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.     

Whole-body high-field-strength (3.0-T) MR imaging in clinical practice. Part II. Technical considerations and clinical applications

This is the second part of a two-part series on the clinical applications of high-field-strength (3.0-T) magnetic resonance (MR) imaging and spectroscopy. In this part, the current level of evidence regarding the use of higher magnetic field strengths for cardiac imaging techniques (including the assessment of cardiac anatomy and function), breast and pelvic imaging, musculoskeletal applications, pediatric imaging, and MR spectroscopy is presented. Published data are interpreted from the perspective of the clinical radiologist. Specific difficulties associated with high-field-strength MR for body imaging and for spectroscopic applications are reviewed and compared with the expected or documented added value of high-field-strength MR for clinical patient care. The overall number of studies published on clinical body high-field-strength MR is still small, and there is evidence for a clinical advantage for selected, but not all, body MR imaging applications. Even without published evidence, clinical experience suggests substantial clinical advantages for musculoskeletal and pediatric applications.     

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.     

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.     

MR imaging-guided sonography followed by fine-needle aspiration cytology in occult carcinoma of the breast

OBJECTIVE: In patients with axillary metastases as clinical evidence of possible occult breast cancer, a combined approach of MR imaging, sonography, and aspiration biopsy cytology was evaluated. SUBJECTS AND METHODS: Thirty-one women with metastatic adenocarcinoma in their axillary lymph nodes originating from an unknown primary site underwent MR imaging of the breast because physical examination and mammography findings were normal. Twenty of the 31 women had no history of malignancy, 10 had been previously treated for contralateral breast cancer, and one patient had nodal metastases in the contralateral axilla at the time breast cancer was detected. When a contrast-enhancing lesion was revealed on MR imaging of the breast, sonography and fine-needle aspiration cytology were also performed. RESULTS: MR imaging revealed the primary breast cancer in eight (40%) of the 20 patients without a history of malignancy. MR imaging of the breast revealed a second primary cancer in three (27%) of the 11 patients with previous or simultaneous breast cancer. All lesions were identified with sonography and verified by cytology and histology. CONCLUSION: In women with axillary lymph node metastases from adenocarcinoma, MR imaging of the breast should be added to clinical examination and mammography before defining the breast cancer as occult. The combined approach of MR imaging, sonography, and aspiration fine-needle cytology is a good alternative to the MR imaging-guided biopsy.     

MR lesion detection in a breast cancer population

Implementation of MR imaging of the breast as an extension of the existing imaging modalities in the diagnosis of breast cancer was evaluated in a university cancer center. MR imaging of the breast was performed in 54 patients, in whom the MR results were compared with the triple test (the combination of clinical examination, mammographic evaluation, and cytology) and the final histological diagnosis. MR imaging of the breast depicted 30 of the 33 malignancies (sensitivity, 91%). In two of the malignancies, the carcinoma was clinically and mammographically occult. For the three patients with a false-negative MRI diagnosis, the conventional mammography showed suspicious clustered microcalcifications as a sign of in situ carcinoma. For seven patients, MR imaging of the breast incorrectly suggested the presence of a malignant lesion (specificity, 67%). To improve MR specificity, we perform MR-guided ultrasonographic fine-needle aspiration biopsy (FNAB). Although MR imaging of the breast is a highly sensitive examination, conventional x-ray mammography remains the most efficient imaging modality in the diagnosis of breast cancer. In our patient population, MR imaging of the breast had additional value for women with mammographically dense breast tissue and especially for patients with clinical evidence of breast carcinoma that could not be detected with conventional diagnostic methods.     

