增强 T1- FLAIR 序列和磁化传递对比技术诊断脑微小转移瘤

目的：对比分析增强 T1液体衰减反转恢复（T1- FLAIR）序列和磁化传递对比（MTC）两种序列对脑内微小转移瘤的应用价值。方法：对60例患有脑转移瘤的病人行常规扫描后采用 T1- FLAIR 和 T1 WI ＋ MTC序列增强扫描,分别统计增强后 T1- FLAIR 和 T1 WI ＋ MTC 序列显示转移瘤的数目、大小、位置等,并比较二者对微小转移瘤的显示能力及2种序列图像的病灶-背景的对比度/噪声（C/ Ns）值。结果：60例脑转移瘤中,共计235个病灶,增强后 MTC 序列显示了231个病灶,显示率为98.3%,T1- FLAIR 序列显示了227个病灶,显示率为96.6%。T1 WI ＋ MTC 序列发现了 T1- FLAIR 序列不能显示的4个病灶,而 T1- FLAIR 序列证实了 T1 WI ＋ MTC 序列误判的2个病灶。T1 WI ＋ MTC 图像病灶-背景的 C/ Ns 值为29.85±6.43,T1- FLAIR图像病灶-背景的 C/ Ns 值为14.54±7.64,T1 WI ＋ MTC 序列的 C/ Ns 值高于 T1- FLAIR 序列的 C/ Ns 值（t=7.05,P ﹤0.05）。结论：增强 T1 WI ＋ MTC 序列和增强 T1- FLAIR 序列相互补充,二者结合能够最大程度满足微小转移瘤的显示和鉴别诊断的需要。     

Magnetic resonance imaging of musculoskeletal lesions: Comparison of three fat-saturation pulse sequences

Fat-saturation (FS) pulse sequences can improve the detection of musculoskeletal lesions. We prospectively compared contrast-enhanced T1-weighted FS spin-echo (SE) images, T2-weighted FS fast spin-echo (FSE) images and inversion recovery (IR) FSE images to determine if any of these three pulse sequences is superior for depicting bone marrow and soft tissue lesions. T1-weighted FS-SE images (400-680/10-20 [TR/TE]) after intravenous injection of gadoliniumdiethylenetriaminepentaacetic acid (DTPA), T2-weighted FS-FSE (2400-4200/96-112) and IR-FSE (3700-6000/12-14/170 [TR/TE/TI]) images were obtained with a 1.5-T magnet system in 35 patients. The visibility, margination and extent of 37 bone marrow and 67 soft tissue lesions, image uniformity, susceptibility and motion artefacts were qualitatively analysed by four radiologists. The number and size of lesions detected, the mean lesion signal-to-noise ratio (S/N) and contrast-to-noise ratio (C/N) were also statistically compared. More bone and soft-tissue lesions were detected on the IR-FSE and T2-weighted FS-FSE than the T1-weighted FS-SE images. The IR-FSE images were significantly better than the T2-weighted FS-FSE and T1-weighted FS-SE images for bone marrow lesion conspicuity (P<0.01). The soft-tissue lesions were also more conspicuous on the IR-FSE and T2-weighted FS-FSE images than on the T1-weighted FS-SE images (P<0.005). The lesion extent and image quality were similar on all three sequences while motion artefacts were most severe on the IR-FSE and least severe on the T1-weighted FS-SE images (P<0.001). Fat saturation was maximal on the IR-FSE images, resulting in a significantly higher mean ON of bone marrow lesions. The mean C/N of soft-tissue lesions was higher on the T2-weighted FS-FSE images although the differences were not significant. The T2-weighted FS-FSE and IR-FSE sequences are superior to the contrast-enhanced T1-weighted FS-SE sequence for depicting musculoskeletal lesions. Bone marrow lesion conspicuity is greater on the IR-FSE images, with comparable scan time and image quality but more motion artifacts.     

