The diagnosis of hepatocellular carcinoma (HCC) can be made non-invasively without histopathological confirmation in high-risk patients (i.e., those with cirrhosis according to the European Association for the Study of the Liver [EASL v.2018], chronic hepatitis B viral infection, current or prior HCC according to the Liver Imaging Reporting And Data System [LI-RADS v.2018]), provided that the liver nodules display typical imaging features [1], [2], [3]. These typical imaging features slightly differ among international guidelines, but all include at least arterial phase hyper-enhancement (APHE) and washout [1], [2], [3], [4], [5], [6].

The assessment of these two features is purely visual and does not rely on quantitative methods. The depiction of APHE can be challenging for nodules that are spontaneously hyperintense on T1-weighted images. The reported rate of spontaneously hyperintense nodules on T1-weighted images in cirrhotic liver, ranges from 12 to 25% of observations [7], [8], [9]. The differentials include HCCs but also regenerative or dysplastic nodules, adenoma and focal nodular hyperplasia [10]. Seventeen p. cent of HCCs can also show hyperintensity on T1-weighted images due to the accumulation of copper, iron and/or manganese. Hyperintensity on T1-weighted images is associated with the degree of differentiation, being reported for Edmonson grade 1 or 2 HCCs, but not grades 3 or 4 [11]. To address this, guidelines recommend the use of arterial phase subtraction images [12,13]. However, using such subtraction images on post-arterial phases (i.e., portal venous phase [PVP], delayed phase [DP], transitional phase [TP] and hepatobiliary phase [HBP]) to extract features, especially washout, has never been properly investigated and is not currently included in international recommendations.

The purpose of this study was to assess the value of subtraction imaging on post-arterial phase images (i.e., PV, DP/TP and HBP) for the non-invasive diagnosis of HCC in spontaneously hyperintense nodules on T1-weighted images in patients with cirrhosis.