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ZusammenfassungNuklearmedizinische tomografische Verfahren wie die Positronen-Emissions-Tomografie (PET) und Single-Photonen-Emissions-Computertomografie (SPECT) werden in einem quantitativen Setting genutzt (z. B. die PET) bzw. sind, wie im Fall der SPECT, aufgrund der Erfordernisse nuklearmedizinischer Therapien an eine bildbasierte Dosimetrie, als quantitative bildgebende Modalität zu etablieren. Für die quantitative Analyse der bereitgestellten Bilddaten existieren unterschiedliche Konzepte. Ausgehend von der Quantifizierung dynamischer Aufnahmen mittels der Zeitaktivitätskurve wird für die kinetische Modellierung die Patlak-Methode vorgestellt. Verschiedene Methoden zur Auswertung statischer PET-Messungen, wie der Standardized Uptake Value (SUV) und das Standardized Uptake Ratio (SUR), werden diskutiert. Für die SPECT werden exemplarisch verschiedene methodische Entwicklungen auf dem Weg zur quantitativen Modalität adressiert.

ZusammenfassungAuch wenn bei der Radionuklidtherapie die individuelle Dosimetrie unter Mitwirkung des Medizin-Physik-Experten in der Strahlenschutzverordnung (StrSchV) festgeschrieben ist, bestehen unterschiedliche Auffassungen über das Ausmaß der Datenerfassung und auch technische Limitationen im Hinblick auf eine valide Bildgebung zur Bestimmung der Biokinetik. Dabei ist für die klinische Anwendung stets eine einfache und robuste Approximation zu bevorzugen.Für wissenschaftliche Fragestellungen und für die Berücksichtigung der biologisch effektiven Dosis bedarf es jedoch valider Algorithmen, insbesondere für die Kombination interner und externer Radiotherapie. Die Anwendung von Alphastrahlern mit geringen Aktivitätsmengen und geringer Emissionswahrscheinlichkeit von Gammastrahlung zur Bilderzeugung zwingt jedoch teilweise, auf Standardaktivitätsmengen auszuweichen oder sich an Wirkung und Nebenwirkung analog zu anderer onkologischer Systemtherapie zu orientieren.

ZusammenfassungNach einer einführenden Erklärung der Funktionsweise der Positronen-Emissions-Tomografie (PET) Diagnostik werden Inhalt und Ziel der Rekonstruktion von PET-Daten vorgestellt. Es wird dargelegt, welche physikalischen Prozesse die PET-Bildgebung beeinflussen und wie diese im Rahmen der Rekonstruktion von PET-Daten korrigiert werden können. Dazu gehören Korrekturen für zufällige, gestreute und absorbierte Photonen sowie Korrekturen für Totzeiteffekte des Detektors.Die beiden gängigsten PET-Rekonstruktionsverfahren, die gefilterte Rückprojektion (Filtered Back Projection, FBP) und der iterative Rekonstruktionsalgorithmus, werden erklärt und die jeweiligen Vor- und Nachteile dargelegt. Auf zwei Beispiele der iterativen Rekonstruktionsmethode wird detaillierter eingegangen: das Verfahren der Maximum Likelihood Expectation Maximization (MLEM) und die aktuell in der klinischen PET-Bildgebung am häufigsten angewendete Methode der Ordered Subsets Expectation Maximization (OSEM) Rekonstruktion. Weiterhin werden verschiedene Möglichkeiten der Reduktion von Bildrauschen bei iterativen Rekonstruktionen vorgestellt, wie beispielsweise die Bayesian Penalized Likelihood (BPL) Methode.Es wird auf technische Neuerungen hinsichtlich der Gerätetechnik und der Software von PET-Geräten eingegangen. Time of Flight (ToF) Messung und Point Spread Function (PSF) Modellierungen im Rahmen der Rekonstruktion werden erklärt und deren Vor- und Nachteile dargestellt. Abschließend werden neue Möglichkeiten der datengestützten Bewegungskorrektur (data-driven motion correction) und Ansätze mittels künstlicher Intelligenz aufgegriffen.

