Search

Appropriate imaging is essential in the treatment of children and adolescents with rhabdomyosarcoma. For adequate stratification and optimal individualised local treatment utilising surgery and radiotherapy, high-quality imaging is crucial. The paediatric radiologist, therefore, is an essential member of the multi-disciplinary team providing clinical care and research. This manuscript presents the European rhabdomyosarcoma imaging guideline, based on the recently developed guideline of the European Paediatric Soft Tissue Sarcoma Study Group (EpSSG) Imaging Committee. This guideline was developed in collaboration between the EpSSG Imaging Committee, the Cooperative Weichteilsarkom Studiengruppe (CWS) Imaging Group, and the Oncology Task Force of the European Society of Paediatric Radiology (ESPR). MRI is recommended, at diagnosis and follow-up, for the evaluation of the primary tumour and its relationship to surrounding tissues, including assessment of neurovascular structures and loco-regional lymphadenopathy. Chest CT along with [F-18]2-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET)/CT or PET/MRI are recommended for the detection and evaluation of loco-regional and distant metastatic disease. Guidance on the estimation of treatment response, optimal long-term follow-up, technical imaging settings and standardised reporting are described. This European imaging guideline outlines the recommendations for imaging in children and adolescents with rhabdomyosarcoma, with the aim to harmonise imaging and to advance patient care. Supplementary Information The online version contains supplementary material available at 10.1007/s00247-021-05081-0.

Background and aims: Cerebral uptake of radioactive metabolites poses a major challenge for quantitative tracer kinetic PET studies. Although this uptake can be quantified by PET studies of the labelled metabolites themselves [1,2], it requires extensive chemistry and additional PET measurements, and is not feasible on a routine basis. Use of spectral analysis [3] has previously been suggested as a tool for assessing uptake of labelled metabolites of (R)-[11C]verapamil [4]. The aim of the present study was to investigate the potential use of multi-input spectral analysis (MISA) for assessment of metabolite uptake using simulations. In addition, the method was applied to clinical [18F]FDDNP and [11C]PIB data. Methods: MISA was implemented using 30 basis functions (BFs) based on tracer concentration in plasma, 30 BFs based on metabolite concentration in plasma, and one whole blood compartment, with time constants between 1/scan length and 1 min-1. Sets of 1000 noisy time-activity curves (TACs) were simulated, each set being based on different rate constants and plasma kinetic data with fast ([11C]PIB) or slow ((R)-[11C]verapamil) metabolism, with or without metabolite uptake. Volume of distribution (Vd), model order, and percent area under the curve due to metabolites (%AUCmet) were determined using MISA and compared to true values. TACs of 35 grey matter regions of interest (ROIs) of 10 subjects (5 [18F]FDDNP and 5 [11C]PIB) were analysed using MISA to identify possible metabolite uptake. Results: Using BFs based on [11C]PIB plasma kinetics, good correlation (r2 0.96) was found between %AUCmet obtained by MISA and true %AUCmet. MISA derived %AUCmet significantly > 0 always corresponded to a true metabolite compartment (figure 1). A metabolite compartment was consistently identified in clinical [18F]FDDNP time-activity curves, with mean ± SD %AUCmet of 29 ± 10 in 175 ROIs, compared to 22 ± 4 for [11C]PIB. According to the Akaike criterion, MISA consistently provided better fits than SA with only parent BFs in the case of [18F]FDDNP. Conclusions: Simulations indicate that a potential metabolite contribution can be identified accurately using MISA for tracers with fast metabolism. MISA applied to clinical data revealed likely metabolite uptake for [18F]FDDNP and [11C]PIB. Further validation of the method, using tracers for which metabolite kinetics have been measured such as [18F]altanserin [1], will be subject of future studies.

Introduction: Both [18F]FDDNP and [11C]PIB have been developed as PET tracers for imaging and quantifying beta-amyloid (As) fibril accumulation in Alzheimer's disease (AD) in vivo1,2. The purpose of the present study was to compare the potential value of [18F]FDDNP and [11C]PIB in the (early) diagnosis of AD by performing paired studies in the same patients. Methods: In this ongoing study, dynamic 90 minutes 3D [11C]PIB and [18F]FDDNP scans were acquired on the same day using an HR+ (Siemens) PET scanner. During both scans, continuous on-line and discrete manual sampling was performed to derive a metabolite corrected arterial plasma input curve. For each subject, volumes of interest (VOI) were defined on an individually acquired, co-registered T1 weighted structural MRI scan using an automated procedure3. Preliminary analysis of time-activity curves was performed using the simplified reference tissue model with cerebellum grey matter as reference tissue. Binding potential (BP) was used as outcome measure, in particular for areas previously associated with AD: frontal, parietal and temporal cortex. Results: At present, three AD patients, three patients with Mild Cognitive Impairment (MCI) and three age matched normal controls were included. Results are summarised in figures 1 and 2. [11C]PIB showed good contrast between AD patients and normal controls, as described previously1. In addition, the range of BP values in MCI patients was broader, probably due to the known heterogeneity of this group4. [18F]FDDNP provided less contrast between AD patients and normal controls. In AD patients, [11C]PIB BP was in general tenfold higher than [18F]FDDNP BP. Conclusion: The difference in BP between AD patients and normal controls appears to be more pronounced for [11C]PIB than for [18F]FDDNP. Further studies are needed to substantiate these preliminary findings.

