Assessment of the skeletal status by MR relaxometry techniques of the lumbar spine: comparison with dual X-ray absorptiometry.
OBJECTIVE
To measure lumbar spine T2*, T2, T2' and T1 MR relaxometry parameters and compare them with lumbar spine bone mineral density (BMD) in a group of postmenopausal women.


METHODS
Lumbar spine T2*, T2, T2' and T1 MR relaxometry parameters and BMD values were assessed in 101 postmenopausal women (mean age: 61.8 +/- 7.1 (1 S.D.) years); of them 63 referred to as control subjects (group A, BMD T-scores > or = -2.5 S.D.) and 38 as osteoporotic (group B, BMD T-scores < -2.5 S.D.). All magnetic resonance imaging (MRI) examinations were performed on an 1.5 T imaging system using: (a) a 2D single slice multi echo (32 echoes) gradient echo (MEGRE) sequence (TR/TE1/TE32/FA: 160/2.7/74.93 ms/25 degrees for the T2* measurement, (b) a respiratory gated 2D single slice Multi Echo (16 echoes) Spin Echo (MESE) sequence (TR/TE1/TE16/FA: 2000-2500/22.5/360 ms/90 degrees) for the T2 measurement and (c) a 2D single slice multi TI (18 repeats) turbo Fast Low Angle Shot (turbo FLASH) sequence (TR/TE/TI1/TI16/FA: 11/4.2/10/5000 ms/10 degrees) for the T1 measurement. T2' was calculated from its definition equation: (1/T2' = 1/T2* - 1/T2). Lumbar spine BMD was assessed using DXA.


RESULTS
All measured parameters showed statistically significant differences between groups A and B (from P < 0.05 to <0.001). All parameters showed significant associations with subject's age ranging from r = 0.245 (P < 0.05) for the T2 up to r = 0.377 (P < 0.001) for the T2*. All parameters showed significant associations with subject's BMD measurements ranging from r = -0.184 (P < 0.05) for the R1 = (1/T1) up to r = -0.345 (P < 0.0005) for the T2.


CONCLUSIONS
Among the MR relaxometry parameters studied, T2* and T2 showed better discrimination of patients with osteoporosis from control subjects.
Maris
Thomas G
TG
Departement of Medical Physics, Faculty of Medicine, University Hospital of Heraklion, P.O. Box 1352, 71110 Stavrakia, Heraklion, Crete, Greece. tmaris@med.uoc.gr
Damilakis
John
J
Sideri
Liana
L
Deimling
Michael
M
Papadokostakis
Georgios
G
Papakonstantinou
Olympia
O
Gourtsoyiannis
Nikos
N
D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D000368:Aged; D000886:Anthropometry; D015519:Bone Density / Q000502:physiology; D016022:Case-Control Studies; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D016014:Linear Models; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000175:diagnosis*; D019047:Phantoms, Imaging; D017698:Postmenopause / Q000502:physiology; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
D003287:Contrast Media; D019786:Gadolinium DTPA