Motion Reduction for C-Arm Computed Tomography of the Pulmonary Arteries: Image Quality of a Motion Correction Algorithm in Patients with Chronic Thromboembolic Hypertension During Balloon Pulmonary Angioplasty.

PURPOSE: To evaluate the feasibility and image quality of a motion correction algorithm for supra-selective C-arm computed tomography (CACT) of the pulmonary arteries in patients with chronic thromboembolic pulmonary hypertension (CTEPH) undergoing balloon pulmonary angioplasty (BPA). MATERIALS & METHODS: CACT raw data acquired during 30 consecutive BPAs were used for image reconstruction using either standard (CACTorg) or a motion correction algorithm (CACTmc), using 400 iterations. Two readers independently evaluated 188 segmental and 564 sub-segmental contrast-enhanced pulmonary arteries in each reconstruction. The following categories were assessed: Sharpness of the vessel, motion artifacts, delineation of bronchial structures, vessel geometry, and visibility of treatable lesions. The mentioned criteria were rated from grade 1 to grade 3: grade 1: excellent quality; grade 2: good quality; grade 3: poor/seriously impaired quality. Inter-observer agreement was calculated using Cohen's Kappa. Due to an excellent agreement, the ratings of both readers were merged. Differences in the assessed image quality criteria were evaluated using pairwise Wilcoxon signed-rank test. RESULTS: Inter-observer agreement was excellent for all evaluated image quality criteria (κ > 0.81). For all assessed image quality criteria, the ratings on CACTorg were good but improved significantly for CACTmc to excellent for the whole vascular tree (p < 0.01). When considering segmental and sub-segmental levels individually, all image quality criteria improved significantly for CACTmc on both levels (p < 0.01). While ratings of CACTmc were constant for both levels (segmental and sub-segmental) for all criteria, the ratings of CACTorg were slightly impaired for the sub-segmental arteries. CONCLUSION: Motion correction for supra-selective contrast-enhanced CACT of the pulmonary arteries is feasible and improves the overall image quality. KEY POINTS: · Motion artifacts can severely impair the diagnostic accuracy of CACT.. · A motion correction algorithm can significantly improve image quality in CACT of the pulmonary arteries.. · Especially the overall image quality of sub-segmental branches is significantly improved.. CITATION FORMAT: · Maschke S, Werncke T, Becker LS et al. Motion Reduction for C-Arm Computed Tomography of the Pulmonary Arteries: Image Quality of a Motion Correction Algorithm in Patients with Chronic Thromboembolic Hypertension During Balloon Pulmonary Angioplasty. Fortschr Röntgenstr 2021; 193: 1074 - 1080.

Impact of Patient Alignment on Image Quality in C-Arm Computed Tomography - Evaluation Using an ACR Phantom.

PURPOSE: To evaluate the influence of patient alignment and thereby heel effect on the image quality (IQ) of C-arm flat-panel detector computed tomography (CACT). MATERIALS AND METHODS: An ACR phantom placed in opposite directions along the z-axis (setup A and B) on the patient support was imaged using CACT. Image acquisition was performed with three different image acquisition protocols. The images were reconstructed with four convolution kernels. IQ was assessed in terms of high contrast using the modulation transfer function (MTF) and low contrast by assessing the image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) as well as the reliability of density measurements. Furthermore, the dose intensity profiles were measured free-in-air. RESULTS: The MTF in setup B is higher than the MTF measured in setup A (p < 0.01). The image noises measured in setup A for the air and bone inserts were higher compared to those measured in setup B (p > 0.05). Opposite behavior has been observed for the polyethylene, water-equivalent and acrylic inserts. The SNR for all inserts is inversely related to the image noise. A systematically increasing or decreasing trend of CNR could not be observed (p > 0.05). The intensity profile measured by the detector system free-in-air showed that the anode heel effect is perpendicular to the z-axis. CONCLUSION: The patient alignment has a minor influence on the IQ of CACT. This effect is not based on the X-ray anode heel effect but is caused mainly by the non-symmetrical rotation of CACT. KEY POINTS: · The impact of patient alignment and thereby the heel effect on the image quality of CACT was analyzed.. · The patient alignment has a minor influence on the physical parameters related to image quality, such as noise, SNR, and MTF.. · This effect is based mainly on the non-symmetrical rotation of CACT.. CITATION FORMAT: · Alikhani B, Renne J, Maschke S et al. Impact of Patient Alignment on Image Quality in C-Arm Computed Tomography - Evaluation Using an ACR Phantom. Fortschr Röntgenstr 2021; 193: 417 - 426.

Perioperative CTEPH patient monitoring with 2D phase-contrast MRI reflects clinical, cardiac and pulmonary perfusion changes after pulmonary endarterectomy.

