title: R2 relaxometry with MRI for the quantification of tissue iron overload in beta-thalassemic patients.
abstract: OBJECTIVE
  To evaluate the usefulness of a time-efficient MRI method for the quantitative determination of tissue iron in the liver and heart of beta-thalassemic patients using spin-spin relaxation rate, R2, measurements.
  
  
  METHODS
  Images were obtained at 1.5 T from aqueous Gd-DTPA solutions (0.106-8 mM) and from the liver and heart of 46 beta-thalassemic patients and 10 controls. The imaging sequence used was a respiratory-triggered 16-echo Carr-Purcell-Meiboom-Gill (CPMG) spin-echo (SE) pulse sequence (TR = 2000 msec, TE(min) = 5 msec, echo spacing (ES) = 5 msec, matrix = 192 x 256, slice thickness = 10 mm). Liver iron concentration (LIC) measurements were obtained for 22 patients through biopsy specimens excised from the relevant liver segment. Biopsy specimens were also evaluated regarding iron grade and fibrosis. Serum ferritin (SF) measurements were obtained in all patients.
  
  
  RESULTS
  A statistically significant difference was found between patients and healthy controls in mean liver (P < 0.004) and myocardium (P < 0.004) R2 values. The R2 values correlated well with Gd DTPA concentration (r = 0.996, P < 0.0001) and LIC (r = 0.874, P < 0.0001). A less significant relationship (r = 0.791, P < 0.0001) was found between LIC measurements and SF levels. R2 measurements appear to be significantly affected (P = 0.04) by different degrees of hepatic fibrosis. The patients' liver R2 values did not correlate with myocardial R2 values (r = 0.038, P < 0.21).
  
  
  CONCLUSIONS
  Tissue iron deposition in beta-thalassemic patients may be adequately quantified using R2 measurements obtained with a 16-echo MRI sequence with short ES (5 msec), even in patients with a relatively increased iron burden.
authors.affiliation: Second Department of Radiology, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Efthymia
authors.initials: E
authors.lastname: Alexopoulou
authors.forename: Fotini
authors.initials: F
authors.lastname: Stripeli
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Baras
authors.forename: Ioannis
authors.initials: I
authors.lastname: Seimenis
authors.forename: Antonis
authors.initials: A
authors.lastname: Kattamis
authors.forename: Vasilis
authors.initials: V
authors.lastname: Ladis
authors.forename: Efstathios
authors.initials: E
authors.lastname: Efstathopoulos
authors.forename: Elias N
authors.initials: EN
authors.lastname: Brountzos
authors.forename: Alexis D
authors.initials: AD
authors.lastname: Kelekis
authors.forename: Nikolaos L
authors.initials: NL
authors.lastname: Kelekis
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D002648:Child; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D005293:Ferritins / Q000097:blood / Q000378:metabolism; D006801:Humans; D019190:Iron Overload / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D011336:Probability; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012815:Signal Processing, Computer-Assisted; D013318:Stroke Volume; D017086:beta-Thalassemia / Q000175:diagnosis*
chemical_list: D005293:Ferritins