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Purpose: Medical imaging can be used to estimate a patient’s biological age, which may provide complementary information to clinicians compared to chronological age. In this study, we aimed to develop a method to estimate a patient’s age based on their chest CT scan. Additionally, we investigated whether chest CT estimated age is a more accurate predictor of lung cancer risk compared to chronological age. Methods: To develop our age prediction model, we utilized composite CT images and Inception-ResNet-v2. The model was trained, validated, and tested on 13,824 chest CT scans from the National Lung Screening Trial, with 91% for training, 5% for validation, and 4% for testing. Additionally, we independently tested the model on 1849 CT scans collected locally. To assess chest CT estimated age as a risk factor for lung cancer, we computed the relative lung cancer risk between two groups. Group 1 consisted of individuals assigned a CT age older than their chronological age, while Group 2 comprised those assigned a CT age younger than their chronological age. Results: Our analysis revealed a mean absolute error of 1.84 years and a Pearson’s correlation coefficient of 0.97 for our local data when comparing chronological age with the estimated CT age. The model showed the most activation in the area associated with the lungs during age estimation. The relative risk for lung cancer was 1.82 (95% confidence interval, 1.65–2.02) for individuals assigned a CT age older than their chronological age compared to those assigned a CT age younger than their chronological age. Conclusion: Findings suggest that chest CT age captures some aspects of biological aging and may be a more accurate predictor of lung cancer risk than chronological age. Future studies with larger and more diverse patients are required for the generalization of the interpretations.

Posit numeric format is getting more and more attention in recent years. Its tapered precision makes it especially suitable in many applications including deep learning computation. However, due to its dynamic component bit-width, the cost of implementing posit arithmetic in hardware is more expensive than its floating-point counterpart. To solve this cost problem, in this paper, posit multipliers with approximate computing features are proposed. The core idea of the proposed design is to truncate the fraction multiplier according to the estimated fraction bit-width of the product. So that the resource consumption of the fraction multiplier and thus the fraction adder can be significantly reduced. The proposed method is applied in both linear domain and logarithm domain posit multipliers. The 8/16/32-bit version of the proposed approximate posit multipliers are implemented and analyzed. For the commonly used 16-bit posit format in deep learning computation, the proposed approximate posit multiplier can consume 16% less power compared to the conventional posit multiplier design. The proposed 16-bit approximate logarithm multiplier can achieve a 15% improvement in terms of power consumption compared to the state-of-the-art posit approximate logarithm multiplier. The proposed 16-bit approximate posit multipliers are applied in the computation of several deep neural network models and significant improvements on energy efficiency can be achieved with negligible accuracy degradation.