***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: Purpose The presence of contrast material s on computed tomography ( CT ) images can cause problems in the attenuation correction of positron emission tomography ( PET ) images . These are because of errors converting the CT attenuation of contrast to 511-keV attenuation and by the change in tissue enhancement over the duration of the PET emission scan . Newer CT-based attenuation correction ( CTAC ) algorithms have been developed to reduce these errors . Methods To evaluate the effectiveness of the modified CTAC technique , we performed a retrospective analysis on 20 patients , comparing PET images using unenhanced and contrast-enhanced CT scans for attenuation correction . A phantom study was performed to simulate the effects of contrast on radiotracer concentration measurements . Results There was a maximum difference in calculated radiotracer concentrations of 5.9 % within the retrospective data and 7 % within the phantom data . Conclusion Using a CTAC algorithm that de-emphasizes high-density areas , contrast-enhanced CT can be used for attenuation mapping without significant errors in quantitation Objectives The aim of this prospect i ve study was to assess the influence of different normalization procedures on relative changes in st and ardized uptake values ( SUV ) of 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography ( FDG-PET ) for the assessment of chemotherapy response in patients with colorectal carcinoma ( CRC ) and nonsmall cell lung carcinoma ( NSCLC ) . Methods In 97 patients with CRC ( n = 48 ) and NSCLC ( n = 49 ) , FDG-PET was performed before and during the course of chemotherapy .  Relative changes in SUV ( ΔSUV ) were determined after correction for injected dose and bodyweight , lean body mass , body surface area or a combination of bodyweight and plasma glucose . The predictive value for overall and progression-free survival with respect to the different normalized ΔSUVs was assessed . Results In both CRC and NSCLC , no differences were seen in the degree of change between the four SUV-normalizations during chemotherapy . Cox regression analysis for overall survival showed significant hazard ratios of 1.14–1.16 per 10 % SUV change in CRC and 1.10–1.13 in NSCLC and for progression-free survival hazard ratios of 1.15 per 10 % ΔSUV change in CRC and 1.10–1.12 in NSCLC . Conclusion Relative changes in SUV is a strong predictor for survival in both CRC and NSCLC . None of the four normalization methods showed statistical advantage over the other . Therefore , simplifying the methods for analysis of FDG-PET data can improve the incorporation of FDG-PET in clinical treatment – response monitoring and may facilitate application in multicentre trials UNLABELLED This study evaluated various quantitative criteria for analysis of breast imaging with PET using the radiolabeled glucose analog 18F-fluorodeoxyglucose ( FDG ) . METHODS In a prospect i ve study , 73 patients with abnormal mammography or palpable breast masses scheduled for biopsy were investigated with  PET .  A total of 97 breast tumors were evaluated by histology , including 46 benign and 51 malignant tumors . Using a whole-body PET scanner , attenuation-corrected images were acquired between 40 and 60 min after tracer injection . For Patlak analysis , dynamic data acquisition was obtained in 24 patients . To differentiate between benign and malignant breast tumors , receiver operating characteristic curves were calculated using incrementally increasing threshold values for tumor/ nontumor ratios based on average and maximum activity values per region of interest , st and ardized uptake values ( corrected for partial volume effect , normalized to blood glucose , partial volume effect and blood glucose , using the lean body mass as well as the body surface area ) and calculating the FDG influx rate ( K ) assessed by Patlak analysis . RESULTS Quantification of FDG uptake in breast tumors provided objective criteria for differentiation between benign and malignant tissue with similar diagnostic accuracy as compared with visual analysis . Applying correction for partial volume effect and normalization by blood glucose yielded the highest diagnostic accuracy . CONCLUSIONS These quantitative methods provided accurate evaluation of PET data for differentiating