Perianal infections: Reader agreement and diagnostic performance of fat‐suppressed contrast‐enhanced MRI

We aimed to determine the diagnostic performance of the contrast‐enhanced fat‐suppression technique in the detectability of perianal infections and to compare this technique with different MR sequences used for this purpose. Thirty consecutive patients with clinically suspected anorectal infections were examined with fast spin‐echo (FSE) T2‐weighted, short‐inversion‐time inversion recovery (STIR), and fat‐suppressed and non‐fat‐suppressed T1‐weighted spoiled gradient‐echo (SGE) (in‐phase) dynamic contrast‐enhanced sequences. The results of MRI were correlated with the findings of surgery, which was considered as the standard of reference. Receiver‐operating‐characteristic curves were reconstructed to describe and compare the diagnostic value of each MR technique. The values of kappa were used as a measure of observer reliability. Diagnostic performances of STIR, FSE T2‐weighted and fat‐suppressed and non‐fat‐suppressed, contrast‐enhanced SGE T1‐weighted techniques showed statistically insignificant differences in detection of perianal infections. There was almost perfect interobserver agreement regarding the presence of lesions on each MR technique. Fat‐suppressed, contrast‐enhanced SGE T1‐weighted MRI showed adequate diagnostic performance in the detection of perianal infections. However, its significance is not different from the other MR sequences used for the present study.     

Two‐tone pancreas on T1‐weighted images: Correlation with abnormalities on magnetic resonance pancreatography

Two patients are presented in whom geographical alteration in signal between areas of normal and abnormal pancreatic tissue on T1‐weighted magnetic resonance images of the pancreas was observed. This alteration in signal intensity produced a ‘two‐tone’ pattern; magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangiopancreatography (ERCP) in both patients revealed altered pancreatic duct drainage. It is believed that the ‘two‐tone’ pancreas effect on T1‐weighted images of the abdomen, may indicate aberrant duct drainage and that MRCP is an ideal means of further evaluation.     

Primary central nervous system lymphoma in immunocompetent patients: a retrospective review of MRI features

Introduction: To define the features of primary central nervous system lymphoma (PCNSL) on MRI in immunocompetent patients. Methods: A retrospective review of the authors' institutional database was performed to identify histologically proven cases of PCNSL. Images were retrieved and reviewed with respect to location, lesion number, size, signal intensity, enhancement characteristics, oedema and necrosis. Results: Thirty‐one cases of histologically proven PCNSL had available imaging. One patient was excluded due to immunosuppression. Of the 30 remaining cases, the average age was 65.5 years, and males and females were equally represented. A total of 68 lesions (average of 2.5 per patient) were identified. With diffusion‐weighted imaging, all but two had restricted diffusion (40.3% mild and 55.6% marked) and all but one had enhancement (51.5% homogeneous, 42.6% heterogeneous and ring 4.4%). Most lesions were isointense to grey matter (75.8% on T2‐weighted image (WI) and 82.5% on T1‐WI). Oedema was mild in 43.4% and marked in 55.2%. Necrosis was seen in only five lesions (7.4%). On a per patient basis, 50% had bilateral lesions and 96.7% had lesions contacting a cerebrospinal fluid (CSF) surface. 16.7% of patients had posterior fossa involvement and 30% had lesions in the basal ganglia or thalami. Conclusion: The vast majority of cases of PCNSL in immunocompetent patients have lesions contacting a CSF surface, enhancement and restricted diffusion with no necrosis. These features should alert radiologists to the diagnosis of PCNSL.     

Pre- and post-contrast three-dimensional double inversion-recovery MRI in human glioblastoma

Fluid attenuated inversion recovery (FLAIR) MRI sequences have become an indispensible tool for defining the malignant boundary in patients with brain tumors by nulling the signal contribution from cerebrospinal fluid allowing both regions of edema and regions of non-enhancing, infiltrating tumor to become hyperintense on resulting images. In the current study we examined the utility of a three-dimensional double inversion recovery (DIR) sequence that additionally nulls the MR signal associated with white matter, implemented either pre-contrast or post-contrast, in order to determine whether this sequence allows for better differentiation between tumor and normal brain tissue. T1- and T2-weighted, FLAIR, dynamic susceptibility contrast (DSC)-MRI estimates of cerebral blood volume (rCBV), contrast-enhanced T1-weighted images (T1+C), and DIR data (pre- or post-contrast) were acquired in 22 patients with glioblastoma. Contrast-to-noise (CNR) and tumor volumes were compared between DIR and FLAIR sequences. Line profiles across regions of tumor were generated to evaluate similarities between image contrasts. Additionally, voxel-wise associations between DIR and other sequences were examined. Results suggested post-contrast DIR images were hyperintense (bright) in regions spatially similar those having FLAIR hyperintensity and hypointense (dark) in regions with contrast-enhancement or elevated rCBV due to the high sensitivity of 3D turbo spin echo sequences to susceptibility differences between different tissues. DIR tumor volumes were statistically smaller than tumor volumes as defined by FLAIR (Paired t test, P = 0.0084), averaging a difference of approximately 14 mL or 24 %. DIR images had approximately 1.5× higher lesion CNR compared with FLAIR images (Paired t test, P = 0.0048). Line profiles across tumor regions and scatter plots of voxel-wise coherence between different contrasts confirmed a positive correlation between DIR and FLAIR signal intensity and a negative correlation between DIR and both post-contrast T1-weighted image signal intensity and rCBV. Additional discrepancies between FLAIR and DIR abnormal regions were also observed, together suggesting DIR may provide additional information beyond that of FLAIR.     

