Purpose
To determine the capability of Iterative Model Reconstruction (IMR-Philips) as dose reducing method in clinical practice.
Methods and materials
CT-scan of the thorax (iCT Philips Healthcare,
Best,
The Netherlands) was performed with standard care (120 kV,
auto-mA,
iDose4,
thickness 0.9 mm,
reconstruction interval 0.7 mm) and low dose (50% of initial dose) in 10 patients over 65 years old.
The images we interpretated at a thickness of 3 mm.
The low dose CT-scan was also reconstructed with a prototype model-based reconstructor (IMR,
Philips) using filter Body Sharp Plus level 1 and 2 (thickness 1 mm).
Level 2 provides more noise reduction than level 1....
Results
IMR-low dose is superior to standard CT-scan in detecting and delineating ground glass nodules (L2 4.8 ± 0.4).
Only one patient showed emphysema,
remarkably well seen on IMR and barely seen on conventional CT.IMR-low dose showed at least acceptable image quality for detection ofsmall pulmonary vessels (L1/L2 3.7 ± 0.5) and delineation of the pleura (L1 4.1 ± 0.5)and mediastinal wall (L1 3.8 ± 0.4).
This result is due to the very drastic reduction in image noise and artifacts by the new developped model-based iterative...
Conclusion
The demand for dose reduction pushes the radiologist to lower the dose.
This tendency may end in a loss of diagnostic quality,
if only statistical iterative reconstruction levels are used.
The pathology mostly affected by lowering the dose in CT thorax are ground glass nodules,
mosaic perfusion,
emfysema,...
Iterative model-based reconstruction shows a potential to recover this pathology at low dose levels,
making it possible to scan more savely at low dose levels.
Besides that,
iterative model-based reconstruction shows a potential as dose reducing reconstruction...
References
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Conventional CT image quality metrics: do they make sense in the era of iterative reconstruction? MDCT symposium of the International Society of Computed Tomography,
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Martinsen et all.
Improved image quality...