Periprosthetic infections: How do we diagnose and treat? Results of an online survey and comparison with international recommendations

Objective Endoprosthetic replacement surgery of hip and knee joints is widely performed, but always carries the risk of developing periprosthetic infection (PPI). Treatment of PPI is lengthy and demanding for the patient, often involving multiple surgeries as well as lengthy drug therapies. Remediation is not always successful despite extensive therapy. Methods An online survey was used to investigate whether the therapeutic measures implemented in German hospitals are based on international treatment recommendations. For this purpose, German physicians who regularly treat periprosthetic infections in their clinics were asked to complete an online questionnaire. The questionnaire asked about internal hospital procedures. These were then compared with international recommendations. Results With a response rate of 10.9%, the questionnaire shows agreement with the international recommendations in large parts of the operative and medicinal procedures. In preoperative imaging for example, two-plane radiographs are the standard. Similarly, the participants' approach to preoperative specimen collection, incubation time, and operative management (regarding one- or two-stage approach to septic joint) reflects the recommendations. Deviations were particularly evident in the area of laboratory diagnostics, where the erythrocyte sedimentation rate (ESR) is determined in only 17.1%, contrary to the recommendations. Whereas procalcitonin (PCT) and blood culture sampling takes place regularly. Clear differences emerges in the use of drains, which, contrary to the recommendations, are used very regularly (almost 70%). In this survey, the time intervals between the onset of infection symptoms and the start of therapy (prosthesis-preserving therapy) is shown to be longer than recommended internationally. Conclusion In summary, however, the recommended approaches of the international groups in most respects are followed, a high willingness of respondents to collaborate with local infectious disease specialists demonstrates the complexity of the disease

Virtual calcium-suppression in dual energy computed tomography predicts metabolic activity of focal MM lesions as determined by fluorodeoxyglucose positron-emission-tomography

Purpose: Recent studies showed that dual energy CT (DECT) allows for detection of bone marrow infiltration in multiple myeloma (MM) by obtaining virtual non-calcium (VNCa) images. This feasibility study investigated, if VNCa imaging might discriminate metabolically active, focal lesions in MM against avital lesions in MM patients, considering fluorodeoxyglucose positron-emission-tomography CT (FDG PET/CT) as the standard of reference. Method: The study included 60 osteolytic lesions in 10 consecutive low-dose whole body CT scans of patients with MM, who underwent both FDG PET/CT and DECT at a tertiary care university hospital. Circular ROI measurements were performed in predefined lesions on the monoenergetic CT (MECT) and VNCa images by three blinded radiologists. Each lesion was rated vital or avital by a blinded specialist of nuclear medicine, based on their FDG metabolism. Results: Each of the three readers could separate FDG PET/CT negative and positive MM lesions when analyzing the VNCa images, while MECT did not show a significant difference. Best results were yielded by high calcium suppression with excellent inter-rater reliability (average sensitivity 0.91, specificity 0.88, cutoff -46.9 HU), followed by medium and low calcium suppression. Conclusions: In contrast to MECT imaging, VNCa imaging in DECT appears to be feasible to assess metabolic activity of focal MM lesions as defined by the standard of reference, FDG PET/CT. Considering the higher cost and radiation exposure of FDG PET/CT, DECT VNCa imaging might develop to be the modality of choice to assess metabolic activity of focal MM lesions

Virtual monoenergetic images preserve diagnostic assessability in contrast media reduced abdominal spectral detector CT

Objectives: To investigate if low-keV virtual monoenergetic images (VMI4OkeV) from abdominal spectral detector CT (SDCT) with reduced intravenous contrast media application (RCM) provide abdominal assessment similar to conventional images with standard contrast media (SCM) dose. Methods: 78 patients with abdominal SDCT were retrospectively included: 41 patients at risk for adverse reactions who received 44 RCM examinations with 50 ml and 37 patients who underwent 44 SCM examinations with 100 ml of contrast media (CM) and who were matched for effective body diameters. RCM, SCM images and RCM VMI4OkeV were reconstructed. Attenuation and signal to noise ratio (SNR) of liver, pancreas, kidneys, lymph nodes, psoas muscle, aorta and portal vein were assessed ROIs-based. Contrast-to-noise ratios (CNR) of lymph nodes vs aorta/portal vein were calculated. Two readers evaluated organ/vessel contrast, lymph node delineation, image noise and overall assessability using 4-point Likert scales. Results: RCM were inferior to SCM images in all quantitative/qualitative criteria. RCM-VMI4OkeV and SCM images showed similar lymph node and muscle attenuation (p = 0.83,0.17), while for all other ROIs, RCM VMI4OkeV showed higher attenuation (p <= 0.05). SNR was comparable between RCM-VMI4OkeV and SCM images (p range: 0.23-0.99). CNR of lymph nodes was highest in RCM-VMI4OkeV (p <= 0.05). RCM-VMI4OkeV received equivalent or higher scores than SCM in all criteria except for organ contrast, overall assessability and image noise, where SCM were superior (p <= 0.05). However, RCM-VMI4OkeV received proper or excellent scores in 88.6/94.2/95.4% of the referring cases. Conclusions: VMI4OkeV counteract contrast deterioration in CM reduced abdominal SDCT, facilitating diagnostic assessment. Advances in knowledge: SDCT-derived VMI4OkeV provide adequate depiction of vessels, organs and lymph nodes even at notable CM reduction

