Contrast-enhanced angiographic cone-beam computed tomography without pre-diluted contrast medium

A technical note on intra-arterial cone-beam computed tomography for the evaluation of flow-diverter stents: Image quality differences between diluted and non-diluted contrast medium

Background

Design of flow-diverter stents for flexibility, tractability, and low profile limits their radiopacity on conventional digital subtraction angiography. Cone-beam computed tomography (CBCT) offers higher spatial resolution for the evaluation of flow-diverter stents. However, CBCT requires optimal dilution and timing of contrast medium for simultaneous visualization of the stent, arterial lumen, and vessel wall. There are only limited data on the effects of different contrast dilutions on CBCT image quality in neurointerventional applications.

Materials and methods

In our institution, intra-arterial CBCTs were acquired during stent deployment and at follow-ups with 10% diluted contrast. We had recently started acquiring intra-arterial CBCTs with non-diluted contrast. Retrospective analysis of our flow-diverter data identified eight cases with different aneurysm locations who had intra-arterial CBCT with 10% diluted contrast immediately after flow-diverter stent deployment and with non-diluted contrast technique during follow-ups. For each case, the image quality between diluted and non-diluted contrast techniques was compared qualitatively by assessing stent visualization and quantitatively by plotting gray-scale intensity values along the vessel lumen.

Results

In two sets of CBCT images per each case, there was no substantial difference between diluted and non-diluted CBTC techniques for the evaluation of stent architecture and lumen opacification. Gray-scale intensity values perpendicular to the lumen revealed similar intensity values along the neighboring parenchyma, vessel wall, and lumen for the two different contrast techniques.

Conclusion

Intra-arterial CBCT angiography can be performed without contrast dilution and still achieve adequate image quality in certain cerebral aneurysms treated with flow diverter. The non-diluted contrast technique avoids the time loss during preparation of diluted contrast and installation of diluted contrast to the injector in angiography suites with a single power injector.

Optimizing contrast-enhanced cone-beam CT protocol to facilitate simultaneous visualization of neurovascular pathologies and surrounding structures of interest

OBJECTIVE

Contrast-enhanced cone-beam computed tomography (CBCT) imaging is commonly used for evaluating neurovascular stents and their relationship to the parent artery or vascular pathologies such as arteriovenous malformations (AVMs) and dural arteriovenous fistulas (dAVFs) in the context of surrounding anatomical structures. The purpose of this study was to understand the effects of varying concentrations of contrast medium used in CBCT imaging for optimal visualization of various endovascular devices and anatomical pathologies.

METHODS

Thirty-five patients with various neurovascular pathologies were included in the study. Contrast-enhanced CBCT images (20 s DR, Siemens syngo DynaCT, Siemens AG, Forchheim, Germany) were acquired in all cases, with varying dilutions of contrast medium, from 1% to 30%. The injection rate was kept constant at 3 cc/sec with an X-ray delay of two sec, and a total volume of 66 cc of diluted contrast was administered. Results from visual and quantitative analysis were reported.

RESULTS

Ten percent dilution of contrast medium resulted in the best image differentiation between flow-diverter devices and the parent artery. Concentrations as low as 2.5% contrast medium also resulted in identifying AVMs in the context of the surrounding brain parenchyma, whereas 20% to 30% dilution provided the best visualization of residual AVMs with prior Onyx embolization and dAVFs in the presence of bony structures.

CONCLUSIONS

Simultaneous visualization of brain parenchyma, bony structures, devices, and pathological anatomy using contrast-enhanced CBCT imaging is feasible with appropriate doses of iodinated contrast, and should be tailored to the individual case based on the goals of CBCT.

Usefulness of Cone Beam Intra-Arterial CTA for Evaluation of Flow Diverters: A Practical Approach for Daily Use

Cone beam computed tomography (CBCT), initially used for evaluation of intraprocedural complications such as hemorrhage, has evolved to provide details of implanted devices such as flow diverters. The study aim is to present our experience in using CBCT with intra-arterial injection and provide a step-by-step approach for postprocessing in a practical protocol for daily use. IRB approval was obtained, and the neurointerventional database was retrospectively reviewed from July 2012 to June 2017. Patients who underwent cone beam intra-arterial CT angiography for evaluation of implanted flow diverter devices were reviewed. Patient demographics, aneurysm location (internal carotid artery [ICA]-cavernous, ICA-paraclinoid, and ICA-distal; middle cerebral artery [MCA], anterior cerebral artery [ACA]-acom, ACA-pericallosal, vertebral artery [VA]), type (saccular, dissecting fusiform, or blister) and size, device, injection technique (contrast dilution, rate, and volume), and reconstruction protocol were recorded. Acquired images were postprocessed using a Philips Xtravision workstation. Eighty patients (63 women and 17 men) met the inclusion criteria of our study. Age range was 25-80 years old. Treated aneurysms were located in the ICA-paraclinoid in 48 cases (60%), ICA-distal in 12 cases, ICA-cavernous in 8 cases, MCA in 4 cases, VA in 4 cases, ACA-acom in 2 cases, ACA-pericallosal in 2 cases; 69 were saccular, 8 fusiform, and 3 ruptured blister aneurysms. There were 52 small, 20 large, and 8 giant aneurysms. Pipeline (Medtronic, MN, USA) was the predominant device used in 77 procedures. Two injection techniques were used: 2.5 mL/s for a total volume of 55 mL with a 2-s imaging delay or 3 mL/s for a total volume of 70 mL with a 3-s imaging delay; contrast (Ioxilan 300 mgI/mL) dilution was 10-20% in all cases. The device's landing zones, conformability, presence of deformities, and wall apposition were successfully visualized in all cases. Metal artifact reduction program was applied in 9 coiled aneurysms, and this was satisfactory as well.