Three-dimensional Magnetic Resonance Angiography Research Articles

Automatic detection method of intracranial aneurysms on maximum intensity projection images based on SE-CaraNet

Conventional maximum intensity projection (MIP) images tend to ignore some morphological features in the detection of intracranial aneurysms, resulting in missed detection and misdetection. To solve this problem, a new method for intracranial aneurysm detection based on omni-directional MIP image is proposed in this paper. Firstly, the three-dimensional magnetic resonance angiography (MRA) images were projected with the maximum density in all directions to obtain the MIP images. Then, the region of intracranial aneurysm was prepositioned by matching filter. Finally, the Squeeze and Excitation (SE) module was used to improve the CaraNet model. Excitation and the improved model were used to detect the predetermined location in the omni-directional MIP image to determine whether there was intracranial aneurysm. In this paper, 245 cases of images were collected to test the proposed method. The results showed that the accuracy and specificity of the proposed method could reach 93.75% and 93.86%, respectively, significantly improved the detection performance of intracranial aneurysms in MIP images.

ACCURACY OF SUSCEPTIBILITY WEIGHTED IMAGING AND 3D-TOF MRA IN DETECTION AND PRE-TREATMENT EVALUATION OF INTRACRANIAL DURAL ARTERIOVENOUS FISTULAS

Background: Dural arteriovenous fistulas (DAVFs) are abnormal connections between meningeal arteries and dural venous sinuses or cortical veins. A cerebral angiogram is the gold standard for diagnosing and treating DAVFs. Still, non-invasive techniques such as three-dimensional time-offlight magnetic resonance angiography (3D-TOF MRA) and susceptibility-weighted imaging (SWI) are also helpful in evaluating the location and severity of the fistulas, including cortical venous reflux (CVR) and cortical venous ectasia (CVE). This study aimed to compare the efficacy in detecting and pretreating DAVFs evaluating SWI and 3D-TOF MRA with cerebral angiography. Methods: The retrospective study included 35 patients with 41 DAVFs who underwent pre-treatment MR imaging and cerebral angiogram. The fistulous point at convexity and cavernous locations, arterial feeders, venous drainers, CVR, and CVE were evaluated. Results: SWI and 3D-TOF MRA showed high sensitivity and excellent specificity in detecting DAVFs Cognard II-IV at convexity location and high sensitivity in evaluating CVR. For DAVFs at cavernous sinus locations, arterial feeders and venous drainers were significantly identified in 3D-TOF MRA (p < 0.001). SWI exhibited superior sensitivity (87.5%) in detecting CVE at convexity locations (p < 0.001). Slow flow or low-grade fistulas in cavernous sinus locations (n = 2, 4.8%, Cognard I) were not identified using MR imaging. Conclusion: SWI and 3D-TOF MRA are helpful tools for evaluating high-flow DAVFs (Cognard II-IV). SWI is superior in detecting CVE in convexity locations but is limited in assessing the fistulous point in cavernous sinus locations. Thus, combining findings from both SWI and 3D-TOF MRA exhibited high accuracy in detecting and pretreating high-flow DAVFs.

Osteoid osteoma appearing after bony fracture in a girl with osteogenesis imperfecta.

Osteoid osteoma (OO) is a common, benign bone tumor. However, there are no case reports of OO associated with osteogenesis imperfecta (OI), or pathological fractures in OO. A 3-year-old girl with OI sustained a complete right tibial diaphyseal fracture. Bony fusion was completed after 4months of conservative therapy; nevertheless, 18months later spontaneous pain appeared at the fracture site, without any cause. Plain radiographs showed a newly apparent, rounded area of translucency 1cm in diameter, just overlapping the previous fracture. Images obtained using three-dimensional time-resolved contrast-enhanced magnetic resonance angiography showed strong central enhancement in the early phase, with an apparent nidus, suggesting the diagnosis of OO. Nineteen months after the first fracture, while skipping, the patient refractured her tibial diaphysis at the site of the previous fracture. This is a very rare case of OO, apparently co-existing with OI and leading to a bony fracture. In our case, the combination of bone fragility in OI and a recent fracture at the site of the OO may have caused the re-fracture.

Diagnostic performance of dynamic 3D magnetic resonance angiography in daily practice for the detection of intracranial arteriovenous shunts in patients with non-traumatic intracranial hemorrhage.

