MRA of intracranial aneurysms embolized with platinum coils: a vascular phantom study at 1.5T and 3T

PURPOSE: To analyze the influence of matrix and echo time (TE) of three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA) on the depiction of residual flow in aneurysms embolized with platinum coils at 1.5T and 3T. MATERIALS AND METHODS: A simulated intracranial aneurysm of the vascular phantom was loosely packed to maintain the patency of some residual aneurysmal lumen with platinum coils and connected to an electromagnetic flow pump with pulsatile flow. MRAs were obtained altering the matrix and TE of 3D TOF sequences at 1.5T and 3T. RESULTS: The increased spatial resolution and the shorter TE offered better image quality at 3T. For the depiction of an aneurysm remnant, the high-spatial-resolution 3T MRA (matrix size of 384 x 224 and 512 x 256) with a short TE of < or =3.3 msec were superior to the 1.5T MRA obtained with any sequences. CONCLUSION: 3T MRA is superior to 1.5T MRA for the assessment of aneurysms embolized with platinum coils; the combination of the 512 x 256 matrix and short TE (3.3 msec or less) seems feasible at 3T.     

Follow-up of coiled cerebral aneurysms at 3T: comparison of 3D time-of-flight MR angiography and contrast-enhanced MR angiography

BACKGROUND AND PURPOSE: Our aim was to compare contrast-enhanced MR angiography (CE-MRA) and 3D time-of-flight (TOF) MRA at 3T for follow-up of coiled cerebral aneurysms.MATERIALS AND METHODS: Fifty-two patients treated with Guglielmi detachable coils for 54 cerebral aneurysms were evaluated at 3T MRA. 3D TOF MRA (TR/TE = 23/3.5; SENSE factor = 2.5) and CE-MRA by using a 3D ultrafast gradient-echo sequence (TR/TE = 5.9/1.8; SENSE factor = 3) enhanced with 0.1-mmol/kg gadobenate dimeglumine were performed in the same session. Source images, 3D maximum intensity projection, 3D shaded surface display, and/or 3D volume-rendered reconstructions were evaluated in terms of aneurysm occlusion/patency and artifact presence.RESULTS: In terms of clinical classification, the 2 MRA sequences were equivalent for 53 of the 54 treated aneurysms: 21 were considered fully occluded, whereas 16 were considered to have a residual neck and 16 were considered residually patent at follow-up MRA. The remaining aneurysm appeared fully occluded at TOF MRA but had a residual patent neck at CE-MRA. Visualization of residual aneurysm patency was significantly (P = .001) better with CE-MRA compared with TOF MRA for 10 (31.3%) of the 32 treated aneurysms considered residually patent with both sequences. Coil artifacts were present in 5 cases at TOF MRA but in none at CE-MRA. No relationship was apparent between the visualization of patency and either the size of the aneurysm or the interval between embolization and follow-up.CONCLUSION: At follow-up MRA at 3T, unenhanced TOF and CE-MRA sequences are similarly effective at classifying coiled aneurysms as occluded or residually patent. However, CE-MRA is superior to TOF MRA for visualization of residual patency and is associated with fewer artifacts.