Magnetic resonance imaging (MRI) is an emerging tool for diagnosis and treatment monitoring of chronic thromboembolic pulmonary hypertension (CTEPH). The current study aims to identify central pulmonary arterial hemodynamic parameters that reflect clinical, cardiac and pulmonary changes after PEA. 31 CTEPH patients, who underwent PEA and received pre- and postoperative MRI, were analyzed retrospectively. Central pulmonary arterial blood flow, lung perfusion and right heart function data were derived from MRI. Mean pulmonary arterial pressure (mPAP) and 5-month follow-up six-minute walk-distance (6MWD) were assessed. After PEA, mPAP decreased significantly and patients achieved a higher 6MWD. Central pulmonary arterial blood flow velocities, pulmonary blood flow (PBF) and right ventricular function increased significantly. Two-dimensional (2D) phase-contrast (PC) MRI-derived average mean velocity, maximum mean velocity and deceleration volume changes after PEA correlated with changes of 6MWD and right heart ejection fraction (RVEF). Deceleration volume is a novel 2D PC MRI parameter showing further correlation with PBF changes. In conclusion, 2D PC MRI-derived main pulmonary hemodynamic changes reflect changes of RVEF, PBF and 5-month follow-up 6MWD and may be used for future CTEPH patient monitoring after PEA.

Noninvasive Monitoring of the Response of Human Lungs to Low-Dose Lipopolysaccharide Inhalation Challenge Using MRI: A Feasibility Study.

BACKGROUND: Development of antiinflammatory drugs for lung diseases demands novel methods for noninvasive assessment of inflammatory processes in the lung. PURPOSE: To investigate the feasibility of hyperpolarized 129 Xe MRI, 1 H T1 time mapping, and dynamic contrast-enhanced (DCE) perfusion MRI for monitoring the response of human lungs to low-dose inhaled lipopolysaccharide (LPS) challenge compared to inflammatory cell counts from induced-sputum analysis. STUDY TYPE: Prospective feasibility study. POPULATION: Ten healthy volunteers underwent MRI before and 6 hours after inhaled LPS challenge with subsequent induced-sputum collection. FIELD STRENGTH/SEQUENCES: 1.5T/hyperpolarized 129 Xe MRI: Interleaved multiecho imaging of dissolved and gas phase, ventilation imaging, dissolved-phase spectroscopy, and chemical shift saturation recovery spectroscopy. 1 H MRI: Inversion recovery fast low-angle shot imaging for T1 mapping, time-resolved angiography with stochastic trajectories for DCE MRI. ASSESSMENT: Dissolved-phase ratios of 129 Xe in red blood cells (RBC), tissue/plasma (TP) and gas phase (GP), ventilation defect percentage, septal wall thickness, surface-to-volume ratio, capillary transit time, lineshape parameters in dissolved-phase spectroscopy, 1 H T1 time, blood volume, flow, and mean transit time were determined and compared to cell counts. STATISTICAL TESTS: Wilcoxon signed-rank test, Pearson correlation. RESULTS: The percentage of neutrophils in sputum was markedly increased after LPS inhalation compared to baseline, P = 0.002. The group median RBC-TP ratio was significantly reduced from 0.40 to 0.31, P = 0.004, and 1 H T1 was significantly elevated from 1157.6 msec to 1187.8 msec after LPS challenge, P = 0.027. DCE MRI exhibited no significant changes in blood volume, P = 0.64, flow, P = 0.17, and mean transit time, P = 0.11. DATA CONCLUSION: Hyperpolarized 129 Xe dissolved-phase MRI and 1 H T1 mapping may provide biomarkers for noninvasive assessment of the response of human lungs to LPS inhalation. By its specificity to the alveolar region, hyperpolarized 129 Xe MRI together with 1 H T1 mapping adds value to sputum analysis. LEVEL OF EVIDENCE: 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:1669-1676.

Chemosaturation Percutaneous Hepatic Perfusion (CS-PHP) with Melphalan: Evaluation of 2D-Perfusion Angiography (2D-PA) for Leakage Detection of the Venous Double-Balloon Catheter.

PURPOSE: To evaluate the feasibility of 2D-perfusion angiography (2D-PA) for detecting leakage of the double-balloon catheter used for chemosaturation percutaneous hepatic perfusion (CS-PHP). MATERIALS AND METHODS: Overall, 112 CS-PHP (09/2015-09/2018) in 52 patients were retrospectively screened for leakage alongside the double-balloon catheter on standard venograms. Finally, 18 procedures with visually detected leakage were included. Fifteen consecutive procedures without leakage served as control. To evaluate 2D-PA for leakage detection, the acquired digital subtraction venograms were post-processed. For each balloon, two different target ROIs were evaluated to assess a possible impact of localization and shape of the ROIs. Time to peak (TTP), peak density (PD), area under the curve (AUC), and ratios of target ROI/reference ROIs (PDtROI/PDREF; AUCtROI/AUCREF; and TTPtROI/TTPREF) were calculated. RESULTS: Leakages were located as follows: 15/18 cranial and 3/18 caudal. At the cranial balloon both ROIs showed a significant decrease in PDtROI/PDREF and AUCtROI/AUCREF (ROI1: p < 0.0001; p < 0.0001; ROI2: p < 0.0001; p < 0.0001) and a significant increase in TTPtROI/TTPREF (ROI1: p = 0.0009; ROI2: p = 0.0003) after double-balloon correction. Following balloon adjustment, the 2D-PA ratios (PD and AUC) of the tested ROIs differed significantly (p < 0.05). The inter-individual comparison of the 2D-PA parameters of the group with leakage before balloon correction and the non-leakage group showed significantly different 2D-PA values for the cranial balloon in both ROIs (p < 0.05). No significant differences were found for the caudal balloon. CONCLUSION: 2D-PA provides a feasible tool for detecting leakages alongside the cranial portion of the double-balloon catheter used in CS-PHP. The shape and position of the ROIs used to assess perfusion and flow have an impact on the measurements.