Background: Atelectasis is one of the most common respiratory complications in patients undergoing open abdominal surgery. Peripheral oxygen saturation (SpO2) and forced vital capacity (FVC) are bedside indicators of postoperative respiratory dysfunction. The aim of this study was to describe the changes in lung aeration, using quantitative analysis of magnetic resonance imaging (MRI) and the diagnostic accuracy of SpO2 and FVC to detect postoperative atelectasis. Methods: Post-hoc analysis of a randomized trial conducted at a University Hospital in Dresden, Germany. Patients undergoing pre- and postoperative lung MRI were included. MRI signal intensity was analyzed quantitatively to define poorly and nonaerated lung compartments. Postoperative atelectasis was defined as nonaerated lung volume above 2% of the total lung volume in the respective MRI investigation. Results: This study included 45 patients, 27 with and 18 patients without postoperative atelectasis. Patients with atelectasis had higher body mass index (p =.024), had more preoperative poorly aerated lung volume (p =.049), a lower preoperative SpO2 (p =.009), and a lower preoperative FVC (p =.029). The amount of atelectasis correlated with preoperative SpO2 (Spearman's ρ = −.51, p

Recently, dose reference levels (DRLs) have been defined in Germany for auxiliary low-dose CT scans in hybrid SPECT/CT and PET/CT examinations, based on data from 2016/17. Here, another survey from 2020 was evaluated and compared with the new DRLs as well as with similar surveys from foreign countries.The survey, which had already been conducted in the Nordic countries, queried for various examinations including the following values: patient weight and height, volume CT dose index (CTDIData from 15 SPECT/CT and 13 PET/CT systems from 15 nuclear medicine departments were collected. For the following examinations datasets from more than 10 systems were submitted: SPECT lung VQ, SPECT bone, SPECTPET cardiac, PET brain, PET oncology. Especially for examinations of the thorax and heart, the new DRLs are very strict compared to this study. The CTDIFor certain examination types, there is a need for dose optimization at some clinics and devices in order to take into account the new DRLs in Germany in the future.ZIEL: Seit Kurzem gibt es in Deutschland für auxiliäre Niedrigdosis-CT-Aufnahmen bei SPECT/CT- und PET/CT-Untersuchungen Dosisreferenzwerte (DRW), welche auf Daten von 2016/17 basieren. Hier wurde eine weitere Umfrage aus dem Jahr 2020 ausgewertet und mit den neuen DRW sowie mit ähnlichen Umfragen aus anderen Ländern verglichen.Die Umfrage, welche bereits in den nordischen Ländern durchgeführt wurde, erfasste für unterschiedliche Einsatzbereiche u.a. folgende Werte: Patientengewicht/-größe, volumenbezogener CT-Dosisindex (CTDIDaten von insgesamt 15 SPECT/CT- und 13 PET/CT-Geräten aus 15 Zentren wurden erhoben. Hierbei beinhalteten die Daten z.B. folgender Untersuchungen mehr als 10 Geräte: Lungen-SPECT, Knochen-SPECT, kardiologisches SPECTPET, Hirn-PET, onkologisches PET. Besonders für Untersuchungen des Thorax und des Herzens sind die neuen DRW im Vergleich zu dieser Studie sehr streng. Die CTDIFür einzelne Untersuchungstypen besteht bei einigen Kliniken und Geräten Dosisoptimierungsbedarf, um die neuen DRW in Deutschland zukünftig zu berücksichtigen.

Background Mechanical ventilation with variable tidal volumes (VT) may improve lung function and reduce ventilator-induced lung injury in experimental acute respiratory distress syndrome (ARDS). However, previous investigations were limited to less than 6 h, and control groups did not follow clinical standards. We hypothesised that 24 h of mechanical ventilation with variable VT reduces pulmonary inflammation (as reflected by neutrophil infiltration), compared with standard protective, nonvariable ventilation. Methods Experimental ARDS was induced in 14 anaesthetised pigs with saline lung lavage followed by injurious mechanical ventilation. Pigs (n=7 per group) were randomly assigned to using variable VT or nonvariable VT modes of mechanical ventilation for 24 h. In both groups, ventilator settings including positive end-expiratory pressure and oxygen inspiratory fraction were adjusted according to the ARDS Network protocol. Pulmonary inflammation (primary endpoint) and perfusion were assessed by positron emission tomography using 2-deoxy-2-[18F]fluoro-d-glucose and 68Gallium (68Ga)-labelled microspheres, respectively. Gas exchange, respiratory mechanics, and haemodynamics were quantified. Lung aeration was determined using CT. Results The specific global uptake rate of 18F-FDG increased to a similar extent regardless of mode of mechanical ventilation (median uptake for variable VT=0.016 min−1 [inter-quartile range, 0.012–0.029] compared with median uptake for nonvariable VT=0.037 min−1 [0.008–0.053]; P=0.406). Gas exchange, respiratory mechanics, haemodynamics, and lung aeration and perfusion were similar in both variable and nonvariable VT ventilatory modes. Conclusion In a porcine model of ARDS, 24 h of mechanical ventilation with variable VT did not attenuate pulmonary inflammation compared with standard protective mechanical ventilation with nonvariable VT.

