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. 2019 Jan;20(1):321-330.
doi: 10.1002/acm2.12510. Epub 2018 Dec 26.

Ultra-low dose CT colonography with automatic tube current modulation and sinogram-affirmed iterative reconstruction: Effects on radiation exposure and image quality

Roberta Cianci  1 , Andrea Delli Pizzi  1 , Gianluigi Esposito  1 , Mauro Timpani  1 , Alessandra Tavoletta  1 , Pierluigi Pulsone  1 , Raffaella Basilico  1 , Antonio Raffaele Cotroneo  1 , Antonella Filippone  1
Affiliations

Ultra-low dose CT colonography with automatic tube current modulation and sinogram-affirmed iterative reconstruction: Effects on radiation exposure and image quality

Roberta Cianci et al. J Appl Clin Med Phys. 2019 Jan.

Abstract

Objective: To assess the radiation dose and image quality of ultra-low dose (ULD)-CT colonography (CTC) obtained with the combined use of automatic tube current (mAs) modulation with a quality reference mAs of 25 and sinogram-affirmed iterative reconstruction (SAFIRE), compared to low-dose (LD) CTC acquired with a quality reference mAs of 55 and reconstructed with filtered back projection (FBP).

Methods: Eighty-two patients underwent ULD-CTC acquisition in prone position and LD-CTC acquisition in supine position. Both ULD-CTC and LD-CTC protocols were compared in terms of radiation dose [weighted volume computed tomography dose index (CTDIvol ) and effective dose], image noise, image quality, and polyp detection.

Results: The mean effective dose of ULD-CTC was significantly lower than that of LD-CTC (0.98 and 2.69 mSv respectively, P < 0.0001) with an overall dose reduction of 63.2%. Image noise was comparable between ULD-CTC and LD-CTC (28.6 and 29.8 respectively, P = 0.09). There was no relevant difference when comparing image quality scores and polyp detection for both 2D and 3D images.

Conclusion: ULD-CTC allows to significantly reduce the radiation dose without meaningful image quality degradation compared to LD-CTC.

Keywords: automated tube current modulation; computed tomographic colonography; computed tomographic colonography, technique; dose reduction; iterative reconstruction techniques; radiation dose.

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Figures

Figure 1
Figure 1
Plots of CTDI vol (a) and Effective Dose (b) values obtained with LD‐CTC and ULD‐CTC.
Figure 2
Figure 2
Plots of objective noise values obtained with LD‐CTC and ULD‐CTC.
Figure 3
Figure 3
Axial two‐dimensional (2D) computed tomography images (a,b) and three‐dimensional (3D) endoluminal reconstructions (c,d) of the rectosigmoid junction in a 69‐yr‐old, class D, man after incomplete colonoscopy. Both 2D LD (a) and ultra‐low dose (ULD) (b) images were rated to have an average image quality, with mild image noise. Similarly, both 3D low‐dose (LD) (c) and ULD (d) images were judged to have an average image quality, despite a slight increase in mural surface irregularity for the ULD protocol (d).
Figure 4
Figure 4
Axial two‐dimensional (2D) computed tomography images (a,b) and three‐dimensional (3D) endoluminal reconstructions (c,d) of the splenic flexure in a 71‐yr‐old, class B, man after incomplete colonoscopy. Both 2D low‐dose (a) and ultra‐low dose (ULD) (b) images were rated to have comparable overall image quality, despite a slight increase of the perceived noise and aortic contour blurriness of the ULD protocol. Similarly, no significant differences were found between overall 3D image quality scores of ULD and LD acquisitions, despite a slight increase of the mural surface irregularity of the ULD protocol (d).
Figure 5
Figure 5
Axial two‐dimensional (2D) computed tomography images (a,b) and three‐dimensional 3D endoluminal reconstructions (c,d) at the level of the ileocecal valve in a 67‐yr‐old, class D, man with a history of colonic polyps and incomplete colonoscopy. Low‐dose (a) and ultra‐low dose (ULD) (b) 2D images were deemed to have equivalent overall quality, but there was a less subjective noise for the ULD acquisition with sinogram‐affirmed iterative reconstruction (b). No significant differences were found in overall 3D image quality, although there was a mild increase of mural surface irregularity for the ULD acquisition (d).
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