Meeting Abstracts
» Direct Detector Chest Radiography: Impact of Tube Voltage on Image Quality

Martin Uffmann, Cornelia Schaefer-Prokop, Nahla Kabalan, Csilla Balassy, Mathias Prokop, Christian Herold

Purpose: To evaluate whether the increased soft-tissue contrast at low kVp settings improves delineation of structures in high and low attenuation areas of digital chest radiographs.

Methods: PA chest radiographs of 50 randomly selected patients were obtained using a direct detector unit (Philips) using automatic exposure control. Images were obtained at 90, 121 and 150 kVp. Hardcopy images were blinded and evaluated in a side-by-side comparison. Three radiologists were asked to rank the visibility of anatomical structures using a 5-point scale (excellent, good, moderate, poor, not acceptable). Evaluation criteria included the visibility of structures in high and low attenuation areas, overall image quality and the assessment of diagnostic relevance of image differences. Statistical analysis was performed using nonparametric analysis of image quality ratings (Kruskal-Wallis test).

Results:The visibility of all structures in both, high and low attenuation areas was ranked significantly superior in the 90kVp images (average ranking = 57.6) followed by the 121 kVp (78.4, p< 0.05) and 150 kVp images (95.3, p< 0.05). Only for the delineation of the carina and main bronchi differences did not reach significance. Sharpness and image noise were ranked significantly better at 90 kVp, no significant motion artifacts were observed. The 90 kVp images were preferred by all three readers. Differences in image quality were not considered diagnostically relevant.

Conclusion: Structural contrast and overall image quality of direct detector radiographs was graded significantly superior when acquired with lower tube voltage. Results suggest a reevaluation of acquisition technique of posteroanterior digital chest radiographs.

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