Time-Dependent Changes in T1 during Fracture Healing in Juvenile Rats: A Quantitative MR Approach

PLoS One. 2016 Nov 10;11(11):e0164284. doi: 10.1371/journal.pone.0164284. eCollection 2016.

Abstract

Quantitative magnetic resonance imaging (qMRI) offers several advantages in imaging and determination of soft tissue alterations when compared to qualitative imaging techniques. Although applications in brain and muscle tissues are well studied, its suitability to quantify relaxation times of intact and injured bone tissue, especially in children, is widely unknown. The objective observation of a fracture including its age determination can become of legal interest in cases of child abuse or maltreatment. Therefore, the aim of this study is the determination of time dependent changes in intact and corresponding injured bones in immature rats via qMRI, to provide the basis for an objective and radiation-free approach for fracture dating. Thirty-five MR scans of 7 Sprague-Dawley rats (male, 4 weeks old, 100 ± 5 g) were acquired on a 3T MRI scanner (TimTrio, Siemens AG, Erlangen, Germany) after the surgical infliction of an epiphyseal fracture in the tibia. The images were taken at days 1, 3, 7, 14, 28, 42 and 82 post-surgery. A proton density-weighted and a T1-weighted 3D FLASH sequence were acquired to calculate the longitudinal relaxation time T1 of the fractured region and the surrounding tissues. The calculation of T1 in intact and injured bone resulted in a quantitative observation of bone development in intact juvenile tibiae as well as the bone healing process in the injured tibiae. In both areas, T1 decreased over time. To evaluate the differences in T1 behaviour between the intact and injured bone, the relative T1 values (bone-fracture) were calculated, showing clear detectable alterations of T1 after fracture occurrence. These results indicate that qMRI has a high potential not only for clinically relevant applications to detect growth defects or developmental alterations in juvenile bones, but also for forensically relevant applications such as the dating of fractures in cases of child abuse or maltreatment.

MeSH terms

  • Animals
  • Fracture Healing*
  • Fractures, Bone / diagnostic imaging*
  • Magnetic Resonance Imaging / methods*
  • Male
  • Rats, Sprague-Dawley
  • Tibia / diagnostic imaging*
  • Tibia / injuries*

Grants and funding

This work was funded by the Austrian Science Fund FWF (SFB grant F3209-18, https://www.fwf.ac.at, with RS as Vice-Coordinator) and the AO Research Fund of the AO Research Foundation (project number S-06-96W, https://www.aofoundation.org, to AMW). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.