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A study of the image quality of CT brain adaptive statistical iterative reconstructed (ASIR) images using subjective and objective methods

Författare och institution:
Jasvinder Mangat (-); J Morgan (-); P Clinch (-); A Reilly (-); Magnus Båth (Institutionen för kliniska vetenskaper, sektionen för onkologi, radiofysik, radiologi och urologi, Avdelningen för radiofysik); J Clinch (-); E Chaloner (-); M Lewis (-)
Publicerad i:
Optimisation in X-ray and Molecular Imaging 2015 - the Fourth Malmö Conference on Medical Imaging, Gothenburg, Sweden, 28-30 May 2015,
Konferensbidrag - refereegranskat abstract
Fulltextlänk (lokalt arkiv):
Sammanfattning (abstract):
Purpose: The aim of this study was to investigate the image quality of ASIR reconstructed brain images using subjective, observer-based assessment and objective metrics to elucidate trends and possible alternatives to the current standard protocol featuring 40%ASIR and a noise index of 11.20, possibly facilitating a dose decrease. Method: An audit of image quality of patient brain scans (n=55) was performed using Visual Grading Assessment (VGA) by two radiologist-observers, using CEC image criteria of retrospectively reconstructed images at 0% -70% & 100% ASIR-levels originally scanned using the standard protocol. Analysis was conducted using Visual Grading Characteristics (VGC). Empirical phantom-based assessments of high-contrast spatial resolution (HCSR) and Noise Power Spectrum (NPS) with 0-100%ASIR increments and decrementing tube currents (565-235mA), were also conducted. Results: VGC analysis showed that the mid-range increments (50%-70%ASIR) were not significantly different to 40%ASIR (p>0.05). Low-contrast spatial resolution (LCSR) showed slight, non-significant improvement with 70% and 60%ASIR increments compared with 40%ASIR (p>0.05). Subjective image noise remained constant across this range, but was slightly worse than 40%ASIR (p>0.05). However, 70%ASIR reconstructions were found to be overly susceptible to artefact appearance. Hence pairwise-analysis was performed using 60% & 50%ASIR, which showed 60%ASIR was the preferred increment. Phantom-based HCSR investigations showed MTF50 and MTF10 increases of up-to 4.1% and 3.0%, respectively (p<0.05) for ASIR reconstructed images as compared to those produced using FBP. MTF50 and MTF10 showed a linearly improving relationship with increasing %ASIR. With tube current, MTF behaviour was more complex with a rapid increase up to 305mA, a plateau between 305 and 420mA and then a rapid fall off. The NPS study revealed peak-frequency decreased linearly with increasing %ASIR and remained constant with tube current. Peak-variance decreased non-linearly with %ASIR and tube current. Empirical ranges for MTF50, MTF10, peak frequency NPS & peak variance NPS of (0.370- 0.375mm-1), (0.617- 0.622mm-1), (0.199- 0.176mm-1) & (99.28- 84.92mm-1) respectively, were obtained for the standard protocol for the mid-range ASIR increments. Conclusion: This study demonstrated the trends for objective and subjective image quality metrics with ASIR increment and tube-current. 60%ASIR with a tube current of 305mA (NI=12.20) was proposed as an alternative to the current standard, as it was the best fit with these empirical ranges, producing a possible dose saving of 16.1%.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
Klinisk medicin ->
Radiologi och bildbehandling ->
Klinisk medicin ->
Radiologi och bildbehandling ->
Postens nummer:
Posten skapad:
2016-04-27 18:02
Posten ändrad:
2016-05-09 11:20

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