Assessment Of Lung Perfusion Research Articles

Feasibility of quantitative evaluation of hemodynamics using SPECT/CT in patients with chronic thromboembolic pulmonary hypertension

Abstract Background A ventilation/perfusion (V/Q) lung scan is recommended in the diagnostic work-up of patients with newly diagnosed pulmonary hypertension to rule out chronic thromboembolic pulmonary hypertension (CTEPH). V/Q single-photon emission computed tomography (SPECT) is considered the method of choice for diagnosis in CTEPH because it allows more precise evaluation than planar imaging. However, the evaluation of lung perfusion using V/Q SPECT imaging remains mainly a qualitative evaluation, and no quantitative method has been established. We hypothesized that the standardized uptake value (SUV) technique in Positron Emission Tomography (PET)-CT, a nuclear imaging technique well suited for quantitative of tumor biology, could be applied to quantitative assessment of lung perfusion. Purpose The purpose of this study was to evaluate the correlation between pulmonary perfusion distribution and hemodynamic data in Tc-labeled large-assembly albumin (99mTc-MAA) SPECT images in order to determine the feasibility of SPECT/CT for quantitative assessment of lung perfusion. Methods Twenty-five patients with CTEPH who underwent BPA and received SPECT-CT were included. Since the injected 99mTc-MAA selectively accumulates only in the lungs, SUV normalization was conducted using each patient’s lung volume, calculated by SPECT/CT and defined as SUV lung volume (LV) . The percentage of lung volume below each SUVLV value in total lung volume on SPECT/CT was examined before BPA, after two procedures of BPA, and six months after a series of BPA, and the correlations with hemodynamic parameters on right heart catheterization at each time point were evaluated. Results The Percent lung volume below SUVLV of 0.7 in total lung volume before BPA, after two procedures of BPA, and six months after a series of BPA had the strongest correlation with mean pulmonary artery pressure (mPAP) (rs; 0.727, p<0.001, Figure 1). The percent lung volume below SUVLV of 0.7 decreased with the BPA procedure in each patient with CTEPH (Figure 2). Furthermore, receiver operating characteristic analysis revealed that a threshold for the percent lung volume below SUVLV of 0.7 of 50.3% or greater could identify mPAP greater than 21 mmHg for right heart catheterization (area under the curve = 0.86, 95% CI 0.78-0.94, p<0.001). Conclusion Percent lung volume below SUVLV of 0.7 in total lung volume using SPECT/CT might reflect the severity of hemodynamics in patients with CTEPH. This method would be feasible for quantitative assessment of lung perfusion, even inter-patient and intra-patient.Figure 1Figure 2

Pulmonary emphysema: the assessment of lung perfusion with Dual-Energy CT and pulmonary scintigraphy.

To assess the correlation of quantitative data of pulmonary Perfused Blood Volume (PBV) on Dual-Energy CT (DECT) datasets in patients with moderate - severe Pulmonary Emphysema (PE) with Lung Perfusion Scintigraphy (LPS) as the reference standard. The secondary endpoints are the correlation between the CT densitometric analysis and the visual assessment of parenchymal destruction with PBV. Patients with moderate - severe PE candidate to Lung Volumetric Reduction (LVR), with available a pre-procedural LS and a contrast-enhanced DECT were retrospectively included. DECT studies were performed with a 3rd generation Dual-Source CT and the PBV was obtained with a 3-material decomposition algorithm. The CT densitometric analysis was performed with a dedicated commercial software (Pulmo3D). The Goddard Score was used for visual assessment. The perfusion LS were performed after the administration of albumin macroaggregates labeled with 99mTechnetium. The image revision was performed by two radiologists or nuclear medicine physicians blinded, respectively, to LS and DECT data. The statistical analysis was performed with nonparametric tests. Thirty-one patients (18 males, median age 69 y.o., interquartile range 62-71 y.o.) with moderate - severe PE (Median Goddard Score 14/20 and 31% of emphysematous parenchyma at quantitative CT) candidate to LVR were retrospectively included. The median enhancement on PBV was 17 HU. Significant correlation coefficients were demonstrated between lung PBV and LS, poor in apical regions (Rho = 0.1-0.2) and fair (Rho = 0.3-0.5) in middle and lower regions. No significant correlations were recorded between the CT densitometric analysis, the visual score, and the PBV. Lung perfusion with PBV on DECT is feasible in patients with moderate - severe PE candidate to LVR, and has a poor to fair agreement with LPS.

