橋本 秀行¹, 神山 直久², 岡村 陽子²

Hideyuki HASHIMOTO¹, Naohisa KAMIYAMA², Yoko OKAMURA²

¹ちば県民保健予防財団総合健診センター乳腺科, ²東芝メディカルシステムズ超音波開発部

¹Breast Cancer Screening Center, Chiba Foundation for Health Promotion and Disease Prevention, ²Ultrasound Systems Division, Toshiba Medical Systems Corp

キーワード : microcalcification, breast cancer, ultrasonography, intervention

我国における乳癌の罹患率・死亡率は，年々，上昇しており，早期発見の意義は非常に大きい．マンモグラフィで容易に検出出来る微細石灰化は，乳癌の最も早期である非浸潤性乳管癌に認められることの多い所見であるが，乳房超音波検査では，検出の難しいことがあり弱点とも言われている．そこで，我々は容易に微細石灰化を検出出来る石灰化フィルタ（firefly）を開発し，診断および臨床応用について検討した．乳腺の超音波画像は非常に複雑な構造をしており，石灰化の高輝度エコーを視認（同定）出来ないことが多い．今回，開発した石灰化フィルタは周囲と連続にあるものを消去し，点状の高輝度を強調するものである．このフィルタを使用すると闇夜の中で蛍（firefly）が光るように石灰化を同定出来る．これまで218例の微細石灰化症例を検討したところ，確実に検出能が上昇していた．現在，微細石灰化の組織診断にはステレオ（マンモグラフィ）ガイド下のインターベンションが主流であり，限られた施設でしか施行出来ない．しかし，このフィルタの開発により，どの施設でも超音波ガイド下の生検が可能となり，石灰化が確実に採取さている状況をリアルタイムに観察出来る．また，石灰化病変を主とする乳癌手術では拡がり診断を術中と同じ体位でマッピングが可能となる．微細石灰化検出フィルタfireflyを開発することにより，乳房超音波検診への期待も拡がり，その意義と有用性は非常に大きい．

The morbidity and the mortality of breast cancer in Japan continue to increase year by year, making early detection very important. It is easy to detect microcalcifications on mammography, but they are more difficult to detect on breast ultrasound, which is said to be a limitation of breast ultrasound. Microcalcifications are found in ductal carcinoma in situ (DCIS), which is the earliest stage of breast cancer. We have developed a new technology, the microcalcification detection filter (firefly), and examined diagnostic and clinical application. It is often difficult to identify the high-intensity echogenic spots of microcalcifications on the monitor because the mammary gland has a very complicated structure on B-mode ultrasound. Using the theory of CFAR (Contrast False Alarm Rate), we have erased the echogenic breast tissue on screen and emphasized punctate high-intensity microcalcifications. The microcalcifications can be identified with this filter, like the glitter of fireflies on a dark night. Two-hundred and eighteen cases were examined, in whom a clear increase in detectability was found. Intervention under stereo (mammography) guide is the mainstay of diagnosis of microcalcifications, but it can be performed only at a limited number of institution. The development of this filter will allow biopsy under guided ultrasound at any hospital, and it will also be possible to observe the microcalcifications on sampling. Furthermore, the extent of the surgical margin needs to be accurately evaluated before surgery. This filter will enable mapping of malignancy at the same position as the operation. Breast cancer screening with ultrasound may become widespread with use of the “firefly” microcalcification detection filter. The significance and utility of “firefly” are great.