Whole-body high-field-strength (3.0-T) MR Imaging in Clinical Practice. Part I. Technical considerations and clinical applications

In the year 2002, magnetic field strength of more than 2 T was cleared for clinical patient care. Since then, an increasing number of magnetic resonance (MR) systems operating at a field strength of 3.0 T (and higher) have been installed worldwide. This article is the first of a two-part series on clinical high-field-strength MR imaging. Some basic physical effects of higher magnetic fields as they pertain to clinical MR imaging and spectroscopy are reviewed, from the perspective of a clinical radiologist, and strategies that are useful to avoid magnetic field-related difficulties and artifacts are discussed. Advantages and downsides, which can be expected for clinical MR, are presented and compared with the current level of evidence based on published data about MR of the brain and MR angiography. In the second part of the series, clinical applications regarding cardiac, breast, musculoskeletal, abdominopelvic, and pediatric MR and MR spectroscopy will be presented.     

Bildgebende Diagnostik des Mammakarzinoms

Advances in imaging of the female breast have substantially influenced the diagnosis and probably also the therapy and prognosis of breast cancer in the past few years. This article gives an overview of the most important imaging modalities in the diagnosis of breast cancer. Digital mammography is considered to be the gold standard for the early detection of breast cancer. Digital breast tomosynthesis can increase the diagnostic accuracy of mammography and is used for the assessment of equivocal or suspicious mammography findings. Other modalities, such as ultrasound and contrast-enhanced magnetic resonance imaging (MRI) play an important role in the diagnostics, staging and follow-up of breast cancer. Percutaneous needle biopsy is a rapid and minimally invasive method for the histological verification of breast cancer. New breast imaging modalities, such as contrast-enhanced spectral mammography, diffusion-weighted MRI and MR spectroscopy can possibly further improve breast cancer diagnostics; however, further studies are necessary to prove the advantages of these methods so that they cannot yet be recommended for routine clinical use.     

Clinical usefulness of MR imaging of the breast in the evaluation of the problematic mammogram.

OBJECTIVE: This study was undertaken to determine the usefulness of MR imaging of the breast as an adjunct to mammography in problematic cases in which the significance, presence, or location of an abnormality could not be determined. MATERIALS AND METHODS: From January 1993 through February 1998, 86 lesions for which histologic or mammographic follow-up was available were evaluated by breast MR imaging because of equivocal findings on mammography. MR studies were performed with a dedicated breast multicoil on a 1.5-T scanner. Early studies were done using a T1-weighted two-dimensional spin-echo sequence before and after the administration of contrast material. Later studies were performed using a three-dimensional fast spoiled gradient sequence with fat suppression. Studies were considered to be positive for an abnormality if a focal area of enhancement was seen after contrast administration. RESULTS: MR imaging had positive findings in 38 sites. Twenty-six of these sites corresponded in location to the mammographic abnormality that had prompted the recommendation for MR imaging. The remaining 12 sites occurred in areas not suspected mammographically. At biopsy, 10 (26%) of the 38 positive sites were malignant. MR imaging had negative findings at 60 other sites that had been suspected mammographically. Of these 60 sites, six were treated with excision, all with benign results; the remaining 54 sites showed mammographic stability on follow-up that ranged from 5 to 66 months (mean, 19 months). CONCLUSION: MR imaging of the breast can be a valuable adjunct to mammography for selected problematic cases.     

Targeted ultrasound for MR-detected lesions in breast cancer patients.

OBJECTIVE: To investigate the usefulness of targeted ultrasound (US) in the identification of additional suspicious lesions found by magnetic resonance (MR) imaging in breast cancer patients and the changes in treatment based on the identification of the lesions by the use of targeted US. MATERIALS AND METHODS: One-hundred forty nine patients who underwent breast MR imaging for a preoperative evaluation of breast cancer between January 2002 and July 2004 were included in the study. We searched all cases for any additional lesions that were found initially by MR imaging and investigated the performance of targeted US in identifying the lesions. We also investigated their pathological outcomes and changes in treatment as a result of lesion identification. RESULTS: Of the 149 patients with breast cancer, additional suspicious lesions were detected with MR imaging in 62 patients (42%). Of the 69 additional lesions found in those 62 patients, 26 (38%) were confirmed as cancers by histology. Thirty-eight lesions in 31 patients were examined with targeted US and were histologically revealed as cancers in 18 (47%), high risk lesions in two (5%), benign lesions in 15 (39%), and unidentified lesions in three (8%). The cancer rate was statistically higher in lesions with a US correlate than in lesions without a US correlate (p = 0.028). Of 31 patients, the surgical plan was altered in 27 (87%). The use of targeted US justified a change in treatment for 22 patients (81%) and misled five patients (19%) into having an unnecessary surgical excision. CONCLUSION: Targeted US can play a useful role in the evaluation of additional suspicious lesions detected by MR imaging in breast cancer patients, but is limited in lesions without a US correlate.     

