肾动脉狭窄:肾动脉非增强MRA与增强MRA对照研究

目的本研究目的主要是探讨稳态自由进动(SSFP)非对比增强MRA(非增强-MRA)和传统的对比增强MRA(CE-MRA)对肾动脉狭窄(RAS)评价的价值。方法回顾     

Renal artery stenosis: comparative assessment by unenhanced renal artery MRA versus contrast-enhanced MRA

Objectives  

To evaluate steady-state free precession (SSFP) non-contrast-enhanced MR angiography (Unenhanced-MRA) versus conventional contrast-enhanced MR angiography (CE-MRA) in the detection of renal artery stenosis (RAS).     

Quiescent‐interval single‐shot unenhanced magnetic resonance angiography of peripheral vascular disease: Technical considerations and clinical feasibility

We performed technical optimization followed by a pilot clinical study of quiescent‐interval single‐shot MR angiography for peripheral vascular disease. Quiescent‐interval single‐shot MR angiography acquires data using a modified electrocardiographic (ECG)‐triggered, fat suppressed, two‐dimensional, balanced steady‐state, free precession pulse sequence incorporating slice‐selective saturation and a quiescent interval for maximal enhancement of inflowing blood. Following optimization at 1.5 T, a pilot study was performed in patients with peripheral vascular disease, using contrast‐enhanced MR angiography as the reference standard. The optimized sequence used a quiescent interval of 228 ms, α/2 catalyzation of the steady‐state magnetization, and center‐to‐out partial Fourier acquisition with parallel acceleration factor of 2. Spatial resolution was 2‐3mm along the slice direction and 0.7‐1mm in‐plane before interpolation. Excluding stented arterial segments, the sensitivity, specificity, and positive and negative predictive values of quiescent‐interval single‐shot MR angiography for arterial narrowing greater than 50% or occlusion were 92.2%, 94.9%, 83.9%, and 97.7%, respectively. Quiescent‐interval single‐shot MR angiography provided robust depiction of normal peripheral arterial anatomy and peripheral vascular disease in less than 10 min, without the need to tailor the technique for individual patients. Moreover, the technique provides consistent image quality in the pelvic region despite the presence of respiratory and bowel motion. Magn Reson Med 63:951–958, 2010. © 2010 Wiley‐Liss, Inc.     

Performance of unenhanced respiratory-gated 3D SSFP MRA to depict hepatic and visceral artery anatomy and variants

Objectives

To prospectively evaluate the performance of unenhanced respiratory-gated magnetization-prepared 3D-SSFP inversion recovery MRA (unenhanced-MRA) to depict hepatic and visceral artery anatomy and variants in comparison to contrast-enhanced dynamic gradient-echo MRI (CE-MRI) and to digital subtraction angiography (DSA).

Methods

Eighty-four patients (55.6 ± 12.4 years) were imaged with CE-MRI (TR/TE 3.5/1.7 ms, TI 1.7 ms, flip-angle 15°) and unenhanced-MRA (TR/TE 4.4/2.2 ms, TI 200 ms, flip-angle 90°). Two independent readers assessed image quality of hepatic and visceral arteries on a 4-point-scale. Vessel contrast was measured by a third reader. In 28 patients arterial anatomy was compared to DSA.

Results

Interobserver agreement regarding image quality was good for CE-MRI (κ = 0.77) and excellent for unenhanced-MRA (κ = 0.83). Unenhanced-MRA yielded diagnostic image quality in 71.6% of all vessels, whereas CE-MRI provided diagnostic image quality in 90.6% (p < 0.001). Vessel-based image quality was significantly superior for all vessels at CE-MRI compared to unenhanced-MRA (p < 0.01). Vessel contrast was similar among both sequences (p = 0.15). Compared to DSA, CE-MRI and unenhanced-MRA yielded equal accuracy of 92.9–96.4% for depiction of hepatic and visceral artery variants (p = 0.93).