Regular imaging follow-up of patients with intracranial aneurysms treated with Guglielmi detachable coils (GDCs) is necessary because of the risk of aneurysm reconfiguration (ie, coil compaction and/or growth of a residual aneurysm neck or body remnant) with time.^1–4 Of the techniques available for monitoring the results of embolization therapy, MR angiography (MRA) has emerged as the technique of choice at most institutions. Advantages over conventional digital subtraction angiography (DSA) include minimal invasiveness with no associated risk of neurologic complications, reduced patient discomfort and inconvenience, greater cost savings, and no exposure to ionizing radiation or potentially nephrotoxic iodinated contrast media. An alternative minimally invasive procedure is CT angiography (CTA). However, whereas this technique has proved useful for aneurysm detection,^5–9 limitations to its use for follow-up of coiled aneurysms include streak and other coil-related artifacts.^10–12 Moreover, CTA also requires exposure to ionizing radiation and iodinated contrast media, which may be undesirable if repeat follow-up examinations are required.Studies performed to date have shown that nonenhanced 3D time-of-flight (TOF) MRA sequences on 1.5T scanners are frequently satisfactory for the follow-up of coiled aneurysms^1–20 but that 3D TOF MRA on 3T scanners offers improved depiction of both treated²¹ and untreated²² aneurysms due to the greater spatial and contrast resolution achievable at a higher magnetic field strength. Concerning the use of gadolinium contrast material, some studies have suggested that contrast-enhanced MRA (CE-MRA) provides no additional benefit compared with nonenhanced 3D TOF MRA at either 1.5T^15,20 or 3T,²¹ whereas other studies have shown that CE-MRA permits better visualization of coiled aneurysms and of branch arteries and residual neck, particularly in large or giant aneurysms.^14,22–26 Recently, Nael et al²⁷ demonstrated that CE-MRA with highly accelerated (×4) parallel acquisition at 3T provides comparable information to accelerated (×2) 3D TOF MRA at 3T for the characterization of untreated intracranial aneurysms without the known drawbacks of TOF MRA techniques (ie, prolonged acquisition time, spin saturation, and flow-related artifacts). On the other hand, Gibbs et al²⁸ showed that with elliptic-centric imaging, 3D TOF MRA at 3T is superior to CE-MRA at 3T in terms of both image quality and detection of untreated intracranial aneurysms. Our study was performed to evaluate CE-MRA with accelerated (×3) parallel acquisition at 3T compared with accelerated (×2.5) 3D TOF MRA at 3T for the follow-up of GDC-treated intracranial aneurysms. To the authors’ knowledge, this is the first study to compare MRA sequences at 3T for follow-up of coiled aneurysms.     

肾动脉高分辨力三维增强磁共振血管成像术:透视触发和并行采集技术使用初探

目的:评估透视触发和并行采集技术用于肾动脉高分辨力三维增强磁共振血管成像术的可行性和对肾动脉的显影诊断效果。方法:90例临床诊断或怀疑肾动脉或腹主动脉病变的患者行高分辨力肾动脉三维增强磁共振血管成像(3D CE MRA)。使用透视触发软件启动肾动脉3D CE MRA扫描,扫描采用K空间中心填充法和加速因子为2的并行采集技术。分析图象质量和病变显示情况,并与其它检查结果对照。结果:肾动脉3D CE MRA显示了90例患者共810支动脉段(100%显示率),平均显示等级为3.88。3D CE MRA显示8例11支副肾动脉,显示等级均为4.0。肾动脉段级分支的显示率为73%(66/90例)。所有病例在动脉显示区静脉均未显影或显影很淡,平均等级为0.20。3D CE MRA发现639支动脉段正常;66支动脉段管壁不规则;55支动脉段轻度狭窄;37支动脉段严重狭窄;2支动脉段闭塞;11支动脉段动脉瘤形成。其中96支肾动脉存在狭窄,11支副肾动脉均正常。共有43例病例,肾动脉3D CE MRA与其它血管成像技术作了比较,3D CE MRA的检查结果与之完全符合。结论:透视触发并行采集肾动脉高分辨力3D CE MRA简单可行,成像时间短,空间分辨力高,能清楚显示肾动脉且无静脉污染。     

Cerebrovascular pathology. Comparison of magnetic resonance and magnetic resonance angiography]

After making the visualization of the intracranial circulation possible without contrast media, the radiologist is now evaluating the diagnostic role of the different techniques of MRA. Attempts are also being made to characterize the main patterns of intracranial vascular diseases. The authors examined, with 3D TOF MRA, 40 patients presenting with 50 vascular lesions on MRI scans. Twenty of 40 patients were also studied with angiography. Seventeen aneurysms were detected, together with 3 stenoses of the cerebral arteries, 13 arteriovenous malformations, 12 dolichobasilar arteries, 3 postoperative and 2 post-embolization controls. MRI was performed with a superconductive magnet (1.5 T), a dedicated coil and gradient-echo 3D TOF FT sequences. The refocused sequence for flux, FISP 3DFT, required the following parameters: TR = 0.04 s, TE = 10 ms, flip angle = 15 degrees, 256 x 256 matrix, 1 acquisition. The 64-80 mm volume along the axial plane was divided so that an actual 1-mm thickness was excited. In post-processing, the maximum-intensity projection was employed on the axial plane 0 degrees-90 degrees (15 degrees interval). In the various conditions, the results obtained with MRA were correlated and compared with MRI findings. MRA provided useful additional information in 27.4% of cases in the study of aneurysms, arteriovenous malformations, vascular occlusion and dolichobasilar arteries, as well as in the follow-up of these lesions. MRA is currently suggested in the evaluation of cerebral circulation and is considered a complementary technique to MRI. MRA is also to be used preliminary to angiography.     

