DOI:10.2214/AJR.05.0572
AJR 2006; 187:W152-W160
© American Roentgen Ray Society
BI-RADS-MRI: A Primer
Basak Erguvan-Dogan1,
Gary J. Whitman1,
Anne C. Kushwaha1,2,
Michael J. Phelps1,3 and
Peter J. Dempsey1
1 Department of Diagnostic Radiology, The University of Texas M. D. Anderson
Cancer Center, 1515 Holcombe Blvd., Unit 1350, Houston, TX 77230.
2 Present address: Southwest Memorial Hospital Breast Center, Houston, TX.
3 Present address: Department of Physiology and Biophysics, Georgetown
University, Washington, DC.
Received April 7, 2005;
accepted after revision June 13, 2005.
Presented as an educational exhibit (EE 111) at the 2005 annual meeting of
the American Roentgen Ray Society, New Orleans, LA.
Address correspondence to B. Erguvan-Dogan
(basakerguvan{at}yahoo.com).
WEB
This a Web exclusive article.
Abstract
OBJECTIVE. Variations in breast MRI techniques and descriptions of
morphologic findings led to the development of a breast MRI lexicon. This
lexicon, the American College of Radiology's BI-RADS-MRI, includes terminology
for describing lesion architecture and enhancement characteristics. We show
the use of these descriptors on breast MR images obtained at our
institution.
CONCLUSION. BI-RADS-MRI is a common language with which to report
MRI findings of studies from different institutions.
Keywords: BI-RADS • breast cancer • dynamic MRI
Introduction
Dynamic contrast-enhanced MRI of the breast is becoming increasingly useful
in the detection, diagnosis, and management of breast cancer. To overcome
difficulties arising from lack of standardization among radiologists in
describing lesions and communicating results to referring physicians, the
American College of Radiology in 2003 developed the BI-RADS-MRI lexicon,
published as a part of the American College of Radiology's Breast Imaging
Reporting and Data System Atlas
[1].
The aim of this pictorial essay is to provide practicing radiologists with
illustrations of the descriptors defined in the BI-RADS-MRI lexicon. For this
purpose, we reviewed breast MR images obtained at a large academic
institution. Technical issues and technical variations were not addressed.
General Principles
For reliable assessment with breast MRI, it is crucial to obtain images
with high temporal and high spatial resolution. In addition, data on
morphologic lesions should be accompanied by kinetic time-intensity
information. Lesion information should include lesion location, described as
the clock-face location of the lesion within the breast and the distance from
the nipple.
Morphologic Assessment of Enhancement
Enhancing lesions are divided into three main categories: focus or foci,
masses, and nonmasslike enhancements.
Focus and Foci
Focus and foci are enhancements measuring less than 5 mm that cannot be
otherwise specified (Figs. 1A
and 1B). Focus or foci are
frequently stable on follow-up images and may result from hormonal
changes.
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Fig. 1A —Focus and foci of enhancement. 49-year-old woman with
palpable abnormality in right breast and radiologic findings suggestive of
fibrocystic disease. Dynamic contrast-enhanced sagittal 3D fast spoiled
gradient-recalled echo image (TR/TE, 7/2; flip angle, 20°; matrix size,
256 x 160; slice thickness, 4 mm; interslice gap, 2 mm; field of view,
20 cm) of left breast with fat suppression shows subcentimeter focus
(arrow) of delayed enhancement in upper aspect of right breast.
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Fig. 1B —Focus and foci of enhancement. 49-year-old woman with
palpable abnormality in right breast and radiologic findings suggestive of
fibrocystic disease. Multiple foci of enhancement (arrows) throughout
right breast. All foci were stable for at least 1.5 years and were considered
benign.
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Masses
A mass is a 3D lesion that occupies a space within the breast. Masses are
described in terms of shape, margin, and internal enhancement
characteristics.
Shape—A mass can be round, oval, lobulated, or irregular
(Figs. 2A,
2B,
2C, and
2D). Lobulated masses have an
undulating contour (Fig. 2C).
