Quantitative MRI-pathology correlations of brain white matter lesions developing in a non-human primate model of multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) induced with recombinant human myelin/oligodendrocyte glycoprotein in the common marmoset is a useful preclinical model of multiple sclerosis in which white matter lesions can be well visualized with MRI. In this study we characterized lesion progression with quantitative in vivo MRI (4.7 T; T(1) relaxation time +/- Gd-DTPA; T(2) relaxation time; magnetization transfer ratio, MTR, imaging) and correlated end stage MRI presentation with quantitative ex vivo MRI (formaldehyde fixed brains; T(1) and T(2) relaxation times; MTR) and histology. The histopathological characterization included axonal density measurements and the numeric quantification of infiltrated macrophages expressing markers for early active [luxol fast blue (LFB) or migration inhibition factor-related protein-14 positive] or late active/inactive [periodic acid Schiff (PAS) positive] demyelinating lesion. MRI experiments were done every two weeks until the monkeys were sacrificed with severe EAE-related motor deficits. Compared with the normal appearing white matter, lesions showed an initial increase in T(1) relaxation times, leakage of Gd-DTPA and decrease in MTR values. The progressive enlargement of lesions was associated with stabilized T(1) values, while T(2) initially increased and stabilized thereafter and MTR remained decreased. Gd-DTPA leakage was highly variable throughout the experiment. MRI characteristics of the cortex and (normal appearing) white matter did not change during the experiment. We observed that in vivo MTR values correlated positively with the number of early active (LFB+) and negatively with late active (PAS+) macrophages. Ex vivo MTR and relaxation times correlated positively with the number of PAS-positive macrophages. None of the investigated MRI parameters correlated with axonal density.     

Histopathological Characterization of Magnetic Resonance Imaging-Detectable Brain White Matter Lesions in a Primate Model of Multiple Sclerosis : A Correlative Study in the Experimental Autoimmune Encephalomyelitis Model in Common Marmosets (Callithrix jacchus)

Experimental autoimmune encephalomyelitis in the common marmoset, a nonhuman primate species (Callithrix jacchus), is a new model for multiple sclerosis. Given the close immunological relationship between marmosets and humans, it is an attractive model for investigating immunopathological pathways relevant to multiple sclerosis and to evaluate new treatments for the disease. Unlike in the originally documented model, experimental autoimmune encephalomyelitis induced without the use of Bordetella pertussis led to a chronic disease of moderate severity. The clinical course of experimental autoimmune encephalomyelitis in the present model was mainly chronic and progressive, but periods of incomplete remission did occur. At the chronic stage of the disease, actively demyelinating lesions were found together with inactive demyelinated and remyelinated (shadow) plaques. Before immunization and during clinically active experimental autoimmune encephalomyelitis, T1- and T2-weighted magnetic resonance brain images were obtained. Correlation of the data from the magnetic resonance images and the neuropathology analysis revealed that the hyperintense regions in T2-weighted images represented both active and inactive remyelinating lesions. Quantification showed that the number of lesions in T2-weighted magnetic resonance images equalled those found by pathological examination, and thus T2-weighted magnetic resonance imaging can be used to discern the total lesion load. Extravasation of gadolinium-diethylenetriamine-penta-acetic acid (triple dose) was found only in lesions, which by histopathology were shown to be engaged in the process of active demyelination.     

椎间隙感染的MRI诊断

目的：分析椎间隙感染的MRI影像特征，评价椎间隙感染的MRI诊断价值。方法：对15例经临床或手术病理证实的椎间隙感染患者行脊柱MRI检查，扫描序列为矢状面FrFsE-T1WI、FrFSE-T2WI、脂肪抑制T2WI，横断面FrFSE-T2WI，其中5例行Gd-DTPA增强对比扫描。结果：15例患者共发现17个椎间隙感染，其中15个发生于腰椎间隙。椎间隙狭窄(13个)，病变椎间盘呈不同程度破坏、碎裂，呈长T1(17个)长T2(15个)信号，T2上椎间盘髓核内正常裂隙状低信号消失(13个)，上下相邻椎体受累破坏(15个)，椎旁软组织肿胀(8个)。5例行Gd-DT-PA增强对比扫描可见病变椎间盘、相邻椎体及椎旁软组织异常强化。结论：MRI对诊断椎间隙感染具有很高的敏感性和准确性，应作为首选的影像学检查方法：     