Effect of Indacaterol/Glycopyrronium on Pulmonary Perfusion and Ventilation in Hyperinflated Patients with Chronic Obstructive Pulmonary Disease (CLAIM). A Double-Blind, Randomized, Crossover Trial.

Rationale: In the CLAIM study, dual bronchodilation with indacaterol/glycopyrronium (IND/GLY) significantly reduced hyperinflation, which translated into improved cardiac function, measured by left ventricular end-diastolic volume and cardiac output. Pulmonary microvascular blood flow (PMBF) is reduced in chronic obstructive pulmonary disease (COPD); however, the effect of reduced lung hyperinflation on PMBF remains unknown. Objectives: To determine the effect of lung deflation with IND/GLY on PMBF and regional pulmonary ventilation using magnetic resonance imaging (MRI) in hyperinflated patients with COPD. Methods: In this double-blind, randomized, two-period crossover study, gadolinium-enhanced MRI and phase-resolved functional lung MRI were used to measure PMBF and regional ventilation, respectively, in patients with COPD receiving IND/GLY versus placebo. Measurements and Main Results: Sixty-two patients were randomized to receive once-daily IND/GLY (110/50 µg) for 14 days, followed by 14 days of placebo, or vice versa. Treatment periods were separated by a 14-day washout. Sixty patients were included in the per-protocol analysis. MRI measurements showed significant improvements in total PMBF (P = 0.006) and regional PMBF (P values for individual lobes were between 0.004 and 0.022) in response to IND/GLY versus placebo. Regional ventilation was also significantly improved with IND/GLY, as evidenced by a 12.4% increase versus placebo (P = 0.011), a 14.3% relative decrease in ventilation defect percentage of nonventilated/hypoventilated lung tissue (cutoff was defined as 0.075 regional ventilation; P = 0.0002), and a 15.7% reduction in the coefficient of variation of regional ventilation compared with placebo (P < 0.0001). Conclusions: Pharmacologic intervention with IND/GLY improves pulmonary microvascular blood flow and regional ventilation in patients with COPD with hyperinflation. Clinical trial registered with www.clinicaltrials.gov (NCT02442206).

Functional Pulmonary Magnetic Resonance Imaging for Detection of Ischemic Injury in a Porcine Ex-Vivo Lung Perfusion System Prior to Transplantation.

RATIONALE AND OBJECTIVES: To evaluate the feasibility of multiparametric magnetic resonance imaging (MRI) of the lungs to detect impaired organ function in a porcine model of ischemic injury within an ex-vivo lung perfusion system (EVLP) prior to transplantation. MATERIALS AND METHODS: Twelve pigs were anesthetized, and left lungs were clamped to induce warm ischemia for 3 hours. Right lungs remained perfused as controls. Lungs were removed and installed in an EVLP for 12 hours. Lungs in the EVLP were imaged repeatedly using computed tomography, proton MRI (1H-MRI) and fluorine MRI (19F-MRI). Dynamic contrast-enhanced derived parenchymal blood volume, oxygen washout times, and 19F washout times were calculated. PaO2 was measured for ischemic and normal lungs, wet/dry ratio was determined, histologic samples were assessed, and cytokines in the lung tissue were analyzed. Statistical analysis was performed using nonparametric testing. RESULTS: Eleven pigs were included in the final analysis. Ischemic lungs showed significantly higher wet/dry ratios (p = 0.024), as well as IL-8 tissue levels (p = 0.0098). Histologic assessment as well as morphologic scoring of computed tomography and 1H-MRI did not reveal significant differences between ischemic and control lungs. 19F washout (p = 0.966) and parenchymal blood flow (p = 0.32) were not significantly different. Oxygen washout was significantly prolonged in ischemic lungs compared to normal control lungs at the beginning (p = 0.018) and further prolonged at the end of the EVLP run (p = 0.005). CONCLUSION: Multiparametric pulmonary MRI is feasible in lung allografts within an EVLP system. Oxygen-enhanced imaging seems to be a promising marker for ischemic injury, enabling detection of affected lung segments prior to transplantation.

