***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background MRI is the diagnostic mainstay for detection and differentiation of musculoskeletal tumors . However , a projection regarding the biological dignity of lesions based on st and ard MRI sequences remains difficult and uncertain . This study was undertaken to analyse whether diffusion-weighted MRI ( DWI ) can distinguish between benign and malignant musculoskeletal tumorous and tumor-like lesions in pediatric patients . Methods MR examinations of 44 consecutive pediatric patients ( 26 girls , mean age 11±6 years ) including st and ard sequences and DWI ( b=50/800 s/mm2 ) at 1.5 or 3 Tesla were retrospectively evaluated . The study group contained 10 patients with non-treated malignant tumors and 34 patients with benign lesions . Size , relative signal intensity and apparent diffusion coefficient ( ADC , unit ×10−3 mm2/s ) were determined in one lesion per patient . Results Mean ADC was 0.78±0.45 × 10−3 mm2/s in patients with malignant tumors and 1.71±0.75 ×10−3 mm2/s in patients with benign lesions ( P<0.001 ) . Relative operating characteristics ( ROC ) analysis showed a sensitivity of 90 % and a specificity of 91 % for malignancy , based on an ADC cut-off value of ≤1.03 . On logistic regression , mean ADC and lesion size accounted for 62 % of variability in benign vs. malignant tumors . For malignant tumors , the signal intensity ratio was higher on DWI than on T1w post-contrast images ( P<0.002 ) . Two cases of local tumor recurrence were diagnosed by DWI only . Conclusions DWI shows promising results for determination of biological dignity in musculoskeletal tumors . Mean ADC ≤1.03 × 10−3 mm2/s is a strong indicator of malignancy at the first diagnosis . The use of DWI for early diagnosis of tumor recurrence in comparison with st and ard MRI sequences should be evaluated in prospect i ve studies PURPOSE To prospect ively assess whether there is a relationship between the apparent diffusion coefficient ( ADC ) and the histopathologic cell count and whether the ADC can enable differentiation of benign and malignant extracranial mass lesions in children . MATERIAL S AND METHODS Institutional ethics approval and parent or guardian consent were obtained . Eleven malignant and eight benign lesions in 19 children ( 11 girls , eight boys ; median age , 3.9 years ; age range , 11 days to 15.5 years ) who underwent magnetic resonance ( MR ) imaging of extracranial mass lesions-including a diffusion-weighted sequence ( with b values 0 , 500 , and 1000 sec/mm(2))- and histopathologic analysis to prove findings were studied . The median ADC within each mass lesion was compared with the median cell count for 10 high-power microscopic fields in the specimen . The inverse regression between cell count and ADC was calculated . The difference in ADC between benign and malignant lesions was assessed by using the Mann-Whitney U test . RESULTS There was an inverse relationship between ADC and cell count , expressed as ADC ( in x10(-3 ) mm(2)/sec ) = 0.56 + ( 66.2/cell count ) , with a relatively good fit to the observed data ( analysis of variance R(2 ) = 0.541 , F = 20.0 , P < .001 ) . The ADCs of benign lesions ranged from ( 0.84 - 2.83 ) x 10(-3 ) mm(2)/sec ( median , 1.35 x 10(-3 ) mm(2)/sec ; st and ard deviation , 0.68 ) . The ADCs of malignant lesions ranged from ( 0.73 - 1.53 ) x 10(-3 ) mm(2)/sec ( median , 1.00 x 10(-3 ) mm(2)/sec ; st and ard deviation , 0.29 ) . There was no significant difference in ADC between benign and malignant lesions ( Mann-Whitney U = 22 , P = .069 ) . All highly cellular ( > 150 cells per high-power field ) lesions had an ADC lower than 1.5 x 10(-3 ) mm(2)/sec . CONCLUSION Although there is a significant relationship between cellularity and ADC , cell count probably is not the sole determinant of the ADC . Use of the ADC can not enable accurate differentiation of malignant and benign lesions PURPOSE 18-fluorodeoxyglucose positron emission tomography ( PET ) is already an integral part of staging in rhabdomyosarcoma . We investigated whether primary -site treatment response characterized by serial PET imaging at specific time points can be correlated with local control . PATIENTS AND METHODS We retrospectively examined 94 patients with rhabdomyosarcoma who received initial chemotherapy 15 weeks ( median ) before radiotherapy and underwent baseline , preradiation , and postradiation PET .  Baseline PET st and ardized uptake values ( SUVmax ) and the presence or absence of abnormal uptake ( termed PET-positive or PET-negative ) both before and after radiation were examined for the primary site . Local relapse-free survival ( LRFS ) was calculated according to baseline SUVmax , PET-positive status , and PET-negative status by the Kaplan-Meier method , and comparisons were tested with the log-rank test . RESULTS The median patient age was 11 years . With 3-year median follow-up , LRFS was improved among postradiation PET-negative vs PET-positive patients : 94 % vs 75 % , P=.02 . By contrast , on baseline PET , LRFS was not significantly different for primary -site SUVmax≤7 vs > 7 ( median ) , although the findings suggested a trend toward improved LRFS : 96 % for SUVmax≤7 vs 79 % for SUVmax>7 , P=.08 . Preradiation PET also suggested a statistically insignificant trend toward improved LRFS for PET-negative ( 97 % ) vs PET-positive ( 81 % ) patients ( P=.06 ) . CONCLUSION Negative postradiation PET predicted improved LRFS . Notably , 77 % of patients with persistent postradiation uptake did not experience local failure , suggesting that these patients could be closely followed up rather than immediately referred for