单层TSE序列及多层HASTE序列磁共振胰胆管成像技术在临床应用价值的比较

目的:比较磁共振胰胆管成像技术的2种成像方法,探讨有助于临床诊断胆系病变的磁共振检查的最佳方法。方法:分析经手术病理或活检证实的35例胰胆管病变患者2种不同方法(单层TSE序列及多层HASTE序列)MRCP影像表现,比较二者显示胰胆管病变的优缺点。结果:单层TSE序列采集时间短,空间分辨率高,受运动伪影影响小;多层HASTE序列采集时间较长,运动伪影明显。结论:单层TSE-MRCP成像结合常规SE及梯度序列冠轴位相扫描是胰胆管病变的磁共振检查的最佳方法之一。     

胎儿磁共振成像序列的对比研究及应用

目的:比较单次激发快速自旋回波序列(SSFSE)和快速成像稳态采集序列(FIESTA)对胎儿解剖结构和病变的显示能力,探讨两种快速成像序列在胎儿MRI中的临床应用价值。方法:82例中晚期妊娠孕妇行单次激发快速自旋回波序列和快速成像稳态采集序列扫描,并根据图像平均信号强度、图像质量和图像伪影等方面对两个序列在胎儿解剖结构和病变的显示能力方面做出统计学分析。结果:两种序列对胎儿解剖结构和异常病变的显示各有优点和不足,SSFSE和FIESTA均能清楚显示胎儿正常脏器的解剖结构和异常病变。SSFSE的平均信号强度和分辨力要高于FIESTA序列,但其呼吸伪影要比FIESTA序列明显,而对于液体的显示FIESTA要优于SSFSE。结论:SSFSE序列和FIESTA序列对胎儿的不同组织其显示能力不同,所以根据病情做出不同的选择是非常重要的。     

TSE和HASTE序列在上腹部T_2WI中的应用对比

目的:评价磁共振TSE序列和HASTE序列在上腹部T2WI的应用价值,了解其各自的特点及临床应用价值。方法:使用Siemens Magnetom Avanto 1.5T磁共振成像仪对36例行上腹部MRI检查的患者分别行T2W-TSE-trig-ger、T2W-TSE-bh、T2W-HASTE-trigger和T2W-HASTE-bh扫描。由两位有丰富经验的高年资医生单独评价4组图像运动伪影,肝内外脉管显示的清晰度及图像的整体质量,并对结果进行统计学分析和处理。结果:4种成像序列的相对信噪比差异无统计学意义(F=1.388,P=0.259),但4种图像的呼吸运动伪影、肝内外血管显示及整体图像质量之间差异均有显著性意义。T2W-TSE-trigger序列肝内外血管显示优于其余3种方法(P=0.000～0.001);T2W-TSE-trigger的整体图像质量好于其余3种方法(P=0.001～0.022);T2W-HASTE-trigger组中图像的运动伪影最少,要好于其他3种方法(P=0.005～0.025)。结论:HASTE序列可以更好地抑制运动伪影,但T2W-TSE-trigger序列可得到较高的图像质量,同时对肝脏的解剖结构和细节的显示有一定的帮助。     

MRI在儿童轻型急性胰腺炎中的应用

目的:评价MRI在儿童轻型急性胰腺炎诊断中的作用并探讨适合的MRI检查序列。方法:对20例胰腺正常儿童及10例经临床确诊的轻型急性胰腺炎患儿行MRI检查。扫描序列为脂肪抑制快速小角度激发T1加权成像(FLASH)、刀锋技术快速自旋回波T2加权成像(BLADE-TSE)、常规快速自旋回波T2加权成像(TSE)、真稳态进动快速成像(True-FISP)以及DWI成像(b=400、600、800s/mm2)。评价各成像序列在胰腺炎诊断中的优势,确定DWI成像时的合适b值。结果:本组10例胰腺炎患儿在MRI上均有阳性表现,在FLASH序列上胰腺相对于肝脏呈等信号(2例)及低信号(8例),在BLADE-TSE序列上,胰腺相对于肝脏呈较高信号。在FLASH及BLADE-TSE序列上,胰腺炎组与正常对照组之间胰腺与肝脏信号强度比值差异具有统计学意义。FLASH序列显示胰腺炎胰腺内在信号改变明显;True-FISP序列在显示胰周炎症敏感清晰;BLADE-TSE序列与常规TSE序列对胰腺及胰周炎症均可较好显示,但成像质量BLADE-TSE序列优于常规TSE序列。DWI成像时选择b值600s/mm2时图像既有较好对比度又有较高信噪比。结论:MRI在儿童轻型急性胰腺炎诊断中具有较高价值,FLASH、BLADE-TSE以及True-FISP序列可作为评价胰腺炎的常规扫描序列,DWI扫描时使用b值为600s/mm2较为合适。     

