Spatial and contrast resolution of ultralow dose dentomaxillofacial CT imaging using iterative reconstruction technology

Abstract

Objectives: The objective of this study was to determine how iterative reconstruction technology (IRT) influences contrast and spatial resolution in ultralow-dose dentomaxillofacial CT imaging. Methods: A polymethyl methacrylate phantom with various inserts was scanned using a reference protocol (RP) at CT dose index volume 36.56 mGy, a sinus protocol at 18.28 mGy and ultralow-dose protocols (LD) at 4.17 mGy, 2.36 mGy, 0.99 mGy and 0.53 mGy. All data sets were reconstructed using filtered back projection (FBP) and the following IRTs: adaptive statistical iterative reconstructions (ASIRs) (ASIR-50, ASIR-100) and model-based iterative reconstruction (MBIR). Inserts containing line-pair patterns and contrast detail patterns for three different materials were scored by three observers. Observer agreement was analyzed using Cohen's kappa and difference in performance between the protocols and reconstruction was analyzed with Dunn's test at a 5 0.05. Results: Interobserver agreement was acceptable with a mean kappa value of 0.59. Compared with the RP using FBP, similar scores were achieved at 2.36 mGy using MBIR. MIBR reconstructions showed the highest noise suppression as well as good contrast even at the lowest doses. Overall, ASIR reconstructions did not outperform FBP. Conclusions: LD and MBIR at a dose reduction of .90% may show no significant differences in spatial and contrast resolution compared with an RP and FBP. Ultralow-dose CT and IRT should be further explored in clinical studies.

Dose reduction in CT imaging for facial bone trauma in adults: A narrative literature review

“…ASIR uses information obtained from the FBP algorithm as a scaffold for image reconstruction, while MBIR incorporates a number of key parameters . These iterative reconstruction (IR) algorithms are both reported as capable of reducing dose in facial bone imaging, while maintaining low noise and enhancing spatial and contrast resolution . Studies published by Widmann et al demonstrated that the implementation of adaptive statistical IR and model‐based IR in craniofacial bone imaging reduced dose by 76% and 91% respectively.…”

“…These iterative reconstruction (IR) algorithms are both reported as capable of reducing dose in facial bone imaging, while maintaining low noise and enhancing spatial and contrast resolution . Studies published by Widmann et al demonstrated that the implementation of adaptive statistical IR and model‐based IR in craniofacial bone imaging reduced dose by 76% and 91% respectively. The absorbed dose using adaptive statistical IR can be as low as 2.19 mGy, while for model‐based IR dose can be minimised to 0.22 mGy.…”

“…A follow‐on study reported that the use of IR significantly improved subjective image quality for the purpose of navigated surgery on craniofacial fractures, in comparison to images produced through FBP, as shown in Figure . On analysis of the results, Widmann et al concluded that although IR reduces noise, further research is necessary to establish whether diagnosis of non‐displaced fractures would become compromised due to the integral smoothing effects.…”

Influence of Ultra-Low-Dose and Iterative Reconstructions on the Visualization of Orbital Soft Tissues on Maxillofacial CT

“…25 With MBIR, ultra-low-dose protocols at CTDI vol ϭ 4.14 and 2.63 mGy may show comparable scores for spatial resolution, which may allow a dose-reduction potential of up to 93%. 26 Compared with FBP, ASIR was not able to significantly improve spatial resolution. 26 In a more recent human cadaver study evaluating the influence of various low-dose protocols and IRTs on the detectability of midfacial fractures, ultra-low-dose protocols at CTDI vol ϭ 1.0 and 2.6 mGy were diagnostic for dislocated and nondislocated fractures, respectively.…”

“…26 Compared with FBP, ASIR was not able to significantly improve spatial resolution. 26 In a more recent human cadaver study evaluating the influence of various low-dose protocols and IRTs on the detectability of midfacial fractures, ultra-low-dose protocols at CTDI vol ϭ 1.0 and 2.6 mGy were diagnostic for dislocated and nondislocated fractures, respectively. 14 However, due to smoothing effects, ASIR and MBIR could not improve fracture detection.…”