title: A novel method for quantitative monitoring of transplanted islets of langerhans by positive contrast magnetic resonance imaging.
abstract: The Automatic Quantitative Ultrashort Echo Time imaging (AQUTE) protocol for serial MRI allows quantitative in vivo monitoring of iron labeled pancreatic islets of Langerhans transplanted into the liver, quantifying graft implantation and persistence in a rodent model. Rats (n = 14), transplanted with iron oxide loaded cells (0-4000 islet equivalents, IEQ), were imaged using a 3D radial ultrashort echo time difference technique (dUTE) on a Siemens MAGNETOM 3T clinical scanner up to 5 months postsurgery. In vivo 3D dUTE images gave positive contrast from labeled cells, suppressing liver signal and small vessels, allowing automatic quantification. Position of labeled islet clusters was consistent over time and quantification of hyperintense pixels correlated with the number of injected IEQs (R² = 0.898, p < 0.0001), and showed persistence over time (5 months posttransplantation). Automatic quantification was superior to standard imaging and manual counting methods, due to the uniform suppressed background and high contrast, resulting in significant timesavings, reproducibility and ease of quantification. Three-dimensional coverage of the whole liver in the absence of cardiac/respiratory artifact provided further improvement over conventional imaging. This imaging protocol reliably quantifies transplanted islet mass and has high translational potential to clinical studies of transplanted pancreatic islets.
authors.affiliation: Department of Radiology Cell Isolation and Transplant Center, Department of Surgery, University of Geneva School of Medicine and Geneva University Hospitals, Geneva, Switzerland. Lindsey.crowe@hcuge.ch
authors.forename: L A
authors.initials: LA
authors.lastname: Crowe
authors.forename: F
authors.initials: F
authors.lastname: Ris
authors.forename: S
authors.initials: S
authors.lastname: Nielles-Vallespin
authors.forename: P
authors.initials: P
authors.lastname: Speier
authors.forename: S
authors.initials: S
authors.lastname: Masson
authors.forename: M
authors.initials: M
authors.lastname: Armanet
authors.forename: P
authors.initials: P
authors.lastname: Morel
authors.forename: C
authors.initials: C
authors.lastname: Toso
authors.forename: D
authors.initials: D
authors.lastname: Bosco
authors.forename: T
authors.initials: T
authors.lastname: Berney
authors.forename: J-P
authors.initials: JP
authors.lastname: Vallee
mesh_terms: D000818:Animals; D003287:Contrast Media; D007515:Islets of Langerhans / Q000473:pathology*; D016381:Islets of Langerhans Transplantation; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results
chemical_list: D003287:Contrast Media