3.0TMRI螺旋桨技术在女性盆腔中的应用

目的探讨螺旋桨技术(PROPELLER)在3.0T MRI上减轻女性盆腔成像伪影和提高其整体成像质量中的价值。资料与方法 38例女性盆腔患者行矢状面PROPELLER T2WI和常规快速自旋回波(FSE)T2WI扫描,采用相同的成像矩阵、视野、层数、层厚和层间距,评价与呼吸运动和肠管蠕动相关的运动伪影程度、结合带等盆腔结构的显示以及图像整体的成像质量。结果 PROPELLER T2WI在运动伪影程度和女性盆腔结构显示方面的平均得分均高于常规FSE T2WI,且在抑制运动伪影方面差异有统计学意义(P<0.001),其中1名医师在评价盆腔结构显示方面差异无统计学意义(P>0.05)。最后2名医师对两组序列的整体图像质量评分结果差异有统计学意义(P<0.05、P<0.001)。结论 PROPELLER T2WI在显示结合带等解剖结构、矫正肠管蠕动和呼吸运动伪影及提高图像的整体质量方面均优于常规FSE T2WI,在3.0T MRI上进行女性盆腔检查时,可以考虑用PROPELLER T2WI代替常规FSE T2WI。     

BLADE技术在消除MRI膝关节运动伪影方面的应用

目的 探讨刀锋伪影校正(BLADE)技术在消除MRI膝关节运动伪影的应用价值.方法 32例膝关节常规MRI检查中出现运动伪影的患者,改用BLADE技术扫描(PD矢状位、T2矢状位),以是否能够清晰显示膝关节结构、半月板及交叉韧带为标准,与常规序列对比评估BLADE技术对消除膝关节运动伪影的应用价值.结果 膝关节常规序列扫描中出现运动伪影,改用BLADE技术扫描后,图像运动伪影消除,图像质量明显改善.结论 BLADE技术对膝关节常规扫描中产生的运动伪影有明显的校正作用,可广泛用于产生运动伪影的膝关节MRI检查中.     

HASTE序列磁共振胰胆管成像:单层和多层法成像技术比较研究

目的　采用HASTE磁共振成像技术进行磁共振胰胆管成像并比较 2种不同成像方法优劣。方法　对 66例临床怀疑胰胆管病变患者进行磁共振检查 ,所有病例全部行胰胆系常规SE及梯度序列矢冠轴位相扫描和HASTE序列 2种不同方法 (多层薄块采集MIP重建法和连续单层厚块采集法 )MRCP成像。对 2种不同HASTE序列显示胰胆管病变的优缺点进行比较。结果　 66例中共有 44例确诊为胰胆系病变 ,阳性率 67% ( 4 4/ 66)。采用单层法 66例 ( 10 0 % )全部达到诊断标准 ;多层法有 5 8例 ( 88% )达到诊断标准。单层法采集空间分辨率较高 ,且采集时间短 ,但受血管伪影影响较明显。多层法采集密度分辨率高 ,但运动伪影明显。结论　单层采集HASTE屏气MRCP成像结合常规SE及梯度序列矢冠轴位相扫描是胰胆管病变磁共振检查的最佳方法之一     

MRI快速扫描技术在儿童先天性心脏病诊断中的应用

目的:探讨MRI半傅立叶采集单次激发快速SE(HASTE)序列、真稳态进动快速成像(TrueFISP)序列和并行采集技术在儿童先天性心脏病诊断中的应用价值.方法:对50例经超声心动图检查的先天性心脏病患儿进行心脏大血管MRI检查,其中26例行DSA检查,全部病例经手术证实.扫描序列包括HASTE、TrueFISP序列以及回顾性心电门控心血管电影成像,并加用并行采集技术.分析各序列MRI图像质量,并将MRI检查结果与超声心动图、DSA结果进行对照.结果:MRI共检出10种复杂先心共181处心血管畸形.26例行DSA检查共检出畸形120个并均与手术结果吻合,MRI显示畸形114个(95.00%),超声心动图检出畸形110个(92.67%).TrueFISP序列和HASTE序列利于显示血管畸形,电影序列有助于检出心内外分流.结论:HASTE黑血技术、TrueFISP亮血技术结合快速电影序列进行心脏MRI检查,可以获得高质量的图像以及较高的病变检出率,适用于儿童先天性心脏病的诊断.     

HASTE序列单层法磁共振胰胆管成像与常规磁共振胰胆管成像的比较

目的比较HASTE序列单层法磁共振胰胆管成像(HASTE-MRCP)和常规磁共振胰胆管成像(OMRCP),评价HASTE-MRCP的临床应用价值。方法48例梗阻性黄疸和30例无黄疸患者行OMRCP、HASTE-MRCP单层扫描,比较2种技术诊断的准确性。结果2个序列均能显示胆管病变部位、疾病特征、近侧扩张胆管以及远侧正常胰胆管;显示扩张胆管直径2个序列间没有显著性差异;HASTE-MRCP单层法采集空间分辨率较高,且采集时间短,但受血管伪影影响较明显。OMRCP采集密度分辨率高,但运动伪影明显。结论单层采集HASTE-MRCP成像结合常规SE及梯度序列冠轴位相扫描是胰胆管病变磁共振检查的最佳方法之一。     

IMAR对起搏器植入患者胸部CT扫描的应用价值

目的:通过仿真胸部体模对伪影区域内肺结节及肺组织显示效果的分析,评价IMAR算法对心脏起搏器植入患者CT扫描的应用价值。方法:在胸部仿真体模内置入模拟肺结节60个,分别在心脏起搏器放置前后进行胸部CT扫描(常规剂量及低剂量扫描),图像分别采用无IMAR和有IMAR两种方式进行重建。比较肺结节的检出率,测量模拟肺结节CT值与其标称CT值的差值,并比较图像的噪声值、SNR、CNR值,并对主观图像质量评分。结果:低剂量胸部CT扫描时,使用IMRA检出结节数目较多;使用IMAR算法磨玻璃肺结节的测量CT值与标称CT值的差值较小。使用IMAR重建时图像SNR及CNR值均较高。IMAR重建图像质量主观评分高于未使用IMAR。结论:IMAR算法能减轻心脏起搏器金属伪影,提高低剂量胸部CT对伪影区域结节的检出率,提高伪影区域磨玻璃肺结节的显示效果,提高伪影区域图像质量。     

Fast T1- and T2-weighted pulmonary MR-imaging in patients with bronchial carcinoma

PURPOSE: A prospective study to evaluate the diagnostic potential and limitations of three fast MRI sequences in patients with bronchial carcinoma based on the comparison with spiral CT. MATERIAL AND METHODS: Three fast chest MRI sequences from 20 patients with central or peripheral bronchial carcinoma were evaluated by two observers for relation of tumour to adjacent structures, lymph node enlargement, additional pulmonary lesions and artefacts. The information from MR-imaging was compared with the results from spiral CT. MRI comprised a T1-3D-GRE breath-hold examination ("VIBE", TR/TE 4.5/1.9 ms, flip-angle 12 degrees , matrix 502 x 512, 2.5 mm coronal slices), a breath-hold, T2-HASTE sequence (TR/TE 2000/43 ms, matrix 192 x 256, 10 mm coronal slices) and a respiration-triggered T2-TSE sequence (TR/TE 3000-6000/120 ms, matrix 270 x 512, 6 mm transverse slices). The FOV was adapted individually (380-480 mm). RESULTS: The presence of the primary bronchial carcinoma and infiltration of thoracic structures by tumour tissue could be demonstrated by all sequences. VIBE sequence was more suitable for detecting small pulmonary nodules than the other MRI examinations, but compared to CT still 20% of these lesions were missed. Contrary to VIBE and T2-weighted TSE scans, HASTE sequence was limited in imaging mediastinal lymph nodes due to missing relevant findings in 2/20 patients. HASTE images significantly provided the lowest rate of artefacts in imaging lung parenchyma (P < 0.001 in peripheral parenchyma), but spatial resolution was limited in this sequence. Concerning the differentiation between tumour and adjacent atelectasis (n = 8), T2-weighted TSE imaging was superior to CT and VIBE in all cases and to HASTE sequence in 4/8 patients. CONCLUSION: The combination of VIBE and HASTE sequence allows for an adaequate imaging of thoracic processes in patients with bronchial carcinoma, limited only in visualizing small pulmonary nodules. To obtain more detail resolution and to differentiate tumour tissue from adjacent atelectasis, T2-TSE examination may be added in selected cases.     

