32接收通道并行采集全身MR血管成像技术的临床应用初探

目的初步探讨32接收通道并行采集全身MR血管成像技术在系统性动脉病变中的临床使用价值。方法30例接受三维增强全身MR血管成像(3D CE MRA)检查。仪器为1.5 T成像仪(M agnetom Avanto,S iem ens AG)配置32个接收通道和并行采集技术。病例包括临床诊断或怀疑的周围动脉闭塞性病变(PAOD)17例,多发性大动脉炎3例,结节性多动脉炎1例,Stanford B型夹层4例以及胸和(或)腹主动脉瘤5例。共使用68个表面线圈单元包绕患者全身。3D CE MRA共分4段采集,每段视野(FOV)为375 mm×500 mm,通过自动移床分段扫描,第1~3段使用并行采集技术。对比剂用量为0.3 mmol/kg,分两相注射,前0.15 mmol/kg注射流率为1.3 m l/s,后0.15 mmol/kg注射流率为0.6 m l/s。总的扫描长度约188 cm,覆盖颈动脉到小腿动脉分支(不包括颅内动脉和冠状动脉)。分析每段动脉的图像质量、各种动脉血管病变的显示效果,并同其他影像检查对照(包括DSA 9例,CT血管造影8例,单段MRA 1例)。结果所有病例均顺利完成全身3D CE MRA检查。动脉图像质量好,平均检查时间为17.4 m in。17例PAOD患者中发现70段下肢动脉病变,其中7例3D CE MRA显示了除下肢动脉病变以外的其他部位动脉狭窄。4例血管炎患者3D CE MRA显示全身多处动脉管腔不规则、狭窄或闭塞、动脉瘤以及侧支血管。3D CE MRA还清楚显示夹层和动脉瘤的严重程度和范围。与其他血管成像技术比较,除1例3D CE MRA高估血管狭窄程度外,其他均相符合。结论配置了32个接收通道和并行采集技术的新型MR成像仪能顺利完成全身3D CE MRA检查,该法操作简便,检查时间短,在全面显示各种系统性动脉病变的临床使用方面有重要价值。     

MR血管成像诊断脊髓动静脉畸形的价值

目的 探讨磁共振血管成像(包括快速3D增强MRA技术和常规MRA)在脊髓动静脉畸形的诊断价值.方法 回顾分析10例脊髓动静脉畸形MRA资料,均由选择性脊髓血管造影确诊,全部病例均使用3D增强MRA技术(CE-MRA),头颈部另外还使用常规MRA(3D-TOF MRA).结果 髓内动静脉畸形3例,AVM血管巢的MRA表现为血管粗细不一,扭曲成团,并显示1条或多条供血动脉及增粗的引流静脉.髓外硬膜内动静脉畸形5例,其中3例为AVM,MRA显示有血管巢、供血动脉及引流静脉;2例为AVF,MRA可以显示供血动脉及引流静脉,并可推断瘘口的位置.硬脊膜动静脉瘘2例,MRA只表现为髓周血管扩张.结论 MRA不仅可以对脊髓动静脉畸形作定性诊断,而且还可以显示病灶的内部结构,已成为无创性诊断脊髓血管畸形的理想方法.     

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。     

脊髓血管畸形的快速增强MRA与DSA诊断的比较研究

目的 评价椭圆形中心顺序(elliptic centric ordered)的快速增强磁共振血管成像(fastcontrast-enhanced MR angiography,CE-MRA)在脊髓血管畸形中的诊断和临床应用价值.方法 25例临床怀疑脊髓血管畸形的患者在1.5T MR机上接受了椭圆形中心顺序的快速CE-MRA检查,所有病例行选择性全脊椎动脉造影,18例施行了外科手术,其中2例术前行血管内栓塞,术后MRA随访了10例;以选择性全脊椎动脉造影为金标准,就病变诊断、供养动脉起源、供养动脉、瘘口或瘤巢、引流静脉和血管的图像质量(包括血管的连续性、强化程度和清晰度)进行MRA和DSA的比较.结果 经外科手术证实18例,包括脊髓动静脉畸形3例、髓周动静脉瘘5例、硬膜动静脉瘘7例、椎旁动静脉瘘1例、自发性椎管内硬膜外血肿2例;MRA显示脊髓血管畸形的诊断、供养动脉起源、供养动脉、瘤巢或瘘口、引流静脉与DSA的符合率分别为93.8%、92%、96.2%、100%和100%,MRA显示血管强化和清晰度类似于DSA(P＞0.05),DSA显示血管的连续性优于MRA(P＜0.05);9例MRA未见椎管内异常血管,与DSA完全符合.术后MRA随访的10例原异常血管未再显示.结论 椭圆形中心顺序的快速CE-MRA能够初步诊断脊髓血管畸形的亚型,能够显示脊髓血管畸形的供养动脉起源、供养动脉、瘤巢或瘘口、引流静脉,能够指导选择性脊椎动脉造影和手术治疗,是脊髓血管畸形术前诊断和术后随访的重要手段.     

