儿童颅内非典型畸胎样瘤/横纹肌样瘤的MRI表现

目的 探讨儿童中枢神经系统非典型畸胎样瘤/横纹肌样瘤的MRI表现.方法 回顾性分析经手术病理证实的12例原发性非典型畸胎样瘤/横纹肌样瘤的MRI表现.结果 幕下6例,幕上4例,颅内多发病灶2例.肿瘤体积均较大,且幕上大于幕下,最大者为8.3 cm x6.8 cm,位于大脑半球.肿瘤边界清楚,信号混杂,T1FLAIR等低信号为主者12例,T2FSE呈等信号者10例,稍高信号2例,扩散加权成像上呈混杂高信号者11例,边缘囊变9例,出血、坏死10例,增强后明显不均匀强化9例,实性部分呈环形条带样强化;不明显强化2例;轻度强化1例,脑脊液播散3例,瘤周轻度水肿6例.结论 畸胎样瘤/横纹肌样瘤以实性肿块为主,T1、T2信号混杂,均以等信号为主,扩散加权成像呈明显混杂高信号,增强扫描表现方式多样,可为明显环形强化,结节样强化,轻度强化和不强化等,出血、坏死、周围囊变常见,常出现脑脊液播散,瘤周轻度水肿.     

横纹肌样脑膜瘤的MRI表现

目的:探讨横纹肌样脑膜瘤(RM)的MRI表现,并结合文献讨论其病理特点。方法:回顾性分析我院经手术病理证实的3例RM病例。3例患者术前均行MRI平扫、增强及DWI序列检查。结果:3例RM中,2例为实性,1例为囊实性。2例实性病灶中,1例呈等T1等T2信号,DWI呈高信号,增强扫描病灶呈花环形强化;1例呈等T1稍短T2信号,DWI呈低信号,增强扫描病灶呈团块状均匀强化,矢状面可见脑膜尾征。囊实性病灶的实性部分呈等T1等T2信号,DWI呈稍高信号,增强扫描呈不均匀强化;囊性部分呈长T1长T2信号,DWI呈低信号;增强扫描未见明显强化。3例均未出现瘤周水肿。结论:横纹肌样脑膜瘤的MRI表现缺乏特征性,最终确诊需行病理学检查。     

颅内表皮样囊肿的CT、MRI及DWI诊断

目的:通过分析55例颅内表皮样囊肿CT、MRI和DWI表现,探讨表皮样囊肿的影像学诊断和鉴别诊断。方法:对55例经手术病理证实的颅内表皮样囊肿的CT、MRI及DWI表现进行回顾性分析。男33例,女22例。全部病例均行MR平扫检查,其中26例行MR增强扫描,18例行扩散加权成像,26例行CT平扫检查,5例行CT增强扫描。结果:表皮样囊肿位于脑外29例,脑实质23例,脑室3例。CT平扫24例呈低密度,2例密度稍高于脑实质。51例类似脑脊液信号,1例呈短T1短T2信号,2例呈短T1长T2信号,1例T1WI大部分呈等信号,少部分为低信号,T2WI呈低信号。2例囊壁似有轻微强化。DWI上囊肿均表现为高信号,且ADC值高于脑实质。结论:形态不规则、类似脑脊液信号、DWI呈高信号、不强化是表皮样囊肿的影像学表现特点,不典型表皮样囊肿可呈其它密度和信号变化,可根据不强化和DWI呈高信号与其它类似病变鉴别。     

颅内非典型畸胎瘤样/横纹肌样瘤的MRI特征分析

目的 探讨颅内非典型畸胎瘤样/横纹肌样瘤(AT/RT)的MRI表现特征,提高对该病的诊断及鉴别能力。方法 回顾性分析9例经病理和免疫组织化学诊断为AT/RT患者的临床及影像资料。其中男6例,女3例,年龄1～42岁。所有患者均行MR平扫及增强扫描。结果 9例AT/RT患者中6例位于幕上,3例位于幕下;肿瘤最大径为3.5～7.3 cm;其中6例肿瘤存在偏心性囊变,3例伴有瘤内出血,1例瘤内出现结节状钙化,3例显示轻度瘤周水肿;所有病灶均呈不均匀中-重度强化,4例存在边缘环形强化;8例DWI呈不均匀高信号,ADC呈低信号。结论 颅内AT/RT的MRI表现具有一定特征,结合临床资料有助于鉴别诊断。     