Contrast-enhanced MR angiography at 3T in the evaluation of intracranial aneurysms: a comparison with time-of-flight MR angiography

The combination of 3T and parallel-acquisition techniques holds promise for improved performance of contrast-enhanced MR angiography (MRA), in terms of speed, spatial resolution, and coverage. We present a comparison of 2 MRA techniques, including time-of-flight (TOF) and contrast-enhanced MRA, for detection and evaluation of intracranial aneurysms. Our results show that contrast-enhanced MRA with highly accelerated parallel acquisition at 3T does not have the known drawbacks of TOF-MRA techniques, including prolonged acquisition time, spin saturation, and flow-related artifacts, with comparable aneurysm characterization.     

3.OT高时间分辨率对比增强MRA颅内血管成像

目的:评价3.0T高时间分辨率对比增强磁共振血管成像(TR 3D CE-MRA)在颅内血管成像的技术可行性和临床应用价值.方法:经医院伦理委员会批准,回顾性搜集21例患者,采用3.0T磁共振,首先行常规序列T1 WI、T2 WI和TOF MRA扫描,然后在确定痛变处用TR 3D CE-MRA即快速小角度激发梯度回波序列...     

三维梯度回波增强MRA对脑巨大动脉瘤的应用价值

目的 评价给梯度回波（３Ｄ－ＳＰＧＲ）增强ＭＲＡ对颅脑巨大动脉瘤的应用价值。材料与方法 １６例共１８个巨大动脉瘤,包括颈内动脉虹吸部１０个,椎动脉４个,基底动脉１个,大脑前动脉１个,后交通动脉１个。ＭＲ机为ＧＥ１．５Ｔ超导型及相应工作站。增强３Ｄ－ＳＰＧＲ轴位扫描后,进行矢、冠、斜位等多平面重建（ｍｕｌｔｉｐｌａｎｎｅｒ ｒｅｃｏｍｓｔｒｕｃｔｉｏｎ,ＭＰＲ）,并与传统３Ｄ－ＴＯＦ法ＭＲＡ进行对比     

Time-resolved 3D contrast-enhanced MRA with GRAPPA on a 1.5-T system for imaging of craniocervical vascular disease: initial experience

Introduction: For three-dimensional (3D) imaging with magnetic resonance angiography (MRA) of the cerebral and cervical circulation, both a high temporal and a high spatial resolution with isovolumetric datasets are of interest. In an initial evaluation, we analyzed the potential of contrast-enhanced (CE) time-resolved 3D-MRA as an adjunct for neurovascular MR imaging. Methods: In ten patients with various cerebrovascular disorders and vascularized tumors in the cervical circulation, high-speed MR acquisition using parallel imaging with the GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) algorithm on a 1.5-T system with a temporal resolution of 1.5 s per dataset and a nearly isovolumetric spatial resolution was applied. The results were assessed and compared with those from conventional MRA and digital subtraction angiography (DSA). Results: CE time-resolved 3D-MRA enabled the visualization and characterization of high-flow arteriovenous shunts in cases of vascular malformations or hypervascularized tumors. In steno-occlusive disease, the method provided valuable additional information about altered vessel perfusion compared to standard MRA techniques such as time-of-flight (TOF) MRA. The use of a nearly isovolumetric voxel size allowed a free-form interrogation of 3D datasets. Its comparatively low spatial resolution was found to be the major limitation. Conclusion: In this preliminary analysis, CE time-resolved 3D-MRA was revealed to be a promising complementary MRA sequence that enabled the visualization of contrast flow dynamics in various types of neurovascular disorders and vascularized cervical tumors.     