原发性中枢神经系统恶性淋巴瘤MR表现及其病理学基础

目的 研究原发性中枢神经系统恶性淋巴瘤(PCNSL)的MR表现及其病理学基础。方法 分析13例手术病理证实的原发性中枢神经系统恶性淋巴瘤的临床病理及MR表现。结果 13例中单发肿瘤4例，多发肿瘤9例，共计36个病灶。13例病变均累及幕上，其中8例病灶位于深部脑白质近脑室旁。肿瘤平均最大径为3．2cm。T1WI略低信号28个，T2WI等信号24个。28个病灶呈均匀强化。肿瘤水肿及占位效应相对较轻。2例PCNSL行MR动态增强扫描，早期强化均不明显，时间-信号强度曲线呈缓慢上升型。病理上肿瘤细胞弥漫分布，瘤细胞大小较一致，细胞质少，细胞核大，染色质颗粒粗，可见瘤细胞围绕血管呈袖套样浸润，少见明显的出血及片状坏死，未见钙化，病理均为非霍奇金淋巴瘤。结论 原发性中枢神经系统恶性淋巴瘤的病理基础决定其MR增强形态、占位程度以及肿瘤发生部位具有一定特征，运用不同的MR影像学检查方法和技术，在多数情况下可以做出术前正确诊断。     

Neural fibrolipoma of the superficial peroneal nerve in the ankle: a case report with immunohistochemical analysis

This report presents a case of neural fibrolipoma arising from the superficial peroneal nerve in the ankle. A 28-year-old woman was referred with a soft tissue mass in the anterior aspect of the right ankle, which had been gradually enlarging for the past 10 years. Magnetic resonance imaging showed a mass lesion, measuring approximately 8 x 3 x 2 cm, with high to partially low signal intensity on both T1- and T2-weighted images. A band of low signal intensity within the lesion, which is indicative of coexistence with the tumor and the superficial peroneal nerve, could be detected on both T1- and T2-weighted images. The patient underwent an excisional biopsy. The specimen microscopically consisted of nerve bundles and fibro-fatty proliferation with abundant collagen fibers. Immunoreactivity for CD34 antigen antibody was detected in fibrous spindle cells. This is the first report to present an immunohistochemical profile of neural fibrolipoma. Neural fibrolipoma should be considered as a differential diagnosis when a lipomatous lesion is encountered in the foot or ankle as well as in the upper extremities.     

Low-contrast focal lesion detectability phantom for 1H MR imaging

A phantom made from tissue-mimicking materials is reported for testing 1H MRI systems regarding their ability to detect small low-contrast focal lesions and to delineate the boundaries of larger lesions. Two sets of seven spherical simulated lesions with diameters of 2, 3, 4, 5, 6.3, 7.9, and 9.5 mm have T1 and T2 values somewhat higher than the corresponding values in the surrounding simulated normal tissue. Relaxometer determinations of T1 and T2 for the simulated normal tissue yielded 955 and 106 ms, respectively, at 22 degrees C and 1 T. The corresponding values in set #1 of the simulated lesions were 1017 and 175 ms and in set #2 were 1002 and 127 ms. These T1 and T2 values are similar to those for brain and brain lesions but are too high to represent soft tissue such as liver and muscle. The centers of the 14 lesions are coplanar, and eight alignment devices surround them facilitating superposition of the scan plane and the plane containing the centers of the lesions. Illustrative images made with a 1.5-T system are shown. All simulated lesions are detectable in T2-weighted head coil images. Corresponding T1-weighted images are also shown, the 2- and 3-mm lesions of set #2 and the 2-mm lesion of set #1 not being detectable. The phantoms could be useful for performance or acceptance testing and perhaps for quality assurance testing.     

A case of intraosseous arteriovenous malformation with unusual radiological presentation of low blood flow

We report a case of intraosseous arteriovenous malformation (AVM) arising in the diaphysis of the tibia. The patient was a 15-year-old boy who presented with pain in the right lower leg for 3 years. Plain radiographs displayed honeycomb lytic lesions in the right tibial shaft, with slight expansion of the bone and cortical thinning. The lesion was isointense to the muscle on T1-weighted images, and hyperintense on T2-weighted images. An admixture of hypointense small nodular or linear areas on both T1- and T2-weighted images was present within the lesion. Post contrast fat-suppressed T1-images demonstrated a mild heterogeneous increase in signal intensity throughout the tumor. Angiographs showed only faint staining in the lesion. Curettage of the lesion was carried out, and the histological diagnosis of AVM was made. In the context of this patient's lesion, it should be noted that AVM rarely presents as an intraosseous lesion with low blood flow.     