C-Arm computed tomography (CACT)-guided balloon pulmonary angioplasty (BPA): Evaluation of patient safety and peri- and post-procedural complications.

AIM: To assess the frequency and severity of complications of balloon pulmonary angioplasty (BPA) using C-arm computed tomography (CACT) guidance. MATERIAL AND METHODS: 266 consecutive interventions in 67 patients (42 females, mean age 66 ± 13 years) were included. Selective CACT was acquired prior to the intervention for three-dimensional (3D) guidance and to select appropriate balloon size based on the measured vessel diameter. Complications during and after the procedure, the need for further interventions and the impact on patient safety and outcome were assessed and categorised according to the SIR Classification System to Complications by Outcome (Grade A-F). RESULTS: Overall, 237 interventions were conducted without any complications (89.1%). Minor complications not requiring additional treatment occurred during or after 25 procedures (9.4%), including recurring dry cough in four patients during a total of 11 interventions (4.1%) (Grade A), three focal dissections of the targeted pulmonary artery (1.1%), four cases of pulmonary haemorrhage (1.5%), one case of reperfusion oedema (0.4%) and six cases of post-interventional short-term hemoptysis (2.3%) (Grade B). Four cases of major complications requiring additional treatment were observed (1.5%): one case of pulmonary haemorrhage (0.4%) and two cases of post-interventional haemoptysis (0.8%), all resolved after medical therapy without requiring further intervention, and one case of atrial tachycardia induced during catheterisation, subsequently requiring pharmacological cardioversion (0.4%) (Grade C). No fatal or life-threatening peri- or post-interventional complications or mortality were observed (Grade D-F). CONCLUSION: BPA performed under CACT guidance appears to be a safe procedure with a low risk of severe complications. KEY POINTS: • CACT guidance of BPA is safe and successful. • CACT-guided BPA procedures have a low complication profile. • CACT guidance is a valuable tool to navigate BPA.

Cardio-pulmonary MRI for detection of treatment response after a single BPA treatment session in CTEPH patients.

OBJECTIVES: Chronic thromboembolic pulmonary hypertension (CTEPH) can be treated with balloon pulmonary angioplasty (BPA) in inoperable patients. Sensitive non-invasive imaging methods are missing to detect treatment response after a single BPA treatment session. Therefore, the aim of this study was to measure treatment response after a single BPA session using cardio-pulmonary MRI. MATERIALS AND METHODS: Overall, 29 patients with CTEPH were examined with cardio-pulmonary MRI before and 62 days after their initial BPA session. Pulmonary blood flow (PBF), first-pass bolus kinetic parameters, and biventricular mass and function were determined. Multiple linear regression analysis was implemented to estimate the relationship of PBF change in the treated lobe with treatment change of full width at half maximum (FWHM), cardiac output (CO), ventricular mass index (VMI), pulmonary transit time (PTT) and PBF change in the non-treated lobes. Paired Wilcoxon rank sum test and Spearman rho correlation were used. RESULTS: After BPA regional PBF increased in the treated lobe (p < 0.0001) as well as in non-treated lobes (p = 0.015). PBF treatment changes in the treated lobe were significantly larger compared with the non-treated lobes (p = 0.0049). Change in NT proBNP, MRI-derived mean pulmonary artery pressure (mPAP), PTT, FWHM, right ventricular (RV) ejection fraction, RV stroke volume, CO, VMI and PBF in the non-treated lobes correlated with PBF change in the treated lobe (p < 0.05). PBF changes in the treated lobe were independently predicted by PTT as well as PBF change in the non-treated lobes. CONCLUSION: Cardio-pulmonary MRI detects and quantifies treatment response after a single BPA treatment session. KEY POINTS: • Two months after BPA regional parenchymal pulmonary perfusion (PBF) increased in the total lung parenchyma (p = 0.005), the treated lobes (p < 0.0001) and non-treated lobes (p = 0.015). • The PBF treatment changes in the treated lobe were significantly larger than in the non-treated lobes (p = 0.0049). • Change in NT proBNP, MRI-derived mean pulmonary artery pressure, pulmonary transit time, full width at half maximum, right ventricular (RV) ejection fraction, RV stroke volume, cardiac output, ventricular mass index and PBF in the non-treated lobes correlated with PBF change in the treated lobe (p < 0.05).

Multiparametric MRI for organ quality assessment in a porcine Ex-Vivo lung perfusion system.

