Meike Weis

Radiation Dose Comparison Between 70 kVp and 100 kVp With Spectral Beam Shaping for Non-Contrast-Enhanced Pediatric Chest Computed Tomography: A Prospective Randomized Controlled Study.

Objective The aim of this prospective randomized controlled study was to compare 2 techniques for radiation dose reduction in non–contrast-enhanced pediatric chest computed tomography (CT): low peak kilovoltage imaging at 70 kVp and spectral beam shaping at 100 kVp using a dedicated tin filter (100-kVp Sn). Materials and Methods All chest CT examinations were performed on a third-generation dual-source CT system (SOMATOM Force; Siemens Healthineers, Germany). Fifty children (mean age, 6.8 ± 5.1 years) were examined using the 100-kVp Sn protocol, whereas 25 children received the 70-kVp protocol (mean age, 5.7 ± 5.2 years; 2:1 randomization scheme). Radiation metrics and organ doses were compared between acquisition techniques using commercially available radiation dose analysis software (Radimetrics Inc, Bayer AG, Toronto, Ontario, Canada). Objective image quality, expressed by signal-to-noise ratio and subjective image quality based on a 4-point scale (1, best; 4, worst image quality), were compared. Results Volume CT dose index and size-specific dose estimate were significantly lower in the 100-kVp Sn group compared with the 70-kVp group (0.19 ± 0.12 mGy vs 0.81 ± 0.70 mGy and 0.34 ± 0.13 mGy vs 1.48 ± 1.11 mGy; P < 0.0001 for both). Accordingly, mean effective dose was significantly lower for the 100-kVp Sn examinations (0.21 ± 0.10 mSv) compared with the 70-kVp examinations (0.83 ± 0.49 mSv; P < 0.0001). Calculated organ doses were also significantly lower using the 100-kVp Sn protocol when compared with the 70-kVp protocol; for example, breast dose was reduced by a factor of 4.3. Signal-to-noise ratio was slightly superior for 70-kVp images while lung image quality of the 100-kVp Sn protocol was preferred in subjective analysis (P = 0.0004). Conclusions Pediatric chest CT performed at 100 kVp with an additional tin filter for spectral shaping significantly reduces radiation dose when compared with low peak kilovoltage imaging at 70 kVp and therefore should be preferred in non–contrast-enhanced pediatric chest CT examinations, particularly (given the improved subjective image quality) when the main focus is evaluation of the lung parenchyma.

Dual-energy snap-shot perfusion CT in suspect pulmonary nodules and masses and for lung cancer staging

Dual energy computed tomography (DECT) has proven its clinical usefulness for improved tissue characterization within the past years. In thoracic oncology, DECT can be used to differentiate between benign and malignant pulmonary nodules and masses. In patients with known lung cancer, DECT can add incremental functional information to staging scans, therapeutic response evaluation, as well as to the assessment of lung function. This review aims to give an overview on the current clinical utilities of DECT of the chest, its multiple post-processing applications and dose saving options. Furthermore, this review highlights promising applications of DECT that merit implementation in future clinical routine.