Imaging in multiple sclerosis: A new spin on lesions

This article evaluates the most relevant state‐of‐the‐art magnetic resonance (MR) techniques that are clinically available to investigate multiple sclerosis (MS). The presence of hypo‐ and hyperintense lesions on T1‐ and T2‐weighted magnetic resonance imaging (MRI) sequences in white matter (WM) is a common finding that is occasionally a diagnostic challenge for the radiologist. The technical requirements and how they may help to understand, classify or follow‐up these pathologies are briefly summarized. The gold standard for MS diagnosis is pathological correlation. Yet due to limited availability of biopsy and autopsy material, there is a high demand for imaging as a diagnostic as well as prognostic indicator. With the progress in MRI during the last decade, MRI now plays a leading role in the diagnosis and follow‐up of MS. A number of correlative pathological and MR studies have helped to define pathological substrates of MS in focal lesions and normal appearing white matter (NAWM). Vascular spaces mimicking MS lesions have been minimized by the enhanced differentiation of WM and grey (GM) matter parenchyma. The aim of this article is to enhance the current understanding of histopathology and radiological characteristics of MS lesions in space and time.     

Geometric accuracy in three‐dimensional coordinates of Leksell stereotactic skull frame with wide‐bore 1.5‐T MRI compared with conventional 1.5‐T MRI

The use of 1.5‐tesla (T) magnetic resonance (MR) imaging with a wide and simultaneously short bore enhances patient comfort compared with traditional 1.5‐T MR imaging and is becoming increasingly available in stereotactic radiosurgery treatment planning. However, the geometric accuracy seems unavoidably worse in wide‐bore MR imaging than in conventional MR imaging. We assessed the geometric distortion of the stereotactic image attached on a Leksell skull frame in conventional and wide‐bore 1.5‐T MR imaging. Two kinds of acrylic phantoms were placed on the skull frame and were scanned using computed tomography (CT) and conventional and wide‐bore 1.5‐T MR imaging. The three‐dimensional coordinates on both MR imaging were compared with those on CT. Deviations of measured coordinates at selected points (x = 50, 100, 150 mm; y = 50, 100, 150 mm) were indicated on different axial planes (z = 50, 75, 100, 125, 150 mm). The differences of coordinates were less than 1.0 mm in the entire treatable area for conventional MR imaging. With the large bore system, the differences of the coordinates were less than 1.0 mm around the center but substantially exceeded 1.0 mm in the peripheral regions. Further study is needed to increase the geometric accuracy of wide‐bore MR imaging for stereotactic radiosurgery treatment planning.     

Long‐standing Morel‐Lavallée lesion in the proximal thigh: Ultrasound and MR findings with surgical and histopathological correlation

A 65‐year‐old man presented with a soft mass in his proximal right thigh. Ultrasonography showed a well‐defined anechoic lesion with slightly internal echoes. On MRI, the mass was hypointense and minimally hyperintense compared with muscle at T1 and hyperintense at T2, with a hypointense peripheral rim on both sequences. No signal loss was observed on T1‐weighted fat‐suppression MRI. The clinical setting, imaging findings and histopathological features were consistent with a long‐standing Morel‐Lavallée lesion.     

