Thomas Ehammer

Fully Automatic Bone Age Estimation from Left Hand MR Images

There has recently been an increased demand in bone age estimation (BAE) of living individuals and human remains in legal medicine applications. A severe drawback of established BAE techniques based on X-ray images is radiation exposure, since many countries prohibit scanning involving ionizing radiation without diagnostic reasons. We propose a completely automated method for BAE based on volumetric hand MRI images. On our database of 56 male caucasian subjects between 13 and 19 years, we are able to estimate the subjects age with a mean difference of 0.85 ± 0.58 years compared to the chronological age, which is in line with radiologist results using established radiographic methods. We see this work as a promising first step towards a novel MRI based bone age estimation system, with the key benefits of lacking exposure to ionizing radiation and higher accuracy due to exploitation of volumetric data.

Applicability of Greulich-Pyle and Tanner-Whitehouse grading methods to MRI when assessing hand bone age in forensic age estimation: A pilot study.

Determination of skeletal development is a key pillar in forensic age estimation of living persons. Radiological assessment of hand bone age is widely used until the age of about 17-18 years, applying visual grading techniques to hand radiographs. This study investigated whether Greulich-Pyle (GP) and Tanner-Whitehouse (TW2) grading can be equally used for magnetic resonance imaging (MRI) data, which would offer the huge benefit of avoiding ionizing radiation. In 18 subjects aged between 7 and 17 years a radiograph and an MRI scan of the hand were performed. Epiphyseal ossification of hand bones was rated by two blinded radiologists with both GP and TW2. Correlation between hand MRIs and radiographs was analyzed by linear regression and inter-observer agreement was assessed. Correlation between age estimates from MRI and radiographs was high for both GP (r(2)=0.98) and TW2 (r(2)=0.93). MRI showed a tendency to estimate age slightly lower for 14-18 year-olds, which would be favorable regarding majority age determination in case this result could be reproduced using a currently not existing reference estimation method based on MRI data. Inter-observer agreement was similar for GP in radiographs and MRI, while for TW2, agreement in MRI was lower than in radiographs. In spite of limitations regarding sample size and recruited subjects, our results indicate that the use of GP and TW2 on MRI data offers the possibility of hand bone age estimation without the need for ionizing radiation.

CT-Guided Biopsy of Lesions of the Lung, Liver, Pancreas or of Enlarged Lymph Nodes: Value of Additional Fine Needle Aspiration (FNA) to Core Needle Biopsy (CNB) in an Offsite Pathologist Setting

RATIONALE AND OBJECTIVES To assess the value of additional fine needle aspiration (FNA) to core needle biopsy (CNB) in computed tomography-guided biopsy of lesions of the lung, liver, pancreas, or of enlarged lymph nodes in an offsite cytopathologist setting. MATERIALS AND METHODS This retrospective Health Insurance Portability and Accountability Act-compliant study was approved by the Institutional Review Board (IRB); informed consent (IC) was waived. Data of 377 patients who underwent computed tomography-guided FNA and CNB of lesions of the lung, liver, pancreas, or enlarged lymph nodes were enrolled. An onsite cytopathologist was not available. Sensitivity and specificity were calculated for FNA, CNB, and combined FNA/CNB. For the purpose of our study, positive diagnoses from CNB specimens or subsequent biopsy or surgical resection specimens or clinical follow-up data were considered as the standard of reference. RESULTS CNB yielded a significantly higher sensitivity than FNA in all sites, except the pancreas, where the difference did not reach statistical significance. Additional FNA to CNB did not significantly increase the sensitivity. Specificity did not significantly differ between FNA, CNB, and combined FNA/CNB in all sites. Malignancies of 1.7% were detected only with FNA, without evidence of malignancy in CNB; for the remaining malignancies, CNB was positive or indeterminate. CONCLUSION Additional FNA to CNB without an onsite cytopathologist does not yield higher sensitivity or specificity compared to CNB alone.

Forensic age estimation by morphometric analysis of the manubrium from 3D MR images

Forensic age estimation research based on skeletal structures focuses on patterns of growth and development using different bones. In this work, our aim was to study growth-related evolution of the manubrium in living adolescents and young adults using magnetic resonance imaging (MRI), which is an image acquisition modality that does not involve ionizing radiation. In a first step, individual manubrium and subject features were correlated with age, which confirmed a statistically significant change of manubrium volume (Mvol:p<0.01, R2¯=0.50) and surface area (Msur:p<0.01, R2¯=0.53) for the studied age range. Additionally, shapes of the manubria were for the first time investigated using principal component analysis. The decomposition of the data in principal components allowed to analyse the contribution of each component to total shape variation. With 13 principal components, ∼96% of shape variation could be described (Mshp:p<0.01, R2¯=0.60). Multiple linear regression analysis modelled the relationship between the statistically best correlated variables and age. Models including manubrium shape, volume or surface area divided by the height of the subject (Y∼MshpMsur/Sh:p<0.01, R2¯=0.71; Y∼MshpMvol/Sh:p<0.01, R2¯=0.72) presented a standard error of estimate of two years. In order to estimate the accuracy of these two manubrium-based age estimation models, cross validation experiments predicting age on held-out test sets were performed. Median absolute difference of predicted and known chronological age was 1.18 years for the best performing model (Y∼MshpMsur/Sh:p<0.01, Rp2=0.67). In conclusion, despite limitations in determining legal majority age, manubrium morphometry analysis presented statistically significant results for skeletal age estimation, which indicates that this bone structure may be considered as a new candidate in multi-factorial MRI-based age estimation.

Reducing acquisition time for MRI-based forensic age estimation

Radiology-based estimation of a living person’s unknown age has recently attracted increasing attention due to large numbers of undocumented immigrants entering Europe. To avoid the application of X-ray-based imaging techniques, magnetic resonance imaging (MRI) has been suggested as an alternative imaging modality. Unfortunately, MRI requires prolonged acquisition times, which potentially represents an additional stressor for young refugees. To eliminate this shortcoming, we investigated the degree of reduction in acquisition time that still led to reliable age estimates. Two radiologists randomly assessed original images and two sets of retrospectively undersampled data of 15 volunteers (N = 45 data sets) applying an established radiological age estimation method to images of the hand and wrist. Additionally, a neural network-based age estimation method analyzed four sets of further undersampled images from the 15 volunteers (N = 105 data sets). Furthermore, we compared retrospectively undersampled and acquired undersampled data for three volunteers. To assess reliability with increasing degree of undersampling, intra-rater and inter-rater agreement were analyzed computing signed differences and intra-class correlation. While our findings have to be confirmed by a larger prospective study, the results from both radiological and automatic age estimation showed that reliable age estimation was still possible for acquisition times of 15 seconds.