Conventional digital subtractional vs non-invasive MR angiography in the assessment of brain arteriovenous malformation

Low-dose contrast-enhanced time-resolved angiography with stochastic trajectories with iterative reconstruction (IT-TWIST-MRA) in brain arteriovenous shunt

OBJECTIVES

To assess the feasibility of low-dose contrast-enhanced four-dimensional (4D) time-resolved angiography with stochastic trajectories (TWIST) with iterative reconstruction (hereafter IT-TWIST-MRA) covering the whole brain and to compare IT-TWIST-MRA and TWIST-MRA with reference to digital subtraction angiography (DSA) in the evaluation of arteriovenous shunts (AVS).

METHODS

Institutional Review Board approval was obtained for this observational study, and the requirement for written informed consent was waived. Twenty-nine patients with known AVS underwent TWIST-MRA on a 3-T MRI scanner, using low-dose injection (0.02 mmol/kg) of gadolinium-based contrast agent (GBCA) with each of Fourier and iterative reconstruction between September 2016 and October 2019. Visual evaluation of image quality was conducted for delineation of (a) the normal cerebral arteries and veins and (b) AVS feeder, shunt, and drainer vessels. Region-of-interest evaluation was conducted to evaluate bolus sharpness and baseline signal fluctuation in the signal intensity of the cerebral vessels. We compared the detection of AVS between TWIST-MRA and IT-TWIST-MRA. The paired-samples Wilcoxon test was used to test the differences between TWIST-MRA and IT-TWIST-MRA.

RESULTS

Visualization scores for normal vasculature and AVS angioarchitecture were significantly better for images produced using IT-TWIST-MRA than those using TWIST-MRA. Peak signal and the enhancement slope of the time-intensity curve were significantly higher for IT-TWIST-MRA than for TWIST-MRA, except for the superior sagittal sinus (SSS). Baseline intensity fluctuation was significantly lower for IT-TWIST-MRA than for TWIST, except for SSS.

CONCLUSIONS

IT-TWIST-MRA yields clinically feasible 4D MR-DSA images and delineates AVS even with low-dose GBCA.

KEY POINTS

• Iterative reconstruction significantly improves the image quality of TWIST-MRA covering the whole brain. • The short temporal footprint and denoising effect of iterative reconstruction enhances the quality of 4D-MRA. • IT-TWIST-MRA yields clinically feasible images of AVS with low-dose GBCA.

State of the Art and Future Direction in Diagnosis, Molecular Biology, Genetics, and Treatment of Brain Arteriovenous Malformations

Brain arteriovenous malformations (bAVMs) are uncommon and represent a heterogeneous group of lesions. Although these 2 facts have delayed research on this topic, knowledge about the pathophysiology, diagnosis, and treatment of bAVMs has evolved in recent years. We conducted a review of the literature to update the knowledge about diagnosis, molecular biology, genetic, pathology, and treatment by searching for the following terms: "Epidemiology AND Natural History," "risk of hemorrhage," "intracranial hemorrhage," "diagnosis," "angiogenesis," "molecular genetics," "VEGF," "KRAS," "radiosurgery," "endovascular," "microsurgery," or "surgical resection." Our understanding of bAVMs has significantly evolved in recent years. The latest investigations have helped in defining some molecular pathways involved in the pathology of bAVM. Although there is still more to learn and discover, describing these pathways will allow the creation of targeted treatments that could improve the prognosis of patients with bAVMs.

MRI and MR angiography evaluation of pulsatile tinnitus: A focused, physiology-based protocol

BACKGROUND AND PURPOSE

Pulsatile tinnitus (PT) is the subjective sensation of a pulse-synchronous sound, most often due to a cerebrovascular etiology. PT can severely impact quality of life and may indicate a life-threatening process, yet a timely and accurate diagnosis can often lead to effective treatment. Clinical assessment with a history and physical examination can often suggest a diagnosis for PT, but is rarely definitive. Therefore, PT should be evaluated with a comprehensive and targeted radiographic imaging protocol. MR imaging provides a safe and effective means to evaluate PT. Specific MR sequences may be used to highlight different elements of cerebrovascular anatomy and physiology. However, routine MR evaluation of PT must comply with economic and practical constraints, while effectively capturing both common and rarer, life-threatening etiologies of PT.

METHODS

In this state-of-the-art review, we describe our institutional MR protocol for evaluating PT.

RESULTS

This protocol includes the following dedicated sequences: time-of-flight magnetic resonance angiography; arterial spin labeling; spoiled gradient recalled acquisition in the steady state; time-resolved imaging of contrast kinetics; diffusion weighted imaging, and 3-dimensional fluid-attenuated inversion recovery.

CONCLUSIONS

We describe the physiologic and clinical rationale for including each MR sequence in a comprehensive PT imaging protocol, and detail the role of MR within the broader evaluation of PT, from clinical presentation to treatment.

The use of contrast-enhanced, time-resolved magnetic resonance angiography in cerebrovascular pathology

Digital subtraction angiography (DSA) has long been the imaging gold standard in the evaluation, treatment, and follow-up of cerebro- and spinovascular disorders. However, DSA has the disadvantages of invasiveness, contrast allergy or nephropathy, the impracticality of procedural preparation and recovery, and expense. Contrast-enhanced (CE), time-resolved (TR) magnetic resonance angiography (CE TR-MRA) is a sophisticated, relatively novel imaging modality that provides multiphasic contrast-enhanced visualization of the neurovasculature. Given the crucial role of angiography in all aspects of care for patients with complex neurovascular disorders, it is incumbent on those who care for these patients to understand the usefulness and pitfalls of novel imaging in this arena to ensure best practices, and to deliver cutting edge care to these patients in a way that minimizes cost, but does not compromise quality. CE TR-MRA has the potential to play an expanded role in the workup and follow-up across the spectrum of neurovascular disease, and this review is aimed to help neurosurgeons better understand how CE TR-MRA can be used to better manage patients in this cohort.

Impact of flow and angioarchitecture on brain arteriovenous malformation outcome after gamma knife radiosurgery: the role of hemodynamics and morphology in obliteration

BACKGROUND

Few studies have evaluated the relationship between brain arteriovenous malformations (bAVMs) angioarchitecture and the response to Gamma Knife Stereotactic Radiosurgery (GKSR).

METHODS

A prospectively enrolled single-center cohort of patients with bAVMs treated by GKSR has been studied to define independent predictors of obliteration with particular attention to angioarchitectural variables. Only patients older than 18 years old (y.o.), who underwent baseline digital subtraction angiography (DSA) and clinico-radiological follow-up of at least 36 months, were included in the study.

RESULTS

Data of 191 patients were evaluated. After a mean follow-up of 80 months (range 37-173), total obliteration rate after first GKSR treatment was 66%. Mean dose higher than 22 Gy (P = .019, OR = 2.39, 95% CI 1.15-4.97) and flow rate dichotomized into high vs non-high (P < .001, OR = 0.23, 95% CI 0.11-0.51) resulted to be independent predictors of obliteration. Flow-surrogate angioarchitectural features did not emerge as independent outcome predictors.

CONCLUSIONS

Flow rate seems to be associated in predicting outcome after GKSR conferring high-flow AVM a lower occlusion rate. Its role should be considered when planning radiosurgical treatment of bAVM, and it could be added to other parameters used in GKRS outcome predicting scales.