MR imaging of extracapsular silicone from breast implants: diagnostic pitfalls.

OBJECTIVE: We sought to identify pitfalls in recognition of extracapsular silicone on MR imaging. MATERIALS AND METHODS: Three experienced observers reviewed MR images from 359 women with current (n = 320), prior (n = 15), or both current and prior (n = 24) silicone gel implants. Axial and sagittal fast spin-echo T2-weighted images with water suppression, axial inversion-recovery T2-weighted images with water suppression, and axial T2-weighted images with silicone suppression were obtained in a dedicated phased array breast coil on a 1.5-T magnet. Images were reviewed again when only one observer saw extracapsular silicone, and reasons for disagreement were recorded. RESULTS: Rupture was identified in 265 women (77%) with current silicone implants and 378 (55%) of 687 implants. Observers agreed in describing extracapsular silicone in 85 (12%) of 687 breasts with current silicone gel implants, of which 81 (95%) showed definite evidence of rupture on MR imaging. One observer reported extracapsular silicone in another 79 breasts. Confusion over contour deformity due to weakening versus breach of the capsule accounted for 33 (42%) of 79 disagreements. Another 20 (25%) of the 79 disagreements were attributed to poor conspicuity of extracapsular silicone on fast spin-echo T2-weighted images combined with intermittent observer failure to review inversion-recovery images. Subtlety of findings (n = 17, 22%) and technical issues (n = 9, 11%) with failed water suppression of pleural effusion or cysts and ghosting artifacts accounted for remaining disagreements. CONCLUSION: Extracapsular rupture is usually manifest as local spread of silicone in the breast and is not well-depicted on fast spin-echo T2-weighted images. Water-suppressed inversion-recovery T2-weighted images are often needed to identify extracapsular silicone. Distinction of the bulge in the fibrous capsule from herniation through the capsule remains problematic.     

Silicone synovitis: MR imaging in five patients

 Silicone synovitis is a known complication of silicone implants used in orthopedic surgery for joint reconstruction. It has been studied with routine radiography; however, no report on magnetic resonance imaging abnormalities of this condition exist in the literature. This article reports on five patients with silicone synovitis studied by magnetic resonance imaging. All patients showed hypointense implants that were deformed, fragmented or subluxed, and intra- and periarticular silicone particles were evident on T1- and T2-weighted images.     

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.     

MR imaging of breast paraffinomas.

OBJECTIVE: Our objective is to present the MR appearance of breast paraffinoma, a late complication of breast augmentation by liquid paraffin wax, and to correlate this appearance with the histopathologic findings that were available for three of the 11 breasts we studied. CONCLUSION: Breast paraffinomas have a characteristic MR appearance that correlates well with histopathologic findings. With MR imaging, we were able to visualize the location and extent of the paraffinoma, best seen on the fat-suppression sequence, and to evaluate the surrounding fibroglandular breast tissue.     

High-field-strength MR imaging and metallic biomedical implants: an ex vivo evaluation of deflection forces

Ferromagnetic biomedical implants are considered a contraindication for MR imaging primarily because of the potential hazards associated with their movement or dislodgment. Many metallic biomedical implants are composed of nonferromagnetic materials and do not present a danger to patients during MR imaging. Therefore, to evaluate the ferromagnetic qualities of 36 different metallic biomedical implants (four aneurysm clips, six hemostatic clips, four dental implants, seven prosthetic heart valves, eight orthopedic prostheses, one artificial urinary sphincter, three contraceptive diaphragms, and three cerebral ventricular shunt tube connectors) not previously evaluated with a high-field-strength MR system, we measured deflection forces at the portal of the magnet of a 1.5-T MR system. Fourteen of the 36 metallic biomedical implants were determined to be ferromagnetic as indicated by their deflection in the static magnetic field. However, only the four aneurysm clips (Drake, Mayfield, McFadden, and Sundt-Kees) had sufficient ferromagnetism to warrant exclusion of patients with these implants from imaging with a 1.5-T MR system because of the possibility of movement or displacement. The calculated deflection forces for these aneurysm clips were comparable with previously reported values of certain aneurysm clips that have been designated to present a risk for patients undergoing MR imaging. Patients with 32 of 36 metallic biomedical implants tested can be safely imaged with high-field-strength MR systems.     

MR imaging in patients with metallic implants

A total of 305 magnetic resonance (MR) examinations were performed in 236 patients with metallic implants. Most examinations were performed at 0.3 T. The metallic implants included central nervous system shunting devices, tantalum mesh, surgical wire, skin staples, surgical clips, metallic orthopedic devices, and a few miscellaneous metallic objects. Patients with cardiac pacemakers, electrical implants, prosthetic cardiac valves, and aneurysm clips were excluded from MR examinations. The images were reviewed for evidence of metallic artifact. The conspicuity of artifact was related to the composition, mass, orientation, and position of the metallic object in the body. In most instances, the metallic artifact did not interfere with the interpretation of the image. The patients' records were also reviewed for adverse effects noted by each patient during the MR examination. Only two patients reported discomfort that could possibly have been related to their metallic implants, but in both cases it seemed unlikely that the symptoms were actually related to the imaging process. There were no apparent short-term adverse effects demonstrated 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.     