Quantitative Perfusionsbildgebung in der Magnetresonanztomographie

CLINICAL/METHODICAL ISSUE Magnetic resonance imaging (MRI) is recognized for its superior tissue contrast while being non-invasive and free of ionizing radiation. Due to the development of new scanner hardware and fast imaging techniques during the last decades, access to tissue and organ functions became possible. One of these functional imaging techniques is perfusion imaging with which tissue perfusion and capillary permeability can be determined from dynamic imaging data. STANDARD RADIOLOGICAL METHODS Perfusion imaging by MRI can be performed by two approaches, arterial spin labeling (ASL) and dynamic contrast-enhanced (DCE) MRI. While the first method uses magnetically labelled water protons in arterial blood as an endogenous tracer, the latter involves the injection of a contrast agent, usually gadolinium (Gd), as a tracer for calculating hemodynamic parameters. PERFORMANCE Studies have demonstrated the potential of perfusion MRI for diagnostics and also for therapy monitoring. ACHIEVEMENTS The utilization and application of perfusion MRI are still restricted to specialized centers, such as university hospitals. A broad application of the technique has not yet been implemented. PRACTICAL RECOMMENDATIONS The MRI perfusion technique is a valuable tool that might come broadly available after implementation of standards on European and international levels. Such efforts are being promoted by the respective professional bodies.ZusammenfassungKlinisches/methodisches ProblemDie Magnetresonanztomographie (MRT) zeichnet sich durch einen überlegenen Gewebekontrast aus, während sie nichtinvasiv und frei von ionisierender Strahlung ist. Sie bietet Zugang zu Gewebe- und Organfunktion. Eine dieser funktionellen bildgebenden Verfahren ist die Perfusionsbildgebung. Mit dieser Technik können u. a. Gewebeperfusion und Kapillarpermeabilität aus dynamischen Bilddaten bestimmt werden.Radiologische StandardverfahrenPerfusionsbildgebung mithilfe der MRT kann durch 2 Ansätze, nämlich „arterial spin labeling“ (ASL) und dynamische kontrastverstärkte (DCE-)MRT durchgeführt werden. Während die erste Methode magnetisch markierte Wasserprotonen im arteriellen Blut als endogenen Tracer verwendet, erfolgt bei der DCE-MRT eine Injektion eines Kontrastmittels, üblicherweise Gadolinium (Gd) als Tracer für die Berechnung hämodynamischer Parameter.LeistungsfähigkeitAus Studien werden das Potenzial und die Möglichkeiten der MRT-Perfusionsbildgebung deutlich, sei es in Bezug auf die Diagnostik oder aber auch zunehmend im Bereich des Therapiemonitorings.BewertungNutzung und Anwendung der MRT-Perfusionsbildgebung beschränken sich jedoch auf spezialisierte Zentren wie Universitätskliniken. Eine breite Anwendung der Technik ist bisher leider nicht erfolgt.Empfehlung für die PraxisDie MRT-Perfusionsbildgebung ist ein wertvolles Tool, das im Rahmen europäischer und internationaler Standardisierungsbemühungen für die Praxis zukünftig einsetzbar werden sollte.AbstractClinical/methodical issueMagnetic resonance imaging (MRI) is recognized for its superior tissue contrast while being non-invasive and free of ionizing radiation. Due to the development of new scanner hardware and fast imaging techniques during the last decades, access to tissue and organ functions became possible. One of these functional imaging techniques is perfusion imaging with which tissue perfusion and capillary permeability can be determined from dynamic imaging data.Standard radiological methodsPerfusion imaging by MRI can be performed by two approaches, arterial spin labeling (ASL) and dynamic contrast-enhanced (DCE) MRI. While the first method uses magnetically labelled water protons in arterial blood as an endogenous tracer, the latter involves the injection of a contrast agent, usually gadolinium (Gd), as a tracer for calculating hemodynamic parameters.PerformanceStudies have demonstrated the potential of perfusion MRI for diagnostics and also for therapy monitoring.AchievementsThe utilization and application of perfusion MRI are still restricted to specialized centers, such as university hospitals. A broad application of the technique has not yet been implemented.Practical recommendationsThe MRI perfusion technique is a valuable tool that might come broadly available after implementation of standards on European and international levels. Such efforts are being promoted by the respective professional bodies.

