In this study we examined the correlation between the extent of thoracic lymphatic anomalies in patients after surgical palliation by total cavopulmonary connection (TCPC) and their outcome in terms ...of clinical and laboratory parameters.
We prospectively examined 33 patients after TCPC with an isotropic heavily T2-weighted MRI sequence on a 3.0 T scanner. Examinations were performed after a solid meal, slice thickness of 0.6 mm, TR of 2400 ms, TE of 692 ms, FoV of 460 mm, covering thoracic and abdominal regions. Findings of the lymphatic system were correlated with clinical and laboratory parameters obtained at the annual routine check-up.
Eight patients (group 1) showed type 4 lymphatic abnormalities. Twentyfive patients (group 2) presented less severe anomalies (type 1-3). In the treadmill CPET, group 2 reached step 7.0;6.0/8.0 vs. 6.0;3.5/6.8 in group 1 (
= 0.006*) and a distance of 775;638/854 m vs. 513;315/661 m (
= 0.006*). In the laboratory examinations, group 2 showed significantly lower levels of AST, ALT and stool calprotectin as compared to group 1. There were no significant differences in NT-pro-BNP, total protein, IgG, lymphocytes or platelets, but trends. A history of ascites showed 5/8 patients in group 1 vs. 4/25 patients in group 2 (
= 0.02*), PLE occurred in 4/8 patient in group 1 vs. 1/25 patients in group 2 (
= 0.008*).
In the long-term follow-up after TCPC, patients with severe thoracic and cervical lymphatic abnormalities showed restrictions in exercise capacity, higher liver enzymes and an increased rate of symptoms of imminent Fontan-failure such as ascites and PLE.
Background
Newborns and small infants have shallow breathing.
Objective
To suggest criteria for when respiratory gating is necessary during cardiac MRI in newborns and infants.
Materials and methods
...One-hundred ten data sets of newborns and infants with (
n
= 92, mean age: 1.9 ± 1.7 SD years) and without (
n
= 18, mean age: 1.6 ± 1.8 SD years) navigator gating were analysed retrospectively. The respiratory motion of the right hemidiaphragm was recorded and correlated to age, weight, body surface area and qualitative image quality on a 4-point score. Quantitative image quality assessment was performed (sharpness of the delineation of the ventricular septal wall) as well as a matched-pair comparison between navigator-gated and non-gated data sets.
Results
No significant differences were found in overall image quality or in the sharpness of the ventricular septal wall between gated and non-gated scans. A navigator acceptance of >80% was frequently found in patients ages <12 months, body surface area <0.40 m
2
, body weight <10 kg and a size of <80 cm.
Conclusion
Sequences without respiratory gating may be used in newborns and small infants, in particular if age <12 months, body surface area <0.40 m
2
, body weight <10 kg and height <80 cm.
Traditionally, tropospheric radical chemistry is discussed in terms of the daytime photochemically produced hydroxyl radical (OH). Radicals, however, are also important during nighttime: this is ...especially true for ozone and the nitrate radical (NO3), which both act as key initiators of the degradation of alkenes such as biogenic monoterpenes. These reactions lead to the formation of peroxy radicals (HO2 and RO2) and hydroxyl radicals at night. We present recent observations of nighttime concentrations of NO3, RO2, HO2, and OH by differential optical absorption spectroscopy (DOAS), matrix isolation electron spin resonance (MIESR), laser‐induced fluorescence (LIF), and a chemical amplifier (CA) in the framework of the Berliner Ozonexperiment (BERLIOZ) campaign at Pabstthum, Germany, together with modeling studies of nocturnal radical chemistry. Modeled RO2 mixing ratios reached 40 ppt while the measured ROx level went up to 22 ppt at the same time. Modeled and measured HO2 mixing ratios were up to 6 and 4 ppt, respectively. In the case of OH, a nocturnal concentration of (1.85 ± 0.82) × 105 cm−3 was measured during one night. At this time, the model yielded an OH level of (4.1 ± 0.7) × 105 cm−3. This overestimation by the model could point to a missing nocturnal sink of OH. Nitrate radical reactions with terpenes were found responsible for producing 77% of the RO2 radicals, 53% of the HO2, and 36% of the OH radicals during night. Nighttime ozonolysis formed 12% of the RO2, 47% of the HO2, and 64% of the OH radicals. Another 11% of the RO2 radicals were formed by OH–volatile organic compound (VOC) reactions. A positive linear correlation of RO2 and NO3 was observed and could be reproduced in model calculations originating from the loss of both radicals by reaction with NO and the NO3‐initiated RO2 production. The contribution of nighttime OH to the atmosphere's oxidation capacity (oxidation rate of VOCs, CO, and CH4) was found negligible (<0.5%).
