~(31)P MR波谱在犬顿抑心肌实验中的应用

目的　评价 3 1PMRS在犬顿抑心肌研究中的应用价值。方法　 10条健康杂种犬开胸阻断左冠状动脉前降支 2 0min后 ,解除阻断予以再灌注 ,分别在术前、术后 2、4、6、8h ,1、2、3、12d不同时间点进行心肌3 1PMRS的动态检测。结果　正常对照组结果显示 ,心肌组织磷酸肌酸 /β -三磷酸腺苷 (PCr/β -ATP)和无机磷酸盐 /磷酸肌酸 (Pi/PCr)的比值分别是 1.70± 0 .6 1与 0 .2 0± 0 .0 8,pH值为 7.19± 0 .2 0。顿抑心肌再灌注后 2h ,PCr/β -ATP和 pH值下降 (Ρ <0 .0 5 ) ,Pi/PCr比值提高 (Ρ <0 .0 1) ;PCr/β -ATP在再灌注后 4h时接近正常 ,之后无明显差异 ;而Pi/PCr比值上升持续到再灌注后第 3d ,在第 12d恢复至正常水平。pH值在再灌注后 6～ 8h逐渐恢复正常。结论　心肌缺血再灌注后 ,Pi/PCr比值的变化能较早且准确地反映心肌的代谢状态 ,为临床早期诊断顿抑心肌提供了一种无创性连续观测的新方法。     

磁共振心肌灌注成像及心肌活力分析诊断急性心肌梗死的价值

目的:研究磁共振心肌灌注成像及心肌活力分析在诊断急性心肌梗死中的价值。方法:选择37例急性心肌梗死患者作为观察组,同时选出37例无心血管疾病的正常志愿者作为对照组,均行灌注成像和心肌活力分析,观察2组相应心肌信号强度平均值、首过最大上升斜率及首过时间。结果:磁共振心肌灌注成像延迟期观察组梗死心肌的信号强度平均值为73.23±35.24,对照组正常心肌(对应观察组梗死区)为17.99±8.15,2组对比差异具有统计学意义(P<0.01);观察组梗死心肌的首过最大上升斜率平均值为32.85±20.69,对照组正常心肌(对应观察组梗死区)为44.68±23.60,2组对比差异具有统计学意义(P<0.01)。观察组患者心肌梗死区首过时间平均为(5.04±1.74)s,对照组正常心肌(对应观察组梗死区)为(2.82±1.82)s,2组对比差异具有统计学意义(P<0.01)。结论:磁共振心肌灌注成像及心肌活力分析可用于诊断急性心肌梗死。     

斑点追踪显像评价犬心肌缺血-再灌注后存活心肌的价值

目的探讨犬缺血-再灌注模型中斑点追踪超声心动图检查存活心肌的价值。材料与方法健康犬14只,开胸后阻断左冠状动脉前降支构建心肌缺血-再灌注模型(缺血3h,再灌注1h),于再灌注1h采集左心室中部切面短轴二维图像,处死犬后行氯化三苯基四氮唑(TTC)染色。随机测量84个节段收缩末期的径向应变和圆周应变,根据TTC染色结果,比较梗死面积≤50%及>50%节段的径向应变和圆周应变。结果与≤50%梗死面积或无梗死节段相比,梗死面积>50%的节段,其收缩末期径向应变和圆周应变减低(P<0.05)。收缩末期径向应变≥9.72%,判定心肌存活的敏感度为77%,特异度为84%;圆周应变≤-4.92%,判定心肌存活的敏感度为90%,特异度为94%,两者判断心肌存活的优劣性差异无统计学意义(P>0.05),但圆周应变有更大的曲线下面积。结论二维应变超声心动图能够检测心肌功能障碍,评价心肌存活性;收缩末期径向应变与圆周应变均为可靠指标。     

