Menoufia Medical Journal

ORIGINAL ARTICLE
Year
: 2017  |  Volume : 30  |  Issue : 3  |  Page : 870--875

Role of triphasic MRI in the diagnosis of hepatic focal lesions


Zeinab A Ali1, Tarek F Abd Ella1, Mostafa M Adel2,  
1 Radiology Department, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Radiology Department, National Liver Institute, Menoufia University, Menoufia, Egypt

Correspondence Address:
Mostafa M Adel
Radiology Department, National Liver Institute, Menoufia University, 5 Taiseer Street, Shebein El kom, Menoufia Governorate, 32511
Egypt

Abstract

Objective The aim of this study was to highlight the role of triphasic (dynamic) MRI in the diagnosis of hepatic focal lesions. Background MR of liver depends on the signal characteristics (T1-weighted and T2-weighted signal intensities) and post-Gd imaging. The combination of these imaging techniques provides anatomic and functional imaging information to best detect and diagnose liver pathology. Liver lesions were classified as malignant or benign on the basis of a combination of imaging features such as enhancement pattern/presence of fat, necrosis, and clinical features such as the presence of new/growing liver lesions and uncontrolled systemic disease. Patients and methods The study was conducted in the Hepatic Oncology Unit of the National Liver Institute, Menoufia University on 40 patients with focal hepatic lesions. The study was performed between January 2015 and February 2016. Results Out of the 40 patients studied (28 male and 12 female), 39 were found to have hepatic focal lesions and one had a well-defined hyperechoic area by ultrasound and revealed focal fatty infiltration when examined with dynamic MRI. Their ages ranged from 30 to 71 years, with a mean age of 52 years. Dynamic MRI was successfully performed in all patients, revealing 18 focal lesions to be benign, 21 malignant lesions, and one area of focal fatty infiltration. Conclusion MRI was found to be of considerable value in diagnosing and differentiating between the different cirrhotic hypervascular nodules. This technique can be implemented simply and reliably. It offers the advantages of significantly shorter acquisition times, retrospective thin-section or thick-section reconstruction from the same raw data, improved three-dimensional rendering, and high-quality liver imaging with high intrinsic soft-tissue contrast. It also provides a global overview of the abdomen. Its relative contraindications include renal impairment and sensitivity to IV contrast.



How to cite this article:
Ali ZA, Abd Ella TF, Adel MM. Role of triphasic MRI in the diagnosis of hepatic focal lesions.Menoufia Med J 2017;30:870-875


How to cite this URL:
Ali ZA, Abd Ella TF, Adel MM. Role of triphasic MRI in the diagnosis of hepatic focal lesions. Menoufia Med J [serial online] 2017 [cited 2019 Dec 8 ];30:870-875
Available from: http://www.mmj.eg.net/text.asp?2017/30/3/870/218261


Full Text

 Introduction



Medical innovation regarding the procedures for treatment of focal liver lesions, both primary and metastatic, has shown a significant increase of patient survey in such cases. Therefore, it is fundamental to identify the presence of focal liver lesions early as well as to characterize the nature of such lesions, as benign or malignant, accurately to establish the appropriate treatment planning [1].

MRI represents the current technique of choice in this setting as it is free of ionizing radiation and also because it shows high contrast resolution using several sequences and different types of contrast media. In this regard, the more commonly used MR contrast media are represented by gadolinium chelates, which show an extracellular hepatic distribution, whereas the intracellular contrast media consist of compounds with biliary excretion or those with distribution in the reticuloendothelial system cells [1].

Although liver parenchyma are fed by both the hepatic artery and portal vein, classical hepatocellular carcinoma (HCC) is usually fed by the hepatic artery only. In particular dynamic, computed tomography (CT) or MRI is essential for the diagnosis of liver tumors. Moreover, MRI with tissue-specific MR contrast media and enhanced ultrasonography with real-time high-spatial-resolution imaging have recently become clinically available [2].

Focal nodular hyperplasia (FNH) is the second most common benign hepatic tumor and is believed to be the result of a hyperplastic response of hepatocytes to the presence of a pre-existing vascular malformation. Hepatocellular adenoma is another benign hepatic tumor that occurs predominantly in young women who are receiving oral contraceptives or other steroid medications. MRI is widely used for the differential diagnosis of these lesions. A number of characteristic MRI findings, such as central vascular scar for FNH or signal dropout on fat-suppressed images for hepatocellular adenoma, may be useful, and the dynamic contrast enhancement profile of each tumor when standard gadolinium-based chelates are used can provide additional diagnostic information [3].