Background The analysis aimed to compare the radiotracers [68Ga]-Ga-PSMA-11 and [18F]-F-PSMA-1007 intraindividually in terms of malignant lesions, mi(molecular-imaging)TNM staging and presumable unspecific lesions retrospectively as used in routine clinical practice. Methods A retrospective analysis of 46 prostate cancer patients (median age: 71 years) who underwent consecutive [68Ga]-Ga-PSMA-11- and [18F]-F-PSMA-1007-PET/CT or PET/MRI within a mean of 12 ± 8.0 days was performed. MiTNM staging was performed in both studies by two nuclear medicine physicians who were blinded to the results of the other tracer. After intradisciplinary and interdisciplinary consensus with two radiologists was reached, differences in both malignant and presumable nonspecific tracer accumulation were analyzed. Results Differences in terms of miTNM stages in both studies occurred in nine of the 46 patients (19.6%). The miT stages differed in five patients (10.9%), the miN stages differed in three patients (6.5%), and different miM stages occurred only in one patient who was upstaged in [18F]-F-PSMA-1007 PET. Concordant miTNM stages were obtained in 37 patients (80.4%). There was no significant difference between [18F]-F-PSMA-1007 and [68Ga]-Ga-PSMA-11 in the SUVmax locally (31.5 vs. 32.7; p = 0.658), in lymph node metastases (28.9 vs. 24.9; p = 0.30) or in bone metastases (22.9 vs. 27.6; p = 0.286). In [18F]-F-PSMA-1007 PET, more patients featured presumable unspecific uptake in the lymph nodes (52.2% vs. 28.3%; p: p p 18F]-F-PSMA-1007-positive lesions mainly occurred in the ribs (58.7%), axillary lymph nodes (39.1%) and cervical ganglia (28.3%). Conclusion In terms of miTNM staging, both tracers appeared widely exchangeable, as no tracer relevantly outperformed the other. The differences between the two tracers were far more common in presumable unspecific lesions than in malignant spots. A routinely performed two-tracer study could not be shown to be superior. Since it seems at least challenging for most nuclear medicine departments to provide both [18F]-F-PSMA-1007 and [68Ga]-Ga-PSMA-11, it appears reasonable to choose the PSMA radiotracer depending on local availability with attention to the greater occurrence of nonspecific bone findings with [18F]-F-PSMA-1007.

The application of 225Ac (half-life T1/2 = 9.92 d) dramatically reduces the activity used for peptide receptor radionuclide therapy by a factor of 1000 in comparison to 90Y, 177Lu or 188Re while maintaining the therapeutic outcome. Additionally, the range of alpha particles of 225Ac and its daughter nuclides in tissue is much lower (47–85 μm for alpha energies Eα = 5.8–8.4 MeV), which results in a very precise dose deposition within the tumor. DOTA-conjugated commercially available peptides used for endoradiotherapy, which can readily be labeled with 177Lu or 90Y, can also accommodate 225Ac. The benefits are lower doses in normal tissue for the patient, dose reduction of the employees and environment and less shielding material. The low availability of 225Ac activity is preventing its application in clinical practice. Overcoming this barrier would open a broad field of 225Ac therapy. Independent which production pathway of 225Ac proves the most feasible, the use of automated synthesis and feasible and reproducible patient doses are needed. The Modular-Lab EAZY is one example of a GMP-compliant system, and the cassettes used for synthesis are small. Therefore, also the waste after the synthesis can be minimized. In this work, two different automated setups with different purification systems are presented. In its final configuration, three masterbatches were performed on the ML EAZY for DOTA-TATE and PSMA-I&amp, T, respectively, fulfilling all quality criteria with final radiochemical yields of 80–90% for the 225Ac-labeled peptides.