Irregular masses (Fig. 2D) have
an uneven shape that cannot be characterized as round, oval, or lobulated.
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Fig. 2A —Mass shape may be defined as round, oval, lobulated, or
irregular. Maximum slope of increase images obtained in first 2 minutes after
contrast injection show malignant masses (arrows) with round
(A), oval (B), lobulated (C), and irregular (D)
shapes. Irregular accompanied by abnormal nipple enhancement and retraction
(arrowhead, D) suggest involvement.
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Fig. 2B —Mass shape may be defined as round, oval, lobulated, or
irregular. Maximum slope of increase images obtained in first 2 minutes after
contrast injection show malignant masses (arrows) with round
(A), oval (B), lobulated (C), and irregular (D)
shapes. Irregular accompanied by abnormal nipple enhancement and retraction
(arrowhead, D) suggest involvement.
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Fig. 2C —Woman with breast cancer. Mass shape may be defined as round,
oval, lobulated, or irregular. Maximum slope of increase images obtained in
first 2 minutes after contrast injection show malignant masses
(arrows) with round (A), oval (B), lobulated
(C), and irregular (D) shapes. Irregular accompanied by abnormal
nipple enhancement and retraction (arrowhead, D) suggest
involvement.
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Fig. 2D —Woman with breast cancer. Mass shape may be defined as round,
oval, lobulated, or irregular. Maximum slope of increase images obtained in
first 2 minutes after contrast injection show malignant masses
(arrows) with round (A), oval (B), lobulated
(C), and irregular (D) shapes. Irregular accompanied by abnormal
nipple enhancement and retraction (arrowhead, D) suggest
involvement.
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Margin—Margins can be described as smooth, irregular, or
spiculated (Figs. 3A,
3B, and
3C). Spiculated margins
frequently are a feature of malignant breast lesions and radial scars
[2].
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Fig. 3A —Mass margins can be defined as smooth, irregular, or
spiculated. Sagittal 3D fast spoiled gradient-recalled echo (3D FSPGR) image
of woman shows oval mass with early peripheral enhancement and smooth margins
(arrow) in central aspect of breast. Mass contains central unenhanced
area (asterisk) representing necrosis.
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Internal enhancement characteristics— Enhancement patterns
of masses have been divided into the following six types:
Homogeneous enhancement is uniform and confluent enhancement throughout the
mass (Fig. 4A).
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Fig. 4A —Internal enhancement characteristics of masses. Homogeneous
enhancement in 32-year-old woman with peripheral T-cell lymphoma involving
right breast. Sagittal maximum slope of increase image shows oval,
homogeneously enhanced mass (arrow) with smooth borders in posterior
central right aspect of breast representing lymphomatous involvement.
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Heterogeneous enhancement is nonuniform enhancement that shows variations
within the mass (Fig. 4B).
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Fig. 4B —Internal enhancement characteristics of masses. Heterogeneous
enhancement. Sagittal maximum slope of increase image shows irregular borders
and heterogeneous internal enhancement at 12-o'clock position. Histopathologic
evaluation revealed invasive ductal cancer.
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Rim enhancement is enhancement mainly concentrated at the periphery of the
mass. Rim thickness is not well defined. This type of enhancement is most
frequently a feature of high-grade invasive ductal cancer
[3,
4], fat necrosis, and cysts
with inflammation (Fig.
4C).
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Fig. 4C —Internal enhancement characteristics of masses. Rim
enhancement. Sagittal 3D fast spoiled gradient-recalled echo image shows two
smooth, round masses (arrows) with rim enhancement in central
posterior aspect of breast of patient with multicentric breast cancer.
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Fig. 4D —Internal enhancement characteristics of masses. Dark internal
septations. Sagittal maximum slope of increase image shows smooth, oval mass
(arrow) with hypointense central septations suggestive of
fibroadenoma.
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Fig. 4E —Internal enhancement characteristics of masses. Central
enhanced nidus (arrows) and enhanced internal septum
(arrowhead, E). Pathologic assessment of both lesions revealed
invasive high-grade ductal carcinoma.
