Frank Risse

Effect of inspiratory and expiratory breathhold on pulmonary perfusion: assessment by pulmonary perfusion magnetic resonance imaging.

Rationale and Objectives:The effect of breathholding on pulmonary perfusion remains largely unknown. The aim of this study was to assess the effect of inspiratory and expiratory breathhold on pulmonary perfusion using quantitative pulmonary perfusion magnetic resonance imaging (MRI). Methods and Results:Nine healthy volunteers (median age, 28 years; range, 20–45 years) were examined with contrast-enhanced time-resolved 3-dimensional pulmonary perfusion MRI (FLASH 3D, TR/TE: 1.9/0.8 ms; flip angle: 40°; GRAPPA) during end-inspiratory and expiratory breathholds. The perfusion parameters pulmonary blood flow (PBF), pulmonary blood volume (PBV), and mean transit time (MTT) were calculated using the indicator dilution theory. As a reference method, end-inspiratory and expiratory phase-contrast (PC) MRI of the pulmonary arterial blood flow (PABF) was performed. Results:There was a statistically significant increase of the PBF (Δ = 182 mL/100mL/min), PBV (Δ = 12 mL/100 mL), and PABF (Δ = 0.5 L/min) between inspiratory and expiratory breathhold measurements (P <0.0001). Also, the MTT was significantly shorter (Δ = −0.5 sec) at expiratory breathhold (P = 0.03). Inspiratory PBF and PBV showed a moderate correlation (r = 0.72 and 0.61, P ≤0.008) with inspiratory PABF. Conclusion:Pulmonary perfusion during breathhold depends on the inspiratory level. Higher perfusion is observed at expiratory breathhold.

Assessment of differential pulmonary blood flow using perfusion magnetic resonance imaging: comparison with radionuclide perfusion scintigraphy.

Objectives:We sought to assess the agreement between lung perfusion ratios calculated from pulmonary perfusion magnetic resonance imaging (MRI) and those calculated from radionuclide (RN) perfusion scintigraphy. Materials and Methods:A retrospective analysis of MR and RN perfusion scans was conducted in 23 patients (mean age, 60 ± 14 years) with different lung diseases (lung cancer = 15, chronic obstructive pulmonary disease = 4, cystic fibrosis = 2, and mesothelioma = 2). Pulmonary perfusion was assessed by a time-resolved contrast-enhanced 3D gradient-echo pulse sequence using parallel imaging and view sharing (TR = 1.9 milliseconds; TE = 0.8 milliseconds; parallel imaging acceleration factor = 2; partition thickness = 4 mm; matrix = 256 × 96; in-plane spatial resolution = 1.87 × 3.75 mm; scan time for each 3D dataset = 1.5 seconds), using gadolinium-based contrast agents (injection flow rate = 5 mL/s, dose = 0.1 mmol/kg of body weight). The peak concentration (PC) of the contrast agent bolus, the pulmonary blood flow (PBF), and blood volume (PBV) were computed from the signal-time curves of the lung. Left-to-right ratios of pulmonary perfusion were calculated from the MR parameters and RN counts. The agreement between these ratios was assessed for side prevalence (sign test) and quantitatively (Deming-regression). Results:MR and RN ratios agreed on side prevalence in 21 patients (91%) with PC, in 20 (87%) with PBF, and in 17 (74%) with PBV. The MR estimations of left-to-right perfusion ratios correlated significantly with those of RN perfusion scans (P < 0.01). The correlation was higher using PC (r = 0.67) and PBF (r = 0.66) than using PBV (r = 0.50). The MR ratios computed from PBF showed the highest accuracy, followed by those from PC and PBV. Independently from the MR parameter used, in some patients the quantitative difference between the MR and RN ratios was not negligible. Conclusions:Pulmonary perfusion MRI can be used to assess the differential blood flow of the lung. Further studies in a larger group of patients are required to fully confirm the clinical suitability of this imaging method.

Dual‐bolus approach to quantitative measurement of pulmonary perfusion by contrast‐enhanced MRI

To evaluate a dual‐bolus approach to pulmonary perfusion MRI.

Impact of oxygen inhalation on the pulmonary circulation: assessment by magnetic resonance (MR)-perfusion and MR-flow measurements.

