Anatomical information of the lenticulostriate arteries on high-resolution 3D-TOF MRA at 3 T: comparison with 3D-DSA

PURPOSE

As the lenticulostriate arteries (LSAs) perfuse neurologically important areas, it is necessary to accurately assess the origin and number of the LSAs before surgery. Although three-dimensional time-of-flight MR angiography (3D-TOF MRA) is a non-invasive procedure, it requires high-resolution (HR) images to depict the LSAs with a small diameter. Therefore, we performed 3D-TOF MRA with the maximum HR (HR-MRA) using a 3 T scanner to examine whether a good depiction of the LSAs, equivalent to that of digital subtraction angiography (DSA), could be obtained.

METHODS

Our study group comprised 16 consecutive patients who underwent HR-MRA and 3D-DSA. In both studies, we evaluated the localization of the origin from M1, M2, or A1 segments, their number of stems, and depiction.

RESULTS

There was no significant difference in the visualization of the LSAs between HR-MRA and 3D-DSA (P values; M1, M2, and A1 = 0.39, 0.69, and 0.69, respectively), and both the number of stems and the localization of the origin of the LSAs corresponded between the two examinations.

CONCLUSION

HR-MRA at 3 T can depict the LSA well. It reveals the number of the LSA stems and the LSA origin comparatively with DSA.

Unilateral cerebral arterial tortuosity: Associated with aneurysm occurrence, but potentially inversely associated with aneurysm rupture

PURPOSE

To investigate the association of tortuosity of the main cerebral arteries with intracranial aneurysm (IA) occurrence and rupture. To investigate the relationship between arterial tortuosity and aneurysm morphology as well as conventional risk factors of vascular diseases.

METHODS

Three subject groups were analyzed in this study: Patients with ruptured IAs, patients with unruptured IAs, and healthy subjects. The groups were matched by sex and age using tendency score matching. Their intracranial magnetic resonance angiography (MRA) images were collected retrospectively. The intracranial arterial structures were segmented from the MRA images. Arterial tortuosity was measured and statistically compared between the different subject groups and different vessels. Correlation analysis was conducted between arterial tortuosity and clinical risk factors as well as aneurysm morphology.

RESULTS

120 patients were included in the study (average age: 67.5 years; 60% female), 40 for each group after matching. The tortuosity of the aneurysm-bearing artery was significantly greater than that of the contralateral artery in both the ruptured and unruptured IA groups (p < 0.001). There was no significant association between clinical risk factors (history of hypertension, hyperlipidemia, diabetes, smoking, and alcohol use) and arterial tortuosity. There were significant negative correlations between aneurysm-bearing artery tortuosity and aneurysm morphological features such as maximal diameter (p = 0.0011), neck diameter (p < 0.0001), maximum height (p = 0.0024), and size ratio (p = 0.0269).

CONCLUSION

The occurrence of cerebral aneurysms correlates to increased unilateral arterial tortuosity, but the risk of aneurysm enlargement/rupturing decreases with greater arterial tortuosity. Abnormal tortuosity may be congenital as tortuosity has no clear connection with acquired common risk factors of vascular diseases.

MR Angiography for Aortic Diseases

Aortic pathologic conditions represent diverse disorders, including aortic aneurysm, acute aortic syndrome, traumatic aortic injury, and atherosclerosis. Given the nonspecific clinical features, noninvasive imaging is critical in screening, diagnosis, management, and posttherapeutic surveillance. Of the commonly used imaging modalities, including ultrasound, computed tomography, and MR imaging, the final choice often depends on a combination of factors: acuity of clinical presentation, suspected underlying diagnosis, and institutional practice. Further research is needed to identify the potential clinical role and define appropriate use criteria for advanced MR applications such as four-dimenional flow to manage patients with aortic pathologic conditions.