大鼠脑缺血再灌注的磁共振扩散加权成像研究

目的：采用磁共振扩散加权成像（DWI）评价大鼠脑缺血早期再灌注的动态变化,观察缺血早期再灌注对脑梗死的保护作用。方法：选取16只SD雄性大鼠,采用线栓法制作右侧大脑中动脉闭塞（MCAO）脑缺血模型,随机分为缺血再灌注组（缺血2h后再灌注）及对照组（永久性缺血）,每组8只。分别于制作MCAO模型后30min、2h、6h、12h及24h行MRI扫描。计算并比较缺血再灌注组与对照组大鼠每次扫描的脑梗死体积、脑梗死体积的增长率、脑梗死最大层面梗死区域的ADC值和rADC值。磁共振检查结束后处死大鼠,断头取脑行HE染色,并与DWI结果进行比较。结果：缺血再灌注组和对照组大鼠MCAO后DWI均显示右侧大脑中动脉供血区异常高信号,ADC图上为低信号。MCAO后2h、6h、12h及24h的DWI图上缺血再灌注组体积增长率均低于对照组,仅12h及24h时差异有统计学意义（P〈0.05）。MCAO后30min缺血再灌注组与对照组梗死区ADC值及rADC值差异均无统计学意义（P〉0.05）,但2h、6h、12h及24h时缺血再灌注组梗死区ADC值及rADC值均明显小于对照组（P〈0.05）。缺血再灌注组与对照组大鼠MCAO后HE染色均显示脑梗死灶体积与相应DWI层面差异无统计学意义（P〉0.05）。结论：DWI是评价超早期脑梗死再灌注的敏感方法,为脑梗死的疗效评价提供客观依据。     

冠状动脉侧枝循环对STEMI患者心肌损伤影响的心血管MRI研究

目的探讨应用心血管磁共振(cardiovascular MR, CMR)多序列参数联合评价法,对急性ST段抬高型心肌梗死(ST-segment elevation myocardial infarction, STEMI)患者缺血再灌注后冠状动脉侧枝循环对心肌损伤的影响进行评估,为预后诊治提供影像支撑。方法对临床确诊的37例STEMI患者以Rentrop分级标准分为侧枝循环不良组(Rentrop:0～1级)和侧枝循环良好组(Rentrop:2～3级),比较两组患者水肿心肌、梗死心肌、梗死水肿心肌比、梗死水肿心肌差以及可挽救心肌等磁共振定量参数。结果冠状动脉侧枝循环不良组患者23例,良好组14例;不良组水肿心肌略大(31.0±8.4%LV vs. 28.7±7.9%LV,P=0.42);不良组梗死心肌显著高于良好组(6.7±3.2%LV vs. 3.9±1.7%LV,P<0.05);梗死水肿心肌比(21.7±9.8%vs. 13.8±5.8%)和可挽救心肌(78.3±9.8%vs. 86.2±5.8%),不良组均显著低于良好组(P<0.05)。结论 CMR可定量评估STEMI...     

急性缺血再灌注心肌磁共振成像实验研究

目的：通过MR灌注成保评价急性梗死心肌组织血流灌注特点。方法：采用结扎左前降支90min存灌注的方法建立为存灌注梗死心肌组，对6只犬行MRI灌注成保及延迟扫描，观察犬心肌缺血存灌注模型梗死心肌MRI特点。结果：犬心肌缺血存灌注梗死心肌MR灌注成保表现为灌注缺损区，延迟扫描表现为高信号。结论：MR灌注成保有助于评价心肌血流，诊断心肌缺血存灌注梗死心肌。     

13N-NH3心肌灌注显像评价兔心肌梗死模型缺血再灌注

目的　探讨兔心肌梗死模型缺血再灌注与梗死面积之间的关系。方法　完全闭塞 16只雄性新西兰大白兔冠状动脉左前降支 4 5min ,随机分为再灌注组 (n =8)和无再灌注组 (n =8) ,7～10d后行1 3N NH3PET CT心肌灌注显像 ,与三氯四氮唑 (TTC)染色梗死灶缺损百分比进行比较。HE染色评价梗死灶病理学改变。结果　TTC染色示无再灌注组、再灌注组实际梗死灶缺损百分比分别为 (2 5 7± 2 3) %、(2 1 5± 2 4 ) % (P =0 0 0 31)。1 3N NH3PET CT心肌灌注显像示 ,无再灌注组与再灌注组缺损百分比分别为 (2 4 6± 2 2 ) %和 (2 0 5± 2 5 ) % (P =0 0 0 37)。组内TTC染色与PET CT显像结果差异无显著性 (P >0 0 5 )。结论　1 3N NH3PET CT心肌灌注显像较TTC染色能更准确测定心肌梗死灶范围。     

