Prototype breast coil for MR-guided needle localization

MRI-guided needle localization: Indications, tips, tricks, and review of the literature

We describe the history of, indications for, and techniques involved in MRI-guided needle localization (MRI-NL). MRI-NL continues to be a safe, effective method of sampling lesions that are only detected with MRI, particularly for anatomically challenging lesions such as those near the chest wall, the nipple, the skin, and/or in close proximity to implants.

MRI vacuum-assisted breast biopsies

The indications, technique, results and limitations of MRI vacuum-assisted breast biopsies are discussed from a review of the literature. This was initially a home-grown technique and its development was slowed down by several factors. As a result of major technical advances, it has become a reliable and very consistent procedure with a low rate of underestimation. It is now an undisputed technique when suspicious MRI enhancement is seen with no corresponding mammography or ultrasound features.

Significance of breast lesion descriptors in the ACR BI-RADS MRI lexicon

In recent years, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has altered the clinical management for women with breast cancer. In March 2007, the American Cancer Society (ACS) issued a new guideline recommending annual MRI screening for high-risk women. This guideline is expected to substantially increase the number of women each year who receive breast MRI. The diagnosis of breast MRI involves the description of morphological and enhancement kinetics features. To standardize the communication language, the Breast Imaging Reporting and Data System (BI-RADS) MRI lexicon was developed by the American College of Radiology (ACR). In this article, the authors will review various appearances of breast lesions on MRI by using the standardized terms of the ACR BI-RADS MRI lexicon. The purpose is to familiarize all medical professionals with the breast MRI lexicon because the use of this imaging modality is rapidly growing in the field of breast disease. By using this common language, a comprehensive analysis of both morphological and kinetic features used in image interpretation will help radiologists and other clinicians to communicate more clearly and consistently. This may, in turn, help physicians and patients to jointly select an appropriate management protocol for each patient's clinical situation.

Magnetic resonance imaging--guided breast interventions

The use of breast magnetic resonance imaging (MRI) for screening, diagnosis, staging, and management of breast cancer is rapidly increasing. MRI is highly sensitive for the detection of benign and malignant abnormalities that are occult to physical examination, ultrasound, and mammography. However, the specificity of MRI is moderate. These attributes necessitate methods for MR-guided tissue sampling to determine the histology of MRI detected lesions. This article will review appropriate peer-reviewed data and currently accepted methods for MR-guided tissue sampling. A detailed step-by-step technique for vacuum-assisted MR-guided breast biopsy is included. We also review emerging data for percutaneous and transcutaneous MR-guided breast interventions such as tissue ablation for benign and malignant disease.

The current status of breast MR imaging. Part I. Choice of technique, image interpretation, diagnostic accuracy, and transfer to clinical practice

Compared with mammography and breast ultrasonography, contrast material-enhanced magnetic resonance (MR) imaging is a breast imaging technique that offers not only information on lesion cross-sectional morphology but also on functional lesion features such as tissue perfusion and enhancement kinetics. After an enthusiastic start to clinical breast MR imaging in the early 1990s, a variety of difficulties and obstacles were identified that hampered the transfer of the modality into clinical practice, including a lack of standardization regarding image acquisition and interpretation guidelines, a lack of MR-compatible interventional materials, and a lack of evidence regarding its diagnostic accuracy--particularly specificity and positive predictive value, as well as sensitivity for ductal carcinoma in situ. This article is the first of two on the current status of breast MR imaging. The pathophysiologic basis of breast MR and the effects on acquisition technique and diagnostic accuracy, the diverging demands of high spatial and temporal resolution, and the different approaches that exist for image acquisition are reviewed. Advantages and disadvantages of different pulse sequence parameters are discussed to help radiologists make a balanced and informed decision regarding choice of image acquisition protocol. Imaging findings in common benign and malignant changes are described, and current concepts for differential diagnosis, including the MR Breast Imaging Reporting and Data System lexicon, are discussed. Furthermore, obstacles that impeded the technique's transfer into clinical practice are discussed, and the progress made in recent years, especially regarding the development of guidelines, procedural standardization, and MR-guided interventions are outlined.

Computer assistance for MR based diagnosis of breast cancer: present and future challenges

MR based methods have gained an important role for the clinical detection and diagnosis of breast cancer. Dynamic contrast-enhanced MRI of the breast has become a robust and successful method, especially for diagnosis of high-risk cases due to its higher sensitivity compared to X-ray mammography. The application of MR based imaging methods depends on various automated image processing routines. The combination of techniques for preprocessing, quantification and visualization of datasets is necessary to achieve fast and solid assessment of valuable parameters for diagnosis. In this paper, different aspects such as registration methods for the reduction of motion artifacts, segmentation issues, as well as morphologic and dynamic lesion analysis will be reviewed with a focus on breast MRI, MR spectroscopy and MR guided biopsies of the breast, their implications and technical challenges from a computer assistance point of view.

MRI-Guided percutaneous biopsy of breast lesions: materials, techniques, success rates, and management in patients with suspected radiologic-pathologic mismatch

MR imaging of the breast allows the detection of suspicious breast lesions that are occult at mammography and ultrasound. For the histologic verification of such lesions, percutaneous MR imaging-guided biopsy techniques can now be offered as an alternative to open breast biopsy. This review focuses on the currently available devices and techniques for MR imaging-guided percutaneous breast biopsy and reports their achievable diagnostic accuracy. Technical success rates and strategies for patient management are also outlined. In addition, new developments in MR imaging-guided minimally invasive therapeutic interventions are discussed, as well as the potential for research opportunities and directions.