脉络膜裂囊肿的影像学诊断

背景与目的：脑部脉络膜裂囊肿属神经上皮性囊肿,临床上不常见。本文通过探讨脉络膜裂囊肿的影像学表现,以期提高对本病的诊断及鉴别诊断水平。方法：回顾性分析20例CT和MRI诊断为脉络膜裂囊肿患者的临床及影像学资料。患者均行CT和MRI检查,其中增强扫描5例。结果：20例患者均为单发病灶．其中右侧13例,左侧7例,病灶均位于两侧脉络膜裂区。CT表现为圆形或类圆形、边缘光滑的脑脊液样低密度灶、增强扫描无强化。MRI检查表现为长T1长T2脑脊液样信号灶,FLAIR为低信号,在各扫描序列中完全与脑脊液信号同步,病灶周围脑实质无明显异常表现。结论：正确认识脉络膜裂囊肿的影像学表现．可避免误诊。CT和MRI均可检出脉络膜裂囊肿,但单纯CT检出定位困难,MRI多方位扫描可作出明确诊断并能够与其他囊性病变相鉴别。     

不同容积成像技术MR增强扫描对检出脑转移瘤的价值比较

目的：探讨3D Bravo与Cube序列在脑转移瘤诊断中的价值,比较两种序列的优缺点。方法收集临床因怀疑脑转移而行3D Bravo、Cube容积采集技术MR增强扫描的病例25例。先由两位影像医师共同阅片确定转移瘤的位置与数目,以及有无脑膜转移。再由另一位影像医师对所有病例的Bravo与Cube序列图像分别进行判读,包括图像质量、转移病灶位置及数目、有无脑膜转移,比较病灶与正常灰白质的信号强度相对对比度（CR）,并对结果进行统计学分析。结果入组25例病例中共发现转移病灶221枚;Bravo序列发现转移病灶206枚（93.2%）,漏诊15枚（6.8%）,误诊1枚（0.4%）;Cube序列发现转移病灶214枚（96.8%）,漏诊7枚（3.2%）,误诊3枚（1.4%）;1例软脑膜转移病例,Cube序列诊断正确,Bravo序列出现漏诊;Bravo序列中病灶与正常灰质、病灶与正常白质的信号强度CR明显高于Cube序列（P=0.001）。结论 Bravo序列中病灶与正常灰白质的信号强度CR均明显高于Cube序列。对于近皮层的微小转移病灶以及软脑膜转移,Bravo序列有可能漏诊,Cube序列中部分病灶强化程度较低,应注意结合平扫序列综合考虑。     

Noise reduction in FLAIR2 images using total generalized variation,Gaussian and Wiener filtering

Purpose

Multiplication of FLAIR and T2-weighted MRI scans results in images (called FLAIR²) with an improved contrast-to-noise ratio (CNR) for multiple sclerosis (MS) lesions but with a reduced signal-to-noise ratio (SNR). Denoising of these images may therefore further improve FLAIR² image quality. The purpose of this work is to present a systematic investigation of FLAIR² image denoising methods using Gaussian, Wiener and Total Generalized Variation (TGV) filtering approaches.

颞叶放射性脑病磁共振成像的特征分析

背景与目的：鼻咽癌(nasopharyngeal carcinoma,NPC)放疗后放射性脑病(radiation encephalopathy,REP)的表现形式多样,对其多样性表现的报道并不多,本研究观察NPC放射性脑病的磁共振成像(magnetic resonance imaging,MRI)形态学表现特征并探讨其诊断价值。方法：对104例NPC患者共160处病灶经MRI诊断为颞叶REP的MRI资料进行回顾性分析。在NPC放射治疗8个月～13年进行MRI检查,成像序列包括T1WI,T2WI,111处病灶作了T1WI Gd—DTPA增强,37处病灶有水抑制反转恢复(fluid attented inversion recovery FLAIR)检查,其中2例有磁共振脑血流灌注成像(MR perfusion weighted imaging,MR PWI)。结果：104例REP中累及单侧颞叶48例,双侧颞叶56例,共160个病灶。脑白质病变在T2WI为高信号,信号可均匀一致,但其中59个病灶在高信号区内出现不均匀低信号影;有91个病灶同时伴有灰质病变,表现为T1WI低信号,T2WI高信号;在111个病灶T1WI Gd—DTPA检查中91个病灶出现强化灶;有5个病灶出现出血及含铁血黄素沉着。结论：鼻咽癌放射性脑病表现具有多样性,除了常见的脑白质病变外,脑灰质病变、脑出血及含铁血黄素沉着及血脑屏障破坏等均比较常见;MRI能清楚地显示这些病变。     

