腹部磁共振成像的临床应用──探讨和比较几种扫描脉冲序列

笔者通过分析１００例腹部ＭＲＩ图像，研究和比较３对扫描脉冲序列的应用；研究结果表明：（１）Ｔ＿１加权像脉冲序列，快速ＳＰＧＲ（屏气）扫描速度快、呼吸伪影少、流动伪影多；而ＳＥ序列扫描时间长、流动伪影少、呼吸伪影多些；两者脉冲序列图像中解剖分辨和病变显示率相似（Ｐ＞０．０５，无显著差异）。（２）Ｔ＿２加权像脉冲序列，ＦＳＥ序列扫描时间短、呼吸伪影和流动伪影多；而ＳＥ序列扫描时间长、呼吸伪影和流动伪影少些；ＦＳＥ和ＳＥ图像中病变显示率相似（Ｐ＞０．０５，无显著差异）；ＳＥ图像中解剖分辨好于ＦｓＥ（Ｐ＜０．０１．有极显著差异）。（３）Ｔ＿２加权像加脂肪抑制序列图像中呼吸伪影、化学位移伪彤少，解剖分辨和病变显示清晰度均好于Ｔ＿２加权像不加脂肪抑制序列（Ｐ＜０．０ｌ，有极显著差异）。     

预饱和脂肪抑制技术在乳腺MRI检查中的临床应用

目的 探讨预饱和脂肪抑制技术在乳腺MRI检查中的临床应用价值。资料与方法 对58例乳腺疾病患者进行常规MRI平扫、脂肪抑制MRI平扫和脂肪抑制动态增强MRI扫描，对比分析SE TlWI、FSE T2WI、脂肪抑制SE T1WI、脂肪抑制FSE T2WI和脂肪抑制SE T1WI增强扫描5种图像对病变的检出情况及病变形态和内部信号的显示效果。结果 (1)对病变的检出，脂肪抑制增强扫描明显优于平扫各图像，检出率达100％，平扫各图像对病变的检出无显著性差别，其中以脂肪抑制T2WI为最好，检出率为93．1％，脂肪抑制T1WI最差，检出率为85．06％；(2)在病变形态的显示上，虽然脂肪抑制T2WI效果较好，但与常规T2WI相比并无显著性差别，而脂肪抑制的增强扫描则明显优于平扫各图像；(3)在病变内部信号的显示方面，脂肪抑制的平扫(包括T1WI、T2WI)明显优于常规平扫，而脂肪抑制的增强扫描明显优于平扫各图像。结论 乳腺MRI平扫中脂肪抑制的应用对病变的检出及内部信号的显示具明显优势，以脂肪抑制T2WI效果更好；在脂肪抑制基础上进行动态增强扫描不仅对病变强化的形态学特征显示良好，明显提高病变的检出率，而且能准确判断病变强化程度，观察病变血流灌注的动态变化过程．明显提高了MRI对乳腺疾病诊断的准确性，因此预饱和脂肪抑制技术在乳腺MRI增强扫描中的应用具有重要价值。     

磁共振减影技术在脑膜显像中的应用

目的　评价一种简便的磁共振减影方法对正常脑膜成像的显示效果。方法　对 45例无颅脑疾患的志愿者行颅脑磁共振增强成像 ,对增强前后T1加权像行减影处理。选取不同的解剖层面 (后颅窝四脑室、大脑脚、侧脑室体和半卵圆中心 4个平面 ) ,通过主观判断和客观测量等方法评价、比较各解剖层面正常脑膜及软膜血管在减影图像与常规增强T1加权图像中的显示。结果　在 87%的受检者中 ,常规增强T1加权图像显示正常脑膜及软膜血管强化呈短片段 ,而减影图像则多呈连续强化。 2种成像方法显示强化脑膜范围与强化长度在所有解剖层面上均有显著性差异 (Ρ <0 .0 1)。减影图像中脑膜及软膜血管强化信号强度相对比值明显高于常规增强T1加权图像 (Ρ <0 .0 1)。主观评价脑膜强化均为轻到中度。结论　减影技术是一种能明确显示脑膜强化的简便方法。     

