Magnetic resonance imaging of injected silicone: findings in seven male-to-female transsexuals

Our goal was to describe the MR findings of subcutaneously injected silicone in male-to-female transsexuals and to determine the most optimal combination of pulse sequences for discrimination of injected silicone from the surrounding structures. Seven male-to-female transsexuals were referred for MRI in order to detect the injected silicone in the subcutaneous tissues and to visualize distant migration and possible complications. Conventional spin-echo (SE) T1-weighted and turbo SE proton-density/T2-weighted, plain short tau inversion recovery (STIR), and two STIR sequences with, respectively, water and silicone suppression were applied at 1.5 T. Three observers trained in MRI analysed the images separately for the abnormalities and rated the images using a four-level scale. The STIR with water suppression provided the highest contrast between silicone and the surrounding adipose tissue. Silicone-specific STIR pulse sequences provided clear images for the evaluation of the amount and patterns of local and distant spread of injected fluid silicone. Magnetic resonance imaging readily identifies the subcutaneously injected silicone, its distant migration and the amount of tissue disorganization around the silicone deposits. Two silicone-specific STIR sequences are usually sufficient for imaging the spread of silicone.     

MRI化学位移同、反相位成像的体外实验模型研究

目的 通过建立同、反相位的体外实验模型，探讨与同相位相比，反相位上信号强度变化与脂肪含量的相关性，并从中确定反相位上信号强度明显下降时的确切脂肪含量的标准。材料与方法模型建立方法：将1％琼脂糖水溶液与色拉油先后倒入一长方形水槽内，在水-脂交界处采用层厚10mm倾斜面进行同、反相位检查。测出同、反相位图像各部感兴趣区(ROI)的信号强度(SI)，计算信号强度下降指数(SI指数)值，并且绘制脂肪含量与SI指数关系的曲线图。结果 最初脂肪比例较低时，随脂肪含量增加，反相位的信号强度呈逐渐下降表现；而当脂肪比例较高时，其信号强度随着脂肪含量的增加而升高，其反转点的脂肪含量为23％。结论 脂肪含量在23％左右时，反相位上的信号强度有较为明显的下降，而且脂肪含量愈接近该值，信号强度下降的程度就愈明显。     

Migration of silicone oil for retinal detachment

Here we describe two, separate, and unique radiological findings in two distinct patients, sequelae from prior silicone oil injection for management of retinal detachment. In both cases we present bilateral, frontal horn hyperdense “masses” without appreciable enhancement or surrounding vasogenic edema. Both cases serve as important reminders of the potential for silicone oil migration and its unique radiological presentation, which has the potential to be a radiologic mimic of intracerebral hemorrhage and significantly change medical management of individuals presenting with transient ischemic attack or cerebrovascular accident.     

The utility of chemical shift imaging and related fat suppression as standalone technique in cryptorchidism using low field MRI

Cryptorchidism is failure of one or both testes to descend completely into the scrotum. The testis can be located anywhere along its journey of descent, between the lower pole of the kidney and the inguinal canal. Objective: The aim of this study was to assess the effectiveness of chemical shift imaging and Dixon based fat suppression using low field MRI in non-palpable undescended testicle. Patients and methods: From July 2017 through February 2018, Twenty eight boys, presented by either unilateral or bilateral cryptorchidism, with total number of forty testicles, underwent MRI study using low field machine in T1-weighted dual gradient-echo in-phase and opposed-phase sequence with Dixon based fat suppression. Results: Based on the laparoscopic/operative data, twenty one testes were located at the inguinal region, whereas fifteen testes were pelvi-abdominal and four were absent. The whole image sets of CSI and Dixon fat suppression had the highest specificity and positive predictive value (100%) and the highest overall accuracy (95%) for detection of undescended testes. Conclusion: chemical shift imaging combined with Dixon based fat suppression is reliable imaging tool as a standalone technique for evaluating cryptorchidism, providing high specificity and diagnostic accuracy.     