相位对比法MRA在颅内静脉窦病变中的应用

目的 评价相位对比法(PC)磁共振血管造影(MRA)对颅内静脉窦病变的显示能力及其应用价值.方法 累及静脉窦的病变共44例.动静脉畸形(AVM)19例,动静脉瘘(AVF)6例,静脉窦血栓形成(DST)2例,脑膜瘤16例,结核1例.其中行2DPC法MRA检查的息者共35例,3D PC法MRA检查6例,3例同时行2D PC法和3D PC法检查.9例同时行DSA检查.结果 PC法MRA对AVM供血动脉的显示不如3D TOF法,但能更好地显示引流静脉的数量、方向、受累及静脉窦的形态,瘤巢的信号也较3D TOF法高;PC法MRA能清晰显示Galen静脉型动静脉瘘(AVF)扩张的Galen静脉和引流静脉以及海绵窦动静脉瘘(CS-DAVF)时"血管湖"状扩张的海绵窦和眼上静脉、蝶顶窦、岩上窦、岩下窦等引流静脉;静脉窦血栓形成时Pc法MRA出现血流缺损和引流静脉的扩张;PC法MRA能显示镰旁和后颅窝脑膜瘤和结核灶造成的静脉窦移位、狭窄、闭塞等形态的改变.结论 结合常规MBI检查,PC法MRA能直观、清晰地显示静脉窦受病变累及时其形态特点.     

无创性脊髓血管成像诊断脊髓血管畸形的临床应用价值

目的 通过与脊髓DSA及手术对比,初步探讨256层MSCT全脊髓血管成像(CTA)及3.0TMR脊髓血管动态增强扫描(CE-MRA)诊断脊髓血管畸形的临床应用价值.方法 17例临床表现及MR平扫疑诊为脊髓血管病的患者,全部行CTA检查,其中10例行MRA检查,15例在CT或MR检查3～5d后行DSA检查,8例患者经手术治疗.将其CTA、MRA、DSA及手术结果进行对比.结果行CTA检查的17例患者中,16例较好地显示了异常血管病变的范围,其中7例诊断为硬脊膜 动静脉瘘,7例为髓周动静脉瘘,2例为脊髓动静脉畸形,与DSA或手术诊断一致,1例无法做出诊断.其中12例准确判定供血动脉,12例准确显示瘘口位置.行MRA检查的10例患者中,7例准确诊断供血动脉及瘘口位置,与DSA或手术结果一致;其余3例DSA检查阴性.结论 256层MSCT全脊髓CTA及3.0T MR CE-MRA能安全、无创、快速、清晰地显示脊髓血管畸形的病变范围、供血动脉及瘘口的位置,缩短DSA诊疗时间,在脊髓血管畸形的诊断、协助制订治疗方案及术后随访方面起到重要作用.     

硬脑膜动静脉瘘MRI的诊断价值

目的探讨MRI、磁共振血管成像（MRA）在硬脑膜动静脉瘘的诊断及治疗评估中的作用。资料与方法回顾性分析14例硬脑膜动静脉瘘的临床资料及影像表现。所有患者术前均行头颅MRI、MRA及数字减影血管造影（DSA）,其中8例治疗后行MRI及MRA复查,对比分析患者MRI及MRA影像表现。结果MRI、MRA均能明确显示出增粗的供血动脉及扩张的引流静脉;同时显示脑出血（3例）,脑血栓（1例）,脑水肿（2例）,脑组织萎缩（1例）及栓塞物（治疗所置）（2例）等;8例经治疗后复查,MRI示7例扩张血管消失或缩小。结论MRI、MRA在硬脑膜动静脉瘘的诊断和术后评估中起着重要的作用。     

