title: Is the T1ρ MRI profile of hyaline cartilage in the normal hip uniform?
abstract: BACKGROUND
  T1ρ MRI is an imaging technique sensitive to proteoglycan (PG) content of hyaline cartilage. However, normative T1ρ values have not been established for the weightbearing cartilage of the hip, and it is not known whether it is uniform or whether there is topographic variation. Knowledge of the T1ρ profile of hyaline cartilage in the normal hip is important for establishing a baseline against which comparisons can be made to experimental and clinical arthritic subjects.
  
  
  OBJECTIVE
  In this diagnostic study, we determined (1) the T1ρ MRI values of hyaline cartilage of the normal hip; and (2) whether the T1ρ MRI profile of the normal hip hyaline cartilage is uniform.
  
  
  METHODS
  Fourteen asymptomatic volunteers (11 men, three women; mean age, 35 years) prospectively underwent 1.5-T T1ρ MRI of a single hip. The weightbearing hyaline cartilage bilayer of the acetabulum and femoral head was evaluated on sagittal images and segmented into four zones: (1) anterior; (2) anterosuperior; (3) posterosuperior; and (4) and posterior. For the full region of interest and within each zone and each sagittal slice, we calculated the mean T1ρ relaxation value, a parameter that indirectly quantifies PG content, where T1ρ is inversely related to PG concentration.
  
  
  RESULTS
  There was variation in the T1ρ relaxation values depending on zone (anterior to posterior) and slice (medial to lateral). When combining the most anterior quadrants (Zones 1 and 2), the T1ρ relaxation values were lower than those in the combined posterior quadrants (Zones 3 and 4) (30.4 msec versus 32.2 msec, respectively; p = 0.002), reflecting higher PG concentration. There was a difference between the T1ρ relaxation values of the sagittal slices (p = 0.038), most pronounced anteriorly in Zone 1 (26.6 msec, p = 0.001). With a selective combination of zones and slices, there were lower mean T1ρ values in the anterolateral-most region compared with the remainder of the weightbearing portion of the hip (28.6 msec versus 32.2 msec, respectively; p = 0.001).
  
