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.
Highlights
The exact determination of the age of a fracture is a legally relevant question in cases where children show multiple fractures in different stages of bone healing and suspicion of maltreatment exists
The intra-observer reliability, based on double measurements of the regions of interest (ROI) of the muscle (ROI 1), bone (ROI 3) and fractured region (ROI 6), was tested with the intra-observer correlation coefficient resulting in rI = 0.941, rI = 0.851 and rI = 0.576 (p
This study aims to systematically investigate time-resolved changes in T1 relaxation times of a surgical lesion of the epiphysis and metaphysis in juvenile Sprague-Dawley rats, to determine whether or not Quantitative magnetic resonance imaging (qMRI) is suitable to detect the bone healing process in juvenile subjects
Summary
The exact determination of the age of a fracture is a legally relevant question in cases where children show multiple fractures in different stages of bone healing and suspicion of maltreatment exists. The well-studied bone healing process starts with an inflammatory response followed by a primary soft callus formation, callus mineralisation and is completed with bone remodelling. During these general phases of fracture healing several anabolic as well as catabolic processes occur [3,4,5,6]. Detailed transitions of phases and changes in metabolic processes are not visible in radiographic imaging and the single stages may not be captured by using this method. The assessment of a fracture may sometimes be challenging with standard radiographs due to a lack of sufficient image information
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