Detection and characterization of intracardiac thrombi on MR imaging

OBJECTIVE: The aim of our study was to compare the diagnostic accuracy achieved using different MR techniques with the diagnostic accuracy achieved using transthoracic and transesophageal echocardiography to detect intracardiac thrombi. MATERIALS AND METHODS: Twenty-four patients with known or suspected intracardiac thrombi were examined using MR imaging and echocardiography. All MR examinations were performed on a 1.5-T MR scanner using dark-blood-prepared half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences, fast imaging steady-state free precession (trueFISP) cine sequences, and inversion recovery gradient-echo fast low-angle-shot (inversion recovery turbo FLASH) sequences after injection of 0.2 mmol/kg of gadolinium diethylene triamine pentaacetic acid. RESULTS: MR imaging and echocardiography revealed 12 thrombi-two in the right atrium, one in the right ventricle, three in the left atrium, and six in the left ventricle. Compared with echocardiography, MR imaging revealed three additional thrombi in the left ventricle; these thrombi were confirmed at surgery. All 15 thrombi appeared as filling defects on early contrast-enhanced inversion recovery turbo FLASH MR images. Only seven thrombi were detected on HASTE images, and 10 thrombi were seen on trueFISP images. Four thrombi showed enhancement 10-20 min after contrast material injection and were characterized as organized clots. CONCLUSION: Contrast-enhanced inversion recovery turbo FLASH sequences were superior to dark-blood-prepared HASTE and trueFISP cine MR images in revealing intracardiac thrombi. Compared with transthoracic echocardiography, MR imaging was more sensitive for the detection of left ventricular thrombi. The characterization of thrombi may be used to predict the risk of embolism, which is higher for subacute clots than for organized thrombi.     

Quantitative analysis of lung and tumour mobility: comparison of two time-resolved MRI sequences

The purpose of this study was to describe the use of parallel imaging technique (PAT) using dynamic MRI in lung and tumour mobility during the breathing cycle. 20 patients with stage I non-small cell lung carcinoma were investigated using two dynamic gradient echo sequences with PAT (TrueFISP (fast imaging with steady precession), and fast low angle shot (FLASH). Craniocaudal distance from the apex to the diaphragm of the thorax and tumour mobility during the breathing cycle were measured. Signal-to-noise ratio (SNR) of the tumour was determined. In spite of the different temporal resolutions both trueFISP and FLASH sequence proved to be adequate to continuously measure lung motion and tumour mobility. SNR of the tumour was significantly higher using the trueFISP sequence than FLASH sequence (20.7+/-3.6 vs 5.8+/-2.3, p<0.01). Mobility of the tumour bearing hemithorax was significantly lower compared with the non-tumour bearing hemithorax (p<0.05). Dynamic MRI using PAT allows for continuous quantitative documentation of tumour mobility and lung motion. Because of the higher SNR, trueFISP sequence provides a better delineation of intrapulmonary lesions with a sufficient temporal resolution.     