Separate Evaluation of the Ipsilateral and Contralateral MR Fetal Lung Volume in Patients With Congenital Diaphragmatic Hernia

OBJECTIVE Our study had two objectives. First, we separately evaluated observed-to-expected MR fetal lung volume (FLV) of lungs ipsilateral and contralateral to a congenital diaphragmatic hernia (CDH). Second, we compared the prognostic value of observed-to-expected MR FLV of the ipsilateral and contralateral lungs with that of observed-to-expected MR FLV of both lungs with respect to survival, need for extracorporeal membrane oxygenation (ECMO), and development of chronic lung disease (CLD). MATERIALS AND METHODS We evaluated observed-to-expected MR FLV of the lung ipsilateral to the diaphragmatic defect as well as in the contralateral lung in 107 fetuses with isolated CDH. ROC analysis and logistic regression analysis were performed to assess the prognostic value of the observed-to-expected MR FLV for association with outcome. RESULTS In all fetuses with CDH, values in the ipsilateral (mean observed-to-expected MR FLV ± SD, 9.4% ± 9.6%) and the contralateral lung (mean observed-to-expected MR FLV, 48.9% ± 18.5%; p < 0.0001) were significantly lower than values measured in healthy fetuses. Observed-to-expected MR FLV of both lungs and of the contralateral and ipsilateral lung revealed significant differences regarding survival (p < 0.0001, p < 0.0001, and p = 0.0170, respectively), need for ECMO (p < 0.0001, p < 0.0001, and p = 0.0051, respectively), and development of CLD (p = 0.0004, p = 0.0002, and p = 0.0460, respectively). Compared with the observed-to-expected MR FLV of both lungs, the observed-to-expected MR FLV of the contralateral lung showed a slightly higher prognostic accuracy regarding survival (AUC = 0.859 vs 0.825) and development of CLD (AUC = 0.734 vs 0.732) and a similar prognostic accuracy regarding need for ECMO (AUC = 0.805 vs 0.826). Observed-to-expected MR FLV of the ipsilateral lung did not show good prognostic value regarding survival (AUC = 0.617), need for ECMO (AUC = 0.673), and development of CLD (AUC = 0.636). These AUCs were significantly smaller than the AUCs resulting from the observed-to-expected MR FLV of both lungs (each p < 0.05) and considerably smaller than the AUCs of the observed-to-expected MR FLV of the contralateral lung (each p < 0.10). CONCLUSION Patients with CDH showed a substantially lower observed-to-expected MR FLV of both lungs compared with healthy fetuses. The observed-to-expected MR FLV of both lungs as well as of the lung contralateral to the CDH were reliable prenatal predictors of survival, need for ECMO, and development of CLD.

Lung Perfusion MRI After Congenital Diaphragmatic Hernia Repair in 2-Year-Old Children With and Without Extracorporeal Membrane Oxygenation Therapy

OBJECTIVE In severe cases of congenital diaphragmatic hernia (CDH), extracorporeal membrane oxygenation (ECMO) therapy improves survival. Later on, lung morbidity mainly defines development. The purpose of this study was to investigate whether 2-year-old children who need ECMO therapy after delivery have reduced perfusion MRI values as a sign of more severe lung hypoplasia than do children who do not need ECMO. MATERIALS AND METHODS After CDH repair, 38 children underwent dynamic contrast-enhanced MRI with a 3D time-resolved angiography with stochastic trajectories sequence. Fifteen (39%) of the children had received ECMO therapy in the neonatal period. Pulmonary blood flow (PBF), pulmonary blood volume (PBV), and mean transit time were calculated for both lungs. In addition, the ratio of ipsilateral to contralateral lung was calculated for all parameters. RESULTS In all children, those with and those without ECMO requirement, PBF and PBV were significantly reduced on the ipsilateral side (p < 0.05). Children who had received ECMO therapy had significantly reduced PBF and PBV values on the ipsilateral side (p < 0.05) compared with children who had not needed ECMO therapy. The ratios of ipsilateral to contralateral lung for PBF and PBV were also significantly reduced after ECMO. CONCLUSION Two-year-old children undergoing CDH repair who had needed neonatal ECMO had significantly reduced perfusion MRI values in the ipsilateral lung in comparison with children who had not needed ECMO. Perfusion MRI measurements are associated with the severity of lung hypoplasia and may therefore be helpful in follow-up investigations.

