Radiation dose and clinical value of whole-brain CT perfusion imaging in the assessment of collateral circulation / 中华放射医学与防护杂志

ABSTRACT

Objective:To assess the radiation dose and clinical value of "one-stop" whole-brain CT perfusion (CTP) imaging in the evaluation of collateral circulation for patients with acute ischemic stroke (AIS), regarding the digital subtraction angiography (DSA) as the reference.Methods:This retrospective study included 32 AIS patients, for whom both CTP and DSA were obtained <24 h since onset. All CTP scans were acquired in whole-brain volume perfusion mode using a 320-row CT with the phase-specific settings of tube currents to optimize the image quality of CTA images, where multiple-phase (mp) CTA images were extracted from the CTP data in post-processing. The volume CT dose index (CTDI vol), dose length product (DLP), and effective dose were compared to those reported in previous studies. The perfusion parameters of the infarct lesions and their contralateral regions were compared using the paired t-tests. One radiologist scored the collateral circulation with only the CTP and with the CTP plus mp-CTA using a 5-point scale. Another radiologist performed the same evaluation on the DSA. The diagnostic accuracy was calculated referring to the result based on DSA. The scores were analyzed using the Pearson correlation coefficient. The agreement of scores was quantified with the Kappa test. Results:The mean CTDI vol was 184.18 mGy, which was comparable to the result of a previous study (184.19 mGy), and the mean effective dose was reduced 39% compared to that reported in the literature for combined CTP and CTA scanning (6.1 vs 10 mSv). There were statistically significant differences in cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), transit time to peak (TTP), and time-to-maximum (Tmax) between the infarct lesions and their contralateral regions ( P<0.01). The scores between CTP and DSA were significantly correlated ( r=0.95, P<0.01), as well as the scores between CTP plus mp-CTA and DSA ( r=0.98, P<0.01). The Kappa value was 0.64 ( t=7.53, P<0.01) between CTP and DSA, while it increased to 0.88 ( t=9.99, P<0.01) for CTP plus mp-CTA. With the result of DSA as a reference, the diagnostic accuracy was 71.9% and 90.6% for CTP and CTP plus mp-CTA, respectively. Conclusions:The "one-stop" whole-brain CTP imaging with phase-specific settings of tube currents can provide reliable CTP and multiple-phase CTA images simultaneously, which could reasonably reduce the radiation dose. Combined use of multi-phase CTA and CT perfusion improves the diagnostic accuracy of collateral circulation in AIS patients.