Identification of treatable causes of intracranial hemorrhage (ICH) such as intracranial arteriovenous shunt is crucial to prevent recurrence. However, diagnostic approaches vary considerably across centers, partly because of limited knowledge of the diagnostic performance of first-line vascular imaging techniques. We assessed the diagnostic performance of dynamic three-dimensional magnetic resonance angiography (dynamic 3D MRA) in daily practice to detect intracranial arteriovenous shunts in ICH patients against subsequent digital subtraction angiography (DSA) as reference standard. We reviewed all adult patients who underwent first-line dynamic 3D MRA and subsequent DSA for non-traumatic ICH between January 2016 and September 2021 in a tertiary center. Sensitivity, specificity, accuracy, positive and negative predictive values of dynamic 3D MRA for the detection of intracranial arteriovenous shunt were calculated with DSA as reference standard. Among 104 included patients, 29 (27.9%) had a DSA-confirmed arteriovenous shunt [19 pial arteriovenous malformations, 10 dural arteriovenous fistulae; median onset-to-DSA: 17 (IQR: 3-88) days]. The sensitivity and specificity of dynamic 3D MRA [median onset-to-dynamic 3D MRA: 14 (3-101) h] for the detection of intracranial arteriovenous shunt were 66% (95% CI: 48-83) and 91% (95% CI: 84-97), respectively. The corresponding accuracy, positive and negative predictive values were 84% (95% CI: 77-91), 73% (95% CI: 56-90), and 87% (95% CI: 80-95), respectively. This study suggests that although first-line evaluation with dynamic 3D MRA may be helpful for the detection of intracranial arteriovenous shunts in patients with ICH, additional vascular imaging work-up should not be withheld if dynamic 3D MRA is negative. Comparative prospective studies are needed to determine the best imaging strategy to diagnose arteriovenous shunts after non-traumatic ICH.

Red Blood Cell Membrane-Coated Ultrasmall NaGdF4 Nanoprobes for High-Resolution 3D Magnetic Resonance Angiography.

Enhanced angiography based on magnetic resonance imaging (MRI) has emerged as a noninvasive, robust, and high-resolution imaging technique for the clinical evaluation of vascular diseases. However, the effects of clinical Gd-chelating contrast agents are unsatisfactory for MRI contrast enhancement owing to their short blood half-life caused by rapid vascular extravasation, especially in microvessels. To address these issues, nanoprobes based on red blood cell membrane-coated ultrasmall NaGdF4 nanoparticles that exhibit much higher longitudinal molar relaxivity (r1) than the clinically used contrast agent gadolinium diethylenetriaminepentaacetic acid have been developed. Furthermore, the appropriate hydrodynamic diameter and stealth nature aid the nanoprobes to reside longer within the blood vessels without extravasation, thereby increasing the contrast between the blood vessels and surrounding tissues. Through probe-enhanced three-dimensional (3D) dynamic contrast-enhanced MR angiography, the main arteries and veins of the mouse were readily discernible, and even tiny vessels with sub-millimeter diameters could be clearly depicted. With this level of outstanding MR angiography performance, the embolization and recanalization processes of the carotid artery can be serially monitored with high imaging resolution using only a single injection. Additionally, the results of clearance studies and the toxicity tests further highlight the safety features of the nanoprobe. To summarize, the nanoprobes used in this study exhibit less extravascular leakage and a longer blood half-life, thus successfully overcoming the defects of the conventional low-molecular-weight Gd-based contrast agents and demonstrating their potential usefulness in enhanced MR angiography.

Automated Segmentation of Trigeminal Nerve and Cerebrovasculature in MR-Angiography Images by Deep Learning.

Trigeminal neuralgia caused by paroxysmal and severe pain in the distribution of the trigeminal nerve is a rare chronic pain disorder. It is generally accepted that compression of the trigeminal root entry zone by vascular structures is the major cause of primary trigeminal neuralgia, and vascular decompression is the prior choice in neurosurgical treatment. Therefore, accurate preoperative modeling/segmentation/visualization of trigeminal nerve and its surrounding cerebrovascular is important to surgical planning. In this paper, we propose an automated method to segment trigeminal nerve and its surrounding cerebrovascular in the root entry zone, and to further reconstruct and visual these anatomical structures in three-dimensional (3D) Magnetic Resonance Angiography (MRA). The proposed method contains a two-stage neural network. Firstly, a preliminary confidence map of different anatomical structures is produced by a coarse segmentation stage. Secondly, a refinement segmentation stage is proposed to refine and optimize the coarse segmentation map. To model the spatial and morphological relationship between trigeminal nerve and cerebrovascular structures, the proposed network detects the trigeminal nerve, cerebrovasculature, and brainstem simultaneously. The method has been evaluated on a dataset including 50 MRA volumes, and the experimental results show the state-of-the-art performance of the proposed method with an average Dice similarity coefficient, Hausdorff distance, and average surface distance error of 0.8645, 0.2414, and 0.4296 on multi-tissue segmentation, respectively.