Distinction between postoperative recurrent glioma and delayed radiation injury using MR perfusion weighted imaging

Introduction: Distinction between postoperative recurrent glioma and radiation injury remains a tough diagnostic problem for routine imaging methods. The purpose of this study is to evaluate the differentiated effectiveness of perfusion weighted imaging (PWI) for the two entities. Methods: PWI was performed using Siemens 3.0‐T MR system for 35 patients with new contrast‐enhancing lesions at the site of treated glioma. Regions of interest (ROIs) were manually drawn at the contrast‐enhancing lesion and peri‐lesion edema areas. For calculation of standardised relative cerebral blood volume (rCBV) ratios, the same size ROIs were drawn at the area of contralateral hemisphere normal white matter on rCBV maps. At least five ROIs were selected at each lesion. The rCBV values were measured and the rCBV ratios were calculated. The maximum rCBV (rCBV_max) ratio at each region was chosen for analysis. The patients were divided into two groups: tumour recurrence and radiation injury. The mean rCBV_max ratios were compared between the two groups. Results: The mean rCBV_max ratio in the contrast‐enhancing lesion was significantly higher in the tumour recurrence (4.36 ± 1.98) compared with that (1.28 ± 0.64) in the radiation injury (P < 0.01). The mean rCBV_max ratio in the peri‐lesion edema was also significantly higher in the tumour recurrence (1.79 ± 0.51) compared with that (0.85 ± 0.28) in the radiation injury (P < 0.05). A recurrent tumour was suggested when the rCBV_max ratio >2.15 based on the receiver operating characteristic curve. Four patients with recurrent tumour and three with radiation injury were misclassified. Conclusion: PWI is a useful method to distinguish tumour recurrence and radiation injury.     

Magnetic resonance imaging signal characteristics in hydatid cysts

The MRI features of hydatid cysts were retrospectively studied in 12 patients to look for specific signal characteristics. Twelve patients in the series included eight with abdominal, two with abdominal‐pelvic, one with a sacral and one with a lung hydatid cyst. The T1‐, T2‐ and proton density (PD)‐weighted images of spin‐echo sequence were used for imaging. The signal characteristics of the hydatid parent cyst capsule and fluid, daughter cyst fluid, detached germinal membrane and surrounding soft tissue reaction were noted. Observations revealed that the capsule is best seen on T2‐ and PD‐weighted images. The daughter cysts are best demonstrated on T1‐weighted images, whereas the difference in the signal intensities of parent cyst and daughter cyst fluid is better demonstrated on T2‐weighted and T1‐weighted images, and the detached germinal membrane is best seen on T2‐ and PD‐weighted images. The signal characteristics of hydatid cyst morphology can help distinguish it from other entities.     

Atypical diffusion‐weighted magnetic resonance findings in glioblastoma multiforme

The present report describes two patients with glioblastoma multiforme with the tumour demonstrating low central apparent diffusion coefficient values similar to those found in cerebral abscesses. Although conventional MR images were fairly specific for tumour, the cases illustrate the need for exercising caution when using diffusion‐weighted (DW) MR images for the differentiation of necrotic brain tumours from abscesses. The DW MR imaging information should always be integrated with the conventional spin‐echo MR images.     

Spinal ‘flip‐flop’ effect in anorexia nervosa: A case report

Anorexia nervosa is a psychiatric eating disorder related to malnutrition and consequent altered metabolism. A 48‐year‐old female with a history of anorexia in the last 2 years referred to our hospital with spinal pain. She underwent spinal X‐ray and magnetic resonance imaging (MRI) showing multiple vertebral collapses in dorsal and lumbar spine with inversion of normal bone marrow and soft tissue signal in T1‐weighted and STIR images. We describe this case of spinal ‘flip‐flop’ phenomenon, underlining how what seems a technical failure is actually a specific imaging pattern related to the clinical context.     

