Longitudinal relaxation rate ( ) in lung: a systematic review and meta-analysis.

OBJECTIVE

The lung magnetic resonance longitudinal relaxation rate varies with disease but reported values in healthy subjects (HS) also differ markedly between studies.

OBJECTIVE

To evaluate the reported values and variances of observed accounting for field strength , acquisition method, and disease.

MATERIALS AND METHODS

A systematic literature search was performed to identify studies quantifying or its reciprocal . The relationship between field strength and observed R was analysed in all healthy subject data. Data were fit to the heuristic equation . The variances between-study , within-study-between-subject , and within-study-within-subject , in HS were assessed. Linear correlation between observed R and TE was also investigated.

RESULTS

Fifty-nine papers were selected, 50 quantifying R in HS and 20 in disease, representing 1559 human and non-human subjects, with ranging from 0.2 T to 9.4 T. In HS, the result of the fit on all healthy subjects was A = -0.227 ± 0.020 s T, B = 0.923 ± 0.014 s with variance components . The reference values for R at between 0.55 T and 7 T were derived. For inversion recovery with gradient echo readout at 1.5 T, a previously observed negative relationship between and TE was confirmed.

DISCUSSION

We provide reference values for lung across all commonly used field strengths. The variation in HS lung observed reported in different studies in different centres likely reflects methodological differences. Investigators wishing to compare lung values with previous reports should take account of this irreproducibility, and multicentre projects should standardise to minimise between-centre variance.