Published in:
Open Access 01-05-2017 | Computed Tomography
Feasibility of spectral shaping for detection and quantification of coronary calcifications in ultra-low dose CT
Published in: European Radiology | Issue 5/2017
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Objectives
To evaluate detectability and quantification of coronary calcifications for CT with a tin filter for spectral shaping.
Methods
Phantom inserts with 100 small and 9 large calcifications, and a moving artificial artery with 3 calcifications (speed 0–30 mm/s) were placed in a thorax phantom simulating different patient sizes. The phantom was scanned in high-pitch spiral mode at 100 kVp with tin filter (Sn100 kVp), and at a reference of 120 kVp, with electrocardiographic (ECG) gating. Detectability and quantification of calcifications were analyzed for standard (130 HU) and adapted thresholds.
Results
Sn100 kVp yielded lower detectability of calcifications (9 % versus 12 %, p = 0.027) and lower Agatston scores (p < 0.008), irrespective of calcification, patient size and speed. Volume scores of the moving calcifications for Sn100 kVp at speed 10–30 mm/s were lower (p < 0.001), while mass scores were similar (p = 0.131). For Sn100 kVp with adapted threshold of 117 HU, detectability (p = 1.000) and Agatston score (p > 0.206) were similar to 120 kVp. Spectral shaping resulted in median dose reduction of 62.3 % (range 59.0–73.4 %).
Conclusions
Coronary calcium scanning with spectral shaping yields lower detectability of calcifications and lower Agatston scores compared to 120 kVp scanning, for which a HU threshold correction should be developed.
Key points
• Sn100kVp yields lower detectability and lower Agatston scores compared to 120kVp
• Adapted HU threshold for Sn100kVp provides Agatston scores comparable to 120kVp
• Sn100 kVp considerably reduces dose in calcium scoring versus 120 kVp