Chronic Thromboembolic Pulmonary Hypertension Perioperative Monitoring Using Phase‐Resolved Functional Lung (PREFUL)‐MRI

Abstract

BackgroundThe translation of phase‐resolved functional lung (PREFUL)‐MRI to routine practice in monitoring chronic thromboembolic pulmonary hypertension (CTEPH) still requires clinical corresponding imaging biomarkers of pulmonary vascular disease.PurposeTo evaluate successful pulmonary endarterectomy (PEA) via PREFUL‐MRI with pulmonary pulse wave transit time (pPTT).Study TypeRetrospective.PopulationThirty CTEPH patients and 12 healthy controls were included.Field Strength/SequenceFor PREFUL‐MRI a 2D spoiled gradient echo sequence and for DCE‐MRI a 3D time‐resolved angiography with stochastic trajectories (TWIST) sequence were performed on 1.5T.AssessmentEight coronal slices of PREFUL‐MRI were obtained on consecutive 13 days before and 14 days after PEA. PREFUL quantitative lung perfusion (PREFULQ) phases over the whole cardiac cycle were calculated to quantify pPTT, the time the pulmonary pulse wave travels from the central pulmonary arteries to the pulmonary capillaries. Also, perfusion defect percentage based on pPTT (QDPpPTT), PREFULQ (QDPPREFUL), and V/Q match were calculated. For DCE‐MRI, pulmonary blood flow (PBF) and QDPPBF were computed as reference. For clinical correlation, mean pulmonary arterial pressure (mPAP) and 6‐minute walking distance were evaluated preoperatively and after PEA.Statistical TestsThe Shapiro–Wilk test, paired two‐sided Wilcoxon rank sum test, Dice coefficient, and Spearman's correlation coefficient (ρ) were applied.ResultsMedian pPTT was significantly lower post PEA (139 msec) compared to pre PEA (193 msec), P = 0.0002. Median pPTT correlated significantly with the mPAP post PEA (r = 0.52, P < 0.008). Median pPTT was distributed more homogeneously after PEA: IQR pPTT decreased from 336 to 281 msec (P < 0.004). Median PREFULQ (P < 0.0002), QDPpPTT (P < 0.0478), QDPPREFUL (P < 0.0001) and V/Q match (P < 0.0001) improved significantly after PEA. Percentage change of PREFULQ correlated significantly with percentage change of 6‐minute walking distance (ρ = 0.61; P = 0.0031) 5 months post PEA.Data ConclusionPerioperative perfusion changes in CTEPH can be detected and quantified by PREFUL‐MRI. Normalization of pPTT reflects surgical success and improvement of PREFULQ predicts 6‐minute walking distance changes.Level of Evidence3Technical Efficacy Stage2 J. Magn. Reson. Imaging 2020;52:610–619.

Repeatability of Phase‐Resolved Functional Lung (PREFUL)‐MRI Ventilation and Perfusion Parameters in Healthy Subjects and COPD Patients

“…Interestingly, pPTT was repeatable in both COPD and healthy subjects. As described before, 29 pPTT measures the conduction time of the pulse wave through the pulmonary arterial vessels. The exact effects of the pulse wave and its velocity on the phase signal in different diseases has to be examined in future studies.…”

“…For every slice, a Q‐weighted phase was selected automatically, 16 and the signal of the full blood voxel defined above from the middle slice was used to normalize perfusion values (Q N ). Based on the reconstructed cardiac cycle, a pulmonary pulse wave transit time (pPTT) map, a physiological description of the time the pulse wave travels from the main pulmonary artery to the lung parenchyma, was computed using a manually segmented healthy parenchyma ROI 29 . The manual segmentation of the healthy parenchyma of the pPTT calculation was performed blinded by two observers with over 6 years of experience in lung segmentation.…”

“…pPTT is a noninvasive dynamic marker of pulmonary vascular disease. 29 S Exp and S Insp are the averaged signals of the end-expiratory and end-inspiratory images. S Mean is defined as the mean signal of the intermediate lung inflation level images.…”

Cardiac Magnetic Resonance in Pulmonary Hypertension—an Update

“…Perfusion MRI identified all cases of CTEPH and had comparable sensitivity and specificity to the other modalities. Recent studies have shown that ventilation and perfusion changes in CTEPH can be interrogated using phase-resolved functional lung MRI without the need for contrast agents [74]. Perfusion MRI is likely to play an essential role in the diagnostic pathway in centres that already perform CMR for CTEPH patients.…”

Chronic thromboembolic pulmonary hypertension: diagnosis, operability assessment and patient selection for pulmonary endarterectomy

“…Additionally, Phase-Resolved Functional Lung (PREFUL)-MRI could detect and quantify hemodynamic changes in CTEPH. The initial results of this technique are promising, considering no intravenous contrast is required (44). Therefore, a combination of CTPA for morphological delineation and MRI for functional and pulmonary vascular assessment with pulmonary angiography reserved as a problem-solving tool has been proposed in previous diagnostic algorithms.…”