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

De Crop A, Smeets P, Van Hoof T, Vergauwen M, Dewaele T, Van Borsel M, Achten E, Verstraete K, D'Herde K, Thierens H, Bacher K - BMC Med Imaging (2015)

Bottom Line: Potential dose reduction based on clinical image quality varied from 27 to 37.4%, depending on the strength of SAFIRE.Our results demonstrate that noise assessments in a uniform phantom overestimate the potential dose reduction for the SAFIRE IR algorithm.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Basic Medical Sciences, Ghent University, Proeftuinstraat 86, B-9000, Ghent, Belgium. An.decrop@ugent.be.

ABSTRACT

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.

Conclusion: 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.

No MeSH data available.


Catphan@504 phantom. The figure represents a CT image of the Catphan phantom. On the left, the CT number linearity and CT number accuracy module, which includes samples of teflon and acrylic used to calculate the CNR. In the middle, the low contrast module containing targets with different contrast levels: 1, 0.5 and 0.3 %. Each contrast level has 9 targets with different diameters: 15, 9, 8, 7, 6, 5, 4, 3, 2 mm. On the right the image uniformity module
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4541737&req=5

Fig2: Catphan@504 phantom. The figure represents a CT image of the Catphan phantom. On the left, the CT number linearity and CT number accuracy module, which includes samples of teflon and acrylic used to calculate the CNR. In the middle, the low contrast module containing targets with different contrast levels: 1, 0.5 and 0.3 %. Each contrast level has 9 targets with different diameters: 15, 9, 8, 7, 6, 5, 4, 3, 2 mm. On the right the image uniformity module

Mentions: To evaluate the physical-technical image quality the Catphan@504 phantom (The Phantom laboratory, Salem, New York, USA) was used. The phantom consists of several modules to evaluate high and low contrast resolution, CNR and noise (Fig. 2). In the low contrast module there are three areas with different contrast levels: 1, 0.5 and 0.3 %. Each contrast level contains targets with decreasing diameters (15, 9, 8, 7, 6, 5, 4, 3 and 2 mm). The CT number linearity and CT number accuracy module contains targets made from teflon, delrin, acrylic, polystyrene, low density polyethylene (LDPE), polymethylpentene (PMP) and air. The image uniformity module is made from a uniform material. The material’s CT number is designed to be within 2 % (20 HU) of water’s density at standard scanning protocols.Fig. 2


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

De Crop A, Smeets P, Van Hoof T, Vergauwen M, Dewaele T, Van Borsel M, Achten E, Verstraete K, D'Herde K, Thierens H, Bacher K - BMC Med Imaging (2015)

Catphan@504 phantom. The figure represents a CT image of the Catphan phantom. On the left, the CT number linearity and CT number accuracy module, which includes samples of teflon and acrylic used to calculate the CNR. In the middle, the low contrast module containing targets with different contrast levels: 1, 0.5 and 0.3 %. Each contrast level has 9 targets with different diameters: 15, 9, 8, 7, 6, 5, 4, 3, 2 mm. On the right the image uniformity module
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4541737&req=5

Fig2: Catphan@504 phantom. The figure represents a CT image of the Catphan phantom. On the left, the CT number linearity and CT number accuracy module, which includes samples of teflon and acrylic used to calculate the CNR. In the middle, the low contrast module containing targets with different contrast levels: 1, 0.5 and 0.3 %. Each contrast level has 9 targets with different diameters: 15, 9, 8, 7, 6, 5, 4, 3, 2 mm. On the right the image uniformity module
Mentions: To evaluate the physical-technical image quality the Catphan@504 phantom (The Phantom laboratory, Salem, New York, USA) was used. The phantom consists of several modules to evaluate high and low contrast resolution, CNR and noise (Fig. 2). In the low contrast module there are three areas with different contrast levels: 1, 0.5 and 0.3 %. Each contrast level contains targets with decreasing diameters (15, 9, 8, 7, 6, 5, 4, 3 and 2 mm). The CT number linearity and CT number accuracy module contains targets made from teflon, delrin, acrylic, polystyrene, low density polyethylene (LDPE), polymethylpentene (PMP) and air. The image uniformity module is made from a uniform material. The material’s CT number is designed to be within 2 % (20 HU) of water’s density at standard scanning protocols.Fig. 2

Bottom Line: Potential dose reduction based on clinical image quality varied from 27 to 37.4%, depending on the strength of SAFIRE.Our results demonstrate that noise assessments in a uniform phantom overestimate the potential dose reduction for the SAFIRE IR algorithm.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Basic Medical Sciences, Ghent University, Proeftuinstraat 86, B-9000, Ghent, Belgium. An.decrop@ugent.be.

ABSTRACT

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.

Conclusion: 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.

No MeSH data available.