Gadolinium-enhanced phase-contrast magnetic resonance portography.

PURPOSE: The purpose of this study was to investigate the effect and usefulness of gadolinium-chelated contrast medium in phase-contrast magnetic resonance (MR) portography. METHODS: Twenty-six patients (21 men, 5 women; aged 34 to 79 years, mean 62 years) underwent respiratory-triggered 3-dimensional phase-contrast portography before and after administration of gadolinium in a 1.5T MR unit. Coronal maximum intensity projection (MIP) images of the portal vein were reconstructed and compared to conventional arterial portograms regarding visualization. Signal-to-noise ratio (SNR) and portal vein-to-liver contrast-to-noise ratios (CNR) of main, right, right anterior, right posterior, left portal veins, and umbilical portion were measured on both non-enhanced and gadolinium-enhanced images and compared. RESULTS: Portal veins and branches were more clearly visualized on the gadolinium-enhanced than on the non-enhanced images. Compared to arterial portography, gadolinium-enhanced portography showed similar performances in visualization, except in the right posterior branch and left portal vein. No severe image degradation from respiration was experienced. SNR was significantly higher on the gadolinium-enhanced than on non-enhanced images except in the right anterior branch. CNR was significantly higher on the gadolinium-enhanced than on the non-enhanced images at all measured locations. CONCLUSIONS: Administration of gadolinium improves the SNR and CNR of phase-contrast portography and visualization of the portal vein. The phase-contrast technique with gadolinium enhancement can be used to evaluate the portal vein as a supplemental technique.     

磁共振门静脉成像技术探讨

目的：通过改变翻转角试图优选出一种最佳翻转角的快速准确的磁共振门静脉血流成像方法，并尽可能消除呼吸运动的影响。材料与方法：采用Ｓｉｇｎａ１．５Ｔ磁共振仪随机对５８例上腹部ＭＲ检查者进行门脉血流成像，其中快速梯度回波间断闭气扫描１８例，采用２０°、３０°和４５°三种不同翻转角。梯度回波加呼吸门控法共扫描４０例，均采用３０°翻转角。所有图像均经三维处理，并采用双盲法评价门脉显示效果。结果：间断闭气ＭＲ门脉成像选择３０°翻转角，图像信噪比、对比度及血管亮度比２０°或４５°为优，此技术受呼吸影响较大，而呼吸门控技术的运用可大大消除呼吸运动的影响。结论：选择３０°翻转角并加用呼吸门控的门脉血流成像技术是较为有效的门脉成像方法之一，它能较好地显示门脉主干及分支，对诊断和手术治疗方案的制定有一定的帮助     

Contrast-enhanced three-dimensional MR portography.

Three-dimensional (3D) magnetic resonance (MR) portography with contrast material enhancement is a fast means of evaluating the portal venous system that has some advantages over currently used modalities, such as digital subtraction angiography, helical computed tomography, ultrasonography, and nonenhanced MR angiography with time-of-flight and phase-contrast techniques. With contrast-enhanced 3D MR portography, a first-pass study of the mesenteric vasculature is performed after rapid bolus injection of gadopentetate dimeglumine; a 3D fast field echo sequence is used, which can demonstrate the intrahepatic and extrahepatic portal venous system clearly. Repeated sequences after administration of gadopentetate dimeglumine allow separate demonstration of the splanchnic arteries and portomesenteric veins. The images are reconstructed by means of maximum-intensity projection postprocessing, and a subtraction technique can be used to eliminate arterial enhancement and demonstrate portosystemic shunts. The coronal source images simultaneously demonstrate parenchymal lesions of the liver, pancreas, biliary tract, and spleen. This technique is clinically indicated in portosystemic shunt, portal vein thrombosis, hepatocellular carcinoma, pancreatobiliary tumor, hepatic vein obstruction, differentiation of splanchnic arterial from portal venous disease, and gastrointestinal hemorrhage. Its limitations include allergic reactions to contrast media, inappropriate positioning of the 3D acquisition slab, respiratory motion artifacts, and pseudodissection.     

