Relationship between body habitus and image quality and radiation dose in chest X-ray examinations: A phantom study

To evaluate the influence of being overweight on image quality (IQ), radiation dose and acquisition parameters when undertaking adult chest X-ray (CXR) examinations using routine acquisition protocols.

The Lungman chest phantom, with and without chest plates, was used to simulate the chest region for larger size and average adult patients, respectively. Radiographic acquisitions were conducted using 17 X-ray machines located in eight hospitals using their routine clinical protocols. IQ was assessed using relative visual grading analysis (VGA) and 2 alternative forced choice (2AFC) by six observers. Incident air kerma (IAK) was measured using a solid-state dosimeter.

IQ mean (range) scores between the hospitals were 16.2 (12.0-21.3) with a 56.0% difference and 20.9 (14.1-23.6) with a 50.2% difference for the standard and larger size phantoms, respectively. IAK mean (range) scores 63 µGy (19-136 µGy) with a 150% difference and 159 µGy (27-384 µGy) with a 173% difference for the standard and larger size phantoms, respectively. The chest plates had a significant negative impact on IQ (P = 0.001) and lead to an increased in IAK by approximately 50%.

Visual measures of IQ and IAK showed large differences between hospitals for standard and larger phantom sizes; differences within the hospitals was lower. Overall, Lungman with chest plates was found to degrade IQ and increase radiation dose by a factor of two. Further optimisation is required especially for the larger sized patient's imaging protocols for all eight hospitals.