MR-guided breast biopsy and hook wire marking using a low-field (0.23 T) scanner with optical instrument tracking

The purpose of this study was to evaluate the technical feasibility of MR-guided percutaneous breast biopsy (LCNB) and breast hook wire marking in a low-field (0.23 T) MRI system with optical instrument tracking. MR-guided core biopsy and/or hook wire marking was performed on 13 lesions observable at MR imaging only. Seven breast LCNBs and 10 hook wire markings were performed under MR guidance on 11 patients. The diagnosis was confirmed by excision biopsy or mastectomy in 12 lesions and with histopathological and cytological diagnosis and 12-month clinical follow-up in one lesion. All lesions seen in the high-field scanner were also successfully identified and targeted in the low-field scanner. The following procedures were typically technically successful. There were difficulties due to unsatisfactory functioning of some core biopsy guns. Detailed description of low-field MR guidance and optical tracking in breast biopsies is provided. The procedure seems accurate and safe and provides means to obtain a histological diagnosis of a breast lesion only seen with MRI. The low-field biopsy system is comparable to the high-field MRI system. MR-compatible biopsy guns need to be improved.

MR Imaging–guided Breast Localization System with Medial or Lateral Access

PURPOSE

To evaluate the degree of error of the authors' magnetic resonance (MR) imaging-guided needle localization system for biopsy of suspicious lesions visualized only with MR imaging, by using both prospectively recorded and retrospectively reviewed data, including MR imaging lesion coordinates as the reference standard, and to determine whether any lesion or breast characteristics affect this error.

MATERIALS AND METHODS

Institutional review board approval, along with informed consent, was obtained as directed by the board. In 31 patients (age range, 34-64 years; mean age, 54.5 years), 38 wires were placed for 35 lesions by means of an MR-guided needle localization system with medial or lateral access and computer software assistance for needle placement calculation. Needle and wire placement error measurements were calculated before and after necessary placement correction, accounting for tissue shift in the z plane. The error was statistically correlated with MR imaging lesion variables, breast density, and histopathologic findings by means of univariate and multivariate linear regression analyses or two-tailed paired t test. Procedure times and the frequency of medial or lateral approaches were recorded.

RESULTS

Eleven of 35 localizations (31%) were medial, and 24 of 35 (69%) were lateral. The mean total magnet time was 61.6 minutes, and the mean needle deployment time was 9 minutes (range, 4-17 minutes). Sixteen of 35 lesions (46%) were malignant (seven ductal carcinoma in situ, six invasive ductal, two invasive lobular, and one lymphoma). The mean uncorrected needle placement error was 1.3 mm (range, 0-6 mm) for the x plane, 2.4 mm (range, 0-6.5 mm) for the y plane, and 5.6 mm (range, 0-15.6 mm) for the z plane. Fourteen of 38 needles (37%) required repositioning for z-plane error. The corrected z-plane error improved to 3.2 mm (range, 0-10.0 mm). Factors that significantly increased the uncorrected error included tissue shift in the z plane (R = 0.7), small lesion size (R = -0.59), and fatty breast density (P = .029).

CONCLUSION

The authors' system is accurate for performing MR-guided needle localizations for both medial and lateral approaches. Factors that increased the uncorrected needle placement error included small lesion size, fatty breast density, and tissue shift in the z plane.

MRI-Guided Breast Interventions

The use of breast magnetic resonance imaging (MRI) in the diagnosis, staging, and management of breast cancer is rapidly increasing. MRI has the ability to detect malignancy that is occult to physical exam, ultrasound, and mammography. These qualities necessitate methods for MRI-guided tissue sampling. This article reviews all previously published and currently accepted methods for MRI-guided tissue sampling. The data to support these techniques are provided where appropriate. A detailed technique for vacuum-assisted breast biopsy is included. We will also review the data on other MRI-guided breast interventions such as transcutaneous tissue ablation.

Magnetic resonance-guided, vacuum-assisted breast biopsy: results from a European multicenter study of 538 lesions

BACKGROUND

The objective of this study was to determine the accuracy, reproducibility, and clinical value of magnetic resonance (MR)-guided, vacuum-assisted breast biopsy (MR-VAB) in a prospective, multicenter study.

METHODS

In 5 European centers, MR-VAB was performed or attempted on 538 suspicious lesions that were visible or could targeted only by MR imaging (MRI). Verification of malignant or borderline lesions included reexcision of the biopsy cavity. Benign biopsy results were verified by retrospective correlation of histology with preinterventional and postinterventional MRI studies. Follow-up of 24-48 months (median, 32 months) was available for 491 of 538 patients.

RESULTS

MR-VAB was unsuccessful or was not completed in 21 of 538 patients, for which an immediate repeat biopsy was recommended. Five hundred seventeen of 538 performed VAB procedures (96%) were successful. Histology yielded 138 (27%) malignancies, 17 (3%) atypical ductal hyperplasias, and 362 (70%) benign entities. No false-negative diagnoses occurred among the 517 successful MR-VAB procedures. The positive predictive value of VAB depended on patient preselection, which differed according to the indication for the initial MRI study.

CONCLUSIONS

The results of this study indicated that MR-VAB offers excellent accuracy. Small lesion size did not prove to be a limitation.

MR-Guided Interventions of the Breast

Techniques and instrumentation are now widely available that enable interventional MR-guided preoperative needle localization and lesion marking. Minimally invasive MR-guided core biopsy techniques have been demonstrated but remain limited for small lesions and will be facilitated by the development of biopsy instruments that can be directly visualized using MR imaging. MR-guided tumor ablation is beginning to be evaluated in a few centers. It holds promise as new treatment modality in the continuing trend toward greater breast conservation in the local therapy of breast cancer. Further studies are needed to document the ability of MR-guided ablation to control the margins of a tumor as effectively as surgery. Patients with an extensive in situ intra-ductal component may pose a significant hurdle because the extent of ductal carcinoma in situ maybe underestimated on breast MR images. Ultimately, the success of MR-guided thermal ablation depends on the ability of MR imaging to map the extent of heating during the procedure so that the procedure can be performed to achieve complete control of the tumor margins. It is unfortunate that the conventional method for MR thermometry--the proton resonance frequency shift method--does not work in fat or in voxels with a mix of fat and glandular tissue and, hence, has limited applicability in the breast. Other methods, including measurement of T1 and T2, are being investigated as alternatives.