Background
The SIOP‐Renal Tumor Study Group (RTSG) does not advocate invasive procedures to determine histology before the start of therapy. This may induce misdiagnosis‐based treatment initiation, ...but only for a relatively small percentage of approximately 10% of non‐Wilms tumors (non‐WTs). MRI could be useful for reducing misdiagnosis, but there is no global consensus on differentiating characteristics.
Purpose
To identify MRI characteristics that may be used for discrimination of newly diagnosed pediatric renal tumors.
Study Type
Consensus process using a Delphi method.
Population
Not applicable.
Field Strength/Sequence
Abdominal MRI including T1‐ and T2‐weighted imaging, contrast‐enhanced MRI, and diffusion‐weighted imaging at 1.5 or 3 T.
Assessment
Twenty‐three radiologists from the SIOP‐RTSG radiology panel with ≥5 years of experience in MRI of pediatric renal tumors and/or who had assessed ≥50 MRI scans of pediatric renal tumors in the past 5 years identified potentially discriminatory characteristics in the first questionnaire. These characteristics were scored in the subsequent second round, consisting of 5‐point Likert scales, ranking‐ and multiple choice questions.
Statistical Tests
The cut‐off value for consensus and agreement among the majority was ≥75% and ≥60%, respectively, with a median of ≥4 on the Likert scale.
Results
Consensus on specific characteristics mainly concerned the discrimination between WTs and non‐WTs, and WTs and nephrogenic rest(s) (NR)/nephroblastomatosis. The presence of bilateral lesions (75.0%) and NR/nephroblastomatosis (65.0%) were MRI characteristics indicated as specific for the diagnosis of a WT, and 91.3% of the participants agreed that MRI is useful to distinguish NR/nephroblastomatosis from WT. Furthermore, all participants agreed that age influenced their prediction in the discrimination of pediatric renal tumors.
Data Conclusion
Although the discrimination of pediatric renal tumors based on MRI remains challenging, this study identified some specific characteristics for tumor subtypes, based on the shared opinion of experts. These results may guide future validation studies and innovative efforts.
Level of Evidence: 3
Technical Efficacy Stage: 3
Abstract Background Magnetic resonance imaging (MRI) and/or scintigraphy are commonly used for follow-up in children after treatment of acute osteomyelitis. Regularly, post-treatment imaging reveals ...pathological findings even if serum inflammatory parameters and clinical presentation are normal. We analyzed combined positron emission tomography and multislice computed tomography (PET/CT) for this condition. Methods Six children received PET/CT after treatment of acute osteomyelitis. Post-treatment MRI had revealed suspicious residual and/or additional findings. All patients had physiological serum infection parameters and no clinical symptoms. Results Median patient age was 59.5 months (range, 48-156). No increased 18-Fluor-2-deoxy-D-glucose uptake was observed in 3 patients. In 3 patients, there was minimal activity at the site of infection, which, however, did not reach the presumed range of osteomyelitis. All children were taken off antibiotic medication. No clinical symptoms reoccurred in any of them, and repeatedly controlled serum infection parameters were all normal. Median follow-up was 33 months (range, 4-65). Conclusions The PET/CT was superior to MRI in distinguishing between infection and reparative activity within the musculoskeletal system in selected children after acute osteomyelitis. The termination of antibiotic treatment for children after acute osteomyelitis seems justified when laboratory parameters as well as clinical presentation are normal, and PET/CT scan is unsuspicious.