颅内神经节细胞胶质瘤的MRI表现

目的：探讨颅内神经节细胞胶质瘤的MRI表现。方法：回顾性分析19例经手术病理证实的颅内神经节细胞胶质瘤的临床、病理及MRI表现。结果：19例中1例表现为2个病灶,18例为单发病灶。囊实性8例和实性11例。囊实性肿瘤中囊性部分MRI平扫表现为长T1、长T2信号,增强扫描2例囊壁可见环形强化,6例囊壁无强化;实性部分MRI平扫表现为稍长T1、稍长T2异常信号影,增强扫描2例无明显强化,1例呈条纹状强化,2例呈明显不均匀强化,明显壁结节样强化3例。11例实性肿瘤中MRI平扫示1例病灶呈长T1、长T2信号改变,1例呈囊实性信号表现,此2例增强扫描示瘤内长T2信号区均有不同程度的强化;其余9例病灶表现为稍长T1、稍长T2信号,增强扫描无明显强化3例,片絮状浅淡强化4例,明显不均匀强化2例。结论：颅内神经节细胞胶质瘤的MRI表现无明显特异性,但是当MRI上表现为囊实性肿块、尤其是伴有壁结节样强化,或者实性肿块且强化及水肿均不明显,而且系以癫痫为主要症状的年轻患者时,应考虑到神经节细胞胶质瘤的可能。     

颅内表皮样囊肿的非典型CT和MRI表现

目的 探讨颅内表皮样囊肿的非典型CT和MRI表现,提高对本病的认识.方法 收集经手术病理证实的8例表皮样囊肿,术前均行MRI平扫,其中2例行扩散加权成像(difussion weighted imaging,DWI)检查,CT检查5例.MRI增强扫描4例.结果 8例表皮样囊肿发生于桥小脑角2例,大脑纵裂2例,脑实质2例,颅骨2例.CT显示囊肿表现为均匀高密度2例;混杂密度1例;囊壁及囊内钙化2例.MRI平扫2例T1WI呈均匀高信号,T2WI呈稍高、高信号;3例T1WI和T2WI呈混杂信号;3例T1WI呈不均匀低信号,T2WI呈高信号;其中1例DWI表现为高信号.4例MRI增强扫描显示囊壁显著环形强化和囊内不均匀强化2例,囊壁轻度强化2例.结论 颅内表皮样囊肿的CT和MRI非典型表现主要包括CT呈高密度、混杂密度、囊壁和囊内钙化,MRI T1 WI、T2WI呈高信号、混杂信号,增强扫描显著环形强化,在诊断时应充分结合DWI检查,以提高术前诊断准确性.     

儿童颅内非典型畸胎瘤样/横纹肌样瘤的影像表现

目的:探讨儿童颅内非典型畸胎瘤样/横纹肌样瘤(AT/RT)的影像特点。方法:回顾性分析2017年12月-2021年9月在本院经病理证实的15例AT/RT患儿的临床和影像资料。15例均行MRI平扫、DWI及对比增强扫描，10例行3D-ASL及MRS检查，10例行CT平扫。15例中，男9例、女6例；年龄0.17～1.67岁，中位年龄0.83岁。结果:15例中4例肿瘤位于幕上，7例位于幕下，跨幕上和幕下4例；肿瘤最大径2.0～10.0 cm; 15例肿瘤合并囊变14例，其中11例囊变位于外周，合并出血8例。所有病灶呈不同程度强化，其中6例呈明显环形不均匀强化；DWI上病灶呈不均匀高信号；ASL上8例呈等灌注，2例呈高灌注；MRS示肿瘤NAA降低，Cho升高。15例肿瘤中侵犯脑膜1例；伴有脑内转移2例，其中1例合并脑脊液播散。结论:颅内AT/RT的影像学表现具有一定的特征性，有助于鉴别诊断。     