The aim of this study is to assess if the number of radiation-induced double strand breaks (DSB) in lymphocytes of prostate cancer patients is affected after repeated Ra-223 therapies. In addition, we investigated the repair of ex vivo induced DSB to investigate the repair proficiency in patient's lymphocytes over the therapy course.Before each of six therapy cycles, blood samples were obtained from seventeen patients. After separation of lymphocytes, the cells were subjected to immunofluorescence staining for detection of DSB-marking γH2AX foci. The number of foci per cell per patient sample was determined for each cycle (X1-X6, baseline foci per cell). Additionally, appropriate samples were exposed ex vivo to an X-ray dose of 1 Gy. The number of γH2AX foci per cell were analyzed after 0.5 h, 2 h and 24 h of recovery.Patient-specific linear regression of the baseline foci per cell over the therapy cycles revealed no significant slopes in the regression lines. Likewise, the mean baseline foci per cell of all patients for cycles X2-X6 was not significantly elevated in comparison to the pre-therapeutic value (X1). The differences between the percentages of residual DSB and cycles were not significant, both at 2 h and 24 h repair time. Consideration of the X6/X1 ratios of both the number of lymphocytes and the amount of residual damage at 24 h indicated a significant correlation.Our findings indicate that the number of γH2AX foci per cell was not changed in dependence on the Ra-223 therapy cycles. The ability of patient's lymphocytes to repair ex vivo induced DSB remained unaffected throughout the entire therapy course.ZIEL: Das Ziel dieser Studie ist die Analyse von strahleninduzierten Doppelstrangbrüchen (DSB) in Lymphozyten von Prostatakarzinompatienten im Verlauf der sechs Ra-223 Therapiezyklen (X1-X6). Die Reparaturkapazität der Lymphozyten wurde nach Applikation einer ex vivo Bestrahlung mit 1 Gy Röntgenstrahlung evaluiert.Von 17 Patienten wurden vor jedem Therapiezyklus (X1-X6) Blutproben entnommen, die Lymphozyten isoliert und die DSB-assoziierten γH2AX Foci pro Zelle (Basiswerte) mit Immunfluoreszenzfärbung detektiert. Weiterhin wurden die entsprechenden Lymphozytenproben ex vivo mit 1 Gy Röntgenstrahlung bestrahlt und nach 0,5 h, 2 h und 24 h Reparaturzeit die γH2AX Foci pro Zelle bestimmt.Die Analyse der γH2AX Basiswerte für die einzelnen Patienten zeigte keine signifikanten Anstiege im Therapieverlauf. Die gemittelten γH2AX Basiswerte der Zyklen X2-X6 waren im Vergleich zum prätherapeutischen Wert (X1) nicht signifikant erhöht. Ein signifikanter Einfluss wiederholter Ra-223 Therapien auf die Reparatur ex vivo erzeugter DSB konnte nicht gefunden werden. Die Relation der Lymphozytenanzahl (X6/X1) korreliert mit der Relation residualer DSB (X6/X1) nach 24 h Reparaturzeit.Wiederholt applizierte Ra-223 Therapien zeigten mit dem verwendeten γH2AX Assay als DSB-Marker weder Auswirkungen auf die Basiswerte noch auf das Reparaturvermögen ex vivo induzierter DSB in Lymphozyten der Prostatakarzinom-Patienten.

Objectives To determine the impact of positive end-expiratory pressure during mechanical ventilation with and without spontaneous breathing activity on regional lung inflammation in experimental nonsevere acute respiratory distress syndrome. Design Laboratory investigation. Setting University hospital research facility. Subjects Twenty-four pigs (28.1-58.2 kg). Interventions In anesthetized animals, intrapleural pressure sensors were placed thoracoscopically in ventral, dorsal, and caudal regions of the left hemithorax. Lung injury was induced with saline lung lavage followed by injurious ventilation in supine position. During airway pressure release ventilation with low tidal volumes, positive end-expiratory pressure was set 4 cm H2O above the level to reach a positive transpulmonary pressure in caudal regions at end-expiration (best-positive end-expiratory pressure). Animals were randomly assigned to one of four groups (n = 6/group; 12 hr): 1) no spontaneous breathing activity and positive end-expiratory pressure = best-positive end-expiratory pressure - 4 cm H2O, 2) no spontaneous breathing activity and positive end-expiratory pressure = best-positive end-expiratory pressure + 4 cm H2O, 3) spontaneous breathing activity and positive end-expiratory pressure = best-positive end-expiratory pressure + 4 cm H2O, 4) spontaneous breathing activity and positive end-expiratory pressure = best-positive end-expiratory pressure - 4 cm H2O. Measurements and main results Global lung inflammation assessed by specific [F]fluorodeoxyglucose uptake rate (median [25-75% percentiles], min) was decreased with higher compared with lower positive end-expiratory pressure both without spontaneous breathing activity (0.029 [0.027-0.030] vs 0.044 [0.041-0.065]; p = 0.004) and with spontaneous breathing activity (0.032 [0.028-0.043] vs 0.057 [0.042-0.075]; p = 0.016). Spontaneous breathing activity did not increase global lung inflammation. Lung inflammation in dorsal regions correlated with transpulmonary driving pressure from spontaneous breathing at lower (r = 0.850; p = 0.032) but not higher positive end-expiratory pressure (r = 0.018; p = 0.972). Higher positive end-expiratory pressure resulted in a more homogeneous distribution of aeration and regional transpulmonary pressures at end-expiration along the ventral-dorsal gradient, as well as a shift of the perfusion center toward dependent zones in the presence of spontaneous breathing activity. Conclusions In experimental mild-to-moderate acute respiratory distress syndrome, positive end-expiratory pressure levels that stabilize dependent lung regions reduce global lung inflammation during mechanical ventilation, independent from spontaneous breathing activity.

