Optimization of Neonatal Chest Radiography Exposure Parameters Using a Gammex 610 Phantom: A Cross Sectional Study

Abstract

Introduction: Neonatal chest radiography is essential but carries risks due to high radiation sensitivity and recurrent requirement for imaging. This study identifies optimal exposure parameters for visualizing stipulated pathologies—pneumothorax and hyaline membrane disease—using Gammex 610 phantom to balance image quality and exposure factors.

Methods: The study was conducted using the Gammex 610 neonatal chest phantom, which included inserts simulating normal lung, pneumothorax, and hyaline membrane disease (HMD). A total of 16 radiographs were acquired using different combinations of kVp (45, 50, 55) and mAs (6.3, 4.0, 3.2, 2.5, 2.0, 1.6, 1.3, 1.0). Objective metrics were assessed by calculating signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) using ImageJ. Subjective image quality: visual grade analysis (VGA) was evaluated by five radiologists using a 4-point Likert scale. The inter-rater agreement was measured using Fleiss’ Kappa.

Results: The higher exposure settings yielded superior mean CNR and SNR; they also increased radiation burden. The 45 kVp / 2 mAs setting provided acceptable image quality, with a mean CNR of 5.86 and SNR of 26.75. Furthermore, radiologist-assessed VGA scores (3.61) at this level were comparable to those achieved at higher exposure settings (>50 kVp / 1.6 mAs).

Conclusion: This phantom-based experimentation demonstrates that exposure parameter (kVp and mAs) reduction is possible while maintaining image quality. Based on CNR, SNR and VGA scores and in alignment with the ALARA principle, the authors recommend 45 kVp /2.0 mAs as the most appropriate exposure factors for the institutional settings.