A novel MS/MS-based analysis strategy using isotopomer labels, referred to as “tandem mass tags” (TMTs), for the accurate quantification of peptides and proteins is described. The new tags are ...designed to ensure that identical peptides labeled with different TMTs exactly comigrate in all separations. The tags require novel methods of quantification analysis using tandem mass spectrometry. The new tags and analysis methods allow peptides from different samples to be identified by their relative abundance with greater ease and accuracy than other methods. The new TMTs permit simultaneous determination of both the identity and relative abundances of peptide pairs using a collision induced dissociation (CID)-based analysis method. Relative abundance measurements made in the MS/MS mode using the new tags are accurate and sensitive. Compared to MS-mode measurements, a very high signal-to-noise ratio is achieved with MS/MS based detection. The new tags should be applicable to a wide variety of peptide isolation methods.
Optimization of tracer dose regimes in positron emission tomography (PET) imaging is a trade-off between diagnostic image quality and radiation exposure. The challenge lies in defining minimal tracer ...doses that still result in sufficient diagnostic image quality. In order to find such minimal doses, it would be useful to simulate tracer dose reduction as this would enable to study the effects of tracer dose reduction on image quality in single patients without repeated injections of different amounts of tracer. The aim of our study was to introduce and validate a method for simulation of low-dose PET images enabling direct comparison of different tracer doses in single patients and under constant influencing factors.
(18)F-fluoride PET data were acquired on a combined PET/magnetic resonance imaging (MRI) scanner. PET data were stored together with the temporal information of the occurrence of single events (list-mode format). A predefined proportion of PET events were then randomly deleted resulting in undersampled PET data. These data sets were subsequently reconstructed resulting in simulated low-dose PET images (retrospective undersampling of list-mode data). This approach was validated in phantom experiments by visual inspection and by comparison of PET quality metrics contrast recovery coefficient (CRC), background-variability (BV) and signal-to-noise ratio (SNR) of measured and simulated PET images for different activity concentrations. In addition, reduced-dose PET images of a clinical (18)F-FDG PET dataset were simulated using the proposed approach.
(18)F-PET image quality degraded with decreasing activity concentrations with comparable visual image characteristics in measured and in corresponding simulated PET images. This result was confirmed by quantification of image quality metrics. CRC, SNR and BV showed concordant behavior with decreasing activity concentrations for measured and for corresponding simulated PET images. Simulation of dose-reduced datasets based on clinical (18)F-FDG PET data demonstrated the clinical applicability of the proposed data.
Simulation of PET tracer dose reduction is possible with retrospective undersampling of list-mode data. Resulting simulated low-dose images have equivalent characteristics with PET images actually measured at lower doses and can be used to derive optimal tracer dose regimes.
OBJECTIVEThe aim of this study was to evaluate the clinical applicability and technical feasibility of fluorodeoxyglucose (FDG) positron emission tomography (PET)/magnetic resonance imaging (MRI) ...compared with FDG PET/computed tomography (CT) in young children focusing on lesion detection, PET quantification, and potential savings in radiation exposure.
METHODSTwenty examinations (10 PET/CT and 10 PET/MRI examinations) were performed prospectively in 9 patients with solid tumors (3 female, 6 male; mean age, 4.8 1–6 years). Fluorodeoxyglucose PET/CT and FDG PET/MRI were performed sequentially after a single tracer injection. Lesion detection and analysis were performed independently in PET/CT and PET/MRI. Potential changes in diagnostic or therapeutic patient management were recorded. Positron emission tomography quantification in PET/MRI was evaluated by comparing standardized uptake values resulting from MRI-based and CT-based attenuation correction. Effective radiation doses of PET and CT were estimated.