Breast magnetic resonance imaging

Mammography has long been considered the gold standard for screening breast cancer. Although it reduces the risk of breast cancer mortality by enabling early diagnosis, it does not detect all breast cancers. Numerous breast imaging technologies are emerging as effective adjunctive diagnostic tools when mammography results are negative or inconclusive. Contrast-enhanced magnetic resonance (CE-MR) imaging, in particular, has demonstrated a high sensitivity and has proven to be most effective, especially with patients at high risk for developing breast cancer. This article discusses the clinical applications for breast MR imaging, use of CE-MR for breast cancer detection, and other emerging breast imaging technologies.     

Detecting breast cancer with non-contrast MR imaging: combining diffusion-weighted and STIR imaging.

We combined diffusion-weighted (DWI) and short TI inversion recovery (STIR) imaging to evaluate the diagnostic capability of non-contrast magnetic resonance (MR) imaging to detect breast cancer. Seventy women patients underwent mammography and MR imaging with combined DWI (b factor: 1000) and STIR that revealed malignancy, and postoperative pathological examination confirmed breast cancer. Interpreted images were evaluated for sensitivity, false negative rate (FN), sensitivity by pT, and sensitivity by background density of the mammary gland. Of the 70 cases, 68 were diagnosed as cancer by DWI and STIR (sensitivity, 97% [68/70]; FN, 2.9% [2/70]). Sensitivities by pT were: pTis, 67% (4/6); pT1, 100% (33/33); and pT2-4, 100% (31/31). No significant differences were observed in sensitivity between pT1 and pT2-4 (P<0.001). Sensitivities by background density of mammary gland were: fatty/scattered fibroglandular tissue, 95% (20/21) and heterogeneous fibroglandular tissue/mostly fibroglandular tissue, 98% (48/49). No significant differences were observed (P<0.001). Two cases, an intraductal and an apocrine carcinoma, were incorrectly diagnosed by MR imaging. Precise diagnosis of breast cancer is possible with combined DWI and STIR, even in non-contrast MR imaging, regardless of the diameter or background density of mammary gland. It is hoped that non-contrast MR imaging that combines DWI and STIR will become an established clinical screening method.     

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.     

Contrast-enhanced magnetic resonance imaging of the breast

Contrast-enhanced magnetic resonance (MR) imaging is increasingly used as a complementary diagnostic modality in breast imaging. The sensitivity of MR imaging of the breast for malignancy has consistently been reported to be excellent. The specificity has been rather variable. Study methods and imaging techniques are not standardized and there is still a great deal of uncertainty about MR imaging's place in clinical practice. Nevertheless, radiologists should be familiar with the current technique and the varying MR appearance of breast tumors to improve the accuracy of this method. This paper reviews the techniques for breast MR imaging, the pathopysiologic basis of contrast enhancement in breast tumors, and the current knowledge about detection and differentiation of breast tumors. In addition, future directions for breast MR imaging are discussed.     

MR imaging assessment of the breast after breast conservation therapy: distinguishing benign from malignant lesions

Dynamic contrast material-enhanced magnetic resonance (MR) imaging has emerged as a valuable tool in evaluation of women who have undergone lumpectomy and whole-breast radiation therapy for breast cancer. Early diagnosis of local recurrence by means of close clinical and imaging follow-up is an important component of a breast-conserving strategy, as it may improve survival. In the post-breast conservation therapy (BCT) breast, resolving edema, fat necrosis, a small focal area of non-masslike enhancement (NMLE), and thin linear NMLE at the lumpectomy site can all be expected findings. In contrast, masslike enhancement or NMLE of ductal or segmental distribution can indicate recurrence. Therefore, at MR imaging of the post-BCT breast, it is important to identify lesions that are benign or appropriate for short-interval imaging surveillance to minimize unnecessary intervention, as well as to discern suspicious lesions and optimize the diagnosis of recurrence.     

