title: Real T1 relaxation time measurement and diurnal variation analysis of intervertebral discs in a healthy population of 50 volunteers.
abstract: OBJECTIVE
  To measure the real T1 relaxation time of the lumbar intervertebral discs in a young and healthy population, using different inversion recovery times, and assess diurnal variation.
  
  
  METHODS
  Intervertebral discs from D12 to S1 of 50 healthy volunteers from 18 to 25 years old were evaluated twice the same day, in the morning and in the late afternoon. Dedicated MRI sequences with different inversion recovery times (from 100 to 2500ms) were used to calculate the real T1 relaxation time. Three regions of interest (ROIs) were defined in each disc, the middle representing the nucleus pulposus (NP) and the outer parts the annulus fibrosus (AF) anterior and posterior. Diurnal variation and differences between each disc level were analyzed.
  
  
  RESULTS
  T1 mean values in the NP were 1142±12ms in the morning and 1085±13ms in the afternoon, showing a highly significant decrease of 57ms (p<0.001). A highly significant difference between the levels of the spine was found. The mean T1 of the anterior part of the AF was 577±9ms in the morning and 554±8ms in the afternoon. For the posterior part, the mean values were 633±8ms in the morning and 581±7ms in the evening. It shows a highly significant decrease of 23ms for the anterior part and 51ms for the posterior part (all p<0.001).
  
  
  CONCLUSIONS
  T1 mapping is a promising method of intervertebral disc evaluation. Significant diurnal variation and difference between levels of the lumbar spine were demonstrated. A potential use for longitudinal study in post-operative follow up or sport medicine needs to be evaluated.
authors.affiliation: Department of Radiology, HFR Fribourg, Hôpital Cantonal, Switzerland. Electronic address: galleyjulien@gmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Galley
authors.affiliation: Department of Orthopedic Surgery, HFR Fribourg, Hôpital Cantonal, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Maestretti
authors.affiliation: Department of Radiology, HFR Fribourg, Hôpital Cantonal, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Koch
authors.affiliation: Department of Radiology, HFR Fribourg, Hôpital Cantonal, Switzerland.
authors.forename: H-M
authors.initials: HM
authors.lastname: Hoogewoud
mesh_terms: D000293:Adolescent; D000328:Adult; D002940:Circadian Rhythm; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007403:Intervertebral Disc / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D012016:Reference Values; D013997:Time Factors; D055815:Young Adult
keywords: Intervertebral disc; MR; Musculoskeletal; Spine; T1 mapping