眶内及眶旁病变:脂肪抑制结合顺磁性增强MRI的价值

在眶内及眶旁病变上,虽然MR顺磁性增强技术能改善病变与周围结构的区分,但脂肪量多时,区分强化结构与脂肪仍有困难。作者应用顺磁性对比剂增强结合脂肪抑制MR技术检查了18例眼眶。2例正常眼眶应用单纯脂肪抑制技术显示与正常T_1相反的对比,视神经、泪腺及眼外肌呈高信号与低信号的脂肪形成清楚的对比,管内视神经也由于周围脂肪和骨髓脂肪信号被消除而清楚显示。但增强后脂肪抑制T_1加权,眼外肌和泪腺明显强化,眼内结构之间的解剖分界显示更清楚。3例眼球病变中,2例脉络膜视网膜炎在增强后T_1加权、质子密度和T_2加权象上均未显示,仅在增强后结合脂肪抑     

正常胃的MRI表现与扫描技术

目的：研究正常胃的MRI表现和扫描技术。方法：在胃不同充盈状态下，采用单次屏气快速扫描序列，共进行72人次MRI平扫和7次增强检查，分析正常胃的MRI表现和图像质量。结果：按充盈程度不同，胃壁形态可分为扩张不良，适度扩张、充分扩张3型表现。MRI能较好显示胃及其与邻近器官的关系。胃壁厚度平均值在适度扩张下为2．7mm，在充分扩张下为2.4.T2WI图像均无运动伪影，79％的T1WI图像在使用解痉剂后无运动伪影。结论：采用单次屏气快速扫描序列，MRI能获得满意的胃部图像，较好显示胃及其与邻近解剖关系。     

SPIR扫描在诊断骨胳肌肉系统疾病中的应用

目的：探讨SPIR脂肪抑制技术在骨胳肌肉系统疾病MRI检查中的诊断价值。材料与方法：对36例骨、关节软组织疾病患者行T1W／SE、T2W／FSE及T2W／SPIR序列扫描，并对后两者进行比较。结果：各种病理性积液呈高信号；损伤性骨髓水肿呈高信号；骨折线呈低信号，如骨折断端出血则呈线状高信号；软组织肿瘤囊性部分呈高信号，实质部分呈中等强度信号；软组织炎症性病变为弥漫性高信号；骨病成骨性改变为低信号；骨髓病变为高信号或混杂等高信号；椎管内占位性病变及半月板损伤SPIR显示不清。结论：SPIR能提高正常组织与病变组织间的对比度，清晰地显示病变组织，作为T1W／SE、T2W／FSE序列的辅助检查，有助于提高骨胳肌肉系统疾病的诊断水平。     

球后病变的MRI信号特征及其诊断

目的：通过分析和掌握MRI信号征象，提高诊断和鉴别诊断球后病变能力。材料和方法：69例球后病变，术前接受了MRI检查。常规SE序列，T1加权和T2加权的多回波成像。结果：根据其MRI信号征象，大致可分为四种信号表现。多数非肿瘤性病变的MRI信号征象，不同于一般肿瘤性病变的信号改变，具有一定特征性改变。结论：MRI可以根据病变部位以及MRI信号特征对眼眶病变做出正确的定性诊断，为临床提供重要诊断和治疗依据。     

SEMAC技术在脊柱金属植入物MRI中的应用价值

目的 探讨层间编码金属伪影校正(SEMAC)技术在脊柱金属植入物磁共振成像(MRI)中的应用价值.方法 对30例行脊柱内固定术后的患者分别用常规TSE序列和SEMAC技术进行MRI,分别计算二者在轴位T2WI图像上金属伪影导致信号缺失区域的面积和矢状位T2WI、T1WI图像上脊髓被金属伪影所遮蔽的长度;另外对假体周围解剖结构(包括椎弓根、椎体、硬膜囊和椎间神经孔)的显示进行5分制评分.结果 运用SEMAC技术的图像上金属伪影导致信号缺失区域的面积明显低于常规TSE序列(t值为15.9,P值＜0.001),脊髓被遮蔽的长度也明显减小(t值分别为13.5、12.4,P值均＜0.001).假体周围各项解剖结构显示的评分,运用SEMAC技术的图像均高于常规TSE图像.结论 SEMAC技术可明显减少脊柱内固定术后MRI的金属伪影,为术后评估提供了重要的应用价值.     

