| Objective: CT perfusion(CTP)source images reconstructed with iterative model reconstruction(IMR)algorithm can reconstruct multi-phase CT perfusion angiography(CTPA)without increasing radiation dose and contrast agent.The study was to explore the value of multi-phase CTPA derived from low-dose CTP source volume datasets reconstructed with IMR algorithm on evaluating collateral circulation in patients with unilateral middle cerebral artery(MCA)steno-occlusion and moyamoya disease(MMD).Methods: The study included two main parts: 1.Sixty-eight patients with unilateral MCA steno-occlusion underwent non-contrast CT(NCCT),CTP and CT angiography(CTA).Multiphase CTPA images were reconstructed from CTP source volume data.We evaluated the subjective image quality of CTP parameter maps,compared the vascular attenuation,image noise,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR)of CTPA with routine CTA by using Student’s t test or Wilcoxon signed-rank test when data did not follow normal distribution.Wilcoxon signed-rank test was used to compare subjective image quality and collateral score.2.Eighteen patients with moyamoya disease confirmed by digital subtraction angiography(DSA)underwent NCCT,CTP and CTA.Multi-phase CTPA images were reconstructed from CTP source volume data.The subjective evaluation of image quality was performed.Multiphase CTPA and DSA were used to analyze the consistency and correlation of collateral vessels using DSA as the “gold standard”.Results: 1.The subjective image quality score of CTP parameters maps was 7.28±1.09,of which 3(4%)patients scored 4,3(4%)patients scored 5,6(9%)patients scored 6,16(24%)patients scored 7,40(59%)patients scored 8.Fifty-six(83%)patients of CTP parameters maps were considered to be of good quality and can meet the need of diagnosis.The subjective image quality of CTPA images was good,the edges of blood vessels were smooth,distal branches were clearly displayed,and the image quality met clinical diagnostic needs.The arterial enhancement,depiction of small arterial detail,image noise,and venous contamination of CTPA were higher than that of CTA(all,P < 0.05).The vascular attenuation(390.94±78.02 vs.116.13±52.66),SNR(17.07±10.11 vs.13.00±6.80)and CNR(14.95±8.74 vs.5.42±2.87)of CTPA were higher than that of CTA(all,P < 0.05).The image noise of CTPA was higher than that of CTA(P < 0.001).Collaterals were rated higher on CTPA compared with CTA(1.79±0.64 vs.1.22±0.77,P<0.001).The CTA can only show some main cerebral arteries in the arterial phase,while CTPA can show the collateral vessels in the delayed phases.Compared with CTA,CTPA was rated with higher collateral grades in 54%(37/68)of cases,equal in 46%(31/68)of cases.Collateral circulation was assessed as good in 71%(48/68)of cases on CTPA,compared with only 31%(21/68)of cases on conventional CTA.Some collaterals that were not visible on single-phase CTA,were visible on multi-phase CTPA images.2.The subjective image quality score of CTP parameters maps was 2.83±0.38.The subjective image quality of CTPA images was good,the edges of blood vessels were smooth,distal branches were clearly displayed,and the image quality met clinical diagnostic needs.Multi-phase CTPA showed good consistency and correlation with DSA in collateral vessels evaluations(Kappa = 0.778),(r = 0.864,P < 0.01).The interobserver agreement was good(Kappa=0.792).Conclusion: CTP reconstructed with IMR algorithm can significantly reduce radiation dose.It can not only obtain brain perfusion information,but also reconstruct multi-phase CTPA images.Multi-phase CTPA images can satisfy the clinical diagnosis needs and accurately evaluate collateral circulation in patients with unilateral MCA steno-occlusion and MMD. |
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