Conclusions

Unenhanced-MRA provides diagnostic image quality in 72% of hepatic and visceral arteries with no significant difference in vessel contrast and similar accuracy to CE-MRI for depiction of hepatic and visceral anatomy.     

Quadruple inversion-recovery b-SSFP MRA of the abdomen: Initial clinical validation

The purpose of this study is to assess the image quality and diagnostic accuracy of non-contrast quadruple inversion-recovery balanced-SSFP MRA (QIR MRA) for detection of aortoiliac disease in a clinical population. QIR MRA was performed in 26 patients referred for routine clinical gadolinium-enhanced MRA (Gd-MRA) for known or suspected aortoiliac disease. Non-contrast images were independently evaluated for image quality and degree of stenosis by two radiologists, using consensus Gd-MRA as the reference standard. Hemodynamically significant stenosis (≥50%) was found in 10% (22/226) of all evaluable segments on Gd-MRA. The sensitivity and specificity for stenosis evaluation by QIR MRA for the two readers were 86%/86% and 95%/93% respectively. Negative predictive value and positive predictive value were 98%/98% and 63%/53% respectively. For stenosis evaluation of the aortoiliac region QIR MRA showed good agreement with the reference standard with high negative predictive value and a tendency to overestimate mild disease presumably due to the flow-dependence of the technique. QIR MRA could be a reasonable alternative to Gd-MRA for ruling out stenosis when contrast is contraindicated due to impaired kidney function or in patients who undergo abdominal MRA for screening purposes. Further work is necessary to improve performance and justify routine clinical use.     

Comparison between multi-shot gradient echo EPI and balanced SSFP in unenhanced 3T MRA of thoracic aorta in healthy volunteers

PurposeThe purpose of this study was to compare scan time and image quality between magnetic resonance angiography (MRA) of the thoracic aorta using a multi-shot gradient echo planar imaging (MSG-EPI) and MRA using balanced steady-state free precession (b-SSFP).Materials and methodsHealthy volunteers (n = 17) underwent unenhanced thoracic aorta MRA using balanced steady-state free precession (b-SSFP) and MSG-EPI sequences on a 3T MRI. The acquisition time, total scan time, signal-to-noise ratio (SNR) of the thoracic aorta, and the coefficient of variation (CV) of thoracic aorta were compared with paired t-tests. Two radiologists independently recorded the images’ contrast, noise, sharpness, artifacts, and overall quality on a 4-point scale.ResultsThe acquisition time was 36.2% shorter for MSG-EPI than b-SSFP (115.5 ± 14.4 vs 181.0 ± 14.9 s, p < 0.01). The total scan time was 40.4% shorter for MSG-EPI than b-SSFP (272 ± 78 vs 456 ± 144 s, p < 0.01). There was no significant difference in mean SNR between MSG-EPI and b-SSFP scans (17.3 ± 3.6 vs 15.2 ± 4.3, p = 0.08). The CV was significantly lower for MSG-EPI than b-SSFP (0.2 ± 0.1 vs. 0.5 ± 0.2, p < 0.01). All qualitative scores except for image noise were significantly higher in MSG-EPI than b-SSFP scans (p < 0.05).ConclusionThe MSG-EPI sequence is a promising technique for shortening scan time and yielding more homogenous image quality in MRA of thoracic aorta on 3T scanners compared with the b-SSFP.     

Time-resolved projection MRA: clinical application in intracranial vascular malformations

We report preliminary results of imaging intracranial vascular malformations with time-resolved projection MRA after a bolus injection of contrast median before and after endovascular treatment. Projection angiograms are acquired with a slice-selective snapshot FLASH sequence with a time resolution of two images per second, 40–60 images being acquired consecutively after bolus injection of 15 ml Gd-DTPA. Postprocessing of images in 2D projection MRA by correlation analysis offers several advantages with significant improvement of signal-to-noise, leading to adequate anatomical resolution. Subsecond projection MRA is a reliable technique for imaging intracranial vessels and gives information about the haemodynamics of vascular malformations. Received: 24 April 1999/Accepted: 12 July 1999     