MR angiography-planned prostatic artery embolization for benign prostatic hyperplasia: single-center retrospective study in 56 patients

We aimed to evaluate the advantages of magnetic resonance angiography (MRA)-planned prostatic artery embolization (PAE) for benign prostatic hyperplasia (BPH).In this retrospective study, MRAs of 56 patients (mean age, 67.23±7.73 years; age range, 47-82 years) who underwent PAE between 2017 and 2018 were evaluated. For inclusion, full information about procedure time and radiation values must have been available. To identify prostatic artery (PA) origin, three-dimensional MRA reconstruction with maximum intensity projection was conducted in every patient. In total, 33 patients completed clinical and imaging follow-up and were included in clinical evaluation.There were 131 PAs with a second PA in 19 pelvic sides. PA origin was correctly identified via MRA in 108 of 131 PAs (82.44%). In patients in which MRA allowed a PA analysis, a significant reduction of the fluoroscopy time (-27.0%, p = 0.028) and of the dose area product (-38.0%, p = 0.003) was detected versus those with no PA analysis prior to PAE. Intervention time was reduced by 13.2%, (p = 0.25). Mean fluoroscopy time was 30.1 min, mean dose area product 27,749 µGy•m2, and mean entrance dose 1553 mGy. Technical success was achieved in all 56 patients (100.0%); all patients were embolized on both pelvic sides. The evaluated data documented a significant reduction in IPSS (p < 0.001; mean 9.67 points).MRA prior to PAE allowed the identification of PA in 82.44% of the cases. MRA-planned PAE is an effective treatment for patients with BPH.

Inter- and Intra-Rater Reliability of Individual Cerebral Blood Flow Measured by Quantitative Vessel-Flow Phase-Contrast MRI.

Vessel flow quantification by two-dimensional (2D) phase-contrast magnetic resonance imaging (PC-MRI) using a three-dimensional (3D) magnetic resonance angiography (MRA) model to measure cerebral blood flow has unclear analytical reliability. The present study aimed to determine the inter- and intra-rater reliability of quantitative vessel-flow PC-MRI and potential factors influencing its consistency. We prospectively recruited 30 Asian participants (aged 20–90 years; 16 women; 22 healthy and 8 stroke patients) for performing 1.5-T MR equipped with a head coil. Each participant was first scanned for time-of-flight magnetic resonance angiography (TOF-MRA) images for localization of intracranial arteries. The 2D PC-MRI for each cerebral artery (total 13 arteries in fixed order) was performed twice by two well-trained operators in optimal position. Using the same 3D MRA as a map and facilitated with the non-invasive optimal vessel analysis (NOVA) system, each scan was taken on a plane perpendicular to the target artery. Two consecutive full 13-artery scans were performed at least 15 min apart after participants were removed from the scanner table and then repositioned. A total of four PC flow images obtained from each target artery were transmitted to a workstation facilitated with the NOVA system. Flow data were calculated semi-automatically by the NOVA system after a few simple steps. Two-way mixed-effect models and standard errors of measurements were used. In 13 cerebral arteries, repeatability, using the intra-rater estimate expressed as the average-measures intraclass correlation coefficient, ranged from 0.641 to 0.954, and reproducibility, using the inter-rater estimate, ranged from 0.672 to 0.977. Except in the middle cerebral artery and the distal segment of the anterior cerebral artery, repeatability and reproducibility were excellent (intraclass correlation coefficient exceeded 0.8). The use of quantitative vessel-flow PC-MRI is a precise means to measure blood flow in most target cerebral arteries. This was evidenced by inter-rater and intra-rater correlations that were good/excellent, indicating good reproducibility and repeatability.

