Intracranial stenting in atherosclerotic disease—recent results and challenges to face

Obesity and intracranial in-stent thrombosis

A morbidly obese, diabetic, hypertensive patient, with severe intracranial left middle cerebral artery (MCA) stenosis, suffered recurrent stereotyped transient ischemic attacks over 2 months, despite taking daily antiplatelet agents, high dose statin, insulin and an angiotensin converting enzyme inhibitor. A left MCA (M1) Wingspan stent-assisted angioplasty was performed after standard loading, and daily doses of clopidogrel were given 3 days prior to the procedure. Immediately after the procedure, the patient developed a left hemispheric ischemic stroke syndrome. Urgent re-angiography identified an acute intracranial in-stent thrombosis. This complication was immediately treated successfully with abciximab and balloon angioplasty. The patient had persistent residual stroke despite complete recanalization of the thrombosed stent within 3 h of occlusion. The patient was subsequently found to have incomplete inhibition of platelet activity despite being on clopidogrel 150 mg and aspirin 81 mg daily and having a normal CYP-2C19 genotype, suggesting that suboptimal antiplatelet inhibition, secondary to morbid obesity, contributed to his in-stent thrombosis. Obese patients undergoing coronary artery stenting routinely receive larger loading and maintenance doses of clopidogrel. Our case suggests that obese patients undergoing intracranial stenting may also benefit from higher than conventional clopidogrel doses prior to intracranial stenting, to decrease risk of acute in-stent occlusion.

High-resolution 3D X-ray imaging of intracranial nitinol stents

INTRODUCTION

To assess an optimized 3D imaging protocol for intracranial nitinol stents in 3D C-arm flat detector imaging. For this purpose, an image quality simulation and an in vitro study was carried out.

METHODS

Nitinol stents of various brands were placed inside an anthropomorphic head phantom, using iodine contrast. Experiments with objects were preceded by image quality and dose simulations. We varied X-ray imaging parameters in a commercially interventional X-ray system to set 3D image quality in the contrast-noise-sharpness space. Beam quality was varied to evaluate contrast of the stents while keeping absorbed dose below recommended values. Two detector formats were used, paired with an appropriate pixel size and X-ray focus size. Zoomed reconstructions were carried out and snapshot images acquired. High contrast spatial resolution was assessed with a CT phantom.

RESULTS

We found an optimal protocol for imaging intracranial nitinol stents. Contrast resolution was optimized for nickel-titanium-containing stents. A high spatial resolution larger than 2.1 lp/mm allows struts to be visualized. We obtained images of stents of various brands and a representative set of images is shown. Independent of the make, struts can be imaged with virtually continuous strokes. Measured absorbed doses are shown to be lower than 50 mGy Computed Tomography Dose Index (CTDI).

CONCLUSION

By balancing the modulation transfer of the imaging components and tuning the high-contrast imaging capabilities, we have shown that thin nitinol stent wires can be reconstructed with high contrast-to-noise ratio and good detail, while keeping radiation doses within recommended values. Experimental results compare well with imaging simulations.