Malignant solitary fibrous tumor of the floor of the mouth in a 71-year-old male: A case report

Solitary fibrous tumors are rare mesenchymal tumors originally described in the pleura that infrequently metastasize. We present a 71-year-old male complaining of hemoptysis and a mass with the characteristic appearance of a hemangioma in the floor of the mouth. The mass had nonspecific imaging features on CT and MRI. After unsuccessful fine needle aspiration, surgical excision and biopsy with histological analysis revealed a solitary fibrous tumor, high risk variant. CT Imaging and lymph node biopsy showed gross total resection and no metastatic adenopathy. Given the high risk for malignancy, the patient received adjuvant radiation without subsequent clinical or imaging signs of recurrence. This case report demonstrates the presentation of this rare entity that can often be confused with other tumors in this region, given its nonspecific clinical and imaging findings.

Development and practical evaluation of a saturation effect learning simulator for inflow magnetic resonance angiography

The quality of visualization in inflow magnetic resonance angiography (MRA) depends highly on the excitation state of the longitudinal magnetization obtained using specified imaging parameters. In addition, signal intensity changes controlled by the preparation pulse-such as inversion recovery (IR) and saturation recovery (SR)-can potentially be used as quantitative physiological values. Although having practitioners understand these relationships both qualitatively and quantitatively is important, handling clinical equipment in practical learning or experiments involves limited opportunities. The simulator corresponds to a three-dimensional spoiled gradient echo sequence and allows users to freely input multiple virtual excitation effects in space and time. The purpose of this study was to quantitatively evaluate the agreement between the measured MRAs obtained in flow phantom tests and virtual MRAs simulated under similar conditions. We imaged two vascular flow phantoms on a 3.0 T MR system using three-dimensional (3D) time-of-flight (TOF) MRA and 3D inversion recovery tissue signal suppression (IR-suppression) MRA protocols. We evaluated quantitative values for consistency between the measured and virtual MRAs images with matched spatial resolution. Then we assessed the coincidence by reformatting maximum-intensity projection images with 1 mm isotropic pixels, with it ranging from 89.6 to 92.0% and 89.1 to 92.9% for TOF MRA and IR-suppression MRA, respectively. These results may be useful as a reference index for the theoretical study of MRA images by practitioners, for complementary validation by phantom testing, or for the development of MRI-related simulators.

Intensity of arterial structure acquired by Silent MRA estimates cerebral blood flow

BACKGROUND

Cerebral blood flow (CBF) and the morphology of the cerebral arteries are important for characterizing cerebrovascular disease. Silent magnetic resonance angiography (Silent MRA) is a MRA technique focusing on arterial structural delineation. This study was conducted to investigate the correlation between Silent MRA and CBF quantification, which has not yet been reported.

METHODS

Both the Silent MRA and time-of-flight magnetic resonance angiography scans were applied in seventeen healthy participants to acquire the arterial structure and to find arterial intensities. Phase-contrast MRA (PC-MRA) was then used to perform the quantitative CBF measurement of 13 cerebral arteries. Due to different dataset baseline signal level of Silent MRA, the signal intensities of the selected 13 cerebral arteries were normalized to the selected ROIs of bilateral internal carotid arteries. The normalized signal intensities were used to determine the relationship between Silent MRA and CBF.

RESULTS

The image intensity distribution of arterial regions generated by Silent MRA showed similar laminar shape as the phase distribution by PC-MRA (correlation coefficient > 0.62). Moreover, in both the results of individual and group-leveled analysis, the intensity value of arterial regions by Silent MRA showed positively correlation with the CBF by PC-MRA. The coefficient of determination (R²) of individual trends ranged from 0.242 to 0.956, and the R² of group-leveled result was 0.550.

CONCLUSIONS

This study demonstrates that Silent MRA provides valuable CBF information despite arterial structure, rendering it a potential tool for screening for cerebrovascular disease.

Magnetic Resonance Angiography and Multidetector CT Angiography in the Diagnosis of Takayasu's Arteritis: Assessment of Disease Extent and Correlation with Disease Activity

BACKGROUND

Takayasu's arteritis (TA) is a large vessel vasculitis with diverse clinical presentations and arterial vascular bed involvement. It is characterized by chronic, nonspecific inflammation of all layers of the vessel wall, which results in stenosis, occlusion, dilatation, or aneurysm formation in the involved blood vessels.