Percutaneous Biopsy from Blinded to MR Guided: An Update on Current Techniques and Applications

The advent of interventional MR imaging techniques as well as their adoption to guide percutaneous biopsies and aspirations has served as a further step along a series of technical refinements that commenced with the implementation of image-guided approaches for tissue sampling. Nowadays, the practice of and the expectations from these procedures are quite different from those of the blind percutaneous thrusts performed in the late nineteenth and early twentieth centuries. As the field of interventional MR imaging continues to flourish and to attract more radiologists who realize the many opportunities that this technology can offer to their patients, there is a need for a full comprehension of the concepts, techniques, limitations, and cost-effectiveness of MR imaging guidance to present this service to clinical partners in the appropriate setting. Radiologists should also recognize the need for their significant involvement in the technical aspects of MR-guided procedures, because several user-defined parameters and trajectory decisions can alter device visualization in the MR imaging environment and hence affect procedure safety.

Preoperative Magnetic Resonance Imaging-Guided Localization of 131 Breast Lesions With Modified Embolization Coils

OBJECTIVES

The objectives of this study were to assess practicability, outcome, and possible advantages of magnetic resonance imaging (MRI)-guided localizations with modified embolization coils for exclusively MRI-detected suspicious breast lesions.

MATERIALS AND METHODS

We performed 131 MRI-guided preoperative localizations in 105 patients with exclusively MRI-detected breast lesions. Contrast-enhanced, T1-weighted, 3-dimensional gradient echo sequences were used for imaging. Breast fixation and needle guidance were achieved by a perforated plate. Lesion localization was performed with a modified embolization coil. The distance between coil and lesion was measured. Results of specimen radiography and histopathology were analyzed.

RESULTS

Thirty-four of 131 lesions (26%) were malignant. Lesion localization and excision was successful in all patients. The mean distance between the coil and the lesion was 0.5 mm (+/-1.7 mm standard deviation).

CONCLUSIONS

Exact MRI-guided preoperative localization of exclusively MRI-detected breast lesions by using a modified embolization coil is feasible with excellent precision. Advantages over wire localization procedures are the possibility of specimen x-ray and the independence from time and place of operation.

Detection and localization of occult lesions using breast magnetic resonance imaging: initial experience in a community hospital

RATIONALE AND OBJECTIVES

To evaluate the outcome of diagnostic breast MR imaging followed by MR guided needle localization for mammographically and sonographically occult breast lesions in a community-based hospital.

MATERIALS AND METHODS

Records of the initial 50 consecutive patients who underwent MR guided needle localizations at our institution from November 2001 to January 2003 were reviewed. Sixty-two lesions were localized by MR and were mammographically and sonographically occult. Pathology following excision was reviewed and correlated with the MR findings.

RESULTS

Cancer was present in 15 % (9/62) of lesions or 18 % (9/50) of the women localized. Five of the lesions (56%) were invasive carcinoma and four (44%) were ductal carcinoma in situ (DCIS). High-risk lesions, including atypical ductal hyperplasia (ADH) and atypical lobular hyperplasia (ALH), were found in 6.5 % (4/62) of the lesions, while 3 % (2/62) of the lesions contained lobular carcinoma in situ (LCIS). Cancer plus high risk lesions were found in 15/62 (24%) lesions or 14/50 (28%) of women who underwent biopsy.

CONCLUSION

The data in this study supports findings from other studies conducted by large research institutions. In this regard, it is important that community-based hospitals, such as the one operating this breast MR program, can achieve the same positive predictive values as those found in data emanating from academic institutions.

Magnetic Resonance-Guided Biopsies and Localizations of the Breast

OBJECTIVE

The objective of this study was to evaluate the performance of a new commercially available open breast coil and compatible intervention device (Machnet) for magnetic resonance image (MRI)-guided breast interventions.

MATERIALS AND METHODS

Breast lesions detected on MRI were evaluated using MRI-guided core biopsy (n = 20) and/or preoperative wire localization (n = 23) on histologic outcome and accuracy of localization. Time needed to perform a procedure and occurring problems were recorded.

RESULTS

Mean lesion size was <10 mm. Two of 20 lesions could not be biopsied because they were out of range for the device. Biopsies were conclusive in half of the cases; most lesions missed were <10 mm. The average accuracy for needle placement in the localization procedures was less than 2 mm (range, 0-5 mm). The average procedure time was 40 minutes for a biopsy procedure and 33 minutes for an MRI-guided localization.

CONCLUSIONS

Preoperative MRI-guided localizations can be performed quickly and accurately. However, in MRI-guided core biopsies, especially in small lesions, the device does not guarantee conclusive histologic evaluation of the lesion targeted.

Clipmarkierung nach MRT-gesteuerter Vakuumbiopsie der Mamma

PURPOSE

The purpose of our study was to determine the placement accuracy, usefulness as a guide for wire localization, and long-term stability of tissue marker clips following MR-guided vacuum-assisted biopsy (VB) of breast lesions.

METHODS

During a 2-year period, MR-guided VB with an 11-gauge device was performed in 79 lesions. In 26 lesions a marker clip was placed at the biopsy site.