intervention . Negative baseline and preradiation PET findings suggested statistically insignificant trends toward improved LRFS . Additional study may further underst and ing of relationships between PET findings at these time points and outcome in rhabdomyosarcoma The purpose of this retrospective study was to evaluate the role of 18F-FDG PET or PET/CT in the prediction of patient outcome in children and young adults affected by rhabdomyosarcoma . Methods : Forty-one patients with histology-proven rhabdomyosarcoma who underwent PET or PET/CT were identified ( age range , 1–20 y ; mean age ± SD , 9.9 ± 5.8 y ) . Tumor maximum st and ardized uptake value ( SUVmax ) and visually rated metabolic activity , as well as the presence of metabolically active lymph nodes and distant metastases , were compared with event-free and overall survival . Multivariate Cox regression analyses were performed to compare the prediction of outcome according to metabolic tumor intensity in relation to established prognostic factors . Results : Kaplan – Meier analyses revealed a significantly shorter overall survival in primary tumors visually rated as highly metabolically active or with a ratio of SUVmax to SUV of the liver above 4.6 . In addition , metabolically active lymph node and distant site involvement was indicative of significantly lower survival rates . On multivariate Cox regression analysis , the impact of intensity or SUVmax of the primary tumor on outcome failed to attain significance , although PET performed better than some of the prognostic factors established in larger patient groups ( P = 0.081 ) . Conclusion : 18F-FDG PET/CT is a valuable tool for initial staging in children affected by rhabdomyosarcoma . 18F-FDG PET/CT may be an additional predictor of outcome and may be used to refine risk-adapted therapy . PET performed better than some established risk factors . The borderline significance level of primary tumor metabolism in multivariate testing may be an effect of the limited sample size . Further prospect i ve evaluations are warranted Background Complete staging of rhabdomyosarcoma is critical to deliver appropriate therapy . We evaluated the role of 18F-fluorodeoxyglucose positron emission tomography ( PET ) in the staging of patients with rhabdomyosarcoma . Methods Twenty-four patients with rhabdomyosarcoma had a PET scan  during staging evaluation , before or within 13 days of initiation of therapy . PET was compared with computed tomography ( CT ) , magnetic resonance imaging ( MRI ) , bone scan , and pathology . Results Ninety-six sites were evaluated . All patients had positive PET scans at the primary site . Thirty-one PET positive sites at primary , regional , or distant sites were biopsied . Pathology in all 31 confirmed disease . St and ardized uptake value for the primary site at diagnosis ranged from 2.4 to 12.7 ( mean 6.4 ) . At 23 sites , CT or MRI was equivocal for the detection of regional or distant spread . In these cases , a negative PET helped to exclude disease in 21 of 23 patients . PET failed to capture sites of disease visualized by CT , MRI , or bone scan at 10 sites . When comparing PET with the final clinical determination of disease extent , PET was 77 % sensitive and 95 % specific . Conclusions These preliminary data indicate that PET is a useful adjunct in staging rhabdomyosarcoma . A prospect i ve study of PET for staging of rhabdomyosarcoma is warranted PURPOSE The objective of this study was to evaluate the impact of positron emission tomography ( PET ) using fluorine-18-fluorodeoxyglucose ( FDG ) for initial staging and therapy planning in pediatric sarcoma patients . PATIENTS AND METHODS In this prospect i ve multicenter study , 46 pediatric patients ( females , n = 22 ; males , n = 24 ; age range , 1 to 18 years ) with histologically proven sarcoma ( Ewing sarcoma family tumors , n = 23 ; osteosarcoma , n = 11 ; rhabdomyosarcoma , n = 12 ) were examined with conventional imaging modalities ( CIMs ) , including ultrasound , computed tomography ( CT ) , magnetic resonance imaging , and bone scintigraphy according to the st and ardized algorithms of the international therapy optimization trials , and whole-body FDG-PET . A lesion- and patient-based analysis of PET alone and CIMs alone and a side-by-side ( SBS ) analysis of FDG-PET and CIMs were performed . The st and ard of reference consisted of all imaging material , follow-up data ( mean follow-up time , 24 + /- 12 months ) , and histopathology and was determined by an interdisciplinary tumor board . RESULTS FDG-PET and CIMs were equally effective in the detection of primary tumors ( accuracy , 100 % ) . PET was superior to CIMs concerning the correct detection of lymph node involvement ( sensitivity , 95 % v 25 % , respectively ) and bone manifestations ( sensitivity , 90 % v 57 % , respectively ) , whereas CT was more reliable than FDG-PET in depicting lung metastases ( sensitivity , 100 % v 25 % , respectively ) . The patient-based analysis revealed the best results for SBS , with 91 % correct therapy decisions . This was significantly superior to CIMs ( 59 % ; P < .001 ) . CONCLUSION In staging pediatric sarcoma , subsidiary FDG-PET scanning depicts important additional information and has a relevant impact on therapy planning when analyzed side-by-side with CIMs 
    Output:
    
Limited evidence indicated initial PET-CT results were predictive of survival  .
Limited data were found on outcome prediction by PET-CT response .
DISSEMINATION AND ETHICS PET/PET-CT may increase initial staging accuracy in paediatric RMS , specifically in the detection of nodal involvement and distant metastatic spread .