Abstract
ObjectiveTo prospectively evaluate image quality and radiation dose using a low-dose computed tomography angiography protocol and iterative image reconstruction for high-pitch dual-source CT-angiography (DSCTA) of the supraaortic arteries.Material and MethodsDSCTA was performed in 42 patients, using either 120 kVp tube voltage, 120 mAS tube current, 2.4 pitch and filtered back projection, or 100 kVp tube voltage, 100 mAs tube current, 3.2 pitch, and sinogram affirmed iterative reconstruction. Measurements of vessel attenuation, of the contrast-to-noise ratio (CNR) and the signal-to-noise ratio (SNR) were performed to objectively evaluate image quality. Two readers evaluated subjective image quality and image noise, using a four-point scale. Effective dose was used to compare the differences in radiation dose.ResultsLow-dose protocol application showed significantly higher vessel opacification (p = 0.013), and non-significantly higher CNR and SNR values. There was no difference in the subjective image quality and image noise reading between the protocols. Effective dose was significantly lower using the low-dose protocol (1.29±0.21 mSv vs. 2.92±0.72 mSv; p<0.001).ConclusionThe combined use of reduced tube voltage, reduced tube current, and iterative reconstruction reduces radiation dose by 55.4% in high-pitch DSCTA of the supraaortic arteries without impairment of image quality.
Highlights
Computed tomography angiography (CTA) of the supraaortic arteries has become a standard imaging technique for arteriosclerotic disease, acute stroke imaging, and for imaging traumatic arterial dissection [1,2]
The efficacy and usefulness of radiation dose reduction by using reduced tube voltage and reduced tube current settings have already been reported, but this technique leads to increased image noise, which may alter diagnostic image quality if using filtered back projection (FBP) for image reconstruction [7]
For the low dose groups 100 kVp tube voltage was chosen as previous reports using 80 kVp without Sinogram-affirmed iterative reconstruction (SAFIRE) were associated with increased image noise at the level of the shoulder belt [7]
Summary
Computed tomography angiography (CTA) of the supraaortic arteries has become a standard imaging technique for arteriosclerotic disease, acute stroke imaging, and for imaging traumatic arterial dissection [1,2]. The efficacy and usefulness of radiation dose reduction by using reduced tube voltage and reduced tube current settings have already been reported, but this technique leads to increased image noise, which may alter diagnostic image quality if using filtered back projection (FBP) for image reconstruction [7]. The use of FBP in low dose CT scanning is limited, as increased image noise is associated with and reduced image quality [8] To overcome this limitation and to provide diagnostic image quality even at low dose, iterative reconstruction algorithms for image noise correction may be used [9,10]. These reconstruction algorithms allow for image noise reduction during postprocessing, as loop-wise comparison and noise correction to the raw data images are performed [11]
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