benign from malignant breast tumors . Quantitative assessment is recommended to complement visual image interpretation with the potential benefit of reduced interobserver variability UNLABELLED St and ardized uptake values ( SUVs ) are widely used to measure 18F-fluorodeoxyglucose ( FDG ) uptake in various tumors . It has been reported that normalization of FDG uptake for patient body weight ( SUVbw ) overestimates FDG uptake in heavy patients , as their fraction of body fat ( with low FDG uptake ) is often increased . The objective of this study was to determine if " normalization of FDG uptake for the body surface area " ( SUVbsa ) is independent of the patient 's body size and is more reliable than SUVbw . METHODS FDG-PET images were acquired on 44 patients ( body weight range : 45 - 115 kg ) with cancer .  SUVbw [ ( mCi/g of tissue)/(mCi injected/patient body weight in g ) ] and SUVbsa [ ( mCi/g of tissue)/(mCi injected/patient BSA in m2 ) ] were determined for the liver . Since most observers are accustomed to using the SUVbw , the two values were compared by setting the mean SUVbsa equal to that of SUVbw . RESULTS SUVbw and SUVbsa were 3.42 + /- 0.85 ( mean + /- s.d . ) and 3.42 + /- 0.60 , respectively . The st and ard deviation of the SUVbsa was smaller than that of SUVbw . More importantly , there was a strong positive correlation between SUVbw and , not only body weight ( r = 0.75 ) but also BSA ( r = 0.68 ) , whereas only a weak correlation between SUVbsa and body weight ( r = 0.41 ) or BSA ( r = 0.38 ) was found with a near flat regression line . CONCLUSION SUVbw overestimates FDG uptake in large patients . SUVbsa appears preferable to SUVbw , since it is minimally affected by the body size 18F-FDG PET is increasingly being used to monitor the early response of malignant tumors to chemotherapy . Underst and ing the reproducibility of st and ardized uptake values ( SUVs ) is an important prerequisite in estimating what constitutes a significant change . Methods : Twenty-six patients were studied on 2 separate occasions ( mean interval ± SD , 3 ± 2 d ; range , 1–5 d ) . A static PET/CT scan was performed 94 ± 9 min after the intravenous injection of 383 ± 15 MBq of 18F-FDG .  Mean and maximum SUVs ( SUVmean and SUVmax , respectively ) were determined for regions of interest drawn around the tumor on the first study and for the same regions of interest transferred to the second study . Results : SUVmean in tumors ranged from 1.49 to 17.48 and SUVmax ranged from 2.99 to 24.09 . The correlation between SUVmean determined on the 2 separate visits was 0.99 ; the mean difference between the 2 measurements was 0.01 ± 0.27 SUV . The 95 % confidence limits for the measurements were ±0.53 . For SUVmax , the mean difference was −0.05 ± 1.14 SUV . Conclusion : Our study demonstrates that repeated measurements of SUVmean performed a few days apart are highly reproducible . A decrease of 0.5 in the SUV is statistically significant Over the years several analytical methods have been proposed for the measurement of glucose metabolism using fluorine-18 fluorodeoxyglucose ( [18F]FDG ) and positron emission tomography ( PET ) . The purpose of this study was to evaluate which of these ( often simplified ) methods could potentially be used for clinical response monitoring studies in breast cancer . Prior to chemotherapy , dynamic [18F]FDG scans were performed in 20 women with locally advanced ( n=10 ) or metastasised ( n=10 ) breast cancer . Additional PET scans were acquired after 8 days ( n=8 ) , and after one , three and six courses of chemotherapy ( n=18 , 10 and 6 , respectively ) . Non-linear regression ( NLR ) with the st and ard two tissue compartment model was used as the gold st and ard for measurement of [18F]FDG uptake and was compared with the following methods : Patlak graphical analysis , simplified kinetic method ( SKM ) , SUV-based net influx constant ( " Sadato " method ) , st and ard uptake value [ normalised for weight , lean body mass ( LBM ) and body surface area ( BSA ) , with and without corrections for glucose ( g ) ] , tumour to non-tumour ratio ( TNT ) , 6P model and total lesion evaluation ( TLE ) . Correlation coefficients between each analytical method and NLR were calculated using multilevel analysis . In addition , for the most promising methods ( Patlak , SKM , SUVLBMg