INTRODUCTION: Ex-vivo lung perfusion (EVLP) is an emerging technique promising an expansion of the donor pool and improvements in the outcome after lung transplantation. Reliable biomarkers for local assessment of organ function in the EVLP system are intensely sought after. This study aims to evaluate the feasibility of multiparametric functional magnetic resonance imaging (fMRI) in an EVLP system in a porcine aspiration model. MATERIAL AND METHODS: Seven female pigs were anesthetized and gastric juice was instilled in the right lower lobe bronchus to simulate aspiration. Left lungs served as control. Lungs were removed and installed in a modified EVLP system. In the 12-hour EVLP run three sequential MRI scans were performed. Oxygen-washout time, Fourier Decomposition derived ventilation and perfusion, and dynamic contrast enhanced imaging derived perfusion were calculated. PaO2:FiO2 ratio was determined and correlated. End-point histology and computed tomography served as control. RESULTS: All animals completed the protocol. MRI structural images showed infiltrates in lungs after aspiration comparable to CT scans. Ventilation was significantly (p = 0.016) reduced while perfusion was increased (p = 0.016) in lungs after aspiration. Non-contrast dependent Fourier decomposition perfusion showed good correlation (R2 = 0.67) to dynamic contrast enhanced derived perfusion. Oxygen washout time was significantly increased (p = 0.016) in lungs after aspiration and showed a correlation with the PaO2:FiO2 ratio (R2 = 0.54). CONCLUSION: Multiparametric fMRI for local assessment of organ function is feasible in EVLP and detects alterations in lung function following aspiration with correlation to clinical parameters. fMRI may improve organ assessment in ex-vivo perfusion systems, leading to a better selection of segments suitable for transplant.

Transjugular intrahepatic portosystemic shunt (TIPS) dysfunction: quantitative assessment of flow and perfusion changes using 2D-perfusion angiography following shunt revision.

PURPOSE: To analyze the feasibility of 2D-perfusion angiography (2D-PA) to quantify flow and perfusion changes pre- and post-transjugular intrahepatic portosystemic shunt (TIPS) revision. MATERIALS AND METHODS: Fifteen consecutive patients (54 ± 14 years, seven men and eight women) scheduled for TIPS revision were included in this study. To quantify flow and perfusion changes caused by TIPS revision, digital subtraction angiography (DSA) series acquired during the revision were post-processed using a dedicated software. Reference region-of-interest (ROI) in the main portal vein (input function) and target ROIs in the TIPS lumen, the liver parenchyma and in the right atrium were placed in corresponding areas on DSA pre- and post-TIPS revision. 2D-PA evaluation included time to peak (TTP), peak density (PD), and the area under the curve (AUC) assessment. The ratios of reference ROI to target ROIs pre- and post-TIPS revision were calculated (TTPparenchyma/TTPinflow, PDparenchyma/PDinflow, AUCparenchyma/AUCinflow, TTPTIPS/TTPinflow, PDTIPS/PDinflow, AUCTIPS/AUCinflow, TTPatrium/TTPinflow, PDatrium/PDinflow, and AUCatrium/AUCinflow). Pressure measurements pre- and post-TIPS revision were performed and correlated to the 2D-PA parameters. Reproducibility of 2D-PA was assessed by the intra-class correlation coefficient (ICC). RESULTS: The portosystemic pressure gradient was significantly reduced following TIPS revision (17.1 ± 6.3 vs. 8.9 ± 4.3 mmHg; p < 0.0001). PDTIPS/PDinflow (0.22 vs. 0.35; p = 0.0014) and AUCTIPS/AUCinflow (0.24 vs. 0.39; p = 0.0012) increased significantly. Likewise, PDatrium/PDinflow (0.32 vs. 0.78; p = 0.0004) and AUCatrium/AUCinflow (0.3 vs. 0.79; p < 0.0001) increased, whereas PDparenchyma/PDinflow decreased significantly (0.14 vs. 0.1; p = 0.0084). Pressure gradient changes correlated significantly with the increase in PDatrium/PDinflow (r = - 0.77, p = 0.0012) and AUCatrium/AUCinflow (r = - 0.76, p = 0.0018). ICC of the 2D-PA parameters was in the range of 0.88-0.99. CONCLUSION: 2D-PA offers a feasible approach to quantify flow and perfusion changes during TIPS revision. Therefore, 2D-PA may be a valuable amendment to mere pressure measurements.

Quantification of perfusion reduction by using 2D-perfusion angiography following transarterial chemoembolization with drug-eluting beads.

PURPOSE: To analyze the feasibility of 2D-perfusion angiography (2D-PA) for the quantification of perfusion reduction following transarterial chemoembolization with drug-eluting beads (DEB-TACE). METHODS: Overall, 24 DEB-TACE procedures in 19 patients were included. To quantify changes in tumor perfusion following DEB-TACE using 2D-PA, the acquired digital subtraction angiography (DSA) series were post-processed. A reference region-of-interest (ROI) in a main hepatic artery and two, distal target ROIs in embolized tumor tissue and in non-target liver parenchyma were placed in corresponding areas on DSA pre- and post-DEB-TACE. The time to peak (TTP), peak density (PD), and the area under the curve (AUC) were assessed and the ratios reference ROI/target ROIs were calculated. RESULTS: In the embolized tumor, the 2D-PA ratios changed significantly (p < 0.05) after DEB-TACE, whereas no significant change was observed for non-target liver parenchyma (p > 0.05). PDtumor/PDinflow differed significantly to PDparenchyma/PDinflow pre-DEB-TACE (p < 0.0001), likewise AUCtumor/AUCinflow to AUCparenchyma/AUCinflow (p < 0.0001) with higher values in tumor tissue. The post-DEB-TACE ratios of AUC decreased significantly in the tumor tissue compared to the non-target liver parenchyma (p < 0.05). CONCLUSION: 2D-PA offers an objective approach to quantify the immediate perfusion reduction of embolized tumor tissue following DEB-TACE and may therefore be used to monitor peri-interventional stasis and to quantify technical success.