BACKGROUND Patient-ventilator asynchrony during mechanical ventilation may exacerbate lung and diaphragm injury in spontaneously breathing subjects. We investigated whether subject-ventilator asynchrony increases lung and/or diaphragmatic injury in a porcine model of acute respiratory distress syndrome (ARDS). METHODS ARDS was induced in adult female pigs by lung lavage and injurious ventilation, before mechanical ventilation by pressure assist-control for 12h. Mechanically ventilated pigs were randomised to spontaneously breath with, or without, induced subject-ventilator asynchrony, or neuromuscular blockade (n=7/group). Subject-ventilator asynchrony was produced by ineffective, auto- or double-triggering of spontaneous breaths. The primary outcome was mean alveolar septal thickness (where thickening of the alveolar wall indicates worse lung injury). Secondary outcomes included distribution of ventilation (electrical impedance tomography), lung morphometric analysis, inflammatory biomarkers (gene expression), lung wet-to-dry ratio and diaphragmatic muscle fibre thickness. RESULTS Mean alveolar septal thickness was similar in pigs randomised to subject-ventilator asynchrony (mean (SD):29.5% (10.8) asynchronous breaths of total breaths; n=7) compared to synchronous spontaneous breathing (asynchronous breaths 1.8% (2.9) of total breaths; n=7). There was no difference in mean alveolar septal thickness throughout upper and lower lungs lobes between pigs randomised to subject-ventilator asynchrony versus synchronous spontaneous breathing (87.3-92.2μm after subject-ventilator asynchrony, compared to 84.1-95.0 μm in synchronised spontaneous breathing; P=0.956). There were also no differences between groups in wet-to-dry ratio, diaphragmatic muscle fibre thickness, atelectasis, lung aeration, and mRNA expression levels for inflammatory cytokines pivotal in ARDS pathogenesis. CONCLUSION Subject-ventilator asynchrony during spontaneous breathing did not exacerbate lung injury and dysfunction in experimental ARDS.

Summary Aim: We compared 68Gallium (68Ga)- and fluorescence-labeled microspheres for measurement of pulmonary perfusion distribution in anesthetized pigs without lung injury. Methods: In two mechanically ventilated pigs, the distribution of pulmonary perfusion was marked in vivo with 68Ga- and fluorescence-labeled microspheres in supine and prone position. After each injection, the distribution of 68Ga-labeled microspheres was measured in vivo with positron emission tomography/ computed tomography (PET/CT) in the position in which microspheres were injected and vice versa. The distribution of fluorescence-labeled microspheres was measured ex vivo. Perfusion distributions were compared between methods and postures within four lung regions and along the ventro-dorsal gradient. After each injection of 68Ga-labeled microspheres, changes in ventro-dorsal perfusion gradients induced by repositioning were compared for volume- and mass-normalized PET/CT measurements. Results: Regional and gradient analyses of in vivo and ex vivo measurements, respectively, consistently revealed higher pulmonary perfusion in dorsal than ventral regions in supine positioned animals. Both methods showed more pronounced perfusion gradients in supine compared to prone position. Changes in animal position were associated with alterations in the ventro-dorsal perfusion gradient when volume-, but not mass-normalization was conducted for PET/CT data. Conclusions: Ex vivo fluorescence- and in vivo 68Ga-labeled microspheres measurements revealed similar perfusion distributions. Mass-normalized perfusion measurements by 68Ga-labeled microspheres and PET/CT were not affected by positioning artifacts.