成人椎间盘炎的MRI诊断

目的 评价MRI对成人椎间盘炎的诊断价值。方法 搜集经临床证实的28例椎间盘炎患者的MR影像资料，分析其MRI表现，比较各种成像方法的敏感性与特异性及其在鉴别诊断中的价值。MRI检查使用1．0T超导机，T1、T2加权像及脂肪抑制T2加权像，2例进行了增强检查。结果 75％的病变椎间盘呈不均匀长T2高信号；全组病例均有相邻椎体受累，两个及两个以上受累者达89％。病变椎体均呈显著长T1低信号，25例呈不均匀长T1高信号，脂肪抑制T2加权像上高信号改变更明显。5例可见椎体边缘骨质增生。椎体受累范围大于二分之一者达78．5％。5例椎体边缘骨质破坏、不完整，而82．1％的病变椎体均无明显外形改变。12例椎旁或椎管内可见局限性脓肿影。2例行Gd—DTPA增强后均可见椎间盘及病变椎体内显著异常强化。结论 MRI对成人椎间盘炎具有极高的敏感性与特异性，可准确鉴别本病与椎体结核与肿瘤，是临床上应作为首选的影像检查方法。     

儿童眼眶转移性神经母细胞瘤和绿色瘤的特征性MR表现

目的 分析儿童眼眶转移性神经母细胞瘤和绿色瘤的特征性MR表现。资料与方法 回顾性分析经手术病理证实的9例儿童眼眶转移性神经母细胞瘤和5例绿色瘤的CT和MRI表现。所有病例均行CT平扫以及MRI平扫和增强扫描。结果 14例CT表现均为眼眶不规则肿块和邻近的眶壁溶骨性骨质破坏，7例骨质破坏区邻近的颅内可见扁平不规则肿块。2例转移性神经母细胞瘤表现为眼眶肌锥外间隙肿块内有与眶外壁垂直的针状高密度影。14例MRI表现为眼眶肌锥外间隙略长T1、略长T2信号不规则软组织影，7例骨质破坏区邻近的颅内硬膜外间隙可见略长T1、略长T2信号扁平不规则肿块，增强后明显强化。14例双侧眶骨及蝶骨大翼，9例斜坡和双侧岩尖及2例双侧颞骨鳞部骨髓腔脂肪高信号影被略长T1、略长T2信号影取代，采用脂肪抑制的增强T1WI显示均有强化，强化程度与眼眶内肿块相似。结论 儿童眼眶转移性神经母细胞瘤和绿色瘤的眶壁和颅面骨MR表现具有特征，有助于诊断和鉴别诊断。     

Intra- and paraorbital lesions: value of fat-suppression MR imaging with paramagnetic contrast enhancement

The orbital area of 18 individuals was examined by using a combination of fat-suppression contrast-enhanced MR imaging to determine whether contrast between fat and surrounding tissues could be improved over that obtained with conventional fat-suppression techniques alone. We used a hybrid technique combining two independent methods of fat suppression. Subjects consisted of 16 patients and two normal volunteers. Fifteen individuals received gadopentetate dimeglumine, and conventional T1-weighted, T2-weighted, and fat-suppression T1-weighted images were obtained. The fat-suppressed T1-weighted images obtained after contrast administration provided more information than did the conventional MR images. Intraorbital and paraorbital lesions could be distinguished easily from intraorbital fat that had been suppressed. Cases of chorioretinitis and optic neuritis could be confidently diagnosed only by this technique. Cases of optic nerve meningioma and mixed conal lesions also were better appreciated. Because of sharp contrast between tissue planes, this technique was helpful for detecting any intraorbital invasion from paraorbital lesions. Fat-suppression MR imaging with paramagnetic contrast enhancement can significantly improve the delineation of both normal and abnormal structures and better define lesional margins in the orbit, where large amounts of fat are present. Our results support earlier findings, and we suggest that postcontrast fat-suppressed T1-weighted imaging be used instead of conventional T1-weighted postcontrast imaging in evaluating orbital and paraorbital lesions.     

