Quantifiable Imaging Biomarkers for Evaluation of the Posterior Cruciate Ligament Using 3-T Magnetic Resonance Imaging: A Feasibility Study.
BACKGROUND
Quantitative magnetic resonance imaging (MRI) techniques, such as T2 and T2 star (T2*) mapping, have been used to evaluate ligamentous tissue in vitro and to identify significant changes in structural integrity of a healing ligament. These studies lay the foundation for a clinical study that uses quantitative mapping to evaluate ligaments in vivo, particularly the posterior cruciate ligament (PCL). To establish quantitative mapping as a clinical tool for identifying and evaluating chronic or acute PCL injuries, T2 and T2* values first must be determined for an asymptomatic population.


OBJECTIVE
To quantify T2 and T2* mapping properties, including texture variables (entropy, variance, contrast, homogeneity), of the PCL in an asymptomatic population. It was hypothesized that biomarker values would be consistent throughout the ligament, as measured across 3 clinically relevant subregions (proximal, middle, and distal thirds) in the asymptomatic cohort.


METHODS
Cross-sectional study; Level of evidence, 4.


METHODS
Unilateral knee MRI scans were acquired for 25 asymptomatic subjects with a 3.0-T MRI system using T2 and T2* mapping sequences in the sagittal plane. The PCL was manually segmented and divided into thirds (proximal, middle, and distal). Summary statistics for T2 and T2* values were calculated. Intra- and interrater reliability was assessed across 3 raters to 2 time points.


RESULTS
The asymptomatic PCL cohort had mean T2 values of 36.7, 29.2, and 29.6 ms in the distal, middle, and proximal regions, respectively. The distal PCL exhibited significantly higher mean, variance, and contrast and lower homogeneity of T2 values than the middle and proximal subregions (P < .05). T2* results exhibited substantial positive skew and were therefore presented as median and quartile (Q) values. Median T2* values were 7.3 ms (Q1-Q3, 6.8-8.9 ms), 7.3 ms (Q1-Q3, 7.0-8.5 ms), and 7.3 ms (Q1-Q3, 6.4-8.2 ms) in the distal, middle, and proximal subregions, respectively.


CONCLUSIONS
This is the first study to identify T2 and T2* mapping values, and their texture variables, for the asymptomatic PCL. The distal third of the PCL had significantly greater T2 values than the proximal or middle thirds.


CONCLUSIONS
T2 and T2* values of the asymptomatic PCL can provide a baseline for comparison with acute and chronic PCL injuries in future studies.
Steadman Philippon Research Institute, Vail, Colorado, USA.
Katharine J
KJ
Wilson
Steadman Philippon Research Institute, Vail, Colorado, USA.
Rachel K
RK
Surowiec
Steadman Philippon Research Institute, Vail, Colorado, USA.
Charles P
CP
Ho
Steadman Philippon Research Institute, Vail, Colorado, USA.
Brian M
BM
Devitt
Commonwealth Scientific and Industrial Research Organization, Digital Productivity and Services Flagship, The Australian eHealth Research Centre, Queensland, Australia.
Jurgen
J
Fripp
Steadman Philippon Research Institute, Vail, Colorado, USA.
W Sean
WS
Smith
Steadman Philippon Research Institute, Vail, Colorado, USA.
Ulrich J
UJ
Spiegl
Steadman Philippon Research Institute, Vail, Colorado, USA.
Grant J
GJ
Dornan
Steadman Philippon Research Institute, Vail, Colorado, USA.; The Steadman Clinic, Vail, Colorado, USA.
Robert F
RF
LaPrade
MRI; T2 mapping; T2* mapping; asymptomatic; posterior cruciate ligament