Radiation dose reduction in parasinus CT by spectral shaping
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Spectral shaping aims to narrow the X-ray spectrum of clinical CT. The aim of this study was to determine the image quality and the extent of radiation dose reduction that can be achieved by tin prefiltration for parasinus CT.
All scans were performed with a third generation dual-source CT scanner. A study protocol was designed using 100 kV tube voltage with tin prefiltration (200 mAs) that provides image noise levels comparable to a low-dose reference protocol using 100 kV without spectral shaping (25 mAs). One hundred consecutive patients were prospectively enrolled and randomly assigned to the study or control group. All patients signed written informed consent. The study protocol was approved by the local Institutional Review Board and applies to the HIPAA. Subjective and objective image quality (attenuation values, image noise, and contrast-to-noise ratio (CNR)) were assessed. Radiation exposure was assessed as volumetric CT dose index, and effective dose was estimated. Mann-Whitney U test was performed for radiation exposure and for image noise comparison.
All scans were of diagnostic image quality. Image noise in air, in the retrobulbar fat, and in the eye globe was comparable between both groups (all p > 0.05). CNReye globe/air did not differ significantly between both groups (p = 0.7). Radiation exposure (1.7 vs. 2.1 mGy, p < 0.01) and effective dose (0.055 vs. 0.066 mSv, p < 0.01) were significantly reduced in the study group.
Radiation dose can be further reduced by 17% for low-dose parasinus CT by tin prefiltration maintaining diagnostic image quality.
KeywordsParasinus CT Tin filtration Spectral shaping
We thank Petra Ruse and Katharina Roth for excellent patient management and Marie-Louise Haider for assistance in data management. This study was supported by the German government, Bundesministerium für Bildung und Forschung (01EX1012B, Spitzencluster Medical Valley).
Compliance with ethical standards
We declare that all human and animal studies have been approved by the ethics committee and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. We declare that all patients gave informed consent prior to inclusion in this study
Conflict of interest
MM is part of Siemens Speakers’ Bureau; ML is part of Siemens and Bayer Speakers’ Bureau, has grants from Siemens and Bayer and consults for Bracco;
MB is part of Siemens Speakers’ Bureau; MU is part of Siemens, Bayer, Bracco and Medtronic Speakers’ Bureau; and WW is part of Siemens Speakers’ Bureau.
No financial support for this study was received from any company listed above.