(Tuesday, 7/14/2020) 2:00 PM - 3:00 PM [Eastern Time (GMT-4)]
Room: Track 1
Purpose: To correlate quantitative image quality metrics with radiologists’ detectability score and to develop optimized radiographic techniques for identifying retained suture needles.
Methods: A suture needle phantom was constructed by arranging nine taper-style steel suture needles measuring from 5 mm to 13 mm in length in a 3x3 grid. Portable radiographs of the needle phantom were obtained in various thicknesses of homogenous soft tissue-equivalent material (Superflab bolus material, Mick Radio-Nuclear Instruments, Inc.) and at various locations in an anthropomorphic phantom (Alderson phantom patient). One board-certified abdominal radiologist with 30+ years of experience and three radiology residents scored suture needle visibility on a diagnostic review monitor using a 4-point Likert scale (not visible, barely visible, visible, obviously visible). A template-matching observer model was implemented to calculate suture needle index of detectability (d’) in homogenous backgrounds, and suture needle contrast-to-noise ratio (CNR) was computed in anthropomorphic phantom backgrounds. Correlation between these quantitative image quality metrics and radiologists’ qualitative rankings were assessed using Kendall’s tau.
Results: Radiologists’ assessment correlated to d’ with a Kendall’s tau of 0.77 (p<0.01), and to CNR with a Kendall’s tau of 0.62 (p<0.01). To achieve a “visible” score, a d’ of 26 in a homogenous background and a CNR of 12 in anthropomorphic background are required.
Conclusion: We have correlated d’ and CNR with radiologists’ assessment of needle visibility in homogenous and anthropomorphic phantom backgrounds, respectively. This work will facilitate the development of a patient- and needle size-specific radiographic technique chart based on target d’ and CNR values.
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