Focal liver lesions detection and characterization: The advantages of gadoxetic acid-enhanced liver MRI

Since its clinical introduction, several studies in literature have investigated gadolinium ethoxybenzhyl diethylenetriaminepentaacetic acid or gadoxetic acid(Gd-EOB-DTPA) properties. Following contrast injection, it provides dynamic vascular phases(arterial, portal and equilibrium phases) and hepatobiliary phase, the latter due to its uptake by functional hepatocytes. The main advantages of Gd-EOB-DTPA of focal liver lesion detection and characterization are discussed in this paper. Namely, we focus on the possibility of distinguishing focal nodular hyperplasia(FNH) from hepatic adenoma(HA), the identification of early hepatocellular carcinoma(HCC) and the pre-operative assessment of metastasis in liver parenchyma. Regarding the differentiation between FNH and HA, adenoma typically appears hypointense in hepatobiliary phase, whereas FNH is isointense or hyperintense to the surrounding hepatic parenchyma. As for the identification of early HCCs, many papers recently published in literature have emphasized the contribution of hepatobiliary phase in the characterization of nodules without a typical hallmark of HCC. Atypical nodules(no hypervascularizaton observed on arterial phase and/or no hypovascular appearance on portal phase) with low signal intensity in the hepatobiliary phase, have a high probability of malignancy. Finally, regarding the evaluation of focal hepatic metastases, magnetic resonance pre-operative assessment using gadoxetic acid allows for more accurate diagnosis.

Diffusion-weighted MRI in a liver protocol: Its role in focal lesion detection

AIM: To evaluate the role of diffusion-weighted imaging (DWI) in the detection of focal liver lesions (FLLs), using a conventional magnetic resonance imaging (MRI) protocol. METHODS: Fifty-two patients (22 males, average age 55.6 years, range: 25-82 years), studied using a 1.5 Tesla magnetic resonance scanner, were retrospectively analyzed; detection of FLLs was evaluated by considering the number of lesions observed with the following sequences: (1) respiratory-triggered diffusion-weighted single-shot echo-planar (DW SS-EP) sequences; (2) fat-suppressed fast spin-echo (fs-FSE) T2 weighted sequences; (3) steady-state free precession (SSFP) images; and (4) dynamic triphasic gadolinium-enhanced images, acquired with three-dimensional fast spoiled gradient-echo (3D FSPGR). Two radiologists independently reviewed the images: they were blinded to their respective reports. DW SS-EP sequences were compared to fs-FSE, SSFP and dynamic gadolinium-enhanced acquisitions using a t -test. Pairs were compared for the detection of: (1) all FLLs; (2) benign FLLs; (3) malignant FLLs; (4) metastases; and (5) hepatocellular carcinoma (HCC). RESULTS: Interobserver agreement was very good (weighted = 0.926, CI = 0.880-0.971); on the consensus reading, 277 FLLs were detected. In the comparison with fs-FSE, DW SS-EP sequences had a significantly higher score in the detection of all FLLs, benign FLLs, malignant FLLs and metastases; no statistical difference was observed in the detection of hepatocellular carcinoma (HCCs). In the comparison with SSFP sequences, DW SS-EP had significantly higher scores (P < 0.05) in the detection of all lesions, benign lesions, malignant lesions, metastases and HCC. All FLLs were better detected by dynamic 3D FSGR enhanced acquisition, with P = 0.0023 for reader 1 and P = 0.0086 for reader 2 in the comparison with DW SS-EP sequences; with reference to benign FLLs, DW SS-EP showed lower values than 3D FSPGR enhanced acquisition (P < 0.05). No statistical differences were observed in the detection of malignant lesions and metastases; considering HCCs, a very slight difference was reported by reader 1 (P = 0.049), whereas no difference was found by reader 2 (P = 0.06). CONCLUSION: In lesion detection, DWI had higher scores than T2 sequences; considering malignant FLLs, no statistical difference was observed between DWI and dynamic gadolinium images.

Diagnosis of ruptured superior mesenteric artery aneurysm mimicking a pancreatic mass

Aneurysms and pseudoaneurysms of the superior mesenteric artery are potentially lethal and should be treated as urgently as possible.In a 52-year-old man with occasional epigastric pain,we accidentally discovered a superior mesenteric artery aneurysm that was ruptured with spontaneous tamponade in the uncinate process and in the head of the pancreas.The ruptured aneurysm had a heterogeneous appearance due to its thrombotic and hemorrhagic content,and it simulated a voluminous mass in the head and uncinate process of the pancreas,associated with mild dilatation of the main pancreatic duct.Recent advances in multidetector computed tomography and magnetic resonance imaging have enabled radiologists to develop a correct diagnosis of mesenteric aneurysms and pseudoaneurysms of the visceral branches of the abdominal aorta,and to differentiate this diagnosis from that of pancreatic or peripancreatic masses;angiography is currently used to confirm a diagnosis and to develop therapeutic treatments.