Comparison of intracranial 3D-ToF-MRA with and without parallel acquisition techniques at 1.5T and 3.0T: preliminary results

PURPOSE: To evaluate the performance of four 3D-ToF magnetic resonance angiography (MRA) sequences with and without integrated parallel acquisition techniques (iPAT) at 1.5T and 3.0T in imaging intracranial vessels. MATERIAL AND METHODS: Seven volunteers and 5 patients (4 aneurysms, 1 AVM) underwent 3D-ToF-MRA at 1.5T (Magnetom Sonata) and 3.0T (Magnetom Trio) with and without parallel acquisition techniques (iPAT) using similarly designed 8-channel phased-array head coils. Imaging time of the pulse sequences was set to 7.15 and 7.35 min, respectively. Images were analyzed quantitatively by calculating signal-to-noise (SNR) and contrast-to-noise (CNR) ratios of proximal M2 segments and qualitatively by using a 5-point scale. RESULTS: SNR and CNR were significantly higher for both 3D-ToF sequences at 3.0T compared with both pulse sequences at 1.5T. The highest SNR and CNR were obtained at 3.0T without iPAT. However, because of a higher spatial resolution (matrix 512 x 640) visualization of small vessel details was best at 3.0T with iPAT. CONCLUSION: Intracranial 3D-ToF-MRA at 3.0T offers superior image quality compared with 1.5T, particular in the delineation of smaller vessels. In contrast to 1.5T, implementation of iPAT at 3.0T is of additional benefit since the high SNR available at 3.0T allows for higher spatial resolution without prolongation of measurement time.     

Improved image quality of intracranial aneurysms: 3.0-T versus 1.5-T time-of-flight MR angiography

BACKGROUND AND PURPOSE: We hypothesize that the nearly doubling of signal-to-noise ratio at 3.0 T compared with that at 1.5 T yields improved clinical MR angiograms and enables superior visualization of intracranial aneurysms. The goal of this study was to determine whether 3.0-T time-of-flight (TOF) MR angiography is superior to 1.5-T TOF MR angiography in the detection and characterization of intracranial aneurysms. METHODS: Fifty consecutive patients referred for MR angiography of a known or suspected intracranial aneurysm underwent 3-T TOF MR angiography. Seventeen of these 50 patients had also previously undergone 1.5-T TOF MR angiography and these images were used as a basis for comparison with images obtained at 3.0 T. Fourteen of 23 patients in whom aneurysms were identified also underwent prior conventional angiography, which was used as the reference standard. Readers blinded to patient history identified the presence and location of aneurysm(s) on angiograms and graded images for overall image quality by using a five-point scale. RESULTS: Twenty-eight aneurysms were identified in 23 of 50 patients. Seventeen aneurysms in 17 patients had been documented with 1.5-T MR angiography. The 3.0-T technique had a higher mean image quality score than that of the 1.5-T MR technique (P <.0001). Both 3.0-T and 1.5-T TOF MR angiography depicted all the aneurysms that had been documented by conventional angiography. CONCLUSION: 3D TOF MR angiography at 3 T offers superior depiction of intracranial aneurysms compared with that of 1.5-T TOF MR angiography.     

MR angiography at 3T versus digital subtraction angiography in the follow-up of intracranial aneurysms treated with detachable coils

BACKGROUND AND PURPOSE: Digital subtraction angiography (DSA) is used to follow-up intracranial aneurysms treated with detachable coils to identify recurrence and determine need for additional treatment. However, DSA is invasive and involves a small risk of neurologic complications. We assessed the feasibility and usefulness of 3D time-of-flight (TOF) MR angiography (MRA) performed at 3T compared with DSA for the follow-up of coil-treated intracranial aneurysms. METHODS: In a prospective study, 20 consecutive patients with 21 intracranial aneurysms treated with coils underwent DSA and nonenhanced and enhanced multiple overlapping thin-slab acquisition 3D TOF MRA at 3T on the same day at a mean follow-up of 6 months (range, 4-14 months) after coil placement. MRA images were evaluated for presence of artifacts, presence and size of aneurysm remnants and recurrences, patency of parent and branch vessels, and added value of contrast material enhancement. MRA and DSA findings were compared. RESULTS: Interobserver agreement of MRA was good, as was agreement between MRA and DSA. All three recurrences that needed additional treatment were detected with MRA. Minor disagreement occurred in four cases: three coil-treated aneurysms were scored on MRA images as having a small remnant, whereas on DSA images these aneurysms were occluded; the other aneurysm was scored on MRA images as having a small remnant, whereas on DSA images this was a small recurrence. Use of contrast material had no additional value. Coil-related MR imaging artifacts were minimal and did not interfere with evaluation of the occlusion status of the aneurysm. CONCLUSION: High-spatial-resolution 3D TOF MRA at 3T is feasible and useful in the follow-up of patients with intracranial aneurysms treated with coil placement.     

