江尻 夏樹¹, 今野 佐智代¹, 薄根 美咲¹, 髙瀬 直敏¹, 吉原 明美¹, 林 光弘², 竹川 英宏^{1, 3, 4}

Natsuki EJIRI¹, Sachiyo KONNO¹, Misaki USUNE¹, Naotoshi TAKASE¹, Akemi YOSHIHARA¹, Mitsuhiro HAYASHI², Hidehiro TAKEKAWA^{1, 3, 4}

¹獨協医科大学病院超音波センター, ²獨協医科大学病院乳腺センター, ³獨協医科大学病院脳卒中センター, ⁴獨協医科大学病院脳神経内科

¹Center of Medical Ultrasonics, Dokkyo Medical University, ²Breast Center, Dokkyo Medical University, ³Stroke Center, Dokkyo Medical University, ⁴Department of Neurology, Dokkyo Medical University

キーワード : breast cancer, breast ultrasound, quantitative imaging, strain elastography, shear wave elastography

目的：BI-RADS USの診断基準に準拠したB-mode診断にshear wave elastography （SWE） の所見を加味し，乳腺腫瘤の良悪性診断能が向上するかを検討した．対象と方法：乳腺腫瘤97例（悪性42例）を対象に，B-modeで最大腫瘤径とdepth width ratio （D/W） を計測しBI-RADS USに従いカテゴリー分類した．SWEは剪断波伝播速度，組織弾性値および弾性値のカラーパターンを評価し，良悪性の差と診断率を求めた．結果と考察：悪性腫瘤は有意に高齢で，最大腫瘤径，D/W，剪断波伝搬速度，組織弾性値が高値であった．また悪性腫瘤の弾性値表示画像はカラーパターン3，4が多かった（p＜0.0001）．多変量解析では，剪断波伝搬速度 ≧ 4.07 m/s（オッズ比 17.1），組織弾性値 ≧ 53.7 kPa（17.1）およびカラーパターン≧ 3（19.2）が有用であった．さらにBI-RADS USカテゴリー 3，4の76例では，陰性的中率はカラーパターン≧ 3（91.7％）が， 陽性的中率は剪断波伝搬速度 ≧ 4.07 m/sまたは組織弾性値 ≧ 53.7kPa（61.9％）が最も高値であり，SWEの追加評価の有用性が示唆された．結論：BI-RADS USカテゴリー3と4の症例にSWEの所見を加味することで診断能の向上が得られる可能性が示された．

Purpose: We evaluated the benign and malignant diagnosis of breast tumors by adding shear wave elastography (SWE) to BI-RADS ultrasound (US). Methods: The maximum tumor diameter and depth width ratio (D/W) were measured by B-mode and categorized according to BI-RADS US in 97 breast tumors (55 benign and 42 malignant). Shear wave speed, elastic modulus, and color pattern classification of modulus were evaluated by SWE to determine the difference between benign and malignant tumors and to evaluate the diagnostic rate of malignant tumors. Results and Discussion: Malignant tumors were significantly older and had higher values for maximum tumor diameter, D/W, shear wave speed, and elastic modulus. Color pattern classification of the modulus in malignant tumors was often pattern 3 and 4 (p＜0.0001). Corrected for confounding factors, shear wave speed ≧4.07 m/s (odds ratio 17.1), elastic modulus ≧53.7 kPa (odds ratio 17.1), and color pattern ≧3 (odds ratio 19.2) were useful. Furthermore, in the analysis of 76 patients classified as BI-RADS US categories 3 and 4, the highest negative predictive value (91.7%) was found for color pattern ≧3, and the highest positive predictive value (61.9%) was found for shear wave speed ≧4.07 m/s or elastic modulus ≧53.7 kPa, suggesting the usefulness of additional evaluation of SWE. Conclusion: Addition of SWE findings to BI-RADS US findings, especially in cases of categories 3 and 4, might improve the diagnostic rate.