RESULTS

In 18 cases, the clip was shown to be closely adjacent to the lesion on post-interventional MR images. In seven cases in which minor bleeding occurred, the clip dislocated (< or =15 mm) in the direction of the needle pathway. In one case dislocation in the dorsal direction (< or =5 mm) was observed. In eight cases with a malignant or borderline histology according to the VB, the marker clips served as targets for mammographically guided wire localization. In all of those patients, histology results derived from open surgery confirmed those of VB. Eighteen patients with benign findings according to the VB were followed up 6 months later. Among these cases we found a significant displacement of the marker clip in one case (3 cm). The clip generally caused a round artifact (diameter of 9+/-2 mm). In two cases it was not possible to determine whether the lesion had been removed completely or was just behind the artifact caused by the clip.

CONCLUSION

Based on our results, clip marker placement following MR-guided vacuum biopsy should be called into question due to the possibility of masking the lesion by a metallic artifact and because of possible dislocation.

Low-field versus high-field MRI in diagnosing breast disorders

We evaluated the performance of low-field MRI in breast disorders by comparing it with high-field MRI and biopsy results. Twenty-eight consecutive patients who were able to undergo two magnetic resonance examinations on following days were examined by high-field and low-field MRI. After T1-weighted sagittal images had been obtained a dynamic 3D axial study was performed followed by the acquisition of contrast-enhanced T1-weighted sagittal images. The images were analyzed separately by two radiologists paying attention to lesion morphology and enhancement kinetics. Six patients had problems in both breasts (34 breasts studied). The results were compared with biopsy results of 27 breasts. There were 16 malignant lesions, two fibroadenomas and nine other benign lesions. The inter-magnetic-resonance-scanner kappa value was 0.77 (substantial agreement), while the interobserver kappa value was 0.86 and 0.81 at low and high field, respectively (excellent agreement). The sensitivity was 100 and 100%, the specificity was 82 and 73% and the accuracy was 93 and 89% at low and high field, respectively. The mean lesion size was 2 cm and the smallest malignant lesion was 8 mm in diameter. Low-field MRI is a promising tool for breast imaging. Larger materials and smaller lesions are needed to evaluate its true sensitivity and specificity.

Design of an MRI-Compatible Robotic Stereotactic Device for Minimally Invasive Interventions in the Breast†

The objective of this work was to develop a robotic device to perform biopsy and therapeutic interventions in the breast with real-time magnetic resonance imaging (MRI) guidance. The device was designed to allow for (i) stabilization of the breast by compression, (ii) definition of the interventional probe trajectory by setting the height and pitch of a probe insertion apparatus, and (iii) positioning of an interventional probe by setting the depth of insertion. The apparatus is fitted with five computer-controlled degrees of freedom for delivering an interventional procedure. The entire device is constructed of MR compatible materials, i.e. nonmagnetic and non-conductive, to eliminate artifacts and distortion of the MR images. The apparatus is remotely controlled by means of ultrasonic motors and a graphical user interface, providing real-time MR-guided planning and monitoring of the operation. Joint motion measurements found probe placement in less than 50 s and sub-millimeter repeatability of the probe tip for same-direction point-to-point movements. However, backlash in the rotation joint may incur probe tip positional errors of up to 5 mm at a distance of 40 mm from the rotation axis, which may occur for women with large breasts. The imprecision caused by this backlash becomes negligible as the probe tip nears the rotation axis. Real-time MR-guidance will allow the physician to correct this error. Compatibility of the device within the MR environment was successfully tested on a 4 Tesla MR human scanner.

Differentiation of benign and malignant sub-1 cm breast lesions using dynamic contrast enhanced MRI

The purpose of this work is to assess the additional benefit of MRI-based morphology and quantification of contrast enhancement in the differential diagnosis of sub-1cm breast lesions. Forty-three women with suspected breast cancer were examined using X-ray mammography, ultrasound mammography, and MRI. Dynamic contrast imaging was performed and relative enhancement at various time-points was calculated. The dynamic data was also processed using a two-compartment pharmacokinetic model. Radiological interpretation of high-resolution post-contrast images revealed a similar accuracy (69%) compared to X-ray mammography (69%) and ultrasound mammography (67%). The best individual parameter calculated from the dynamic images was found to be the exchange rate constant which revealed a diagnostic accuracy of 0.74 +/- 0.08. When information from the post-contrast images and dynamic data was combined in a logistic regression model a diagnostic accuracy of 0.92 +/- 0.03 was achieved. In conclusion, MR imaging of small breast lesions is feasible and the incorporation of quantitative MR derived parameters is beneficial.

Fast MRI-Guided Vacuum-Assisted Breast Biopsy:Initial Experience

OBJECTIVE

The purpose of this study was to evaluate a new method for performing MRI-guided vacuum-assisted breast biopsy in a study of lesions that had subsequent surgical excision. SUBJECTS AND METHODS. Twenty women scheduled for MRI-guided needle localization and surgical biopsy were prospectively entered in the study. MRI-guided biopsy was performed with a vacuum-assisted probe, followed by placement of a localizing clip, and then needle localization for surgical excision. Vacuum-assisted biopsy and surgical histology were correlated.

RESULTS

Vacuum-assisted biopsy was successfully performed in 19 (95%) of the 20 women. The median size of 27 MRI-detected lesions that had biopsy was 1.0 cm (range, 0.4-6.4 cm). Cancer was present in eight (30%) of 27 lesions and in six (32%) of 19 women; among these eight cancers, five were infiltrating and three were ductal carcinoma in situ (DCIS). Among these 27 lesions, histology was benign at vacuum-assisted biopsy and at surgery in 19 (70%), cancer at vacuum-assisted biopsy in six (22%), atypical ductal hyperplasia at vacuum-assisted biopsy and DCIS at surgery in one (4%), and benign at vacuum-assisted biopsy with surgery showing microscopic DCIS that was occult at MRI in one (4%). The median time to perform vacuum-assisted biopsy of a single lesion was 35 min (mean, 35 min; range, 24-48 min). Placement of a localizing clip, attempted in 26 lesions, was successful in 25 (96%) of 26, and the clip was retrieved on specimen radiography in 22 (96%) of 23. One complication occurred: a hematoma that resolved with compression.