Gd-DTPA enhanced MR imaging of the breast in patients with postoperative scarring and silicon implants

Sixty patients with postoperative scarring with (30) or without (30) silicon implants have been examined by magnetic resonance (MR) with Gd-diethylenetriamine pentaacetic acid. The 60 patients consisted of 28 patients with obvious normal or abnormal findings and of 32 diagnostically difficult patients, who were referred to MR because of uncertain mammographic and/or clinical findings. Scarring older than 6 months postoperatively did not enhance noticeably, whereas scarring younger than 6 months postoperatively enhanced variably (nonsignificant, borderline, or significant). Since all carcinomas larger than the slice thickness enhance significantly (as also confirmed by other studies) contrast enhanced MR allowed an excellent discrimination between scarring older than 6 months and malignancy. Good visualization of the tissue around silicon implants proved to be another advantage of MR. When its use in the diagnostically difficult cases was analyzed, MR proved quite helpful in 23 of 32 cases by excluding or demonstrating malignancy.     

Inflammatory breast cancer: MR imaging findings

Purpose

This paper describes the magnetic resonance (MR) imaging features of primary inflammatory breast cancer (IBC).

Materials and methods

Two radiologists reviewed the MR examinations of 14 women with a pathological diagnosis of IBC. Images were assessed for skin thickening, oedema, nipple retraction, architectural distortion, type and extent of parenchymal and cutaneous enhancement and enhancement kinetics over time, axillary and internal mammary lymphadenopathy, pectoral muscle enhancement and additional findings.

Results

Skin thickening was identified in eight patients (58%), oedema in nine (64%), nipple retraction in two (14%), architectural distortion in eight (58%), mass-like enhancement in five (36%), non-mass-like enhancement in nine (64%) with washout enhancement curve in 12 (86%) and plateau curve in two (14%), axillary lymphadenopathy in 12 (86%) and internal mammary artery lymphadenopathy in two (14%), and pectoral muscle enhancement in one (7%). Additional findings included increased breast volume in two patients (14%), prepectoral fluid in four (28%) and hypertrophic internal mammary artery in three (21%).

Conclusions

The most characteristic MR findings of IBC are skin thickening, oedema, architectural distortion, masslike enhancement with washout curve and axillary lymphadenopathy; less frequent ones are nipple retraction, mass-like enhancement and internal mammary lymphadenopathy. Prepectoral fluid is frequent but is not a sign of infiltration.     

Renal artery stenosis: in vivo perfusion MR imaging

The intravoxel incoherent motion (IVIM) model of perfusion and diffusion imaging was applied to an in vivo canine model of unilateral renal artery stenosis and was compared with relative renal blood flow determination with radioactive microspheres. The percentage relative renal blood flow as determined with radioactive microspheres correlated closely with the percentage apparent diffusion coefficient. If this method can be adapted to human imaging, it may provide a noninvasive means for detecting renal artery stenosis.     

MR imaging of the breast

The results of clinical investigation suggest that MR imaging can provide clinically important information that cannot be obtained with conventional imaging methods, and that this modality will, in the future, be an invaluable adjunctive breast imaging tool just as breast ultrasound is today. MR imaging appears to be the most accurate method for the detection of implant failure, and although it is the most costly of the available implant imaging techniques, it may be the study of choice when there is a question of implant integrity that cannot be answered with conventional methods. MR imaging as a method to detect, diagnose, and stage breast cancer remains in the investigational stage. The specificity of MR imaging appears limited because of the overlap in the enhancement kinetics and morphologic appearance of benign and malignant lesions. In selected cases, the identification of certain morphologic features, such as internal septations or the absence of enhancement, may be used to classify a lesion as benign, offering an alternative to percutaneous or excisional biopsy. MR imaging appears to be very sensitive for the visualization of both invasive carcinoma and DCIS. Perhaps most important, MR imaging can detect invasive and noninvasive breast carcinoma that is both mammographically and clinically occult, offering the potential for more accurate breast cancer staging and optimized treatment planning. MR imaging is emerging as perhaps the most promising imaging modality for breast cancer detection to date. Published results, however, are from studies with relatively small numbers of patients. The results of these studies should be validated in a large-scale clinical trial before MR imaging is implemented clinically, outside of research settings. This type of clinical investigation is needed to define the technical requirements for optimal imaging, to define interpretation criteria, to develop accurate MR imaging guided localization and biopsy systems, to define the clinical indications for which MR imaging should be used as an adjunct to conventional imaging methods, and to address the issue of cost-effectiveness. One such trial, an international, multi-institutional study funded by the National Cancer Institute, is presently underway.