Maria Filomena Santarelli1, Antonella Meloni2, Daniele De Marchi2, Laura Pistoia2, Antonella Quarta3, Anna Spasiano4, Luigi Landini2,5, Alessia Pepe2, Vincenzo Positano6. 1. CNR Institute of Clinical Physiology, Pisa, Italy. 2. Fondazione CNR Regione Toscana "G. Monasterio", Via Moruzzi, 1, 56124, Pisa, Italy. 3. Ematologia, Ospedale "A. Perrino", Brindisi, Italy. 4. UOS Malattie Rare Del Globulo Rosso, AORN Cardarelli, Naples, Italy. 5. Department of Information Engineering, University of Pisa, Pisa, Italy. 6. Fondazione CNR Regione Toscana "G. Monasterio", Via Moruzzi, 1, 56124, Pisa, Italy. vincenzo.positano@ftgm.it.
Abstract
OBJECTIVES: To propose a method for estimating pancreatic relaxation rate, R2*, from conventional multi-echo MRI, based on the nonlinear fitting of the acquired magnitude signal decay to MR signal models that take into account both the signal oscillations induced by fat and the different R2* values of pancreatic parenchyma and fat. MATERIALS AND METHODS: Single-peak fat (SPF) and multi-peak fat (MPF) models were introduced. Single-R2* and dual-R2* assumptions were considered as well. Analyses were conducted on simulated data and 20 thalassemia major patients. RESULTS: Simulations revealed the ability of the MPF model to correctly estimate the R2* value in a large range of fat fractions and R2* values. From the comparison between the results obtained with a single R2* value for water and fat and the dual-R2* approach, the latter is more accurate in both water R2* and fat fraction estimation. In patient's data analysis, a strong concordance was found between SPF and MPF estimated data with measurements done with manual signal correction and from fat-saturated images. The MPF method showed better reproducibility. CONCLUSION: The MPF dual-R2* approach improves reproducibility and reduces image analysis time in the assessment of pancreatic R2* value in patients with iron overload.
OBJECTIVES: To propose a method for estimating pancreatic relaxation rate, R2*, from conventional multi-echo MRI, based on the nonlinear fitting of the acquired magnitude signal decay to MR signal models that take into account both the signal oscillations induced by fat and the different R2* values of pancreatic parenchyma and fat. MATERIALS AND METHODS: Single-peak fat (SPF) and multi-peak fat (MPF) models were introduced. Single-R2* and dual-R2* assumptions were considered as well. Analyses were conducted on simulated data and 20 thalassemia major patients. RESULTS: Simulations revealed the ability of the MPF model to correctly estimate the R2* value in a large range of fat fractions and R2* values. From the comparison between the results obtained with a single R2* value for water and fat and the dual-R2* approach, the latter is more accurate in both water R2* and fat fraction estimation. In patient's data analysis, a strong concordance was found between SPF and MPF estimated data with measurements done with manual signal correction and from fat-saturated images. The MPF method showed better reproducibility. CONCLUSION: The MPF dual-R2* approach improves reproducibility and reduces image analysis time in the assessment of pancreatic R2* value in patients with iron overload.
Entities:
Keywords:
Fat infiltration; Iron overload; Multi-echo MRI; Pancreas; R2*; Thalassemia
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