Introduction: [11C]PIB is a ligand for imaging amyloid fibrils in brain. Price et al.[1] and Lopresti et al.[2] have evaluated Methods: for quantification of [11C]PIB studies, including performance of various parametric Methods:. The aim of the present study was to further investigate performance of parametric Methods: in which the reference tissue efflux rate (k2') is fixed to improve quantification. Performance of parametric Methods: was evaluated using simulations and clinical data. Methods: The following parametric Methods: were studied: RPM1[3], Reference Logan[4], MRTMo and MRTM[5]. In addition, RPM2[6], MRTM2[5] and two newly developed multi-linear Methods: (MRTM3 and MRTM4), with fixed k2', were included. Both simulations and clinical data were used to determine effects of flow (R1=0.6-0.9), fractional blood volume (Vb = 0.025-0.075) and binding potential (BP=0.2-3) on precision and accuracy of parametric BP and DVR. For simulations various [11C]PIB time activity curves (TACs) were generated at a 15% noise level using both reference tissue input (RI) and plasma input (PI). In addition, test-retest studies (two scans with arterial blood sampling on one day) were performed in 6 control and 5 AD subjects. TACs were derived from 8 regions of interest in the frontal cortex. Grey matter cerebellum was used as reference tissue. BP obtained with SRTM and DVR obtained with two-tissue reversible plasma-input model (2T-4k DVR) were used as reference. Results: RI simulations indicated that differences in bias between the various Methods: reduced with increasing BP (>0.2). Overall, lowest BP biases were observed for MRTM2 (

Objectives To compare WB-MRI with an [18F]FDG-PET/CT-based reference for early response assessment and restaging in children with Hodgkin’s lymphoma (HL). Methods Fifty-one children (ages 10–17) with HL were included in this prospective, multicentre study. All participants underwent WB-MRI and [18F]FDG-PET/CT at early response assessment. Thirteen of the 51 patients also underwent both WB-MRI and [18F]FDG-PET/CT at restaging. Two radiologists independently evaluated all WB-MR images in two separate readings: without and with DWI. The [18F]FDG-PET/CT examinations were evaluated by a nuclear medicine physician. An expert panel assessed all discrepancies between WB-MRI and [18F]FDG-PET/CT to derive the [18F]FDG-PET/CT-based reference standard. Inter-observer agreement for WB-MRI was calculated using kappa statistics. Concordance, PPV, NPV, sensitivity and specificity for a correct assessment of the response between WB-MRI and the reference standard were calculated for both nodal and extra-nodal disease presence and total response evaluation. Results Inter-observer agreement of WB-MRI including DWI between both readers was moderate (κ 0.46–0.60). For early response assessment, WB-MRI DWI agreed with the reference standard in 33/51 patients (65%, 95% CI 51–77%) versus 15/51 (29%, 95% CI 19–43%) for WB-MRI without DWI. For restaging, WB-MRI including DWI agreed with the reference standard in 9/13 patients (69%, 95% CI 42–87%) versus 5/13 patients (38%, 95% CI 18–64%) for WB-MRI without DWI. Conclusions The addition of DWI to the WB-MRI protocol in early response assessment and restaging of paediatric HL improved agreement with the [18F]FDG-PET/CT-based reference standard. However, WB-MRI remained discordant in 30% of the patients compared to standard imaging for assessing residual disease presence. Key Points • Inter-observer agreement of WB-MRI including DWI between both readers was moderate for (early) response assessment of paediatric Hodgkin’s lymphoma. • The addition of DWI to the WB-MRI protocol in early response assessment and restaging of paediatric Hodgkin’s lymphoma improved agreement with the [18F]FDG-PET/CT-based reference standard. • WB-MRI including DWI agreed with the reference standard in respectively 65% and 69% of the patients for early response assessment and restaging.