The Effect of Axial and Spiral Scan Mode in Emergency Head CT on Image Quality and Radiation Dosage

Objective: to study the effect of axial and spiral scan mode in head CT on image quality and radiation dosage, and provide the evidence for emergency patient to choice the reasonable scanning mode. Methods: A total of 20 patients were taken the emergency CT with spiral scan mode and with axial scan mode in the first recheck. Scan parameters: 120 k V, 290 m A, 0.8 s/rol, slice thickness 5 mm, scanning interval 5 mm, pitch 0.969:1, standard reconstruction algorithm. To measure the CT value and background noise of the white matter and grey matter and calculate the SNR and CNR, and evaluate image noise, artifacts of the skull base, gray matter-white matter differentiation. After scanning, the radiation dosage was obtained from the dose report. Paired sample t test and chi-square test were used to compare the difference of image quality between two scanning modes. Results: Using axial scanning mode, the CT value of grey matter and white matter was(38.02 ±2.23)HU and(27.01 ±1.72)HU respectively, and using spiral scanning mode, the CT value of grey matter and white matter was(37.76 ±2.22) HU and(26.99 ±1.69) HU respectively. There is no significant difference in CT value, SNR, CNR between two modes(P > 0.05, t = 0.045, 0.119, 0.502). There is no significant difference in image noise, artifacts of the skull base, the scores of grey matter-white matter differentiation between two modes(P > 0.05, χ²= 3.142, 0.0, 3.159). Effective doses was 66 m Sv in spiral mode, and 43 m Sv in axial mode, but the scanning time of spiral mode is shorter, and the reconstruction is helpful to the diagnosis. Conclusions: In term of both image quality and radiation dosage, the axial scanning mode is the preferred choice in the emergency head CT, but spiral scanning mode should be taken for the restless and non-cooperative patients.