Purpose:Oxygen-enhanced magnetic resonance (MR)-ventilation imaging of the lung is based on the inhalation of a high concentration of oxygen (hyperoxia). However, the effect of hyperoxia on the pulmonary circulation is not yet fully understood. In this study the impact of hyperoxia on the pulmonary circulation was evaluated. Materials and Methods:Ten healthy volunteers were examined in a 1.5 T MRI system with contrast-enhanced perfusion MRI (saturation recovery 2D turboFLASH) of the lung and phase-contrast flow measurements in the pulmonary trunk. Both measurements were performed breathing room air (RA) and, subsequently, 100% oxygen (15 L/min) (O2). Results:The perfusion measurements showed a significant difference between RA and O2 for the pulmonary blood flow (181 vs. 257 mL/min/100 mL, P = 0.04) and blood volume (14 vs. 21 mL/100 mL, P = 0.008). The mean transit time of the contrast bolus was not changed (P = 0.4) in the dorsal part of the lung, whereas it was significantly prolonged (P = 0.006) in the central part. The mean heart rate during flow measurements breathing RA (67 ± 11 beats/min) and O2 (61 ± 12 beats/min) were not significantly different (P = 0.055). The average cardiac output (pulmonary trunk) was not significantly lower while breathing O2 (RA: 5.9 vs. O2: 5.5 L/min, P = 0.054). Conclusion:Hyperoxia causes a significant increase and redistribution of the pulmonary perfusion, whereas it leads to a not significant decrease in cardiac output. Thus, for MR-perfusion and MR-flow measurements oxygen inhalation should be avoided, if possible. In the context of oxygen-enhanced MR-ventilation imaging of the lung the contribution of this effect needs to be further evaluated.

Intraindividual comparison between gadopentetate dimeglumine and gadobutrol for magnetic resonance perfusion in normal brain and intracranial tumors at 3 Tesla.

Background: In vitro studies have shown that the 3-Tesla (T) magnetic resonance (MR) characteristics of high- and standard-molar gadolinium-based contrast agents differ. Such differences may indicate that high-molar (1.0 M) agents offer advantages for perfusion-weighted imaging (PWI) at 3T, as has been previously reported at 1.5T. Purpose: To investigate possible intraindividual differences of high- versus low-molar contrast agents on PWI at 3T in patients with intracranial space-occupying lesions. Material and Methods: Six patients with intraaxial and five patients with extraaxial tumors underwent two MR examinations at 3T, separated by at least 48 hours. On each occasion, an exogenous contrast-based, T2*-weighted, gradient-recalled echo-planar imaging (EPI) technique was used to determine the intracranial perfusion characteristics using one of two intravenous contrast agents: either 5 ml of 1.0 M gadobutrol or 10 ml of 0.5 M gadopentetate dimeglumine. The primary PWI outcome measure was region-of-interest maximal signal change (Cmax). Results: The difference in Cmax for gray and white matter (ΔCmax) was significantly higher for gadobutrol compared to gadopentetate dimeglumine (P<0.01). The ratio of Cmax between gray and white matter (rCmax = CmaxGray/CmaxWhite) was also significantly higher (median 24.6%, range 13.7–36.5%) for gadobutrol (P<0.01). The ratio of Cmax between the whole tumor and whole normal side hemisphere was higher in five out of the six intraaxial tumor cases. A significantly higher ratio (ΔCmax/Cmax) in the difference between Cmax of gray and white matter (from hemisphere without brain lesion) compared to Cmax for the hemisphere containing the neoplasm (hemisphere with brain lesion) was demonstrated for gadobutrol in intraaxial tumors (P<0.05). Conclusion: Higher-concentration 1.0 M gadobutrol can offer advantages over standard 0.5 M gadopentetate dimeglumine, particularly with respect to delineation between gray and white matter and for the demarcation of highly vascularized tumor tissue on brain PWI performed at 3T.

Improved visualization of delayed perfusion in lung MRI

INTRODUCTION The investigation of pulmonary perfusion by three-dimensional (3D) dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was proposed recently. Subtraction images are generated for clinical evaluation, but temporal information is lost and perfusion defects might therefore be masked in this process. The aim of this study is to demonstrate a simple analysis strategy and classification for 3D-DCE-MRI perfusion datasets in the lung without omitting the temporal information. MATERIALS AND METHODS Pulmonary perfusion measurements were performed in patients with different lung diseases using a 1.5 T MR-scanner with a time-resolved 3D-GRE pulse sequence. 25 3D-volumes were acquired after iv-injection of 0.1 mmol/kg KG Gadolinium-DTPA. Three parameters were determined for each pixel: (1) peak enhancement S(n,max) normalized to the arterial input function to detect regions of reduced perfusion; (2) time between arterial peak enhancement in the large pulmonary artery and tissue peak enhancement τ to visualize regions with delayed bolus onset; and (3) ratio R=S(n,max)/τ was calculated to visualize impaired perfusion, irrespectively of whether related to reduced or delayed perfusion. RESULTS A manual selection of peak perfusion images is not required. Five different types of perfusion can be found: (1) normal perfusion; (2) delayed non-reduced perfusion; (3) reduced non-delayed perfusion; (4) reduced and delayed perfusion; and (5) no perfusion. Types II and IV could not be seen in subtraction images since the temporal information is necessary for this purpose. CONCLUSIONS The analysis strategy in this study allows for a simple and observer-independent visualization and classification of impaired perfusion in dynamic contrast-enhanced pulmonary perfusion MRI by using the temporal information of the datasets.

