| Objective To investigate the feasibility of virtual non-contrast CT images instead of conventional non-contrast CT images in CT imaging of urinary system.It is in order to optimize the imaging of the urinary system and reduce the radiation dose of the patient.Methods 24 patients were enrolled in this study.The objective parameters(noise,contrast-to-noise ratio,radiation dose,stone size)and the subjective score of two doctors were measured and compared in the two groups of non-contrast scan and discharge stage virtual non-contrast scan respectively in field of vision.Paired t test was used for analysis of objective indexes and rank sum test was used for analysis of subjective scores of image quality.Results In virtual non-contrast CT images,the renocortical noise was(10.31±2.34),the renal medullary noise was(10.64±2.76),the contrast to noise ratio of cortex renis was(2.37±0.98)and the contrast to noise ratio of renal medullary was(2.14±1.08).In conventional non-contrast CT images,the renocortical noise was(9.56±1.46),the renal medullary noise was(9.46±1.57),the contrast to noise ratio of cortex renis was(2.42±0.97)and the contrast to noise ratio of renal medullary was(2.40±1.14).There was no significant difference in contrast to noise ratio and the noise between virtual non-contrast CT images and conventional non-contrast CT images.The volume CT dose index of CT CT virtual urography was(21.62±2.46)m Gy,and the dose length product was(1069.05±122.46)m Gy? Cm,and the effective radiation dose was(16.04±1.84)m SV.The conventional CT urography in patients receiving CT dose index volume is(29.07±2.85)m Gy,dose length product(1440.17±158.01)for m Gy,cm,effective radiation dose was(21.60±2.37)m SV,the difference was statistically significant(P<0.05),effective radiation dose was reduced by 25.74%.The average diameter of the stone larger than 10 mm was about(18.06±6.48)mm,and the average diameter of the virtual plain scan was about(17.98±6.35)mm.The average diameter of 6~10mm’s stone was about(7.83±1.15)mm on the traditional plain scan image,and the average diameter of the virtual plain scan was about(7.73±0.89)mm.The average diameter of 3~5mm stone was about(4.19±0.48)mm,and the average diameter of the virtual plain scan was about(4.00±0.46)mm.The stone was 3mm in TNC and VNC images on the diameter of the difference was not statistically significant.There was no difference in the detection of stones above 6mm between traditional and virtual plain images.3~5mm stones were missing in VNC images,with a detection rate of over 90%,and a small VNC below3 mm was not detected.The quality of TNC and VNC images was highly consistent with the two radiologists,and the value of Kappa was >0.6.Two radiologists on the VNC image score from 3 points and 4 points,for the TNC image score from 4 points and 5points,the subjective score greater than or equal to 3 points.Conclusion In CT urinary imaging,the use of spectral virtual reality CT instead of routine scan not only saves patient’s examination time and cost,but also effectively reduces radiation dose when the image quality meets the needs of clinical diagnosis. |
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