3D nongadolinium-enhanced ECG-gated MRA of the distal lower extremities: preliminary clinical experience

PURPOSE: To report our initial experience implementing a noncontrast-enhanced electrocardiograph (ECG) gated fast spin echo magnetic resonance angiography (MRA) technique for assessment of the calf arteries. MATERIALS AND METHODS: Noncontrast MRA images of 36 clinical patients examined over a 6-month period were evaluated by two radiologists for length and degree of stenosis of arterial segments. Diagnostic confidence in the technique was also recorded. The reference standard was a consensus reading by both radiologists using the noncontrast technique combined with two gadolinium-enhanced techniques: bolus-chase and time-resolved imaging. RESULTS: For stenosis evaluation the noncontrast technique demonstrated accuracy 79.4% (1083/1364), sensitivity 85.4% (437/512), and specificity 75.8% (646/852). The sequence demonstrated high negative predictive value (92.3%, 646/700). The technique had serious artifacts leading to poor diagnostic confidence in 17 patients (47.2%). These included motion (n = 7) and artifacts specific to the sequence, including inaccurate trigger delays (n = 5), linear artifact (n = 7), and vessel blurring (n = 5). When only patients in whom there was satisfactory diagnostic confidence were considered, accuracy, sensitivity, and negative predictive value were 92.2% (661/717), 92.4% (158/171), and 97.5% (503/516), respectively. CONCLUSION: Our results indicate that when technically successful, noncontrast-enhanced MRA using ECG-gated fast spin echo can provide accurate imaging of the calf and pedal arteries. However, further development and optimization are needed to improve the robustness of the technique.     

MRA of intracranial aneurysm models: a comparison of contrast-enhanced three-dimensional MRA with time-of-flight MRA

PURPOSE: The purpose of our study was to compare contrast-enhanced 3D MR angiography (MRA) using ultrafast spoiled gradient-recalled acquisition in the steady state (SPGR) with 2D and 3D time-of-flight (TOF) MRA for visualization of intracranial lateral saccular aneurysm models. METHOD: We used lateral saccular aneurysm models with a height of 10 mm and neck sizes of 2.5 and 10 mm. Imaging was performed using a 1.5 T MR system with a head coil. Contrast-enhanced 3D MR angiograms were obtained using 3D ultrafast SPGR sequence with and without the MR Smartprep technique. Two-dimensional and 3D TOF MR angiograms were also obtained. RESULTS: Contrast-enhanced multiphase 3D MR angiograms taken every 5 s after injection of contrast medium proved superior to the other MRA techniques for delineating lateral saccular aneurysm models. Contrast-enhanced 3D MRA images taken with inadequate delay after MR Smartprep trigger showed poor visualization of the aneurysm model. CONCLUSION: Use of contrast-enhanced multiphase 3D MRA with ultrafast SPGR with shorter TR and TE resulted in clear images of the lateral saccular aneurysm model.     

Quantification of intracranial internal carotid artery calcification on brain unenhanced CT: evaluation of its feasibility and assessment of the reliability of visual grading scales

Objectives

Previous studies have evaluated intracranial internal carotid artery calcifications (ICACs) qualitatively using different visual grading scales, which could lead to inconsistent results. The purpose of this study was to evaluate the feasibility of ICAC volume measurement and to correlate the volume with visual grading scales.

Methods

We included 49 patients (>50?years) who underwent unenhanced cranial CT. Two observers evaluated four visual grading scales and measured ICAC volumes semi-automatically, and interobserver agreements were assessed. Differences in ICAC volume between visual grades of each scale were tested. The relationship between the visual grading and volume was assessed.

Results

Interobserver agreements ranged from 0.841 to 0.901 for visual grading and 0.997 for volume measurement. Mean volumes were not significantly different between the visual grades (P?>?0.05) except when comparing grade 4 with the other grades. The grades of each visual grading correlated well with ICAC volumes (Spearman's ???=?0.849?C0.881, P?<?0.001). The relationship between the visual grades and volume was described by a quadratic model (R ², 0.31?C0.50, P?<?0.01).

