Mr Bi-Rads Lexicon



Mr Bi-Rads Lexicon


Sughra Raza, MD










Sagittal T1WI C+ FS MR in a 65 year old with a mass on screening mammogram shows an oval mass with spiculated margins and thick rim enhancement image (BI-RADS 4C). US-guided CNB revealed IDC and DCIS.






Sagittal T1WI C+ FS MR of the opposite breast in the same patient shows unexpected ductal, clumped NMLE image (BI-RADS 4B). MR-guided CNB showed IDLC.


TERMINOLOGY


Abbreviations



  • Breast imaging reporting and data system for magnetic resonance imaging (BI-RADS® MRI)



    • Published by American College of Radiology (ACR); terms may undergo revision


  • Maximum intensity projections (MIP)



    • 3D reconstruction of brightest pixels from 3D post-contrast subtraction data


  • Computer-aided detection (CAD)



    • Computer-assisted parametric mapping


  • Signal intensity (SI)


Definitions



  • Standardized terminology developed by subcommittee of ACR



    • Terms parallel BI-RADS: Mammography and BI-RADS: US when possible


    • Lexicon to describe findings on breast MR



      • Lesion type, architecture, and location


      • Kinetics: Initial and delayed phase


      • Associated findings: Nipple, skin, axilla, chest wall


      • Final assessment and management recommendations


      • Extramammary findings (e.g., hepatic, pulmonary)


  • Focus: Punctate, nonspecific enhancement, too small to characterize morphologically (usually < 5 mm)


  • Mass: Enhancing 3D space-occupying lesion with discrete margins


  • Non-mass-like enhancement (NMLE): Area of enhancement distinct from surrounding parenchyma; not space-occupying mass



    • Usually has interspersed fat or normal tissue


  • Kinetics: Signal-intensity curves based on initial and delayed-phase enhancement over time



    • Sensitivity threshold (e.g., 50%, 60%, 100% increase in signal intensity in 1st 90 seconds) determines whether or not color is assigned


    • Specific color assignment is based on delayed-phase behavior (persistent, plateau, washout)


MR FEATURES & INTERPRETATION Imaging Protocols



  • Magnet field strength of at least 1.5 T


  • Dedicated breast coil


  • Sequences



    • Typically: T1W image; T2W FS image (or STIR); dynamic pre- and post-contrast 3D SPGR FS


  • Contrast: 0.1 mmoL/kg Gadolinium-based contrast via power injector


  • Post-processing: Subtraction series, MIPs, ± use of CAD


Imaging Pitfalls



  • Limitations of examination



    • Confirm successful contrast administration (e.g., heart, great vessels, liver enhancement)


    • Hormonal influences: Significant variation can be seen in parenchymal enhancement in premenopausal women



      • Schedule in days 7-14 of menstrual cycle when possible: ↓ parenchymal enhancement, false positives


    • Larger breasts: Inhomogeneous fat saturation; artifacts from breast touching coil or table surface


Exam Interpretation



  • Interpretation informed by exam indication, history, and correlative imaging findings



    • Prior biopsies, risk factors, ± symptoms


    • Compare to recent mammography, US, and MR


  • Lesion location



    • Quadrant, subareolar, central, axillary tail


    • Distance from nipple, skin, or chest wall (in cm) as appropriate


    • Table position (e.g., R72) &/or series/slice location where finding best seen


  • Background enhancement



    • Minimal, mild, moderate marked


    • Moderate background enhancement may obscure detection of small masses


    • Parenchyma usually slower to enhance than cancer



      • Early imaging (within 1-2 minutes) after contrast injection is therefore important



Mass Shape



  • Round/spherical; oval/elliptical


  • Lobulated: Undulating contour, scalloped


  • Irregular: Uneven shape


Mass Margin



  • Smooth: Circumscribed, 17-44% malignant when solitary



    • Resolution of ˜ 1 mm may be insufficient to identify subtle spiculation


  • Irregular: Neither smooth nor spiculated, may be ill defined or indistinct; 22-39% malignant


