Bone age determination using only the index finger: a novel approach using a convolutional neural network compared with human radiologists

Nakul E. Reddy, Jesse C. Rayan, Ananth V. Annapragada, Nadia F. Mahmood, Alan E. Scheslinger, Wei Zhang, J. Herman Kan

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Background: Recently developed convolutional neural network (CNN) models determine bone age more accurately than radiologists. Objective: The purpose of this study was to determine whether a CNN and radiologists can accurately predict bone age from radiographs using only the index finger rather than the whole hand. Materials and methods: We used a public anonymized dataset provided by the Radiological Society of North America (RSNA) pediatric bone age challenge. The dataset contains 12,611 hand radiographs for training and 200 radiographs for testing. The index finger was cropped from these images to create a second dataset. Separate CNN models were trained using the whole-hand radiographs and the cropped second-digit dataset using the consensus ground truth provided by the RSNA bone age challenge. Bone age determination using both models was compared with ground truth as provided by the RSNA dataset. Separately, three pediatric radiologists determined bone age from the whole-hand and index-finger radiographs, and the consensus was compared to the ground truth and CNN-model-determined bone ages. Results: The mean absolute difference between the ground truth and CNN bone age for whole-hand and index-finger was similar (4.7 months vs. 5.1 months, P=0.14), and both values were significantly smaller than that for radiologist bone age determination from the single-finger radiographs (8.0 months, P<0.0001). Conclusion: CNN-model-determined bone ages from index-finger radiographs are similar to whole-hand bone age interpreted by radiologists in the dataset, as well as a model trained on the whole-hand radiograph. In addition, the index-finger model performed better than the ground truth compared to subspecialty trained pediatric radiologists also using only the index finger to determine bone age. The radiologist interpreting bone age can use the second digit as a reliable starting point in their search pattern.

Original languageEnglish (US)
Pages (from-to)516-523
Number of pages8
JournalPediatric radiology
Issue number4
StatePublished - Apr 1 2020
Externally publishedYes


  • Bone age
  • Children
  • Convolutional neural network
  • Deep learning
  • Forefinger
  • Hand
  • Musculoskeletal
  • Radiographs

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Radiology Nuclear Medicine and imaging


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