METHODS

The study included 36 patients of TA. All patients fulfilled the modified Ishikawa's diagnostic criteria for TA. All patients were evaluated for clinical presentation, angiographic findings, and severity of the disease. The disease activity was assessed based on Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) and also by CT angiography (CTA)/Magnetic resonance angiography (MRA) imaging. The angiographic types were classified based on the International TA Conference in Tokyo, 1994 angiographic classification.

RESULTS

A total of 36 patients were included in the study, 86% were females and a mean age of 21.6 years. Hypertension (78%) was the most common clinical presentation. Type V was the most common angiographic type (42%), followed by type III (25%), type IV (14%), type IIb (11%), type I (5%) and type IIa (3%). Among the aortic arch branches, the left subclavian artery (50%), right subclavian artery (38.8%), left vertebral artery (33.3%) and left common carotid artery (27.7%) were the most commonly involved arteries. Disease activity based on CT/MR imaging showed a significant statistical correlation with elevated ESR and positive CRP (p < 0.0001). Mediastinal lymphadenopathy was seen in 21 patients, out of which 11 had active disease. However, no significant correlation was found between mediastinal lymphadenopathy and disease activity.

CONCLUSIONS

TA presents varied symptomatology and differing vascular involvement. CT/MR angiography is effective in diagnosis and accurately predicted the active stage of the disease.

Electrophysiological and neuroimaging findings in a patient who developed visual loss after attempted suicide by hanging

PURPOSE

To report the electrophysiological and neuroimaging findings in a patient who developed visual loss after attempted suicide by hanging.

METHODS

A 45-year-old male presented with bilateral visual loss and difficulty in walking following a suicide attempt by hanging six months ago. He underwent a complete ophthalmologic examination, posterior segment optical coherence tomography (OCT), various electrophysiological tests and neuroimaging.

RESULTS

His bilateral best-corrected visual acuity was logMAR 1.08. Intraocular pressures and ocular examination were normal except for bilateral temporal disk pallor. Macular OCT showed bilateral ganglion cell layer-inner plexiform layer complex thinning. Electroretinogram showed reduced b/a wave amplitude ratio in all the dark- and light-adapted International Society for Clinical Electrophysiology of Vision protocols in both the eyes. Pattern-reversal visually evoked potential (VEP) showed delayed latency of the P100 component in both the eyes. Electrooculography showed a normal light peak-to-dark trough ratio in both the eyes. Magnetic resonance imaging (MRI) brain showed chronic infarct and gliosis in both the occipital lobes. MR angiography showed pruning of P4 segments of both the posterior cerebral artery. Perfusion imaging showed reduction of perfusion in both the parieto-occipital lobes.

CONCLUSION

Hanging survivors can develop visual loss after their recovery. The visual loss may be a result of simultaneous ischemic insult to the occipital lobe cortex, optic nerve and retina.

Abdominal arterial lesions associated with antiphospholipid antibodies: A comparative cross sectional magnetic resonance angiography study

INTRODUCTION

Case reports and small case series suggest that stenotic lesions of the renal, coeliac and mesenteric arteries may occur in the antiphospholipid syndrome (APS) resulting in clinical consequences such as hypertension and abdominal angina.

OBJECTIVE

To determine the prevalence of stenotic lesions in arteries arising from the middle aorta in patients with antiphospholipid antibodies (aPL) compared with healthy, hypertensive and atherosclerotic controls.

PATIENTS AND METHODS

In a cross-sectional comparative radiological study using magnetic resonance angiography (MRA) we assessed 5 groups of subjects for the prevalence of stenotic lesions in arteries arising from the middle aorta: APS/aPL positive, healthy renal donors, patients with hypertension, patients with atherosclerosis defined radiologically and patients with systemic lupus erythematosus and vasculitis who were negative for aPL. All subjects underwent MRA in suspended respiration and images were assessed by 2 senior radiologists blinded to the clinical details.

