Metal artifact reduction algorithm for image quality improvement of cone-beam CT images of medium or large cerebral aneurysms treated with stent-assisted coil embolization

Safety and Efficacy of LVIS Jr Stent-assisted Coiling of Intracranial Aneurysms in Small-diameter Parent Arteries : A Single-center Experience

OBJECTIVE

To investigate the safety and efficacy of LVIS Jr stent-assisted coiling (SAC) of intracranial aneurysms (IAs) in small-diameter parent arteries and determine the factors influencing incomplete aneurysm occlusion.

MATERIAL AND METHODS

Clinical and imaging data of 130 patients with IAs in small-diameter parent arteries that were treated with LVIS Jr SAC were retrospectively analyzed. Stent apposition was evaluated by high-resolution flat detector CT, and aneurysm embolization density was evaluated using 2D-DSA. Perioperative complications were recorded. Multivariate logistic regression analyses were performed to determine possible factors for incomplete aneurysm occlusion.

RESULTS

In this study, 130 patients (60 and 70 patients with ruptured and unruptured aneurysms, respectively) were successfully treated with LVIS Jr SAC. Immediate digital subtraction angiography (DSA) showed that the aneurysm occlusion was Raymond-Roy class I, II, IIIa, and IIIb in 93 (71.5%), 24 (18.5%), 8 (6.2%), and 5 (3.8%) cases, respectively. There were three cases of acute in-stent thrombosis and two cases of severe vasospasm observed during the perioperative period. The 6‑month follow-up angiograms indicated that complete aneurysm occlusion in 122 patients was 79.5% (97/122). Multivariate logistic regression analyses showed that an aneurysm size > 10.0 mm, parent artery mean diameter < 2.0 mm, and incomplete stent apposition at the aneurysm neck were possible risk factors for incomplete aneurysm occlusion.

CONCLUSION

The LVIS Jr SAC is effective for managing IAs in small-diameter parent arteries. An aneurysm size > 10.0 mm, parent artery mean diameter < 2.0 mm, and incomplete stent apposition at the aneurysm neck are possible risk factors for incomplete aneurysm occlusion.

Single-Energy Metal Artifact Reduction (SEMAR) in Ultra-High-Resolution CT Angiography of Patients with Intracranial Implants

PURPOSE

To evaluate the effects of single-energy metal artifact reduction (SEMAR) on image quality of ultra-high-resolution CT-angiography (UHR-CTA) with intracranial implants after aneurysm treatment.

METHODS

Image quality of standard and SEMAR-reconstructed UHR-CT-angiography images of 54 patients who underwent coiling or clipping was retrospectively evaluated. Image noise (i.e., index for metal-artifact strength) was analyzed in close proximity to and more distally from the metal implant. Frequencies and intensities of metal artifacts were additionally measured and intensity-differences between both reconstructions were compared in different frequencies and distances. Qualitative analysis was performed by two radiologists using a four-point Likert-scale. All measured results from both quantitative and qualitative analysis were then compared between coils and clips.

RESULTS

Metal artifact index (MAI) and the intensity of coil-artifacts were significantly lower in SEMAR than in standard CTA in close vicinity to and more distally from the coil-package (p < 0.001, each). MAI and the intensity of clip-artifacts were significantly lower in close vicinity (p = 0.036; p < 0.001, respectively) and more distally from the clip (p = 0.007; p < 0.001, respectively). In patients with coils, SEMAR was significantly superior in all qualitative categories to standard images (p < 0.001), whereas in patients with clips, only artifacts were significantly less (p < 0.05) for SEMAR.

CONCLUSION

SEMAR significantly reduces metal artifacts in UHR-CT-angiography images with intracranial implants and improves image quality and diagnostic confidence. SEMAR effects were strongest in patients with coils, whereas the effects were minor in patients with titanium-clips due to the absent of or minimal artifacts.