Intraindividual comparison of 1.0 M gadobutrol and 0.5 M gadopentetate dimeglumine for time-resolved contrast-enhanced three-dimensional magnetic resonance angiography of the upper torso.

To compare the signal characteristics and bolus dynamics of 1.0 M gadobutrol and 0.5 M Gd‐DTPA for time‐resolved, three‐dimensional, contrast‐enhanced (CE) MRA of the upper torso.

Perfusionsmessung mit der T2*-Kontrastmitteldynamik in der Neuroonkologie : Physikalische Grundlagen und klinische Anwendungen

ZusammenfassungDie MRT-Perfusionsmessungen im Zentralnervensystem (ZNS) werden derzeit hauptsächlich mit der kontrastmittelverstärkten T2*-Dynamik durchgeführt, die die Passage eines schnellen Kontrastmittelbolus mit einer Serie von T2*-gewichteten MRT-Aufnahmen verfolgt und charakterisiert. Dabei wird der Signalabfall, bedingt durch den Suszeptibilitätseffekt des paramagnetischen Kontrastmittels, mittels geeigneter mathematischer Modelle, denen die Prinzipien der Indikatorverdünnungstheorie zugrunde liegen, in die Kontrastmittelkonzentration umgerechnet. Mittels einer „Region-of-interest-Analyse“ können Werte für den regionalen zerebralen Blutfluss und das regionale Blutvolumen berechnet werden.Dieser Übersichtsartikel beschreibt die physikalischen Grundlagen der Technik und fasst deren radiologische Anwendungen für die Neuroonkologie zusammen.Studien an relativ kleinen Patientenkollektiven berichten über eine Verbesserung der Differenzierung von Tumorrezidiv und Therapiekomplikationen, wie etwa der Strahlennekrose. Die Methode verhilft zur besseren Unterscheidung zwischen neoplastischen und nichtneoplastischen ZNS-Prozessen sowie zwischen ZNS-Lymphomen, Glioblastomen und singulären Metastasen und der Abgrenzung niedergradiger von anaplastischen Gliomen. Bei niedergradigen Gliomen kann die T2*-Dynamik den am stärksten vaskularisierten Tumoranteil mit der höchsten Anaplastizität zur zielgerichteten Biopsie visualisieren.Die ersten Ergebnisse zeigen, dass die T2*-Dynamik ein diagnostisches Instrument zur Visualisierung regionaler Variationen der Mikrovaskularität in gesundem und krankhaft verändertem Hirngewebe ist.AbstractPerfusion imaging in the central nervous system (CNS) is mostly performed using the first-pass dynamic susceptibility-weighted contrast-enhanced (DSC) MRI.The first-pass of a contrast bolus in brain tissue is monitored by a series of T2*-weighted MR images. The susceptibility effect of the paramagnetic contrast agent leads to a signal loss that can be converted, using the principles of the indicator dilution theory, into an increase of the contrast agent concentration. From these data, parameter maps of cerebral blood volume (CBV) and flow (CBF) can be derived. Regional CBF and CBV values can be obtained by region-of-interest analysis.This review article describes physical basics of DSC MRI and summarizes the literature of DSC MRI in neurooncological issues.Studies, all with relatively limited patient numbers, report that DSC MRI is useful in the preoperative diagnosis of gliomas, CNS-lymphomas, and solitary metastases, as well as in the differentiation of these neoplastic lesions from infections and tumor-like manifestations of demyelinating disease. Additionally, DSC MRI is suitable for determining glioma grade and regions of active tumor growth which should be the target of stereotactic biopsy. After therapy, DSC MRI helps better assessing the tumor response to therapy, residual tumor after therapy, and possible treatment failure and therapy-related complications, such as radiation necrosis.The preliminary results show that DSC MRI is a diagnostic tool depicting regional variations in microvasculature of normal and diseased brains.