and SUVBSAg ) it was explored whether correlation with NLR changed with different time points after the start of therapy . Three methods showed excellent correlation ( r>0.95 ) with NLR for the baseline scan : Patlak10–60 and Patlak10–45 ( r=0.98 and 0.97 , respectively ) , SKM40–60 ( r=0.96 ) and SUVLBMg ( r=0.96 ) . Good correlation was found between NLR and SUV-based net influx constant , TLE and SUVBSAg ( 0.90<r<0.95 ) . The 6P model and TNT had the lowest correlation ( r≤0.84 ) . SUV was least accurate in predicting changes in [18F]FDG uptake over time during therapy . For all methods , correlation with NLR was significantly lower for bone metastases than for other ( primary or metastatic ) tumour lesions ( P<0.05 ) . In conclusion , three methods with different degrees of complexity appear to be promising alternatives to NLR for measuring glucose metabolism in breast cancer : Patlak , SKM and SUV ( normalised for LBM and with a correction for plasma glucose ) The aim of chemotherapy for mesothelioma is to palliate symptoms and improve survival . Measuring response using CT is challenging because of the circumferential tumor growth pattern . This study aims to evaluate the role of serial 18F-FDG PET in the assessment of response to  chemotherapy in patients with mesothelioma . Methods : Patients were prospect ively recruited and underwent both 18F-FDG PET and conventional radiological response assessment before and after 1 cycle of chemotherapy . Quantitative volume-based 18F-FDG PET analysis was performed to obtain the total glycolytic volume ( TGV ) of the tumor . Survival outcomes were measured . Results : Twenty-three patients were suitable for both radiological and 18F-FDG PET analysis , of whom 20 had CT measurable disease . After 1 cycle of chemotherapy , 7 patients attained a partial response and 13 had stable disease on CT assessment by modified RECIST ( Response Evaluation Criteria in Solid Tumors ) criteria . In the 7 patients with radiological partial response , the median TGV on quantitative PET analysis fell to 30 % of baseline ( range , 11%–71 % ) . After 1 cycle of chemotherapy , Cox regression analysis demonstrated a statistically significant relationship between a fall in TGV and improved patient survival ( P = 0.015 ) . Neither a reduction in the maximum st and ardized uptake value ( P = 0.097 ) nor CT ( P = 0.131 ) demonstrated a statistically significant association with patient survival . Conclusion : Semiquantitative 18F-FDG PET using the volume-based parameter of TGV is feasible in mesothelioma and may predict response to chemotherapy and patient survival after 1 cycle of treatment . Therefore , metabolic imaging has the potential to improve the care of patients receiving chemotherapy for mesothelioma by the early identification of responding patients . This technology may also be useful in the assessment of new systemic treatments for mesothelioma Objectives Peristalsis can lead to confusing FDG PET bowel uptake artefacts and potential for recording inaccurate mean st and ardised uptake value ( SUV ) measurements in PET-CT scans . Accordingly , we investigate the influence of different SUV normalisations on FDG PET uptake of the bowel and assess which one(s ) have least dependence on body size factors in patients with and without the introduction of the anti-peristalsis agent N-butylscopolamine ( Buscopan ) .  Methods This study consisted of 92 prospect i ve oncology patients , each having a whole body 18F-FDG PET scan .  Correlations were investigated between height , weight , glucose , body mass index ( bmi ) , lean body mass ( lbm ) and body surface area ( bsa ) with maximum and mean SUV recorded for bowel normalised to weight ( SUVw ) , lbm ( SUVlbm ) , bsa ( SUVbsa ) and blood glucose corrected versions ( SUVwg , SUVlbmg , SUVbsag ) . Results St and ardised uptake value normalisations were significantly different between control and Buscopan groups with less variability experienced within individual SUV normalisations by the administration of Buscopan .  Mean SUV normalisations accounted for 80 % of correlations in the control group and 100 % in the Buscopan group . Further , > 86 % of all correlations across both groups were dominated by mean SUV normalis 
    Output:
    
Scanner and reconstruction parameters can significantly affect SUV measurements .