CONCLUSION

MRI-guided vacuum-assisted biopsy is a fast, safe, and accurate alternative to surgical biopsy for breast lesions detected on MRI.

Current applications and future direction of MR mammography

Compared with triple assessment for symptomatic and occult breast disease, magnetic resonance mammography (MRM) offers higher sensitivity for the detection of multifocal cancer, which is important in selecting patients appropriately for breast-conserving surgery. It is an ideal tool for the screening of patients with a high risk of breast cancer or where there is axillary disease or nipple discharge and conventional imaging has not revealed the primary focus. Techniques are now available to biopsy lesions only apparent on MRM. MRM can differentiate scar tissue from tumour; therefore, it is useful in patients in which there is possible recurrent disease. Clinical and X-ray mammographic assessment of response to neoadjuvant chemotherapy may be unreliable because of replacement of the tumour with scar tissue. MRM can identify responders and nonresponders with more accuracy. It is the modality of choice for the assessment of breast implants for rupture with accuracy higher than X-ray mammography and ultrasound. Advances in both spatial and temporal resolutions, the imaging sequences employed, pharmacokinetic modelling of contrast uptake, the use of dedicated and now phased-array breast coils, and gadolinium-based contrast agents have all played their part in the advancement of this imaging technique. Despite the limitations of patient compliance, scan-time and cost, this review describes how MRM has become a valuable tool in breast disease, especially in cases of diagnostic uncertainty. However, MRM must make the transition from research institutions into routine clinical practice.

Preoperative assessment of breast cancer: sonography versus MR imaging

OBJECTIVE

The purposes of our study were to compare the diagnostic value of whole-breast sonography and MR imaging as adjunctive techniques to mammography and to determine whether MR imaging should be used routinely in the preoperative assessment of patients with suspected breast cancer.

SUBJECTS AND METHODS

. One hundred four women (age range, 34-84 years; mean age, 60 years) with findings highly suggestive of malignancy in the breast were examined with mammography, sonography, and dynamic MR imaging before undergoing surgery. All visualized suspicious lesions were correlated histologically. The diagnostic relevance of sonographic and MR imaging findings was compared with the diagnostic value of the findings of clinical examination and mammography alone.

RESULTS

. Twenty-seven tumors showed multifocal or multicentric invasive growth at pathology. Of these 27, 48% were correctly diagnosed via mammography alone; 63%, via the combination of mammography and sonography; and 81%, via MR imaging. Nine of the index tumors were invisible on mammography but were detected on sonography. Use of sonography benefited 13 patients and produced two studies with false-positive findings. Use of MR imaging benefited seven patients and produced eight studies with false-positive findings. In summary, 93% of all patients gained no advantage from MR imaging. Relevant additional findings were significantly more frequent in patients with dense breasts.

CONCLUSION

Although MR imaging is most sensitive for the detection of small tumors, routine preoperative MR imaging appears to be unnecessary for most patients if a combination of mammography and whole-breast sonography is used. Additional MR imaging can be restricted to problematic cases in women with dense breast parenchyma.

MR imaging-detected breast lesions: histopathologic correlation of lesion characteristics and signal intensity data

OBJECTIVE

The aim of our study was to differentiate benign from malignant breast lesions that had been detected exclusively on MR imaging by analyzing qualitative and quantitative lesion characteristics.

MATERIALS AND METHODS

We performed 51 MR imaging-guided breast interventions (41 preoperative lesion localizations and 10 large-core needle biopsies) in 45 patients with exclusively MR imaging-detected lesions. All patients had previously undergone diagnostic dynamic contrast-enhanced MR imaging of the breast with a double breast coil at 1.0 T (n = 36) or 1.5 T (n = 15). The diagnostic MR images were evaluated on a workstation. Lesion morphology (size, shape, margin type, enhancement pattern), signal intensity parameters (time to peak enhancement, maximum slope of enhancement curve, washout, relative water content), and scores analogous to the Breast Imaging Reporting and Data System (BI-RADS) categories were correlated with histology.

RESULTS

Histology revealed malignancy in 37.3% (19/51) of the lesions. The positive predictive value for malignancy of exclusively MR imaging-detectable lesions increased as the analogous BI-RADS category increased. Late inhomogeneous contrast enhancement was the only morphologic criterion that was statistically significantly correlated with malignancy. Malignant and benign lesions did not differ significantly in any of the quantitatively evaluated signal intensity parameters. Carcinomas showed a tendency toward faster and stronger enhancement and stronger washout.

CONCLUSION

The classification of exclusively MR imaging-detectable breast lesions according to a combination of morphologic and perfusion parameters including the late enhancement pattern helps identify the lesions for which interventional MR imaging is required. Quantitative signal intensity data alone do not suffice.

MR-guided percutaneous core biopsy of small breast lesions: first experience with a vertically open 0.5T scanner

PURPOSE

The growing use of highly sensitive but only moderate specific breast MRI requires the development of both minimal-invasive as well as precise biopsy systems. The aim of the study was to prove the accuracy and feasibility of a biopsy procedure carried out in prone position in a vertically opened MR imager.

