Thrombus imaging in acute ischaemic stroke using thin-slice unenhanced CT: comparison of conventional sequential CT and helical CT.

OBJECTIVES

Thin-slice helical unenhanced CT can be used for thrombus imaging but increases radiation exposure. Conventional sequential images obtained by multidetector CT can be reconstructed into thin-slice images. The purpose of this study was to evaluate if conventional sequential unenhanced CT images can replace helical unenhanced CT for thrombus imaging.

METHODS

Fifty consecutive patients with acute ischaemic stroke underwent both 5-mm conventional sequential unenhanced CT and helical unenhanced CT. Each of the sequential and helical unenhanced CT images was subsequently reconstructed into four 1.25-mm images. Thrombus volumes and HU were measured semi-automatically using both types of unenhanced CT. Thrombus HU ratio (rHU) was calculated using the HU of the contralateral segment. The intraclass correlation coefficient (ICC) and Bland-Altman plots were used to assess measurement agreement.

RESULTS

The mean rHUs were 1.47 ± 0.17 for sequential unenhanced CT and 1.47 ± 0.18 helical unenhanced CT (P = 0.542). The mean thrombus volumes were 124.25 ± 125.65 mm(3) and 117.84 ± 124.32 mm(3) on sequential and helical unenhanced CT images, respectively (P = 0.063). Measurement agreement between thrombus volumes from the two unenhanced CT images was high (ICC = 0.981).

CONCLUSIONS

Thin-slice unenhanced CT images reconstructed from 5-mm sequential images can replace helical unenhanced CT for thrombus imaging in acute ischaemic stroke.

KEY POINTS

• Unenhanced CT is used to evaluate intra-arterial thrombus. • Thrombus HU and volume measurements using sequential or helical CT are comparable. • Conventional sequential images can replace helical CT for thrombus imaging. • Radiation dose for thrombus imaging can be reduced using sequential CT.