Breast Imaging: A Core Review (8 page)

Diagnostic abnormal interpretation rate = (Category 4 and 5 cases based on diagnostic workup)/(Total number of diagnostic mammograms).

28b
 
Answer C.
 Cancer detection rate is the number of cancers correctly detected at mammography per 1,000 patients examined at mammography.

Cancer detection rate = Positive biopsies/Total number of screening mammograms = 30/5,000 = 0.006 = 6/1,000.

Reference: American College of Radiology (ACR).
ACR BI-RADS—Mammography. In: ACR Breast Imaging Reporting and Data System, Breast Imaging Atlas
. 4th ed. Reston, VA: American College of Radiology; 2003:231.

29
 
Answer C.
 This image demonstrates susceptibility artifact on the right breast due to metal on the patient’s skin. A mammographic BB marker left on the patient’s skin prior to the MRI caused the artifact. The BB has a metallic component, which can cause image artifacts manifesting as warped images, signal voids, and signal flare. The artifact can vary based on which type of sequence is performed. Metallic artifacts manifest as signal voids on gradient echo sequences. On spin echo sequences, a signal flare component may be seen in addition to the signal void. Susceptibility artifact is most commonly seen in breast MRI interpretation as a result of breast biopsy markers or surgical clips. Answer A is wrong because chemical shift artifact is an artifact that results from the different resonances of the hydrogen in fat and water. It is most commonly seen in non–fat-suppressed sequences (e.g., non–fat-suppressed T1-weighted) and results in signal void or bright signal at a fat–water interface. Answer B is wrong because wrap or aliasing artifact occurs when tissue extends beyond the field of view (FOV), causing signal from tissues outside the FOV to be superimposed on structures within the FOV. It occurs in the phase encoding direction. This artifact can be seen with patients’ arms in breast MRI practice. Answer D is wrong. There is no significant motion on this image. Motion artifact is one of the most commonly encountered artifacts affecting breast MRI. Motion can arise from patient motion or cardiac, respiratory, or great vessel motion. All motions propagate in the phase encoding direction despite the direction of the motion. Phase encoding direction should be left to right for axial sequences and superior to inferior for sagittal sequences to reduce the effect of cardiac and respiratory motion on the breasts.

References: Genson CC, Blane CE, Helvie MA, et al. Effects on breast MRI of artifacts caused by metallic tissue marker clips.
AJR Am J Roentgenol
2007;188(2):372–376.
Harvey JA, Hendrick E, Coll JM, et al. Breast MR imaging artifacts: How to recognize and fix them.
Radiographics
2007;27:S131–S145.
Hendrick RE.
Breast MRI: Fundamentals and Technical Aspects
. New York, NY: Springer; 2008: 187–207.

30
 
Answer C.
 Correct film labeling should include all of the following: the patient’s first and last name as well as unique patient identification number, name and address of the facility, mammography unit, date of the exam, view and laterality placed near the axilla, Arabic number indicating the cassette, and technologist’s initials.

Reference: Ikeda D.
Breast Imaging: The Requisites
. 2nd ed. St. Louis, MO: Elsevier Mosby; 2011:7, 12.

31
 
Answer B.
 A BI-RADS 3 category finding should have a less than 2% chance of malignancy. The finding is not expected to change over the time interval of the BI-RADS 3 follow-up. BI-RADS 3 findings include the noncalcified circumscribed solid mass, the focal asymmetry, and the cluster of round and punctate calcifications.

Reference: American College of Radiology (ACR). ACR BI-RADS—Mammography. In:
ACR Breast Imaging Reporting and Data System, Breast Imaging Atlas
. 4th ed. Reston, VA: American College of Radiology; 2003:194–197.

32
 
Answer C.
 BI-RADS 5 lesions have a > 95% chance of malignancy. The level of suspicion is high enough in these lesions that they could be taken to surgery without preoperative biopsy; however, current oncologic evaluation may require a tissue biopsy to adequately plan the patient’s treatment course before surgery.