Ultra-high pitch chest computed tomography at 70 kVp tube voltage in an anthropomorphic pediatric phantom and non-sedated pediatric patients: Initial experience with 3rd generation dual-source CT

PURPOSE Minimizing radiation dose while at the same time preserving image quality is of particular importance in pediatric chest CT. Very recently, CT imaging with a tube voltage of 70 kVp has become clinically available. However, image noise is inversely proportional to the tube voltage. We aimed to investigate radiation dose and image quality of pediatric chest CT performed at 70 kVp in an anthropomorphic pediatric phantom as well as in clinical patients. METHODS AND MATERIALS An anthropomorphic pediatric phantom, which resembles a one-year-old child in physiognomy, was scanned on the 3rd generation dual-source CT (DSCT) system at 70 kVp and 80 kVp and a fixed ultra low tube-current of 8 mAs to solely evaluate the impact of lowering tube voltage. After the phantom measurements, 18 pediatric patients (mean 29.5 months; range 1-91 months; 21 examinations) underwent 3.2 high-pitch chest CT on the same DSCT system at 70 kVp tube voltage without any sedation. Radiation dose and presence of motion artifacts was compared to a retrospectively identified patient cohort examined at 80 kVp on a 16-slice single-source-CT (SSCT; n=15; 14/15 with sedation; mean 30.7 months; range 0-96 months; pitch=1.5) or on a 2nd generation DSCT without any sedation (n=6; mean 32.8 months; range 4-61 months; pitch=3.2). RESULTS Radiation dose in the phantom scans was reduced by approximately 40% when using a tube voltage of 70 kVp instead of 80 kVp. In the pediatric patient group examined at 70 kVp age-specific effective dose (ED; mean 0.5±0.2 mSv) was significantly lower when compared to the retrospective cohort scanned at 80 kVp on the 16-slice-SSCT (mean ED: 1.0±0.3 mSv; p<0.0001) and also considerably lower when compared to the cohort scanned at 80 kVp on the 2nd generation DSCT (mean ED: 0.9±0.5 mSv). None of the prospective, sedation-free CT examinations showed any motion artifacts whereas 13/15 examinations of the retrospective patient cohort scanned at 80 kVp with a pitch of 1.5 showed motion artifacts. CONCLUSION 3.2 high-pitch chest CT performed with 70 kVp significantly reduces radiation dose when compared to 80 kVp while at the same time provides good image quality without any motion artifacts even without sedation.

Region of interest-based versus whole-lung segmentation-based approach for MR lung perfusion quantification in 2-year-old children after congenital diaphragmatic hernia repair

ObjectiveWith a region of interest (ROI)-based approach 2-year-old children after congenital diaphragmatic hernia (CDH) show reduced MR lung perfusion values on the ipsilateral side compared to the contralateral. This study evaluates whether results can be reproduced by segmentation of whole-lung and whether there are differences between the ROI-based and whole-lung measurements.MethodsUsing dynamic contrast-enhanced (DCE) MRI, pulmonary blood flow (PBF), pulmonary blood volume (PBV) and mean transit time (MTT) were quantified in 30 children after CDH repair. Quantification results of an ROI-based (six cylindrical ROIs generated of five adjacent slices per lung-side) and a whole-lung segmentation approach were compared.ResultsIn both approaches PBF and PBV were significantly reduced on the ipsilateral side (p always <0.0001). In ipsilateral lungs, PBF of the ROI-based and the whole-lung segmentation-based approach was equal (p=0.50). In contralateral lungs, the ROI-based approach significantly overestimated PBF in comparison to the whole-lung segmentation approach by approximately 9.5 % (p=0.0013).ConclusionsMR lung perfusion in 2-year-old children after CDH is significantly reduced ipsilaterally. In the contralateral lung, the ROI-based approach significantly overestimates perfusion, which can be explained by exclusion of the most ventral parts of the lung. Therefore whole-lung segmentation should be preferred.Key Points• Ipsilaterally, absolute lung perfusion after CDH is reduced in whole-lung analysis.• Ipsilaterally, the ROI- and whole-lung-based approaches generate identical results.• Contralaterally, the ROI-based approach significantly overestimates perfusion results.• Whole lung should be analysed in MR lung perfusion imaging.• MR lung perfusion measurement is a radiation-free parameter of lung function.