糖尿病对大鼠心肌缺血预处理保护作用的影响

目的 探讨糖尿病对缺血预适应(IPC)在大鼠缺血再灌注心肌保护作用中的影响.方法 取糖尿病SD大鼠及非糖尿病SD大鼠各30只,分为非糖尿病对照组(A组)、非糖尿病缺血再灌注组(B组)、非糖尿病IPC组(C组)、糖尿病对照组(D组)、糖尿病缺血再灌注组(E组)、糖尿病IPC组(F组),每组10只.动物处死后建立离体心脏Langendorff灌注模型.对照组采用全心灌流90min,余不做任何处理;缺血再灌注组采用心脏平衡灌流30min后,缺血30min,再复灌30min;IPC组采用心脏平衡灌流10min,经2次缺血5min再灌注5rnin后,缺血30min,再复灌30min.比较各组复灌30min后心排血量(CO)、左室发展压(LVDP)、左室内压最大上升和下降速率(±dp/dtmax)的恢复率,检测缺血前及复灌30rain后冠脉流出液中肌酸激酶(CK)的活性和心肌组织中丙二醛(MDA)、超氧化物歧化酶(SOD)的含量,并计算心肌含水率.结果 与非糖尿病缺血再灌注组比较,非糖尿病IPC组CK活性、MDA含量、心肌含水率均明显降低,SOD含量明显增加,CO、LVDP、 dp/dtmax、-dp/dtmax恢复率明显增加(P<0.05).而糖尿病IFC组与糖尿病缺血再灌注组比较上述变化均不明显(P>0.05).结论 糖尿病可抑制IPC对大鼠缺血再灌注心肌的保护作用.     

SENSE技术在急性心梗磁共振成像中的应用价值

目的　通过快速MR心脏电影及灌注成像评价急性心肌梗死组织的心肌运动及血流灌注特点 ,研究敏感编码技术在快速心脏磁共振成像中的应用价值。方法　结扎犬冠状动脉左前降支建立急性心梗模型。结合SENSE技术 6只犬分别行快速多层面多相位屏气电影扫描、快速MR心肌灌注及延迟扫描观察梗死心肌MRI特点。结果　心脏电影成像可显示犬前壁心梗区室壁运动异常 ,MR灌注成像表现为局部灌注缺损区 ,延迟扫描表现为梗死区高信号。使用SENSE技术扫描速度提高 1倍 ,且图像质量无明显变化。结论　快速MR电影及灌注成像有助于评价心肌运动及血流灌注 ,诊断急性梗死心肌。SENSE技术可提高心脏成像的时间分辨率 ,且在扫描时间不变时提高空间分辨率 ,减少运动及敏感伪影性 ,是一种行之有效的提高MRI速度的技术方法 ,在心脏成像中具有非常重要的应用价值。     

大鼠心肌缺血再灌注损伤及中性粒细胞浸润与一氧化氮心肌保护作用的研究

目的 中性粒细胞(Neu)心肌浸润是心肌缺血-再灌注(I/R)损伤的重要机制之一。本实验通过在SD大鼠中建立心肌I/R模型,研究I/R过程中心肌损伤与中性粒细胞浸润的关系,并通过左型精氨酸(L-Arg)干预,探讨一氧化氮(NO)对中性粒细胞浸润的影响及其在心肌I/R损伤中的保护作用。方法 实验分对照(CON)组、L-Arg处理组。每组又分缺血前、缺血40 min、再灌 1h、再灌 3h和再灌6 h 5个时间点,分别测定各组各时间点血清肌酸磷酸激酶(CPK)及心肌匀浆丙二醛(MDA)值,并观察心肌组织病理学的改变。结果 (1)CPK及心肌匀浆MDA测定结果:再灌注后各时相血清CPK及肌匀浆MDA含量较缺血前明显上升,再灌注3h后达到高峰。L-Arg组中再灌注后各时相点血清CPK及肌匀浆MDA明显低于CON组(P<0.05)。(2)H-E染色结果:缺血前心肌细胞完整,边界清楚,心肌横纹清晰。CON组:再灌后1h出现Neu心肌浸润,再灌3 h Neu心肌浸润更明显,累及心肌全层,伴有局灶心肌坏死;再灌6 h后Neu浸润尤甚,大片心肌坏死,并可见小血管内Neu聚集现象。L-Arg组:再灌注后Neu心肌浸润明显减少,再灌6 h心肌坏死灶较CON组明显缩小。结论 (1)心肌I/R过程中有大量Neu心肌浸润,与心肌损伤密切。(2)L-Arg能抑制Neu心肌浸润,具有心肌保护作用。     

Safety protocols for interventional MRI

RATIONALE AND OBJECTIVES: To review magnetic resonance safety protocols and supplement them for interventional applications. MATERIALS AND METHODS: The American College of Radiology White Papers on MR Safety are summarized. Elements relevant to interventional MR procedures are emphasized. Additional policies and procedures specifically for interventional MR applications covering safety, training, and MR compatibility are proposed. RESULTS: A comprehensive operational policy for an interventional MR department is proposed. The policies and procedures helped our department perform over 400 surgeries and maintain a perfect safety record for 5 years. CONCLUSION: Interventional MR departments can operate safely but require policies and procedures beyond those required for diagnostic MR departments.     