Perfusionsmessung mit der T2*-Kontrastmitteldynamik in der Neuroonkologie

ZusammenfassungDie MRT-Perfusionsmessungen im Zentralnervensystem (ZNS) werden derzeit hauptsächlich mit der kontrastmittelverstärkten T2*-Dynamik durchgeführt, die die Passage eines schnellen Kontrastmittelbolus mit einer Serie von T2*-gewichteten MRT-Aufnahmen verfolgt und charakterisiert. Dabei wird der Signalabfall, bedingt durch den Suszeptibilitätseffekt des paramagnetischen Kontrastmittels, mittels geeigneter mathematischer Modelle, denen die Prinzipien der Indikatorverdünnungstheorie zugrunde liegen, in die Kontrastmittelkonzentration umgerechnet. Mittels einer „Region-of-interest-Analyse“ können Werte für den regionalen zerebralen Blutfluss und das regionale Blutvolumen berechnet werden.Dieser Übersichtsartikel beschreibt die physikalischen Grundlagen der Technik und fasst deren radiologische Anwendungen für die Neuroonkologie zusammen.Studien an relativ kleinen Patientenkollektiven berichten über eine Verbesserung der Differenzierung von Tumorrezidiv und Therapiekomplikationen, wie etwa der Strahlennekrose. Die Methode verhilft zur besseren Unterscheidung zwischen neoplastischen und nichtneoplastischen ZNS-Prozessen sowie zwischen ZNS-Lymphomen, Glioblastomen und singulären Metastasen und der Abgrenzung niedergradiger von anaplastischen Gliomen. Bei niedergradigen Gliomen kann die T2*-Dynamik den am stärksten vaskularisierten Tumoranteil mit der höchsten Anaplastizität zur zielgerichteten Biopsie visualisieren.Die ersten Ergebnisse zeigen, dass die T2*-Dynamik ein diagnostisches Instrument zur Visualisierung regionaler Variationen der Mikrovaskularität in gesundem und krankhaft verändertem Hirngewebe ist.AbstractPerfusion imaging in the central nervous system (CNS) is mostly performed using the first-pass dynamic susceptibility-weighted contrast-enhanced (DSC) MRI.The first-pass of a contrast bolus in brain tissue is monitored by a series of T2*-weighted MR images. The susceptibility effect of the paramagnetic contrast agent leads to a signal loss that can be converted, using the principles of the indicator dilution theory, into an increase of the contrast agent concentration. From these data, parameter maps of cerebral blood volume (CBV) and flow (CBF) can be derived. Regional CBF and CBV values can be obtained by region-of-interest analysis.This review article describes physical basics of DSC MRI and summarizes the literature of DSC MRI in neurooncological issues.Studies, all with relatively limited patient numbers, report that DSC MRI is useful in the preoperative diagnosis of gliomas, CNS-lymphomas, and solitary metastases, as well as in the differentiation of these neoplastic lesions from infections and tumor-like manifestations of demyelinating disease. Additionally, DSC MRI is suitable for determining glioma grade and regions of active tumor growth which should be the target of stereotactic biopsy. After therapy, DSC MRI helps better assessing the tumor response to therapy, residual tumor after therapy, and possible treatment failure and therapy-related complications, such as radiation necrosis.The preliminary results show that DSC MRI is a diagnostic tool depicting regional variations in microvasculature of normal and diseased brains.

New method for 3D parametric visualization of contrast-enhanced pulmonary perfusion MRI data

Three-dimensional (3D) dynamic contrast-enhanced magnetic resonance imaging (3D DCE-MRI) has been proposed for the assessment of regional perfusion. The aim of this work was the implementation of an algorithm for a 3D parametric visualization of lung perfusion using different cutting planes and volume rendering. Our implementation was based on 3D DCE-MRI data of the lungs of five patients and five healthy volunteers. Using the indicator dilution theory, the regional perfusion parameters, tissue blood flow, blood volume and mean transit time were calculated. Due to the required temporal resolution, the volume elements of dynamic MR data sets show a reduced spatial resolution in the z-direction. Therefore, perfusion parameter volumes were interpolated. Linear interpolation and a combination of linear and nearest-neighbor interpolation were evaluated. Additionally, ray tracing was applied for 3D visualization. The linear interpolation algorithm caused interpolation errors at the lung borders. Using the combined interpolation, visualization of perfusion information in arbitrary cutting planes and in 3D using volume rendering was possible. This facilitated the localization of perfusion deficits compared with the coronal orientated source data. The 3D visualization of perfusion parameters using a combined interpolation algorithm is feasible. Further studies are required to evaluate the additional benefit from the 3D visualization.