Dynamic contrast enhanced magnetic resonance imaging subtraction in evaluating osteosarcoma response to chemotherapy

PURPOSE: To evaluate the results of a new technique of dynamic contrast enhanced Magnetic Resonance (MR) imaging subtraction in the assessment of osteosarcoma response to chemotherapy. METHODS: 24 patients with high grade osteosarcoma, treated with preoperative neo-adjuvant chemotherapy, underwent MR at high field strength (1.5 T). Both unenhanced conventional SE T1- and T2-weighted sequences in the coronal and axial plane and dynamic Gd-DTPA-enhanced SE T1-weighted sequences in the coronal plane were performed. Image postprocessing included subtraction of unenhanced image from enhanced images (arbitrary called "angiographic subtraction") and subtraction of each enhanced image from the last-enhanced image (arbitrary called "pathologic area" subtraction). The early enhancing areas detected in the angiographic subtraction and the pathologic areas detected in the pathologic area subtraction were correlated with histopathological findings on histological macrosections obtained from the resected specimen. The sensitivity, specificity, accuracy, positive and negative predictive value of both the subtraction techniques were calculated. RESULTS: The early enhancing areas of angiographic subtraction were related not only to viable tumor but also to the host reactions such as flogosis and granulation tissue. The pathologic areas detected at the pathologic area subtraction correlated in most cases with viable tumor, while in 3 cases they did not correspond to viable tumor tissue and in 1 case a small area of residual viable tumor was missed. In assessing response to chemotherapy, pathologic areas subtraction had an accuracy of 95% (specificity: 100%, sensitivity: 93%, PPV: 100%, NPV: 88%), whereas angiographic subtraction had an accuracy of 79% (specificity: 37%, sensitivity: 100%, PPV: 76%, NPV: 100%). CONCLUSIONS: Pathologic area subtraction may be a useful technique for assessing the response of osteosarcoma to chemotherapy and for detecting residual viable tumor tissue.     

Value of subtraction in fat-saturated three-dimensional contrast-enhanced magnetic resonance angiography of the hemodialysis fistula

Purpose: To evaluate image subtraction in a three-dimensional contrast-enhanced magnetic resonance angiography (3D CE-MRA) using fat suppression for the hemodialysis fistula.

Material and Methods: Fifteen patients suffering from hemodialysis fistula dysfunction were imaged with 3D CE-MRA using fat suppression and digital subtraction angiography (DSA). Non-subtracted and subtracted MRA images using maximum intensity projection (MIP) were constructed and the validity of the MRA interpretations of the degree of vascular stenoses was evaluated using DSA as the standard of reference. Image quality was assessed using qualitative analysis (vessel contrast) and quantitative analysis (contrast-to-noise ratio (CNR) of the vessel versus the background).

Results: In the vessels with stenosis of 50% or greater, the sensitivity and specificity of the non-subtracted MRA were 89.5% and 81.8%, respectively, and of the subtracted MRA 89.5% and 86.4%, respectively. There was no significant difference in the detectability of stenoses between either MRA. The vessel contrast of the anterior interosseous artery and the CNR of the anterior interosseous artery versus the background on the subtracted MRA were significantly superior to those on the non-subtracted MRA. With regard to the radial artery and cephalic vein, there was no significant difference in the vessel contrast and CNR between either MRA.

Conclusion: Both subtracted and non-subtracted MRA techniques are useful in detecting hemodialysis fistula dysfunction.     

Gadolinium DTPA in magnetic resonance. Clinical experience in intracranial pathology

Sixty-seven patients with various intracranial pathologies were studied using Gd-DTPA as a contrast medium applied to MRI. This paramagnetic substance was well tolerated by all patients, and proved particularly useful in improving the diagnosis of extra-axial tumors, in which a rich enhancement was always present. Gd-DTPA allowed a better definition of the tumor outlines, as well as its differentiation from edema, and the demonstration of its relationship to brain parenchyma and cerebral vessels. This was particularly true for meningiomas, which often display poor contrast enhancement at MRI. Even though acoustic neuromas had, as a rule, high signal intensity, Gd-DTPA was useful to precisely recognize the intracanalar part of the tumor. The value of Gd-DTPA was less evident in intra-axial lesions. It proved nonetheless useful in demonstrating the portions of the tumor where, due to alterations in BBB, enhancement was present. This allowed both to characterize the lesion and to perform accurate biopsies.     

