title: Task-based optimization of flip angle for fibrosis detection in T1-weighted MRI of liver.
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 5 mm, 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.
authors.affiliation: University of Arizona , College of Optical Sciences, 1630 East University Boulevard, Tucson, Arizona 85719, United States.
authors.forename: Jonathan F
authors.initials: JF
authors.lastname: Brand
authors.affiliation: University of Arizona, College of Optical Sciences, 1630 East University Boulevard, Tucson, Arizona 85719, United States; University of Arizona, College of Medicine, Department of Medical Imaging, P.O. Box 245067 Tucson, Arizona 85724-5067, United States.
authors.forename: Lars R
authors.initials: LR
authors.lastname: Furenlid
authors.affiliation: University of Arizona , College of Medicine, Department of Medical Imaging, P.O. Box 245067 Tucson, Arizona 85724-5067, United States.
authors.forename: Maria I
authors.initials: MI
authors.lastname: Altbach
authors.affiliation: University of Arizona , College of Medicine, Department of Medical Imaging, P.O. Box 245067 Tucson, Arizona 85724-5067, United States.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Galons
authors.affiliation: University of Arizona , College of Medicine, Department of Pathology, 1501 North Campbell Avenue, Tucson, Arizona 85724, United States.
authors.forename: Achyut
authors.initials: A
authors.lastname: Bhattacharyya
authors.affiliation: University of Arizona , College of Medicine, Department of Medical Imaging, P.O. Box 245067 Tucson, Arizona 85724-5067, United States.
authors.forename: Puneet
authors.initials: P
authors.lastname: Sharma
authors.affiliation: University of Arizona , College of Medicine, Department of Pathology, 1501 North Campbell Avenue, Tucson, Arizona 85724, United States.
authors.forename: Tulshi
authors.initials: T
authors.lastname: Bhattacharyya
authors.affiliation: University of Arizona , College of Medicine, Department of Medical Imaging, P.O. Box 245067 Tucson, Arizona 85724-5067, United States.
authors.forename: Ali
authors.initials: A
authors.lastname: Bilgin
authors.affiliation: University of Arizona , College of Medicine, Department of Medical Imaging, P.O. Box 245067 Tucson, Arizona 85724-5067, United States.
authors.forename: Diego R
authors.initials: DR
authors.lastname: Martin
keywords: MRI; hepatic fibrosis; hotelling observer; liver; magnetic resonance imaging; optimization; texture analysis