Diagnostic Accuracy of Three-Dimensional Whole-Heart Magnetic Resonance Angiography to Detect Coronary Artery Disease with Invasive Coronary Angiography as a Reference: A Meta-Analysis

Objective: We aimed to evaluate the diagnostic performance of three-dimensional whole-heart magnetic resonance coronary angiography (MRCA) in detecting coronary artery disease (CAD) with invasive coronary angiography as the reference standard. Methods: We searched PubMed and Embase for studies evaluating the diagnostic performance of three-dimensional whole-heart MRCA for the diagnosis of CAD with invasive coronary angiography as the reference standard. The bivariate mixed-effects regression model was applied to synthesize available data. The clinical utility of whole-heart MRCA was calculated by the posttest probability based on Bayes’s theorem. Results: Eighteen studies were included, of which 16 provided data at the artery level. Patient-based analysis revealed a pooled sensitivity of 0.90 (95% confidence interval [CI] 0.87–0.93) and specificity of 0.79 (95% CI 0.73–0.84), while the pooled estimates were 0.86 (95% CI 0.82–0.89) and 0.89 (95% CI 0.84–0.92), respectively, at the artery level. The areas under the summary receiver operating characteristic curve were 0.93 (95% CI 0.90–0.95) and 0.92 (95% CI 0.90–0.94) at the patient and artery levels, respectively. With a pretest probability of 50%, the patients’ posttest probabilities of CAD were 81% for positive results and 11% for negative results. Conclusions: Whole-heart MRCA can be an alternative noninvasive method for diagnosis and assessment of CAD.

Comparison of axial and coronal acquisitions by non-contrast-enhanced renal 3D MR angiography using flow-in time-spatial labeling inversion pulse

ObjectiveWe evaluated image quality differences between axial and coronal non-contrast-enhanced renal three-dimensional (3D) magnetic resonance angiography (MRA) acquisitions, using time-spatial labeling inversion pulse (Time-SLIP) with flow-in balanced steady-state free precession (bSSFP).Materials and methodsAxial and coronal images were acquired in 128 subjects using non-contrast-enhanced 3D-MRA with Time-SLIP flow-in bSSFP on a clinical 1.5-T MRI system. Visualization of source and maximum intensity projection (MIP) images of renal arteries were compared between the axial and coronal acquisitions using a four-point scale. For quantitative analysis, vessel-to-background contrast ratios of aorta and renal arteries were calculated.ResultsBoth acquisitions yielded similarly excellent quality. In source image evaluation, coronal acquisitions showed significantly more motion degradation (p < 0.01) than did axial acquisitions. In MIP image evaluation, coronal acquisitions yielded superior image quality, less motion degradation, and better visualization of the number of renal branches than did axial acquisition. The renal artery to background signal contrast was greater in coronal than in axial acquisitions (p < 0.01).ConclusionCoronal acquisition provides superior contrast between the renal arteries and background and allows more persistent visualization than axial acquisitions in non-contrast-enhanced MRA using flow-in bSSFP with Time-SLIP. First-line screening of renal non-contrast-enhanced MRA should involve coronal acquisition.

Consistency of neurovascular relationship between multimodal image fusion 3D reconstruction and intraoperative findings of microvascular decompression for primary trigeminal neuralgia

Objective To explore the consistency of neurovascular relationships between multimodal image fusion 3D reconstruction and intraoperative findings in microvascular decompression (MVD) for primary trigeminal neuralgia (PTN). Methods A retrospective analysis was conducted on the clinical data of 50 PTN patients treated with MVD at Department of Neurosurgery, Qingdao University Hospital from January to November 2018. All subjects underwent three-dimensional time-flying magnetic resonance angiography (3D-TOF-MRA) and three-dimensional cyclic phase steady-state acquisition rapid imaging (3D-FIESTA) sequences. Then, the 3D-slicer software was used to reconstruct the multimodal fusion 3D image. Multimodal image fusion 3D reconstruction images and surgical video were analyzed to determine the offending vessels responsible for trigeminal neuralgia. At the same time, the direction of compression, compression site and compression degree of the trigeminal nerve were analyzed. Kappa consistency test method was used to judge the consistency of the two approaches above. Results With MVD set as the standard, the accuracies of multimodal image fusion 3D reconstruction images in determining the offending vessels, direction of compression, compression site and the degree of compression were 92.0% (46/50), 92.0% (46/50), 96.0% (48/50) and 58.0% (29/50), respectively. Multimodal image fusion 3D reconstruction images and MVD showed high consistency in judging offending vessels, compression direction and compression position (Kappa values: 0.729, 0.903 and 0.955 respectively, all P<0.001). However, the consistency was poor in judging the degree of compression of offending vessels to the trigeminal nerve (Kappa value=0.227, P=0.002). The degree of compression was higher in intraoperative findings of MVD than that revealed by multimodal image fusion three-dimensional reconstruction (mean values: 2.57 and 1.58 respectively, Z=-4.499, P<0.001). Conclusions Preoperative multi-modal image fusion 3D reconstruction could help accurately determine the offending vessel, compression direction and compression position of PTN, which seems highly consistent with intraoperative findings of MVD. Preliminary speculation could be used as one of the methods facilitating preoperative diagnosis. Key words: Trigeminal neuralgia; Multimodal image fusion; Microvascular decompression; Neurovascular relationship; Computer-aided diagnosis