肝脏局灶性病变磁共振弥散加权成像中三种呼吸采集方式的比较

目的比较3T磁共振弥散加权成像(diffusion weighted imaging,DWI)中屏气、呼吸触发、自由呼吸等3种采集技术对肝脏初诊局灶性病变的评估效能。方法 56例患者在GE公司3.0T MR磁共振机进行常规MR和3种DWI检查,其中DWI的弥散感度(b值)均为800s/mm2,扫描层数均为24,范围包括全肝。屏气方式的激励次数为1,呼吸触发为2,自由呼吸为4,其余参数保持一致。各序列最终扫描时间屏气为20s,呼吸触发2 min,自由呼吸1 min。最后由影像科2名高年资主治医师盲法记录、评价测得的数据。结果 3种DWI采集方式对所有肝脏局灶性病变的检出率(92.0%⁹5.5%)和准确率(86.8%95.5%)和准确率(86.8%⁸9.3%)差异无统计学意义(P>0.05),3组测得的正常肝脏和病变量化表观弥散系数(ADC)值具有较好的相关性(同类相关系数ICC分别为0.732和0.951),但屏气状态下测得的信噪比和对比度噪声比低于呼吸门控和自由呼吸状态(P<0.05)。结论 3种DWI采集方式对于肝脏局灶性病变的检出率和准确率差异无统计学意义(P>0.05),但非屏气序列可提供更高的信噪比和对比度噪声比,其中自由呼吸技术更具时间效率。     

Liver metastasis of a mucinous colonic carcinoma mimicking a haemangioma in T2‐weighted sequences

We report the case of a patient with a single liver metastasis of a mucinous colonic carcinoma that mimics a haemangioma in T2‐weighted sequences. Although a very high T2 signal in non‐cystic lesions is highly specific for the diagnostic of haemangioma, the use of gadolinium‐enhancement MRI is recommended. In patients with a history of neoplasia, the diagnosis of benign liver nodules should be made with caution.     

Imaging for Crohn disease: Use of 3‐T MRI in a paediatric setting

This study was carried out to review our experience with 3‐T MRI in the assessment of Crohn disease in a paediatric population. Twenty‐four patients with biopsy proven Crohn disease identified on the radiology information system underwent abdominal MRI, with or without pelvic MRI. Twenty‐eight studies were carried out on a 3‐T scanner at a tertiary paediatric hospital. Eight of 24 of these (30%) had a gastrointestinal barium study, 2 of 24 (8%) a CT and 9 of 24 (38%) an abdominal ultrasound. The different MRI sequences were rated for observation of the bowel wall and abnormalities (0–5). The findings were correlated to relevant findings on endoscopy, examination under anaesthesia (EUA) and where available surgery, barium studies, CT and ultrasound. In this study, the colon was involved in 5 of 28 (18%), small bowel in 7 of 28 (25%), terminal ileum in 5 of 28 (18%). All the perineal studies (9 of 9) showed abnormalities. Sinus tracts or fistulas were identified in 7 of 28 (25%) studies. The mean rating of the different MRI sequences in showing bowel wall and changes of Crohn disease was T2 TSE 3.6, T2 half fourier aquisition single shot turbo spin echo (HASTE) with a long TE 3.6, T2 HASTE with short TE 3.4, true fast imaging with steady state precession (FISP) 2.7, T1 4.1 and Post‐contrast T1 4.3. The T2 HASTE sequences with thinner slices improved observation. Detection of superficial abnormalities was similar on the 3D VIBE images and on the post‐contrast T1 spin‐echo (SE) sequences. In five of nine (56%) of those that had ultrasound, both studies were abnormal, with incomplete correlation of the abnormalities. Computed tomography and MRI were abnormal in two of two (100%) patients with good correlation of the abnormalities in one; in the other there was a minimal discrepancy in the estimation of the length of involved bowel. In 7 of 11 (64%) the barium study was abnormal. Good correlation to MRI findings was found in five of seven (71%) of patients. In two of seven (29%) both studies were abnormal, with incomplete correlation of the abnormalities. Barium underestimated the length of involved segment in these patients with inflammatory ileal thickening and ulceration. Notably, in both studies compression was limited because of patient discomfort and the involved segments obscured by overlap. Abdominal and pelvic MRI at 3 T is a useful imaging technique for evaluation of Crohn disease in the children. The extent of bowel wall involvement and extra‐intestinal complications, such as abscesses and fistulas can be accurately assessed non‐invasively, without the use of ionizing radiation or sedation.