3D-TOF MRA及SWI对脑血管畸形的对照研究

目的:通过分析脑动静脉畸形和海绵状血管瘤的的3D-TOF MRA及SWI磁共振表现,探讨3D-TOF MRA及SWI对脑血管畸形的诊断价值。方法:对我院收治的44例血管畸形进行高场磁共振成像,并加扫3D-TOF MRA及SWI序列,其中26例海绵状血管瘤、18例动静脉畸形。通过分析SW I和3D-TOF-MRA技术对脑血管畸形的显示情况,比较二者对脑血管畸形的检出率以及细微特征的鉴别能力等。结果:3D-TOF MRA可以清晰显示动静脉畸形的部位、大小、输入动脉的来源、输出静脉的去向等;海绵状血管瘤MRA检查均未见异常供血动脉,病灶内无异常流空信号。SWI可清晰显示海绵状血管瘤,病灶的数目及范围较常规序列增大;SWI只能显示动静脉畸形迂曲的小静脉,但不能直观显示畸形血管团的全貌及输入动脉等粗大血管的情况。结论:3D-TOF MRA技术对于AVM之类高流速低阻力的血管畸形的显示具有独特的价值,而SWI技术则对于海绵状血管瘤等小血管或低流速的血管畸形的显示具有明显的优势。     

磁共振血管成像在脑血管病中的诊断价值

目的:探讨三维时间飞跃法MR血管成像(3D TOF MRA)和三维增强MR血管造影(3D CE-MRA)检查技术,评价两种方法对脑血管病的诊断价值。方法:磁共振血管成像检查150例,全部行3D TOF MRA检查;9例进行3D CE-MRA检查,钆对比剂(Gd-DTPA)0.2mmol/kg,注射流率3ml/s,增强前、增强后动脉期及静脉期3次扫描;所有MRA图像进行三维重建,同期12例行DSA检查。常规MRI包括横断面T1WI、T2WI,矢状面T1WI。结果:56例中颅内血管显示正常56例,颅内动脉狭窄或闭塞者46例,颅内动脉瘤22例,颅内动静脉畸形21例,颈内动脉海绵窦瘘3例,烟雾病(moyamoya dis-ease)2例。结论:3D TOF MRA和3D CE-MRA是无创、快速、有效的检查技术,对诊断脑血管病有较高的价值,结合原始图像和常规MRI检查,一次检查即能为临床提供较为全面的信息,可作为脑血管病的筛选和首选诊断方法。     

多层螺旋CT脊髓血管成像的初步研究

目的 探讨多层螺旋CT血管成像（CTA）在脊髓血管病变诊断中的价值。方法 对MRI及临床表现符合脊髓血管病的10例患者行CTA。其中7例于1周内行DSA检查，4例行手术治疗。CT扫描采用Toshiba Aquilion 64层CT扫描机，采用多平面重组、曲面重组、最大密度投影、容积重组方法进行图像后处理。主要从分型、显示病变范围、供血动脉、瘘口及引流静脉等方面对CTA图像进行评价，并与DSA及手术结果对照。结果10例患者CTA均显示了脊髓血管畸形；3例为髓内动静脉畸形，2例为髓周动静脉瘘，5例为硬脊膜动静脉瘘。所有病例均清楚显示病变范围及引流静脉，除1例患者有2根血管为假阳性，其余患者均清楚显示供血动脉并与DSA检查结果一致。结论 CTA对脊髓血管病变的诊断有较大价值，可作为DSA检查前的筛选检查。     

透视触发并行采集高分辨率三维增强颈动脉磁共振血管成像术

目的评估透视触发和并行采集技术用于高分辨率三维增强颈动脉磁共振血管成像术(3DCEMRA)的可行性。方法80个临床诊断或怀疑颈动脉狭窄的病人接受3DCEMRA检查。使用透视触发软件触发启动颈动脉3DCEMRA扫描,同时采用K空间椭圆形中心填充法和加速因子为2的并行采集技术。对显示的各段动脉和有无静脉早期显影做分析。动脉狭窄分成动脉管壁不规则、轻度狭窄、严重狭窄和闭塞。颈动脉3DCEMRA的显示结果与其他检查结果做了对照。结果所有病例均顺利触发和完成颈动脉3DCEMRA检查。3DCEMRA显示了80例病人总共800支动脉段(100%显示率),所有病例在动脉显示区域内静脉均未显影或显影很淡,对诊断不构成影响。结果显示有680段动脉正常、41段动脉管壁不规则、24段动脉轻度狭窄、51段严重狭窄和4段闭塞。另外10段颈动脉狭窄处溃疡形成,12例患者除见颈动脉狭窄以外,还发现合并椎动脉和/或锁骨下动脉狭窄。36例病例,与其他血管成像技术作了比较,3DCEMRA的检查结果与之完全符合,未出现高估或低估血管狭窄程度。结论透视触发并行采集高分辨率3DCEMRA简单可行,成像时间短,空间分辨率高,能清楚显示颈动脉,它将在颈动脉狭窄的诊断中起重要作用。     