MR imaging of the skin and nipple of the breast: differentiation between tumour recurrence and post-treatment change

Contrast-enhanced MR imaging of the breast has been found to be valuable in the assessment of local recurrence of previously treated breast cancer. We looked specifically at the appearances of the skin and nipple of the treated breast in order to describe the appearances of post-treatment change and recurrence in this region. Thirty-nine women treated for breast cancer had MR imaging of one or both breasts reviewed retrospectively with particular attention to the nipple and skin. The skin and chest wall were assessed for patients with mastectomies. All available histology of the skin and/or nipple, obtained following MR imaging, was reviewed. In patients who did not undergo surgery following MR imaging, clinical follow-up was obtained. Six of 39 cases had nodular enhancing areas seen on MR imaging, which correlated with histology demonstrating tumour recurrence within the skin and/or nipple. Of the remaining 33 patients, changes of linear or diffuse enhancement were seen in the skin and/or nipple of 15 patients. These changes were shown to be benign post-treatment changes at surgery/biopsy in 4 cases or by clinical follow-up in the remainder. In this article we demonstrate differing patterns of contrast enhancement within the skin and nipple in recurrent breast carcinoma vs. post-treatment changes. This suggests that contrast-enhanced MR imaging of the breast may be a useful tool in differentiating tumour recurrence from post-treatment changes within the skin and nipple.     

Cancer yield of probably benign breast MR examinations

PURPOSE: To evaluate the cancer yield, frequency of use, and follow-up compliance of breast MR examinations assessed as "probably benign." MATERIALS AND METHODS: We retrospectively reviewed our MR database of 809 consecutive examinations between January 2003 and June 2004. We identified all examinations that ultimately received an MR breast imaging reporting and data system (BI-RADS) 3 assessment and recommendation for a short-interval follow-up MR with or without an antecedent targeted ultrasound. The clinical indication for breast MR, date of the follow-up examination, follow-up assessment, and any pathology findings through June 2005 were collected from clinical records and radiology and pathology reports. Frequency of BI-RADS 3 use, follow-up compliance, and cancer yield were calculated. RESULTS: A total of 160 out of 809 (20%) examinations comprise the study population. A total of 100 out of 160 (63%) women returned for the recommended follow-up MR, in which three out of 100 (3%) were upgraded to BI-RADS 4 with biopsy recommended. One patient underwent biopsy and the result was benign. A total of seven out of 160 (4%) underwent mastectomy in lieu of MR for known cancer elsewhere in the breast. One out of seven mastectomy specimens contained malignancy that corresponded to the probably benign finding, resulting in a cancer yield of one out of 160 (0.6%). CONCLUSION: Our data suggest that follow-up MR is a valid alternative to biopsy for MR BI-RADS 3 lesions.     

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.     

Potential Clinical Applications of <Superscript>18</Superscript>F-Fluorodeoxyglucose Positron Emission Tomography/Magnetic Resonance Mammography in Breast Cancer

The whole-body positron emission tomography (PET)/magnetic resonance (MR) scan is a cutting edge technology providing comprehensive structural information from MR imaging and functional features from PET in a single session. Recent research findings and clinical experience have shown that ¹⁸F-fluorodeoxyglucose (FDG) whole-body PET/MR imaging has a diagnostic performance comparable with or superior to that of PET/CT in the field of oncology, including for breast cancer. In particular, FDG PET/MR mammography in the prone position with the breast hanging in a pendant manner can provide more comprehensive information about the metabolism, anatomy, and functional features of a breast lesion than a whole-body PET/MR scan. This article reports on current state-of-the-art PET/MR mammography in patients with breast cancer and the prospects for potential application in the future.