Three-Dimensional Free-Breathing Whole-Heart Coronary Magnetic Resonance Angiography at 1.5 T: Gadobutrol-Enhanced Gradient-Echo Acquisition Sequence Versus Non-Contrast-Enhanced Steady-State Free Precession Sequence.

The objective of this study was to compare gadobutrol-enhanced gradient-echo sequence (GRE) acquisition with T2-prepared non-contrast-enhanced steady-state free precession (SSFP) in coronary magnetic resonance angiography at 1.5 T. Twenty-one subjects successfully completed GRE and SSFP acquisition. Signal-to-noise ratio (SNR), contrast-to-noise ratio, image quality, sharpness, visibility, length, and lumen diameter of vessels were analyzed by 2 experienced radiologists. The SNR at whole left circumflex artery, left main artery, and proximal left descending artery (LAD) was significantly higher in SSFP acquisition (P < 0.05). The SNR of distal LAD was slightly higher in GRE acquisition (P < 0.05). The contrast-to-noise ratio at distal LAD, proximal and distal RCA were significantly higher with GRE acquisition (P < 0.05). Double-dose gadobutrol-enhanced GRE and unenhanced SSFP coronary magnetic resonance angiography at 1.5 T have their own characteristics, and the combined use of the 2 methods may be taken into consideration.

The value of 3D-TOF-MRA and 3D-FIESTA fusion three-dimensional images in judgment of offending vessel in primary trigeminal neuralgia

Objective To investigate the value of three-dimensional time-flying magnetic resonance angiography (3D-TOF-MRA) and three-dimensional fast imaging employing steady-state acquisition sequence (3D-FIESTA) fusion three-dimensional image in identification of offending vessels of primary trigeminal neuralgia (PTN). Methods A total of 48 patients with PTN who underwent microvascular decompression (MVD) from January 2016 to June 2019 at Department of Neurosurgery, Affiliated Hospital of Qingdao University were retrospectively enrolled into this study. All patients underwent 3D-TOF-MRA and 3D-FIESTA sequence examinations before operation. The 3D-slicer software was used to fuse 3D-TOF-MRA and 3D-FIESTA sequence images and conduct three-dimensional reconstruction. Using MVD as a standard, 3D-TOF-MRA, 3D-FIESTA and fused images were evaluated to determine the offending vessels and their compressive degree on the nerves. Results In MVD, except for 1 patient who had no offending vessel, the other 47 patients had clear offending vessels. The offending vessels were merely arteries in 40 cases, veins in 2, and both arteries and veins in 5. The 3D-TOF-MRA results showed that 5 patients had no offending vessels, and the remaining 43 patients had arteries as offending vessels. The 3D-FIESTA showed that 4 cases had no offending vessels; the offending vessels were arteries in 36 cases, veins in 3 cases, and both arteries and veins in 5 cases. The fused images showed that there were 2 cases without offending vessels; the offending vessels were arteries in 39 cases, veins in 2 cases, and both arteries and veins in 5 cases. Using the MVD as the standard, the accuracy of 3D-TOF-MRA, 3D-FIEST and fusion 3D images for determining the presence/absence offending vessels was 91.7% (44/48), 93.8% (45/48) and 97.9%(45/48), respectively. The accuracy of correct identification of offending vessels by 3D-TOF-MRA, 3D-FIEST and fused images was 54.2% (26/48), 89.6% (43/48) and 93.8% (45/48), respectively. Compared with intraoperative findings, those 3 types of images commonly showed lighter degree of nerve compression, and the differences were statistically significant (all P<0.05). Conclusion Compared with 3D-TOF-MRA and 3D-FIESTA single sequences, the fused images seem to be more accurate in identification of the offending vessels of PTN, which, however, is still associated with underestimation of the nerve compression degree. Key words: Trigeminal neuralgia; Offending vessel; Three-dimensional time-of-flight magnetic resonance angiography; Three-dimensional fast imaging employing steady-state acquisition; Microva-scular decompression