Conclusions

ICAC volume measurement is feasible and reproducible, whereas visual grades poorly reflect the actual volume; therefore, volume measurement may be warranted for future research.

Key Points

? Computed tomography provides unique information about vascular calcification. ? Volume measurement of intracranial carotid artery calcification is feasible and reproducible. ? Visual grades poorly reflect the volume of intracranial carotid artery calcification. ? Quantification of intracranial carotid artery calcification is warranted for future research.     

小腿3.0 T MRA:非增强心电门控流动依赖MRA、连续移床MRA和时间分辨MRA的对比研究

目的对一组临床病人行小腿3.0TMRA检查分析,旨在比较3D非增强心电门控流动依赖型MRA(NE-MRA)、连续移床(CTM)MRA和时间分辨TWIST-MRA的应用价值。方法 36例外周动脉硬化闭塞症(PAOD)病人(Ⅱ～Ⅳ     

Dual-energy CT of the brain: Comparison between DECT angiography-derived virtual unenhanced images and true unenhanced images in the detection of intracranial haemorrhage

Objective

To evaluate the diagnostic performance of virtual non-contrast (VNC) images in detecting intracranial haemorrhages (ICHs).

Methods

Sixty-seven consecutive patients with and 67 without ICH who underwent unenhanced brain CT and DECT angiography were included. Two radiologists independently evaluated VNC and true non-contrast (TNC) images for ICH presence and type. Inter-observer agreement for VNC and TNC image evaluation was calculated. Sensitivity and specificity of VNC images for ICH detection were calculated using Fisher’s exact test. VNC and TNC images were compared for ICH extent (qualitatively and quantitatively) and conspicuity assessment.

Results

On TNC images 116 different haemorrhages were detected in 67 patients. Inter-observer agreement ranged from 0.98–1.00 for TNC images and from 0.86–1.00 for VNC images. VNC sensitivity ranged from 0.90–1, according to the different ICH types, and specificity from 0.97–1. Qualitatively, ICH extent was underestimated on VNC images in 11.9% of cases. Haemorrhage volume did not show statistically significant differences between VNC and TNC images. Mean haemorrhage conspicuity was significantly lower on VNC images than on TNC images for both readers (p?<?0.001).

Conclusion

VNC images are accurate for ICH detection. Haemorrhages are less conspicuous on VNC images and their extent may be underestimated.

Key points

? VNC images represent a reproducible tool for detecting ICH.? ICH can be identified on VNC images with high sensitivity and specificity.? Intracranial haemorrhages are less conspicuous on VNC images than on TNC images.? Intracranial haemorrhages extent may be underestimated on VNC images.

     

MRA在诊断血管疾病方面的临床应用

血管中流动血液的MR信号取决于其流速,这些流动的血液和周围组织有着明显的MR影像差异,根据这一现象可用于磁共振血管造影(magneticresonance angiography,MRA),也可用于其流速的测量。目前,这种不用造影剂的非侵入性MRA已在临床上得到了广泛的应用。下面简单介绍MRA的基本原理、主要技术和在临床上的应用情况。1 MRA基本原理和主要技术MRA的基本原理是利用血管内流动的血液与周围静止组织的这一明显差别,使流动的血液成为高信号,让静止的组织成为低信号或无信号。然后利用计算机后处理技术以二维或三维的立体图像来显示出某一部分…     

Spin-labeling angiography of the carotids by presaturation and simplified adiabatic inversion

A new adiabatic inversion pulse is tested for a spin-labeling subtraction angiography method. Adiabatic nature of the pulse is achieved by ramping the gradient during the RF pulse. In addition, with cardiac triggering, any irregularity of the heartbeat would decrease cancellation of the static tissue after subtraction. A 90 degree presaturation pulse applied to prevent this suppresses the background intensity from the static tissue by a factor greater than 2. Slice angiograms of carotid arteries are presented.