinterventions were assessed. A regression analysis was performed to evaluate the possible risk factors associated with the development of LGO at specified time points. These included aortic and iliac diameters, graft component oversizing, iliac tortuosity and calcification, overlap of graft components, proximal alignment of ipsilateral and contralateral legs, and sealing zone in the external iliac artery. Reader agreement of iliac calcification and tortuosity was assessed in patients with LGO.

RESULTS

A total of 33 limbs (7%) in 27 patients (11%) had become occluded. The cumulative incidence of LGO was 7% (95% confidence interval [CI], 5%-9%) per limb up to 3 years postoperatively. The previously described risk factors for LGO were studied using regression analysis; however, no positive association with LGO was identified. Heavily calcified common iliac arteries (CIAs) and external iliac arteries were protective against LGO compared with noncalcified vessels up to 3 years postoperatively (decreased risk, 17% [95% CI, -27% to -7%]; P = .001; and 15% [95% CI, -26 to -5]; P = .005, respectively). The reader agreement of iliac calcification and tortuosity showed substantial agreement (CIA intrareader kappa = 0.75; CIA interreader kappa = 0.62) and almost perfect agreement (intrareader kappa = 0.85; interreader kappa = 0.84), respectively.

CONCLUSIONS

The cumulative incidence of LGO after endovascular aneurysm repair with the Zenith Alpha graft was 7% per limb up to 3 years postoperatively. None of the analyzed risk factors suggested by the IFUs or current literature were positively associated with LGO.

One-year volume growth of abdominal aortic aneurysms measured by extended field-of-view ultrasound

BACKGROUND

Measurement of volume has the potential to detect subtle growth not recognized in the current surveillance paradigm of abdominal aortic aneurysms (AAAs). Currently available three-dimensional ultrasound allows for estimation of AAA volume, but for most patients, the AAA extends beyond the ultrasound field-of-view and only allows visualization of a partial AAA volume. A new extended field-of-view three-dimensional ultrasound protocol (XFoV US) has been found to improve the proportion of patients with visualization of the full AAA volume.

METHODS

To investigate the applicability of the XFoV US protocol in estimating AAA volume growth in follow-up, 86 patients with AAAs were recruited from the surveillance program at a university hospital. All were imaged by XFoV US at baseline and at one-year follow-up.

RESULTS

Assessment of full volume, based on visualization of the AAA neck and bifurcation at both baseline and one-year follow-up, was achieved in 67/86 (78%) of patients. One-year mean growth in maximum diameter was 2.8 mm (6%/year), in centerline length 2.9 mm (4%/year), and in volume 15.9 mL (19%/year). In 17/67 (25%) of patients, volume growth was detected in diameter-stable AAAs. Baseline XFoV US volume was associated with one-year AAA volume growth, while, conversely, maximum baseline diameter was not associated with one-year AAA diameter growth.

CONCLUSIONS

This study concludes that the XFoV US protocol provides a safe and repeatable modality for assessing AAA volume growth, and that AAA volume is a promising predictive measure of AAA growth.

Local and global distensibility assessment of abdominal aortic aneurysms in vivo from probe tracked 2D ultrasound images

Rupture risk estimation of abdominal aortic aneurysm (AAA) patients is currently based on the maximum diameter of the AAA. Mechanical properties that characterize the mechanical state of the vessel may serve as a better rupture risk predictor. Non-electrocardiogram-gated (non-ECG-gated) freehand 2D ultrasound imaging is a fast approach from which a reconstructed volumetric image of the aorta can be obtained. From this 3D image, the geometry, volume, and maximum diameter can be obtained. The distortion caused by the pulsatility of the vessel during the acquisition is usually neglected, while it could provide additional quantitative parameters of the vessel wall. In this study, a framework was established to semi-automatically segment probe tracked images of healthy aortas (N = 10) and AAAs (N = 16), after which patient-specific geometries of the vessel at end diastole (ED), end systole (ES), and at the mean arterial pressure (MAP) state were automatically assessed using heart frequency detection and envelope detection. After registration AAA geometries were compared to the gold standard computed tomography (CT). Local mechanical properties, i.e., compliance, distensibility and circumferential strain, were computed from the assessed ED and ES geometries for healthy aortas and AAAs, and by using measured brachial pulse pressure values. Globally, volume, compliance, and distensibility were computed. Geometries were in good agreement with CT geometries, with a median similarity index and interquartile range of 0.91 [0.90-0.92] and mean Hausdorff distance and interquartile range of 4.7 [3.9-5.6] mm. As expected, distensibility (Healthy aortas: 80 ± 15·10^-3 kPa^-1; AAAs: 29 ± 9.6·10^-3 kPa^-1) and circumferential strain (Healthy aortas: 0.25 ± 0.03; AAAs: 0.15 ± 0.03) were larger in healthy vessels compared to AAAs. Circumferential strain values were in accordance with literature. Global healthy aorta distensibility was significantly different from AAAs, as was demonstrated with a Wilcoxon test (p-value = 2·10^-5). Improved image contrast and lateral resolution could help to further improve segmentation to improve mechanical characterization. The presented work has demonstrated how besides accurate geometrical assessment freehand 2D ultrasound imaging is a promising tool for additional mechanical property characterization of AAAs.