Effects of different VV ECMO blood flow rates on lung perfusion assessment by hypertonic saline bolus-based electrical impedance tomography

ObjectiveOur study aimed to investigate the effects of different extracorporeal membrane oxygenation (ECMO) blood flow rates on lung perfusion assessment using the saline bolus-based electrical impedance tomography (EIT) technique in patients on veno-venous (VV) ECMO.MethodsIn this single-centered prospective physiological study, patients on VV ECMO who met the ECMO weaning criteria were assessed for lung perfusion using saline bolus-based EIT at various ECMO blood flow rates (gradually decreased from 4.5 L/min to 3.5 L/min, 2.5 L/min, 1.5 L/min, and finally to 0 L/min). Lung perfusion distribution, dead space, shunt, ventilation/perfusion matching, and recirculation fraction at different flow rates were compared.ResultsFifteen patients were included. As the ECMO blood flow rate decreased from 4.5 L/min to 0 L/min, the recirculation fraction decreased significantly. The main EIT-based findings were as follows. (1) Median lung perfusion significantly increased in region-of-interest (ROI) 2 and the ventral region [38.21 (34.93–42.16)% to 41.29 (35.32–43.75)%, p = 0.003, and 48.86 (45.53–58.96)% to 54.12 (45.07–61.16)%, p = 0.037, respectively], whereas it significantly decreased in ROI 4 and the dorsal region [7.87 (5.42–9.78)% to 6.08 (5.27–9.34)%, p = 0.049, and 51.14 (41.04–54.47)% to 45.88 (38.84–54.93)%, p = 0.037, respectively]. (2) Dead space significantly decreased, and ventilation/perfusion matching significantly increased in both the ventral and global regions. (3) No significant variations were observed in regional and global shunt.ConclusionsDuring VV ECMO, the ECMO blood flow rate, closely linked to recirculation fraction, could affect the accuracy of lung perfusion assessment using hypertonic saline bolus-based EIT.

Modulation of pulmonary blood flow in patients with acute respiratory failure

BackgroundImpairment of ventilation and perfusion (V/Q) matching is a common mechanism leading to hypoxemia in patients with acute respiratory failure requiring intensive care unit (ICU) admission. While ventilation has been thoroughly investigated, little progress has been made to monitor pulmonary perfusion at the bedside and treat impaired blood distribution. The study aimed to assess real-time changes in regional pulmonary perfusion in response to a therapeutic intervention. MethodsSingle-center prospective study that enrolled adult patients with ARDS caused by SARS-Cov-2 who were sedated, paralyzed, and mechanically ventilated. The distribution of pulmonary perfusion was assessed through electrical impedance tomography (EIT) after the injection of a 10-ml bolus of hypertonic saline. The therapeutic intervention consisted in the administration of inhaled nitric oxide (iNO), as rescue therapy for refractory hypoxemia. Each patient underwent two 15-min steps at 0 and 20 ppm iNO, respectively. At each step, respiratory, gas exchange, and hemodynamic parameters were recorded, and V/Q distribution was measured, with unchanged ventilatory settings. ResultsTen 65 [56–75] years old patients with moderate (40%) and severe (60%) ARDS were studied 10 [4-20] days after intubation. Gas exchange improved at 20 ppm iNO (PaO2/FiO2 from 86 ± 16 to 110 ± 30 mmHg, p = 0.001; venous admixture from 51 ± 8 to 45 ± 7%, p = 0.0045; dead space from 29 ± 8 to 25 ± 6%, p = 0.008). The respiratory system's elastic properties and ventilation distribution were unaltered by iNO. Hemodynamics did not change after gas initiation (cardiac output 7.6 ± 1.9 vs. 7.7 ± 1.9 L/min, p = 0.66). The EIT pixel perfusion maps showed a variety of patterns of changes in pulmonary blood flow, whose increase positively correlated with PaO2/FiO2 increase (R2 = 0.50, p = 0.049). ConclusionsThe assessment of lung perfusion is feasible at the bedside and blood distribution can be modulated with effects that are visualized in vivo. These findings might lay the foundations for testing new therapies aimed at optimizing the regional perfusion in the lungs.

Lung perfusion assessment in children with long-COVID: A pilot study.