Aim 68Ga-PSMA-11 is the gold standard for molecular imaging of prostate cancer. However, recurrent tumor manifestations or metastases cannot be detected in every case. Therefore, we investigated if there is an additive value of the gastrin-releasing peptide receptor (GRP-R) ligand 68Ga-RM2 compared to the well-established 68Ga-PSMA-11 in patients with (Group 1) and without (Group 2) pathologic PSMA-expression in different tumor stages. Patients and Methods Sixteen men (median age: 74 years, range 50–80 years) with prostate cancer in different stages who had a recent negative (n = 8) or pathologic (n = 8) PSMA PET underwent a subsequent 68Ga-RM2 PET. Both examinations were analyzed qualitatively and quantitatively and compared in terms of pathologic and physiologic tracer distribution. Results None of the PSMA-negative patients showed any pathological RM2-accumulation. Pathologic PSMA-uptake was observed in 8 patients of whom 5 had pathologic RM2-uptake. The number of patients with a local recurrence was equal in both scans (n = 3). Bone metastases and lymph node metastases were detected in less patients in RM2 PET compared to PSMA PET (n = 4 vs. 7 and n = 2 vs. 5, respectively). In one patient, PSMA-positive liver metastases were not detected in RM2. RM2 PET revealed two additional lesions indicative for bone metastases in two patients with multiple PSMA-positive bone metastases, which had no therapeutic consequence. Conclusion At least in our small and heterogeneous patient population, 68Ga-RM2 showed no clinically relevant, additional benefit compared to 68Ga-PSMA-11 PET.

Background Electrical impedance tomography (EIT) with indicator dilution may be clinically useful to measure relative lung perfusion, but there is limited information on the performance of this technique. Methods Thirteen pigs (50–66 kg) were anaesthetised and mechanically ventilated. Sequential changes in ventilation were made: (i) right-lung ventilation with left-lung collapse, (ii) two-lung ventilation with optimised PEEP, (iii) two-lung ventilation with zero PEEP after saline lung lavage, (iv) two-lung ventilation with maximum PEEP (20/25 cm H2O to achieve peak airway pressure 45 cm H2O), and (v) two-lung ventilation under unilateral pulmonary artery occlusion. Relative lung perfusion was assessed with EIT and central venous injection of saline 3%, 5%, and 10% (10 ml) during breath holds. Relative perfusion was determined by positron emission tomography (PET) using 68Gallium-labelled microspheres. EIT and PET were compared in eight regions of equal ventro-dorsal height (right, left, ventral, mid-ventral, mid-dorsal, and dorsal), and directional changes in regional perfusion were determined. Results Differences between methods were relatively small (95% of values differed by less than 8.7%, 8.9%, and 9.5% for saline 10%, 5%, and 3%, respectively). Compared with PET, EIT underestimated relative perfusion in dependent, and overestimated it in non-dependent, regions. EIT and PET detected the same direction of change in relative lung perfusion in 68.9–95.9% of measurements. Conclusions The agreement between EIT and PET for measuring and tracking changes of relative lung perfusion was satisfactory for clinical purposes. Indicator-based EIT may prove useful for measuring pulmonary perfusion at bedside.

Ziel/Aim: Dynamische PET/CT Scans gefolgt von Patlak Modellierung der 18F-FDG-Aufnahmerate (Ki) ist eine etablierte Methode zur Quantifizierung der Lungenentzündung im tierexp. Modell des akuten Lungenversagens (ARDS), erfordert aber zeitintensive Aufnahmen und erlaubt nur ein begrenztes cranio-caudales FoV. Dyn. PET/CT Scans von Patienten mit Lebermetastasen zeigten gute Korrelationen zwischen Ki und Standard Uptake Ratio (SUR = ROI-SUV / Blut-SUV) [1]. Wir analysierten in einem tierexp. ARDS-Modell, ob stat. PET/CT Messungen und SUR-Analysen alternativ zu dyn. PET/CT und Ki für die Quantifizierung der pulmonalen Inflammation genutzt werden können. Methodik/Methods: In 14 Schweinen erfolgten nach Induktion eines schweren ARDS sowie nach 24h Beatmung dyn. 18F-FDG-PET/CT Scans und Patlak Ki-Analysen. Anschließende stat. PET/CT Scans (77-81min p.i.) wurden für die Bestimmung von mittleren, zeitkorrigierten SUR-Werte genutzt. SUR- und Ki-Werte wurden für 5 ventro-dorsale ROIs mittels linearer Regression verglichen (Variationskoeffizient, r2). Anhand von Blutproben wurde die Variabilität der arteriellen Inputfunktion (AIF) zwischen Tieren und Messzeitpunkten verglichen. Ergebnisse/Results: SUR- und Ki-Werte korrelierten vor und nach 24h Beatmung (r2=0.84 bzw. 0.97). Der zeitliche Verlauf der AIF war zwischen Tieren und Aufnahmezeitpunkten vergleichbar und konnte mittels einer inversen Potenzfunktion beschrieben werden (r2 = 0.99). Die Patlak-Zeit war Zeit-, aber nicht AIF-abhängig, und wies eine geringe Variabilität auf (t=70min: 153.6 ± 13.3min). Schlussfolgerungen/Conclusions: Für die Quantifizierung der pulmonalen Inflammation in exp. Studien der Anästhesie können stat. PET/CT Scans und SUR-Analysen alternativ zu dyn. 18F-FDG-PET/CT und Patlak genutzt werden. Dies ermöglicht eine schnellere Datenakquisition, die Erfassung der gesamten Lunge und eine Reduktion der erforderlichen Blutproben. Grundlage der guten Ki-SUR Korrelation bildete die geringe Variabilität des AIF.