RESULTS

In the atherosclerosis group, vascular stenotic lesions were more prevalent (71%) than in any other group (p≤ 0.000002). The prevalence of all stenotic lesions in aPL positive patients (33%) was significantly higher than in the renal donors (18%) and hypertensive patients (19%) (p≤ 0.009). Renal artery stenosis was significantly more prevalent in aPL positive patients than in renal donors (p≤ 0.0006) but similar to the prevalence in hypertensive patients. Coeliac and/or mesenteric lesions were significantly more common in aPL positive patients vs hypertensive patients (p≤ 0.001). Stenoses did not correlate with traditional risk factors.

CONCLUSION

Arterial stenotic lesions in arteries arising from the middle aorta were highly prevalent in atherosclerotic subjects and were more common in aPL positive patients than hypertensive patients and healthy renal donors.

Self-navigated versus navigator-gated 3D MRI sequence for non-enhanced aortic root measurement in transcatheter aortic valve implantation

OBJECTIVES

To prospectively compare image-quality, reliability and graft sizing of a prototype self-navigated and a navigator-gated non-contrast three dimensional (3D) whole-heart magnetic-resonance-angiography (MRA) sequence with computed-tomography-angiography (CTA) for planning transcatheter-aortic-valve-implantation (TAVI).

METHODS

Self- and navigator-gated 1.5 T MRA were performed in 27 patients (aged 83 ± 5 years, 41 % male) for aortic root sizing and coronary ostia height measurements; 15 (56 %) patients underwent additional CTA. Subjective-image quality was graded on a 4-point Likert scale, objective MRA image-quality was assessed by signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Continuous MRA and CTA measurements were analyzed with regression and Bland-Altman analysis, valve sizing by kappa statistics.

RESULTS

Median image-quality as rated by two observers was 1.5 [interquartile range (IQR) 1-3] for self-navigated MRA and 1 [IQR 1-2] for navigator-gated MRA (p = 0.059). SNR and CNR were comparable between MRA sequences (p = 0.471 and 0.445, respectively). Acquisition time was shorter for self-navigated MRA compared to navigator-gated MRA (5.5 ± 1 min vs, 6.5 ± 2 min, p = 0.029). Inter-observer correlation of aortic root measurements was high to very high for both self- and navigator-gated MRA (r = 0.75 to 0.94 and r = 0.85 to 0.96, respectively, all p < 0.0001). Theoretical prosthetic valve sizing of self-navigated MRA and CTA was equivalent (κ = 1). However, in four patients (15 %) one coronary ostium each (right coronary artery 3, left main artery 1) was not clearly definable on self-navigated MRA.

CONCLUSION

Self-navigated MRA enables aortic annulus TAVI measurements without significant difference to navigator-gated MRA at shortened acquisition time. Prosthesis sizing by self-navigated MRA measurements is equivalent to navigator-gated MRA and CTA-based choice.

Evaluation of magnetic resonance angiography as a possible alternative to rotational angiography or computed tomography angiography for assessing cerebrovascular computational fluid dynamics

The aim of this study was to conduct a flow experiment using a cerebrovascular phantom and investigate whether magnetic resonance angiography (MRA) could replace three-dimensional rotational angiography (RA) and computed tomography angiography (CTA) to construct vascular models for computational fluid dynamics (CFD). We performed MRA and 3D cine phase-contrast (PC) MR imaging with a silicone cerebrovascular phantom of an internal carotid artery-posterior communicating artery aneurysm with blood-mimicking fluid, and controlled flow with a flowmeter. We also obtained RA and CTA data for the phantom. Four analysts constructed vascular models based on the three different modalities. These 12 constructed models used flow information based on 3D cine PC MR imaging for CFD. We compared RA-, CTA-, MRA-based CFD results using the micro-CT-based CFD result as the criterion standard to investigate whether MRA-based CFD was not inferior to RA- or CTA-based CFD. We also analyzed the inter-analyst variability. Wall shear stress (WSS) distributions and streamlines of RA- or MRA-based CFD and those of micro-CT-based CFD were similar, but the vascular models and WSS values were different. Accuracy in measurements of blood vessel diameter, cross-sectional maximum velocity, and spatially averaged WSS was the highest for RA-based CFD, followed by MRA-based and CTA-based CFD using micro-CT-based CFD result as the reference. Except maximum velocity from CTA, all other parameters had good inter-analyst agreement using different modalities. The results demonstrated that non-invasive MRA can be used for cerebrovascular CFD models with good inter-analyst agreements.