Contrast-enhanced three-dimensional MR angiography with an elliptical centric view for the evaluation of intracranial aneurysms

The purpose of this study was to assess the feasibility of high spatial resolution, selective arterial phase, 3D contrast-enhanced (CE) MR angiography with first pass bolus, software-trigger, elliptical centric view ordering in the detection of intracranial aneurysms. Our study included nine consecutive patients with ten intracranial aneurysms. 3D TOF MR angiography and 3D CE MR angiography were carried out with a 1.5-T MR scanner. 3D CE MR angiography was performed with an automated bolus detection algorithm and elliptical centric view order using ultrafast SPGR with a spatial resolution of 0.63×0.83×0.5 mm and imaging time of 55 s. Observers detected seven of ten aneurysms on 3D TOF MR angiograms and nine of ten aneurysms on 3D CE MR angiograms. 3D CE MR angiography clearly revealed an IC-PC aneurysm with a relatively smaller neck, a broad-based small aneurysm originating from tortuous and dilated MCA bifurcation, and a residual aneurysm and parent vessels adjacent to metallic aneurysmal clips, which had relatively low signal intensities on 3D TOF MR angiograms. 3D CE MR angiography was found to be a good and promising technique for detecting intracranial aneurysms with small necks and slow flow, vasculature with aneurysmal clips and tortuous vasculature with disturbed flow.     

High-resolution renal MRA: comparison of image quality and vessel depiction with different parallel imaging acceleration factors

PURPOSE: To investigate the image quality and vessel depiction of renal MRA with integrated parallel imaging techniques (iPAT) using acceleration factors of 2 and 3. MATERIALS AND METHODS: In this prospective study renal MRA was performed on 14 and 12 patients with acceleration factors of 3 and 2, respectively. For the MRA a 3D-GRE sequence with an acquired spatial resolution of 0.9 x 0.8 x 1.0 mm(3) was applied (TR/TE = 3.79 msec/1.39 msec, FOV = 400 mm x 320 mm, acquired matrix = 512 x 384, flip angle = 25 degrees) on a 32-channel 1.5T MR scanner. The acquisition time was 26 seconds with iPAT 2, and 19 seconds with iPAT3. All parameters other than acquisition time and acceleration factor were kept constant. To assess the signal-to-noise ratio (SNR) we performed repetitive phantom measurements using iPAT 2 and 3. The images were rated by two radiologists in terms of noise, artifacts, and the quality of vessel depiction for the proximal, segmental, and subsegmental renal artery. A Mann-Whitney U-test and kappa-test were used for statistical analysis. RESULTS: SNR decreased significantly with iPAT 3 in the phantom measurements. The two readers found no difference in noise, but significantly fewer artifacts with iPAT 3. The depiction of segmental vessels was significantly better for both readers with iPAT 3, and the subsegmental vessels were rated significantly better by one reader. iPAT 3 also resulted in a better interreader agreement. CONCLUSION: The use of iPAT 3 for renal MRA enables a better depiction of the distal parts of the renal artery. The decrease in SNR is not diagnostically impairing.     

Postoperative assessment of extracranial-intracranial bypass by time-resolved 3D contrast-enhanced MR angiography using parallel imaging

PURPOSE: Our goals were to assess image quality of time-resolved contrast-enhanced MR angiography (CE MRA), by using 3D data acquisition along with a parallel imaging technique that can improve temporal resolution and to compare this technique with 3D-time-of-flight (TOF) MRA in the postoperative assessment of extracranial (EC)-intracranial (IC) bypass surgery. METHODS: On a 1.5T imaging system, we performed CE MRA by using a 3D fast field-echo sequence in combination with a parallel imaging technique, to obtain images in the coronal plane centered at the postoperative site. Our patient group comprised 17 patients, including 13 after superficial temporal artery-middle cerebral artery (MCA) anastomosis, 3 after external carotid artery-MCA anastomosis, and one after extracranial vertebral artery-posterior cerebral artery anastomosis. Visualization of the anastomosis and the distal flow on the CE-MRA images was assessed comparatively with that on 3D-TOF MR angiograms obtained at the same time. In 6 patients, we also compared the efficiency of visualization on CE-MRA images with that on conventional angiograms. RESULTS: A temporal resolution of 0.8 s/frame could be achieved with the technique employed. The bypass was better demonstrated postoperatively on CE-MRA images than on 3D-TOF MR angiograms in 13 patients (76%), whereas the 2 methods were equivalent in 4 patients (24%). Good correspondence of results was observed in the 6 patients for whom CE MRA and conventional digital subtraction angiography (DSA) images were compared. CONCLUSION: CE MRA by using the parallel imaging technique can increase image acquisition speed with sufficient image quality. This technique is at least equivalent to 3D-TOF MRA to evaluate the postoperative status of EC-IC bypass.     