A case of delayed foreshortening and disconnection of pipeline embolization device detected by chronological cone-beam computed tomography fusion image

OBJECTIVE

The morphological changes of the pipeline embolization device (PED; Medtronic, Minneapolis, MN, USA), such as delayed migration or foreshortening, can relate to the incomplete occlusion of aneurysms.

CASE PRESENTATION

A 30-year-old man with a giant cavernous carotid artery aneurysm was treated with two PEDs using the overlapping technique. Six months after treatment, follow-up angiography showed morphological changes of the PEDs and residual flow into the aneurysm. Chronological cone-beam computed tomography fusion imaging clearly revealed the dynamic foreshortening of the first PED and the disconnection of both PEDs, so we decided to implant an additional PED.

CONCLUSION

This case illustrates that a three-dimensional understanding can be useful for assessing the cause of treatment failure or recurrence.

Clinical Evaluation of an Innovative Metal-Artifact-Reduction Algorithm in FD-CT Angiography in Cerebral Aneurysms Treated by Endovascular Coiling or Surgical Clipping

Treated cerebral aneurysms (IA) require follow-up imaging to ensure occlusion. Metal artifacts complicate radiologic assessment. Our aim was to evaluate an innovative metal-artifact-reduction (iMAR) algorithm for flat-detector computed tomography angiography (FD-CTA) regarding image quality (IQ) and detection of aneurysm residua/reperfusion in comparison to 2D digital subtraction angiography (DSA). Patients with IAs treated by endovascular coiling or clipping underwent both FD-CTA and DSA. FD-CTA datasets were postprocessed with/without iMAR algorithm (MAR+/MAR−). Evaluation of all FD-CTA and DSA datasets regarding qualitative (IQ, MAR) and quantitative (coil package diameter/CPD) parameters was performed. Aneurysm occlusion was assessed for each dataset and compared to DSA findings. In total, 40 IAs were analyzed (ncoiling = 24; nclipping = 16). All iMAR+ datasets demonstrated significantly better IQ (pIQ coiling < 0.0001; pIQ clipping < 0.0001). iMAR significantly reduced the metal-artifact burden but did not affect the CPD. iMAR significantly improved the detection of aneurysm residua/reperfusion with excellent agreement with DSA (naneurysm detection MAR+/MAR−/DSA = 22/1/26). The iMAR algorithm significantly improves IQ by effective reduction of metal artifacts in FD-CTA datasets. The proposed algorithm enables reliable detection of aneurysm residua/reperfusion with good agreement to DSA. Thus, iMAR can help to reduce the need for invasive follow-up in treated IAs.

Treatment of Ruptured and Nonruptured Aneurysms Using a Semisolid Iodinated Embolic Agent

Saccular aneurysms (SAs) are focal outpouchings from the lateral wall of an artery. Depending on their morphology and location, minimally invasive treatment options include coil embolization, flow diverter stents, stent-assisted coiling, and liquid embolics. Many drawbacks are associated with these treatment options including recanalization, delayed healing, rebleeding, malpositioning of the embolic or stent, stent stenosis, and even rupture of the SA. To overcome these drawbacks, a nanoclay-based shear-thinning hydrogel (STH) is developed for the endovascular treatment of SAs. Extensive in vitro testing is performed to optimize STH performance, visualization, injectability, and endothelialization in cell culture. Femoral artery saccular aneurysm models in rats and in pigs are created to test stability, efficacy, immune response, endothelialization, and biocompatibility of STH in both ruptured and unruptured SA. Fluoroscopy and computed tomography imaging consistently confirmed SA occlusion without recanalization, migration, or nontarget embolization; STH is also shown to outperform coil embolization of porcine aneurysms. In pigs with catastrophic bleeding due to SA rupture, STH is able to achieve instant hemostasis rescuing the pigs in long-term survival experiments. STH is a promising semisolid iodinated embolic agent that can change the standard of medical practice and potentially save lives.