Pointwise encoding time reduction with radial acquisition in subtraction-based magnetic resonance angiography to assess saccular unruptured intracranial aneurysms at 3 Tesla

PURPOSE

To investigate the clinical utility of pointwise encoding time reduction with radial acquisition in subtraction-based magnetic resonance angiography (PETRA-MRA) and time-of-flight magnetic resonance angiography (TOF-MRA) to evaluate saccular unruptured intracranial aneurysms (UIAs).

METHODS

A total of 49 patients with 54 TOF-MRA-identified saccular UIAs were enrolled. The morphologic parameters, contrast-to-noise-ratios (CNRs), and sharpness of aneurysms were measured using PETRA-MRA and TOF-MRA. Two radiologists independently evaluated subjective image scores, focusing on aneurysm signal homogeneities and sharpness depictions using a 4-point scale: 4, excellent; 3, good; 2, poor; 1, not assessable. PETRA-MRA and TOF-MRA acoustic noises were measured.

RESULTS

All aneurysms were detected with PETRA-MRA. The morphologic parameters of 15 patients evaluated with PETRA-MRA were more closely correlated with those receiving computed tomography angiography over those receiving TOF-MRA. No significant differences between PETRA-MRA and TOF-MRA parameters were seen in the 54 UIAs (p > 0.10), excluding those with inflow angles (p < 0.05). In four patients with inflow angles on PETRA-MRA, the angles were more closely related to those of digital subtraction angiography than those of TOF-MRA. CNRs between TOF-MRA and PETRA-MRA were comparable (p = 0.068), and PETRA-MRA sharpness values and subjective image scores were significantly higher than those of TOF-MRA (p < 0.001). Inter-observer agreements were excellent for both PETRA-MRA and TOF-MRA (intraclass correlation coefficients were 0.90 and 0.97, respectively). The acoustic noise levels of PETRA-MRA were much lower than those of TOF-MRA (59 vs.73 dB, p < 0.01).

CONCLUSIONS

PETRA-MRA, with better visualization of aneurysms and lower acoustic noise levels than TOF-MRA, showed a superior diagnostic performance for depicting saccular UIAs.

Vascular magnetic resonance angiography techniques

Magnetic resonance angiography (MRA) denotes a unique option for the evaluation of peripheral vasculature due to its noninvasive nature, lack of ionizing radiation exposure, potential for non-contrast examination, and ability for generating volumetric representations that showcase vascular pathology. The constant evolution of the available MRA techniques, however, makes understanding and determining an optimal imaging protocol difficult. Here we present a brief overview of the major MRA sequence options, their major weaknesses and strengths, and related imaging considerations. Understanding the technical underpinnings of the various MRA methods helps with recognition of common imaging issues and artifacts and rendering clinically relevant interpretations.

Accelerated Time-of-Flight Magnetic Resonance Angiography with Sparse Undersampling and Iterative Reconstruction for the Evaluation of Intracranial Arteries

OBJECTIVE

To compare the image quality of three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) with sparse undersampling and iterative reconstruction (sparse TOF) with that of conventional TOF MRA.

MATERIALS AND METHODS

This study included 56 patients who had undergone sparse TOF MRA for intracranial artery evaluation on a 3T MR scanner. Conventional TOF MRA scans were also acquired from 29 patients with matched acquisition times and another 27 patients with matched scanning parameters. The image quality was scored using a five-point scale based on the delineation of arterial vessel segments, artifacts, overall vessel visualization, and overall image quality by two radiologists independently, and the data were analyzed using the non-parametric Wilcoxon signed-rank test. Contrast ratios (CRs) of vessels were compared using the paired t test. Interobserver agreement was calculated using the kappa test.

RESULTS

Compared with conventional TOF at the same spatial resolution, sparse TOF with an acceleration factor of 3.5 could reduce acquisition time by 40% and showed comparable image quality. In addition, when compared with conventional TOF with the same acquisition time, sparse TOF with an acceleration factor of 5 could also achieve higher spatial resolution, better delineation of vessel segments, fewer artifacts, higher image quality, and a higher CR (p < 0.05). Good-to-excellent interobserver agreement (κ: 0.65-1.00) was obtained between the two radiologists.