Three-phase dynamic breast magnetic resonance imaging with two-way subtraction

OBJECTIVE: This study was undertaken to introduce a new breast magnetic resonance (MR) imaging technique, 3-phase dynamic MR imaging with 2-way subtraction, and to examine the morphologic and kinetic features of malignant and benign breast lesions using this technique. METHODS: In 99 breasts from 89 consecutive women with suspicious breast lesions (age range: 32-72 years, mean = 48.2 years), MR imaging was performed using a fat-saturated, sagittal, gradient-echo sequence in 3 phases (1 precontrast and 2 postcontrast scans). Two-way subtraction was performed: standard subtraction (early postcontrast minus precontrast scans) and reverse subtraction (early postcontrast minus late postcontrast scans). A radiologist interpreted all the images, described the breast lesions (using the Breast Imaging Reporting and Data System MR lexicon), and assessed the lesions prospectively as being benign or malignant. The lesions with at least 1 malignant feature were classified as malignant. The MR classifications were compared with the biopsy or follow-up results. RESULTS: Sixty-five (65.7%) breast lesions were malignant, and 34 (34.3%) were benign. Forty-two (97.7%) of the 43 cases of microinvasive or invasive ductal cancer showed malignant morphologic features, and 38 (88.4%) showed washout kinetics. Eighteen (81.8%) of the 22 cases of ductal carcinoma in situ showed malignant morphologic features, and 11 (50.0%) showed washout kinetics. Twenty-nine (85.3%) of the 34 benign lesions showed neither malignant morphologic features nor washout kinetics. The sensitivity and specificity were 92.3% and 91.2% by morphologic analysis and 93.8% and 85.3% by the combined method (morphology plus kinetic analysis), respectively. CONCLUSIONS: This study demonstrated that 3-phase dynamic breast MR imaging with 2-way subtraction and a maximum intensity projection (MIP) image is a simple and useful technique for identifying breast lesions. Although the addition of the kinetic criteria enhanced the sensitivity at the cost of specificity, radiologists can diagnose a malignant lesion showing non-mass-like enhancement more confidently using reverse subtraction imaging. Therefore, this study proposes 3-phase dynamic imaging with 2-way subtraction and an MIP image as one of the standard protocols of breast MR imaging.     

Magnetic resonance portography using contrast-enhanced fat-saturated three-dimensional steady-state free precession imaging

PURPOSE: To assess the feasibility of contrast-enhanced fat-saturated three-dimensional steady-state free precession (FIESTA) imaging for contrast-enhanced magnetic resonance (MR) portography. MATERIALS AND METHODS: Contrast-enhanced fat-saturated three-dimensional fast spoiled gradient-echo (SPGR) and FIESTA were performed as MR portography. In 10 cases, fat-saturated three-dimensional FIESTA was first performed and followed by fast SPGR, and the order of post-contrast imaging was reversed in the other 10 cases. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were estimated for portal and visceral veins on the source images. The visualization of portal vein was scored on three-dimensional MR portography. Portal venous system disorders were assessed using three-dimensional MR portography. RESULTS: The SNRs, CNRs, and visual assessment of portal and visceral veins were significantly higher in contrast-enhanced fat-saturated three-dimensional FIESTA than contrast-enhanced fat-saturated three-dimensional fast SPGR (P < 0.05). The contrast-enhanced fat-saturated three-dimensional FIESTA provided high venous signals even at 8 minutes after gadolinium injection. The abnormalities of portal venous system were well visualized with MR portography using contrast-enhanced fat-saturated three-dimensional FIESTA. CONCLUSION: Contrast-enhanced fat-saturated three-dimensional FIESTA was valuable for MR portography, with flexible time window and high vascular signals. This imaging may allow for other post-contrast imaging options before portography and release patients from consecutive breath-holds.     