Wilson's disease: MRI with clinical correlation

We tried to establish possible correlations between clinical data and MRI in a group of patients with Wilson's disease. Eleven patients (6 male, 5 female), aged between 11 and 50 years old, with a duration of illness from 5 months to 32 years, were submitted to MRI on a 1.5 T System. Three patients were asymptomatic, two had mild neurological disturbances, two were moderately affected and the remaining four had a severe form of the disease. All were receiving D-penicillamine at the time of the study. In the most symptomatic patients there were abnormalities in five or more sites on MRI. The putamen was affected in all symptomatic patients, including five with dystonia. A striking feature was the peripheral location of high signal putaminal lesions on T2-weighted images. In five cases, lesions in the corpus striatum or substancia nigra explained the patient's Parkinsonian features. MRI is an efficient method for studying involvement of the central nervous system in Wilson's disease, and allows some interesting anatomoclinical correlations.     

In vivo 1H chemical shift imaging of silicone implants

In order to study the aging process (i.e., silicone migration, fat infiltration) of silicone (polydimethylsiloxane, PDMS) based biomaterials in living subjects by NMR imaging a hybrid ¹H selective excitation and saturation chemical shift imaging technique (IR/CHESS-CSSE) has been developed. This sequence allows selective mapping of the distribution of silicone protons in vivo, while suppressing the contributions of fat and water. Our results indicate that a combined inversion recovery and CHESS pulse, followed by a spoiler gradient, must be applied to suppress all contributions of fat protons to the NMR signal. The sensitivity of our experiments allows the detection of a chemically unchanged silicone concentration of 5% in a voxel of 0.9 mm³ at a signal/noise ratio of 2.     

眼眶郎格罕斯细胞组织细胞增生CT及MRI表现

目的 探讨眼眶郎格罕斯细胞组织细胞增生症影像学表现。材料与方法 回顾性分析资料完整的12例眼眶郎格罕斯细胞组织细胞增生症。均行CT扫描,其中6例行MRI检查。结果 主要临床表现为突眼。常见部位为眼眶外上壁、下壁及外壁。HRCT表现均呈溶骨性破坏,边界清楚但无硬化,伴大的软组织肿块;MRI表现T1WI均呈低信号（与脑实质比较,以下同）,T2WI呈等或高信号。CT及MRI显示病变中～重度强化。结论 HRCT可清楚显示眼眶郎格罕斯细胞组织细胞增生症的骨质改变,能帮助临床诊断。MRI可准确判断病变范围;两者结合在本病的诊断、治疗及随访中起重要作用。     

Value of contrast-enhanced MRI of breast after silicone implant

Summary Early recognition of recurrence and work-up of clinically indeterminate lesions may be impaired after reconstruction with silicone implants due to superimposition of the implant or to scarring. This study was undertaken to evaluate the use of contrast-enhanced MRI in patients with silicone implant after breast cancer. Contrast-enhanded MRI was offered to 169 patients. Comparative two- to three-view mammography was also performed in 169 patients, as well as comparative sonography in 144 patients. Conventional imaging and clinical examination detected only 8/13 recurrences, whereas 12/13 were detected by MRI. One recurrence had been visible as a strongly enhancing 2-mm dot in a previous examination (2 years before), but was not called. It was therefore counted as false negative. In addition, multicentricity was detected by MRI alone in two of three cases. MRI correctly diagnosed scar tissue in all cases with indeterminate findings. However, due to false-positive calls caused by enhancing granulomas specificity could not be improved. Contrast-enhanded MRI allowed decisive additional information in our study group and improved the sensitivity significantly (concerning all diagnoses). Contrast-enhanded MRI is recommended in patients with diagnostic problems or high risk of recurrence after silicone implants.      

Silicone-selective multishot echo-planar imaging for rapid MRI survey of breast implants

The purpose of this study was to assess the usefulness of silicone-selective multishot echo-planar imaging (EPI) for the rapid magnetic resonance imaging (MRI) survey of breast implants. Twenty patients with bilateral breast implants underwent MRI. The use of inversion recovery and magnetization transfer pulses led to silicone-selective images. The rapid MRI survey required only 43 s, which accurately distinguished between silicone and non-silicone materials in the implants, and therefore induced the final MRI sequences appropriate for the detailed characterization of the implants. In 5 of the 20 patients, the rapid MRI survey showed implanted materials that were not indicated from clinical information. This silicone-selective multishot EPI allows a rapid survey of breast implants, which is useful to avoid unnecessary sequences in these patients.     