磁共振成像、FLAIR序列及弥散加权成像技术对多发性硬化的诊断价值分析

目的比较常规磁共振成像（MRI）、液体衰减反转恢复（FLAIR）序列及弥散加权成像（DWI）检查技术对多发性硬化（MS）的诊断价值。方法58例MS患者，其中男性34例，女性24例，年龄4～70岁，平均年龄35．95岁。使用MRI进行T1加权、T2加权、FIAIR序列及弥散加权成像检查。将4种序列图像进行比较，同时使用软件进行DWI的弥散系数（ADC）及影像分析。结果①FLAIR序列共检出病灶877个，而T1WI、T2WI和DWI分别检出病灶651、776和537个，分别为FLAIR序列检出病灶数的74％、88％和61％。各成像序列对病灶的检出率之间的差异有显著统计学意义（P〈0．0001）。②MS病灶主要分布在脑室周围白质和半卵圆中心区，占总病灶数的96．1％。其中分布在脑室周围白质的病灶数与半卵圆中心区者相比，差异无统计学意义（P〉0．05），而与脑干、小脑和胼胝体相比，差异均有显著统计学意义（均P〈0．01）。③T1WI信号多为低信号、略低信号和等信号，T2WI及FLAIR序列为高信号，DWI在急性期病灶显示为略高信号影，在慢性期可表现为等信号或低信号。④MS急性期病灶平均ADC与急性脑梗死相比差异无统计学意义（P〉0．05）。亚急性和慢性期平均ADC高于脑缺血的ADC（P〈0．001），但低于脑肿瘤的ADC（P〈0．05）。结论对MS病灶的阳性检出率，FLAIR序列优于其余3个序列；DWI可以较好地区分MS病灶分期，同时应用DWI、ADC检查对判别病灶的性质、鉴别诊断有较大帮助，是诊断MS等脱髓鞘疾病的有效影像学方法。     

Intraosseous leiomyosarcoma arising in the epiphysis of the distal femur

Herein, we present a rare case of intraosseous leiomyosarcoma arising in the epiphysis of the distal femur and showing unusual radiographic features. A 44-year-old man presented with a pain in the left knee joint. Computed tomography revealed an intraosseous lesion with slightly increased attenuation and a thin marginal sclerotic rim in the femoral medial condyle. The signal of the lesion was hypointense on T1-weighted magnetic resonance (MR) images and hyperintense on fat-suppressed T2-weighted MR images. After gadolinium administration, the signal of the lesion was moderately and diffusely enhanced. The histological diagnosis of leiomyosarcoma was made based on a preoperative core biopsy specimen. Microscopic examination of the resected specimen revealed an ill-defined intraosseous tumor composed of proliferated atypical and mildly pleomorphic smooth muscle cells permeating among the bone trabeculae with only focal destruction of the bone trabeculae and low mitotic activity, indicating low grade leiomyosarcoma. The bone trabeculae at the periphery of the tumor were mildly thickened and anastomosed with a rim of an increased number of osteoblasts. Systemic examination showed no tumorous lesions in other anatomical sites. Leiomyosarcomas rarely present in the bone as a diffuse intertrabecular growth, even in low grade tumors.     

副鼻窦腺泡型横纹肌肉瘤4例CT和MRI表现

目的分析副鼻窦腺泡型横纹肌肉瘤(ARMS)的CT、MRI表现,探讨其诊断要点。方法经手术病理证实的4例ARMS患者,其中男性3例,女性1例;年龄分别为3、9、15、17岁,平均年龄11岁。所有患者均行MRI平扫及增强扫描,同时行CT平扫扫描。分析其影像特点。结果肿瘤位于蝶窦1例,筛窦2例,上颌窦1例。3例骨破坏呈膨胀性、吸收性,1例骨破坏呈溶骨性。累及翼腭窝1例,颞下窝2例,眼下直肌受累3例,鼻腔受累3例。直径5 cm呈椭圆形,直径6 cm呈不规则分叶状。2例有囊变密度或信号,无钙化,1例含有黏液蛋白成分。T1WI以稍低信号为主,近似或低于正常脑实质信号,T2WI以不均匀高信号为主,与脑脊液信号近似,增强扫描呈中等~明显强化,强化不均匀,但程度较轻,可见线环状及菊花瓣样强化。结论 ARMS的CT和MRI有一定的特征性表现,在鉴别诊断上有着较高的临床应用价值。     