Virtual monoenergetic images and post-processing algorithms effectively reduce CT artifacts from intracranial aneurysm treatment

To evaluate artifact reduction by virtual monoenergetic images (VMI) and metal artifact reduction algorithms (MAR) as well as the combination of both approaches (VMIMAR) compared to conventional CT images (CI) as standard of reference. In this retrospective study, 35 patients were included who underwent spectral-detector CT (SDCT) with additional MAR-reconstructions due to artifacts from coils or clips. CI, VMI, MAR and VMIMAR (range: 100-200keV, 10keV-increment) were reconstructed. Region-of-interest based objective analysis was performed by assessing mean and standard deviation of attenuation (HU) in hypo- and hyperdense artifacts from coils and clips. Visually, extent of artifact reduction and diagnostic assessment were rated. Compared to CI, VMI >= 100keV, MAR and VMIMAR between 100-200keV increased attenuation in hypoattenuating artifacts (CI/VMI200keV/MAR/VMIMAR200keV, HU: -77.6 +/- 81.1/-65.1 +/- 103.2/-36.9 +/- 27.7/-21.1 +/- 26.7) and decreased attenuation in hyperattenuating artifacts (HU: 47.4 +/- 32.3/42.1 +/- 50.2/29.5 +/- 18.9/20.8 +/- 25.8). However, differences were only significant for MAR in hypodense and VMIMAR in hypo- and hyperdense artifacts (p= 140/100keV, MAR and VMIMAR >= 100keV. Diagnostic assessment of surrounding brain tissue was significantly improved in VMI >= 100keV, MAR and VMIMAR >= 100keV. The combination of VMI and MAR facilitates a significant reduction of artifacts adjacent to intracranial coils and clips. Hence, if available, these techniques should be combined for optimal reduction of artifacts following intracranial aneurysm treatment

Lessons learned from applying a forest gap model to understand ecosystem and carbon dynamics of complex tropical forests

Forests worldwide are threatened by various environmental and anthropogenic hazards, especially tropical forests. Knowledge on the impacts of these hazards on forest structure and dynamics has been compiled in empirical studies. However, the results of these studies are often not sufficient for long-term projections and extrapolations to large spatial scales especially for unprecedented environmental conditions, which require both the identification and understanding of key underlying processes. Forest models bridge this gap by incorporating multiple ecological processes in a dynamic framework (i.e. including a realistic model structure) and addressing the complexity of forest ecosystems. Here, we describe the evolution of the individual-based and process-based forest gap model FORMIND and its application to tropical forests. At its core, the model includes physiological processes on tree level (photosynthesis, respiration, tree growth, mortality, regeneration, competition). During the past two decades, FORMIND has been used to address various scientific questions arising from different forest types by continuously extending the model structure. The model applications thus provided understanding in three main aspects: (1) the grouping of single tree species into plant functional types is a successful approach to reduce complexity in vegetation models, (2) structural realism was necessary to analyze impacts of natural and anthropogenic disturbances such as logging, fragmentation, or drought, and (3) complex ecological processes such as carbon fluxes in tropical forests – starting from the individual tree level up to the entire forest ecosystem – can be explored as a function of forest structure, species composition and disturbance regime. Overall, this review shows how the evolution of long-term modelling projects not only provides scientific understanding of forest ecosystems, but also provides benefits for ecological theory and empirical study design.peerReviewe

Simulating growth dynamics in a South-East Asian rain forest threatened by recruitment shortage and tree harvesting

There is increasing evidence that the futurerecruitment in South-East Asian dipterocarp treesspecies depending on mast-fruiting events mightbe endangered by climate change or enhancedseed predation in forest fragments. Especially incombination with the ongoing tree harvesting inthis region the recruitment threat imposes asevere danger on the species richness andforest structure of the whole area. We here assesswith the process-based forest growth modelFormind2.0 the impacts of common tree loggingstrategies in those recruitment endangered forests.Formind2.0 is based on the calculations of thecarbon balance of individual trees belonging to13 different plant functional types. Even singlelogging events in those rain forests threatenedby a lack of recruitment led to shifts in theabundances of species, to species loss, and toforest decline and dieback. The results show thatcurrent logging practices in South-East Asiaseriously overuse the forests especially in thelight of changing climate conditions