Time-resolved computed tomography imaging of the aorta: a feasibility study

Dynamic Computed Tomography Angiography as Imaging Method for Endoleak Classification after Endovascular Aneurysm Repair: A Case Series and Systematic Review of the Literature

INTRODUCTION

This study evaluated our experience with dynamic computed tomography angiography (dCTA) as a diagnostic tool after endovascular aortic aneurysm repair (EVAR) with respect to the endoleak classification and the available literature.

METHODS

We reviewed all patients who underwent dCTA because of suspected endoleaks after the EVAR and classified the endoleaks in these patients based on standard CTA (sCTA) and dCTA. We systematically reviewed all available publications that investigated the diagnostic accuracy of dCTA compared with other imaging techniques.

RESULTS

In our single-center series, 16 dCTAs were performed in 16 patients. In 11 patients, the undefined endoleaks that appeared on sCTA scans were successfully classified using dCTA. In three patients with a type II endoleak and aneurysm sac growth, inflow arteries were successfully identified using dCTA, and in two patients, aneurysm sac growth was observed without a visible endoleak on both sCTA and dCTA scans. The dCTA revealed four occult endoleaks, all of which were type II endoleaks. The systematic review identified six series comparing dCTA with other imaging methods. All articles reported an excellent outcome regarding the endoleak classification. In published dCTA protocols, the number and timing of phases varied greatly, affecting radiation exposure. Time attenuation curves of the current series show that some phases do not contribute to the endoleak classification and that the use of a test bolus improves the timing of the dCTA.

CONCLUSIONS

The dCTA is a valuable additional tool that can identify and classify endoleaks more accurately than the sCTA. Published dCTA protocols vary greatly and should be optimized to decrease radiation exposure as long as accuracy can be maintained. The use of a test bolus to improve the timing of the dCTA is recommended, but the optimal number of scanning phases is yet to be determined.

Dynamic, Time-Resolved CT Angiography After EVAR: A Quantitative Approach to Accurately Characterize Aortic Endoleak Type and Identify Inflow Vessels

PURPOSE

Our purpose was to study the accuracy of dynamic computed tomography angiography (d-CTA) in characterizing endoleak type, inflow vessels as compared with digital subtraction angiography (DSA) using qualitative and quantitative analysis.

METHODS

Between March 2019 and January 2021, all patients who underwent d-CTA imaging after EVAR were retrospectively reviewed. Two blinded independent reviewers qualitatively reviewed d-CTA and DSA images. Quantitative region of interest (ROI) analysis was performed by measuring time-resolved contrast enhancement within the aorta and endoleak lesion(s) in the aneurysm sac. Differences between time-to-peak enhancement (Δ TTP) across different ROIs were quantified.

RESULTS

A total of 48 patients underwent d-CTA during the study period, of whom 24 patients had abdominal EVAR and DSA imaging for comparison. Qualitative review of DSA imaging showed type I (n=4), type II (n=16), and type III (n=2) and no endoleak (n=2). In 23 of 24 patients (95.8%), d-CTA findings correlated with DSA findings for endoleak type. One patient had a type III endoleak that was demonstrated only in d-CTA (arising from defect in polymer sealing ring of Ovation stent graft) imaging. In type II endoleak cases, d-CTA identified more inflow vessels than DSA imaging (33 vs 21 vessels, p=0.010). Quantitative analysis showed mean (±SD) Δ TTP values for type I endoleak as 1.8 (±1.8) seconds, type II as 9.6 (±3.5) seconds, and for type III endoleak as 5.6 (±1.3) seconds.

CONCLUSION

Dynamic CTA can accurately characterize aortic endoleak type, inflow vessels as compared with DSA imaging. Quantitative parameters such as Δ TTP enhancement can help better differentiate endoleak types and provide an objective approach to endoleak diagnosis.

Dynamic CT angiography is more accurate in diagnosing endoleaks than standard triphasic CT angiography and enables targeted embolization

PURPOSE

The primary objective was to compare the accuracy of dynamic CT angiography (d-CTA) with standardized triphasic contrast enhanced CT angiography (t-CTA) in diagnosing endoleak type after endovascular aortic repair (EVAR) using digital subtraction angiography (DSA) as reference standard. The secondary objective was to study the impact of d-CTA on image-fusion guided endoleak embolization.

MATERIALS AND METHODS

Retrospective review of patients who underwent d-CTA imaging after EVAR between March 2019 and July 2021 was performed. De-identified images were independently reviewed by two-two blinded readers to document endoleak type and target vessels. Impact of d-CTA-guided embolization was evaluated by number of planning angiograms, radiation exposure and accuracy of target vessel overlay.

RESULTS

During the study period, 52 patients underwent d-CTA, 19 had all three modalities available for analysis. DSA imaging confirmed 4(21.0%) type-I, 14(73.7%) type-II and 1(5.3%) type-III endoleak. Findings from d-CTA matched with DSA in 19/19 cases (100%), whereas t-CTA matched in 14/19 cases (73.7%). In type-II endoleaks, number of target vessels identified by d-CTA, t-CTA and DSA were 23, 17 and 16 respectively. Mean dose-length product from d-CTA and t-CTA was 1445±551 and 1612±530 mGy*cm (p=0.26). Nine patients underwent d-CTA-guided type-II endoleak embolization, using a median of 1(range:1-4) planning angiogram before embolization utilizing 21.6(±8.7)% of total procedural radiation dose. Target vessel overlay was accurate in 9/9(100%) cases.