Functional lung MRI for regional monitoring of patients with cystic fibrosis.

PURPOSE: To test quantitative functional lung MRI techniques in young adults with cystic fibrosis (CF) compared to healthy volunteers and to monitor immediate treatment effects of a single inhalation of hypertonic saline in comparison to clinical routine pulmonary function tests. MATERIALS AND METHODS: Sixteen clinically stable CF patients and 12 healthy volunteers prospectively underwent two functional lung MRI scans and pulmonary function tests before and 2h after a single treatment of inhaled hypertonic saline or without any treatment. MRI-derived oxygen enhanced T1 relaxation measurements, fractional ventilation, first-pass perfusion parameters and a morpho-functional CF-MRI score were acquired. RESULTS: Compared to healthy controls functional lung MRI detected and quantified significantly increased ventilation heterogeneity in CF patients. Regional functional lung MRI measures of ventilation and perfusion as well as the CF-MRI score and pulmonary function tests could not detect a significant treatment effect two hours after a single treatment with hypertonic saline in young adults with CF (p>0.05). CONCLUSION: This study shows the feasibility of functional lung MRI as a non-invasive, radiation-free tool for monitoring patients with CF.

Chronic thromboembolic pulmonary hypertension: Evaluation of 2D-perfusion angiography in patients who undergo balloon pulmonary angioplasty.

OBJECTIVE: To evaluate the feasibility of 2D-perfusion angiography (2D-PA) in order to quantify perfusion changes of the lung parenchyma pre- and post-balloon pulmonary angioplasty (BPA). METHODS: Thirty consecutive interventions in 16 patients with 99 treated pulmonary artery segments were included. To quantify changes in pulmonary blood flow using 2D-PA, the acquired digital subtraction angiographies (DSA) pre- and post-BPA were post-processed. A reference ROI in the treated pulmonary artery and a distal target ROI in the lung parenchyma were placed in corresponding areas on DSA pre- and post-BPA. Time to peak (TTP), peak density (PD) and area under the curve (AUC) were assessed. The ratios reference ROI to target ROI (TTPparenchyma/TTPinflow; PDparenchyma/PDinflow; AUCparenchyma/AUCinflow) were calculated. Relative differences of the 2D-PA parameters were correlated to changes in the pulmonary-flow-grade-score. RESULTS: The pulmonary-flow-grade-score improved after BPA (p<0.0001). Likewise, the ratio TTPparenchyma/TTPinflow shortened by 10% (p=0.0002), the PDparenchyma/PDinflow increased by 46% (p<0.0001) and the AUCparenchyma/AUCinflow increased by 36% (p<0.0001). A significant correlation between changes in the pulmonary-flow-grade-score and changes in PDparenchyma/PDinflow (ρ=0.48, p<0.0001) and AUCparenchyma/AUCinflow (ρ=0.31, p=0.0018) was observed. CONCLUSION: Quantification of pulmonary perfusion pre- and post-BPA using 2D-PA is feasible and has the potential to improve monitoring of BPA. KEY POINTS: • Quantification of BPA results by use of 2D-PA is feasible. • 2D-PA allows objective assessment of changes in lung parenchymal perfusion. • 2D-PA has the potential to optimize BPA.

Balloon pulmonary angioplasty: applicability of C-Arm CT for procedure guidance.

PURPOSE: To investigate the feasibility of and compare two C-Arm CT (CACT) guidance methods during balloon pulmonary angioplasty (BPA). MATERIAL AND METHODS: Forty-two BPAs [27 CTEPH patients (nine males, 70 ± 14y)] targeting 143 pulmonary arteries were included. Twenty-two BPAs were guided by contrast-enhanced CACT acquired immediately before BPA (G3D). In another 20 BPAs (G2D), two orthogonal fluoroscopy images of the chest where acquired to compute a registration of a previously acquired CACT. Volume rendering-based graphic representations (VRT guidance) were generated indicating the origin and course of the vessels. Based on VRT guidance, the intervention was planned. Procedure durations and radiation exposure data were compared between the two groups (Wilcoxon test). RESULTS: The overall intervention time was approximately 2 h in both groups (p = 0.31). BPA was successfully performed in G3D 91 % and G2D 94 %. No significant difference was found concerning the mean dose area product (DAP) related to fluoroscopy (p = 0.38), while DAP related to DSA was slightly higher in G3D (p = 0.048). Overall, DAP was significantly higher in G3D (p = 0.002). CONCLUSIONS: The use of CACT for procedure guidance in patients undergoing BPA is feasible and accurate. Image fusion of a pre-acquired CACT can be used to decrease radiation exposure due to multiple BPA sessions. KEY POINTS: • BPA guidance by CACT overlay is feasible and safe. • 2D3D image fusion for BPA guidance is accurate. • Image fusion can reduce patient radiation dose due to repeated BPA sessions.

