title: A novel semiautomatic parenchyma extraction method for improved MRI R2* relaxometry of iron loaded liver.
abstract: OBJECTIVE
  To propose and evaluate an automatic method of extracting parenchyma from a manually delineated whole liver for the R2* measurement of iron load.
  
  
  METHODS
  In all, 108 transfusion-dependent patients with a wide range of hepatic iron content were scanned with a multiecho gradient-echo sequence. The R2* was measured by fitting the average signal of liver parenchyma, extracted by the proposed semiautomatic parenchyma extraction (SAPE), traditional manually delineated multiple regions-of-interest (mROIs), and T2* thresholding methods to the noise-corrected monoexponential model. The R2* measurement accuracy of the SAPE method was evaluated through simulation; the intra- and interobserver reproducibility of SAPE, mROI, and T2* thresholding were assessed from the in vivo data using coefficient of variation (CoV).
  
  
  RESULTS
  In the simulation, the mean absolute percentage error of R2* measurement using SAPE was 0.23% (range 0.01%-1.09%). In vivo study, the CoVs of intra- and interobserver reproducibility were 0.83%, 1.39% for SAPE, 3.63%, 6.28% for mROI, and 1.62%, 2.66% for T2* thresholding, respectively.
  
  
  CONCLUSIONS
  The SAPE method provides an accurate and reliable approach to assessing the overall hepatic iron content. The improved magnetic resonance imaging (MRI) R2* reproducibility using the SAPE method may lead to more accurate tissue characterization and increased diagnostic confidence.
authors.affiliation: School of Biomedical Engineering, Southern Medical University, Guangzhou, China.
authors.forename: Yanqiu
authors.initials: Y
authors.lastname: Feng
authors.forename: Meiyan
authors.initials: M
authors.lastname: Feng
authors.forename: Huashuai
authors.initials: H
authors.lastname: Gao
authors.forename: Xinyuan
authors.initials: X
authors.lastname: Zhang
authors.forename: Xuegang
authors.initials: X
authors.lastname: Xin
authors.forename: Qianjin
authors.initials: Q
authors.lastname: Feng
authors.forename: Wufan
authors.initials: W
authors.lastname: Chen
authors.forename: Taigang
authors.initials: T
authors.lastname: He
mesh_terms: D000465:Algorithms; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007501:Iron / Q000378:metabolism; D019190:Iron Overload / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D008099:Liver / Q000378:metabolism / Q000473:pathology*; D008107:Liver Diseases / Q000209:etiology / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015588:Observer Variation; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D065227:Transfusion Reaction; D055815:Young Adult
chemical_list: D015415:Biomarkers; D007501:Iron
keywords: R2*; liver iron; magnetic resonance imaging; semiautomatic parenchyma extraction