MRI in staging of lung cancer

PURPOSE: Overview of magnetic resonance imaging (MRI) in staging of lung cancer. MATERIAL AND METHODS: Currently available methods of imaging lung cancer, lymph node and distant metastases by MRI are explained. At present, MRI is mainly used in the detection of cerebral metastases and assessment of infiltration of the thoracic wall and of the mediastinum. The capabilities of T2-weighted single-shot TSE (HASTE) and T1-weighted 3D gradient echo techniques (VIBE) are demonstrated. RESULTS: With the advent of new fast sequences like HASTE and VIBE the spatial resolution comes close to that of computed tomography but with an outstanding soft tissue contrast and without radiation exposure. The introduction of lymph node specific contrast media will improve sensitivity and specificity in N staging. Additionally, whole-body MRI is capable of detecting distant metastases, in particular in the organs at risk, i.e. brain, upper abdomen and musculoskeletal system. CONCLUSION: MRI is gaining importance as part of a multimodal imaging approach for staging of lung cancer.     

High-resolution MRI of pancreatic masses with a new circularly polarized body phased-array coil

A total of 18 patients with clinical suspicion of a pancreatic tumor underwent dynamic contrast-enhanced CT and MRI examinations. A fat-suppressed T1-weighted 2D fast-low-angle-shot (FLASH) sequence and a T2-weighted spin-echo (SE) sequence were applied in a transverse orientation using a circularly polarized (CP) body phased-array coil. The FLASH sequence was repeated after Gd-DTPA administration. The highest spatial resolution was 1.37×1.37×3.00 mm³. In two cases a half Fourier single-shot turbo-SE sequence (HASTE) was additionally applied. In a comparison between CT and MRI, pancreatic masses could be demonstrated and characterized with excellent image quality. The fat-saturated 2D FLASH sequence yielded the highest contrast-to-noise ratios after Gd-DTPA administration between pancreas and inflammatory or neoplastic lesion. One non-contour deforming carcinoma could be detected only with MRI and was only retrospectively visible on CT with an element of uncertainty. Magnetic resonance imaging using a CP body phased-array coil and fat-suppressed T1- and T2-weighted FLASH, SE, and turbo-SE sequences offers diagnostic possibilities in improved imaging of the pancreas.     

Evaluation of the anatomical and functional properties of deglutition with various kinetic high-speed MRI sequences

We evaluated various fast MR sequences for obtaining anatomical and dynamic functional information during deglutition. Seven healthy volunteers underwent MRI of the oropharynx during swallowing of an oral positive-contrast agent. Single-slice imaging was performed in the median sagittal plane while subjects were in a supine position. Twenty serial images were obtained using EPI, FLASH, and turbo-FLASH sequences. The dynamic (movement-related) information and the anatomical resolution of the soft tissues were evaluated during deglutition. The FLASH sequence provided high-quality images at rest. During swallowing, however, the images were significantly degraded by movement artifacts and had inferior temporal resolution. The EPI evidenced better temporal resolution, but was degraded by strong distortions and movement artifacts. The turbo-FLASH sequence provided the best temporal resolution and sufficient spatial resolution during motion. This sequence proved optimal for the investigation of swallowing function, and is expected to be of value for the documentation of functional disturbances in patients with oropharyngeal pathology.     

Fast breath-hold T2-weighted MRI of the kidney by means of half-Fourier single-shot turbo spin echo: comparison with high resolution turbo spin echo sequence

PURPOSE: The value of the fast half-Fourier single-shot turbo spin echo (HASTE) sequence in T2-weighted MRI of the kidney was evaluated as a substitute for the conventional turbo spin echo (TSE) sequence. METHOD: Forty-five patients with suspected abnormalities of the kidney underwent MRI with a 1.5 T system. Breath-hold HASTE and respiratory-triggered TSE sequences were performed. Qualitative and quantitative analyses were performed for comparison of these sequences. RESULTS: The signal-to-noise ratio (SNR) with HASTE was higher than that with TSE. The lesion-to-kidney contrast-to-noise ratio for solid masses with HASTE was almost equal to that with TSE. For cystic masses, the CNR with HASTE was significantly higher than that with TSE (p < 0.05). Respiratory and chemical shift artifacts were significantly smaller on HASTE than on TSE (p < 0.01). However, the blurring artifact was higher on HASTE than on TSE (p = 0.01). CONCLUSION: The HASTE sequence generates high contrast images and is free of motion and chemical shift artifacts, with much better time efficacy. The sequence provides comparable diagnostic information to TSE sequences.     