There is increasing evidence that chronic endotheliopathy can play a role in patients with Post-Covid Condition (PCC, or Long Covid) by affecting peripheral vascularization. This pilot study aimed at assessing lung perfusion in children with Long-COVID with 99m Tc-MAA SPECT/CT. lung 99m Tc-MAA SPECT/CT was performed in children with Long-COVID and a pathological cardiopulmonary exercise testing (CPET). Intravenous injections were performed on patients in the supine position immediately before the planar scan according to the EANM guidelines for lung scintigraphy in children, followed by lung SPECT/CT acquisition. Reconstructed studies were visually analyzed. Clinical and biochemical data were collected during acute infection and follow-up in 14 children (6 females, mean age: 12.6 years) fulfilling Long-COVID diagnostic criteria and complaining of chronic fatigue and postexertional malaise after mild efforts, documented by CPET. Imaging results were compared with clinical scenarios during acute infection and follow-up. Six out of 14 (42.8%) children showed perfusion defects on 99m Tc-MAA SPECT/CT scan, without morphological alterations on coregistered CT. This pilot investigation confirmed previous data suggesting that a small subgroup of children can develop lung perfusion defects after severe acute respiratory syndrome coronavirus 2 infection. Larger cohort studies are needed to confirm these preliminary results, providing also a better understanding of which children may deserve this test and how to manage those with lung perfusion defects.

Hyperspectral imaging enables the differentiation of differentially inflated and perfused pulmonary tissue: a proof-of-concept study in pulmonary lobectomies for intersegmental plane mapping.

The identification of the intersegmental plane isa major interoperative challenges during pulmonary segmentectomies. The objective of this pilot study is to test the feasibility of lung perfusion assessment by Hyperspectral Imaging for identification of the intersegmental plane. A pilot study (clinicaltrials.org: NCT04784884) was conducted in patients with lung cancer. Measuring tissue oxygenation (StO2; upper tissue perfusion), organ hemoglobin index (OHI), near-infrared index (NIR; deeper tissue perfusion) and tissue water index (TWI), the Hyperspectral Imaging measurements were carried out in inflated (Pvent) and deflated pulmonary lobes (PnV) as well as in deflated pulmonary lobes with divided circulation (PnVC) before dissection of the lobar bronchus. A total of 341 measuring points were evaluated during pulmonary lobectomies. Pulmonary lobes showed a reduced StO2 (Pvent: 84.56%±3.92 vs. PnV: 63.62%±11.62 vs. PnVC: 39.20%±23.57; p<0.05) and NIR-perfusion (Pvent: 50.55±5.62 vs. PnV: 47.55±3.38 vs. PnVC: 27.60±9.33; p<0.05). There were no differences of OHI and TWI between the three groups. This pilot study demonstrates that HSI enables differentiation between different ventilated and perfused pulmonary tissue as a precondition for HSI segment mapping.

Lung Transplantation From Controlled and Uncontrolled Donation After Circulatory Death (DCD) Donors With Long Ischemic Times Managed by Simple Normothermic Ventilation and Ex-Vivo Lung Perfusion Assessment.

Donation after cardiac death (DCD) donors are still subject of studies. In this prospective cohort trial, we compared outcomes after lung transplantation (LT) of subjects receiving lungs from DCD donors with those of subjects receiving lungs from donation after brain death (DBD) donors (ClinicalTrial.gov: NCT02061462). Lungs from DCD donors were preserved in-vivo through normothermic ventilation, as per our protocol. We enrolled candidates for bilateral LT ≥14years. Candidates for multi-organ or re-LT, donors aged ≥65years, DCD category I or IV donors were excluded. We recorded clinical data on donors and recipients. Primary endpoint was 30-day mortality. Secondary endpoints were: duration of mechanical ventilation (MV), intensive care unit (ICU) length of stay, severe primary graft dysfunction (PGD3) and chronic lung allograft dysfunction (CLAD). 121 patients (110 DBD Group, 11 DCD Group) were enrolled. 30-day mortality and CLAD prevalence were nil in the DCD Group. DCD Group patients required longer MV (DCD Group: 2days, DBD Group: 1 day, p = 0.011). ICU length of stay and PGD3 rate were higher in DCD Group but did not significantly differ. LT with DCD grafts procured with our protocols appears safe, despite prolonged ischemia times.

Persistent isolated impairment of gas transfer following COVID-19 pneumonitis relates to perfusion defects on dual-energy computed tomography.