Time-resolved echo-shared parallel MRA of the lung: observer preference study of image quality in comparison with non-echo-shared sequences

The aim of this study was to evaluate the image quality of time-resolved echo-shared parallel MRA of the lung. The pulmonary vasculature of nine patients (seven females, two males; median age: 44 years) with pulmonary disease was examined using a time-resolved MRA sequence combining echo sharing with parallel imaging (time-resolved echo-shared angiography technique, or TREAT). The sharpness of the vessel borders, conspicuousness of peripheral lung vessels, artifact level, and overall image quality of TREAT was assessed independently by four readers in a side-by-side comparison with non-echo-shared time-resolved parallel MRA data (pMRA) previously acquired in the same patients. Furthermore, the SNR of pulmonary arteries (PA) and veins (PV) achieved with both pulse sequences was compared. The mean voxel size of TREAT MRA was decreased by 24% compared with the non-echo-shared MRA. Regarding the sharpness of the vessel borders, conspicuousness of peripheral lung vessels, and overall image quality the TREAT sequence was rated superior in 75–76% of all cases. If the TREAT images were preferred over the pMRA images, the advantage was rated as major in 61-71% of all cases. The level of artifacts was not increased with the TREAT sequence. The mean interobserver agreement for all categories ranged between fair (artifact level) and good (overall image quality). The maximum SNR of TREAT did not differ from non-echo-shared parallel MRA (PA: TREAT: 273±45; pMRA: 280±71; PV: TREAT: 273±33; pMRA: 258±62). TREAT achieves a higher spatial resolution than non-echo-shared parallel MRA which is also perceived as an improved image quality.     

Time-resolved contrast-enhanced three-dimensional magnetic resonance angiography of the chest: combination of parallel imaging with view sharing (TREAT)

RATIONALE AND OBJECTIVES: In view sharing, some parts of k-space are updated more often than others, leading to an effective shortening of the total acquisition time. Undersampling of high-frequency k-space data, however, can result in artifacts at the edges of blood vessels, especially during the rapid signal intensity changes. The objective of this study was to evaluate a new time-resolved echo-shared angiographic technique (TREAT) combining parallel imaging with view sharing. First, the presence of artifacts arising from different temporal interpolation schemes was evaluated in simulations of the point spread function. Second, the image quality and presence of artifacts of time-resolved parallel three-dimensional magnetic resonance angiography (3D MRA) of the chest, acquired with and without view sharing, was assessed in a clinical study of patients with cardiovascular or pulmonary disease. MATERIALS AND METHODS: Using parameters from a time-resolved parallel 3D MRA sequence without view sharing (parallel MRA), giving a 33% increase in spatial resolution, our simulations have revealed that k-space segmentation in 3 regions provides acceptable artifacts. Thirty-six consecutive patients (mean age, 50 +/- 16 years; 15 females, 22 males) were examined in a clinical study with TREAT. The image data were compared with that of a group of 31 consecutive patients (mean age, 46 +/- 19 years; 12 females, 19 males) examined with a conventional time-resolved parallel MRA sequence without view sharing (parallel MRA). The image quality and presence of artifacts was assessed in a blind comparison by 2 radiologists in consensus using MPR and MIP reconstructions. Furthermore, the peak SNR of the pulmonary artery and aorta was compared between both MRA sequences. RESULTS: The image quality of TREAT was rated significantly higher than that of the parallel MRA sequence without view sharing: depending on the orientation of MPR and MIP reconstructions, an excellent image quality was found in 69-89% with TREAT and in 45-71% with the parallel MRA protocol without view sharing, respectively. The presence of artifacts was equal with both sequences. CONCLUSION: View sharing can be successfully combined with other acceleration techniques, such as parallel imaging. TREAT allows the assessment of the thoracic vasculature with a high temporal and spatial resolution.     