MATERIALS AND METHODS

The biopsies were carried out in 21 women with lesions visible on MRI alone using an open breast coil with an integrated biopsy device. A 14 G coaxial needle was placed under near real-time MRI-guidance. After the tip of this needle was verified in contact with the lesion, we used a non MR-compatible, but MR-safe biopsy gun with a 16 G canula to take four to eight cores.

RESULTS

We found eight malignant and 12 benign lesions. In one patient the procedure was not successful. In case of malignancy, the operation confirmed the diagnosis in all cases. The 12/21 patients with benign lesions have been followed without evidence of lesions growth over eight to 28 months.

CONCLUSION

The described procedure allows MRI-guided minimal invasive core biopsy of small breast lesions (five to 17 mm) with a high degree of accuracy.

MR-guided interventional breast procedures considering vacuum biopsy in particular

Histologic work-up of just MR-detected breast lesions has become essential with increasing use of contrast-enhanced MR imaging. In the present article an overview is given about the different MR-guided breast interventions, performed since 1990. Presently, for reasons of costs and image quality closed magnets are most widely used. The following approaches have been described: MR-guided freehand localization in supine position, stereotaxic localization in supine position and most frequently used localization in the prone position by means of a compression device that immobilises the breast to prevent tissue shift during intervention. Only limited experience exists with interventions on open magnets. MR-guided wire localization is a well-established procedure. Recently, percutaneous vacuum biopsy of enhancing breast lesions has become possible under MR guidance. The new system allows accurate and safe access to lesions in any location of the breast and direct check-up of representative excision by visualisation of the cavity. Thus reliable histologic evaluation of lesions smaller than 10 mm is possible with this approach.

Interventional and intraoperative magnetic resonance imaging

The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of imaging to guide minimally invasive therapy. The program combines interventional and intraoperative magnetic resonance imaging (MRI) with high-performance computing and novel therapeutic devices. In clinical practice the multidisciplinary program provides for the investigation of a wide range of interventional and surgical procedures. The Signa SP 0.5 T superconducting MRI system (GE Medical Systems, Milwaukee, WI) has a 56-cm-wide vertical gap, allowing access to the patient and permitting the execution of interactive MRI-guided procedures. This system is integrated with an optical tracking system and utilizes flexible surface coils and MRI-compatible displays to facilitate procedures. Images are obtained with routine pulse sequences. Nearly real-time imaging, with fast gradient-recalled echo sequences, may be acquired at a rate of one image every 1.5 s with interactive image plane selection. Since 1994, more than 800 of these procedures, including various percutaneous procedures and open surgeries, have been successfully performed at Brigham and Women's Hospital (Boston, MA).

Magnetic resonance imaging-guided core needle biopsy and needle localized excision of occult breast lesions

BACKGROUND

Breast magnetic resonance imaging (MRI) has been reported to be twice as sensitive and three times more specific in detecting breast cancer. We report a series of MRI-guided stereotactic breast biopsies (SCNBB) and needle localized breast biopsies (NLBB) to evaluate MRI as a localization tool.

METHODS

Forty-one breast lesions were identified in 39 patients who subsequently had SCNBB or NLBB. Suspicious areas of enhancement were stereotactically biopsied with 16-G core biopsy needles or localized with 22-G wires for excision under laser guidance.

RESULTS

Forty-one breast lesions were identified from 1,292 breast MRIs. SCNBB identified three malignancies and two areas of atypia. Two additional cancers were found after NLBB. In patients having NLBB alone, five cancers and two areas of atypia were identified.

CONCLUSIONS

In this initial series, breast MRI-guided SCNBB and NLBB were valuable tools in the management of patients with suspicious abnormalities seen only on MRI.

Magnetic resonance imaging of the breast

BACKGROUND

Magnetic resonance imaging (MRI) has the potential to become a useful adjunct in breast imaging. Contrast-enhanced breast MRI has demonstrated a high sensitivity in the detection of invasive breast cancer. In clinical studies, breast MRI has often altered the course of patient care. Although promising results have been generated, MRI of the breast is currently in a development stage.

METHODS

The authors reviewed the literature on the potential indications, sensitivity, specificity, and limitations of MRI of the breast.

RESULTS

Reported advantages of MRI of the breast over conventional imaging techniques include improved staging and treatment planning, enhanced evaluation of the augmented breast, better detection of recurrence, and improved screening of high-risk women. Contrast-enhanced breast MRI is a sensitive modality for detecting breast cancer, but its variable specificity is a major limitation.

CONCLUSIONS

MRI of the breast is emerging as a valuable adjunct to mammography and sonography for specific clinical indications. Additional clinical studies that define indications, interpretation criteria, imaging parameters, and cost effectiveness are needed. A multi-institutional study designed to address these issues is in progress.

An apparatus for MR-guided breast lesion localization and core biopsy: design and preliminary results

System design and initial results are presented from a new unilateral MR-guided breast lesion localization and core biopsy system. Over 150 imaging studies, an accuracy study on phantoms with 50 localization wire deployments and 33 core biopsy trials, and 19 clinical procedures are reported. The mean spatial accuracy from the lesion center for a 20-gauge (G) needle (N = 13) was within 1.2 +/- 1.4 mm (SD) and for a 14G biopsy (N = 4) 0.8 +/- 1.1 mm. For sampling using a 16G core through a 14G needle, the mean accuracy was 5.6 mm (N = 2). The needle guide geometry imposed a small, calculable targeting error. For phantom measurements using the 20G device, the mean geometry-induced error was 0.73 +/- 0.43 mm. However, this contribution was, on average, 42% of the mean measured 2.35 +/- 1.65 mm offset. The new device design provided an accurate and simple guidance method for localization or core biopsy of MR-visible breast lesions.