Combined fat- and water-suppressed MR imaging of orbital tumors

BACKGROUND AND PURPOSE: The use of a high-resolution T2-weighted MR sequence, which suppresses signal from both fat and water, has been shown to be highly effective for depicting areas of inflammatory damage within the optic nerve. The ability of this sequence to show neoplastic and inflammatory orbital lesions, which may mimic neuritis, is unknown. This study was designed to examine the characteristics of such a sequence for the investigation of orbital mass lesions. METHODS: Twenty-eight patients with known or suspected mass lesions of the orbit and six healthy volunteers were recruited for study. Imaging was performed with a 1.5-T MR unit. Participants were examined by selective partial inversion recovery (SPIR) sequences with T2-weighted fast spin-echo acquisition, selective partial inversion recovery/fluid attenuated inversion recovery (SPIR/FLAIR) sequences with fast spin-echo acquisition, short tau inversion recovery (STIR) sequences with fast spin-echo acquisition, and SPIR sequences with contrast-enhanced T1-weighted fast spin-echo acquisition. Two neuroradiologists, using a randomised, blinded method, scored images for lesion presence and extent. Lesion extent was defined as the number of images with visible abnormality, and was compared with the standard of reference established at a later date by consensus review of all imaging sequences. The ability of the sequences to show the presence and extent of pathologic lesions was compared. RESULTS: The SPIR/FLAIR sequence showed both the presence and extent of orbital masses significantly better than did either STIR or T2-weighted SPIR sequences (P<.01 and P<.001, respectively). Contrast-enhanced T1-weighted SPIR images ranked better than SPIR/FLAIR images, although the difference failed to reach statistical significance. In the orbital apex, the SPIR/FLAIR technique was superior to all other techniques used. This reflected its ability to distinguish enhancing, pathologic lesions from enhancing, normal anatomy. CONCLUSION: SPIR/FLAIR is an appropriate screening technique for orbital masses and offers significant advantages over currently used fat-suppressed sequences for the investigation of orbital disease.     

Orbit, skull base, and pharynx: contrast-enhanced fat suppression MR imaging

The high signal intensity of fat on T1-weighted magnetic resonance images has limited the utility of gadopentetate dimeglumine in imaging of the extracranial head and neck. Enhancing lesions may be obscured either by proximity to fat or by chemical misregistration artifact. The authors evaluated the role of a gadolinium-enhanced fat suppression imaging technique in the detection of extracranial head and neck abnormalities in 29 patients. These studies were directly compared with conventional pre- and postcontrast T1- and T2-weighted SE sequences. In detecting and defining the extent of abnormalities, fat-suppressed images were superior to non-fat-suppressed gadolinium-enhanced T1-weighted images in the majority of cases (22 of 27 [81%]). Fat-suppressed images were particularly beneficial in the detection of perineural spread of tumor as well as in defining lesions situated within or adjacent to fat-containing areas such as the base of the skull. These findings demonstrate that fat suppression techniques in combination with gadolinium enhancement are of value in extracranial head and neck imaging and should replace conventional postcontrast T1-weighted SE imaging.     

Fat-suppressed MR of the orbit and cavernous sinus: comparison of fast spin-echo and conventional spin-echo.

PURPOSETo compare T2-weighted fat-suppressed fast spin-echo imaging with fat-suppressed conventional spin-echo imaging in the detection of normal intraorbital and pericavernous anatomy and orbital disease, and to determine the efficacy of fat saturation with T2-weighted fast spin-echo imaging of the cavernous sinus.METHODSContrast-to-noise ratios of normal intraorbital anatomy were calculated and compared in 10 consecutive patients using fat-suppressed fast spin-echo and conventional spin-echo T2-weighted images. Contrast-to-noise ratios of common intraorbital lesions were calculated and compared using fat-suppressed fast spin-echo and fat-suppressed conventional spin-echo. Qualitative evaluation was performed and compared for normal intraorbital anatomy using both fat-suppressed fast spin-echo and fat-suppressed conventional spin-echo in 16 patients. Qualitative evaluation for the detection of normal anatomic structures of the pericavernous region was performed and compared using fast spin-echo with and without fat suppression and fat-suppressed conventional spin-echo T2-weighted images in 16 patients. Fat saturation was performed using standard commercially available chemical saturation technique.RESULTSReduced imaging time allowed more acquisitions for fat-suppressed fast spin-echo images, which significantly improved visibility of intraorbital and pericavernous anatomy over fat-suppressed conventional spin-echo. Anatomic visibility was also improved because of reduced motion, phase encoding, and susceptibility artifacts. There was no significant difference between contrast-to-noise ratios for fat-suppressed fast spin-echo and fat-suppressed conventional spin-echo imaging of the lateral and medial rectus muscles. Contrast-to-noise ratios of fat suppressed fast spin-echo of orbital disease was significantly greater than contrast-to-noise ratios of fat-suppressed conventional spin-echo. Detection of several normal anatomic structures of the pericavernous region was significantly improved with non-fat-suppressed fast spin-echo over fat-suppressed fast spin-echo because of significantly reduced magnetic susceptibility artifact.CONCLUSIONSFat-suppressed fast spin-echo is superior to fat-suppressed conventional spin-echo for T2-weighted orbital imaging. Non-fat-suppressed fast spin-echo is the preferred pulse sequence for T2-weighted imaging of the cavernous sinus because of the minimal susceptibility artifact.     

