Minimum Requirements for Breast MRI Examinations
Recommendations for the performance of breast MRI examinations, based on a consensus of the members of the breast diagnostics working group of the German Association of Radiology in 2005, should be seen as the minimum requirements that need to be fulfilled to perform high-quality breast MRI examinations (Table 19.1).
TABLE 19.1 Minimum quality requirements for breast MRIa
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Technique |
Field strength |
1–1.5 T |
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|
Surface coil |
Bilateral |
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|
Breast fixation |
Adequate compression (dedicated compression device, sports brassiere, cushions, or the like) |
|
Methods |
Time of examination |
2nd (3rd) week of menstrual cycle (exception: preoperative staging) |
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|
Hormonal influence |
If disturbing enhancement is present: HRT should be discontinued for 4–6 weeks before repeat examination |
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|
Influence of surgery |
Time between surgery and MRI: > 6 months |
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|
|
Time between BCS and radiation therapy and MRI: > 12 months |
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|
Technique |
2D or 3D |
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|
Orientation |
Axial or coronal |
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|
Sequences |
T1w GE, T2w (SE, TSE, IR) |
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|
Dynamics |
First measurement before CM administration; further measurements after CM administration over > 6 minutes |
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|
Paramagnetic contrast medium |
0.1 mmol/kg BW for 2D examination |
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0.1–0.2 mmol/kg BW for 3D examination |
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Contrast injection |
Cubital vein, flow ~2–3 mL/s, followed by injection of at least 20 mL NaCl |
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|
Spatial resolution |
≤4 mm/slice |
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|
Temporal resolution |
< 2.5 min/sequence |
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|
Examination time |
At least 6 minutes after CM administration |
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|
FOV |
300–350 mm |
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Matrix |
At least 256 × 256 |
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|
TR |
Typical settings for 2D or 3D examination |
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|
TE |
Appropriate echo times for 1.0 and 1.5 T in-phase imaging |
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|
Postprocessing |
Subtraction (early—precontrast is obligatory) |
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|
Examination evaluation |
Morphological criteria, dynamic criteria, multimodal evaluation, T2w image information |
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|
Documentation (obligatory) |
T1w precontrast (complete) |
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T1w early postcontrast (complete) |
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|
|
Early subtraction (complete) |
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|
|
TIC analysis + T2w (findings-oriented) |
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|
Presentation |
Hardcopy (film or paper) |
Quality Check in Breast MRI
After an examination has been performed, the following possible errors should be ruled out:
Are both breasts completely imaged? (Possibilities of error on pp. 47 and 48).
Did contrast material reach the breasts? (Reference points on p. 49).
Are there motion artifacts? (Determine the MRI artifact level, see pp. 50–52.) If artifacts are pronounced (MRI artifact level III or IV), then examination should be repeated.
How great is the parenchymal enhancement in the early subtraction images? (Determine MRI density, see p. 69). Should an earliest subtraction be performed? If parenchymal MRI density is high, then a repeat examination in an appropriate cycle phase or, if applicable, after discontinuing hormonal replacement therapy should be considered.
Are the ROIs correctly placed? (Possibilities of error on p. 57.)
Written Report
The written breast MRI report should include a short reference to results of earlier examination results, any specific questions to be answered, and any relevant patient history information. This should be followed by information on the techniques used, sequences, and orientations, as well as the amount of contrast material administered.
The descriptive section should include details of apparent changes in the T1w precontrast and T2w images, and should especially provide information on signal changes after intravenous contrast administration. The evaluation of breast MRI findings into categories 1 to 5 should be performed for each side separately in accordance with the ACR BI-RADS Lexicon. Furthermore, correlation of the breast MRI findings with clinical, mammographic, and/or ultrasonographic findings (if possible) should be made, and recommendations for the further course of action expressed.
Example of Written Report of Unremarkable Breast MRI Findings
Indication: Early breast cancer detection, reduced sensitivity of x-ray mammography and breast ultrasound. Mammography: ACR density IV, BI-RADS right 1/left 1. Breast US: Bilateral bland cysts, US BI-RADS right 2/left 2.
Risk profile: Increased familial risk (breast cancer detected in mother at age 67 years). Not considered high-risk.
MRI technique: Examination with HR technique (matrix 512 × 512) using a 1.5 T system and dedicated open breast surface coil. Acquisition of 46 IR T2w axial slice images. In identical slice position acquisition of 46 axial slice images once before and 5 times after IV administration of 0.1 mmol Gd-DTPA/kg BW. Image postprocessing for generation of subtraction slice images, TICs in appropriate regions, and presentation as MIP.
MRI findings: Unremarkable findings in the T1w precontrast images. No architectural distortions. In the IR T2w images depiction of multiple simple cysts up to 10 mm in diameter. After contrast administration, mild bilateral parenchymal enhancement (MRI density II) with the exception of the cystic spaces. No motion artifacts (MRI artifact level I). No areas of focal enhancement, no hypervascularized mass lesions, no nonmasslike areas of enhancement in either breast. MRI BI-RADS right 1/left 1.
Final evaluation: The present breast MRI examination shows no signs indicating the presence of a malignant breast tumor in either breast. Taking clinical, mammographic, and breast ultrasound findings into consideration results in the cumulative BI-RADS right 2 (cysts)/left 2 (cysts). The next examination for early breast cancer detection is recommended at a routine interval of 1 to 2 years.
Example of Written Report of Breast MRI Performed for Preoperative Local Staging
Indication: Preoperative local staging after histological verification of a breast carcinoma with a diameter of 1 cm in the upper outer quadrant of the left breast. Mammography: ACR density III, BI-RADS right 1/left 5. US BI-RADS right 1/left 5. Cumulative BI-RADS right 1/left 6.
Personal history: Diagnostic excision in the right breast 8 years ago (benign lesion).
Risk profile: No increased familial disposition.
MRI technique: Examination with HR technique (matrix 512 × 512) using a 1.5 T system and dedicated open breast surface coil. Acquisition of 46 IR T2w axial slice images. In identical slice position acquisition of 46 axial slice images once before and 5 times after IV administration of 0.1 mmol Gd-DTPA/kg BW. Image postprocessing for generation of subtraction slice images, TICs in appropriate regions, and presentation as MIP.
MRI findings: In the T1w precontrast images susceptibility artifacts are seen in the upper outer quadrant of the right breast after diagnostic excision. Unremarkable findings in the left breast. In the IR T2w images depiction of multiple simple cysts up to 3 mm in diameter. After contrast administration, no early enhancement in the right breast. In the upper outer quadrant of the left breast there is a hypervascularized, ill-circumscribed mass lesion with a diameter of 10 mm which displays an increased marginal enhancement (rim sign). TICs in appropriate ROIs show a rapid initial signal increase (> 100%) and postinitial washout. MRI score: 7 points. Additional 15 mm linear enhancement originating from this index tumor and nearly reaching the nipple. High parenchymal transparency (MRI density I). No motion artifacts (MRI artifact level I). No pathologically enlarged axillary lymph nodes in the T1w and T2w images. MRI BI-RADS right 1/left 5.
Final evaluation: Confirmation of the histologically verified carcinoma in the upper outer quadrant of the left breast (diameter 1 cm). Additional findings indicative of an EIC between the primary tumor and the breast nipple. No indication of multifocality or multicentricity. No depiction of enlarged locoregional lymph nodes. On the basis of left breast image results we recommend segment resection and sentinel lymph node biopsy. The contralateral right breast is unremarkable. Cumulative BI-RADS right 1/left 6 (plus signs of EIC).