MR imaging of silicone breast implants: Evaluation of prospective and retrospective interpretations and interobserver agreement

MR imaging was used to evaluate the integrity of silicone breast implants in 54 women with 108 implants. MR images were interpreted by relatively inexperienced readers who tried to reproduce the experiences reported in the literature. The study examines the interobserver agreement using different diagnostic signs and the influence of experience on interpretation errors. Prospective and retrospective interpretations were compared with surgical findings at the time of explantation. Diagnostic indicators, including the linguine sign, the inverted tear drop sign, the C sign, water droplets mixed with silicone, and extracapsular globules of silicone, were evaluated for diagnostic efficacy and interobserver agreement. The prospective sensitivity and specificity were 87% and 78%, respectively. With the retrospective interpretations, the sensitivity and specificity increased to 93% and 92%, respectively. Most of the prospective false-positive interpretations were due to misinterpreting radial folds as signs of implant rupture. Six implants interpreted retrospectively as false positives had gross amounts of silicone around the implants at surgery but there were no obvious rents in the implant shells. There was fair to excellent interobserver agreement with the individual diagnostic signs except for extracapsular globules of silicone. All of the signs had specificities of greater than 90%. The sensitivities of the individual signs were less than the overall retrospective sensitivity. With experience, the sensitivity improved from 87% to 93% and the specificity improved from 78% to 92%. This study helps substantiate the use of diagnostic signs used by other authors to detect silicone loss from breast implants by MR imaging; however, questions remain as to the clinical role of MR imaging in evaluating implants for silicone loss.     

POEMS syndrome: radiographic appearance with MRI correlation

POEMS syndrome is a rare disorder in which patients present with the hallmark signs of polyneuropathy, organomegaly, endocrinopathy, M protein and skin changes. Many other clinical findings are also often present, most notably osseous lesions. The MRI appearance of the bony lesions in POEMS syndrome has been described in five cases, four of which are in the non-English literature. We report the MRI appearance of the osseous lesions in a patient with POEMS syndrome who presented with sciatic neuropathy.     

Development of a tissue-equivalent MRI phantom using carrageenan gel.

A new tissue-equivalent MRI phantom based on carrageenan gel was developed. Carrageenan gel is an ideal solidifying agent for making large, strong phantoms in a wide variety of shapes. GdCl(3) was added as a T(1) modifier and agarose as a T(2) modifier. The relaxation times of a very large number of samples were estimated using 1.5-T clinical MRI equipment. The developed phantom was found to have a T(1) value of 202-1904 ms and a T(2) value of 38-423 ms when the GdCl(3) concentration was varied from 0-140 mumol/kg and the agarose concentration was varied from 0-1.6% in a carrageenan concentration that was fixed at 3%. The range of measured relaxation times covered those of all types of human tissue. Empirical formulas linking the relaxation time with the concentration of the modifier were established to enable the accurate and easy calculation of the modifier concentration needed to achieve the required relaxation times. This enables the creation of a phantom having an arbitrary combination of T(1) and T(2) values and which is capable of retaining its shape.     

Postmortem MRI of the brain with neuropathological correlation

We prospectively correlated in vitro MRI of the brain with the neuropathological findings in patients with suspected intracranial disease. In vitro MRI was performed on 91 consecutive formalinfixed whole-brain specimens. In 60 cases, the images were correlated with the neuropathological findings (number of lesions, lesion boundaries, spread of oedema and type of lesions). As compared with neuropathology, MRI showed an equal number of lesions in 50 cases, more in 5, and less in 5 specimens, resulting in a sensitivity of 83.3%. The extent of perilesional oedema was better seen on in vitro MRI than on gross pathology. Microscopic extent of glial tumours was underestimated on both T2-weighted images and macroscopic examination. Neuropathology remains the reference study, since on in vitro MRI primary brain tumours, metastatic deposits and non-neoplastic space-occupying lesions cannot be differentiated. However, in our study MRI had a specificity of 76.6%. MRI of postmortem specimens is sensitive to focal brain lesions, and can foucus the attention of the neuropathologist to abnormal regions.     

