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


METHODS
Clinical 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.


RESULTS
Correlation 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 (IQF(inv)) 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.


CONCLUSIONS
Our results demonstrate that noise assessments in a uniform phantom overestimate the potential dose reduction for the SAFIRE IR algorithm. Since the IQF(inv) 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.
Department of Basic Medical Sciences, Ghent University, Proeftuinstraat 86, B-9000, Ghent, Belgium. An.decrop@ugent.be.
An
A
De Crop
Department of Radiology, Ghent University Hospital, De Pintelaan 185, B-9000, Ghent, Belgium. peter.smeets@ugent.be.
Peter
P
Smeets
Department of Basic Medical Sciences, Ghent University, Proeftuinstraat 86, B-9000, Ghent, Belgium. tom.vanhoof@ugent.be.
Tom
T
Van Hoof
Department of Radiology, Ghent University Hospital, De Pintelaan 185, B-9000, Ghent, Belgium. merelvergauwen@hotmail.com.
Merel
M
Vergauwen
Department of Radiology, Ghent University Hospital, De Pintelaan 185, B-9000, Ghent, Belgium. tommarc_dewaele@hotmail.com.
Tom
T
Dewaele
Department of Radiology, Ghent University Hospital, De Pintelaan 185, B-9000, Ghent, Belgium. mathiasvanborsel@gmail.com.
Mathias
M
Van Borsel
Department of Radiology, Ghent University Hospital, De Pintelaan 185, B-9000, Ghent, Belgium. rik.achten@ugent.be.
Eric
E
Achten
Department of Radiology, Ghent University Hospital, De Pintelaan 185, B-9000, Ghent, Belgium. koenraad.verstraete@ugent.be.
Koenraad
K
Verstraete
Department of Basic Medical Sciences, Ghent University, Proeftuinstraat 86, B-9000, Ghent, Belgium. katharina.dherde@ugent.be.
Katharina
K
D'Herde
Department of Basic Medical Sciences, Ghent University, Proeftuinstraat 86, B-9000, Ghent, Belgium. hubert.thierens@ugent.be.
Hubert
H
Thierens
Department of Basic Medical Sciences, Ghent University, Proeftuinstraat 86, B-9000, Ghent, Belgium. klaus.bacher@ugent.be.
Klaus
K
Bacher
D000465:Algorithms; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D012680:Sensitivity and Specificity; D013909:Thorax / Q000033:anatomy & histology*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*