Correlation of clinical and physical-technical image quality in chest CT: a human cadaver study applied on iterative reconstruction

Abstract

BackgroundThe first aim of this study was to evaluate the correlation between clinical and physical-technical image quality applied to different strengths of iterative reconstruction in chest CT images using Thiel cadaver acquisitions and Catphan images. The second aim was to determine the potential dose reduction of iterative reconstruction compared to conventional filtered back projection based on different clinical and physical-technical image quality parameters.MethodsClinical image quality was assessed using three Thiel embalmed human cadavers. A Catphan phantom was used to assess physical-technical image quality parameters such as noise, contrast-detail and contrast-to-noise ratio (CNR).Both Catphan and chest Thiel CT images were acquired on a multislice CT scanner at 120 kVp and 0.9 pitch. Six different refmAs settings were applied (12, 30, 60, 90, 120 and 150refmAs) and each scan was reconstructed using filtered back projection (FBP) and iterative reconstruction (SAFIRE) algorithms (1,3 and 5 strengths) using a sharp kernel, resulting in 24 image series. Four radiologists assessed the clinical image quality, using a visual grading analysis (VGA) technique based on the European Quality Criteria for Chest CT.ResultsCorrelation coefficients between clinical and physical-technical image quality varied from 0.88 to 0.92, depending on the selected physical-technical parameter. Depending on the strength of SAFIRE, the potential dose reduction based on noise, CNR and the inverse image quality figure (IQFinv) varied from 14.0 to 67.8 %, 16.0 to 71.5 % and 22.7 to 50.6 % respectively. Potential dose reduction based on clinical image quality varied from 27 to 37.4 %, depending on the strength of SAFIRE.ConclusionOur results demonstrate that noise assessments in a uniform phantom overestimate the potential dose reduction for the SAFIRE IR algorithm. Since the IQFinv based dose reduction is quite consistent with the clinical based dose reduction, an optimised contrast-detail phantom could improve the use of contrast-detail analysis for image quality assessment in chest CT imaging. In conclusion, one should be cautious to evaluate the performance of CT equipment taking into account only physical-technical parameters as noise and CNR, as this might give an incomplete representation of the actual clinical image quality performance.

Effect of Radiation Dose Reduction and Reconstruction Algorithm on Image Noise, Contrast, Resolution, and Detectability of Subtle Hypoattenuating Liver Lesions at Multidetector CT: Filtered Back Projection versus a Commercial Model–based Iterative Reconstruction Algorithm

“…The observed effect of SAFIRE on physical image properties is mostly consistent with previous studies showing a sizeable noise reduction from SAFIRE (1,4,6,7,9,12–18,21–26,43). Of note, however, is the fact that, in this study, we also observed a reduction in lesion contrast and resolution from SAFIRE.…”

Determination of a suitable low‐dose abdominopelvic CT protocol using model‐based iterative reconstruction through cadaveric study

“…Technical and anthropomorphic phantoms provide a safe, objective and reproducible method of assessing the image quality of different reconstruction algorithms over a range of radiation dose levels. Preliminary phantom experiments with MBIR report a significant reduction in image noise and streak artefact, with significant improvements in image quality compared to FBP and ASIR …”

“…Preliminary phantom experiments with MBIR report a significant reduction in image noise and streak artefact, with significant improvements in image quality compared to FBP and ASIR. 23,24 Many phantom models do not accurately reflect the complex relationship that exists between anatomical variability and image quality, and results of phantom studies may not be entirely applicable to the clinical setting. However, patient studies to assess the performance of reconstruction algorithms at different dose levels can often be problematic to implement, as imaging large numbers of patients at different dose settings introduces confounding factors in addition to ethical challenges.…”

“…To date, clinical studies assessing the use of MBIR in abdominopelvic CT are limited. 13,23 The use of radiological images acquired from cadavers for research, 24 teaching 25 and training 26 purposes has been well described in the literature. Cadavers also provide an excellent model with which to compare reconstruction algorithms by facilitating the repeated scanning of one subject over a range of radiation dose settings without movement artefact or dose concerns.…”

A systematic review of incubator-based neonatal radiography – What does the evidence say?

“…However, Jiang argues that the attenuation of comfort pads vary between different makes of incubator, even by the same manufacturer 2 . These conflicting findings may be based on the method used to evaluate image quality as small changes in image quality may be more apparent in objective measures such as CNR in comparison to visual changes witnessed by human observer 25,26 .…”