Fast and ultrafast magnetic resonance imaging in renal lesions

Our purpose was to analyze and compare the image quality and contrast-to-noise ratio (CNR) of different fast T1- and T2-weighted sequences with conventional spin-echo sequences in renal MRI. Twenty-three patients with focal renal lesions were examined with a T2-weighted ultrafast turbo spin-echo (UTSE) sequence with and without frequency selective fat suppression (SPIR), a combined gradient-and-spin-echo sequence (GraSE), and a conventional spin-echo sequence (SE). In addition, T1-weighted images were obtained pre-and postcontrast, using a fast spin-echo sequence (TSE) with and without SPIR and the conventional SE sequence. Among the T2-weighted images, the highest CNR and the best image quality were obtained with the UTSE sequence, followed by the fat-suppressed UTSE sequence. GraSE and conventional SE sequences showed a significantly lower CNR and image quality (p < 0.05). The T1-weighted sequences did not show significant differences, in either precontrast or postcontrast measurements. T2-weighted UTSE with and without fat suppression combined excellent image quality and high CNR for imaging and detection of renal lesions. The T1-weighted fast sequences provided no alternative to the gradient-echo or to the conventional SE sequences. The results of this systematic study suggest the use of T2-weighted fast techniques for improved diagnostic accuracy of renal MRI.     

In vivo intravascular MR imaging: transvenous technique for arterial wall imaging

PURPOSE: To determine, in vivo, the potential for transvenous magnetic resonance (MR) imaging of the arterial wall and to assess appropriate MR pulse sequences for this method. MATERIALS AND METHODS: MR imaging was performed on 19 vessels (right renal artery, N = 9; left renal artery N = 2; external iliac artery, N = 4; abdominal aorta, N = 4) in nine swine. The animals were either low-density lipoprotein receptor knockout (N = 5) or Yucatan mini-pigs fed an atherogenic diet for 6 to 11 weeks (N = 4). The intravascular MR coil/guide wire (IVMRG) (Surgi-Vision, Gaithersburg, MD) was introduced via the external iliac vein into the inferior vena cava (IVC). The following electrocardiograph-gated MR pulse sequences were obtained: T1-weighted precontrast with and without fat saturation and T1-weighted postcontrast with fat saturation. Two observers scored wall signal and conspicuity and classified the vessel as normal, abnormal, or stented. Images were compared with histopathologic findings. RESULTS: The T1-weighted precontrast without fat saturation, T1-weighted precontrast with fat saturation, and T1-weighted postcontrast images correlated with histopathologic findings in 12 of 15 vessels, eight of 10 vessels, and 14 of 16 vessels, respectively. Abnormal histopathologic findings included: arterial wall thickening (N = 3), arterial dissection (N = 2), focal fibrous plaque (N = 2), adherent thrombus (N = 1). The T1-weighted postcontrast images were not compromised by artifacts and had the highest score for vessel wall signal and conspicuity. T1-weighted precontrast images were compromised by chemical shift artifact and poor blood suppression. Negligible artifacts were created by the platinum stent. CONCLUSION: The T1-weighted fat saturated postcontrast pulse sequence was superior to other sequences for transvenous MR imaging of the arterial wall.     

Usefulness of selective partial inversion recover (SPIR) sequences in optic nerve diseases]

PURPOSE: To evaluate the yield of SPIR sequences with fat suppression in the diagnosis of optic nerve lesions. MATERIAL AND METHODS: Ten patients with suspected optic nerve involvement on the basis of clinical data and abnormalities of visual evoked potentials were examined. MRI was performed with a 1.5 T unit (Philips NT 15) using T1 weighted conventional spin-echo and T1- and T2 weighted SPIR sequences with fat suppression. Axial images were obtained along the optic nerve course, while coronal images throughout the optic nerve axis; slices were 3 mm thick. Axial T2 weighted SPIR sequences were also performed with the volumetric technique (1.5 mm thickness); coronal and parasagittal reconstructions along the nerve axis were obtained too. After paramagnetic contrast medium injection, conventional T1 weighted and SPIR sequences were performed on axial and coronal planes. RESULTS: Optic nerve lesions consistent with the diagnosis of neuritis were demonstrated with T2 weighted images in 4 of 10 patients. No abnormalities and/or nerve enlargement were found on T1 weighted images. An enhancement area was seen after contrast medium injection in only one case. MRI showed a pilocytic astrocytoma in one patient and selective atrophy of the right optic nerve in another. MRI showed normal findings in 4 patients. CONCLUSIONS: T1 and T2 weighted fat-suppressed SPIR imaging of the optic nerve improves anatomical definition, lesion detection and characterization in optic nerve conditions.     