A novel iodine perfusion score correlates with breathlessness and D LCO in patients post-#COVID19 without obvious interstitial disease on CT, suggesting that lung perfusion assessment may be useful in patients without another cause of dyspnoea https://bit.ly/3U6E2f5.

Lung Perfusion Assessment in Pulmonary Embolism: Novel Semi-Automatic Lung Perfusion Software in Computed Tomography Pulmonary Angiography Compared to Traditional Lung Perfusion Scintigraphy

Lung Perfusion Assessment in Pulmonary Embolism: Novel Semi-Automatic Lung Perfusion Software in Computed Tomography Pulmonary Angiography Compared to Traditional Lung Perfusion Scintigraphy

Initial Case Series with a Novel Cold Storage System for Lung Transplantation

<h3>Purpose</h3> Hypothermia is used to slow the metabolic rate and degradation of donor organs. However, the most commonly used method, ice storage, assures neither a uniform nor an optimal preservation temperature for the organ. Although a recent report suggests that 10 ºC storage prolongs cellular preservation and prevents grade 3 primary graft dysfunction (PGD) in lungs transplanted following <i>ex vivo</i> lung perfusion assessment, these resources are not available at all centers. We report an early case series with a new FDA-approved device that provides temperature-regulated 4 ºC transport of donor lungs and an 8-hour storage time. <h3>Methods</h3> We retrospectively examined the outcomes of 9 patients who underwent bilateral lung transplantation over a 4-month period at our institution. Three patients received donor lungs transported using the novel preservation device (novel group), while 6 patients received donor lungs preserved in ice (standard group). PGD at 24, 48, and 72 hours was the primary outcome. Secondary outcomes included post-reperfusion P/F ratios, ventilation hours, days in ICU, length of stay (LOS), and death. <h3>Results</h3> The standard group recipients were older than the patients in the novel group (standard 64.0 ± 2.4 vs novel 59.3 ± 1.2 years, p = 0.004). Donor characteristics were similar between the two groups. There were no differences in either the total (397.5 ± 59.0 vs 352.7 ± 27.0 minutes, p = 0.16) or warm (46.9 ± 15.3 vs 45.0 ± 13.5 minutes, p = 0.79) ischemic times. Ten minutes after reperfusion, the median intraoperative P/F ratio was markedly better in the novel group (432.4, IQR 341.9-516.2) than the standard group (243.2, IQR 190.2-363.9). No PGD was observed in the novel group. In the standard group, grade 2 or 3 PGD was seen in 4 patients after 24 hours, 2 patients after 48 hours, and 3 patients after 72 hours. The novel group had a shorter LOS (38.0 ± 16.2 vs 16.3 ± 6.1 days, p = 0.04). There was 1 death in the standard ice group and no deaths in the novel device group (<i>n.s.</i>). <h3>Conclusion</h3> The novel preservation system regulates the temperature of donor lungs during transport and until implantation. Our early experience suggests that the novel device may minimize PGD, improve post-reperfusion P/F ratios, and shorten LOS. Analysis of larger cohorts in a randomized controlled study is recommended to validate these results.

Pulmonary Vasculitis on Dual-Phase 18F-FDG PET/CT in SAPHO Syndrome.

Pulmonary vasculitis is an uncommon type of vasculitis that may cause pulmonary artery stenosis with ensuing ischemic damage to lung tissue. 99mTc-macroaggregated albumin scintigraphy and iodine lung perfusion mapping are useful imaging modalities for assessment of lung perfusion but are not useful for assessing disease activity. On the other hand, 18F-FDG PET/CT is widely used for assessment of vasculitis activity but cannot provide perfusion information. We reported the clinical utility of dual-phase 18F-FDG PET/CT for pulmonary vasculitis in patients with SAPHO (synovitis-acne-pustulosis-hyperostosis-osteitis) syndrome.

Lung Perfusion Assessment by Bedside Electrical Impedance Tomography in Critically Ill Patients.