磁共振扩散加权成像对于颅内表皮样囊肿的诊断价值

目的:探讨磁共振扩散加权成像(DWI)对于颅内表皮样囊肿的诊断价值。方法:回顾性分析11例经手术病理证实的颅内表皮样囊肿术前常规MRI和DWI的信号特征。结果:11例均为单发;7例表现为囊状均匀性长T1长T2信号,4例病灶信号不均匀,以长T1长T2信号为主,其内混杂少许等T1等T2信号;5例行增强扫描均未见异常强化;所有病灶在DWI上均表现为明显高信号,边界清楚,ADC图表现为中等信号。结论:DWI对于颅内表皮样囊肿的诊断及鉴别诊断具有重要价值,应作为首选检查与常规扫描同时应用。     

颅内非典型畸胎瘤样/横纹肌样瘤的影像学表现（附6例报道）

目的：探讨颅内非典型畸胎瘤样／横纹肌样瘤（AT／RT）的影像学特征。方法：回顾性分析2010年10月－2014年6月经病理和免疫组化诊断为 AT／RT 的6例患者的 CT（n＝3）和 MRI（n＝6）表现,并进行相关文献复习。结果：6名患者平均年龄2．05岁。肿瘤位于幕上4例,幕下1例,幕上及幕下多发病灶1例。肿瘤最大径30～96 mm,平均（59±24）mm。囊变6例,出血4例,钙化2例,所有病灶都有中重度强化。病灶扩散加权成像（DWI）呈不均匀高信号,表观扩散系数（ADC）值（0．70±0．12）×10－3 mm2／s 。1例病灶侵犯邻近硬膜及颅骨;1例病灶发生柔脑膜种植。2例患者术后随访 MRI 时病灶复发。结论：虽然颅内 AT／RT 无特异性影像学表现,但当肿瘤较大、伴有囊变及出血、低 ADC 值及脑脊液播散时,不应排除 AT／RT 的诊断。     

颅内神经节细胞胶质瘤的MRI诊断

目的探讨颅内神经节细胞胶质瘤的MRI表现及鉴别诊断。方法回顾性分析经病理证实的24例颅内神经节细胞胶质瘤的MRI表现,患者均行MRI平扫及增强扫描。结果24例颅内神经节细胞胶质瘤中,单发23例,多发1例;幕上21例,累及额颞叶为主;幕下3例,累及小脑半球及脑干。病灶大小约2～10cm不等。不规则形12例、类圆形6例、脑回状6例。囊实性14例、实性7例、囊性3例,瘤周多无或轻度水肿,边界清晰,与脑实质分界清晰。平扫肿瘤囊性部分T,wI、TzFLAIR低信号,T2wI高信号,实性部分TzwI稍低信号,T2wI及TzFLAIR高或稍高信号;增强扫描肿瘤强化模式多样,可呈轻中度或明显均匀或不均匀强化。结论颅内神经节细胞胶质瘤MRI表现多样,但具有一定特异性,单发多见,好发于幕上,以额颞叶最为常见,囊实性多见,瘤周水肿程度轻,确诊还有赖病理及免疫组织化学证实。     

MR imaging in the diagnosis of desmoplastic infantile tumor: retrospective study of six cases

BACKGROUND AND PURPOSE: Desmoplastic infantile tumors (DITs) are rare supratentorial tumors of infancy with a favorable prognosis. Radiologic and histologic features of DIT are misleading, and DIT may be misinterpreted as a malignant lesion. We have studied the usefulness of MR imaging in the diagnosis of these tumors. METHODS: Between 1995 and 2002, six DITs were diagnosed in young children at our institution. Neuroimaging, age at diagnosis, sex, clinical presentation, symptoms duration, follow-up, and development were studied retrospectively. Contrast-enhanced CT and MR images were available. MR study included T1-, T2-, and postgadolinium T1-weighted sequences in the axial, sagittal, and coronal planes. RESULTS: These tumors were massive and predominantly cystic, with preferential frontal and parietal involvement. Typically, a DIT appears as a hypointense cystic mass with an isointense peripheral solid component on T1-weighted MR images. The peripheral solid component enhances after gadolinium administration. On T2-weighted MR images, the cystic component is hyperintense and the solid portion isointense or heterogeneous. The cystic portion is usually located deep inside the lesion, whereas its solid portion is peripheral. Meningeal enhancement and thickening adjacent to the solid portion of the tumor, calcifications, bone abnormalities adjacent to the tumor consisting of thinning and deformation were noted in 50% of our cases. Edema was usually absent or moderate. Median follow-up was 32 months, and no recurrence was noted except for one atypical case with incomplete excision, which led to the patient's death. CONCLUSION: Despite their malignant appearance, MR imaging features of DIT may help in the diagnosis and obviate unnecessary chemotherapy or radiation therapy.     