CONCLUSION

Dynamic, time-resolved CTA is more accurate compared to standardized triphasic contrast enhanced CTA in diagnosing endoleak type after EVAR. In type-II endoleak, d-CTA better identified target vessels and enabled safe, targeted embolization.

The added value of CT virtual angioscopy to MDCT angiography in the evaluation of aortic diseases

PURPOSE

Incorporation of virtual angioscopy (VA) in the diagnostic work-up of aortic diseases could improve the clinical value and efficiency of multidetector computed tomography angiography (MDCTA). We aim to evaluate the clinical usefulness of virtual aortic navigation by CT angiography in various aortic diseases as a complement to standard MDCTA.

MATERIALS AND METHODS

We retrospectively selected 211 patients who performed MDCTA for suspected or operated aortic diseases. VA endoluminal images of the aorta were obtained by a fly-through technique. Two senior vascular radiologists independently evaluated all MDCTA images. After 1 month, the same two radiologists independently reviewed the MDCTA images combined with CTVA images. The respective accuracy of CTVA in delineating aortic abnormalities was compared to that of MDCTA using Fisher's exact test. The Fleiss kappa (κ) statistic was used to assess the inter-reader agreement (IRA).

RESULTS

We detected 229 abnormalities in 203 patients on MDCTA and 231 abnormalities in 205 patients on CTVA. CTVA provided significant additional findings in 63.8% (146/229) of all abnormalities diagnosed by MDCTA (p < 0.001, odd ratio [OR] = 42). Although CTVA diagnosed two abnormalities overlooked by MDCTA, the value was statistically insignificant (p = 0.787, OR = 1.3). Regarding postoperative abnormalities, the CTVA added significant additional findings over MDCTA (p = 0.006, OR = 87.4). The overall IRA for the performance of CTVA was good (κ = 0.699).

CONCLUSIONS

CTVA yields extra findings and improves diagnostic efficiency of MDCTA, especially in postoperative patients.

Can multiphase dynamic CT angiography provide a better assessment of aortic dissection compared with the standard triphasic protocol?

Background Acute aortic dissection (AD) is a life-threatening medical emergency. It has been debated whether the multiphase dynamic computed tomography angiography (CTA) protocol is superior to the standard triphasic protocol for revealing the characteristics of AD. Purpose To examine two multiphase dynamic protocols, Dynamic four-dimensional (4D) CTA using the shuttle mode and Flash 4D CTA using the high-pitch mode for the assessment of AD and to compare them with the standard triphasic protocol. Material and Methods A total of 54 consecutive patients were randomly and equally assigned to three groups and scanned with a second-generation DSCT scanner. Groups A, B, and C were assessed with the Dynamic 4D CTA in the shuttle mode, the Flash 4D CTA in the high-pitch mode, and the standard triphasic acquisition protocol, respectively. Image quality of all patients was evaluated. The effective radiation dose (ED) was recorded. Results In 54 patients, CTA images could display the true and false lumens, the intimal flap, the entry tear, and branch vessel involvement in the AD. Compared with group C, additional diagnostic information was obtained in groups A and B, including the dynamic enhancement delay between the true and false lumens (A = 18, B = 18); the presence of membrane oscillation (A = 8, B = 14); dynamic ejection of the contrast material from the true lumen into the false lumen (A = 6, B = 7); and the dynamic obstruction of the left renal artery (B = 2). The ED in these three groups was significantly different ( P < 0.05). Conclusion Compared to the standard triphasic protocol, the multiphase dynamic CTA protocol is feasible and is able to reveal additional diagnostic information. Therefore, we recommend using the high-pitch, dual-source multiphase dynamic CTA to assess ADs.

Optimizing multidetector CT for visualization of splenic vascular injury. Validation by splenic arteriography in blunt abdominal trauma patients

Nonoperative management of blunt splenic injury is the treatment of choice in hemodynamically stable patients. Detection of vascular injury by multidetector CT (MDCT) is the most significant factor predicting the need for endovascular treatment. This study evaluated the timing of the appearance of vascular lesions during angiography. Images from 20 patients embolized for pseudoaneurysms (PSA) were evaluated. Angiograms were reviewed for phase and timing of PSA. Admission MDCT was reviewed for injury grade and PSA. Initial MDCT evaluation indicated grade III and IV splenic injuries in 9 and 11 patients, respectively. PSA was seen on MDCT in 14/20 (70%) patients. Time from opacification of the aorta to vascular injury was 1.32 s for arterial phase injuries compared with 2.05 s for postcapillary injuries (P=0.097). Angiography demonstrated 15 vascular injuries during the arterial and 5 in the venous phase. Of injuries seen during arterial phase angiography, 10/15 (66%) were identified on MDCT. Of the five injuries that exhibited postcapillary-phase findings, 4/5 (80%) demonstrated PSA (P=0.5). Vascular lesions are a better indicator of subsequent clinical deterioration than splenic injury grade. PSAs are more frequently seen in postcapillary vascular injuries than arterial phase lesions with the current timing of MDCT. In a subset of patients in whom splenic injury grades III and IV warrant angiography, PSAs are not initially demonstrated on MDCT. Therefore, alteration of MDCT timing parameters to better correlate with arterial phase angiography may improve initial diagnosis of vascular injury.