Abstract
Chronic liver disease is a worldwide health problem, and hepatic fibrosis (HF) is one of the hallmarks of the disease. The current reference standard for diagnosing HF is biopsy followed by pathologist examination; however, this is limited by sampling error and carries a risk of complications. Pathology diagnosis of HF is based on textural change in the liver as a lobular collagen network that develops within portal triads. The scale of collagen lobules is characteristically in the order of 1 to 5mm, which approximates the resolution limit of in vivo gadolinium-enhanced magnetic resonance imaging in the delayed phase. We use MRI of formalin-fixed human ex vivo liver samples as phantoms that mimic the textural contrast of in vivo Gd-MRI. We have developed a local texture analysis that is applied to phantom images, and the results are used to train model observers to detect HF. The performance of the observer is assessed with the area-under-the-receiver-operator-characteristic curve (AUROC) as the figure-of-merit. To optimize the MRI pulse sequence, phantoms were scanned with multiple times at a range of flip angles. The flip angle that was associated with the highest AUROC was chosen as optimal for the task of detecting HF.
Highlights
Chronic liver disease (CLD) is a widespread health concern that represents a common disease pathway for a number of important etiologies, including nonalcoholic steatohepatitis (NASH), alcoholic cirrhosis, and viral hepatitis.[1,2]. These diseases lead to inflammation and damage, usually first involving the portal triad region surrounding the hepatic lobules, resulting in the deposition of collagen scar tissue in the extracellular matrix (ECM), a process diagnosed as hepatic fibrosis (HF).[1,3,4,5]
We found that a Hotelling observer working with 2-D discrete circular autocorrelation (2DCC) is capable of distinguishing whether local regions drawn from an F0∕F1 or an F4 liver while requiring a modest amount of training data
The F0 sample showed no sign of fibrosis, whereas the F1 biopsy showed early fibrosis forming around the portal veins
Summary
The current reference standard for CLD diagnosis and HF staging is needle biopsy of the liver.[6,9,10,11] Biopsy provides cellular-resolution images that make it possible for a pathologist to identify fibrotic tissue and stage severity. When providing a diagnosis of HF, a pathologist will report severity using a numerical staging system based on one of several alternative scoring methods. Two of these techniques are the “Ishak score,” using a seven-point scale, and the “METAVIR score,” which uses a five-point severity scale.[3,9] Each scale has metrics for determining the severity of HF and each institution or medical organization adopts a particular scale
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