  • Spiculated: Radiating lines from margin, 80-91% malignant


Mass Internal Enhancement Characteristics



  • Homogeneous: Confluent, uniform enhancement


  • Heterogeneous: Nonuniform enhancement


  • Rim enhancement: Greater at periphery, 40-84% malignant



    • Thick, irregular rim, rapid enhancement, and washout kinetics favor malignancy


  • Enhancing internal septations: PPV > 95%


  • Central enhancement: Greater in center of mass


  • Dark internal septations: Nonenhancing internal septations



    • High NPV; often fibroadenomas


Non-Mass-Like Enhancement (NMLE) Distribution



  • Focal area: < 25% of quadrant in confined area



    • Contains interspersed fat or normal glandular tissue


  • Linear/ductal: In a line, pointing to nipple; often branching, conforming to duct



    • Linear often used in place of ductal


    • 20-26% malignant, usually clumped internal enhancement


  • Segmental: Triangular region or cone with apex pointing to nipple



    • Suggests duct and its branches


    • Most common NMLE reported in DCIS at 40-55%


  • Regional: Geographic, ≥ 25% of quadrant



    • Symmetric regional NMLE favors benign etiology


    • At edges of parenchyma: May be “inflow”


    • Cyclic dependency if normal variant


    • When isolated and biopsied, 47-50% malignant


  • Multiple regions: ≥ 2 regions, patchy


  • Diffuse: Uniform, even throughout breast



    • Distinguish diffuse NMLE from background enhancement


NMLE Internal Enhancement



  • Heterogeneous


  • Homogeneous


  • Clumped: Cobblestone-like, confluent in areas, “bunch of grapes” or “string of pearls” appearance



    • Favors DCIS, especially in linear or segmental distribution


  • Stippled/punctate: Round, tiny, dot-like


  • Reticular/dendritic: Strand-like



    • Can be seen with inflammatory carcinoma


NMLE Symmetry



  • Symmetric: Mirror image, both breasts


  • Asymmetric: More in 1 breast than other


Kinetics



  • Sample and report ROIs of most rapidly enhancing ± most suspicious areas in lesion


  • Initial phase: Change in SI within 1st 2 minutes of injection (before curve changes)



    • Slow: < 60% increase in SI


    • Medium: 60-100% increase in SI


    • Rapid: > 100% increase in SI


  • Delayed phase: SI over time after 1st 2 minutes



    • Persistent (type 1): Progressive, continued increase in signal over time


    • Plateau (type 2): SI does not change over time after initial rise; flat (± 10%)


    • Washout (type 3): SI decreases after peaking



      • Cancers more likely to show washout or plateau kinetics



Associated Findings



  • Nipple retraction or inversion, pre-contrast high duct signal, skin retraction, skin thickening (> 2 mm), edema, abnormal signal void (artifacts), cyst(s)


  • Lymphadenopathy: Enlarged, rounded nodes, eccentrically thickened cortex, loss of fatty hila



    • Encourage positioning to include axilla


  • Pectoralis muscle or chest wall invasion: Must see extension of suspicious enhancement into pectoralis, intercostal muscle(s), or rib(s); not sufficient to abut


  • Hematoma/blood: Bright signal on pre-contrast T1W image


  • Cyst: Circumscribed round or oval fluid-filled mass, imperceptible wall, bright on T2W FS image


Final Assessments, Recommendations



  • Should reflect the most suspicious findings in each breast


  • 0: Incomplete, additional evaluation needed


  • 1: Negative, no lesion found, routine follow-up


  • 2: Benign finding, routine follow-up


  • 3: Probably benign, short interval follow-up



    • 6-month follow-up



      • 2-10% risk of malignancy across multiple series, varying criteria


      • Concept requires further validation for MR


      • Consider circumstances of exam: Higher risk of malignancy if satellite to known cancer; follow-up problematic due to planned pregnancy or relocation


    • Proposed criteria for BI-RADS 3 (ACRIN 6666)



      • 1-2 smooth, oval mass(es), persistent or plateau kinetics, not suspicious on mammography or US


      • Solitary focus, persistent or plateau kinetics (1/37 [3%] malignant in 1 series)


      • Patchy regional enhancement, persistent kinetics, no US correlate


      • Multiple, bilateral similar findings favor benign


    • Optional 3A: Possibly hormonal, follow-up at different time in cycle, 2-6 weeks


  • 4: Suspicious abnormality, optional subdivision



    • 4A: Low suspicion of malignancy, biopsy


    • 4B: Intermediate suspicion of malignancy, biopsy


    • 4C: Moderate suspicion of malignancy, biopsy


  • 5: Highly suggestive of malignancy, take appropriate action (usually biopsy)


