MRI of the sternal extremity of the clavicle can be used to differentiate between being younger or older than 18, but a simultaneous evaluation of the hand/wrist is essential. Future evaluation of the predictive performance of the model, using comparable but larger reference samples, is necessary to validate these results.
We conclude that 3T MRI provides high resolution, cross-sectional images of the maturation of the clavicle without ionising radiation in a very short time, allowing more accurate determination of bone age than plain radiography.
Objectives Providing recommendations for wrist MRI in age estimation by determining (1) which anatomical structures to include in the statistical model, (2) which MRI sequence to conduct, and (3) which staging technique to apply. Methods Radius and ulna were prospectively studied on 3T MRI in 363 healthy Caucasian participants (185 females, 178 males) between 14 and 26 years old, using T1 spin echo (SE) and T1 gradient echo VIBE. Bone development was assessed applying a 5-stage staging technique with several amelioration attempts to optimise staging. A Bayesian model rendered point predictions of age and diagnostic indices to discern minors from adults. Results All approaches rendered similar results, with none of them outperforming the others. A single bone assessment of radius or ulna sufficed. SE and VIBE sequences were both suitable, but needed sequence-specific age estimation. A one-fits-all 5-stage staging technique-with substages in stage 3was suitable and did not benefit from profound substaging. Age estimation based on SE radius resulted in a mean absolute error of 1.79 years, a specificity (correctly identified minors) of 93%, and a discrimination slope of 0.640. Conclusion Radius and ulna perform similarly to estimate age, and so do SE and VIBE. A one-fits-all staging technique can be applied.
Background
MRI of the clavicle's sternal end has been studied for age estimation. Several pitfalls have been noted, but how they affect age estimation performance remains unclear.
Purpose/Hypothesis
To further study these pitfalls and to make suggestions for a proper use of clavicle MRI for forensic age estimation. Our hypotheses were that age estimation would benefit from 1) discarding stages 1 and 4/5; 2) including advanced substages 3aa, 3ab, and 3ac; 3) taking both clavicles into account; and 4) excluding morphological variants.
Study Type
Prospective cross‐sectional.
Population
Healthy Caucasian volunteers between 11 and 30 years old (524; 277 females, 247 males).
Field Strength/Sequence
3T, T1‐weighted gradient echo volumetric interpolated breath‐hold examination (VIBE) MR‐sequence.
Assessment
Four observers applied the most elaborate staging technique for long bone development that has been described in the current literature (including stages, substages, and advanced substages). One of the observers repeated a random selection of the assessments in 110 participants after a 2‐week interval. Furthermore, all observers documented morphological variants.
Statistical Tests
Weighted kappa quantified reproducibility of staging. Bayes' rule was applied for age estimation with a continuation ratio model for the distribution of the stages. According to the hypotheses, different models were tested. Mean absolute error (MAE) differences between models were compared, as were MAEs between cases with and without morphological variants.
Results
Weighted kappa equaled 0.82 for intraobserver and ranged between 0.60 and 0.64 for interobserver agreement. Stages 1 and 4/5 were allocated interchangeably in 4.3% (54/1258). Age increased steadily in advanced substages of stage 3, but improvement in age estimation was not significant (right P = 0.596; left P = 0.313). The model that included both clavicles and discarded stages 1 and 4/5 yielded an MAE of 1.97 years, a root mean squared error of 2.60 years, and 69% correctly classified minors. Morphological variants rendered significantly higher MAEs (right 3.84 years, P = 0.015; left 2.93 years, P = 0.022).
Data Conclusion
Our results confirmed hypotheses 3) and 4), while hypotheses 1) and 2) remain to be investigated in larger studies.
Level of Evidence: 1
Technical Efficacy: Stage 2
J. Magn. Reson. Imaging 2020;51:377–388.
In age estimation, 3T MRI of third molars could be valuable. Some considerations are, however, necessary to transfer known staging methods to this 3D technique.
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