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Noncontrast-enhanced MRI for Evaluation of Breast Lesions
Guest Editorial
Noncontrast-enhanced MRI for Evaluation of Breast Lesions: Comparison of Noncontrast-enhanced High Spectral and Spatial Resolution (HiSS) Images versus Contrast-enhanced Fat-suppressed Images D. David Dershaw, MD This issue of Academic Radiology contains a report by Medved et al (1) on their experience with noncontrast breast magnetic resonance imaging (MRI) in the evaluation of breast lesions using high spectral and spatial resolution (HiSS). Within the constraints of the study protocol, the analysis of their data shows that differentiation of benign from malignant lesions using their noncontrast technique was comparable to that achieved with dynamic contrast MRI. The transformation of breast MRI into a noncontrast examination remains hypothetical, but some of the advantages that could be conveyed by noncontrast MRI technology are obvious. Contrast is expensive and requires placement of an intravenous line for administration. Its elimination would decrease cost and discomfort. For those few women with allergy to the contrast material or impaired renal function, MRI could become a feasible study. The usefulness of an imagining technique that is not limited by the time constraints of contrast washout in performing biopsy, particularly multiple sites or both breasts, is also self-evident. In the analysis of specific sites within the breast, the use of HiSS with other noncontrast MRI techniques could convey additional advantage to noncontrast MRI. Spectroscopy requires identification of the volume of the breast to be evaluated, as does the HiSS technique reported in this journal. Spectroscopy does not require contrast. If identification of the breast volume undergoing analysis could be done without using contrast, a noncontrast examination could be performed specifically to obtain high spatial resolution MRI images with spectroscopy data. Because HiSS enables MRI to be done with increased spatial resolution, significant improvement in the ability to diagnose disease could result. It is well known in breast imaging that fine imaging details can hold the key to diagnosis. Small spicules, not seen on routine mammogram but visualized only with magnification technique, convert the breast imager’s impression of a benign entity to that of Acad Radiol 2011; 18:1465–1466 Breast Imaging Service, Department of Radiology, Memorial Sloan-Kettering Cancer Center, 300 East 66th Street, New York, NY 10065. ªAUR, 2011 doi:10.1016/j.acra.2011.09.001
a possible malignancy. Within the context of MRI, the failure of MRI to image microcalcifications associated with breast carcinoma is a well-known cause of false-negative studies (2). If spatial resolution on MRI could be developed to the extent that microcalcifications were included in the data acquired during MRI, this would represent a significant advance in MRI imaging of breast disease. The ability to image such fine detail has been beyond the capabilities of MRI but has been one of the goals of improved MRI technology. Higher strength magnets have been incorporated into clinical MRI to achieve improved of spatial resolution, among other goals. This has led to the progressive increase in magnet strength from early equipment using 0.5 Tesla magnets to current technology incorporating 3.0 Tesla magnets. Although limited by its single-slice application in this report, HiSS imaging of specific lesions within the breast might improve diagnostic accuracy. As an isolated MRI technique eliminating the need to administer contrast, HiSS has the obvious limitation of sacrificing kinetic data. There is little doubt that as spatial resolution has improved and the value of lesion geometry in MRI diagnosis of breast disease has increased, the importance of lesion kinetics in diagnosis has waned. Washout remains a valuable indicator of malignancy, but even progressively enhancing lesions have been described as cancer, particularly ductal carcinoma in situ (3). Because computer-assisted detection (CAD) and diagnosis are based on kinetics, using CAD is not possible with HiSS imaging. Subtraction images are also contrast based and cannot be obtained with HiSS imaging. Many radiologists use these images to interpret MRI; if they were not generated, breast MRI interpretation would become radically different for these radiologists. The technology reported in this study has the technical limitations of being acquired only in a single section. Its authors report that its use to perform a full bilateral breast examination would require about 10 minutes. In its current incarnation, HiSS might be most important as an additional tool to increase data available from MRI to improve diagnostic specificity. Other tools, including spectroscopy and diffusionweighted imaging, open the possibility of improved diagnostic accuracy, diminishing the need to obtain tissue from benign lesions to confirm that they are not clinically important 1465
DERSHAW
(4,5). As other breast imaging techniques have demonstrated, improved spatial resolution—as well as the ability of HiSS to eliminate contrast-induced artifact—offers another tool to improve the specificity of the diagnosis of lesions within the breast. The resultant decrease in cost and anxiety associated with breast cancer screening and diagnosis conveys additional benefit. The automated MRI, performed by the technologist and delivered in the completed state to the radiologist for interpretation, cannot currently offer these benefits. Some advanced MRI technologies, including HiSS, are only applicable to specified sites within the breast. They are not technologies that can be used to interrogate the entire breast volume. The application of these advanced techniques to further refine the data contained in the breast MRI may require that the physician monitor the study as data are acquired and select which, if any, additional scanning techniques are necessary to maximize information obtained from the study. The future of breast MRI, as hinted at in this study, is still hypothetical. Some important limitations in the data reported by Medved et al should be pointed out. In clinical practice, the pivotal decision made by the breast imager is whether or not to biopsy a lesion. This is based on its likelihood of being malignant, but it is not the same as the decision whether or not a lesion is malignant. Therefore, the construct of Medved’s study does not truly test the clinical value of HiSS. Additionally, the study has compared noncontrast HiSS imaging results to contrast MRI without dynamic data. This potentially underestimates the diagnostic ability of contrast MRI, improving the results for HiSS. Importantly, the HiSS technology is currently applicable only to a single slice and cannot be used to interrogate the entire breast. If and when it can be used to evaluate both breasts during MRI, the time required
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for the study is about 10 minutes. It is possible that patient motion during this long scanning time could compromise the improvement in spatial resolution. Nonetheless, the usefulness of the MRI technique reported by Medved et al is not in its ability to replace contrast studies that include dynamic information, but in the possibility of adding additional information to the data currently obtained for the detection and diagnosis of breast cancer. It offers the potential to improve the specificity of breast imagers in determining what areas in the breast are malignant, diminishing the need to biopsy benign sites without sacrificing the sensitivity of detecting those that are malignant. It also raises the possibility that imaging technology will become increasingly radiologist dependent—that the full clinical advantage of high resolution anatomic and of functional imaging may require radiologist interpretation of images when they are being acquired so that specific techniques can be applied to maximize the benefits of imaging.
REFERENCES 1. Medved M, Fan X, Abe H, et al. Non-contrast enhanced MRI for evaluation of breast lesions: comparison of non-contrast enhanced high spectral and spatial resolution (HiSS) images vs. contrast enhanced fat-suppressed images. Acad Radiol 2011; 18:1467–1474. 2. Menell J, Morris E, Dershaw D, et al. Determination of presence and extent of pure ductal carcinoma in situ by mammography and MRI. Breast J 2005; 11:382–390. 3. Raza S, Vallejo M, Chikarmane SA, et al. Pure ductal carcinoma in situ: a range of MRI features. AJR Am J Roentgenol 2008; 191:689–699. 4. Bartella L, Morris E, Dershaw D, et al. Proton MR spectroscopy using choline peak as malignancy marker improves positive predictive for breast cancer diagnosis: preliminary study. Radiology 2006; 239:686–692. 5. Woodhams R, Ramadan S, Stanwell P, et al. Diffusion-weighted imaging of the breast: principles and clinical applications. RadioGraphics 2011; 31: 1059–1084.
Noncontrast-enhanced MRI for Evaluation of Breast Lesions: Comparison of Noncontrast-enhanced High Spectral and Spatial Resolution (HiSS) Images versus Contrast-enhanced Fat-suppressed Images D. David Dershaw, MD This issue of Academic Radiology contains a report by Medved et al (1) on their experience with noncontrast breast magnetic resonance imaging (MRI) in the evaluation of breast lesions using high spectral and spatial resolution (HiSS). Within the constraints of the study protocol, the analysis of their data shows that differentiation of benign from malignant lesions using their noncontrast technique was comparable to that achieved with dynamic contrast MRI. The transformation of breast MRI into a noncontrast examination remains hypothetical, but some of the advantages that could be conveyed by noncontrast MRI technology are obvious. Contrast is expensive and requires placement of an intravenous line for administration. Its elimination would decrease cost and discomfort. For those few women with allergy to the contrast material or impaired renal function, MRI could become a feasible study. The usefulness of an imagining technique that is not limited by the time constraints of contrast washout in performing biopsy, particularly multiple sites or both breasts, is also self-evident. In the analysis of specific sites within the breast, the use of HiSS with other noncontrast MRI techniques could convey additional advantage to noncontrast MRI. Spectroscopy requires identification of the volume of the breast to be evaluated, as does the HiSS technique reported in this journal. Spectroscopy does not require contrast. If identification of the breast volume undergoing analysis could be done without using contrast, a noncontrast examination could be performed specifically to obtain high spatial resolution MRI images with spectroscopy data. Because HiSS enables MRI to be done with increased spatial resolution, significant improvement in the ability to diagnose disease could result. It is well known in breast imaging that fine imaging details can hold the key to diagnosis. Small spicules, not seen on routine mammogram but visualized only with magnification technique, convert the breast imager’s impression of a benign entity to that of Acad Radiol 2011; 18:1465–1466 Breast Imaging Service, Department of Radiology, Memorial Sloan-Kettering Cancer Center, 300 East 66th Street, New York, NY 10065. ªAUR, 2011 doi:10.1016/j.acra.2011.09.001
a possible malignancy. Within the context of MRI, the failure of MRI to image microcalcifications associated with breast carcinoma is a well-known cause of false-negative studies (2). If spatial resolution on MRI could be developed to the extent that microcalcifications were included in the data acquired during MRI, this would represent a significant advance in MRI imaging of breast disease. The ability to image such fine detail has been beyond the capabilities of MRI but has been one of the goals of improved MRI technology. Higher strength magnets have been incorporated into clinical MRI to achieve improved of spatial resolution, among other goals. This has led to the progressive increase in magnet strength from early equipment using 0.5 Tesla magnets to current technology incorporating 3.0 Tesla magnets. Although limited by its single-slice application in this report, HiSS imaging of specific lesions within the breast might improve diagnostic accuracy. As an isolated MRI technique eliminating the need to administer contrast, HiSS has the obvious limitation of sacrificing kinetic data. There is little doubt that as spatial resolution has improved and the value of lesion geometry in MRI diagnosis of breast disease has increased, the importance of lesion kinetics in diagnosis has waned. Washout remains a valuable indicator of malignancy, but even progressively enhancing lesions have been described as cancer, particularly ductal carcinoma in situ (3). Because computer-assisted detection (CAD) and diagnosis are based on kinetics, using CAD is not possible with HiSS imaging. Subtraction images are also contrast based and cannot be obtained with HiSS imaging. Many radiologists use these images to interpret MRI; if they were not generated, breast MRI interpretation would become radically different for these radiologists. The technology reported in this study has the technical limitations of being acquired only in a single section. Its authors report that its use to perform a full bilateral breast examination would require about 10 minutes. In its current incarnation, HiSS might be most important as an additional tool to increase data available from MRI to improve diagnostic specificity. Other tools, including spectroscopy and diffusionweighted imaging, open the possibility of improved diagnostic accuracy, diminishing the need to obtain tissue from benign lesions to confirm that they are not clinically important 1465
DERSHAW
(4,5). As other breast imaging techniques have demonstrated, improved spatial resolution—as well as the ability of HiSS to eliminate contrast-induced artifact—offers another tool to improve the specificity of the diagnosis of lesions within the breast. The resultant decrease in cost and anxiety associated with breast cancer screening and diagnosis conveys additional benefit. The automated MRI, performed by the technologist and delivered in the completed state to the radiologist for interpretation, cannot currently offer these benefits. Some advanced MRI technologies, including HiSS, are only applicable to specified sites within the breast. They are not technologies that can be used to interrogate the entire breast volume. The application of these advanced techniques to further refine the data contained in the breast MRI may require that the physician monitor the study as data are acquired and select which, if any, additional scanning techniques are necessary to maximize information obtained from the study. The future of breast MRI, as hinted at in this study, is still hypothetical. Some important limitations in the data reported by Medved et al should be pointed out. In clinical practice, the pivotal decision made by the breast imager is whether or not to biopsy a lesion. This is based on its likelihood of being malignant, but it is not the same as the decision whether or not a lesion is malignant. Therefore, the construct of Medved’s study does not truly test the clinical value of HiSS. Additionally, the study has compared noncontrast HiSS imaging results to contrast MRI without dynamic data. This potentially underestimates the diagnostic ability of contrast MRI, improving the results for HiSS. Importantly, the HiSS technology is currently applicable only to a single slice and cannot be used to interrogate the entire breast. If and when it can be used to evaluate both breasts during MRI, the time required
1466
Academic Radiology, Vol 18, No 12, December 2011
for the study is about 10 minutes. It is possible that patient motion during this long scanning time could compromise the improvement in spatial resolution. Nonetheless, the usefulness of the MRI technique reported by Medved et al is not in its ability to replace contrast studies that include dynamic information, but in the possibility of adding additional information to the data currently obtained for the detection and diagnosis of breast cancer. It offers the potential to improve the specificity of breast imagers in determining what areas in the breast are malignant, diminishing the need to biopsy benign sites without sacrificing the sensitivity of detecting those that are malignant. It also raises the possibility that imaging technology will become increasingly radiologist dependent—that the full clinical advantage of high resolution anatomic and of functional imaging may require radiologist interpretation of images when they are being acquired so that specific techniques can be applied to maximize the benefits of imaging.
REFERENCES 1. Medved M, Fan X, Abe H, et al. Non-contrast enhanced MRI for evaluation of breast lesions: comparison of non-contrast enhanced high spectral and spatial resolution (HiSS) images vs. contrast enhanced fat-suppressed images. Acad Radiol 2011; 18:1467–1474. 2. Menell J, Morris E, Dershaw D, et al. Determination of presence and extent of pure ductal carcinoma in situ by mammography and MRI. Breast J 2005; 11:382–390. 3. Raza S, Vallejo M, Chikarmane SA, et al. Pure ductal carcinoma in situ: a range of MRI features. AJR Am J Roentgenol 2008; 191:689–699. 4. Bartella L, Morris E, Dershaw D, et al. Proton MR spectroscopy using choline peak as malignancy marker improves positive predictive for breast cancer diagnosis: preliminary study. Radiology 2006; 239:686–692. 5. Woodhams R, Ramadan S, Stanwell P, et al. Diffusion-weighted imaging of the breast: principles and clinical applications. RadioGraphics 2011; 31: 1059–1084.