Effectiveness of MR imaging for diagnosing the mild forms of acute pancreatitis: comparison with MDCT

PURPOSE: To assess the usefulness of MRI and determine which MR sequence is most effective for diagnosing the mild forms of acute pancreatitis. MATERIALS AND METHODS: Forty subjects (20 normal volunteers and 20 patients with a mild form of acute pancreatitis) underwent MRI with fat-suppressed T1-weighted fast low-angle shot (FLASH), half-Fourier acquisition single-shot turbo spin-echo (HASTE), and TSE short TI inversion recovery (TSE-STIR) sequences. The 20 patients with a mild form of acute pancreatitis underwent multidetector CT (MDCT) and MRI within a 24-hour interval. We qualitatively analyzed all of the images by assessing inflammatory changes in the pancreas and peripancreatic fat. We quantitatively compared differences in pancreas-liver contrast between the control and patient groups for each MR sequence by measuring the signal intensities of the pancreas and liver. RESULTS: TSE-STIR was the best of the four modalities for delineating peripancreatic and pancreatic inflammation (P < 0.01). TSE-STIR depicted definitive peripancreatic and pancreatic inflammation in 18 and 15 patients, respectively. MDCT depicted only three cases of peripancreatic inflammation. TSE-STIR was also produced the best the best quantitative results of the MR sequences (P = 0.09). CONCLUSION: MRI is helpful for diagnosing the mild forms of acute pancreatitis. We recommend the use of TSE-STIR imaging as part of the routine protocol for evaluating pancreatitis.     

MR enteroclysis protocol optimization: comparison between 3D FLASH with fat saturation after intravenous gadolinium injection and true FISP sequences

The aim of this study was to introduce the true fast imaging with steady-state precession (FISP) sequence for MR enteroclysis and compare it with the already used T1-weighted fast low-angle shot (FLASH) sequence. Twenty-one patients underwent both MR and conventional enteroclysis. The MR enteroclysis examination was performed after administration of an iso-osmotic water solution through a nasojejunal catheter and the following sequences were included: (a) true FISP; and (b) 3D FLASH with fat saturation after intravenous injection of 20 mg Buscopan or 1 mg glucagon and 0.1 mmol/kg gadolinium chelates. The true FISP sequence provided images with significantly fewer motion artifacts, whereas 3D FLASH was less sensitive to susceptibility and chemical shift artifacts. The homogeneity of endoluminal opacification, wall conspicuity, and distention of the small bowel were very good to excellent and the two sequences presented no statistically significant differences here. True FISP provided significantly better overall image quality than did 3D FLASH. The true FISP sequence can provide good anatomic demonstration of the small bowel on T2-like images and could be combined with T1-weighted FLASH images for an integrated protocol of MR enteroclysis.     

Incremental flip angle snapshot FLASH MRI of hepatic lesions: improvement of signal-to-noise and contrast.

Incremental flip angle (IFA) snapshot fast low angle shot (FLASH) is a new modification of inversion recovery snapshot FLASH MR imaging. The method changes the flip angle incrementally from low to high during data acquisition and was applied in the evaluation of 16 focal hepatic lesions in 10 patients. Sequence comparisons were performed with a fixed flip angle inversion recovery snapshot FLASH sequence (standard), a T1- and T2-weighted spin-echo (SE) sequence, and a T1-weighted breath-hold FLASH sequence. Whereas snapshot FLASH images in both pulse sequences were free from physiological motion artifacts, SE and FLASH images showed respiratory artifacts in some patients. Quantitative analysis of IFA snapshot FLASH images at low hepatic and low lesion signal revealed both superior lesion-liver signal-difference-to-noise ratio (SD/N) and superior contrast compared with standard snapshot FLASH without additional artifacts. Unless motion artifacts were evident, SE and FLASH images showed a higher anatomic resolution but lower SD/N and lower contrast than IFA snapshot images. Because of its superior SD/N and contrast, IFA snapshot FLASH will likely widen the application of fast MR imaging techniques.