Time-resolved contrast-enhanced magnetic resonance angiography of the hand with parallel imaging and view sharing: initial experience

We sought to compare a three-dimensional, contrast-enhanced, magnetic resonance angiogram (3D CE MRA) sequence combining parallel-imaging (generalised autocalibrating partially parallel acquisitions (GRAPPA)) with a time-resolved echo-shared angiographic technique (TREAT) in an intraindividual comparison to a standard 3D MRA sequence. Four healthy volunteers (27–32 years), and 11 patients (11–82 years) with vascular pathologies of the hand were examined on a 1.5-Tesla (T) MR system (Magnetom Avanto, Siemens, Erlangen, Germany) using two multichannel receiver coils. Following automatic injection (flow rate 2.5 cc/s) of 0.1 mmol/kg gadoterate (Dotarem, Guerbet, Roissy, France), 32 consecutive 3D data sets were collected with the TREAT sequence (TR/TE: 4.02/1.31 ms, FA: 10°, GRAPPA acceleration factor: R=2, TREAT factor: 5, voxel size: 1.0×0.7×1.3 mm³) and a T1-wwighted 3D gradient-echo sequence (TR/TE: 5.3/1.57 ms, FA: 30°, GRAPPA acceleration factor: 2, voxel size: 0.71×0.71×0.71 mm^3,). MR data sets were evaluated and compared for image quality and visualisation of vascular details. In the volunteer group, all MR imaging was successful while technical problems prevented acquisition of the standard protocol in two patients. For the corresponding segments, the number of visible segments was equal on both sequences. Overall image quality was significantly better on the standard protocol than on the TREAT protocol. TREAT MRA provided functional information in lesions with rapid blood flow, e.g. detection of feeding and draining vessels in an haemangioma. TREAT-MRA is a robust technique that combines morphological and functional information of the hand vasculature and deals with the very special physiological demands of vascular lesions, such as quick arteriovenous transit time.     

Peripheral arterial disease. Contrast-enhanced 3D MR angiography of the lower leg and foot compared with conventional angiography

PURPOSE: To determine whether contrast-enhanced 3D MR angiography (CE MRA) could replace digital subtraction angiography (DSA) for the evaluation of atherosclerotic peripheral vascular disease of the lower leg and foot. MATERIAL AND METHODS: Thirty-five patients with symptoms of atherosclerotic disease of the leg were examined prospectively with CE MRA of the foot and the lower legs as well as with DSA from the aorta to the pedal arches. The MRA technique was focused on optimal imaging of the arteries of the foot. RESULTS: The agreement between CE MRA and DSA for grading of stenosis was moderate to good (weighted kappa-values 0.48-0.80). The sensitivity of CE MRA for detection of significant stenosis (> or = 50%) was 92% and the specificity was 64% with DSA as gold standard. CONCLUSION: CE MRA is a fairly accurate method for the demonstration of atherosclerotic disease below the knee including the pedal arches. It can replace DSA for the assessment of distal arteries in patients with impaired renal function. However, image quality and resolution still needs to be improved before CE MRA can become the method of choice in all patients.     

肾动脉狭窄的三维增强磁共振血管成像诊断

目的:评价高分辨力三维增强磁共振血管成像术(3DCEMRA)对肾动脉狭窄的显示准确性。方法:对30例临床诊断或怀疑肾动脉狭窄患者进行高分辨力肾动脉3DCEMRA检查,分析所有患者的肾动脉和副肾动脉显示质量和病变显示情况,并与DSA做对照。结果:3DCEMRA显示了30例患者总共59支肾动脉主干(1例为单支移植肾动脉),显示率为100%。3DCEMRA显示4支副肾动脉,显示率100%。肾动脉段级分支的显示率为49%。所有病例在动脉显示区域内静脉均未显影或显影淡,对诊断不构成影响。DSA共显示59支肾动脉主干和4支副肾动脉(以63支计算),59支主干中2支闭塞,8支重度狭窄,11支中度狭窄,10支轻度狭窄,28支肾动脉主干和4支副肾动脉都正常。3DCEMRA除把2支轻度狭窄估为中度狭窄,1支中度狭窄估为重度狭窄外,其它结果都同DSA一致,故3DCEMRA显示肾动脉主干和副肾动脉狭窄程度超过50%的有血液动力学意义的明显狭窄的敏感性和特异性分别为100%和95%,阳性预测值为91%,阴性预测值为100%。结论:高分辨力肾动脉3DCEMRA能准确检出肾动脉主干和副肾动脉狭窄,并能较好判断其狭窄程度。     