MR Imaging-derived Regional Pulmonary Parenchymal Perfusion and Cardiac Function for Monitoring Patients with Chronic Thromboembolic Pulmonary Hypertension before and after Pulmonary Endarterectomy.

Purpose To evaluate surgical success after pulmonary endarterectomy (PEA) by means of cardiopulmonary magnetic resonance (MR) imaging. Materials and Methods In this institutional review board-approved study, 20 patients with chronic thromboembolic pulmonary hypertension were examined at 1.5 T with a dynamic contrast material-enhanced three-dimensional fast low-angle shot sequence before and 12 days after PEA (25th-75th percentile range, 11-16 days). Lung segments were evaluated visually before PEA for parenchymal hypoperfused segments. Pulmonary blood flow (PBF), first-pass bolus kinetic parameters, and biventricular mass and function were determined. Mean pulmonary artery pressure (mPAP) and 6-minute walking distance were measured before and after PEA. The Shapiro-Wilk test, paired two-sided Wilcoxon rank sum test, Spearman ρ correlation, and multiple linear regression analysis were performed. Results Two weeks after PEA, regional PBF increased 66% in the total lung from 32.7 to 54.2 mL/min/100 mL (P = .0002). However, after adjustment for cardiac output, this change was not evident anymore (increase of 7% from 7.03 to 7.54 mL/min/100 mL/L/min, P = .1). Only in the lower lobes, a significant increase in PBF after cardiac output adjustment remained: a 16% increase in the right lower lobe from 7.53 to 8.71 mL/min/100 mL (P = .01) and a 14% increase in the left lower lobe from 7.42 to 8.47 mL/min/100 mL/L/min (P < .05). Right ventricular mass and function also improved. mPAP decreased from 46 to 24 mm Hg (P < .0001). Six-minute walking distance increased from 390 to 467 m (P = .02) 5 months after PEA. Percentage change of mPAP and PBF in the lower lobe tended to be significant predictors of percentage change in 6-minute walking distance (ß = -1.79 [P = .054] and ß = 0.45 [P = .076], respectively) in multiple linear regression analysis. Conclusion Improvement of PBF after PEA was observed predominantly in the lower lungs, and the magnitude of improvement of PBF in the lower lobes correlated with the improvement in exercise capacity, reflecting surgical success. (©) RSNA, 2016.

Pulmonary Artery Imaging in Patients with Chronic Thromboembolic Pulmonary Hypertension: Comparison of Cone-Beam CT and 64-Row Multidetector CT.

PURPOSE: To compare the depiction of pulmonary arteries in pulmonary arterial catheter-based contrast-enhanced cone-beam CT with peripheral intravenous contrast-enhanced multidetector CT in patients with suspected chronic thromboembolic pulmonary hypertension. MATERIAL AND METHODS: In 20 patients (15 men and 5 women, 63.4 y ± 16.3), cone-beam CT using a catheter placed in the main pulmonary artery and 64-row multidetector CT using an appropriate venous access were performed. Contrast enhancement was measured in the main pulmonary artery, the right and left pulmonary arteries, and the left atrium. The amount of peripheral vessel conspicuity adjacent to the pleural surface (distance from vessel-to pleura) was measured. Two readers (R1, R2) independently evaluated the pulmonary arteries for image quality and pathologic findings in both modalities. RESULTS: Contrast density was higher in the main pulmonary artery and right and left pulmonary arteries (P < .002) and lower in the left atrium (P = .001) on cone-beam CT. The smallest distance between clearly delineated vessels and the pleura was significantly lower on cone-beam CT images (P < .0001). Interobserver agreement was good for cone-beam CT (κ = 0.79) and multidetector CT (κ = 0.78), whereas intermodality agreement was moderate (R1, κ = 0.60; R2, κ = 0.59). Both readers detected more weblike stenoses with cone-beam CT (76; 22%) compared with multidetector CT (25; 7%). CONCLUSIONS: Cone-beam CT shows improved contrast between pulmonary arteries and the left atrium and allows a more detailed depiction of the pulmonary arteries.

Chronic Lung Allograft Dysfunction: Oxygen-enhanced T1-Mapping MR Imaging of the Lung.