MR imaging of the breast for the detection, diagnosis, and staging of breast cancer

With the introduction of contrast agents, advances in surface coil technology, and development of new imaging protocols, contrast agent-enhanced magnetic resonance (MR) imaging has emerged as a promising modality for detection, diagnosis, and staging of breast cancer. The reported sensitivity of MR imaging for the visualization of invasive cancer has approached 100%. There are many examples in the literature of MR imaging--demonstrated mammographically, sonographically, and clinically occult breast cancer. Often, breast cancer detected on MR images has resulted in a change in patient care. Despite these results, there are many unresolved issues, including no defined standard technique for contrast-enhanced breast MR imaging, no standard interpretation criteria for evaluating such studies, no consensus on what constitutes clinically important enhancement, and no clearly defined clinical indications for the use of MR imaging. Furthermore, this technology remains costly, and issues of cost-effectiveness and cost competition from percutaneous biopsy have yet to be fully addressed. These factors along with the lack of commercially available MR imaging--guided localization and biopsy systems have slowed the transfer of this imaging technology from research centers to clinical breast imaging practices. Technical requirements, potential clinical applications, and potential pitfalls and limitations of contrast-enhanced MR imaging as a method to help detect, diagnose, and stage breast cancer will be described.

MR imaging--guided large-core (14-gauge) needle biopsy of small lesions visible at breast MR imaging alone

PURPOSE

To report our experience with magnetic resonance (MR) imaging-guided large-core breast biopsy of lesions visible at breast MR imaging only.

MATERIALS AND METHODS

Stereotactic large-core (14-gauge) needle biopsy of 78 lesions visible at MR imaging only was performed with MR imaging guidance in 59 patients. Results were validated with excisional biopsy or mastectomy in 42 lesions and with radiologic-pathologic correlation and/or follow-up MR imaging for at least 2 years in another 17 lesions. The accuracy of MR imaging--guided core biopsy was determined for those 59 lesions with established validation. The effect on patient treatment was evaluated by comparing the prebiopsy treatment plan with the ultimate treatment.

RESULTS

Histologic diagnosis from core biopsy was possible in 77 (99%) of 78 lesions. In the 59 lesions with established validation, the diagnostic accuracy of MR imaging--guided core biopsy was 98% (58 of 59). Successful MR imaging--guided core biopsy findings changed treatment in 70% (54 of 77) of lesions. Difficulties were due to the unsatisfactory performance of earlier types of MR imaging--compatible biopsy guns and decreasing target visibility during intervention.

CONCLUSION

MR imaging--guided large-core stereotactic breast biopsy is sufficiently accurate for obtaining histologic proof of lesions visible only at MR imaging. It can change patient treatment by reducing unnecessary surgical biopsy and can enable one-step surgery for breast cancers.

Localization and biopsy of breast lesions by magnetic resonance imaging guidance

Contrast-enhanced MRI of the breast has proved to be a valuable tool in the detection and work-up of breast lesions. Most of these lesions are small and not visible by other imaging modalities, such as mammography or US. Thus, only MR-guided preoperative localization techniques or MR-guided percutaneous biopsy can provide a histologic work-up of such lesions. MR-guided preoperative localization seems to be a well-established procedure. However, MR-guided biopsy is still problematic. Although prototypical biopsy systems have been developed, considerable progress is still required. Problems exist with MR-guided biopsy due to severe needle artifacts and tissue shift during the intervention. Thus, needle biopsy currently is not recommended for lesions smaller than 10 mm. This work reviews current techniques for MR-guided preoperative localization and percutaneous biopsy in breast lesions. The diagnostic accuracy achievable with these techniques will be discussed, as well as the potential for new research opportunities and directions. J. Magn. Reson. Imaging 2001;13:903-911.

Bilateral open breast coil and compatible intervention device

Dynamic contrast-enhanced breast MRI is an extremely sensitive method for breast lesion detection. For MR-only detected lesions it is essential that needle biopsy or localization prior to surgery is carried out under MR guidance. This work describes a bilateral open breast coil and prototype intervention device, which may be used in these situations. Results demonstrate that the open coil provides images superior to those obtained with a conventional closed breast coil. Initial phantom tests with the intervention device indicate a potential for this system to be used in the MR-guided localization of breast lesions. J. Magn. Reson. Imaging 2000;12:984-990.

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.

Probe with chest shielding for improved breast MRI

The design and construction of an RF coil system for use in MR breast imaging is described. The two-ring, tuned Helmholtz coil, with its axis perpendicular to the chest, surrounds a single pendant breast and is coupled both internally and to the MRI transmitter/receiver by mutual induction. The addition of two symmetrical RF shields minimizes losses in the chest and significantly improves performance. Images obtained from eight healthy volunteers showed that the coil permitted imaging of breasts of diverse size with an in-plane resolution of 0.27 x 0.27 mm and a slice thickness of less than 2 mm at a field strength of 3 T as well as 1.5 T. The use of shields with surface coils in general is advocated as a method for improving signal-to-noise ratio. Magn Reson Med 43:917-920, 2000.

Localization of breast lesions shown only on MRI--a review for the UK Study of MRI Screening for Breast Cancer. Advisory Group of MARIBS

The UK study of screening for breast cancer compares mammography and dynamic contrast enhanced MRI of the breast in women at high genetic risk of developing cancer. Owing to the high sensitivity of MR in the breast, it is anticipated that some lesions will be visible only on MR. A key issue for the study is how to localize these lesions for histological verification and removal. This article reviews available methods and describes the current UK expertise and recent European developments. The use of MR compatible wires and markers has been explored in a phantom. The use of these markers in vivo is demonstrated in a case imaged by MR and mammography and further discussed. The susceptibility artefacts produced on MRI, and technical properties associated with these needles, wires and markers are discussed. The clinical pathway by which these lesions will be worked up for the study, and the quality control procedures for keeping the number of such biopsies to a minimum, are described. There is an urgent need for further centres in the UK to become proficient at removing lesions found only on MRI in support of this study and other breast MRI applications. The management of these lesions must be resolved in order to realize the full potential of MRI for screening for breast cancer in women at genetic risk, and for other diagnostic applications.