CONCLUSION

Compared with conventional TOF, sparse TOF can achieve equivalent image quality in a reduced duration. Furthermore, using the same acquisition time, sparse TOF could improve the delineation of vessels and decrease image artifacts.

Quantification of morphometry and intensity features of intracranial arteries from 3D TOF MRA using the intracranial artery feature extraction (iCafe): A reproducibility study

BACKGROUND

Accurate and reliable vascular features extracted from 3D time-of-flight (TOF) magnetic resonance angiography (MRA) can help evaluate cerebral vascular diseases and conditions. The goal of this study was to evaluate the reproducibility of an intracranial artery feature extraction (iCafe) algorithm for quantitative analysis of intracranial arteries from TOF MRA.

METHODS

Twenty-four patients with known intracranial artery stenosis were recruited and underwent two separate MRA scans within 2 weeks of each other. Each dataset was blinded to associated imaging and clinical data and then processed independently using iCafe. Inter-scan reproducibility analysis was performed on the 24 pairs of scans while intra-/inter-operator reproducibility and stenosis detection were assessed on 8 individual MRA scans. After tracing the vessels visualized on TOF MRA, iCafe was used to automatically extract the locations with stenosis and eight other vascular features. The vascular features included the following six morphometry and two signal intensity features: artery length (total, distal, and proximal), volume, number of branches, average radius of the M1 segment of the middle cerebral artery, and average normalized intensity of all arteries and large vertical arteries. A neuroradiologist independently reviewed the images to identify locations of stenosis for the reference standard. Reproducibility of stenosis detection and vascular features was assessed using Cohen's kappa, the intra-class correlation coefficient (ICC), and within-subject coefficient of variation (CV).

RESULTS

The segment-based sensitivity of iCafe for stenosis detection ranged from 83.3-91.7% while specificity was 97.4%. Kappa values for inter-scan and intra-operator reproducibility were 0.73 and 0.77, respectively. All vascular features demonstrated excellent inter-scan and intra-operator reproducibility (ICC = 0.91-1.00, and CV = 1.21-8.78% for all markers), and good to excellent inter-operator reproducibility (ICC = 0.76-0.99, and CV = 3.27-15.79% for all markers).

CONCLUSION

Intracranial artery features can be reliably quantified from TOF MRA using iCafe to provide both clinical diagnostic assistance and facilitate future investigative quantitative analyses.

Triptans and CGRP blockade - impact on the cranial vasculature

The trigeminovascular system plays a key role in the pathophysiology of migraine. The activation of the trigeminovascular system causes release of various neurotransmitters and neuropeptides, including serotonin and calcitonin gene-related peptide (CGRP), which modulate pain transmission and vascular tone. Thirty years after discovery of agonists for serotonin 5-HT1B and 5-HT1D receptors (triptans) and less than fifteen after the proof of concept of the gepant class of CGRP receptor antagonists, we are still a long way from understanding their precise site and mode of action in migraine. The effect on cranial vasculature is relevant, because all specific anti-migraine drugs and migraine pharmacological triggers may act in perivascular space. This review reports the effects of triptans and CGRP blocking molecules on cranial vasculature in humans, focusing on their specific relevance to migraine treatment.

Imaging of Oculomotor (Third) Cranial Nerve Palsy

When evaluating a patient with an oculomotor cranial nerve palsy it may be unclear which neuroimaging modality is optimal; MRI, MR angiography, computed tomography, computed tomography angiography, or intraarterial digital subtraction angiography. We discuss the clinical guidelines in the evaluation of such patients and review neuroimaging techniques, outlining the advantages and disadvantages of each.