Positron Emission Tomography (PET) imaging with 18F-FDG followed by mathematical modelling of the pulmonary uptake rate (Ki) is the gold standard for assessment of pulmonary inflammation in experimental studies of acute respiratory distress syndrome (ARDS). However, dynamic PET requires long imaging and only allows the assessment of one cranio-caudal field of view (~15 cm). We investigated whether static 18F-FDG-PET/CT and analysis of standard uptake values (SUV) or standard uptake ratios (SURstat, uptake time corrected ratio of 18F-FDG-concentration in lung tissue and blood plasma) might be an alternative to dynamic 18F-FDG-PET/CT and Patlak analysis for quantification of pulmonary inflammation in experimental ARDS. METHODS: ARDS was induced by saline lung lavage followed by injurious mechanical ventilation in fourteen anesthetized pigs (29.5-40.0 kg). PET/CT imaging sequences were acquired before and after 24 h of mechanical ventilation. Ki and the apparent volume of distribution (Vdist) were calculated from dynamic 18F-FDG-PET/CT scans using the Patlak analysis. Static 18F-FDG-PET/CT scans were obtained immediately after dynamic PET/CT and used for calculations of SUV and SURstat. Mean Ki values of the whole imaged field of view and of five ventro-dorsal lung regions were compared with corresponding SUV and SURstat values, respectively, by means of linear regression and concordance analysis. The variability of the 18F-FDG concentration in blood plasma (arterial input function) was analyzed. RESULTS: Both for the whole imaged field of view and ventro-dorsal subregions, Ki were linearly correlated with SURstat (r2 ≥ 0.84), while Ki-SUV correlations were worse (r2 ≤ 0.75). The arterial input function exhibited an essentially invariant shape across all animals and time points and can be described by an inverse power law. Compared to Ki, SURstat and SUV tracked the same direction of change in regional lung inflammation in 98.6 % and 84.3 % of measurements, respectively. CONCLUSION: The Ki-SURstat correlation was considerably stronger than the Ki-SUV correlation. The good Ki-SURstat correlation suggests that static 18F-FDG-PET/CT and SURstat analysis provides an alternative to dynamic 18F-FDG-PET/CT and Patlak analysis, allowing the assessment of inflammation of whole lungs, repeated measurements within the period of 18F-FDG decay, and faster data acquisition.

BACKGROUND Both Electrical Impedance Tomography (EIT) and Computed Tomography (CT) allow the estimation of the lung area. We compared two algorithms for the detection of the lung area per quadrant from the EIT images with the lung areas derived from the CT images. METHODS 39 outpatients who were scheduled for an elective CT scan of the thorax were included in the study. For each patient we recorded EIT images immediately before the CT scan. The lung area per quadrant was estimated from both CT and EIT data using two different algorithms for the EIT data. RESULTS Data showed considerable variation during spontaneous breathing of the patients. Overall correlation between EIT and CT was poor (0.58-0.77), the correlation between the two EIT algorithms was better (0.90-0.92). Bland-Altmann analysis revealed absence of bias, but wide limits of agreement. CONCLUSIONS Lung area estimation from CT and EIT differs significantly, most probably because of the fundamental difference in image generation.