Reference: American College of Radiology (ACR). ACR BI-RADS—Mammography. In:
ACR Breast Imaging Reporting and Data System, Breast Imaging Atlas
. 4th ed. Reston, VA: American College of Radiology; 2003:194–197.

33
 
Answer A.
 Hair artifact is noted on the CC view but is not seen on the MLO view. Hair artifact often creates a swirl pattern on the image. By simply repeating the image, with attention to clearing the hair from the field of view, the artifact will be eliminated.

Reference: Cardenosa G.
Breast Imaging
. Philadelphia, PA: Lippincott Williams & Wilkins; 2004:45–48.

34
 
Answer C.
 A VP shunt catheter is noted on this study. Note that the catheter is seen extending into the abdominal wall on the ML view.

Reference: Chatell T, Shah B. Review of common mammographic artifacts on both digital and analog mammograms.
AJR Am J Roentgenol
2010;194(5 Suppl):A100–A115.

35
 
Answer B.
 The current recommendations of the American Cancer Society and American College of Radiology for screening breast MRI are for women with a high risk of breast cancer, estimated at a > 20% lifetime risk of having the disease, based on multiple different mathematical models outlined in the papers cited below. Other groups for which screening breast MRI is recommended include patients with known genetic mutations, including BRCA-1 and BRCA-2, and a family history that suggests a genetic predisposition (=2 first-degree relatives with breast cancer or a single firstdegree relative with premenopausal breast cancer or a family history of breast and ovarian cancer). There are other cases in which the ACR and ACS do not recommend for or against screening due to limited information including those patients with a 15% to 20% lifetime risk including those with prior personal history of breast cancer, history of ADH or lobular neoplasia, or more limited family histories.

References: Lee CH, Dershaw DD, Kopans D, et al. Breast cancer screening with imaging: Recommendations from the Society of Breast Imaging and the ACR on the use of mammography, breast MRI, breast ultrasound, and other technologies for the detection of clinically occult breast cancer.
J Am Coll Radiol
2010;7(1):18–27.
Saslow D, Boetes C, Burke W, et al. American Cancer Society guidelines for breast screening with MRI as an adjunct to mammography.
CA Cancer J Clin
2007;57(2):75–89.

36
 
Answer D.
 Roller artifact lines coursing longitudinally are seen on the right mediolateral oblique and right craniocaudal views.

Reference: Chatell T, Shah B. Review of common mammographic artifacts on both digital and analog mammograms.
AJR Am J Roentgenol
2010;194(5 Suppl):A100–A115.

37
 
Answer B.
 Estrogen can cause contrast enhancement of benign breast parenchyma in premenopausal females. This enhancement is greatest in weeks 1 and 4 of the cycle, assuming a 4-week cycle. This enhancement can make interpretation of normal background enhancement from pathological enhancement difficult. Physiologic enhancement is the least during the 2nd week; therefore, this is the preferred week to perform breast MRI.

Reference: Morris EA, Liberman L, eds.
Breast MRI: Diagnosis and Intervention
. New York, NY: Springer; 2005:36–38.

38
 
Answer A.
 The 2007 American Cancer Society Guidelines recommend the use of screening MRI in patients with a history of Hodgkin disease, particularly those with a prior history of mantle field radiation. Neurofibromatosis is an incorrect answer. Although there has been a recognized link between neurofibromatosis type 1 and breast carcinoma, current guidelines do not recommend the use of screening MRI in this patient population. The ACS guidelines also recommended the use of screening breast MRI in patients with a 20% to 25% or greater lifetime risk of breast cancer. As such, C would also be an incorrect choice. Heterogeneously dense breasts (>50% breast density) has not been shown to be a clinical indicator of breast cancer risk. Multiple studies have shown, however, that women with >75% breast density have a fivefold increased risk of breast cancer.