The progressive differentiation of a regenerative nodule to a dysplastic nodule, and then to an early-HCC has been well investigated. In this differentiation, the nodule increases its arteriolar supply progressively and reduces the portal vascularization. This vascular change is a crucial step in the carcinogenesis. In view of this consideration, HCC diagnosis with imaging techniques is based on a 'vascular analysis' of enhancing pattern, with an increased signal intensity or 'wash-in' during the arterial phase and a 'wash-out' pattern in the portal or equilibrium phase [4].

Gadolinium-enhanced imaging revealed increased tumor vascularity in the hepatic arterial phase. Increased conspicuity of hypervascular tumors with gadolinium-enhanced images was achieved because of the strong T1-shortening effect of gadolinium chelates injected as a bolus, good T1-weighted contrast resolution of the spoiled gradient-recalled echo sequence, and the use of phased-array multicoil [5].

 Patients and Methods



Study population

A total of 40 patients with focal hepatic lesions were included in this study. The study was performed between January 2015 and February 2016. The study was conducted in the National Liver Institute through the Hepatic Oncology Unit.

Inclusion criteria

Patients known to have a single or multiple hepatic focal lesions detected by ultrasound and/or triphasic CT.

The patients were subjected to the following:

Full clinical assessment including recording of age, sex, and clinical presentation.Laboratory investigations included liver biochemical profile, renal function tests, and α-fetoprotein.Abdominal MRI (precontrast and postcontrast study and diffusion-weighted imaging) was performed by a GE optima MR450w 1.5T (Chicago, USA). The results were compared with laboratory, histopathology (if available), and other previous radiological (ultrasound and/or triphasic CT) findings obtained for all patients.

The MR protocol used

Precontrast imaging included

T1-weighted (T1W) images: repetition time (TR)=10 ms, echo time (TE) = 4.58 ms, matrix 179/320, slice thickness 7–8 mm, slice gap 1–2 mm, and FOV = 355 mmT2-weighted (T2W) images (single-shot free breathing): TR ≥ 445 ms, TE = 26–28 ms, matrix 180–200 × 240 with a field of view = 365, slice thickness 7–8 mm, slice gap 1–2 mmT2 fat suppression sequence: TR ≥ 400 ms, TE = 80 ms, matrix 204 × 384 with a field of view = 365, slice thickness 7–8 mm, slice gap 1–2 mmIn-phase and out-phase gradient echo sequence (dual/fast field echo): TR = 75–100 ms, TE = 4.6 ms for in phase and 2.3 ms for out phase, matrix 143 × 240 with a field of view = 345, slice thickness 7–8 mm, slice gap 0 mmHeavy T2-weighted images: TR = 520 ms, TE = 200 ms, matrix 235/384 with a field of view = 375, slice thickness 7–8 mm, slice gap 1–2 mm.

Dynamic study

Dynamic study was performed after a bolus injection of 0.1 mmol/kg body weight of Gd-DTPA at a rate of 2 ml/s, flushed with 20 ml of sterile 0.9% saline solution from the antecubital vein. The injection of contrast media and saline solution was performed manually. Dynamic imaging using the T1 technique was performed in the triphasic way [arterial phase (16–20 s), portovenous phase (45–60 s), and delayed equilibrium phase (3–5 min)] after administration of contrast media.

Imaging evaluation

Morphological features of each lesion were recorded, including size, shape, margin, signal characteristics, pattern of enhancement in the dynamic imaging, as well as the number and site of the detected focal lesions. Then, the provisional diagnosis was reported.

The results were compared and correlated with other radiological and laboratory results in all patients.

 Results



Out of the 40 patients studied (28 male and 12 female), 39 were found to have hepatic focal lesions and one had a well-defined hyperechoic area by ultrasound and revealed focal fatty infiltration when examined with dynamic MRI. Their ages ranged from 30 to 71 years with a mean age of 52 years. Dynamic MRI was successfully performed in all patients, revealing 18 focal lesions to be benign, 21 malignant lesions, and one area of focal fatty infiltration.

Hepatic focal lesions were divided to the following categories as shown in the chart and table below: malignant tumors (18 cases of HCC, three secondaries), benign tumors (seven cases of hemangioma, one case of abscess, four cases of regeneration nodules and four cases of simple hepatic cysts), two cases of dysplastic nodules, and one case of focal fat infiltration area [Table 1].{Table 1}

Most of the HCC lesions followed pattern 1 (78%), whereas the rest followed different patterns as shown in [Table 2].{Table 2}

All of the hemangioma lesions followed pattern 1 (100%), whereas no other lesions followed different patterns [Table 3].{Table 3}

Most of the metastatic lesions followed pattern 1 (66.5%), whereas the rest of the lesions followed pattern 2 (33.4%) [Table 4].{Table 4}

Most of the regeneration nodules followed pattern 3 (50%), whereas the other lesions followed different patterns [Table 5].{Table 5}

 Discussion



In this study, we noticed that the dynamic study of the majority of HCC lesions displayed the typical early arterial enhancement and contrast washout in the portal and delayed phases. These findings were also similar to the publications of Mannelli and Rosenkrantz [6], who stated that the arterial enhancement (hypervascularity) and delayed hypointensity are considered as essential characteristic features of HCC as the tumor recruits unpaired arteries and sinusoidal capillaries with resultant avid arterial enhancement. Rarely, HCC may remain hyperintense relative to the adjacent liver parenchyma on venous and delayed phase images. However, HCC may be hypovascular to the surrounding liver parenchyma on the immediate gadolinium-enhanced images, and this may be related to the lack of arterialization of the tumor, and in these cases diagnosis by imaging is difficult and biopsy is essential [6].