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Fig. 4F —Internal enhancement characteristics of masses. Central
enhanced nidus (arrows) and enhanced internal septum
(arrowhead, E). Pathologic assessment of both lesions revealed
invasive high-grade ductal carcinoma.
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Dark internal septations not enhanced within an enhanced lesion are typical
of fibroadenomas, especially when the lesion has smooth or lobulated borders
[5]
(Fig. 4D).
Enhanced internal septations are usually a feature of malignant lesions
(Fig. 4E).
Central enhancement is enhancement of a nidus within a mass that is usually
more pronounced than the rest of the enhanced mass. Central enhancement has
been associated with high-grade ductal cancer and vascular breast tumors
[3] (Figs.
4E and
4F).
Nonmasslike Enhancements
A nonmasslike enhancement is an area of enhancement that does not belong to
a 3D mass or have distinct mass characteristics. Features of nonmasslike
enhancement are categorized by distribution, internal enhancement pattern, and
symmetric or asymmetric enhancement. Assessment of symmetric or asymmetric
enhancement should be reserved for bilateral MRI studies only.
Distribution—A focal area is enhancement occupying less than
25% of the volume of a breast quadrant that has fat or normal glandular tissue
between abnormally enhanced components. This type of enhancement usually
manifests as clumped, irregular contrast enhancement
(Fig. 5A).
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Fig. 5A —Nonmasslike enhancements. Woman with focal, clumped,
nonmasslike enhancement (arrowheads) in upper and lower outer aspects
of left breast representing multicentric ductal cancer. Lesions significantly
decreased in size after neoadjuvant chemotherapy.
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Fig. 5B —Nonmasslike enhancements. Maximum slope of increase image
obtained in first 2 minutes after contrast injection shows ductal enhancement
(arrows) in upper aspect of right breast. Pathologic result was
invasive ductal carcinoma.
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Fig. 5C —Nonmasslike enhancements. Segmental enhancement
(arrows) in lower outer aspect of right breast as shown on sagittal
early contrast-enhanced subtraction image. Pathologic result was invasive
ductal carcinoma with extensive intraductal component.
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Fig. 5D —Nonmasslike enhancements. Regional enhancement. Woman with
locally advanced breast tumor (arrows) in right breast involving
upper outer region of breast. Enhancement diminished on subsequent MR images
obtained over course of neoadjuvant chemotherapy, demonstrating response to
therapy (not shown).
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Fig. 6A —Internal enhancement characteristics of nonmasslike
enhancements. Sagittal (A) contrast-enhanced dynamic, reconstructed
axial (B), and coronal (C) images show clumped enhancement
(arrowheads) in upper outer aspect of left breast with right locally
advanced breast cancer.
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Fig. 6B —Internal enhancement characteristics of nonmasslike
enhancements. Sagittal (A) contrast-enhanced dynamic, reconstructed
axial (B), and coronal (C) images show clumped enhancement
(arrowheads) in upper outer aspect of left breast with right locally
advanced breast cancer.
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Fig. 6C —Internal enhancement characteristics of nonmasslike
enhancements. Sagittal (A) contrast-enhanced dynamic, reconstructed
axial (B), and coronal (C) images show clumped enhancement
(arrowheads) in upper outer aspect of left breast with right locally
advanced breast cancer.
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Fig. 6D —Internal enhancement characteristics of nonmasslike
enhancements. Dynamic time-intensity curve shows initial rapid upslope
followed by continuous increase in signal intensity. MR-guided biopsy revealed
fibrocystic disease.
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Fig. 6E —Internal enhancement characteristics of nonmasslike
enhancements. Stippled or punctate enhancement representing hormonal changes
in premenopausal woman. Follow-up MR study showed stability of these lesions
(not shown).
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Linear enhancement is a sheet of enhancement that does not conform to the
shape of a ductal system.
Ductal enhancement conforms to the shape of a ductal system, pointing
toward the nipple (Fig.
