Assessment of the CT image quality for lung nodule using different field of view and matrix:a phantom study / 实用放射学杂志

ABSTRACT

Objective To assess the CT image quality of the pure ground glass nodule(pGGN)in chest phantom by using different field of view(FOV)and matrix.Methods CT(Philips Brilliance 128 spiral CT)scans were performed on chest phantom containing 9 artificial pGGNs(diameter≥5 mm)in 3 different FOV (50 mm,150 mm,300 mm ),and were reconstructed in 2 different matrix(512×512, 1 024×1 024),standard kernel.Recorded the CT values and standard deviations (SD)of the nodules and surrounding regions in different FOV and matrix,and calculated the mean standard deviation(MSD),contrast noise ratio (CNR)and signal noise ratio (SNR),then compared the difference among them.Two radiologists assessed the image quality of the pGGNs in blind method respectively,then evaluated the coherence between them using Kappa testing.Results The coherence of 2 observers was substantial or almost perfect.No significant differences were found on MSD,CNR and SNR in different FOV (P value>0.05)when matrix was kept,whereas the visibility of the nodules improved with the FOV changing smaller.And there were significant differences all on MSD,CNR and SNR by using different matrix when FOV was kept.The MSD increased and the CNR,SNR decreased in high-resolution group.The visibility of the pGGNs was not improved obviously in high-resolution group.Conclusion The image quality of the pGGN(diameter≥5 mm)won’t be changed by using smaller FOV when matrix is kept ,but the visibility will be improved with the FOV changing smaller.When FOV is kept,the MSD increased and the CNR,SNR reduced in high-resolution group,but the visibility will not be improved obviously compare to the standard resolution group.