Off-resonance magnetic resonance angiography improves visualization of in-stent lumen in peripheral nitinol stents compared to conventional T1-weighted acquisitions: an in vitro comparison study

To compare the value of inversion recovery with on-resonant water suppression (IRON) to conventional T1-weighted (T1w) MRA and computed tomography angiography (CTA) for visualization of peripheral nitinol stents. We visualized 14 different peripheral nitinol stents in vitro both using Gadolinium (Gd) and ultrasmall superparamagnetic iron nanoparticles (USPIOs) for conventional T1w and IRON-MRA using clinical grade 1.5T MR scanner and iodinated contrast material for CTA using a 256-slice CT scanner. Parameter assessment included signal- and contrast-to-noise ratio (S/CNR), relative in-stent signal and artificial lumen narrowing. X-ray angiography served as gold standard for diameter assessment. Gd-enhanced IRON-MRA exhibited highest in-stent SNR and CNR values compared to conventional T1w MRA (IRON (Gd/USPIO): SNR = 30 ± 3/21 ± 2, CNR = 23 ± 2/14 ± 1; T1w: SNR = 16 ± 1/14 ± 2, CNR = 12 ± 1/10 ± 1, all p < 0.05). Furthermore, IRON-MRA achieved highest relative in-stent signal both using Gd and USPIO (IRON (Gd/USPIO): 121 ± 8 %/103 ± 6 %; T1w: 73 ± 2 %/66 ± 4 %; CTA: 84 ± 6 %, all p < 0.05). However, artificial lumen narrowing appeared similar in all imaging protocols (IRON (Gd/USPIO): 21 ± 3 %/21 ± 2 %; T1w: 16 ± 4 %/17 ± 3 %; CTA: 19 ± 2 %, all p = NS). Finally, IRON-MRA provided improvement of the in-stent lumen visualization with an 'open-close-open' design, which revealed a complete in-stent signal loss in T1w MRA. IRON-MRA improves in-stent visualization in vitro compared to conventional T1w MRA and CTA. In light of the in vitro results with Gd-enhanced IRON-MRA, the clinical implementation of such an approach appears promising.

Preoperative planning of renal transplantation: a comparison of non-contrast-enhanced ultrasonography, computed tomography, and magnetic resonance angiography with observations from surgery

BACKGROUND

Many candidates for kidney transplantation need to undergo vessel examination before the transplantation procedure.

PURPOSE

To identify the optimal preoperative modality for the examination of vessel status without the use of contrast agents in kidney transplant candidates.

MATERIAL AND METHODS

Fifty-three consecutive patients were examined and 31 patients were transplanted. Ultrasonography (US), non-contrast-enhanced computed tomography (NCCT), and non-contrast-enhanced magnetic resonance angiography (NCMRA) were compared using inspection during kidney transplantation (TX) as a reference standard. The sensitivity and specificity to severe arteriosclerotic changes and the accuracy were calculated. Kappa statistics were used to assess the agreement between TX and the different examination modalities, and McNemar's test was used to test for significant differences.

RESULTS

US had higher sensitivity (1.0) and better agreement with observations from surgery (k = 0.89) than both NCCT (sensitivity = 0.60; k = 0.72) and NCMRA (sensitivity = 0.20; k = 0.30). No significant difference was found between TX and US (P = 0.3173) or TX and NCCT (P = 0.1573), but there was a significant difference between TX and NCMRA (P = 0.0455). US was inconclusive in 20% of cases, and the internal iliac artery could not be visualized in 69% of cases.

CONCLUSION

Either US or NCCT can be used as the preferred preoperative imaging modality to examine vessel status before kidney transplantation, but a combination of the two is preferable. NCMRA should not be used as the sole imaging modality for preoperative imaging before kidney transplantation because of its low sensitivity in detecting severe arteriosclerotic disease without the presence of stenosis.

Temporal profile of the vascular anatomy evaluated by 9.4-tesla magnetic resonance angiography and histological analysis in mice with the R4859K mutation of RNF213, the susceptibility gene for moyamoya disease

