Vascular assessment after clipping surgery using four-dimensional CT angiography

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.

Stroke Mimics and Chameleons from the Radiological Viewpoint of Glioma Diagnosis

Gliomas are sometimes difficult to differentiate from strokes and are often misdiagnosed on magnetic resonance imaging (MRI); thus, the terms “stroke mimics” and “stroke chameleons” have been introduced. In this study, we analyzed stroke mimics and stroke chameleons in glioma and discussed the diagnostic perplexity. We retrospectively reviewed cases that were removed from lesions that were considered to be brain tumors. This study enrolled 214 patients who underwent tumor resection for suspected glioma. Clinical characteristics and radiological findings of the patients were compared between the masquerade findings group, which was further divided into two groups: the stroke chameleons and stroke mimics according to their final diagnosis, and the intelligible findings group. Stroke chameleons and stroke mimics were significantly higher in age and smaller in lesion size than the intelligible findings group. In the multivariate analysis, the predictive factor of the masquerade finding group was higher age and smaller size. Stroke mimics group has a tendency to be higher rate of hyperintensity lesion on diffusion-weighted imaging (DWI) compared with stroke chameleons group. The average period from initial diagnosis to pathological diagnosis was 13.50 days in the stroke chameleons and 61.50 days in the stroke mimics, which proved significantly different. Proper diagnosis of glioma and stroke affects a patient’s prognosis, and should be diagnosed as soon as possible. However, stroke mimics and stroke chameleons caused by glioma can occur. Thus, the diagnosis of a stroke should take into consideration the possibility of a glioma in real clinical situations.

[Completeness of brain aneurysm exclusion according to CT angiography]

OBJECTIVE

To develop a classification of the completeness of brain aneurysm exclusion according to CT angiography for determining further diagnostic and curative strategy.

MATERIAL AND METHODS

The study included 138 patients who had 164 brain aneurysms. Clipping was carried out at the Burdenko Neurosurgery Center in 2013-2017. Titanium clips were used in 111 cases, cobalt clips - in 53 patients.

RESULTS

Completeness of brain aneurysm exclusion was assessed in 149 cases using CT angiography. In 15 cases, artifacts from cobalt clips impaired assessment. Total exclusion was achieved in 136 (91.3%) cases, subtotal (a remainder of residual neck) - in 10 (6.7%) cases, complete exclusion of the body and bottom (patent neck) - 2 (1.3%) patients, partial exclusion (partially patent bottom) - 1 patient (0.7%). In this series, a clip prevented complete contrast enhancement of brain aneurysm bottom in all cases.

CONCLUSION

CTA is a reliable method for assessing the quality of exclusion of brain aneurysm in patients with implanted titanium clips. In case of cobalt clips, stratification depending on severity of CT artifacts should be performed for data interpretation. In some cases, artifacts impair visualization of the vessels adjacent to the clips. In these patients, direct cerebral angiography or dual-energy computed tomography scanners with metal artifact suppression programs should be recommended.

Follow-up is recommended for patients with remnants of residual cervix. Redo surgery is indicated for completely patent neck, as well as partial or complete contrast enhancement of aneurysm bottom.