As a portable, radiation-free imaging modality, electrical impedance tomography (EIT) technology has shown promise in the bedside visual assessment of lung perfusion distribution in critically ill patients. The two main methods of EIT for assessing lung perfusion are the pulsatility and conductivity contrast (saline) bolus method. Increasing attention is being paid to the saline bolus EIT method in the evaluation of regional pulmonary perfusion in clinical practice. This study seeks to provide an overview of experimental and clinical studies with the aim of clarifying the progress made in the use of the saline bolus EIT method. Animal studies revealed that the saline bolus EIT method presented good consistency with single-photon emission CT (SPECT) in the evaluation of lung regional perfusion changes in various pathological conditions. Moreover, the saline bolus EIT method has been applied to assess the lung perfusion in a pulmonary embolism and the effect of positive end-expiratory pressure (PEEP) on regional ventilation/perfusion ratio (V/Q) and acute respiratory distress syndrome (ARDS) in several clinical studies. The implementation of saline boluses, data analyses, precision, and cutoff values varied among different studies, and a consensus must be reached regarding the clinical application of the saline bolus EIT method. Further study is required to validate the impact of the described saline bolus EIT method on decision-making, therapeutic management, and outcomes in critically ill patients.

COVID-19 pneumonia: microvascular disease revealed on pulmonary dual-energy computed tomography angiography.

Increased prevalence of acute pulmonary embolism in COVID-19 has been reported in few recent studies. Some works have highlighted pathological changes on lung microvasculature with local pulmonary intravascular coagulopathy that may explain pulmonary artery thrombosis found on pulmonary computed tomography (CT) angiography. The objective of our study was to describe lung perfusion disorders assessed by pulmonary dual-energy CT (DECT) angiography in severe COVID-19 patients. This single center retrospective study included 85 consecutive patients with a reverse transcriptase-polymerase chain reaction diagnosis of SARS-CoV-2 who underwent a pulmonary DECT angiography between March 16th 2020 and April 22th 2020. Pulmonary DECT angiography was performed when the patient had severe clinical symptoms or suffered from active neoplasia or immunosuppression. Two chest radiologists performed pulmonary angiography analysis in search of pulmonary artery thrombosis and a blinded semi quantitative analysis of iodine color maps focusing on the presence of parenchymal ischemia. The lung parenchyma was divided into volumes based on HU values. DECT analysis included lung segmentation, total lungs volume and distribution of lung perfusion assessment. Twenty-nine patients (34%) were diagnosed with pulmonary artery thrombosis, mainly segmental (83%). Semi-quantitative analysis revealed parenchymal ischemia in 68% patients of the overall population, with no significant difference regarding absence or presence of pulmonary artery thrombosis (23 vs. 35, P=0.144). Inter-reader agreement of parenchymal ischemia between reader 1 and 2 was substantial [0.74; interquartile range (IQR): 0.59-0.89]. Volume of ischemia was significantly higher in patients with pulmonary artery thrombosis [29 (IQR, 8-100) vs. 8 (IQR, 0-45) cm3, P=0.041]. Lung parenchyma was divided between normal parenchyma (59%, of which 34% was hypoperfused), ground glass opacities (10%, of which 20% was hypoperfused) and consolidation (31%, of which 10% was hypoperfused). Pulmonary perfusion evaluated by iodine concentration maps shows extreme heterogeneity in COVID-19 patients and lower iodine levels in normal parenchyma. Pulmonary ischemic areas were more frequent and larger in patients with pulmonary artery thrombosis. Pulmonary DECT angiography revealed a significant number of pulmonary ischemic areas even in the absence of visible pulmonary arterial thrombosis. This may reflect microthrombosis associated with COVID-19 pneumonia.

Initial lung transplantation experience with uncontrolled donation after cardiac death in North America.

Uncontrolled donation after cardiac death (uDCD) has the potential to ameliorate the shortage of suitable lungs for transplant. To date, no lung transplant data from these donors are available from North America. We describe the successful use of these donors using a simple method of in situ lung inflation so that the organ can be protected from warm ischemic injury. Forty-four potential donors were approached, and family consent was obtained in 30 cases (68%). Of these, the lung transplant team evaluated 16 uDCDs on site, and 14 were considered for transplant pending ex vivo lung perfusion assessment. Five lungs were ultimately used for transplant (16.7% use rate from consented donors). The mean warm ischemic time was 2.8hours. No primary graft dysfunction grade 3 was observed at 24, 48, or 72hours after transplant. Median intensive care unit stay was 5days (range: 2-78days), and median hospital stay was 17days (range: 8-100days). The 30-day mortality was 0%. Four of 5 patients are alive at a median of 651days (range: 121-1254days) with preserved lung function. This study demonstrates the proof of concept and the potential for uDCD lung donation using a simple donor intervention.

