Abstract1,3-Butadiene (BD) is a petrochemical manufactured in high volumes. It is a human carcinogen and can induce lymphohematopoietic cancers, particularly leukemia, in occupationally-exposed workers. BD is an air pollutant with the major environmental sources being automobile exhaust and tobacco smoke. It is one of the major constituents and is considered the most carcinogenic compound in cigarette smoke. The BD concentrations in urban areas usually vary between 0.01 and 3.3 μg/m3 but can be significantly higher in some microenvironments. For BD exposure of the general population, microenvironments, particularly indoor microenvironments, are the primary determinant and environmental tobacco smoke is the main contributor. BD has high cancer risk and has been ranked the second or the third in the environmental pollutants monitored in most urban areas, with the cancer risks exceeding 10-5. Mutagenicity/carcinogenicity of BD is mediated by its genotoxic metabolites but the specific metabolite(s) responsible for the effects in humans have not been determined. BD can be bioactivated to yield three mutagenic epoxide metabolites by cytochrome P450 enzymes, or potentially be biotransformed into a mutagenic chlorohydrin by myeloperoxidase, a peroxidase almost specifically present in neutrophils and monocytes. Several urinary BD biomarkers have been developed, among which N-acetyl-S-(4-hydroxy-2-buten-1-yl)-L-cysteine is the most sensitive and is suitable for biomonitoring BD exposure in the general population. Exposure to BD has been associated with leukemia, cardiovascular disease, and possibly reproductive effects, and may be associated with several cancers, autism, and asthma in children. Collectively, BD is a ubiquitous pollutant that has been associated with a range of adverse health effects and diseases with children being a subpopulation with potentially greater susceptibility. Its adverse effects on human health may have been underestimated and more studies are needed.

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PurposeTo explore the effect of half 18F-FDG dose on image quality of pediatric oncological patients using total-body PET/CT. and investigate the ultra-low dose of administered tracer activity. Methods100 pediatric oncological patients who underwent total-body PET/CT using the uEXPLORER scanner with half 18F-FDG dose (1.85 MBq/kg) were retrospectively enrolled. The PET images were firstly reconstructed using all the 600s data, and then split into 300s, 180s, 60s, 40s and 20s duration groups. The subjective analysis method was assessed using a 5-point Likert scales. Objective quantitative metrics included the maximum standard uptake value (SUVmax), SUVmean, standard deviation (SD), signal to noise ratio (SNR) and SNRnorm of the backgrounds. The variability in lesion SUVmean, SUVmax, and tumor-to-background ratio (TBR) were also calculated. ResultsThe overall image quality scores in Group 600s, 300s, 180s and 60s were 4.9 ± 0.2, 4.9 ± 0.3, 4.4±0.5 and 3.5±0.5 respectively. All the lesions identified in half-dose images were localised down to G60s (1/20-dose) images; while 56% of the lesion could be clearly identified in G20s (1/60-dose) images. With stimulated reduced doses, SUVmax and SD of backgrounds were gradually increased, while TBR values showed no statistically significant deviation among all the groups (all p > 0.1). Using the half-dose images as reference, the variability of lesion SUVmax gradually increased from G180s to G20s, while lesion SUVmean remained stable for all the age groups. SNRnorm was highly correlated with the age in a negative direction.ConclusionsThe total-body PET/CT with half 18F-FDG dose achieved good performance in pediatric patients considering the sufficient image quality and lesion conspicuity. Sufficient image quality and lesion conspicuity could be maintained with an administered dose reduced down to 1/20-dose (0.185 MBq/kg, , estimated effective dose: 0.18–0.26 mSv).