Correcting versus resolving respiratory motion in free-breathing whole-heart MRA: a comparison in patients with thoracic aortic disease

BackgroundWhole-heart magnetic resonance angiography (MRA) requires sophisticated methods accounting for respiratory motion. Our purpose was to evaluate the image quality of compressed sensing-based respiratory motion-resolved three-dimensional (3D) whole-heart MRA compared with self-navigated motion-corrected whole-heart MRA in patients with known thoracic aorta dilation.MethodsTwenty-five patients were prospectively enrolled in this ethically approved study. Whole-heart 1.5-T MRA was acquired using a prototype 3D radial steady-state free-precession free-breathing sequence. The same data were reconstructed with a one-dimensional motion-correction algorithm (1D-MCA) and an extradimensional golden-angle radial sparse parallel reconstruction (XD-GRASP). Subjective image quality was scored and objective image quality was quantified (signal intensity ratio, SIR; vessel sharpness). Wilcoxon, McNemar, and paired t tests were used.ResultsSubjective image quality was significantly higher using XD-GRASP compared to 1D-MCA (median 4.5, interquartile range 4.5–5.0 versus 4.0 [2.25–4.75]; p < 0.001), as well as signal homogeneity (3.0 [3.0–3.0] versus 2.0 [2.0–3.0]; p = 0.003), and image sharpness (3.0 [2.0–3.0] vs 2.0 [1.25–3.0]; p < 0.001). SIR with the 1D-MCA and XD-GRASP was 6.1 ± 3.9 versus 7.4 ± 2.5, respectively (p < 0.001); while signal homogeneity was 274.2 ± 265.0 versus 199.8 ± 67.2 (p = 0.129). XD-GRASP provided a higher vessel sharpness (45.3 ± 10.7 versus 40.6 ± 101, p = 0.025).ConclusionsXD-GRASP-based motion-resolved reconstruction of free-breathing 3D whole-heart MRA datasets provides improved image contrast, sharpness, and signal homogeneity and seems to be a promising technique that overcomes some of the limitations of motion correction or respiratory navigator gating.

The diagnostic performance of three-dimensional contrast-enhanced magnetic resonance angiography in demonstrating renal vasculature in patients with suspected renovascular hypertension

Amac: Calismamizin amaci, digital subtraction angiography (DSA) teknigini referans metod alarak, uc boyutlu kontrastli manyetik rezonans anjiyografi (3D CE-MRA) tekniginin, renal arter stenozu (RAS) tanisindaki ve segmental ve aksesuar renal arter goruntulemesindeki degerini saptamak idi. Gerec ve Yontem: Yirmi bes hastaya 3D CE-MRA ve DSA tetkikleri uygulandi. CE-MRA tekniginin RAS tanisindaki sensitivite, spesifisite ve pozitif ve negatif kestirim degerleri ile teknigin segmental ve aksesuar renal arter goruntulemedeki sensitivite degerleri hesaplandi. Bulgular: RAS tanisinda CE-MRA tekniginin sensitivite, spesifisite, pozitif ve negatif kestirim degerleri, ayni sira ile; %100, %97,8, %87,5, ve %100 olarak hesaplandi. Teknigin segmental ve aksesuar renal arter goruntulemedeki sensitivite degerlerinin, ayni sira ile; %58 ve %91,7 oldugu saptandi. Sonuc: 3D CE-MRA tekniginin, sadece renal arter stenozu tanisinda degil, aksesuar arterlerin goruntulemesinde de guvenilir oldugu saptandi. Ancak calismamizin sonuclarina gore, teknigin segmental arter goruntulemesindeki degeri sinirlidir.

Segmentation-Based Blood Flow Parameter Refinement in Cerebrovascular Structures Using 4-D Arterial Spin Labeling MRA.