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with an unknown etiology. Recent genome-wide and locus-specific association studies identified the RNF213 gene (RNF213) as an important susceptibility gene of MMD among East Asian populations; however, the mechanism by which an abnormality in RNF213 leads to MMD has not yet been elucidated. Therefore, we herein generated Rnf213-knock-in mice (RNF213-KI) expressing a missense mutation in mouse Rnf213, p. R4828K, on Exon 61, corresponding to human RNF213, p. R4859K, on Exon 60, in MMD patients, and investigated whether they developed MMD. We assessed the temporal profile of intracranial arteries by 9.4-T magnetic resonance angiography (MRA) continuously in the same mouse up to 64 weeks of age. The ratios of the outer diameter of the internal carotid artery (ICA)/basilar artery (BA) and middle cerebral artery (MCA)/BA were evaluated histopathologically. The common carotid arteries (CCA) were sectioned and arterial wall thickness/thinness was evaluated by Elastica-Masson staining before and after CCA ligation, which selectively induced vascular hyperplasia. The results obtained showed that RNF213-KI grew normally, with no significant difference being observed in MRA findings or the anatomy of the circle of Willis between homozygous RNF213-KI and wild-type (Wt) littermates. Furthermore, no significant difference was noted in the diameter of the intracranial vasculature (ICA/BA; p=0.82, MCA/BA; p=0.27) or in vascular remodeling after CCA ligation. Therefore, RNF213-KI did not spontaneously develop MMD. Multiple secondary insults such as environmental factors may contribute to the onset of MMD in addition to genetic factors.

Flow artifact in the anterior communicating artery resembling aneurysm on the time of flight MR angiogram

BACKGROUND

Magnetic resonance angiogram (MRA) of the brain is a widely employed non-invasive test to diagnose aneurysms. However, its overall accuracy is less than digital subtraction angiography and is prone to give false-positive or false-negative results. False-negative results can be seen with hemorrhage, lipoma, dermoid, posterior lobe of the pituitary gland, and the flow artifacts.

PURPOSE

To describe the findings associated with false aneurysms in the anterior communicating artery on the time of flight MRA and review the physical principles behind this artifact.

MATERIAL AND METHODS

This short series comprises of four patients whose MRA showed suspicious aneurysms in the region of the anterior communicating artery (ACOM) on time of flight MRA.

RESULTS

Two patients underwent catheter angiogram and the other two patients had computed tomography angiogram. None of these cases proved to have aneurysms and normal anterior communicating arteries were seen in all the patients. The findings on the MR angiograms were considered artifacts. All of the pseudoaneurysm had tapered appearance.

CONCLUSION

MR angiogram can result in artifacts at ACOM which may be mistaken for aneurysm. Such pseudoaneurysms have characteristic appearance and should be followed up with non-invasive tests.

Diagnostic Accuracy of Magnetic Resonance Angiography for Detection of Intracranial Aneurysms in Patients with Acute Subarachnoid Hemorrhage; A Comparison to Digital Subtraction Angiography

OBJECTIVES

To determine the diagnostic accuracy of magnetic resonance angiography (MRA) compared to intra-arterial digital subtraction angiography (DSA) in detection of intracranial aneurysms in those suffering from acute subarachnoid hemorrhage (SAH).

METHODS

This observational diagnostic study was performed at a tertiary teaching hospital and reference center in Shiraz, Iran. We included 55 patients who presented to our center with the diagnosis of acute SAH. All the patients underwent MRA and DSA during their hospital course in order to detect the intracranial aneurysms. The time-of-flight MRA protocol was used and the results were compared to the results of DSA as the gold standard test. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for MRA.

RESULTS

The mean age of the patients was 46.3 ± 7.9 including 26 (47.3%%) men and 29 (52.7%) women. In 46 patients, 51 intracranial aneurysms were diagnosed by DSA (5 patients had two aneurysms). No evidence of intracranial aneurysm was found in 9 patients with subarachnoid hemorrhage. MRA correctly identified 42 of the 51 aneurysms (sensitivity 82%) and missed 9 small aneurysms (less than 10 mm). MRA revealed one false- positive finding, resulting in a specificity of 88.8%. The PPC and NPV for MRA were 97% and 47%, respectively. The diagnostic accuracy per aneurysm was 0.83 for MRA.

CONCLUSION

High sensitivity and specificity of MRA compared to DSA in diagnosis of intracranial aneurysms in those with acute SAH indicate that MRA could be reliably used as a diagnostic tool for this purpose. However we cannot recommend it as a routine substitute for DSA before surgery.