title: Chemical shift imaging at 3 Tesla: effect of echo time on assessing bone marrow abnormalities.
abstract: OBJECTIVE
  Our purpose is to test the effect of varied in-phase (IP) and opposed-phase (OP) sequence order on characterizing marrow signal changes at 3T.
  
  
  METHODS
  The study was HIPAA compliant and IRB approved. Informed consent was waived. At 3T, IP and OP sequences were acquired in three patients with biopsy-proven osteosarcomas, using two methods: approach 1 (OP acquisition before IP acquisition) and approach 2 (OP after IP). Signal intensity (SI) measurements in 12 locations of biopsy-proven osteosarcoma and in six locations with normal bone marrow were performed independently by two experienced musculoskeletal radiologists. The signal intensity ratio (SIR) was measured within the marrow where there was T1 signal lower than skeletal muscle. A SIR < 20 % on the OP compared with IP imaging was considered positive for marrow replacement, while SIR > = 20 % was considered negative. Interobserver agreement was measured by the Lin concordance correlation coefficient (CCC).
  
  
  RESULTS
  In 75 % (18/24) of locations within the biopsy-proven tumors, the SIR was >20 % (SI drop more than 20 % in OP compared to IP) using approach 2 and in 100 % (24/24) of the locations the SIR was <20 % (SI drop less than 20 % in OP compared to IP) using approach 1, indicating a high percentage of false-negative results by approach 2, and no false-negative results with approach 1. There was good agreement between observer measurement (CCC = 0.96).
  
  
  CONCLUSIONS
  At 3T, the OP sequence should be acquired prior to the IP sequence, because susceptibility artifacts on a later-acquired OP sequence may lead to an erroneous interpretation of marrow signal abnormalities.
authors.affiliation: The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Medical Institutions, 601 North Wolfe Street, Baltimore, MD, 21287, USA, fdelgra1@jhmi.edu.
authors.forename: F
authors.initials: F
authors.lastname: Del Grande
authors.forename: Ty
authors.initials: T
authors.lastname: Subhawong
authors.forename: A
authors.initials: A
authors.lastname: Flammang
authors.forename: L M
authors.initials: LM
authors.lastname: Fayad
mesh_terms: D000328:Adult; D016477:Artifacts; D001853:Bone Marrow / Q000473:pathology*; D019046:Bone Marrow Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015588:Observer Variation; D012516:Osteosarcoma / Q000473:pathology*; D015203:Reproducibility of Results; D055815:Young Adult
references.citation: AJR Am J Roentgenol. 1997 Nov;169(5):1439-47
references.pmid: 9353477
references.citation: Radiographics. 2009 Sep-Oct;29(5):1253-77
references.pmid: 19755595
references.citation: AJNR Am J Neuroradiol. 2006 Jun-Jul;27(6):1183-8
references.pmid: 16775260
references.citation: Radiology. 2004 Jun;231(3):711-6
references.pmid: 15118113
references.citation: AJR Am J Roentgenol. 2006 Jun;186(6):1524-32
references.pmid: 16714640
references.citation: Radiographics. 1998 Nov-Dec;18(6):1425-40
references.pmid: 9821192
references.citation: Radiology. 1995 Apr;195(1):285-6
references.pmid: 7892487
references.citation: Radiology. 2006 Apr;239(1):174-80
references.pmid: 16507752
references.citation: Radiology. 2005 Nov;237(2):590-6
references.pmid: 16244268
references.citation: Radiology. 2008 Jul;248(1):140-7
references.pmid: 18566172
references.citation: AJR Am J Roentgenol. 2009 Sep;193(3 Suppl):S1-4, Quiz S5-9
references.pmid: 19696238
references.citation: J Magn Reson Imaging. 2004 Dec;20(6):1020-4
references.pmid: 15558548
references.citation: Eur Radiol. 2002 Jul;12(7):1811-8
references.pmid: 12111073