Background Experimental studies showed that controlled variable ventilation (CVV) yielded better pulmonary function compared to non-variable ventilation (CNV) in injured lungs. We hypothesized that CVV improves intraoperative and postoperative respiratory function in patients undergoing open abdominal surgery. Methods Fifty patients planned for open abdominal surgery lasting >3 h were randomly assigned to receive either CVV or CNV. Mean tidal volumes and PEEP were set at 8 ml kg−1 (predicted body weight) and 5 cm H2O, respectively. In CVV, tidal volumes varied randomly, following a normal distribution, on a breath-by-breath basis. The primary endpoint was the forced vital capacity (FVC) on postoperative Day 1. Secondary endpoints were oxygenation, non-aerated lung volume, distribution of ventilation, and pulmonary and extrapulmonary complications until postoperative Day 5. Results FVC did not differ significantly between CVV and CNV on postoperative Day 1, 61.5 (standard deviation 22.1) % vs 61.9 (23.6) %, respectively; mean [95% confidence interval (CI)] difference, −0.4 (−13.2–14.0), P=0.95. Intraoperatively, CVV did not result in improved respiratory function, haemodynamics, or redistribution of ventilation compared to CNV. Postoperatively, FVC, forced expiratory volume at the first second (FEV1), and FEV1/FVC deteriorated, while atelectasis volume and plasma levels of interleukin-6 and interleukin-8 increased, but values did not differ between groups. The incidence of postoperative pulmonary and extrapulmonary complications was comparable in CVV and CNV. Conclusions In patients undergoing open abdominal surgery, CVV did not improve intraoperative and postoperative respiratory function compared with CNV. Clinical trial registration NCT 01683578.

Background Quantitative lung computed tomography (CT) provides fundamental information about lung aeration in critically ill patients. We tested a scanning protocol combining reduced number of CT slices and tube current, comparing quantitative analysis and radiation exposure to conventional CT. Methods In pigs, CT scans were performed during breath hold in a model of lung injury with three different protocols: standard spiral with 180 mAs tube current-time product (Spiral180), sequential with 20-mm distance between slices and either 180 mAs (Sequential180) or 50 mAs (Sequential50). Spiral scans of critically ill patients were collected retrospectively, and subsets of equally spaced slices were extracted. The agreement between CT protocols was assessed with Bland–Altman analysis. Results In 12 pigs, there was good concordance between the sequential protocols and the spiral scan (all biases ≤1.9%, agreements ≤±6.5%). In Spiral180, Sequential180 and Sequential50, estimated dose exposure was 2.3 (2.1–2.8), 0.21 (0.19–0.26), and 0.09 (0.07–0.10) mSv, respectively (p

Objective:Volutrauma and atelectrauma promote ventilator-induced lung injury, but their relative contribution to inflammation in ventilator-induced lung injury is not well established. The aim of this study was to determine the impact of volutrauma and atelectrauma on the distribution of lung inflam

Background: Spontaneous breathing (SB) in the early phase of the acute respiratory distress syndrome is controversial. Biphasic positive airway pressure/airway pressure release ventilation (BIPAP/APRV) is commonly used, but the level of SB necessary to maximize potential beneficial effects is unknown. Methods: Experimental acute respiratory distress syndrome was induced by saline lung lavage in anesthetized and mechanically ventilated pigs (n = 12). By using a Latin square and crossover design, animals were ventilated with BIPAP/APRV at four different levels of SB in total minute ventilation (60 min each): (1) 0% (BIPAP/APRV0%); (2) greater than 0 to 30% (BIPAP/APRV>0–30%); (3) greater than 30 to 60% (BIPAP/APRV>30–60%); and (4) greater than 60% (BIPAP/APRV>60%). Gas exchange, hemodynamics, and respiratory variables were measured. Lung aeration was assessed by high-resolution computed tomography. The distribution of perfusion was marked with 68Ga-labeled microspheres and evaluated by positron emission tomography. Results: The authors found that higher levels of SB during BIPAP/APRV (1) improved oxygenation; (2) decreased mean transpulmonary pressure (stress) despite increased inspiratory effort; (3) reduced nonaerated lung tissue, with minimal changes in the distribution of perfusion, resulting in decreased low aeration/perfusion zones; and (4) decreased global strain (mean ± SD) (BIPAP/APRV0%: 1.39 ± 0.08; BIPAP/APRV0–30%: 1.33 ± 0.03; BIPAP/APRV30–60%: 1.27 ± 0.06; BIPAP/APRV>60%: 1.25 ± 0.04, P < 0.05 all vs. BIPAP/APRV0%, and BIPAP/APRV>60%vs. BIPAP/APRV0–30%). Conclusions: In a saline lung lavage model of experimental acute respiratory distress syndrome in pigs, levels of SB during BIPAP/APRV higher than currently recommended for clinical practice, that is, 10 to 30%, improve oxygenation by increasing aeration in dependent lung zones without relevant redistribution of perfusion. In presence of lung recruitment, higher levels of SB reduce global stress and strain despite an increase in inspiratory effort.