3.0T超导型MRI灌注加权成像联合动态增强扫描技术在乳腺早期良恶性病变鉴定中的研究

目的探讨3.0 T超导型MRI灌注加权成像(PWI)联合动态增强扫描(DCE)在乳腺早期良恶性病变鉴定中的价值。方法选择术后经病理确诊为良恶性的乳腺早期病变女性患者61例,年龄24~65岁,平均年龄30.12岁。所有患者均经3.0 T超导型MRI PWI常规T2加权成像(T2WI)和T1加权成像(T1WI)平扫后行三维(3D)动态增强扫描技术,并根据病理结果分为恶性病变和良性病变,对比病变形态学变化、时间-信号强度曲线(TIC)及表观弥散系数(ADC)值,并分析PWI联合DCE对乳腺早期良恶性病变鉴别诊断价值。结果病理结果为恶性病变27例,良性病变34例;DCE-MRI扫描结果为恶性病变患者20例,良性病变患者26例,病变检出率75.41%;PWI扫描结果为恶性病变患者21例,良性病变患者27例,病变检出率78.69%。乳腺早期良性病变形态以类圆形(76.5%)、边缘以光滑(70.6%)为主,乳腺早期恶性病变形态以分叶形(63.0%)、边缘以毛刺征(59.3%)为主;乳腺早期良恶性病变DCE-MRI扫描形态学特征对比,差异有显著统计学意义(χ^2=43.557、37.459,P=0.000、0.000)。乳腺早期良性病变TIC形态以Ⅰ型(61.8%)为主,乳腺早期恶性病变TIC形态以Ⅲ型(77.8%)为主,两者比较,差异有显著统计学意义(χ^2=121.852,P=0.000);22例(81.5%)恶性病变患者ADC值≤1.195×10-3 mm2/s,28例(82.4%)良性病变患者ADC值>1.195×10-3 mm2/s,两者差异有显著统计学意义(χ2=26.148,P=0.000)。二者联合鉴别诊断乳腺早期良恶性病变的灵敏度、特异度及准确度与DCE-MRI、PWI单一诊断更高(P<0.05)。结论 3.0 T超导型MRI PWI联合DCE在乳腺早期良恶性病变鉴定中具有较高的临床价值。     

应用MRI技术对肝脏局灶结节性增生的诊断

目的 评估磁共振成像（magnetic resonance imaging,MRI）技术对肝脏局灶结节性增生（focal nodular hyperplasia,FNH）的诊断价值.方法 回顾性分析齐齐哈尔市第一医院2008年1月至2010年4月经手术切除或穿刺活检病理证实的10例26灶FNH 磁共振平扫、动态增强表现,由3名有经验的医师做MR表现诊断.结果 对于10例中的26个病灶,平扫T1WI上23个病灶为稍低或等信号、3个病灶为稍高信号;T2WI上23个病灶呈稍高信号、1个病灶等信号,2个病灶呈稍低信号.在动脉期5个病灶明显不均匀增强、19个病灶显著均匀增强,门静脉期和延迟期13个病灶呈稍高信号,11个病灶呈等/稍低信号,2个病灶无强化.11个病灶检出瘢痕,T1WI呈低信号,T2WI呈低或高信号,动脉期无增强、门静脉期或延迟期增强.8例诊断正确,1例诊断为良性病变（定性困难）,1例误诊为恶性肿瘤.结论 MRI能显示单发或多发FNH的特征性改变,并在术前正确诊断大部分FNH.     

Prostate cancer: added value of subtraction dynamic imaging in 3T magnetic resonance imaging with a phased-array body coil

Purpose

To determine the added value of dynamic subtraction magnetic resonance (MR) imaging for the localization of prostate cancer.

Materials and Methods

We examined 21 consecutive patients who underwent MR imaging in 3T unit with a phased-array body coil and then had radical prostatectomy. After T2-weighted fast spin-echo imaging, we performed a contrast-enhanced dynamic 3D gradient-echo imaging consisting of pre-contrast, 2 successive early-phased (first imaging was started just after the appearance of contrast material in the aortic bifurcation followed by second imaging 35 seconds after the initiation of first imaging) and one 5-minute delayed post-contrast series. Subtraction of pre-contrast images from corresponding post-contrast images of each phase was performed on the console.

