The Acceptability of Iterative Reconstruction Algorithms in Head CT: An Assessment of Sinogram Affirmed Iterative Reconstruction (SAFIRE) vs. Filtered Back Projection (FBP) Using Phantoms

Abstract

Background: Computed tomography (CT) is the primary imaging investigation for many neurologic conditions with a proportion of patients incurring cumulative doses. Iterative reconstruction (IR) allows dose optimization, but head CT presents unique image quality complexities and may lead to strong reader preferences. Objectives: This study evaluates the relationships between image quality metrics, image texture, and applied radiation dose within the context of IR head CT protocol optimization in the simulated patient setting. A secondary objective was to determine the influence of optimized protocols on diagnostic confidence using a custom phantom. Methods and Setting: A three-phase phantom study was performed to characterize reconstruction methods at the local reference standard and a range of exposures. CT numbers and pixel noise were quantified supplemented by noise uniformity, noise power spectrum, contrast-to-noise ratio (CNR), high-and low-contrast resolution. Reviewers scored optimized protocol images based on established reporting criteria. Results: Increasing strengths of IR resulted in lower pixel noise, lower noise variance, and increased CNR. At the reference standard, the image noise was reduced by 1.5 standard deviation and CNR increased by 2.0. Image quality was maintained at 24% relative dose reduction. With the exception of image sharpness, there were no significant differences between grading for IR and filtered back projection reconstructions. Conclusions: IR has the potential to influence pixel noise, CNR, and noise variance (image texture); however, systematically optimized IR protocols can maintain the image quality of filtered back projection. This work has guided local application and acceptance of lower dose head CT protocols.

Image quality of conventional images of dual‐layer SPECTRAL CT: A phantom study

“…Yet, for this comparative study, in which the same iterative reconstruction settings are used, these metrics improve comprehensibility and clarity. Moreover, these metrics have been widely used in multiple other comparative studies using iterative reconstruction methods . Thirdly, we studied the image quality of the IQon using a fixed set of scan and reconstruction parameters, whereas other settings, for instance collimation, reconstructed slice thickness, and reconstruction kernel also have an effect on image quality .…”

“…Moreover, these metrics have been widely used in multiple other comparative studies using iterative reconstruction methods. 20,23,24 Thirdly, we studied the image quality of the IQon using a fixed set of scan and reconstruction parameters, whereas other settings, for instance collimation, reconstructed slice thickness, and reconstruction kernel also have an effect on image quality. 25 Our rationale was to select the scan and reconstruction parameters that are used most at our institute and moreover are used commonly for quality control assessment.…”

Deep learning image reconstruction algorithm for abdominal multidetector CT at different tube voltages: assessment of image quality and radiation dose in a phantom study

“…The degradation of image sharpness resulting in a blotchy appearance of the solid organs could compromise the diagnostic accuracy if it caused a well-defined lesion to appear less well-defined. Such degradation can make it difficult to differentiate a small hepatic cyst from metastasis in abdominal CT interpretation for radiologists and had been regarded as an important drawback of ASIR [32][33][34]. At the beginning of this study, we expected that DLIR has a great advantage in improving the noise and sharpness simultaneously, which was regarded to be the weakest point of ASIR-V in terms of image sharpness.…”

Evaluation of Lower-Dose Spiral Head CT for Detection of Intracranial Findings Causing Neurologic Deficits

“…At the same dose level with images reconstructed with weighted FBP, sensitivity for target lesions accounting for neurologic deficits declined by about 2%-3% and specificity declined by 1.5%-5%. Prior work examining the ability to lower the radiation dose at unenhanced head CT has been largely focused on the ability to improve image quality, [21][22][23] because this may be a barrier to radiologists examining noisier, lower-dose images. Wu et al 24 examined image quality and diagnostic accuracy using iterative reconstruction with a case-control design and lowering the rotation dose by 43% with either tube current or tube voltage reduction.…”