Histogram based analysis of lung perfusion of children after congenital diaphragmatic hernia repair

OBJECTIVES To investigate a histogram based approach to characterize the distribution of perfusion in the whole left and right lung by descriptive statistics and to show how histograms could be used to visually explore perfusion defects in two year old children after Congenital Diaphragmatic Hernia (CDH) repair. METHODS 28 children (age of 24.2±1.7months; all left sided hernia; 9 after extracorporeal membrane oxygenation therapy) underwent quantitative DCE-MRI of the lung. Segmentations of left and right lung were manually drawn to mask the calculated pulmonary blood flow maps and then to derive histograms for each lung side. Individual and group wise analysis of histograms of left and right lung was performed. RESULTS Ipsilateral and contralateral lung show significant difference in shape and descriptive statistics derived from the histogram (Wilcoxon signed-rank test, p<0.05) on group wise and individual level. Subgroup analysis (patients with vs without ECMO therapy) showed no significant differences using histogram derived parameters. CONCLUSIONS Histogram analysis can be a valuable tool to characterize and visualize whole lung perfusion of children after CDH repair. It allows for several possibilities to analyze the data, either describing the perfusion differences between the right and left lung but also to explore and visualize localized perfusion patterns in the 3D lung volume. Subgroup analysis will be possible given sufficient sample sizes.

Isolated impact of liver herniation on outcome in fetuses with congenital diaphragmatic hernia – A matched-pair analysis based on fetal MRI relative lung volume

PURPOSE To evaluate liver-herniation as individual parameter on outcome in children with congenital diaphragmatic hernia. MATERIALS AND METHODS In a retrospective matched-pair analysis based on observed to expected fetal lung volume (o/e FLV), birth weight, gestational age at time-point of examination, status of tracheal occlusion therapy and side of the defect the individual impact of liver-herniation on survival, need for extracorporeal membrane oxygenation (ECMO) therapy and chronic lung disease (CLD) was investigated. In total 61 pairs (122 patients) were included. Fishers exact test was used to evaluate influence of liver-herniation and a p-value of <0.05 was defined as statistically significant. The study was approved by the local review board. RESULTS Children with liver-herniation have lower survival rates (78.7% vs. 95.1%; p = 0.0073), need ECMO-therapy more often (41.0% vs. 16.4%; p = 0.0027) and are more likely to develop CLD (71.7% vs. 37.9%; p = 0.0004) than their corresponding matched-pair without liver-herniation. CONCLUSION Liver-herniation itself and not further lung-volume restriction due to liver-herniation is responsible for poor outcome in CDH.

Color-coded visualization of magnetic resonance imaging multiparametric maps

Multiparametric magnetic resonance imaging (mpMRI) data are emergingly used in the clinic e.g. for the diagnosis of prostate cancer. In contrast to conventional MR imaging data, multiparametric data typically include functional measurements such as diffusion and perfusion imaging sequences. Conventionally, these measurements are visualized with a one-dimensional color scale, allowing only for one-dimensional information to be encoded. Yet, human perception places visual information in a three-dimensional color space. In theory, each dimension of this space can be utilized to encode visual information. We addressed this issue and developed a new method for tri-variate color-coded visualization of mpMRI data sets. We showed the usefulness of our method in a preclinical and in a clinical setting: In imaging data of a rat model of acute kidney injury, the method yielded characteristic visual patterns. In a clinical data set of N = 13 prostate cancer mpMRI data, we assessed diagnostic performance in a blinded study with N = 5 observers. Compared to conventional radiological evaluation, color-coded visualization was comparable in terms of positive and negative predictive values. Thus, we showed that human observers can successfully make use of the novel method. This method can be broadly applied to visualize different types of multivariate MRI data.