野々村 和洋^{1, 3}, 島本 佳寿広², 畑佐 和昭³, 水野 求³, 町田 君成³, 水野 裕文³, 田中 洋³, 榊原 聡⁴

Kazuhiro NONOMURA^{1, 3}, Kazuhiro SHIMAMOTO², Kazuaki HATASA³, Motomu MIZUNO³, Kiminari MACHIDA³, Hirohumi MIZUNO³, Hiroshi TANAKA³, Satoshi SAKAKIBARA⁴

¹土岐市立総合病院中央放射線技術部, ²名古屋大学医学部保健学科放射線技術科, ³名古屋大学大学院医学系研究科医療技術学専攻医用量子科学分野, ⁴土岐市立総合病院外科

¹Department of Radiological Technology, Toki General Hospital, ²Department of Radiological technology, Nagoya University School of Health Sciences, ³Nagoya University Graduate School of Medicine, Nagoya University School of Health Sciences, ⁴Department of Surgery, Toki General Hospital

キーワード : ultrasonography, mammary, tissue characterization, breast neoplasm, deformation index

目的：日本超音波医学会による腫瘤像形成性病変に関する乳房超音波診断ガイドライン（2005年）では圧迫による硬さの評価が新たな所見項目に加わった．硬さは動画観察下での主観的評価であり客観性に乏しいため，我々は特殊な装置ではなく汎用のリニア探触子および市販のデジタル体重計を用いて圧迫前後の腫瘤の縦横比の変化と内部エコーレベルの変化を指標とした定量的な硬さと輝度変化率の評価を試み，良悪性鑑別診断における有用性について検討した．方法：対象は乳腺腫瘤139症例（良性89例，悪性50例）である．患者を体重計の上に仰臥位としたうえで，体重計の示す値が3.0±0.6kg重となるように10MHz（4‐10MHz）リニア探触子を用いて用手的に圧迫加重した．圧迫加重前後の腫瘤の縦横比をそれぞれD1，D2とし，変形指標Deformation Index（D.I.）＝［1-D2/D1］×100（％）と定義した。圧迫前後の腫瘤の内部エコーレベルをそれぞれB1，B2とし，B2/B1×100（％）を内部エコーの輝度変化率として求めた．結果： D.I.は，良性35.5±14.7％，悪性15.4±6.2％で良悪性間に有意差を認めた（p＜0.001）．良悪性鑑別のカットオフ値は25％前後と考えられた．輝度変化率は良性149.7±34.3％，悪性122.9±19.9％であり，両者に有意差を認めた（p＜0.001）．結論：汎用の探触子を用いた圧迫加重による乳腺腫瘤のD.I.と内部エコーの輝度変化率は，良悪性鑑別診断の定量的指標として有用であった．

Purpose: Regarding mass image-forming lesions, the 2005 Guidelines for Ultrasonic Diagnosis of Breast Diseases, published by the Japan Society of Ultrasonics in Medicine (JSUM), includes the evaluation of tumor compressibility, which is visually assessed by the degree of deformation caused by applying external pressure to the tumor. However, this is only a subjective estimation under real-time observation; consequently, quantitative evaluation of tumor deformation and the percentage change in internal echo intensity was attempted based on changes in the depth-width ratio and in the internal echo intensity on hand-held probe compression. We evaluated the usefulness of these measurements in the differential diagnosis of benign and malignant tumors. Method: The subjects were 139 patients (89 benign and 50 malignant cases) who underwent breast ultrasonography with a 10-MHz (from 4- to 10-MHz) linear probe. The deformation index (D.I.) of the tumor was defined as: [1−(depth-width ratio with 3.0±0.6-kg-weighted compression)/(depth-width ratio without compression)]×100 (%). The rate of change in internal echo intensity was defined as the echo intensity with compression divided by the echo intensity without compression×100 (%). Result: There was a significant difference in the D.I. between benign lesions (35.5%±14.7%) and malignant lesions (15.4%±6.2%) (P<0.001). The cut-off ratio in differentiating benign from malignant lesions was approximately 25%. The rate of change in echo intensity of benign lesions (149.7%±34.3%) was significantly higher than that of malignant lesions (122.9%±19.9%) (P<0.001). Conclusion: Using an electronic linear probe, quantitative indexes including the D.I. and the rate of change in internal echo intensity could be obtained with the help of a weight meter, and could prove effective for the differential diagnosis of breast mass-image forming lesions.