References: Saslow D, Boetes C, Burke W, et al. American Cancer Society guidelines for breast screening with MRI as an adjunct to mammography.
CA Cancer J Clin
2007;57:75–89.
Sharif S, Moran A, Huson SM, et al. Women with neurofibromatosis type 1 are at moderately increased risk of developing breast cancer and should be considered for early screening.
J Med
Genet 2007;44(8):481–484.

39
 
Answer D.
 Phantom images should be carried out weekly, after equipment service or whenever image quality problems are suspected. The phantom is evaluated for background density, contrast, uniformity, and number of objects seen. The phantom simulates a 4.0 to 4.5 cm compressed breast with six different fibers, five groups of microcalcifications, and five masses. ACR criteria require a minimum score with visibility of at least four fibers, three microcalcifications, and three masses.

Reference: Kopans DB.
Breast Imaging
. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007:275–277.

40
 
Answer C.
 The MLO view provides the greatest amount of coverage for a single projection. In positioning the patient, care must be taken to make sure the medial breast tissue is not pulled out of the field of view. The medial breast tissue is tethered along the sternum, which can easily slide out of view if proper care is not taken with positioning.

Reference: Kopans DB.
Breast Imaging
. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007: 286–288.

41
 
Answer C.
 T1 without fat saturation is the optimal sequence to identify a fat-containing mass, such as an intramammary lymph node or fat necrosis, which are benign findings; BI-RADS category 2. Answer A is incorrect. A cancer cannot be completely excluded if a mass has hyperintense signal on the T2 sequence. Classically, mucinous variants of ductal carcinoma have been described as having high T2 signal. In addition, invasive breast cancers such as invasive ductal carcinoma not otherwise specified can have high T2 signal. Therefore, hyperintense signal on T2 does not rule out cancer in an enhancing mass. Answer B is incorrect. Breast MRI is optimally performed during week 2 of patients’ menstrual cycles. This timing will minimize proliferative changes of the breast tissue and resultant background enhancement. Answer D is incorrect. A breast-specific coil is the optimal radiofrequency receiver coil for breast MRI. It is the coil best designed to fit the relevant anatomy without including additional tissue. The inclusion of additional tissue will decrease the signal-to-noise ratio in the breasts. In addition, a body coil would compress the breast tissue, limiting visualization and evaluation. Finally, answer E is incorrect. Contrast-enhanced breast MRI for the detection of breast cancer is performed using a gadolinium-based contrast agent via intravenous injection. However, an equivalent dosage of a gadolinium-based contrast agent is not used for all patients. Manufacturers of the gadolinium-based contrast agents recommend a weight-based dosage (such as 0.1 mmol/kg). Larger patients should receive a higher dosage of the contrast agent than smaller patients.

References: Hendrick RE.
Breast MRI Fundamentals and Technical Aspects
. New York, NY: Springer; 2008:34, 35.
Morris EA, Liberman L.
Breast MRI Diagnosis and Intervention
. New York, NY: Springer; 2005:9, 17, 21, 85, 152, 428.
Santamaría G, Velasco M, Bargalló X, et al. Radiologic and pathologic findings in breast tumors with high signal intensity on T2-weighted MR images.
Radiographics
2010;30:533–548.

42a
 
Answer E.
 Fat saturation is important for breast cancer detection on MRI. High signal of fat interferes with the detection of enhancing lesions. MR imaging unit software automatically identifies the water peak as the highest signal peak, and fat is suppressed by applying saturation pulses at a frequency of 3.5 ppm (224 Hz at 1.5 T) below the water peak. To effectively suppress the protons in the fat molecules, the correct range of frequencies must be selected. Sometimes in the presence of an unexpected variation in the magnetic field, there will be protons in fat that are precessing out of the range of frequencies included in the suppression pulse. These protons will not be suppressed, and the fat containing these protons will maintain its brighter signal. This phenomenon results in inhomogeneous suppression of the fat signal within the breast. Inhomogeneous fat saturation is a common problem and cannot be corrected for. However, shimming the magnet (optimizing field homogeneity) of an MR imaging unit can correct some of the artifact.