A statistical method for low-contrast detectability analysis in angiography systems. (September 2016)

• Record Type: Journal Article
• Authors: Radice, A.; Paruccini, N.; Spadavecchia, C.; Villa, R.; Baglivi, A.; Crespi, A.
• Is Part Of: Physica medica. Volume 32(2016)Supplement 3
• Page Start: 216
• Publication Date: 2016-09
• Subjects: Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2016.07.728
• Languages: English
• ISSNs: 1120-1797

Abstract

Abstract : Introduction: The current methods for low-contrast detectability (LCD) analysis of angiographic images are time-consuming, observer dependent and the provided phantoms are not compatible with the small fields, especially in cardiology practise. Purpose: To validate a new statistical approach for LCD, derived from CT, as a quality control test of angiography systems. Materials and methods: A homemade phantom consisting of a square aluminum target (3 × 3 cm 2 ; 0.49 thick) and a 5-step wedge (0, 2–1 mmAl) above an acetate sheet was exposed to different modalities ("low/normal/high fluoroscopy"; "cerebral 2 fps"; "cerebral DSA"; "coronary 15 fps") with 10–15–20–25 cm of PMMA. A customer software was developed to automatically calculate the LCD values as following: LCD = 3.29 ∗ σ μ, where σ μ is the pixel values standard deviation from 100 ROI 6 × 6 pixels 2 within the square target corresponding to a 2.04 mm equivalent diameter's object. At last the LCD values were converted into mmAl using the 5-step wedge. Results: LCD depends on detector characteristics, phantom thickness/material, air-kerma to the detector, beam quality (kVp and HVL) and image noise. For all the modalities LCD values increase with the PMMA layers and range from 0.02 mmAl ("cerebral DSA"; 10 cm PMMA) to 1, 11 mmAl ("low fluoroscopy", 25 cm PMMA). The contrast thresholds with 15 cm PMMA are 0.03 ("cerebral DSA"), 0.26 ("cerebral 2 fps"), 0.38 ("coronary 15 fps"), 0.55 ("normal fluoroscopy"), 0.66 ("high fluoroscopy") and 0.75 mmAl ("low fluoroscopy"). Conclusion: Quantitative measurement of LCD is easy to implement and provides a consistent and reproducible metric of angiographic image quality.