Primary intracranial atypical teratoid/rhabdoid tumors of infancy and childhood: MRI features and patient outcomes

BACKGROUND AND PURPOSE: Primary atypical teratoid/rhabdoid tumors (AT/RTs) are rare malignant intracranial neoplasms, usually occurring in young children. The objectives of this study were to characterize the MR imaging features and locations of primary intracranial AT/RTs, to determine the frequency of disseminated disease in the central nervous system (CNS) at diagnosis and postoperatively, and to assess patient outcomes. METHODS: The preoperative cranial MR images of 13 patients with AT/RTs were retrospectively reviewed for evaluation of lesion location, size, MR signal intensity and enhancement characteristics, and the presence of disseminated intracranial tumor. Postoperative MR images of the head and spine for 17 patients were reviewed for the presence of locally recurrent or residual tumor and disseminated neoplasm. Imaging data were correlated with patient outcomes. RESULTS: Patients ranged in age from 4 months to 15 years (median age, 2.9 years). Primary AT/RTs were intra-axial in 94% of patients. The single primary extra-axial lesion was located in the cerebellopontine angle cistern. AT/RTs were infratentorial in 47%, supratentorial in 41%, and both infra- and supratentorial in 12%. A germ-line mutation of the hSNF5/INI1 tumor-suppressor gene was responsible for the simultaneous occurrence of an intracranial AT/RT and a malignant renal rhabdoid tumor in a 4-month-old patient. Mean tumor sizes were 3.6 x 3.8 x 3.9 cm. On short TR images, AT/RTs typically had heterogeneous intermediate signal intensity, as well as zones of low (54%), high (8%), or both low and high (31%) signal intensity from cystic and/or necrotic regions, hemorrhage, or both, respectively. On long TR/long TE images, solid portions of AT/RTs typically had heterogeneous intermediate-to-slightly-high signal intensity with additional zones of high (54%) or both high and low signal intensity (38%), secondary to cystic and/or necrotic regions, edema, prior hemorrhage, and/or calcifications. AT/RT had isointense and/or slightly hyperintense signal intensity relative to gray matter on fluid-attenuated inversion-recovery (FLAIR) and long TR/long TE images, and showed restricted diffusion. All except 1 AT/RT showed contrast enhancement. The fraction of tumor volume showing enhancement was greater than two thirds in 58%, between one third and two thirds in 33%, and less than one third in 9%. Disseminated tumor in the leptomeninges was seen with MR imaging in 24% of patients at diagnosis/initial staging and occurred in another 35% from 4 months to 2.8 years (mean, 1.1 years) after surgery and earlier imaging examinations with negative findings. The overall 1-year and 5-year survival probabilities were 71% and 28%, respectively. Patients with MR imaging evidence of disseminated leptomeningeal tumor had a median survival rate of 16 months compared with 149 months for those without disseminated tumor (P < .004, logrank test). CONCLUSION: AT/RTs are typically intra-axial lesions, which can be infra- and/or supratentorial. The unenhanced and enhanced MR imaging features of AT/RT are often variable secondary to cystic/necrotic changes, hemorrhage, and/or calcifications. Poor prognosis is associated with MR imaging evidence of disseminated leptomeningeal tumor.     

MR imaging of the normal and abnormal clivus

We retrospectively reviewed 330 T1-weighted sagittal images, 80 T2-weighted sagittal images, and 83 gadopentetate-dimeglumine-enhanced scans of normal adults to determine the MR appearance of the normal adult clivus. MR images of 21 patients with an abnormal clivus (19 with tumor invasion and two with marrow reconversion) were also evaluated restrospectively and compared with those of the control group to assess MR features distinguishing the two groups. Our study revealed that a normal adult clivus consisted of low- and high-intensity portions mixed in various proportions on T1-weighted images. The low-intensity portion was isointense or hyperintense relative to the pons and always contained foci of bright signal intensity. The low-intensity tumor of a pathologic clivus tended to be hypointense relative to the pons (17/19), and was completely devoid of foci of bright signal intensity. The normal adult clivus was approximately isointense relative to the pons on T2-weighted images. Clival tumors were grossly hyperintense relative to the pons on T2-weighted images in 11 of 17 patients. In the remaining six patients, either a portion of or the entire lesion was isointense relative to the pons and, therefore, was not detectable on T2-weighted images. A normal adult clivus can enhance to some degree (19/83). Clival tumors were found to enhance intensely. A clivus of very low signal intensity (signal void) on T1- or T2-weighted images was always abnormal. The clivus with marrow reconversion was uniformly hypointense relative to the pons on T1-weighted images and isointense relative to normal marrow on T2-weighted images.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neurenteric cyst in the cerebellopontine angle with xanthogranulomatous changes: serial MR findings with pathologic correlation