Cerebrovascular diseases are one of the main global causes of death and disability in the adult population. The preferred imaging modality for the diagnostic routine is digital subtraction angiography, an invasive modality. Time-resolved three-dimensional arterial spin labeling magnetic resonance angiography (4D ASL MRA) is an alternative non-invasive modality, which captures morphological and blood flow data of the cerebrovascular system, with high spatial and temporal resolution. This work proposes advanced medical image processing methods that extract the anatomical and hemodynamic information contained in 4D ASL MRA datasets. A previously published segmentation method, which uses blood flow data to improve its accuracy, is extended to estimate blood flow parameters by fitting a mathematical model to the measured vascular signal. The estimated values are then refined using regression techniques within the cerebrovascular segmentation. The proposed method was evaluated using fifteen 4D ASL MRA phantoms, with ground-truth morphological and hemodynamic data, fifteen 4D ASL MRA datasets acquired from healthy volunteers, and two 4D ASL MRA datasets from patients with a stenosis. The proposed method reached an average Dice similarity coefficient of 0.957 and 0.938in the phantom and real dataset segmentation evaluations, respectively. The estimated blood flow parameter values are more similar to the ground-truth values after the refinement step, when using phantoms. A qualitative analysis showed that the refined blood flow estimation is more realistic compared to the raw hemodynamic parameters. The proposed method can provide accurate segmentations and blood flow parameter estimations in the cerebrovascular system using 4D ASL MRA datasets. The information obtained with the proposed method can help clinicians and researchers to study the cerebrovascular system non-invasively.

Invited commentary

Given that the superficial femoral and popliteal arteries look fairly straight when a patient is lying supine on a fluoroscopy table, the temptation to view this arterial segment as one long biomechanical continuum seems somewhat understandable. However, Poulson et al have adeptly reminded us that this is not necessarily the case. With the use of an innovative system of nitinol markers deployed along the course of cadaveric femoral and popliteal arteries, these authors have depicted the significant deformations that take place during the course of normal daily activities. Poulson et al are not the first to demonstrate that the femoropopliteal arteries shorten, elongate, bend, buckle, and twist. Numerous prior researchers have done that using three-dimensional magnetic resonance angiography, three-dimensional computed tomography angiography, and fluoroscopy, in combination with finite-element analysis.1Ansari F. Pack L.K. Brooks S.S. Morrison T.M. Designed considerations for studies of the biomechanical environment of the femoropopliteal arteries.J Vasc Surg. 2013; 58: 804-813Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar, 2Ghriallais R.N. Bruzzi M. Effects of knee flexion on the femoropopliteal artery: a computation of study.Med Eng Phys. 2013; 35: 1620-1628Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar, 3Fortier A. Gullapalli V. Mirshams R.A. Review of biomechanical studies of arteries and their effect on stent performance.IJC Heart Vessels. 2014; 4: 12-18Abstract Full Text Full Text PDF Scopus (52) Google Scholar However, the current study does emphasize just how inhomogeneous and severe these strains can be, particularly at sites where arteries are fixed to surrounding structures, such as descending geniculate branches, the adductor canal, and popliteal bifurcation. Although the femoropopliteal arteries in the current study came from older donors, the arteries were relatively free of atherosclerosis. It would be quite interesting to see the effect of calcification, atherosclerotic thickening, and the presence of one or even multiple overlapping stents on the motion of these arteries. Manufacturers have made some progress with regard to stents specifically designed for the femoropopliteal environment. However, we also need to advance our clinical knowledge (eg, the correct stent for the correct segment, the optimal degree of overlap, if any), because there is much room for improvement in the way we use these stents. The opinions or views expressed in this commentary are those of the authors and do not necessarily reflect the opinions or recommendations of the Journal of Vascular Surgery or the Society for Vascular Surgery. Limb flexion-induced axial compression and bending in human femoropopliteal artery segmentsJournal of Vascular SurgeryVol. 67Issue 2PreviewHigh failure rates of femoropopliteal artery (FPA) interventions are often attributed in part to severe mechanical deformations that occur with limb movement. Axial compression and bending of the FPA likely play significant roles in FPA disease development and reconstruction failure, but these deformations are poorly characterized. The goal of this study was to quantify axial compression and bending of human FPAs that are placed in positions commonly assumed during the normal course of daily activities. Full-Text PDF Open Archive

Coronary artery assessment using self-navigated free-breathing radial whole-heart magnetic resonance angiography in patients with congenital heart disease

