Pulmonary andAortic BloodFlowMeasurements in NormalSubjects andPatients AfterSingle Lung Transplantation at0.5TUsing Velocity Encoded

Purpose: Itisthepurpose ofthisstudy tocomparepulmonary andaortic blood flow measure¬ mentsobtained inpatients after single lung transplantation (SLTX) withthose involunteers. Methods/material: Inninepatients after SLTX(three male, sixfemale) andninevolunteers (seven male, twofemale), double oblique phase contrast cine-MRI sequences perpendicular tothedirection ofblood flow were obtained intheascending aorta, main, right, andleft pulmonary artery on a0.5-T unit(Philips Gyroscan; Best, theNetherlands) (repetition time, 600to800ms;echotime, 8ms; alpha=30; field ofview=280 mm matrix, 128x256, ECG gating, temporal resolution 16time frames/RR interval). Aninitial invitro study using the same sequence on anonpulsatile flowphantom showed excellent correlation (r=0.99) between MRImeasurementsofflowvelocity andflow volume andtruevelocity andflow volume. Measurements ofblood flow volume(mL/min), peak mean systolic velocity, resistive index, anddistensibility index were obtained ineachvessel. Results: We foundexcellent correlations between left andright cardiac output as measured by velocity encoded cine-MRI(VEC-MRI) intheascending aortaandmainpulmonary artery bothin normal volunteers (r=0.95) andinpatients (r=0.91). Differential pulmonary blood flow measure¬ mentsinvolunteers showed that 55%oftheright cardiac output was directed totheright and45% totheleft lung. Differential pulmonary blood flow inpatients showed that mostoftheblood flow (81%) reaches thetransplanted lung andonly 19%reaches thepatient's own lung (SLTX: 4.5±1.8 L/min, patient's own lung: 1.2±0.8 L/min). There were significant differences (p<0.05) inpeak mean systolic velocity andresistive index obtained inthepulmonary arteries, bothbetween normal volunteers andpatients andbetween measurementsobtained inthepatient's own lung andthe transplanted lung. Conclusion: VEC-MRIblood flow measurements are a promising noninvasive tool tomonitor the hemodynamic changes ofpulmonary blood flowafter SLTX. (CHEST 1998; 114:771-779)