We report serial MR findings in a middle-aged woman with a neurenteric cyst involving the cerebellopontine angle cistern with xanthogranulomatous changes. On the initial gadolinium-enhanced T1-weighted MR images, the solid portion of the lesion had homogeneously strong enhancement. Follow-up MR images obtained 6 months later showed that the mass had increased in size; however, the solid portion decreased in size. The enhancing solid portion corresponded to the xanthogranulomatous changes on pathologic correlation.     

Atypical teratoid/rhabdoid tumors in adult patients: CT and MR imaging features

Primary AT/RT is a rare highly malignant tumor of the CNS, usually occurring in children younger than 5 years of age. The objective of this study was to characterize the CT and MR imaging findings in a series of 5 adult patients with pathologically proved AT/RT. All 5 AT/RTs were supratentorial. In 2 patients who underwent nonenhanced CT, the tumors appeared isoattenuated, and 1 of the 2 tumors contained calcifications. Solid portions of the tumors on MR imaging were isointense on T1-weighted, T2-weighted, and FLAIR images, and 1 case showed restricted diffusion on DWI. The tumors also demonstrated a bandlike rim of strong enhancement surrounding a central cystic area on contrast-enhanced T1-weighted imaging. One tumor was associated with destruction of the calvaria. Although AT/RTs can have nonspecific findings, the tumors in our series were large and isointense on T1-weighted, T2-weighted, and FLAIR images with central necrosis and prominent rim enhancement.     

MR signal of the solid portion of pilocytic astrocytoma on T2-weighted images:is it useful for differentiation from medulloblastoma?

Background and purpose: Although imaging features of cerebellar pilocytic astrocytoma and medulloblastoma have been described in many texts, original comparisons of magnetic resonance intensity between these two tumours are limited. In the present study the results of magnetic resonance imaging (MRI) were reviewed, focusing especially on the signal intensity of the solid portion of these neoplasms. Methods: MR images of ten cerebellar pilocytic astrocytomas and ten medulloblastomas were reviewed. The signal intensities of the solid components were graded on a scale of 1 to 5, with higher scores indicating a signal intensity closer to that of water. The degree of enhancement, tumour cysts and peripheral oedema were evaluated on MR images. When the solid portion was heterogeneous (i.e. mixed signal intensity or degree of enhancement), the dominant area was selected for evaluation. Results: On T2-weighted images, the signal intensity of the solid portion was equal to that of cerebrospinal fluid (CSF) in 50% of pilocytic astrocytomas. No medulloblastomas showed such hyperintensity. Most medulloblastomas (80%) were isointense to grey matter. On T1-weighted images, the signal intensity varied widely in pilocytic astrocytomas; however, all medulloblastomas were iso- or hypointense to grey matter. The MR enhancement pattern, cystic component and peripheral oedema all varied in both tumour types and no specific features were identified. Conclusion: A signal intensity of the solid portion isointense to CSF on T2-weighted images was characteristic of cerebellar pilocytic astrocytomas; this was not observed in medulloblastomas. Attention to T2-weighted imaging of the solid portions of a tumour is easy and helpful in differentiating between cerebellar pilocytic astrocytoma and medulloblastoma.     