Dynamic contrast-enhanced MRI Perfusion of the Lung – Feasibility and Accuracy in Patients with COPD, lung cancer and pulmonary embolism

Introduction: Dynamic contrast enhanced MRI (DCE-MRI) of the lung used to have its limits concerning spatial and temporal resolution and required breath-hold during the examination. However, new techniques allow for an acquisition of 4D datasets of the lung with higher temporal resolution during free breathing. Purpose of this study is the evaluation of accuracy and feasibility of MRI for the robust assessment of lung perfusion in daily routine in comparison with perfusion scintigraphy serving as standard of reference. Methods: This is a retrospective study including all patients who underwent scintigraphy and DCE-MRI at our institute between 06/2012 and 06/2014 for different clinical indications. A T1-weighted gradient echo sequence with echo sharing (TWIST) on a 1.5 T Magnetom Area scanner (Siemens Healthcare, Erlangen, Germany) was used to acquire 4D datasets of the whole lung with temporal resolution of 1.5 seconds and 20 series in total, during free breathing. This data was evaluated using the dedicated “Pulmo MR” software (Fraunhofer-MEVIS, Bremen, Germany) which included particular algorithms for motion correction and to suppress larger vessels (VS) within the lung to obtain several quantitative perfusion read-outs such as blood flow (PBF) and blood volume (PBV) for the pulmonary parenchyma. These datasets were compared with corresponding regions on scintgraphic results using scatter plots, Blant-Altman-plots and Spearman's rank correlation. Results: Currently we have evaluated datasets of 20 patients. The findings demonstrate a high agreement of perfusion parameters found at MRI using VS in comparison to scintigraphy especially in the basal parts of the lungs. In the apical parts MRI perfusion seems to constantly reveal lower perfusion ratios than scintigraphy. Discussion: MR-based 4D lung perfusion is robustly feasible and provides quantitative functional parameters allowing for a substantiated advanced assessment of pulmonary perfusion in comparison with scintigraphy in the major clinical settings COPD, lung cancer and pulmonary embolism.

Chronic Thromboembolic Pulmonary Hypertension (CTEPH) – Potential Role of Multidetector-Row CT (MD-CT) and MR Imaging in the Diagnosis and Differential Diagnosis of the Disease

Chronic thromboembolic pulmonary hypertension (CTEPH) can be defined as pulmonary hypertension (resting mean pulmonary arterial pressure of 25 mm Hg or more determined at right heart catheterization) with persistent pulmonary perfusion defects. It is a rare, but underdiagnosed disease with estimated incidences ranging from 0.5% to 3.8% of patients after an acute pulmonary embolism (PE), and in up to 10% of those with a history of recurrent PE. CTEPH is the only form of pulmonary hypertension that can be surgically treated leading to normalization of pulmonary hemodynamics and exercise capacity in the vast majority of patients. The challenges for imaging in patients with suspected CTEPH are fourfold: the imaging modality should have a high diagnostic accuracy with regard to the presence of CTEPH and allow for differential diagnosis. It should enable detection of patients suitable for PEA with great certainty, and allow for quantification of PH by measuring pulmonary hemodynamics (mPAP and PVR), and finally, it can be used for therapy monitoring. This overview tries to elucidate the potential role of ECG-gated multidetector CT pulmonary angiography (MD-CTPA) and MR imaging, and summarizes the most important results that have been achieved so far. Generally speaking, ECG-gated MD-CTPA is superior to MR in the assessment of parenchymal and vascular pathologies of the lung, and allows for the assessment of cardiac structures. The implementation of iodine maps as a surrogate for lung perfusion enables functional assessment of lung perfusion by CT. MR imaging is the reference standard for the assessment of right heart function and lung perfusion, the latter delineating typical wedge-shaped perfusion defects in patients with CTEPH. New developments show that with MR techniques, an estimation of hemodynamic parameters like mean pulmonary arterial pressure and pulmonary vascular resistance will be possible. CT and MR imaging should be considered as complementary investigations providing comprehensive information in patients with CTEPH.

