Evaluation of Intracranial Vasculatures in Healthy Subjects with Arterial-Spin-Labeling-Based 4D-MR Angiography at 3T

Iryo, Yasuhiko; Hirai, Toshinori; Nakamura, Masanobu; Tateishi, Machiko; Hayashida, Eri; Azuma, Minako; Nishimura, Shin‐Ichiro; Kitajima, Mika; Yamashita, Yasuyuki

doi:10.2463/mrms.tn.2015-0081

Cited by 4 publications

(3 citation statements)

References 10 publications

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“…24 In 4D CTA, images are taken throughout the administration of a contrast bolus, whereas 4D MRA can be performed with or without contrast administration. 16,18,19,24,40,41 Although the initial experience with 4D MRA involved contrast administration, noncontrast-enhanced sequences such as 4D arterial spin-labeling MRA and 4D TOF have been developed, thus avoiding any potential complications from the use of contrast. 19,40,41 Multiple studies have shown that both contrast-enhanced and non-contrast-enhanced 4D MRA can quantify the degree of collateral circulation to an extent comparable with DSA, which is considered the gold standard.…”

Section: Four-dimensional Cta and Mramentioning

confidence: 99%

“…16,18,19,24,40,41 Although the initial experience with 4D MRA involved contrast administration, noncontrast-enhanced sequences such as 4D arterial spin-labeling MRA and 4D TOF have been developed, thus avoiding any potential complications from the use of contrast. 19,40,41 Multiple studies have shown that both contrast-enhanced and non-contrast-enhanced 4D MRA can quantify the degree of collateral circulation to an extent comparable with DSA, which is considered the gold standard. 16,18 Improved collateral flow surrounding an area of ischemia has been associated with better rates of recanalization, a lower incidence of hemorrhagic transformation, and improved clinical outcome after both thrombectomy and thrombolytic administration.…”

Section: Four-dimensional Cta and Mramentioning

confidence: 99%

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Advanced imaging in acute ischemic stroke

Kilburg¹,

McNally

Havenon

et al. 2017

FOC

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The evaluation and management of acute ischemic stroke has primarily relied on the use of conventional CT and MRI techniques as well as lumen imaging sequences such as CT angiography (CTA) and MR angiography (MRA). Several newer or less-established imaging modalities, including vessel wall MRI, transcranial Doppler ultrasonography, and 4D CTA and MRA, are being developed to complement conventional CT and MRI techniques. Vessel wall MRI provides high-resolution analysis of both extracranial and intracranial vasculature to help identify previously occult lesions or characteristics of lesions that may portend a worse natural history. Transcranial Doppler ultrasonography can be used in the acute setting as a minimally invasive way of identifying large vessel occlusions or monitoring the response to stroke treatment. It can also be used to assist in the workup for cryptogenic stroke or to diagnose a patent foramen ovale. Four-dimensional CTA and MRA provide a less invasive alternative to digital subtraction angiography to determine the extent of the clot burden and the degree of collateral blood flow in large vessel occlusions. Along with technological advances, these new imaging modalities are improving the diagnosis, workup, and management of acute ischemic stroke— roles that will continue to expand in the future.

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Section: Four-dimensional Cta and Mramentioning

confidence: 99%

Section: Four-dimensional Cta and Mramentioning

confidence: 99%

Advanced imaging in acute ischemic stroke

Kilburg¹,

McNally

Havenon

et al. 2017

FOC

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show abstract

“…Furthermore, ASL-MRA allows dynamic signal collection with appropriate timing delays after labeling to achieve 4D MRA with temporal information, which is not possible with TOF and was previously only possible with conventional angiography [14,[19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Synthesizing 4D Magnetic Resonance Angiography From 3D Time-of-Flight Using Deep Learning: A Feasibility Study

Wada,

Akatsu,

Ikenouchi

et al. 2024

Cureus

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Objective and background This study aimed to develop a deep convolutional neural network (DCNN) model capable of generating synthetic 4D magnetic resonance angiography (MRA) from 3D time-of-flight (TOF) images, allowing estimation of temporal changes in arterial flow. TOF MRA provides static information about arterial structures through maximum intensity projection (MIP) processing, but it does not capture the dynamic information of contrast agent circulation, which is lost during MIP processing. Considering the principles of TOF, it is hypothesized that dynamic information about arterial blood flow is latent within TOF signals. Although arterial spin labeling (ASL) can extract dynamic arterial information, ASL MRA has drawbacks, such as longer imaging times and lower spatial resolution than TOF MRA. This study's primary aim is to extend the utility of TOF MRA by training a machine-learning model on paired TOF and ASL data to extract latent dynamic information from TOF signals. Methods A DCNN combining a modified U-Net and a long-short-term memory (LSTM) network was trained on a dataset of 13 subjects (11 men and two women, aged 42-77 years) using paired 3D TOF MRA and 4D ASL MRA images. Subjects had no history of cerebral vessel occlusion or significant stenosis. The dataset was acquired using a 3T MRI system with a 32-channel head coil. Preprocessing involved resampling and intensity normalization of TOF and ASL images, followed by data augmentation and arterial mask generation. The model learned to extract flow information from TOF images and generate 8-phase 4D MRA images. The precision of flow estimation was evaluated using the coefficient of determination (R²) and Bland-Altman analysis. A board-certified neuroradiologist validated the quality of the images and the absence of significant stenosis in the major cerebral arteries. Results The generated 4D MRA images closely resembled the ground-truth ASL MRA data, with R² values of 0.92, 0.85, and 0.84 for the internal carotid artery (ICA), proximal middle cerebral artery (MCA), and distal MCA, respectively. Bland-Altman analysis revealed a systematic error of -0.06, with 95% agreement limits ranging from -0.18 to 0.12. Additionally, the model successfully identified flow abnormalities in a subject with left MCA stenosis, displaying a delayed peak and subsequent flattening distal to the stenosis, indicative of reduced blood flow. Visualization of the predicted arterial flow overlaid on the original TOF MRA images highlighted the spatial progression and dynamics of the flow. Conclusions The DCNN model effectively generated synthetic 4D MRA images from TOF images, demonstrating its potential to estimate temporal changes in arterial flow accurately. This non-invasive technique offers a promising alternative to conventional methods for visualizing and evaluating healthy and pathological flow dynamics. It has significant potential to improve the diagnosis and treatment of cerebrovascu...

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