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英文誌(2004-)

Journal of Medical Ultrasonics

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2007 - Vol.34

Vol.34 No.03

State of the Art(特集)

(0305 - 0311)

超音波解剖と走査法の工夫を中心に

Topography of the pancreas and scanning techniques in pancreatic sonography

榎 真美子, 石田 秀明, 小松田 智也, 渡部 多佳子, 八木澤 仁

Mamiko ENOKI, Hideaki ISHIDA, Tomoya KOMATSUDA, Takako WATANABE, Hitoshi YAGISAWA

秋田赤十字病院超音波センター

Center of Diagnostic Ultrasound, Red Cross Hospital

キーワード : ultrasound, color Doppler, anatomy, pancreas, abdominal vessels

この章では,まず膵の解剖学的位置関係,特に周囲脈管系との関係を述べ,次いで,膵超音波検査で伝統的に用いられてきた走査法に,そして最後に我々が推奨する走査法の工夫について解説する.通常の走査法では,一断面で膵全体を観察するのは困難で,幾つかの走査面を組み合わせざるを得ない.大まかには,次の4走査法が中心となる.a)上腹部横走査:脾静脈を指標として膵頭体部を観察する.b)上腹部矢状走査:この断面では腹腔動脈と上腸間膜動脈に挟まれた膵が見える.これらは全て呼吸性に移動する.c)右上腹部斜走査:門脈本幹を指標にその腹側の頭部と背部の釣部を観察するのに適している.d)左上腹部斜走査:脾動静脈を指標にその腹側の膵尾部を観察するのに適している.我々は,走査法の工夫として,1)プローブを回転させる(回外運動),2)船頭の船こぎ様に手首を背屈させる(背屈運動),3)たすきがけの様に,膵尾部を見る時は頭部に,頭部を見る時は尾部に,プローブを移動させ,目的箇所を斜めに観察する.4)必要に応じ,プローブを円弧状に移動させるなど,1)‐3)を組み合わせたり変法を加える.なお,今まで引水法や体位の変換を推賞しているテキストもあったが,被検者にかかる負担が大きく,その割に効果がなかったのであまりお薦め出来ない.

The aim of this chapter is to discuss the topography of the pancreas with an emphasis on the relationship between the gland and the surrounding vessels, then to review the traditional scanning techniques used in pancreatic sonography. Finally, we recommend some additional scanning techniques to increase diagnostic confidence. In the case of traditional scanning techniques, there is no single scanning method for observing the whole gland. Four principal sectional views should be recognized: a) The transverse view demonstrates the gland as well as vascular landmarks. The examination usually begins with the patient supine. The probe is located just below the xiphoid process. The splenic vein is the most important vascular landmark in this plane. It runs from right to left across the upper abdomen. The pancreatic body and tail are anterior to it. B) The sagittal view demonstrates the pancreas as an oval structure between the celiac axis and the superior mesenteric artery. The anteroposterior diameter and shape as well as the location vary considerably according to the respiratory condition. C) The oblique view in the right upper abdomen shows the superior mesenteric vein joining the splenic vein to form the main portal trunk. This vascular landmark is seen sandwiched between the pancreatic head anteriorly and the uncinate process posteriorly. D) The oblique view in the left intercostal space shows the spleen. The pancreatic tail appears as a homogenous band-like structure in the splenic hilus. The probe is usually placed near the left midaxillary line between ribs. Alternative scanning (our recommended) techniques are as follows a) It is especially important to rotate the probe to minimize the amount of gas in the stomach and duodenum as well as to widen appropriate acoustic windows. The pancreas can be clearly observed by rotating the probe, which allows a rapid and clear assessment of the gland. B) In difficult cases, the probe is located above the pancreatic head are obliquely radiate the beam toward the pancreatic tail, and then slide the probe above the pancreatic tail and obliquely radiate the beam toward the pancreatic head. This so-called “cross-line” method with/without probe rotation is suitable for easy visualization of the whole gland and the neighboring vessels. Conclusion: Some authors have advocated the uptake of 200 CC of water to use the water-filled stomach as an acoustic window. Others have recommended changing the patient's position to an oblique or erect position, for example. Other maneuvers include applying probe pressure on the area of interest on the abdomen. However, these techniques have had very little success. When traditional approaches have failed or provided limited results, the above alternative scanning techniques, although requiring additional effort to learn them,, will minimize the diagnostic problems currently inherent to traditional scanning methods.