Follow-up of intracranial aneurysms selectively treated with coils: Prospective evaluation of contrast-enhanced MR angiography

BACKGROUND AND PURPOSE: The aim of this study was to determine the feasibility and usefulness of contrast-enhanced MR angiography (CE-MRA) for the follow-up of intracranial aneurysms treated with detachable coils, by comparing CE-MRA with digital subtraction angiography (DSA) and 3D time-of- flight (TOF) MRA. METHODS: Thirty-two patients with 42 treated aneurysms were included in the study; 6 had been treated for multiple aneurysms. All MRAs were performed with a 1.5T unit within 48 hours of DSA. We performed 2 types of acquisition: a 3D TOF sequence and CE-MRA. Twenty-eight patients were included 1 year after endovascular treatment, and 4 patients, after 3 years or more. DSA was the technique of reference for the detection of a residual neck or residual aneurysm. RESULTS: Compared with DSA, the sensitivity of MRA was good. For the detection of residual neck, there was no significant difference between the results of 3D TOF MRA (sensitivity, 75%-87.5%; specificity, 92.9%, according to both readers) and CE-MRA (sensitivity, 75%-82.1%; specificity, 85.7%-92.9%). For the detection of residual aneurysm, sensitivity and specificity of both techniques were the same, respectively 80%-100% and 97.3%-100%. Therefore, CE-MRA was not better than 3D TOF MRA for the detection of residual neck or residual aneurysm. For large treated aneurysms, there was no difference between decisions regarding further therapy after CE and 3D TOF MRA, even though CE-MRA with a short echotime and enhancement gave fewer artifacts and better visualization of recanalization than 3D TOF MRA. The interpretation of transverse source images and the detection of coil mesh packing seemed easier with 3D TOF imaging. CONCLUSION: This prospective study did not show that CE-MRA was significantly better than 3D TOF MRA for depicting aneurysm or neck remnants after selective endovascular treatment using coils. For aneurysms treated with coils, 3D TOF MRA seems a valid and useful technique for the follow-up of coiled aneurysms.     

Three-dimensional time-of-flight MR angiography in the evaluation of cerebral aneurysms

We review our preliminary experience with the use of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography (MRA) in the assessment of intra- and extracranial aneurysms. Six patients were examined: Five had intracranial aneurysms and one had a cervical carotid pseudoaneurysm. A 3D rephased gradient recalled echo pulse sequence and maximum intensity projection (MIP) reconstruction algorithm were used. Magnetic resonance angiography, spin echo MR, and conventional angiography were retrospectively reviewed with specific regard to individual vessel visualization, aneurysm depiction, and presence of artifact related to acquisition techniques or MIP reconstruction. All aneurysms were detected on MRA, and anatomical correlation with conventional angiography was excellent. Significant problems included loss of visualization of small vessels, intraluminal signal loss in large vessels, subacute thrombus simulating flow on MIP reconstructions, and limited projections obtainable with MIP techniques. Adequate MRA assessment of aneurysms can be obtained using a combination of T1-weighted spin echo images and 3D TOF MRA. Review of all components of the MRA is required. MRA may be useful in screening asymptomatic patients for intracranial aneurysms as well as in the follow-up of patients treated with balloon occlusion.     

脑血管疾病TOF法磁共振血流成像的初步探讨

笔者搜集了７０例诊断明确的脑血管疾病ＭＲＡ资料进行分析。其中２２例经Ｘ线脑血管造影证实。所有患者均进行了三维ＴＯＦ法ＭＲＡ扫描。结果表明，三维ＴＯＦ法能清楚地显示出脑动脉瘤、血管畸形、大动脉的狭窄和阻塞等血管病变，但由于饱和作用的影响，不能显示小动脉分支和静脉血管，并且在血管狭窄的显示方面存在着夸张作用和假象。与Ｘ线血管造影相比，ＭＲＡ虽具有成像迅速、无创伤等优点，但在小血管病变及血管狭窄的显示方面仍有不足。     