"Ivy sign" in childhood moyamoya disease: depiction on FLAIR and contrast-enhanced T1-weighted MR images

PURPOSE: To compare contrast material-enhanced T1-weighted and fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images with or without gadolinium in depicting the leptomeningeal ivy sign in children with moyamoya disease. MATERIALS AND METHODS: Twenty-nine sets of FLAIR and postcontrast T1-weighted MR images were available in 19 consecutive children with primary moyamoya disease confirmed with conventional and MR angiography. Contrast-enhanced FLAIR MR images also were available in 15 sets. Two pediatric radiologists reviewed FLAIR and postcontrast T1-weighted images in separate sessions for the leptomeningeal ivy sign and assigned a rating of "present," "absent," or "equivocal" by consensus. Unenhanced and contrast-enhanced FLAIR MR images were compared side by side to determine which better depicted leptomeningeal high signal intensities. RESULTS: Postcontrast T1-weighted MR images revealed the leptomeningeal ivy sign in 40 hemispheres (frequency of visualization, 71% [40 of 56 hemispheres]), whereas unenhanced FLAIR MR images depicted it in 26 hemispheres (frequency of visualization, 46% [26 of 56 hemispheres]). An equivocal rating was given in 21 hemispheres versus in 11 on FLAIR and postcontrast T1-weighted images, respectively. FLAIR and postcontrast T1-weighted images agreed in 40 hemispheres. There was no case with a positive rating on FLAIR images when postcontrast T1-weighted images were negative. Unenhanced FLAIR MR imaging was superior to contrast-enhanced FLAIR imaging in seven hemispheres, whereas enhanced FLAIR was better in four of 28 hemispheres. In the remaining 17, findings with each sequence were similar. CONCLUSION: Contrast-enhanced T1-weighted images are better than FLAIR images for depicting the leptomeningeal ivy sign in moyamoya disease.     

Improved detection and delineation of head and neck lesions with fat suppression spin-echo MR imaging.

To compare conventional and fat suppression MR imaging in their ability to detect head and neck lesions, we prospectively studied 17 patients with head and neck tumors and one normal volunteer. Five patients had benign tumors (one mixed cell tumor, one hemangioma, one lipoma, and two plexiform neurofibromas), 10 had malignant tumors (six squamous cell carcinomas, two minor salivary gland carcinomas, one lymphoma, and one malignant fibrous histiocytoma), and two had nonspecific lymphadenopathy. All subjects were studied with standard spin-echo T1- and T2-weighted images (T2-weighted imaging was done with and without fat suppression technique). In addition, T1-weighted images with contrast enhancement and fat suppression were obtained in nine patients. A four-point grading system was used for comparison of the conventional and fat suppression images. Grades ranged from 0 (unsatisfactory, the lesion cannot be seen) to 3 (excellent, the lesion and its margins can be seen clearly with sharp contrast from surrounding normal tissue). We found that postcontrast fat suppression T1-weighted images and fat suppression T2-weighted images were most useful; these sequences obtained an average score close to grade 3 (2.77 and 2.85, respectively). On the other hand, the conventional T2-weighted images had an average score of about 2 (1.82) and the conventional T1-weighted image had a score of about 1 (1.33). Fat suppression T2-weighted sequences generally were superior in cases of lymphadenopathies. Postcontrast T1-weighted images were most useful in a case of plexiform neurofibroma, owing to their fibrous component and lower proton density.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prostatic MR imaging performed with the three-point Dixon technique. Work in progress

The three-point Dixon technique is an enhancement of the original Dixon method for the creation of water- and fat-proton magnetic resonance (MR) images. With the three-point Dixon technique, three measurements of phase shift at 0, pi, and -pi between the fat and water resonances are employed. Compensation for B0 inhomogeneity leads to an error-free decomposition into water- and fat-proton images; an accurate B0 map is also created. The lack of chemical shift artifact in the water- and fat-selective MR images permits the application of narrow receive bandwidth for the creation of T2-weighted images with a high signal-to-noise ratio. The technique was applied in vivo with four healthy subjects, seven patients with prostatic carcinoma, and one patient with benign prostatic hypertrophy and compared with conventional T2-weighted imaging. The three-point technique yielded images with improved definition of normal intraprostatic structures and zonal anatomy and, in some cases of prostatic carcinoma, provided better visualization of extraprostatic spread of tumor.