Imaging breasts with silicone implants

Over the last two decades, the use of breast implants both for breast augmentation and for breast reconstruction following mastectomy has increased substantially. It is estimated that around two million women have undergone breast augmentation, while hundreds of thousands have had breast reconstruction surgery. Different types of material have been used for breast implants, but silicone gel implants have been the dominating implant type. Many implants can lead to complications, such as hardening and rupture, and may therefore need in vivo evaluation by imaging, particularly if they lead to clinical symptoms. They can also pose problems in the assessment of surrounding breast tissue by conventional mammography. In this respect, imaging modalities such as ultrasound, computed tomography and magnetic resonance imaging offer greater possibilities to assess a failing implant, as well as surrounding breast tissue. Several factors, mainly of a psychological nature, lead to requests for breast implants. In this review article, only the imaging aspects of breasts with silicone gel implants will be dealt with. Each modality is concisely presented with its possibilities and limitations. Received: 5 February 1998; Revision received: 18 May 1998; Accepted: 25 May 1998     

MR imaging of silicone gel–filled breast implants in vivo with a method that visualizes silicone selectively

The lack of an adequately sensitive method for detecting silicone leakage and reported serious complications due to silicone leakage were cited as justification by the U.S. Food and Drug Administration for imposing the current restrictions on silicone gel–filled breast prostheses. The authors report a new magnetic resonance imaging method for visualizing silicone leakage: the silicone-only sequence (SOS). The method uses the conventional STIR (short-inversion-time inversion-recovery) technique combined with a 1331 radio-frequency pulse train widely used for water suppression in spectroscopy. With the SOS, silicone can be imaged while signals from fat and water are suppressed. The authors used the SOS to image phantoms and normal and ruptured silicone gel–filled breast prostheses.     

Metallic artifact in MRI after removal of orthopedic implants

Objective

The aim of the present study was to evaluate the metallic artifacts in MRI of the orthopedic patients after removal of metallic implants.

Subjects and methods

From March to August 2009, 40 orthopedic patients operated for removal of orthopedic metallic implants were studied by post-operative MRI from the site of removal of implants. A grading scale of 0–3 was assigned for artifact in MR images whereby 0 was considered no artifact; and I–III were considered mild, moderate, and severe metallic artifacts, respectively. These grading records were correlated with other variables including the type, size, number, and composition of metallic devices; and the site and duration of orthopedic devices stay in the body.

Results

Metallic susceptibly artifacts were detected in MRI of 18 of 40 cases (45%). Screws and pins in removed hardware were the most important factors for causing artifacts in MRI. The artifacts were found more frequently in the patients who had more screws and pins in the removed implants.Gender, age, site of implantation of the device, length of the hardware, composition of the metallic implants (stainless steel versus titanium), and duration of implantation of the hardware exerted no effect in producing metallic artifacts after removal of implants. Short TE sequences of MRI (such as T1 weighted) showed fewer artifacts.

Conclusion

Susceptibility of metallic artifacts is a frequent phenomenon in MRI of patients upon removal of metallic orthopedic implants.     

Small renal cell carcinoma: MRI with pathologic correlation

The MRI features of small renal cell carcinomas (RCCs) were retrospectively reviewed and correlated with histology in 24 patients. MRI features on both T1- and T2-weighted images were classified into hypointensity, isointensity, and hyperintensity. Each tumor was pathologically classified into four types: alveolar, papillary, tubular, and cystic. These findings were correlated with MR signal intensities. Alveolar tumors showed hypointensity to isointensity on T1-weighted image and isointensity to hyperintensity on T2-weighted image. In contrast, all papillary tumors showed hypointensity on T2-weighted image. Four of six tumors with hypointensity on T2-weighted image were caused by hemosiderin deposition, hemorrhage, and necrosis. However, there were two papillary RCCs that showed hypointensity on T2-weighted image despite no hemosiderin deposition and no hemorrhage. We conclude that papillary RCC is associated with T2-hypointense appearance as well as hemosiderin deposition, hemorrhage, and necrosis.     

肝炎后肝硬化脑波谱改变与肝脏MRI表现的相关性研究

目的：探讨肝炎后肝硬化患者脑波谱改变与肝脏MRI表现之间的关系。方法：49例肝炎后肝硬化患者均进行脑化学位移成像及肝脏MRI检查,测量脑内各代谢物的峰下面积,并以Cr为参照计算各代谢物峰下面积相对于Cr的比值。对肝脏MRI图像进行观察和测量,并评定肝脏分数,分析脑代谢物变化与肝脏MRI表现之间的关系。结果：mI及Cho的峰下面积及mI/Cr、Cho/Cr与肝脏分数呈负相关（r值分别为-0.948,-0.783,-0.942,-0.718,P＆lt;0.01）,Glx6峰下面积及Glx6/Cr与肝脏分数呈正相关（r值分别为0.763,0.886,P＆lt;0.01）。结论：肝炎后肝硬化患者脑内某些代谢物的变化与肝脏MRI改变之间关系密切。