To evaluate a self-navigated free-breathing three-dimensional (SNFB3D) radial whole-heart MRA technique for assessment of main coronary arteries (CAs) and side branches in patients with congenital heart disease (CHD). SNFB3D-MRA datasets of 109 patients (20.1±11.8 years) were included. Three readers assessed the depiction of CA segments, diagnostic confidence in determining CA dominance, overall image quality and the ability to freeze cardiac and respiratory motion. Vessel sharpness was quantitatively measured. The percentages of cases with excellent CA depiction were as follows (mean score): left main, 92.6 % (1.92); left anterior descending (LAD), 88.3 % (1.88); right (RCA), 87.8 % (1.85); left circumflex, 82.8 % (1.82); posterior descending, 50.2 % (1.50) and first diagonal, 39.8 % (1.39). High diagnostic confidence for the assessment of CA dominance was achieved in 56.2 % of MRA examinations (mean score, 1.56). Cardiac motion freezing (mean score, 2.18; Pearson's r=0.73, P<0.029) affected image quality more than respiratory motion freezing (mean score, 2.20; r=0.58, P<0.029). Mean quantitative vessel sharpness of the internal thoracic artery, RCA and LAD were 53.1, 52.5 and 48.7 %, respectively. Most SNFB3D-MRA examinations allow for excellent depiction of the main CAs in young CHD patients; visualisation of side branches remains limited. • Self-navigated free-breathing three-dimensional magnetic resonance angiography (SNFB3D-MRA) sufficiently visualises coronary arteries (CAs). • Depiction of main CAs in patients with congenital heart disease is excellent. • Visualisation of CA side branches using SNFB3D-MRA is limited. • SNFB3D-MRA image quality is especially correlated to cardiac motion freezing ability.

Are the anomalous vertebral arteries more hypoplastic?: retrospective linear mixed model approach

BackgroundSmall or hypoplastic vertebral artery (VA) is one of the risk factor for posterior circulation stroke. We assess whether various types of VA anomaly contribute to its diameter.MethodsWe screened 238 patients who underwent neck CT and MR angiography within 1 month. A V1 anomaly was defined as the abnormal origin of the VA on a three-dimensional MR angiography and a V2 anomaly was defined as the VA not passing through the 6th cervical transverse foramen (TF) on an axial CT image. A linear mixed model was used to evaluate the determinants of VA size.ResultsAmong participants, 24 (10.1%) subjects exhibited an anomalous VA and, of the 476 VAs examined, 11 (2.3%) had an aortic origin and 27 (5.7%) had an abnormal entrance into the C6 TF. Presence of the V1 anomaly was positively associated with the V2 anomaly (P for chi-square < 0.001) and a linear mixed model revealed that being male (0.2 mm larger, P = 0.015), having a right VA anomaly (0.3 mm smaller, P < 0.001), having a V1 anomaly (0.9 mm smaller, P < 0.001), and having a V2 anomaly (0.7 mm smaller, P < 0.001) were significant predictor of VA diameter.ConclusionThe diameters of VAs with an anomalous aortic origin or an abnormal entrance of the TF were significantly smaller than those of normal VAs. These findings suggest that anomalies of the VA detected in 3-dimensional CTA or MRA may be clues for vertebral artery hypoplasia.

Fast three-dimensional whole-body post-mortem magnetic resonance angiography

Abstract Purpose The goal of this study was to perform whole-body post-mortem magnetic resonance (PMMR) angiography with imaging quality comparable to that of post-mortem computed tomography (PMCT) angiography. Methods After contrast medium injection into the arterial and venous vascular system of seven human corpses PMMR was performed using a fast three-dimensional T1 weighted spoiled gradient-echo sequence, followed by PMCT imaging. The contrast medium volumes inside the descending aorta and inside the inferior vena cava were measured both on PMMR and on PMCT images by means of image segmentation. Visualization quality of arterial and venous vessels as a function of contrast filling was scored according to a four-point scale and compared using the paired Wilcoxon signed rank test. Results The contrast medium volume in the descending aorta decreased 12% on average from PMMR to PMCT angiography, while the contrast medium volume in the inferior vena cava increased by 11% on average. A total of 410 vessels were analyzed. Scores for all vessels were statistically significantly smaller for the PMMR angiography when compared to PMCT angiography (p = 0.01). No statistically significant differences were found for the subgroups of large vessels (p = 0.21), for the head and neck (p = 0.16) or the abdomen (p = 0.83) as well as for the thorax when the coronary arteries were left out (p = 0.23). Conclusions This study demonstrates that immediate image acquisition after contrast injection and rapid 3D whole-body image acquisition offers good image quality in PMMR angiography with a vascular contrast comparable to PMCT angiography.