Non‐contrast‐enhanced vascular magnetic resonance imaging using flow‐dependent preparation with subtraction

Recent concerns over contrast agent safety have encouraged new developments in non‐contrast‐enhanced vascular imaging techniques. This work investigates the potential for imaging both arteries and veins with vascular anatomy by nonenhanced static subtraction angiography (VANESSA), a method using controllable flow suppression together with subtraction of bright‐ and dark‐blood images. The lower legs of eight healthy volunteers and three patients were imaged using a modified motion‐sensitized driven equilibrium preparation, with three‐dimensional balanced steady‐state free precession readout. The vascular signal decreased with increasing motion‐suppression gradient amplitude, and was suppressed when the velocity‐encoding parameter was (approximately) less than the measured flow velocity. Selected pairs of images were subtracted to depict vessels with either fast flow (e.g. arteries), slow flow (e.g. veins), or both. Several methodological modifications improved image quality and reduced the background signal from static tissues. Subjectively assessed image quality in volunteers was rated as excellent for 56/64 arterial segments, and good or excellent for 35/64 veins. In conclusion, VANESSA enables rapid non‐contrast‐enhanced imaging of arteries and veins, combining information on both morphology and flow. This study demonstrates good technical performance in volunteers and evaluation in patients with vascular disease is warranted. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

Structure enhancement by subtraction in magnetic resonance imaging

Two patients with tumours in the pituitary gland and the liver, respectively, were studied with MRI. Regions of different transverse relaxation times were found in the tumours. Subtraction of images recorded with different echo times demonstrated the tumour regions better than the original images although these were recorded with 2 repetition times and double and multiple echo sequences. Subtraction techniques may thus aid diagnosis in MRI.     

透视触发技术在椎动脉三维增强磁共振血管成像的应用分析

三维增强磁共振血管造影（three dimension con：rast enhanced MR angiography.3D CE-MRA）利用对比剂造成血管组织间的对比进行血管成像．因其具有简便易行、图像清晰的特点在临床上应用越来越广。在椎动脉3DCE-MRA中,为了捕捉到椎动脉显影最佳时相并减少静脉重叠,     

增强减影MRI诊断椎体转移瘤的研究

目的:探讨增强减影MRI对椎体转移瘤的诊断价值。方法:对30例41个椎体行常规MR平扫及增强扫描,并在增强后对病灶同一层面进行叠加减影处理。结果:增强减影MRI能清晰显示椎体内骨小梁结构,更容易发现微小病灶,更好地显示转移性肿瘤的形态学特点。结论:增强减影MRI技术对提高脊椎转移瘤的检出率有重要的临床应用价值。     

Gadolinium zeolite as an oral contrast agent for magnetic resonance imaging

The purpose of thls study was to evaluate efficacy and safety of a gadolinium (Gd) zeolite suspension aa an oral MRI contrast agent. Serial dilution of GADO- LITE@ orpl Suspdon 1.2500 pg of GdO/mL) were prepared. MRI (T1 and T2 welghted) of standards and dogs (precontrast and postcontraat) were performed. Toxicity and Gd absorption were also asmaued. Subsequently, 30 nod male adult volunteers were divided into six group of five subjects each. Gd zeolite po suspension waa adminlstered before and after MRI in volumes and concentrations ranging from 250 to 1600 mL; 6 to 80 pg of Gd⁺³/mL. The images were rated (efficacy score) by a bllnded reader. Vital signs, blood chemistries and urlnalysia were recorded. Gadollte Oral Suspension produced excellent enhancement of the dog gastrointestinal (GI) tract. No todclty or absorption of Gd wan obsenred in dogs receiving doses up to 4 times the anticipated human dose My for 14 consecutive days. In clinical tri.lr. Gd zeollte slgnlficantly lmproved the efficacy scores for all groups and all pulrina sequences (all P values <.05). Efflcacy scores and slgnal intendtics generally increased with concentration and volume. No Gd waa detected in blood or urine specimens. No signiftcant adverse events were reported. Gd zeolite 1s a promlsing contrast medium for enhancement of the GI tract in MRI.     

Registration of three-dimensional magnetic resonance and radionuclide skeletal images.