Breast carcinoma: effect of preoperative contrast-enhanced MR imaging on the therapeutic approach

PURPOSE

To determine if magnetic resonance (MR) imaging can help determine the therapeutic approach in women with breast cancer.

MATERIALS AND METHODS

Preoperative contrast-enhanced MR imaging of the breast was performed in 463 patients with probably benign lesions (n = 63), suspicious lesions (n = 230), or lesions highly suggestive of malignancy (n = 170) per established clinical, mammographic, and/or ultrasonographic (US) criteria. T1-weighted fast low-angle shot MR imaging was performed before and after administration of gadopenetetate dimeglumine. MR imaging findings were correlated with other imaging results and histopathologic findings. Special attention was paid to multifocality and multicentricity.

RESULTS

Histopathologic analysis revealed 143 benign and 405 malignant lesions. The sensitivity, specificity, and accuracy were 58%, 76%, and 62% for clinical examination; 86%, 32%, and 72% for conventional mammography; 75%, 80%, and 76% for US; and 93%, 65%, and 85% for contrast-enhanced MR imaging. Multifocality in 30 of 42 patients, multicentricity in 24 of 50 patients, and additional contralateral carcinomas in 15 of 19 patients were depicted with MR imaging alone. Due to the MR imaging findings, therapy was changed correctly in 66 patients (14.3%); unnecessary open biopsy was performed in 16 patients (3.5%).

CONCLUSION

Contrast-enhanced MR imaging of the breast is highly sensitive for invasive breast cancer. MR imaging may reveal unsuspected multifocal, multicentric, or contralateral breast carcinoma and result in therapy changes.

Computerized analysis of breast lesions in three dimensions using dynamic magnetic-resonance imaging

Contrast-enhanced magnetic resonance imaging (MRI) of the breast is known to reveal breast cancer with higher sensitivity than mammography alone. The specificity is, however, compromised by the observation that several benign masses take up contrast agent in addition to malignant lesions. The aim of this study is to increase the objectivity of breast cancer diagnosis in contrast-enhanced MRI by developing automated methods for computer-aided diagnosis. Our database consists of 27 MR studies from 27 patients. In each study, at least four MR series of both breasts are obtained using FLASH three-dimensional (3D) acquisition at 90 s time intervals after injection of Gadopentetate dimeglumine (Gd-DTPA) contrast agent. Each series consists of 64 coronal slices with a typical thickness of 2 mm, and a pixel size of 1.25 mm. The study contains 13 benign and 15 malignant lesions from which features are automatically extracted in 3D. These features include margin descriptors and radial gradient analysis as a function of time and space. Stepwise multiple regression is employed to obtain an effective subset of combined features. A final estimate of likelihood of malignancy is determined by linear discriminant analysis, and the performance of classification by round-robin testing and receiver operating characteristics (ROC) analysis. To assess the efficacy of 3D analysis, the study is repeated in two-dimensions (2D) using a representative slice through the middle of the lesion. In 2D and in 3D, radial gradient analysis and analysis of margin sharpness were found to be an effective combination to distinguish between benign and malignant masses (resulting area under the ROC curve: 0.96). Feature analysis in 3D was found to result in higher performance of lesion characterization than 2D feature analysis for the majority of single and combined features. In conclusion, automated feature extraction and classification has the potential to complement the interpretation of radiologists in an objective, consistent, and accurate way.

Contrast-enhanced breast MRI for cancer detection using a commercially available system--a perspective

The diagnosis and treatment of breast cancer are dependent upon early detection of the disease by physical examination and mammography. Although mammography is a relatively good and cost-effective method of early breast cancer detection, there are some inherent weaknesses associated with this imaging modality that limit its sensitivity and specificity. Contrast-enhanced MRI of the breasts provides the additional capability to answer questions raised or unanswered with conventional imaging methods. This paper reviews contrast-enhanced breast MRI interpretation guidelines and patient preselection criteria for diagnostic problem cases. Technical aspects using a commercially available three-dimensional (3D) spoiled gradient-echo technique are discussed.

Interactive MR-guided, 14-gauge core-needle biopsy of enhancing lesions in a breast phantom mode

RATIONALE AND OBJECTIVES

The authors attempted to determine the accuracy of magnetic resonance (MR) imaging-guided core-needle biopsy performed with a titanium biopsy needle in a breast phantom.

MATERIALS AND METHODS

Eight 6-7-mm lesions were created at random positions in a lard breast phantom. Each 0.2-mL lesion contained 0.118 mg of gadopentetate dimeglumine, 0.0025 mL of methylene blue dye, and 23.8 mg of gelatin. Rapid fast spin-echo MR imaging was used to guide placement of a 14-gauge titanium core-biopsy needle. A 1.5-T MR imager was used with an open-platform phased-array breast coil.

RESULTS

Visualization of blue dye in core specimens confirmed successful biopsy in 16 of 16 attempts. One (n = 13) or two (n = 3) passes through the "skin" of the phantom were necessary for biopsy. The needle trajectory was adjusted less than three times for each pass through the "skin" in 15 of 16 biopsies. Cores that contained lesion material were obtained in the first sample in 15 of 16 biopsies. On T1-weighted images, needles cast 7-mm-diameter artifacts.

CONCLUSION

MR imaging can be used accurately to guide core-needle biopsy of 6-7-mm lesions in a breast phantom.