Accessory equipment considerations with respect to MRI compatibility

The MR Section of The National Electrical Manufacturers Association (NEMA), in response to a request from the Food & Drug Administration (FDA), recently issued a position paper to address generic issues related to the compatibility of accessory equipment produced by third party equipment manufacturers or MR equipment users and intended to be used in conjunction with MR equipment or within the MR scanning room. The recommendations concern scanning accessories, such as radiofrequency (RF) coils, patient monitoring equipment and injectors, as well as patient comfort accessories and positioning devices. The following issues related to safety performance are discussed: (a) the interaction of the equipment with the MR scanner, (b) interactions of the MR scanner with the equipment, and (c) potential safety hazards for patients and staff that can be posed by accessory equipment in the MR scan environment. The recommendations are based on combined input from NEMA member companies who manufacture MR systems and MR accessories and are presented for consideration in the design of MR accessory products and incorporation of these concepts into testing plans to ensure MR compatibility of third party devices.     

ACR guidance document on MR safe practices: 2013

Because there are many potential risks in the MR environment and reports of adverse incidents involving patients, equipment and personnel, the need for a guidance document on MR safe practices emerged. Initially published in 2002, the ACR MR Safe Practices Guidelines established de facto industry standards for safe and responsible practices in clinical and research MR environments. As the MR industry changes the document is reviewed, modified and updated. The most recent version will reflect these changes. J. Magn. Reson. Imaging 2013;37:501–530. © 2013 Wiley Periodicals, Inc.     

Imaging time reduction through multiple receiver coil data acquisition and image reconstruction

A technique is described for the simultaneous acquisition of MRI data using two independent receiver coils surrounding the same region of tissue, which enables the collection of data necessary for image reconstruction in a reduced number of phase-encoded acquisitions. This results in a 50% reduction in minimum scan time and may be useful in time-critical procedures. The algorithm and imaging procedures are described, and example images are shown that illustrate the reconstruction. Signal to noise is decreased by the square root of the time savings, making this technique applicable to cases in which the need to decrease minimum scan time outweighs the signal to noise penalty.     

Preoperative local MRI-staging of patients with a suspected pancreatic mass

The aim of this study was to define the value of MRI of the pancreas for preoperative local staging of patients with a suspected pancreatic mass. Ninety-four patients (41 women, 53 men; age range 32-87 years) with a suspected pancreatic tumor underwent preoperative staging with MRI on a 1.5-T system. The MRI protocol included breath-hold MR cholangiopancreatography in turbo spin-echo technique, biphasic contrast-enhanced 3D MR angiography, and MRI of the upper abdomen with breath-hold T2-weighted half-Fourier acquired single-shot turbo spin-echo and T1-weighted fast-low-angle-shot (pre- and postcontrast) sequences. Data were collected prospectively and analyzed by two radiologists in agreement modality. Evaluation criteria were vascular involvement, resectability, and a characterization benign vs malignant. Results were compared to histopathology in 78 patients. Sixteen patients were followed-up. In 74 of 94 patients a solid tumor or an inflammation of the pancreas ( n=62) or the papilla ( n=12) was detected. In this group, MRI had a sensitivity of 98%, a specificity of 92%, and an accuracy of 96% in the characterization of malignant tumors. Regarding only the solid tumors, the positive predictive value of MRI was 87% with respect to resectability. Other pathologic findings included adenoma or inflammation of the duodenum ( n=5), carcinoma or benign stenosis of the choledochus duct ( n=7) and carcinoma of the gall bladder ( n=2). In 6 patients MRI did not depict any pathologic findings, and follow-up confirmed this interpretation. Magnetic resonance imaging allows a local preoperative staging in patients with suspected pancreatic tumor. Limitations, however, concern to the diagnostics of peritoneal and/or liver metastases.     