39例腹壁子宫内膜异位症的MRI表现

目的:探讨腹壁子宫内膜异位症的MRI征象及临床特点,探讨MRI的诊断价值.方法:本院39例经病理组织学证实的腹壁子宫内膜异位症患者,经盆腔MRI平扫及增强扫描,回顾性分析其影像表现及临床病理资料.结果:39例腹壁子宫内膜异位症中,大多数患者有剖宫产手术史,仅1例无腹部手术史.34例(87.2％)病灶边界模糊.22例(56.4％)病灶呈实性,T1WI呈等信号,T2WI呈混杂信号为主;15例(38.5％)病灶呈囊实性,T2WI呈高低混杂信号,T1WI以等低信号为主,其中抑脂T1WI中有高信号灶为7例;2例(5.1％)病灶呈囊性,T2WI及T1WI均呈高信号.囊性病灶增强扫描后强化不明显;实性及囊实性病灶增强扫描后病灶均可见持续性强化,病灶显示更加清晰.结论:结合临床病史及MRI表现特点,能准确诊断腹壁子宫内膜异位症,MRI能准确显示病灶位置、边界、大小及范围,对于临床治疗方案的制定有很大参考价值.     

MR imaging features of solid pseudopapillary tumor of the pancreas in adult and pediatric patients

OBJECTIVE: This study was conducted to describe the MR imaging features of solid pseudopapillary tumor of the pancreas. CONCLUSION: Solid pseudopapillary tumor of the pancreas, a tumor typically seen in young women, is a large, well-defined, encapsulated lesion with heterogeneous high or low signal intensity on T1-weighted, heterogeneous high signal intensity on T2-weighted, and early peripheral heterogeneous enhancement with progressive fill-in on gadolinium-enhanced dynamic MR imaging. These features help differentiate this rare tumor from other pancreatic neoplasms.     

Infantile fibromatosis in childhood: findings on MR imaging and pathologic correlation

AIM: The objective of this study was to analyse the MR imaging findings of infantile fibromatosis of childhood and to correlate them with histopathological features. MATERIALS AND METHODS: Seven patients with histologically proven infantile fibromatosis were included in this study. The findings on MR images were retrospectively evaluated and then correlated with the pathological features. Findings on MR imaging evaluated included signal intensity, extent of hyperintense area on T2-weighted images, margins of the lesion, the degree and pattern of enhancement and the presence of fatty tissue. Pathological features evaluated included cellularity, collagenization, and myxoid change. A five point scale was used for the evaluation of the extent of hyperintense area on MR imaging, and each of pathological features. RESULTS: On T1-weighted images, the lesions were iso-intense in two patients; iso- and hypointense in three; and iso-, hypo- and hyperintense in two. On T2-weighted images, iso-, hypo- and hyperintense areas were mixed in all patients, the hyperintense area being the largest portion of the lesion. The margins of the lesions were infiltrative in four patients (57%), smooth in two (29%) and mixed in one (14%). Enhancement was marked in five patients (72%) and diffuse in five (71%). Regardless of the hyperintense signal intensity on T2-weighted images, the grades of each pathologic feature were variable. CONCLUSION: Infantile fibromatosis on MR imaging causes an enhancing mass, that is largely hyperintense on T2-weighted images. Areas of high signal intensity on T2-weighted images corresponded to variable grades of cellularity, collagenization, or myxoid change.     

CT and MR imaging features of oral and maxillofacial hemangioma and vascular malformation

PURPOSE: To present CT and MR images and compare CT and MRI features of oral and maxillofacial hemangioma and vascular malformation. MATERIAL AND METHODS: The clinical materials consisted of nine vascular tumors from nine patients examined by both CT and MR scanners between November 1996 and March 2002. Both CT and MR images were retrospectively evaluated. The following features were evaluated: detectability of the lesion, border of the lesion, tumor margin, inner nature of the lesion, contrast between the lesion and surrounding tissues, degree of CT value or signal intensity of the lesion, enhancement of contrast medium, inner nature of the lesion after contrast medium injection, detectability of phleboliths and detectability of bone resorption. RESULTS: In two patients, we could not detect lesions in any of the CT images because of artifacts from the teeth and/or dental restorations. In contrast, we could detect all lesions on T2-weighted MR images and contrast enhanced T1-weighted MR images. On T2-weighted images with the fat suppression technique, tumors tended to show higher contrast compared to surrounding tissues. CONCLUSION: T2-weighted images with the fat suppression technique and contrast enhanced T1-weighted images with the fat suppression technique were very useful for the detection of vascular lesions. Observation from optional directions (axial, coronal and sagittal images) seemed appropriate for delineating the extension of the tumor. Phleboliths detectability on CT images was superior to that on MR images.