PURPOSE: To evaluate oxygen-enhanced T1-mapping magnetic resonance (MR) imaging of the lungs for detection of chronic lung allograft dysfunction (CLAD) in patients who have undergone double lung transplantation. MATERIALS AND METHODS: The local ethics committee approved this study. Seventy-six recipients of double lung allografts who underwent MR imaging of the lungs during an outpatient visit between 2011 and 2013 were included in this study after they provided written informed consent. Patients were classified as having CLAD on the basis of spirometric results and were divided into three groups: no CLAD (bronchiolitis obliterans syndrome level 0 [BOS 0]), early CLAD (BOS 0p), and late-stage CLAD (BOS 1-3). Coronal T1 maps of the lungs were acquired with the patient breathing room air and 100% oxygen by using an inversion-recovery snapshot fast low-angle shot sequence at 1.5 T. The median and interquartile range of T1 values at room air and at 100% oxygen and the oxygen transfer function were calculated. Statistical analysis was performed with analysis of variance and the Tukey honestly significant difference test or the Kruskal-Wallis test and the Mann-Whitney U test (α = 0.05). Bonferroni correction was applied for multiple comparisons. RESULTS: The oxygen transfer function was significantly lower in patients in the BOS 0p (P = .025) and BOS 1-3 groups (P = .003) than it was in the patients with BOS 0. Absolute T1 values (room air, P = .66; 100% oxygen, P = .67) did not differ significantly among the groups. The heterogeneity of T1 values, measured by using the interquartile range, showed a strong trend toward higher values in patients with BOS (room air, P = .06; 100% oxygen, P = .08). CONCLUSION: Oxygen transfer function may serve as an early marker for detection of CLAD.

Prevalence and configuration of pulmonary nodules on multi-row CT in children without malignant diseases.

OBJECTIVES: To assess the prevalence and morphologic characterization of pulmonary nodules in children on a chest computed tomography (CT). METHODS: Two hundred and fifty-nine trauma chest CTs in children aged 0-18 years were retrospectively reviewed by two radiologists, each with more than 10 years of experience. Images were acquired on a 64-row CT. Pulmonary lobes with trauma affections such as contusion or haemorrhage were excluded. All pulmonary nodules were evaluated for distance from the pleural surface, location, calcification and size on axial slices. RESULTS: A total of 1,190/1,295 (92%) pulmonary lobes without traumatic injury were included in this study. In 86 of 259 (33%) patients, 131 pulmonary nodules were detected. Number of nodules per patient ranged from 1 to 4. Calcifications were seen in 19% (25) of all nodules. Diameters ranged from 1 to 5 mm. 59% (77) were located in the lower lobes, 9% (12) in the middle lobe and 32% (42) in the upper lobes. 84% of the non-calcified nodules >2 mm showed a slightly angular or triangular (mostly pleural nodes) shape. CONCLUSIONS: Pulmonary nodules smaller than 5 mm can be detected frequently in children without malignant disease and are predominantly located in the lower lobes. KEY POINTS: • Pulmonary nodules in children with trauma CTs were retrospectively analysed • Pulmonary nodules seen on CT are frequent in children without malignant disease • Nodules in this group are more frequent in the lower lobes • No age dependency for the number of pulmonary nodules in children was observed.

Performance of perfusion-weighted Fourier decomposition MRI for detection of chronic pulmonary emboli.

PURPOSE: To evaluate the test performance of perfusion-weighted Fourier-decomposition (pw-FD) magnetic resonance imaging (MRI) in comparison to dynamic contrast-enhanced (DCE)-MRI as a reference standard in patients with known or suspected chronic pulmonary embolism (PE). MATERIALS AND METHODS: In 64 patients, chronic PE was ruled out or confirmed by DCE-MRI using a time-resolved angiography with stochastic trajectories (TWIST) sequence in one breath-hold. Pw-FD-MRI was performed using a 2D fast low-angle shot (FLASH) sequence in free-breathing. After a nonrigid image registration, FD was applied to generate pw-images. Lungs were scored by two radiologists (2 and 12 years of lung MRI experience) visually for each lobe and segment for hypoperfused areas. For intra- and interobserver variability, the MR images were analyzed 2 months after the first analysis, blinded to the results of the first reader. RESULTS: PE was diagnosed by DCE-MRI in 39 patients. For the pw-FD MRI sensitivity, specificity, accuracy, and positive and negative predictive value for diagnosis of PE were 100%, 95%, 98%, 98%, and 100% on a per-patient basis, 94%, 94%, 94%, 95%, 94% on a per-lobe basis, and 82%, 92%, 88%, 88%, 88% on a segmental basis, respectively. Detection of subsegmental and segmental hypoperfusion using pw-FD MRI showed a moderate agreement with DCE-MRI (kappa of 0.68; 95% confidence interval: 0.64; 0.72). CONCLUSION: Pw-FD of the lung is a feasible test to diagnose chronic PE on a per-patient level during free-breathing without the use of ionizing radiation or contrast agents.