Enhancement patterns of prostate cancer in dynamic MRI

Our objective was to analyze fast-field-echo dynamic subtracted (FFE/DS) MRI data in prostate cancer, in order to recognize enhancement patterns of tumoral tissue in comparison with non-tumoral peripheral prostatic tissue. Eleven consecutive patients with prostate cancer were proposed for radical prostatectomy. Before surgery, all patients underwent endorectal coil MRI examination. In addition to standard sequences, a dynamic study was performed by FFE/DS to evaluate tumoral behavior after Gd-DTPA rapid infusion. Analysis of the imaging was made by the means of the time/signal intensity curve obtained during early contrast medium enhancement, sampling both the abnormal enhancing focal area and the opposite lobe at the level of the main prostatic tissue. A focal area of increased enhancement was observed in the site of the tumor in all cases. The time/intensity curve sampled on this area and compared with the opposite lobe demonstrated a high confidence interval of the difference of the data: mean tumor maximal intensity 1331 (SD 187) vs normal 470 (SD 139) and mean tumor rise time 103 s (SD 30) vs normal 250 (SD 38; p<0.01). In tumoral tissue, the enhancement percentage of signal intensity (SI%=pre-contrast minus post-contrast/pre-contrast ×100) was 316.7%. At FFE/DS, there is a typical behavior of the time/intensity curve of contrast enhancement in prostatic cancer that might be employed in diagnosis of the disease. Electronic Publication     

Determination of gradient magnetic field-induced acoustic noise associated with the use of echo planar and three-dimensional,fast spin echo techniques

The purpose of this study was to assess gradient magnetic-field-induced acoustic noise levels associated with the use of echo planar imaging (EPI) and three-dimensional fast spin echo (3D-FSE) pulse sequences. Acoustic noise measurements were obtained from two different high field-strength MR systems (1.5 T, Siemens and General Electric Co.) under ambient noise conditions and the use of EPI and 3D-FSE pulse sequences. Parameters were selected to produce “worst case” acoustic noise levels. Acoustic noise recordings were made at the entrance, the center, and at the exit of the magnet bores with a specially designed microphone that was unperturbed by electromagnetic fields. The highest ambient noise levels (A-weighted scale) were 67 dB (Siemens: the same values were recorded at the center and at the exit) and 78 dB (General Electric Co.; recorded at the exit). The highest acoustic noise levels recorded during activation of the gradient magnetic fields were 114 dB (Siemens) and 115 dB (General Electric Co.) and those occurred at the centers of the MR systems with the use of the EPI technique. Gradient magnetic fields associated with the use of EPI and 3D-FSE techniques produced acoustic noise levels that were within permissible levels recommended by federal guidelines.     

Virtual MR arthroscopy of the wrist joint: a new intraarticular perspective

Objective The aim of this study is to investigate whether virtual MR arthroscopy could be used to visualize the internal architecture of the radiocarpal compartment of the wrist joint in comparison to surgical arthroscopy.Design Diluted paramagnetic contrast material was injected into the radiocarpal compartment prior to MR examination in all patients. A fat-suppressed T1-weighted three-dimensional fast spoiled gradient echo sequence was acquired in addition to our standard MR imaging protocol in each patient. Three-dimensional data sets were then transferred to an independent workstation and were postprocessed using navigator software to generate surface rendered virtual MR arthroscopic images.Patients Nineteen patients referred for chronic ulnar-sided wrist pain were evaluated with conventional MR arthrography prospectively.Results and Conclusion Virtual MR arthroscopic images demonstrating the triangular fibrocartilage complex (TFCC) in an intraarticular perspective were achieved in 12 out of 19 patients. Our preliminary investigation suggests that although it has several limitations, virtual MR arthroscopy shows promise in visualizing the TFCC from an intraarticular perspective.     

Whole-body MR angiography using a novel 32-receiving-channel MR system with surface coil technology: first clinical experience

PURPOSE: To demonstrate the feasibility of detecting atherosclerotic vascular disease using an innovative magnetic resonance angiography (MRA) protocol in combination with a dedicated whole-body MR scanner with new surface coil technology. MATERIALS AND METHODS: A total of 10 volunteers and eight patients with peripheral arterial occlusive disease (PAOD) were examined at 1.5 T. Conventional digital subtraction angiography (DSA) of the symptomatic region was available as a reference standard in all eight patients. Depending on subjects' size, four to five three-dimensional data sets were acquired using an adapted injection protocol. Images were assessed independently by two readers for vascular pathology. Additionally, signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were measured. RESULTS: Whole-body MRA yielded excellent sensitivity and specificity of more than 95% for both readers with high interobserver agreement (k = 0.93). Surface coil signal reception rendered a high SNR (mean 151.28 +/- 54.04) and CNR (mean 120.75 +/- 46.47). Despite lower SNR and CNR of the cranial and cervical vessels, a two-step injection protocol exhibited less venous superposition and therefore proved to be superior compared to single-bolus injection. CONCLUSION: Our approach provides accurate noninvasive high-resolution imaging of systemic atherosclerotic disease, covering the arterial vasculature from intracranial arteries to distal runoff vessels. The recently introduced MR scanner and coil technology is feasible to significantly increase the performance of whole-body MRA.