RESULTSTwenty-one PET-positive lesions were found congruently in PET/CT and PET/MRI. Magnetic resonance imaging enabled significantly better detection of morphologic PET correlates compared with CT. Eight suspicious PET-negative lesions were identified by MRI, of which one was missed in CT. Sensitivity, specificity, and accuracy for correct lesion classification were not significantly different (90%, 47%, and 62% in PET/CT; 100%, 68%, and 79% in PET/MRI, respectively). In 4 patients, the use of PET/MRI resulted in a potential change in diagnostic management compared with PET/CT, as local and whole-body staging could be performed within 1 single examination. In 1 patient, PET/MRI initiated a change in therapeutic management. Positron emission tomography quantification using MRI-based attenuation correction was accurate compared with CT-based attenuation correction. Higher standardized uptake value deviations of about 18% were observed in the lungs due to misclassification in MRI-based attenuation maps. Potential reduction in radiation dose was 48% in PET/MRI compared with PET/CT (P < 0.05).
CONCLUSIONSFDG PET/MRI is at least equivalent to FDG PET/CT for oncologic imaging in young children. Specifically, superior soft tissue contrast of MRI results in higher confidence in lesion interpretation. Substantial savings in radiation exposure can be achieved, and the number of necessary imaging examinations can be reduced using PET/MRI compared with PET/CT.
This paper presents the measurements of OH and HO2 radical concentrations as well as photolysis frequencies of different molecules during the Berliner Ozone (BERLIOZ) field experiment in July/August ...1998 at the rural site Pabstthum about 50 km NW of Berlin. Radical concentrations were measured using laser‐induced fluorescence (LIF) spectroscopy, while filter radiometers and a scanning spectroradiometer were used to obtain photolysis frequencies. The radical data set covers the time period from 20 July to 6 August and consists of more than 6000 simultaneous measurements of OH and HO2 with a typical time resolution of about 90 s. The maximum OH and HO2 daytime concentrations were 8 × 106 and 8 × 108 cm−3, respectively. While nighttime values of OH were usually below the detection limit of our instrument (3.5 × 105 cm−3), HO2 did show significant concentrations throughout most of the nights (on average 3 × 107 cm−3). The OH concentration was mainly controlled by solar UV radiation and showed a high linear correlation with J(O1D). A deviation from this general behavior was observed around dawn and dusk, when OH concentrations well above the detection limit were observed, although J(O1D) was essentially zero. A comparison with data sets from previous campaigns revealed that even though the linear correlation is found in other environments as well the slope OH/J(O1D) differs significantly. The diurnal cycles of HO2 were less dependent on the solar actinic flux but were predominantly influenced by NO. During episodes of high NO, HO2 remained below the detection limit (1 × 107 cm−3) but started to rise rapidly as soon as NO started to decrease.
Object
To assess lung perfusion in young patients with cystic fibrosis (CF) using an arterial spin labeling (ASL) technique.
Materials and methods
Perfusion imaging was performed in 5 healthy ...volunteers and 33 pediatric patients (13 ± 5 years) with CF using an ASL technique. Image quality was evaluated on a five-point scale (1 = excellent). Quantitative perfusion maps were calculated based on the modified Bloch equations. Perfusion differences between volunteers and CF patients and regional differences between lobes were analyzed using Student’s
t
test. The association of perfusion values and forced expiratory volume in 1 s (FEV1) was analyzed using univariate regression analysis.
Results
Mean lung perfusion was 698 ± 67 ml/100g/min (range: 593–777 ml/100g/min) in volunteers and 526 ± 113 ml/100g/min (range: 346–724 ml/100g/min) in CF patients. Median image quality was 2 in volunteers and 3 in CF patients. In CF patients, significantly lower perfusion was observed in the upper lobes compared to healthy volunteers. Mean perfusion values significantly correlated with FEV1 (
r
= 0.84,
P
< 0.0001).
Conclusion
ASL perfusion imaging provides lung perfusion assessment in young CF patients. This non-invasive functional imaging technique is worth being evaluated in the clinical monitoring of CF patients.
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