In the study, vascular invasion into the portal vein was not noticed in any case of HCC lesions. However, Chen et al. [7] who reported that malignant portal vein thrombosis in association with HCC is demonstrated by the same signal intensity and contrast-enhancement pattern as the primary tumor.

Regarding the other cases that are not HCC, we found imaging criteria that suggest cirrhotic features of the liver, and some of the them showed early cirrhotic changes; we found suspicious lesions within the liver, and further investigations and imaging was essential to be sure of the nature of these lesions and to determine how to deal with them.

Regarding hemangiomata cases, however, hemangiomas rarely occur in end-stage cirrhosis, probably because the cirrhosis obliterates existing hemangiomas. When present in the cirrhotic liver, they are often atypical and contain large areas of fibrosis. They do not wash out and instead remain isointense relative to the liver [8].

Radiologic features of 'peripheral nodular enhancement and progressive fill-in' are the most typical of cavernous hemangiomas with contrast enhanced dynamic MRI as reported by Kato et al. [8].

In this study, we have seven cases of hemangioma; all of them were relatively typical in appearance.

Specific CT and MRI findings that are important to recognize the characterization of cystic focal liver lesions are the size of the lesion; the presence and thickness of a wall; the presence of septa, calcifications, or internal nodules; the enhancement pattern; the MR cholangiographic appearance; and the signal intensity spectrum. In addition, access to critical clinical information remains extremely important. The most important clinical parameters defined include age and sex, clinical history, and symptoms [9].

The spectrum of multilocular cystic hepatic lesions includes common and uncommon entities. A lesion's cystic components and internal septa usually reflect its underlying pathologic basis, although imaging findings are not always specific [10].

In this study, there were four cases of hepatic cysts; all have homogeneous very low signal intensity on T1-weighted images and homogeneous very high signal intensity on T2-weighted images with no enhancement after administration of gadolinium chelates as reported by Mortele and Ros [9].

One case of pyogenic liver abscess with criteria similar to that was reported by Mortele and Ros [9]: a multiseptated large abscess can be observed that shows rim and septa enhancement with a characteristic target appearance (the 'double target' sign).

The diagnosis of hypervascular metastatic lesions was more or less easier by knowing that the patients have primary malignancy; hence, this raises the importance of searching for a primary malignancy in cases we find multiple hepatic nodular lesions even in cirrhotic patients.

Murakami and Tsurusaki [11] reported that when the primary lesion is known, metastatic tumors can be easily diagnosed.

Hanna et al. [12] reported that regenerative nodules are the most common cirrhosis-associated hepatocellular nodules.

There were four cases included in the study that showed multiple scattered regeneration nodules. The use of dynamic MRI helps further in the detection of these suspicious nodules by identifying the enhancement pattern of these nodules. This raises the effectiveness and usefulness of dynamic MRI in the evaluation and characterization of hepatic focal lesions.

After contrast administration, regenerative nodules RNs show enhancement similar to the normal liver parenchyma in all phases and they are usually smaller than 2 cm as reported by Mannelli and Rosenkrantz [6].

In our study, there were no lesions diagnosed as FNH; however, FNH is a benign hypervascular tumor arising from the normal liver parenchyma. It occurs primarily in young women; it is solitary in about 75–80% of the patients. The typical imaging findings of FNH are a central scar, intratumoral centrifugal arteries from the center, and the presence of Kupffer cells and the proliferation of cholangiole, among others, which was postulated by Murakami and Tsurusaki [11] [Figure 1], [Figure 2], [Figure 3], [Figure 4].{Figure 1}{Figure 2}{Figure 3}{Figure 4}

 Conclusion



So far, MRI was found to be of considerable value in diagnosing and differentiating between different cirrhotic hypervascular nodules. This technique can be implemented simply and reliably. It offers the advantages of significantly shorter acquisition times, retrospective thin-section or thick-section reconstruction from the same raw data, improved three-dimensional rendering, and high-quality liver imaging with high intrinsic soft-tissue contrast. It also provides a global overview of the abdomen. Its relative contraindications include renal impairment and sensitivity to IV contrast.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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