Intracranial time-of-flight MR angiography at 7T with comparison to 3T

PURPOSE: To establish the feasibility of intracranial time-of-flight (TOF) MR angiography (MRA) at 7T using phased array coils and to compare its performance to 3T. MATERIALS AND METHODS: In an initial study, five normal volunteers were scanned at 7T and 3T using eight-channel coils and standard acquisition parameters from a clinical TOF protocol. In a second study three additional studies were performed at 7T and 3T using empirically optimized 7T parameters. Contrast-to-noise (CNR) values were measured for major vessel segments. RESULTS: All measurements documented CNR increases at 7T, with a mean increase of 83% in the initial study and 88% in the second study. The CNR values achieved using the latter protocol were similar to the values obtained in the initial study, despite the 42% reduction expected due to the higher spatial resolution. CNR in the smaller peripheral vessels was increased dramatically, resulting in excellent visualization at high resolution. CONCLUSION: TOF MRA at 7T demonstrated improved visualization of the intracranial vasculature, particularly the smaller peripheral vessels, and may benefit studies of small aneurysms, atherosclerosis, vasospasm, and vasculitis.     

Three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA) and contrast-enhanced MRA of intracranial aneurysms treated with platinum coils

Background: Contrast-enhanced magnetic resonance angiography (CE-MRA) is less prone to flow-related signal intensity loss than three-dimensional time-of-flight (3D TOF) MRA and may therefore be more sensitive for detection of residual patency in platinum coil-treated intracranial aneurysms.

Purpose: To compare MRA and CE-MRA in the follow-up of intracranial aneurysms treated with platinum coils.

Material and Methods: CE-MRA and 3D TOF MRA (pre- and postcontrast injection) of the intracranial vasculature was performed at 1.5T in 38 patients (47 aneurysms) referred for DSA in the follow-up of coiled intracranial aneurysms.

Results: DSA showed aneurysm patency in 22/47 investigations. Patent aneurysm components were observed with CE-MRA in 18/22 cases, and with 3D TOF MRA in 21/22 cases. There was no significant difference in patent aneurysm component size between CE-MRA and 3D TOF MRA. In addition, CE-MRA showed six, 3D TOF MRA before contrast injection showed seven, and 3D TOF MRA after contrast injection showed eight cases with patent aneurysm components not observed on DSA.

Conclusion: 3D TOF MRA was highly sensitive for detection of patent aneurysm components, and at least as sensitive as CE-MRA. Residual aneurysm patency seems to be better visualized with MRA than with DSA in some cases.     

High-resolution, time-resolved MRA provides superior definition of lower-extremity arterial segments compared to 2D time-of-flight imaging

PURPOSE: To evaluate a novel time-resolved contrast-enhanced (CE) projection reconstruction (PR) magnetic resonance angiography (MRA) method for identifying potential bypass graft target vessels in patients with Class II-IV peripheral vascular disease. MATERIALS AND METHODS: Twenty patients (M:F = 15:5, mean age = 58 years, range = 48-83 years), were recruited from routine MRA referrals. All imaging was performed on a 1.5 T MRI system with fast gradients (Signa LX; GE Healthcare, Waukesha, WI). Images were acquired with a novel technique that combined undersampled PR with a time-resolved acquisition to yield an MRA method with high temporal and spatial resolution. The method is called PR hyper time-resolved imaging of contrast kinetics (PR-hyperTRICKS). Quantitative and qualitative analyses were used to compare two-dimensional (2D) time-of-flight (TOF) and PR-hyperTRICKS in 13 arterial segments per lower extremity. Statistical analysis was performed with the Wilcoxon signed-rank test. RESULTS: Fifteen percent (77/517) of the vessels were scored as missing or nondiagnostic with 2D TOF, but were scored as diagnostic with PR-hyperTRICKS. Image quality was superior with PR-hyperTRICKS vs. 2D TOF (on a four-point scale, mean rank = 3.3 +/- 1.2 vs. 2.9 +/- 1.2, P < 0.0001). PR-hyperTRICKS produced images with high contrast-to-noise ratios (CNR) and high spatial and temporal resolution. 2D TOF images were of inferior quality due to moderate spatial resolution, inferior CNR, greater flow-related artifacts, and absence of temporal resolution. CONCLUSION: PR-hyperTRICKS provides superior preoperative assessment of lower limb ischemia compared to 2D TOF.