Breast Sonographic Elastography Using an Advanced Breast Tissue- Specific Imaging Preset

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1 ORIGINAL RESEARCH Breast Sonographic Elastography Using an Advanced Breast Tissue- Specific Imaging Preset Initial Clinical Results Hyun Jin Jung, MD, Soo Yeon Hahn, MD, Hye-Young Choi, MD, Sung Hee Park, MD, Heung Kyu Park, MD Received March 23, 2011, from the Departments of Radiology (H.J.J., S.Y.H., H.-Y.C., S.H.P.) and Surgery (H.K.P.), Gachon University of Medicine and Science, Gachon University Gil Hospital, Incheon, Korea; and Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. Revision requested April 21, Revised manuscript accepted for publication August 30, Address correspondence to Soo Yeon Hahn, MD, Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul , Korea. Abbreviations BI-RADS, Breast Imaging Reporting and Data System; CI, confidence interval; NPV, negative predictive value; PPV, positive predictive value Objectives The purpose of this study was to evaluate the interpretation criteria, such as the size ratio, stain ratio, and elasticity score, and to assess the diagnostic performance of sonographic elastography by using an advanced breast tissue-specific imaging preset compared with that of conventional sonography for the differentiation of benign and malignant breast masses. Methods Conventional sonography and sonographic elastography with the tissuespecific imaging preset were performed in 104 patients (age range, years; mean age, 47.7 years) with 110 breast lesions (67 benign and 43 malignant; mean size, 1.69 cm). The data from the interpretation criteria of sonographic elastography were obtained. The pathologic results from surgical excision or vacuum-assisted removal were used as a reference standard. Results The values for the area under the receiver operating characteristic curve were (95% confidence interval [CI], ) for conventional sonography and (95% CI, ), (95% CI, ), and (95% CI, ) for the strain ratio, size ratio, and elasticity score, respectively. When a strain ratio cutoff point of was used, the sensitivity and specificity were 86.0% and 85.1%. With a best cutoff point for conventional sonography between Breast Imaging Reporting and Data System categories 4A and 4B, the sensitivity and specificity were 93.0% and 83.6%. Conclusions The strain ratio showed the best diagnostic performance among the interpretation criteria for sonographic elastography with the tissue-specific imaging preset. The diagnostic performance was slightly higher for Breast Imaging Reporting and Data System categories than for the strain ratio. However, there was no statistical significance (P =.052). Key Words breast neoplasms; sonographic elastography; tissue characterization E lastography is a dynamic imaging technique that uses sonography to provide an estimate of tissue stiffness by measuring the degree of deformation under the application of an external force. This technique is based on the principle that the soft parts of tissue deform more easily than harder parts of tissue under compression, thus allowing an objective determination of tissue consistency. 1 3 Because breast tissue is soft as well as compressible, and because breast cancer tissue is harder than normal breast tissue, thus leading to a difference in strain, elastography has been studied as a tool for differentiating between benign and malignant breast masses by the American Institute of Ultrasound in Medicine J Ultrasound Med 2012; 31:

2 Sonographic elastography using an advanced breast tissue-specific imaging preset is a new method for tracking tissue deformation requiring virtually no external compression for reproducible strain imaging results. In addition, this technique recommends the strain ratio of a lesion necessary to determine the strain of the lesion and the fat tissue as an objective and constant reference. Recent studies suggest the fat to lesion strain ratio to compare with the surrounding breast tissue to lesion strain ratio. 4 8 However, the strain ratios of these studies were obtained using elastography with the existing freehand technique. The purpose of this study was to evaluate the 3 types of interpretation criteria, including size ratio, stain ratio, and elasticity score, and to assess the diagnostic performance of sonographic elastography with the tissue-specific imaging preset compared with that of conventional sonography for differentiation of benign and malignant breast masses. Materials and Methods Institutional Review Board approval was obtained, and the informed patient consent requirement was waived because the study was retrospective. Patients A retrospective review was performed on 112 breast masses classified as Breast Imaging Reporting and Data System (BI-RADS) categories 3, 4, and 5 from 106 consecutive patients who underwent sonographic elastography and scheduled sonographically guided core biopsies between April and October Breast Imaging Reporting and Data System category 3 lesions were biopsied because the cases were referred from other hospitals or at the request of physicians. Among these 112 lesions, we excluded 2 lesions from patients who did not receive further pathologic confirmation of the lesions at our institution. Thus, we included 110 lesions from 104 patients (age range, years; mean age, 47.7 years). Of these patients, 6 underwent sonographic elastography for 2 separate lesions. Conventional Sonographic Examinations Conventional sonography was performed on 1 of 2 iu22 ultrasound scanners (Phillips Medial Systems, Bothell, WA) equipped with a 5- to 12- or 5- to 17-MHz linear array transducer. All conventional sonographic examinations were performed by 1 of 3 board-certified radiologists specializing in breast imaging before sonographic elastography and sonographically guided core biopsy. Breast lesions on conventional sonography were characterized according to the American College of Radiology BI-RADS classification 9 at the time of the real-time sonographic examinations. All medical records and imaging reports were retrospectively reviewed. Sonographic Elastography After the conventional sonographic examination, sonographic elastography was performed with a 5- to 12-MHz linear array transducer and an iu22 scanner using advanced breast tissue-specific imaging preset. The images from conventional sonography and sonographic elastography were displaced side-by-side as a single image (Figures 1 and 2). A region of interest box was set to include the area from the subcutaneous fat layer to the superficial portion of the pectoralis muscle layer and to focus on the target mass. To obtain the elastographic images, sonographic elastography with the tissue-specific imaging preset requires virtually no external compression. Therefore, the transducer was oriented to face the target area with only light pressure. Real-time monitoring of images and the deformation feedback bar were used to avoid the interruption of color encoding during data acquisition. Interpretation Criteria for Sonographic Elastography At our institution, we record 3 interpretation criteria, size ratio, strain ratio, and elasticity score, for evaluation of sonographic elastography. In this study, we used the recorded data that were determined at the time of sonographic elastography. The size ratios of the breast lesions were calculated as the ratio of the size (diameter) of the area without strain on elastography relative to the size (diameter) of the hypo - echoic area of a lesion on conventional sonography. These ratios were automatically calculated by an embedded software program in the ultrasound unit. Figure 1. Fibroadenoma of the left breast in a 45-year-old woman. Conventional sonography (left) shows a hypoechoic mass with indistinct margins, which was categorized as having a low suspicion of malignancy (category 4A). Sonographic elastography (right) shows no strain in the entire hypoechoic lesion (elasticity score of 4). A size ratio of 1.05 and a strain ratio of 3.25 were calculated. 274 J Ultrasound Med 2012; 31:

3 Figure 2. Invasive ductal carcinoma of the left breast in a 37-year-old woman. Conventional sonography (left) shows a slightly hypoechoic mass with circumscribed margins, which was categorized as having a low suspicion of malignancy (category 4A). Sonographic elastography (right) shows no strain in the entire hypoechoic lesion (elasticity score of 4). A size ratio of 1.00 and a strain ratio of 6.06 were calculated. The strain ratios of the breast lesions were evaluated on the displayed static images with a color map, which assigned a particular color according to the degree of elasticity of the lesion components. The color displayed at the top of the color bar (red) indicates softer areas in the image relative to other areas in the same image. Correspondingly, the color at the bottom of the color bar (blue) indicates stiffer areas relative to other areas in the same image. On a representative static image, relative strain values of the mass and fat were measured. The first region of interest for the fat strain was manually drawn into an elliptical shape and placed in the fat tissue at a depth similar to or as close to the depth of the target mass to avoid pressure decay with depth. This first region of interest for the fat strain was placed in the fat tissue encoded as a mixture of red and green. The second region of interest for the mass strain was adjusted to the mass contours to encompass the maximum mass area that was placed in the mass. The strain ratio, defined as the fat to mass strain ratio, which indicated mass stiffness, was calculated automatically by an embedded software program in the ultrasound unit. At our institution, we select more than 10 consecutive images without movement or pressure artifacts to obtain the mean strain values for increased accuracy and objectivity. These mean strain values were also calculated automatically by the software program. The elasticity scores of the target lesions were assessed using the scoring system described by Itoh et al. 10 A score of 1 indicated even strain for the entire hypo - echoic lesion (ie, the entire lesion was evenly shaded green). A score of 2 indicated strain in most of the hypoechoic lesion with some areas of no strain (ie, the hypo echoic lesion showed a green and blue mosaic pattern). A score of 3 indicated strain at the periphery of the hypoechoic lesion with sparing of the center of the lesion (ie, the peripheral part of the lesion was green, and the central part was blue). A score of 4 indicated no strain in the entire hypoechoic lesion (ie, the entire lesion was blue, but its surrounding area was not included; Figures 1 and 2). A score of 5 indicated no strain in the entire hypo - echoic lesion or surrounding area (ie, both the entire hypoechoic lesion and its surrounding area were blue). Histologic Analysis The histologic diagnoses were obtained for all target lesions by sonographically guided core biopsy after sonographic elastography. The sonographically guided core biopsy procedures were performed by 1 of 2 board-certified radiologists specializing in breast imaging. To avoid the possibility of underestimation of the core biopsy, the final diagnoses after subsequent surgical excision or vacuumassisted removal were used as a reference standard. Data Collection and Analysis The clinical, histologic, and imaging findings were reviewed, including the interpretation criteria for sonographic elastography. To evaluate the differences between benign and malignant masses on sonographic elastography, the interpretation criteria, including the size ratio, strain ratio, and elasticity score of the target lesion, were compared relative to the histologic diagnosis by the Student t test. Statistical analyses were performed with SPSS version 18 software for Windows (SPSS Inc, Chicago, IL). Two-tailed P <.05 was considered statistically significant. To evaluate the performance of sonographic elastography for the differentiation of benign and malignant histologic characteristics, the rates of malignancy according to the interpretation criteria were calculated. In addition, the diagnostic performance of the interpretation criteria was compared with that of conventional sonography by the area under the receiver operating characteristic curve using MedCalc version 10.1 software for Windows (MedCalc Software, Mariakerke, Belgium). To suggest optimal quantitative interpretation criteria for the differentiation of benign and malignant masses, the best cutoff point to achieve the maximal sum of the sensitivity and specificity was calculated. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the interpretation criteria, as determined by sonographic elastography, were calculated when the best interpretation criteria cutoff points were used. Then the interpretation criteria for sonographic elastography were correlated with the BI-RADS categories for conventional sonography. J Ultrasound Med 2012; 31:

4 Results Pathologic Diagnoses A total of 104 patients had 1 lesion, and 6 patients had 2 lesions. Of the 110 breast masses, 68 (61.9%) were benign and 42 (38.1%) were malignant based on the results of core biopsies. Sixty-eight lesions (26 benign and 42 malignant) were surgically confirmed, and 42 (all benign) were diagnosed by vacuum-assisted removal. After surgical confirmation, 1 of 5 ductal carcinomas in situ was upgraded as an invasive ductal carcinoma, and 1 atypical ductal hyperplasia was also upgraded as a ductal carcinoma in situ. Thus, 67 benign masses (60.9%) and 43 malignant masses (39.1%) were finally diagnosed. The benign masses included fibrocystic changes (n = 18), fibroadenomas (n = 17), inflammation (n = 8), intraductal papillomas (n = 6), fibroadenomatoid mastopathy (n = 4), sclerosing adenosis (n = 3), stromal fibrosis (n = 2), and other benign masses (n = 9). The malignant masses included invasive ductal carcinomas (n = 31), ductal carcinomas in situ (n = 5), invasive lobular carcinomas (n = 4), invasive apocrine carcinomas (n = 2), and an invasive papillary carcinoma (n = 1). The mean sizes of the breast masses were 1.46 cm (range, cm) for benign lesions and 2.06 cm (range, cm) for malignant lesions. Size Ratios of the Target Lesions For the 67 benign masses, the size ratios ranged from 0.81 to 1.4 (size ratio <1.0, n = 24 [92.3%]; size ratio 1.0, n = 31 [70.5%]; size ratio >1.0, n = 12 [30%]; Figure 1). For 43 malignant masses, the size ratios ranged from to 1.3 (size ratio <1.0, n = 2 [7.7%]; size ratio 1.0, n = 13 [29.5%]; size ratio >1.0, n = 28 [70%]; Figure 2). The size ratios between conventional sonography and sonographic elastography of the malignant masses were significantly greater than those of the benign masses (P =.005; Tables 1 and 2). Strain Ratios of the Target Lesions For the 67 benign masses, the mean strain ratio ± SD was 3.12 ± 1.58 (range, ; Figure 1). For the 43 malignant masses, the mean strain ratio was 5.42 ± 1.35 (range, ; Figure 2). The strain ratios of the malignant masses were significantly greater than those of the benign masses (P <.001; Table 1). Elasticity Scores of the Target Lesions The mean elasticity score for malignant lesions (3.7 ± 1.1) was significantly higher than that for benign lesions (2.4 ± 0.8; P <.001; Table 1). Among the 67 benign breast masses, 57 lesions (85.1%) had scores of 1, 2, or 3 (score 1, n = 2 [100%]; score 2, n = 47 [79.7%]; score 3, n = 8 [100%]). Nine of the 67 benign lesions (13.4%) had a score of 4 (31.0%; Figure 1). Only 1 benign mass had a score of 5. This benign lesion was diagnosed as fibrosis, which had a size ratio of 1.84, a strain ratio of 9.66, and BI-RADS category 4B. Among the 43 malignant breast masses, 31 of 43 (72.1%) had elasticity scores of 4 or 5 (score 4, n = 20 [69.0%]; score 5, n =11 [91.7%]; Figure 2). There were no malignant lesions with a score of 1 or 3. However, 12 of 43 malignant lesions (27.9%) had a score of 2 (20.3%; Table 3). Breast Imaging Reporting and Data System Classification by Conventional Sonography By conventional sonography, the final assessment categories according to the BI-RADS classification 9 were as follows: category 3 (probably benign), 22 lesions (all benign); category 4A (low suspicion of malignancy), 37 lesions (34 benign and 3 malignant); category 4B (intermediate suspicion of malignancy), 19 lesions (10 benign and 9 malignant); category 4C (moderate suspicion of malignancy), 8 lesions (1 benign and 7 malignant); and category 5 (highly suggestive of malignancy), 24 lesions (all malignant). Table 1. Malignancy Rates for the Size Ratio Ranges, Strain Ratio Ranges, and Elasticity Scores Lesions, n Benign Malignant Malignancy Parameter (n = 67) (n = 43) Rate, % P a Size ratio range.005 < > Mean ± SD 1.06 ± ± 0.11 Strain ratio range < Mean ± SD 3.12 ± ± 1.35 Elasticity score < Mean ± SD 2.4 ± ± 1.1 a Student t test. 276 J Ultrasound Med 2012; 31:

5 Table 2. Malignancy Rates for the Strain Ratio Ranges Correlated With Breast Imaging Reporting and Data System Categories BI-RADS Strain Ratio Range Category Total 3 (n = 22) 0/5 (0) 0/7 (0) 0/7 (0) 0/2 (0) 0/1 (0) 0/22 (0) 4A (n = 37) 0/7 (0) 0/17 (0) 1/9 (11) a 0/2 (0) 1/1 (100) 2/36 (6) 4B (n = 19) 0 0/1 (0) 3/5 (60) b 3/5 (60) 4/9 (44) 10/20 (50) 4C (n = 8) 0 1/1 (100) c 0/1 (0) 1/1 (100) 5/5 (100) 7/8 (88) 5 (n = 24) 0 0 1/1 (100) d 4/4 (100) 19/19 (100) 24/24 (100) Data are numbers of lesions (percent). Percentages have been rounded. BI-RADS indicates Breast Imaging Reporting and Data System. a The surgical histologic diagnosis was a 0.9-cm high-grade ductal carcinoma in situ with a strain ratio of b The surgical histologic diagnoses were a 1.0-cm ductal carcinoma in situ with a strain ratio of 3.22 and an elasticity score of 4, a 1.8-cm invasive ductal carcinoma with a strain ratio of 3.56 and a size ratio of 1.06, and a 4.5-cm ductal carcinoma in situ with a strain ratio of c The surgical histologic diagnosis was a 0.8-cm high-grade ductal carcinoma in situ with a strain ratio of d The surgical histologic diagnosis was a 4.0-cm invasive ductal carcinoma with a strain ratio of Diagnostic Performance of Sonographic Elastography and Conventional Sonography The diagnostic performance of the 3 interpretation criteria for sonographic elastography is shown in Table 4. According to the conventional method, a cutoff point is considered optimal if it attains the maximum value of the sum of the sensitivity and specificity. For the size ratio, when a cutoff point of was used, the sensitivity, specificity, PPV, and NPV were 65.1% (28 of 43), 82.1% (55 of 67), 70.0% (28 of 40), and 78.6% (55 of 70), respectively. For the strain ratio, the sensitivity, specificity, PPV, and NPV were 86.0% (37 of 43), 85.1% (57 of 67), 78.7% (37 of 47), and 90.5% (57 of 63), with the best cutoff point calculated to be For the elasticity score, the sensitivity, specificity, PPV, and NPV were 72.1% (31 of 43), 85.1% (57 of 67), 75.6% (31 of 41), and 82.6% (57 of 69), with the best cutoff point between elasticity scores of 3 and 4. With a best cutoff point for conventional sonography between BI-RADS categories 4A and 4B, the sensitivity, specificity, PPV, and NPV were 93.0% (40 of 43), 83.6% (56 of 67), 78.4% (40 of 51), and 94.9% (56 of 59). The 3 interpretation criteria enabled the differentiation of benign from malignant breast lesions with statistical significance (P <.001). The values for the area under the receiver operating characteristic curve were (95% confidence interval [CI], ) for conventional sonography and (95% CI, ), (95% CI, ), and (95% CI, ) for the strain ratio, size ratio, and elasticity score, respectively (Figure 3). Interpretation Criteria for Sonographic Elastography and BI-RADS Category Correlation The correlation of BI-RADS categories with interpretation criteria for sonographic elastography is detailed in Table 5. Discussion On sonographic elastography, fat tissue can be an objective and constant reference for relative strain because fat tissue has a constant modulus over various compression loading compared with the surrounding breast parenchyma. 11 To our knowledge, few reports exist about the use of sono- Table 3. Lesions With False-Negative Findings on Sonographic Elastography False-Negative Pathologic Size Ratio Strain Ratio Elasticity Score Finding Lesions, n Mean Value (Range) Lesions, n Mean Value (Range) Lesions, n Mean Score IDC ( ) ( ) 7 2 DCIS ( ) ( ) 2 2 ILC PC IAC DCIS indicates ductal carcinoma in situ; IAC, invasive apocrine carcinoma; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; and PC, papillary carcinoma. J Ultrasound Med 2012; 31:

6 graphic elastography for the differentiation of breast masses using the fat to mass strain ratio applied in our study. 4 8 In addition, we used a new method of sonographic elastography for differentiation between benign and malignant breast masses. Our study showed that there was a significant difference in the size ratio between the benign and malignant breast masses, as follows: 1.00 ± 0.11 (range, ) for benign masses and 1.06 ± 0.09 (range, ) for malignant masses (P =.005). A size ratio cutoff point of made the best differentiation between benign and malignant masses. In a previous report, an area ratio was used as the size parameter, and a cutoff point of 1.2 was the best for differentiation between benign and malignant masses. 12 Regner et al 13 reported that cutoff points of 1.04 for the width ratio (ie, size ratio) and 1.13 for the area ratio were best for differentiating breast masses. Our study results showed that the strain ratio of the malignant masses was significantly greater than that of the benign masses, as follows: 3.12 ± 1.58 (range, ) for benign masses and 5.42 ± 1.35 (range, ) for malignant masses (P <.001). A strain ratio cutoff point of enabled the best differentiation between benign and Table 4. Diagnostic Performance of the Size Ratios, Strain Ratios, and Elasticity Scores at Various Cutoff Points Cutoff Point Sensitivity, % Specificity, % PPV, % NPV, % Size ratio Strain ratio Elasticity score Between 1 and Between 2 and Between 3 and Between 4 and malignant masses. Our results are in agreement with the results of the 1998 study by Krouskop et al, 11 which showed that the elastic modulus of a malignant mass was greater than that of a benign mass and the elastic modulus of a benign mass was greater than that of fat tissue. Recent studies have suggested that the fat to lesion strain ratio showed the best cutoff points from 2.24 to This diversity of cutoff points was probably due to technical differences, which included the depth of the reference fat, and population differences, such as various sizes or various malignancy proportions of the breast masses. In this study, we found a significantly higher elasticity score for malignant lesions (3.7 ± 1.1) compared with benign lesions (2.4 ± 0.8; P <.001). A cutoff point between elasticity scores of 3 and 4 resulted in the best differentiation between benign and malignant masses. Several previous studies have reported that the mean elasticity scores for benign masses were 1.8 ± 0.9 to 2.1 ± 1.0, whereas those for malignant masses were 4.1 ± 0.9 to 4.2 ± ,14,15 In those studies, a cutoff point between elasticity scores 3 and 4 was used for the differentiation between benign and malignant masses. In the receiver operating characteristic curve analysis for the 3 interpretation criteria, the area under the curve value was slightly greater for conventional sonography (0.959 [95% CI, ]) than for the strain ratio of sonographic elastography with the tissue-specific imaging preset (0.901 [95% CI, ]). However, there Figure 3. Receiver operating characteristic curves for the 3 interpretation criteria for sonographic elastography and conventional sonography. The area under the receiver operating characteristic curve (Az) values were (95% confidence interval [CI], ) for conventional sonography and (95% CI, ), (95% CI, ), and (95% CI, ) for the strain ratio, size ratio, and elasticity score, respectively. NPV indicates negative predictive value; and PPV, positive predictive value. 278 J Ultrasound Med 2012; 31:

7 was no statistical significance between these values (P =.052). With a best cutoff point for conventional sonography and the strain ratio, the sensitivity for conventional sonography was higher than that for the strain ratio (93.0% for conventional sonography versus 86.0% for the strain ratio). To identify all breast cancers, a strain ratio of less than would be needed, which has 100% sensitivity. In this study, 34 of 37 BI-RADS category 4A lesions (91.9%) were finally diagnosed as benign lesions. According to our results, the strain ratio among the 3 interpretation criteria for sonographic elastography showed the highest reliability for benignity (85.3% [29 of 34] for a size ratio <1.005; 97.1% [33 of 34] for a strain ratio <4.215; 85.3% [29 of 34] for an elasticity score between 3 and 4). Therefore, in this group of low-suspicion (BI-RADS category 4A) lesions, sonographic elastography using the strain ratio might serve a beneficial role with a high likelihood of benignity and allow recategorizing some BI-RADS category 4A lesions as either BI-RADS category 3 or even 2. According to a strain ratio cutoff point of 4.215, 6 malignant masses had strain ratios of less than (Tables 2 and 3). These lesions with false-negative findings were confirmed as 4 ductal carcinomas in situ (category 4A, n = 1; category 4B, n = 2; category 4C, n = 1) and 2 invasive ductal carcinomas (category 4B, n = 1; category 5, n = 1). The mean strain ratios of these lesions were 3.30 (range, ) for the ductal carcinomas in situ and 3.65 (range, ) for the invasive ductal carcinomas. These findings are in agreement with the results of the 1998 study by Krouskop et al, 11 which showed that ductal carcinomas in situ had a more complex elastic modulus than other breast tissues and were much stiffer than normal Table 5. Correlation of Breast Imaging Reporting and Data System Categories With Interpretation Criteria of Sonographic Elastography BI-RADS Categories (Benign/Malignant) 3 4A 4B 4C 5 Parameter (n = 22) (n = 37) (n = 19) (n = 8) (n = 24) Size ratio < (6/0) 6 (6/0) 1 (1/0) 0 (0/0) 0 (0/0) (14/0) 26 (23/3) 8 (4/4) 6 (1/5) 6 (0/6) (2/0) 5 (5/0) 10 (5/5) 2 (0/2) 18 (0/18) Strain ratio < (12/0) 22 (22/0) 1 (1/0) 0 (0/0) 0 (0/0) (8/0) 12 (11/1) 5 (2/3) 2 (1/1) 1 (0/1) (2/0) 3 (1/2) 13 (7/6) 6 (0/6) 23 (0/23) Elasticity score <2 0 (0/0) 2 (2/0) 0 (0/0) 0 (0/0) 0 (0/0) (21/0) 28 (27/1) 11 (7/4) 2 (0/2) 5 (0/5) 4 1 (1/0) 7 (5/2) 8 (3/5) 6 (1/5) 19 (0/19) BI-RADS indicates Breast Imaging Reporting and Data System. glandular tissue and softer than invasive ductal carcinomas at high strain levels but softer than normal glandular tissues at low strain levels. To decrease the number of these false-negative findings, it would be helpful to use the strain ratio of sonographic elastography in conjunction with the BI-RADS categories for conventional sonography. In our study, only 1 of 6 lesions with false-negative findings (strain ratios <4.215) was categorized as 4A; however, the others were categorized as 4B (n = 3), 4C (n = 1), and 5 (n = 1). In addition, a narrowed cutoff point for the strain ratio would improve the sensitivity of this technique, thus reducing the false-negative rate. If a strain ratio cutoff of was used, we could achieve 100% sensitivity for differentiation between benign and malignant breast masses. Indeed, all BI- RADS category 4 lesions that had strain ratios of less than were benign. Thus, the use of narrowed criteria would have reduced our benign biopsy rate by 31.8% (35 biopsies of category 3 [n = 12], 4A [n = 22], and 4B [n = 1] lesions avoided). This study had some limitations. First, it was designed as a retrospective study. Thus, it was not possible to blind the operator from the conventional sonographic findings before the sonographic elastographic assessment. Second, we did not assess interobserver or intraobserver variability with respect to performing and interpreting elastography. However, 1 of 2 radiologists evaluated the elastographic images. Furthermore, a large-scale trial addressing appropriate patient selection, diagnostic parameters, and practical application of this technique might be necessary for a more standardized assessment and subsequent improvement of the diagnostic performance of sonographic elastography with the tissue-specific imaging preset. In conclusion, among the interpretation criteria, the strain ratio of the lesions showed better diagnostic performance than the size ratio (P =.012) and the elasticity score (P =.013). 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