Intracranial time-resolved contrast-enhanced MR angiography at 3T

BACKGROUND AND PURPOSE: A method is presented for high-temporal-resolution MR angiography (MRA) using a combination of undersampling strategies and a high-field (3T) scanner. Currently, the evaluation of cerebrovascular disorders involving arteriovenous shunting or retrograde flow is accomplished with conventional radiographic digital subtraction angiography, because of its high spatial and temporal resolutions. Multiphase MRA could potentially provide the same diagnostic information noninvasively, though this is technically challenging because of the inherent trade-off between signal intensity-to-noise ratio (S/N), spatial resolution, and temporal resolution in MR imaging. METHODS: Numerical simulations addressed the choice of imaging parameters at 3T to maximize S/N and the data acquisition rate while staying within specific absorption rate limits. The increase in S/N at 3T was verified in vivo. An imaging protocol was developed with S/N, spatial resolution, and temporal resolution suitable for intracranial angiography. Partial Fourier imaging, parallel imaging, and the time-resolved echo-shared acquisition technique (TREAT) were all used to achieve sufficient undersampling. RESULTS: In 40 volunteers and 10 patients exhibiting arteriovenous malformations or fistulas, intracranial time-resolved contrast-enhanced MRA with high acceleration at high field produced diagnostic-quality images suitable for assessment of pathologies involving arteriovenous shunting or retrograde flow. The technique provided spatial resolution of 1.1 x 1.1 x 2.5 mm and temporal resolution of 2.5 seconds/frame. The combination of several acceleration methods, each with modest acceleration, can provide a high overall acceleration without the artifacts of any one technique becoming too pronounced. CONCLUSION: By taking advantage of the increased S/N provided by 3T magnets over conventional 1.5T magnets and converting this additional S/N into higher temporal resolution through acceleration strategies, intracranial time-resolved MRA becomes feasible.     

Renal arteriography using gadolinium enhanced 3D MR angiography--clinical experience with the technique, its limitations and pitfalls.

Gadolinium enhanced 3D MR angiography (MRA) is becoming a widely accepted technique for imaging the vascular system. We set out to evaluate its accuracy and reliability in visualization of renal arteries in the clinical setting. Gadolinium enhanced MRA was performed in 15 potential live renal donors and 26 patients suspected of having renal artery stenosis who were referred for digital subtraction angiography (DSA). MRA was performed on a 1.5 T MR scanner in a single breath hold. Images from each study were prospectively analysed for demonstration of number of main and accessory renal arteries and degree of renal artery stenosis in a double blind fashion. All the main and accessory arteries were visualized on MRA in the renal donor group, but in one case a branch was not identified owing to breathing artefact. In one case, an extrarenal vascular anomaly was not demonstrated on MRA. In the renal artery stenosis group, sensitivity, specificity and negative predictive values of 96%, 93% and 96% were obtained for clinically significant stenosis (>50%). Gadolinium enhanced MRA proved to be a useful technique in demonstration of renal arterial anatomy and grading of renal artery stenosis. However, we encountered some pitfalls and limitations of the technique during the process. It is important to be aware of these before accepting it as the sole technique in clinical practice.     

Quantitative and qualitative characterization of vascularization and hemodynamics in head and neck tumors with a 3D magnetic resonance time-resolved echo-shared angiographic technique (TREAT)—initial results

The purpose of this paper is to characterize and quantify the vascularization and hemodynamic characteristics of head and neck tumors (HNT) with a dynamic 3D time-resolved echo-shared angiographic technique (TREAT) using the regular contrast agent (CA) bolus. Sixteen patients with HNT underwent 3D-TREAT during the CA administration on a 1.5-T magnetic resonance (MR) scanner. Using a parallel imaging acceleration factor of 2, 20 3D data sets at a temporal resolution of 2.3 s/frame were acquired. The quality of tumor delineation, vascularization type, and enhancement pattern were evaluated. Quantitative assessment included measurement of the contrast-to-noise ratio (CNR), determination of signal-intensity-over-time (SIT) curves, time-to-peak enhancement within the carotid arteries and the tumor, and the delay between both. TREAT was compared to conventional digital subtraction angiography (DSA) in six patients. Tumor delineation with TREAT was very good or good in 11/16 patients, and better with TREAT than with DSA in 3/6 cases. The CNR was significantly different for glomus tumors versus hypovascularized malignant tumors with TREAT (p=0.0001), but not on T1-weighted gradient echo (T1w GE) images. Qualitative assessment of tumor vascularization on dynamic TREAT shows good correlation (r=0.75) to quantitative SIT curves. We conclude that TREAT imaging permits the characterization of tumor vascularity and holds promise as a supplementary diagnostic tool in the differential diagnosis of HNT. H.J. Michaely and K.A. Herrmann both contributed equally to this work.