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Published on: June 12, 2020
Dose optimization for CT scans of the temporal bone using spectral shaping tin filter
Alexander von Hessling1, Carlos Vinícius Gomes1, Pia Niederau1
1Department of Radiology and Nuclear Medicine, Luzerner Kantonsspital, University Teaching and Research Hospital, University of Lucerne, Lucerne, Switzerland.
Background:
Computed tomography is a highly effective diagnostic tool for evaluating pathological conditions of the temporal bone. However, the relatively high radiation doses pose risks to radiosensitive organs, making dose optimization essential in accordance with the ALARA principle. Recent technological advances, such as tin-based photon-shaping filters, have enabled significant dose reduction in both dual- and single-energy CT without compromising image quality.
Purpose:
To evaluate the impact of a spectral shaping tin filter on image quality and radiation dose in temporal bone CT examinations.
Methods:
Thirty-six patients undergoing temporal bone CT were retrospectively analysed. Group A (n = 13) underwent standard CT, while Group B (n = 23) underwent CT examination using 150 kVp beam with additional tin filtration. Images were reconstructed with model-based iterative reconstruction (ADMIRE, level 3) and assessed by two neuroradiologists using a 3-point Likert scale. Radiation dose was quantified via CTDIvol, DLP, and eye lens dose using Monte Carlo simulations.
Results:
Both protocols provided diagnostic-quality images. The protocol with tin filter achieved slightly superior image quality (median scores: overall 3.00 vs. 2.88, contrast 3.00 vs. 2.96, resolution 2.58 vs. 2.53; p < 0.05) with substantial inter-rater agreement (κ = 0.75-0.97). Mean CTDIvol and DLP decreased from 59.1 ± 12.1 mGy and 551.8 ± 226.8 mGy×cm (Group A) to 39.9 ± 1.7 mGy and 302.4 ± 33.8 mGy×cm (Group B) (p < 0.001). Eye lens dose was reduced by 34% (54.7 ± 10.9 mGy vs. 36.4 ± 2.2 mGy, p < 0.001).
Conclusions:
Incorporating a tin filter into temporal bone CT significantly reduces radiation exposure, including lens dose, without compromising-and in some cases slightly improving-image quality. Routine implementation of spectral shaping may enhance patient safety in clinical practice.