PURPOSE: To apply postprocessing techniques to register three-dimensional TI-201 bone SPECT datasets with MRI. This may provide more accurate anatomic-functional correlation when localizing active tumors. MATERIALS AND METHODS: Three-dimensional datasets were constructed from previously acquired MRIs using routine imaging protocols. Registration software was used to coregister the TI-201 SPECT studies and the MRIs in three dimensions. RESULTS: Adequate TI-201 uptake in muscles and soft tissues along with relatively low accumulation in tendons and joint spaces provided adequate landmarks for visually aligning SPECT and MRI datasets. MR abnormalities were more extensive because of surrounding reactive tissue, and more focal TI-201 uptake could be demonstrated within the region of MR signal abnormality, allowing the focal metabolically active tissue to be distinguished from adjacent edema. CONCLUSIONS: Image registration of SPECT and anatomic imaging (CT or MRI) is used routinely to evaluate functional abnormalities within the brain. This technique has now been applied to the combination of TI-201 SPECT and MR data for evaluating bone lesions and may provide additional anatomic information for localizing functional abnormalities. This may be valuable for defining targets for biopsy, planning surgical treatment, and using minimally invasive therapies.     

Contrast-enhanced three-dimensional magnetic resonance angiography of the mesenteric vasculature.

The diagnosis and treatment of mesenteric occlusive disease is important due to the high morbidity and mortality associated with ischemia of the bowel. This article describes the application of magnetic resonance angiography (MRA) as a minimally invasive tool for diagnosing mesenteric and portal vascular disease. The techniques for three-dimensional (3D) contrast-enhanced MRA and flow measurement of the mesenteric circulation are described. Excellent image quality is obtained using sagittal contrast-enhanced 3D MRA of the aorta and proximal mesenteric vessels. Delineation of the small distal mesenteric branch vessels is still limited due to the finite spatial resolution of MRA. The application of MRA techniques to the diagnosis of mesenteric ischemia, revascularization, transplantation, and portal hypertension are demonstrated. Finally, the merits of various acquisition techniques and future contrast agents are discussed. MR angiography using intravenously administered contrast agents provides the clinician with a powerful, minimally invasive method for diagnosing mesenteric vascular disease.     

Fast magnetic resonance coronary angiography with a three-dimensional stack of spirals trajectory.

In this work, three-dimensional (3D) spiral imaging has been utilized for magnetic resonance coronary angiography. Spiral-based 3D techniques can dramatically reduce imaging time requirements compared with 3D Fourier Transform imaging. The method developed here utilized a "stack of spirals" trajectory, to traverse 3D k-space rapidly. Both thick-slab volumes encompassing the entire coronary tree with isotropic resolution and thin-slab volumes targeted to a particular vessel of interest were acquired. Respiratory compensation was achieved using the diminishing variance algorithm. T2-prepared contrast was also applied in some cases to improve contrast between vessel and myocardium, while off-resonance blurring was minimized by applying a linear correction to the acquired data. Images from healthy volunteers were displayed using a curved reformatting technique to view long segments of vessel in a single projection. The results demonstrate that this 3D spiral technique is capable of producing high-quality coronary magnetic resonance angiograms.     

单次屏气三维对比增强磁共振门静脉造影

目的探讨中次收气三维对比增强门静脉造影（3DCEMRP）方法并初步评价其临床应用价值。方法39例病人接受3DCEMBP检查及三维时间飞越法（2DTOF）门静脉成像，其中无肝脏疾患者8例，肝硬化18例，肝癌12例，脾静脉血栓形成1例，Gd-DTPA用量为每公斤体重0.1～0.2mmol，用团注实验剂量确定门静脉峰值通过时间及扫描延迟时间，所有图像分别经最大信号强度投影（MIP）重建，评价门静脉成像质量、开放程度、侧支血管及从静脉曲张的情况。结果门静脉内造影剂峰值通过时间为17～45秒，所有病例3DCE哑MRP成像质量明显优于2DTOF门静脉成像。8例无肝脏疾病者，CEMRP均完整显示门静脉主干及肝内4级以上的分支；18例肝硬化中有17例显示门、脾静脉扩张迂曲，其中10例显示食管胃底静脉曲张，1例门静脉主干近段闭塞，12例肝癌中，5例门静脉主干和（或）其主分支闭塞，6例显示肝内门静脉分支受压、移位；1例脾静脉血栓形成，见脾静脉闭塞及广泛的侧支血管。结论3DCEMRP为一快速、有效评价门静脉系统的检查方法。