Results

On ROC analysis, the overall accuracy (A_z value) of dynamic imaging combined with subtraction imaging was higher than T2-weighted imaging (p = 0.001) or conventional dynamic imaging alone (p = 0.074) for localization of cancer foci regardless of their zonal locations. Among pathologically verified 81 lesions, the mean volume of detected lesions with the subtraction images (n = 49, 0.69 cm³) was smaller than with T2-weighted images (n = 14, 1.05 cm³) or conventional dynamic images (n = 43, 0.71 cm³).

Conclusion

For localization of small prostate cancer, additional subtraction for the dynamic imaging could be superior to both T2-weighted imaging and un-subtracted dynamic imaging.     

Value of magnetic resonance imaging in predicting efficacy of GnRH analogue treatment for uterine leiomyoma

BACKGROUND: Estimating pharmacological efficacy is important when selecting conservative treatment of uterine leiomyoma. Hence, the ability of magnetic resonance (MR) imaging to predict gonadotrophin-releasing hormone (GnRH) analogue efficacy was investigated. METHODS: A total of 85 lesions was studied in 40 patients who were clinically diagnosed as having uterine leiomyoma and treated with GnRH analogue for 24 weeks. To evaluate changes in lesion size, T2-weighted and gadopentetate-dimeglumine (Gd-DTPA)-enhanced, T1-weighted MR images were obtained within 2 weeks before, and immediately after termination of, GnRH analogue treatment. RESULTS: An average 46.3% size reduction was observed in 45 lesions (52.9%); these were seen as low signal intensity on T2-weighted images and enhanced by Gd-DTPA. Also, an average 44.7% size reduction was observed in lesions enhanced by Gd-DTPA, irrespective of signal intensity findings on T2-weighted images. The average size reduction of unenhanced lesions was only 17.8%, and significantly different from enhanced lesions (P < 0.001). The prediction of efficacy was difficult in those lesions not enhanced. CONCLUSIONS: It is considered that evaluation of MR signal intensities, and the presence or absence of Gd-DTPA enhancement, would predict treatment efficacy before GnRH analogue administration.     

Computer-Aided Diagnosis for Detection of Lacunar Infarcts on MR Images: ROC Analysis of Radiologists’ Performance

The purpose of this study was to retrospectively evaluate radiologist performance in detection of lacunar infarcts on T1- and T2-weighted images, without and with the use of a computer-aided diagnosis (CAD) scheme. Thirty T1-weighted and 30 T2-weighted MR images obtained from 30 patients were used for assessing observer performance. These images were acquired using the fast spin-echo sequence with a 1.5-T MR imaging scanner. The group included 15 patients (age range, 48-83 years; mean age, 67.2 years; 10 men and five women) with a lacunar infarct and 15 patients (age range, 39-76 years; mean age, 64.0 years; eight men and seven women) without lacunar infarcts. Nine radiologists participated in the study. The radiologists initially interpreted the T1- and T2-weighted images without and then with the use of CAD, which indicated their confidence levels regarding the presence (or absence) of lacunar infarcts and the most likely position of a lesion on each MR scan. The observers' performance without and with the computer output was evaluated by performing receiver operating characteristic analysis. For the nine radiologists, the mean area under the best-fit binormal receiver operating characteristic curve plotted for unit square values of radiologists who interpreted the images without and with the scheme were 0.891 and 0.937, respectively. The performance of the radiologists improved significantly when they used the computer output (p=0.032). The CAD scheme has potential to improve the accuracy of radiologists' performance in detection of lacunar infarcts.     

Phosphate metabolism of prior eccentrically loaded vastus medialis muscle during exercise in humans

The possible alteration of metabolism of the m. vastus medialis was investigated during exercise after eccentric loading. Twelve male subjects performed stepping exercise for 25–60 min. One week before and 24 h after stepping they performed concentric leg exercise at stepwise increasing intensity, while power output was measured. During this concentric exercise and recovery therefrom, phosphorous metabolites were also measured in the m. vastus medialis with magnetic resonance spectroscopy. Creatine kinase and myoglobin in blood were measured before and 72 h after stepping. T1 and T2 ¹H-relaxation times for water were calculated from magnetic resonance images collected 72 h after stepping, and used as measures for oedema. The subjects perceived substantial soreness from 24 to 72 h after stepping. The ratio of inorganic phosphate over phosphocreatine at rest increased from 0.12± 0.02 (before) to 0.19± 0.04 (24 h after stepping) (P < 0.05). Creatine kinase activity was slightly elevated 72 h after stepping (71 [49–812] U L^-1 [median, range]; P < 0.05) compared with baseline values (58 [26–409] U L^-1), whereas myoglobin concentration was not significantly elevated (15 [8–120] μg L^-1 compared with 8 [8–41] μg L^-1). In the eccentrically exercised muscles, T1 and T2 values were not or only slightly higher than in the concentrically exercised contralateral muscles. The relation between power and the ratio of inorganic phosphate over phosphocreatine during concentric exercise, and the recovery data for inorganic phosphate, phosphocreatine and pH did not alter after stepping. These data suggest that quadriceps metabolism during concentric exercise and recovery therefrom is not affected by prior eccentric overload, but it cannot be excluded that metabolism will alter during exercise after more strenuous prior eccentric overload.     

