Two-Volume Dynamic CT Pulmonary Perfusion: Contrast Timing Optimization

Abstract

\n PurposeTo develop and validate an optimal timing protocol for a low-radiation-dose CT pulmonary perfusion technique using only two volume scans.MethodsA total of 24 swine (48.5\u2009±\u200914.3 kg) underwent contrast-enhanced dynamic CT. Multiple contrast injections were made under different pulmonary perfusion conditions, resulting in a total of 147 complete pulmonary arterial input functions(AIF). Using the AIFs, an optimal timing protocol for acquisition of two-volume scans was developed for the first-pass CT perfusion technique. Specifically, the first volume scan was obtained at the base of the AIF using bolus-tracking and the second volume scan was obtained at the peak of the AIF using a time-to-peak relation derived by regression analysis. Additionally, a subset of 14 swine with 60 CT acquisitions were used to validate the prospective timing protocol. The prospective perfusion measurements using the two-volume scans, were quantitatively compared to the retrospective perfusion measurements using the entire AIF with t-test, linear regression and Bland-Altman analysis. The CT dose index(CTDI32vol) and size-specific dose estimate(SSDE) of the two-volume perfusion technique were also determined.ResultsThe pulmonary artery time-to-peak (TPA) was related to one-half of the contrast injection duration(TInj/2) by TPA = 1.06 TInj/2+0.090 (r=0.97). Simulated prospective two-volume perfusion measurements (P\xad\xadPRO) in ml/min/g were related to the retrospective measurements (PRETRO) by PPRO= 0.87PRETRO + 0.56 (r=0.88). The CTDI32vol and SSDE of the two-volume CT technique were estimated to be 28.4 and 47.0mGy, respectively.ConclusionThe optimal timing protocol can enable an accurate, low-radiation-dose two-volume dynamic CT perfusion technique.