Correlations of different CT scanning parameters and the effect of iterative metal artifact reduction algorithm

Gang PENG

ABSTRACT

Objective:

To observe the impact of different CT scanning parameters on the effect of reducing metal artifacts with iterative metal artifact reduction (IMAR) algorithm.

Methods:

CT scans of an anthropomorphic chest phantom were performed before and after implantation of spinal screws using different tube voltage and different tube current combinations under different radiation dose conditions. Then the data were reconstructed with iterative reconstruction and IMAR algorithm, respectively. Subjective evaluation of images quality of IMAR was performed by using 4-point method. CT values, noise (standard deviation of CT value, SD) and CT value deviation (ΔHU) of lung tissue and vertebral soft tissue adjacent metal screws were measured and calculated. The differences of image quality collected with various methods were compared.

Results:

Under the same tube current condition, metal artifacts of IMAR images decreased with the increase of tube voltage, and statistical difference of subjective evaluation score of image quality was found (P<0.05). SD and ΔHU of lung parenchyma and paravertebral soft tissue decreased with the increase of tube voltage(r=-0.91, -0.99, 0.85, -0.97, all P<0.01),while the former was mildly (r=0.20, 0.29, all P<0.01)and the latter was moderately negatively related with the increase of tube current(r=-0.59, -0.56, all P<0.01). Under different radiation dose of different combination of tube voltage and tube current, there were statistical differences of both subjective scores and objective index for image quality (both P<0.05). Compared with the condition combination of medium or high radiation dose, metal artifact reduced under low radiation dose using combination of high voltage and low tube current.

Conclusion:

Tube voltage has main impact on imaging quality of IMAR algorithm. For metal artifact reduction with IMAR, better imaging quality can be obtained through increasing tube voltage, and reducing tube current at the same time is able to limit the impact of metal artifacts on image quality and decrease radiation dose.