5B).
Segmental enhancement is conical and probably represents one or more ductal
systems (Fig. 5C). Ductal and
segmental distribution of enhancement may be associated with in situ ductal
cancer or invasive ductal cancer, atypical ductal hyperplasia, papillary
neoplasms, or sclerosing adenosis
[6].
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Fig. 7B —Associated findings. Unenhanced high signal intensity in
ducts. Sagittal T2 (B) and axial T1 (C) images show subareolar
dilated ducts (arrows) with areas of high signal intensity
(asterisks). These areas represent benign ectatic ducts containing
secretion with increased protein content.
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Fig. 7C —Associated findings. Unenhanced high signal intensity in
ducts. Sagittal T2 (B) and axial T1 (C) images show subareolar
dilated ducts (arrows) with areas of high signal intensity
(asterisks). These areas represent benign ectatic ducts containing
secretion with increased protein content.
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Fig. 7D —Associated findings. MR image of right breast after right
segmentectomy for invasive ductal cancer shows abnormal signal voids
(arrows) that denotes surgical clips. Deformity and skin thickening
(arrowheads) due to surgery and radiation therapy are evident.
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Regional enhancement is geographic enhancement involving one or more
segments of the breast. A specific ductal or segmental configuration cannot be
discerned (Fig. 5D).
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Fig. 8 —Kinetic curve assessment. Curve interpretation is composed of
two sections: I, Initial upslope of curve can be slow (1), medium (2), or
rapid (3). This period is first 2 minutes of dynamic scan or until first
change in curve, depending on dynamic parameters used. II, Delayed phase
comprises period after first 2 minutes or until curve starts to change.
Continued increase in enhancement is persistent pattern; steady leveling in
enhancement is plateau pattern; and decrease in signal intensity is washout
pattern. Washout pattern and plateau pattern occurring early in dynamic study
are more likely to be associated with malignancy, whereas persistent pattern
is usually detected with benign lesions, such as fibroadenoma, radial scars,
and lesions associated with hormonal changes.
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Multiple regions of enhancement are distributed in several areas of the
breast.
Diffuse enhancement is uniform enhancement of the entire parenchyma of the
breast, usually associated with benign processes or normal fibroglandular
tissue.
Internal enhancement pattern—The internal enhancement
patterns are homogeneous, heterogeneous, clumped (Figs.
6A,
6B,
6C, and
6D), stippled or punctate
(Fig. 6E), and reticular or
dendritic. In the reticular or dendritic pattern, the normal fat-glandular
tissue interface is lost. This finding is usually associated with inflammatory
breast cancer or lymphatic involvement
(Fig. 7A).
Associated Findings
Associated findings with or without enhancement should be noted (Figs.
7A,
7B,
7C, and
7D). These findings include
nipple retraction or inversion, skin retraction, skin thickening, skin
invasion, pectoralis muscle or chest wall invasion, high signal intensity in
ducts on unenhanced images, abnormal signal void, hematoma, edema,
lymphadenopathy, and cysts.
Kinetic Curve Assessment
The most suspicious curve pattern derived from the fastest-enhancing part
of a lesion is chosen to describe the enhancement curve. The initial
enhancement phase—enhancement within the first 2 minutes after contrast
injection or until the curve starts to change—is described as slow,
medium, or rapid. The delayed phase is described as persistent, plateau, or
washout (Fig. 8). Lesions with
rapid or medium initial enhancement followed by a delayed phase plateau or
washout have a positive predictive value of 77% for malignancy
[7].
Conclusion
The American College of Radiology's BI-RADS-MRI lexicon has overcome many
issues regarding standardization of lesion descriptions. Part of the lexicon
is a reporting system similar to that used in mammography and involves the
overall impression the radiologist has derived from these descriptors.
Increased use of the American College of Radiology's BI-RADS-MRI lexicon will
increase the accuracy of interpretation of breast MRI images obtained at
institutions worldwide.
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Abstract
Introduction
