High signal intensity of intervertebral calcified disks on T1-weighted MR images resulting from fat content.
OBJECTIVE
To explain a cause of high signal intensity on T1-weighted MR images in calcified intervertebral disks associated with spinal fusion.


METHODS
Magnetic resonance and radiological examinations of 13 patients were reviewed, presenting one or several intervertebral disks showing a high signal intensity on T1-weighted MR images, associated both with the presence of calcifications in the disks and with peripheral fusion of the corresponding spinal segments. Fusion was due to ligament ossifications (n=8), ankylosing spondylitis (n=4), or posterior arthrodesis (n=1). Imaging files included X-rays and T1-weighted MR images in all cases, T2-weighted MR images in 12 cases, MR images with fat signal suppression in 7 cases, and a CT scan in 1 case. Histological study of a calcified disk from an anatomical specimen of an ankylosed lumbar spine resulting from ankylosing spondylitis was examined.


RESULTS
The signal intensity of the disks was similar to that of the bone marrow or of perivertebral fat both on T1-weighted MR images and on all sequences, including those with fat signal suppression. In one of these disks, a strongly negative absorption coefficient was focally measured by CT scan, suggesting a fatty content. The histological examination of the ankylosed calcified disk revealed the presence of well-differentiated bone tissue and fatty marrow within the disk.


CONCLUSIONS
The high signal intensity of some calcified intervertebral disks on T1-weighted MR images can result from the presence of fatty marrow, probably related to a disk ossification process in ankylosed spines.
Cliniques Universitaires St Luc, Université Catholique de Louvain, 10 av Hippocrate, 1200 Brussels, Belgium. malghem@rdgn.ucl.ac.be
Jacques
J
Malghem
Frédéric E
FE
Lecouvet
Robert
R
François
Bruno C
BC
Vande Berg
Thierry
T
Duprez
Guy
G
Cosnard
Baudouin E
BE
Maldague
D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000473:pathology*; D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000000981:diagnostic imaging* / Q000209:etiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007403:Intervertebral Disc / Q000000981:diagnostic imaging* / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D012815:Signal Processing, Computer-Assisted; D013123:Spinal Fusion / Q000009:adverse effects; D013167:Spondylitis, Ankylosing / Q000150:complications* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed