Spectral Beam Shaping in Unenhanced Chest CT Examinations

Publication date: Available online 18 October 2017
Source:Academic Radiology
Author(s): Saravanabavaan Suntharalingam, Thomas Allmendinger, Sebastian Blex, Mohammad Al-Bayati, Kai Nassenstein, Bernd Schweiger, Michael Forsting, Axel Wetter
Rationale and ObjectivesThis study aimed to determine the optimal tube potential for unenhanced chest computed tomographies (CTs) with age-related phantoms.Materials and MethodsThree physical anthropomorphic phantoms (newborn, 5-year-old child, and adult) were scanned on a third-generation dual-source CT using CAREkV in semi-mode and CAREDose4D (ref. KV: 120; ref. mAs 50). Scans were performed with all available tube potentials (70–150 kV and Sn150 kV). The lowest volume computed tomography dose index (CTDIvol) was selected to perform additional Sn100-kV scans with matched and half (Sn100-half) CTDIvol value. Image quality was evaluated on the basis of contrast-to-noise ratio (CNR).ResultsFor the newborn phantom, 70–110 kV was selected as the optimal range (0.36–0.37 mGy). Using Sn150 kV led to an increase in radiation dose (0.75 mGy) without improving CNR (96.9 vs 101.5). Sn100-half showed a decrease in CNR (73.1 vs 101.5). The lowest CTDIvol for the child phantom was achieved between 100 and 120 kV (0.78–0.80 mGy). Using Sn150 kV increased radiation dose (1.02 mGy) without improvement of CNR (92.4 vs 95.8). At Sn100-half CNR was decreased (61.4 vs 95.8). For adults, 140 and 150 kV revealed the lowest CTDIvol (2.68 and 2.67 mGy). The Sn150 kV scan delivered comparable CNR (54.4 vs 56.6), but a lower CTDIvol (2.08 mGy). At Sn100-half CNR was comparable to the 150 kV scan (58.1 vs 56.6).ConclusionUnenhanced chest CT performed at 100 kV or 150 kV with tin filtration enables radiation dose reduction for the adult phantom, but not for the pediatric phantoms.



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