  
  CONCLUSIONS
  The T1ρ profile of normal hyaline cartilage of the hip is not uniform with the topographic differences identified suggesting regional variations in PG concentration. This study, through determination of lower T1ρ relaxation values, suggests inherently greater PG concentrations in the more anterolateral region of the normal hip hyaline cartilage. Furthermore, it demonstrates that T1ρ MRI has the ability to detect even subtle, microscopic local differences in hyaline cartilage composition. This technique has the potential to facilitate basic science and clinical research by serving as a noninvasive surrogate or biomarker of cartilage health and thus may be added to the growing repertoire of advanced, biochemical MRI techniques for evaluating hyaline cartilage.
authors.affiliation: Department of Medical Imaging, The Ottawa Hospital, Ottawa, ON, Canada.
authors.forename: Kawan S
authors.initials: KS
authors.lastname: Rakhra
authors.forename: Arturo
authors.initials: A
authors.lastname: Cárdenas-Blanco
authors.forename: Gerd
authors.initials: G
authors.lastname: Melkus
authors.forename: Mark E
authors.initials: ME
authors.lastname: Schweitzer
authors.forename: Ian G
authors.initials: IG
authors.lastname: Cameron
authors.forename: Paul E
authors.initials: PE
authors.lastname: Beaulé
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D051457:Hyaline Cartilage / Q000737:chemistry / Q000473:pathology*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011509:Proteoglycans / Q000032:analysis; D012016:Reference Values
chemical_list: D011509:Proteoglycans
references.citation: Magn Reson Med. 2007 Apr;57(4):803-5
references.pmid: 17390362
references.citation: Arthroscopy. 2005 Apr;21(4):385-93
references.pmid: 15800516
references.citation: Acad Radiol. 2002 Dec;9(12):1388-94
references.pmid: 12553350
references.citation: J Magn Reson Imaging. 2008 Jul;28(1):227-35
references.pmid: 18581346
references.citation: Proc Natl Acad Sci U S A. 2001 Oct 23;98(22):12479-84
references.pmid: 11606754
references.citation: J Oral Maxillofac Surg. 1995 Oct;53(10):1182-92
references.pmid: 7562173
references.citation: J Anat. 1994 Jun;184 ( Pt 3):477-92
references.pmid: 7928637
references.citation: Magn Reson Med. 2009 Oct;62(4):896-901
references.pmid: 19645008
references.citation: J Magn Reson Imaging. 2003 Jan;17(1):114-21
references.pmid: 12500280
references.citation: J Orthop Res. 2008 Mar;26(3):281-91
references.pmid: 17876836
references.citation: Clin Orthop Relat Res. 2004 Oct;(427 Suppl):S69-77
references.pmid: 15480079
references.citation: Magn Reson Imaging. 2013 Sep;31(7):1129-36
references.pmid: 23684960
references.citation: Magn Reson Med. 2001 Sep;46(3):419-23
references.pmid: 11550230
references.citation: Semin Musculoskelet Radiol. 2008 Sep;12(3):212-22
references.pmid: 18850503
references.citation: J Bone Joint Surg Am. 2004 Oct;86(10):2294-8
references.pmid: 15466743
references.citation: Osteoarthritis Cartilage. 2006;14 Suppl A:A76-86
references.pmid: 16716605
references.citation: J Bone Joint Surg Am. 2010 Nov 3;92(15):2557-69
references.pmid: 21048174
references.citation: Osteoarthritis Cartilage. 2013 Oct;21(10):1425-35
references.pmid: 23891696
references.citation: Semin Musculoskelet Radiol. 2004 Dec;8(4):355-68
references.pmid: 15643574
references.citation: Invest Radiol. 2000 Oct;35(10):622-38
references.pmid: 11041156
references.citation: Instr Course Lect. 2012;61:253-62
references.pmid: 22301237
references.citation: Radiology. 2007 Feb;242(2):441-9
references.pmid: 17255415
references.citation: Magn Reson Med. 2009 Jun;61(6):1310-8
references.pmid: 19319904
references.citation: Radiology. 2003 Feb;226(2):382-6
references.pmid: 12563129
references.citation: Osteoarthritis Cartilage. 2002 Nov;10(11):838-44
references.pmid: 12435327
references.citation: Magn Reson Med. 1997 Dec;38(6):863-7
references.pmid: 9402184
references.citation: J Bone Joint Surg Br. 2012 Sep;94(9):1187-92
references.pmid: 22933489
references.citation: Osteoarthritis Cartilage. 2009 Jan;17(1):19-25
references.pmid: 18614381
references.citation: AJR Am J Roentgenol. 2005 Oct;185(4):899-914
references.pmid: 16177408
references.citation: AJR Am J Roentgenol. 2004 Jan;182(1):167-72
references.pmid: 14684534
references.citation: Magn Reson Med. 2005 Nov;54(5):1087-93
references.pmid: 16200568
references.citation: J Magn Reson Imaging. 2007 Jul;26(1):165-71
references.pmid: 17659572
references.citation: Radiology. 2005 Aug;236(2):588-92
references.pmid: 15972331
references.citation: Eur Cell Mater. 2007 May 15;13:76-86
references.pmid: 17506024
references.citation: J Anat. 1978 May;126(Pt 1):145-55
references.pmid: 649495
references.citation: J Bone Joint Surg Am. 2006 Jul;88(7):1540-8
references.pmid: 16818980
references.citation: Osteoarthritis Cartilage. 2006 Nov;14(11):1087-90
references.pmid: 16901724
references.citation: Eur J Radiol. 2012 Nov;81(11):3420-5
references.pmid: 22591759
references.citation: Front Biosci. 1999 Oct 15;4:D662-70
references.pmid: 10525481
references.citation: AJR Am J Roentgenol. 2006 Dec;187(6):1412-9
references.pmid: 17114529