(695) - The Importance of Airway and Vascular Parameters in Cellular Ex Vivo Lung Perfusion Assessment of the Donor Lung

(695) - The Importance of Airway and Vascular Parameters in Cellular Ex Vivo Lung Perfusion Assessment of the Donor Lung

Noninvasive Imaging of Pulmonary Hypertension

Pulmonary hypertension is defined as a resting mean pulmonary arterial pressure of 25 mm Hg or more determined at right heart catheterization. The challenges for imaging in patients with suspected PH are fivefold: the imaging modality should have a high diagnostic accuracy with regard to the presence of PH; it should be able to characterize the underlying disease, and allow for quantification of its extent by measuring pulmonary hemodynamics. Finally, it should provide prognostic information, and can be used for monitoring of therapy. There have been tremendous improvements in assessment of PH by computed tomography (CT) and magnetic resonance (MR) technology in recent years. This overview tries to elucidate the potential role of each imaging modality and summarizes the most important results that have been achieved so far. In general, after implementation of multidetector technology, CT is superior to MR in assessment of parenchymal and vascular pathologies of the lung, and with electrocardiogram-triggered data acquisition allows for assessment of cardiac structures. The implementation of iodine maps as surrogate for lung perfusion will enable functional assessment of lung perfusion by CT. MR imaging is the reference standard for assessment of cardiac structure and function and allows for physiologic assessment of the pulmonary vasculature. New developments show that with MR techniques, an estimation of hemodynamic parameters such as mean pulmonary arterial pressure and pulmonary vascular resistance will be possible. Actually, CT and MR imaging should be considered as complementary investigations providing comprehensive information in patients with pulmonary hypertension.

Non-contrast-enhanced preoperative assessment of lung perfusion in patients with non-small-cell lung cancer using Fourier decomposition magnetic resonance imaging

ObjectiveTo investigate non-contrast-enhanced Fourier decomposition MRI (FD MRI) for assessment of regional lung perfusion in patients with Non-Small-Cell Lung Cancer (NSCLC) in comparison to dynamic contrast-enhanced MRI (DCE MRI). MethodsTime-resolved non-contrast-enhanced images of the lungs were acquired prospectively in 15 patients using a 2D balanced steady-state free precession (b-SSFP) sequence. After non-rigid registration of the native image data, perfusion-weighted images were calculated by separating periodic changes of lung proton density at the cardiac frequency using FD. DCE MRI subtraction datasets were acquired as standard of reference. Both datasets were analyzed visually for perfusion defects. Then segmentation analyses were performed to describe perfusion of pulmonary lobes semi-quantitatively as percentages of total lung perfusion. Overall FD MRI perfusion signal was compared to velocity-encoded flow measurements in the pulmonary trunk as an additional fully quantitative reference. ResultsImage quality ratings of FD MRI were significantly inferior to those of DCE MRI (P<0.0001). Sensitivity, specificity, and accuracy of FD MRI for visual detection of perfusion defects were 84%, 92%, and 91%. Semi-quantitative evaluation of lobar perfusion provided high agreement between FD MRI and DCE MRI for both entire lungs and upper lobes, but less agreement in the lower parts of both lungs. FD perfusion signal showed high linear correlation with pulmonary arterial blood flow. ConclusionFD MRI is a promising technique that allows for assessing regional lung perfusion in NSCLC patients without contrast media or ionizing radiation. However, for being applied in clinical routine, image quality and robustness of the technique need to be further improved.

Regional lung perfusion estimated by electrical impedance tomography in a piglet model of lung collapse

The assessment of the regional match between alveolar ventilation and perfusion in critically ill patients requires simultaneous measurements of both parameters. Ideally, assessment of lung perfusion should be performed in real-time with an imaging technology that provides, through fast acquisition of sequential images, information about the regional dynamics or regional kinetics of an appropriate tracer. We present a novel electrical impedance tomography (EIT)-based method that quantitatively estimates regional lung perfusion based on first-pass kinetics of a bolus of hypertonic saline contrast. Pulmonary blood flow was measured in six piglets during control and unilateral or bilateral lung collapse conditions. The first-pass kinetics method showed good agreement with the estimates obtained by single-photon-emission computerized tomography (SPECT). The mean difference (SPECT minus EIT) between fractional blood flow to lung areas suffering atelectasis was -0.6%, with a SD of 2.9%. This method outperformed the estimates of lung perfusion based on impedance pulsatility. In conclusion, we describe a novel method based on EIT for estimating regional lung perfusion at the bedside. In both healthy and injured lung conditions, the distribution of pulmonary blood flow as assessed by EIT agreed well with the one obtained by SPECT. The method proposed in this study has the potential to contribute to a better understanding of the behavior of regional perfusion under different lung and therapeutic conditions.