Neuroimaging and functional analyses for multiple sclerosis

For neuroimaging studies of multiple sclerosis(MS) lesions, magnetic resonance imaging (MRI) is most useful, while evoked potentials(EPs) are commonly used for functional analyses of neural damage due to MS. This review summarizes the MRI and EP findings in MS. MS lesions are visualized as high signal intensity lesions on T2-weighted images, proton density(PD)-weighted images, and fluid-attenuated inversion recovery(FLAIR) images, while such lesions demonstrate a low signal on T1-weighted images. New MS lesions are usually enhanced by gadolinium-DTPA on T1-weighted images, and the enhancement generally lasts 4 to 8 weeks. In Asian patients with MS, opticospinal MS(Asian-type MS) shows a significantly smaller numbers of brain MRI lesions than conventional MS(Western-type MS), while opticospinal MS shows a significantly higher frequency of the spinal cord atrophy on MRI than conventional MS. EPs are useful for detecting lesions located in certain portions of the central nervous system. MRI is not sensitive enough to detect small lesions in the optic nerves and spinal cord, whereas EPs are sensitive for optic nerve and spinal cord lesions. Thus, combined use of MRI and EPs is required for the diagnosis and the optimal monitoring of disease activity in MS.     

新生儿缺氧缺血性脑病的MR诊断及临床分析

目的探讨新生儿缺氧缺血性脑病的临床与磁共振成像诊断价值。方法50例临床诊断为缺氧缺血性脑病的患儿,对其进行MR的T1WI、T2WI、DWI及FLAIR序列检查,观察皮层及皮层下白质、深部白质、基底节及丘脑、脑室及脑外间隙等部位。结果缺氧缺血性脑病患儿MRI的T1WI及FLAIR序列病灶检出率明显高于T2WI(P<0.05),DWI序列可早期发现部分病变;缺氧缺血性脑病患儿早期Apgar评分与MRI脑白质损伤影像分级有一定相关性,但非绝对相关。结论MRI对缺氧缺血性脑病的诊断有高度的敏感性,运用不同的MR序列可提高缺氧缺血性脑病患儿的检出率;缺氧缺血性脑病患儿预后须从临床与MR表现综合判断。     

快速液体衰减反转回复序列技术在脑部疾病中的应用

对76例脑部疾病患者进行快速液体衰减反转恢复序列(fluid attenuated inversion recovery，FLAIR)序列及常规快速自旋回波(fast spin echo，FSE)序列扫描，比较两种序列对病灶的显示情况。结果发现。在76例脑部疾病中，FLAIR共显示病灶172个，而B加权像(T2WI)只显示123个。FAST FLAIR显示病灶较T2WI清楚明确。在FAST FLAIR上病灶与正常脑组织的对比度更高。FLAIR技术对颅脑病变的显示优于FSE序列T2加权像，特别是对脑表面或脑室周围病灶的显示，FLAIR有很高的临床使用价值，可作为颅脑MR检查常规序列的重要补充。     

融合感知损失的深度学习在常规MR图像转换的研究

目的:研究在完全无监督的条件下深度神经网络实现常规磁共振图像间相互转换的可行性。方法:在循环生成式对抗网络(CycleGAN)中引入感知损失,使网络利用对抗损失学习图像结构信息的同时,结合循环一致性损失和感知损失生成高质量的磁共振图像,并将生成图像与CycleGAN模型以及有监督的CycleGAN模型(S_CycleGAN)生成的图像进行定量比较。结果:引入感知损失后的网络生成的图像定量评估值均高于CycleGAN模型生成的图像,生成的T1加权图像(T1WI)的定量评估值也均高于S_CycleGAN模型生成的T1WI,生成的T2加权图像(T2WI)与S_CycleGAN模型生成的T2WI的定量评估值相似。结论:在CycleGAN中引入感知损失,可以在完全无监督的条件下生成高质量的磁共振图像,进而实现高质量的常规磁共振图像的相互转换。