杉森 一哉¹, 沼田 和司¹, 岡田 真広², 二本松 宏美¹, 竹林 茂生³, 前田 愼⁴, 中野 雅行⁵, 田中 克明¹

Kazuya SUGIMORI¹, Kazushi NUMATA¹, Masahiro OKADA², Hiromi NIHONMATSU¹, Shigeo TAKEBAYASHI³, Shin MAEDA⁴, Masayuki NAKANO⁵, Katsuaki TANAKA¹

¹横浜市立大学附属市民総合医療センター消化器病センター, ²琉球大学医学部附属病院放射線部, ³横浜市立大学附属市民総合医療センター放射線科, ⁴横浜市立大学附属病院消化器内科, ⁵湘南藤沢徳洲会病院病理部

¹Gastroenterological Center, Yokohama City University Medical Center, ²Department of Radiology, University Hospital of the Ryukyus, ³Department of Radiology, Yokohama City University Medical Center, ⁴Division of Gastroenterology, Yokohama City University Graduate School of Medicine, ⁵Pathological Department, Shonan Fujisawa Tokusyukai Hospital

キーワード : magnetic resonance imaging with gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid, contrast-enhanced ultrasonography, regenerative nodule, early hepatocellular carcinoma, high-grade dysplastic nodule

目的：慢性肝疾患患者にガドキセト酸ナトリウム（gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid: Gd-EOB-DTPA）での核磁気共鳴画像 （magnetic resonance imaging: MRI）（EOB-MRI）および造影超音波を施行して，早期肝細胞癌（early hepatocellular carcinoma: eHCC）や高度異型結節（high grade dysplastic nodule: HGDN）と再生結節（regenerative nodule: RN）の鑑別に有用な特徴的所見を調査した．対象と方法：最大径が1 cm以上でかつ病理学的に診断された平均腫瘍径がそれぞれ15.5 mm，15.1 mm，14.8 mmの早期肝細胞癌（100結節），HGDN （7結節），RN （20結節）を後ろ向きに検討した．これらの結節のEOB-MRI肝細胞相の信号強度所見と，造影超音波動脈相の所見を用い，RNに特徴的な所見について検討した．結果：早期肝細胞癌100結節中98結節は，EOB-MRIの肝細胞相で低信号（n＝95），等信号（n＝2），高信号（n＝1）を呈し，HGDN 7結節は，低信号（n＝6），または高信号（n＝1）を呈し，造影超音波動脈相においてはいずれも求心性血管を認めた．早期肝細胞癌1結節では，EOB-MRI肝細胞相で低信号を呈し，造影超音波動脈相で遠心性血管と求心性血管の両方が観察された．RN 20結節中18結節と早期肝細胞癌の残りの1結節ではEOB-MRIで結節中心に小さな低信号域を伴い，周囲は高信号を呈した．残り2結節のRNでは肝細胞相で高信号のみを呈し，造影超音波動脈相で遠心性血管が観察された．結節中心部の小低信号域は，造影超音波動脈相では中央から辺縁に向かって走行する肝動脈とそれに伴走する門脈に一致していた．結論：EOB-MRI肝細胞相および造影超音波動脈相での中心部の血管構造所見は，RNに特徴的な所見である可能性がある．

Objective: We investigated the characteristic findings of regenerative nodules (RNs) for differentiating early hepatocellular carcinoma (HCC) from high-grade dysplastic nodules (HGDNs) using magnetic resonance imaging (MRI) with gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA,EOB-MRI) and contrast enhanced ultrasonography (CEUS) in patients with chronic liver disease. Subjects and methods: Pathologically confirmed lesions (100 early HCCs, 7 HGDNs, and 20 RNs with a maximum diameter of more than 1 cm and mean maximal diameters of 15.5, 15.1, and 14.8 mm, respectively) were enrolled in this retrospective study. The signal intensities of these lesions during the hepatobiliary phase of EOB-MRI were investigated, and findings characteristic of RNs using this modality were also evaluated using CEUS. Results: Ninety-eight of the 100 early HCCs that were hypo-intense (n=95), iso-intense (n=2), or hyper-intense (n=1) and the seven HGDNs that were hypo-intense (n=6) or hyper-intense (n=1) during the hepatobiliary phase of EOB-MRI exhibited centripetal vessels during the arterial dominant phase of CEUS, although one early HCC that was hypo-intense exhibited both centrifugal and centripetal vessels. Eighteen of the 20 RNs and one early HCC that were hyper-intense with a small central hypo-intensity and the remaining two RNs that were hyper-intense on EOB-MRI exhibited centrifugal vessels during the arterial dominant phase of CEUS. The small central hypo-intense area corresponded to central vascular structures in the lesion, such as the hepatic artery and portal vein running from the center to the periphery, when viewed using CEUS. Conclusion: Central vascular structures may be a characteristic finding of RNs when observed during the hepatobiliary phase of EOB-MRI and the arterial dominant phase of CEUS.