  • 6: Recent biopsy-proven malignancy; ongoing treatment



    • Exam for local extent of disease


    • Following neoadjuvant chemotherapy



REFERENCES

1. Schnall MD et al: Diagnostic architectural and dynamic features at breast MR imaging: multicenter study. Radiology. 238(1):42-53, 2006

2. Morakkabati-Spitz N et al: Diagnostic usefulness of segmental and linear enhancement in dynamic breast MRI. Eur Radiol. 15(9):2010-7, 2005

3. Kriege M et al: Efficacy of MRI and mammography for breast-cancer screening in women with a familial or genetic predisposition. N Engl J Med. 351(5):427-37, 2004

4. Warner E et al: Surveillance of BRCA1 and BRCA2 mutation carriers with magnetic resonance imaging, ultrasound, mammography, and clinical breast examination. JAMA. 292(11):1317-25, 2004

5. Ikeda DM et al: Breast Imaging Reporting and Data System, BI-RADS: Magnetic Resonance Imaging (BI-RADS®: MRI), 1st ed. Reston, American College of Radiology, 2003

6. Liberman L et al: Ductal enhancement on MR imaging of the breast. AJR Am J Roentgenol. 181(2):519-25, 2003

7. Liberman L et al: Probably benign lesions at breast magnetic resonance imaging: preliminary experience in high-risk women. Cancer. 98(2):377-88, 2003

8. Liberman L et al: Breast lesions detected on MR imaging: features and positive predictive value. AJR Am J Roentgenol. 179(1):171-8, 2002

9. Nunes LW et al: Optimal post-contrast timing of breast MR image acquisition for architectural feature analysis. J Magn Reson Imaging. 16(1):42-50, 2002

10. Ikeda DM et al: Development, standardization, and testing of a lexicon for reporting contrast-enhanced breast magnetic resonance imaging studies. J Magn Reson Imaging. 13(6):889-95, 2001

11. Schnall MD et al: A combined architectural and kinetic interpretation model for breast MR images. Acad Radiol. 8(7):591-7, 2001






Image Gallery









Axial T1WI C+ FS MR with color overlay in an asymptomatic 33 yo woman, whose sister had breast cancer at 39, shows an 8 mm oval, smooth mass with rapid initial enhancement & washout kinetics image.






Sagittal T1W FS MR C+ delayed image shows washout kinetics image. On T2W image (not shown) the mass demonstrated high signal (BI-RADS 4B). MR-guided CNB showed a grade II IDC.






(Left) Sagittal T1WI C+ FS MR in a 50 yo woman with family history of breast cancer shows a < 5 mm focus image. A few other small foci were also present; mammograms had been negative for 7 years. (Right) Sagittal T1WI C+ FS MR with color overlay (same patient) shows washout kinetics image. Follow-up MR at 6 months was recommended (BI-RADS 3). Despite the size (< 5 mm), this is a mass with irregular margins &, in retrospect, should have been biopsied.






(Left) Sagittal T1WI C+ FS MR in the same patient at 6-month follow-up shows increased lesion size, now reported as a 5.5 mm mass with more intense enhancement image and irregular margins. (Right) Sagittal T1WI C+ FS MR image from the same exam shows washout kinetics only in the small mass image (BI-RADS 4B). Biopsy showed an ER(+), PR(+), Her-2/neu(-), grade I IDC and DCIS. She was treated with lumpectomy, XRT, and tamoxifen.






(Left) Axial T1WI C+ FS MR of a 48-year-old woman with history of right breast ADH on excisional biopsy shows a solitary 3 mm focus in the medial posterior left breast image. (Right) Sagittal T1WI C+ FS MR delayed image of the same patient shows plateau kinetics image (BI-RADS 4B). Correlative US showed a 4 mm mass and US-guided CNB revealed an ER(+), PR(+), Her-2/neu(-), grade II IDC with DCIS.







(Left) Axial T1WI C+ FS MR in a 71-year-old woman with a new palpable lump in the upper right breast, corresponding architectural distortion on mammogram, and shadowing mass on US shows nonenhancing distortion image. This patient had a remote history of excisional biopsy near this site. (Right) Sagittal T1W FS MR C+ delayed image of the same case shows the focal architectural distortion without appreciable enhancement image.

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Sep 18, 2016 | Posted by in OBSTETRICS & GYNAECOLOGY IMAGING | Comments Off on Mr Bi-Rads Lexicon
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