ABSTRACT
Background: positron Emission Tomography-Computed Tomography [PET-CT] is a useful hybrid imaging modality in the diagnosis of various malignancies. This modality imposes almost 20 mSv radiation dose to the patient. The purpose of the present study was to evaluate the uncertainties in calculated CT effective dose in TUBE CURRENT MODULATION-activated scans by Impact-Dose software
Materials and Methods: sixty total body DICOM [30 male and 30 female] whole body PET-CT images were selected. Volume CT Dose Index [CTDIvol] was recorded for each of the procedures. The image was divided into 5 regions of head and neck, chest, abdomen, pelvis and lower limbs according to special anatomical markers. Effective doses for total body and separate organs were calculated by means of Impact-Dose software once with global CTDIvol and once with a summation of doses calculated by 5 Regional CTDIvol and related scan ranges
Results: the difference among effective doses for some organs and total body were considerable. The mean and standard deviation [SD] of the coefficient of variations [CV%] for total body, breast, gonads, liver, lung, red bone marrow [RBM], thyroid, kidneys, and uterus were 12.56, 11.61, 9.44, 8.1, 11.31, 5.93, 8.61, 6.03 and 12.49, respectively. Uncertainties were higher for smaller patients by 19 noise indexes while these changes were higher for bigger patients and 22 noise indexes
Conclusion: the tube current variation depends on the acquisition and patient parameters. For measuring and reporting the total body and organs' effective doses in order to estimate the risks of CT's radiation for total body PET-CT procedures, the tube current variations must be considered
ABSTRACT
Noise in large cities is considered by the World Health Organization to be the third most hazardous type of pollution. Buses are an interesting object of study in the theme of noise pollution. They are at the same time a source of urban environmental [traffic] noise and occupational noise exposure source for drivers. The object of this study is Occupational noise exposure evaluation in drivers of bus transportation of Tehran city. Noise levels in 90 buses were sampled in three separate sub-sample including [1]30 Ikaroos buses [2]30 Man buses [3]30 Shahab buses, which were selected by simple random sampling. Noise exposure level was normalized to a nominal 8-h working day [LEX, 8h]. Simultaneous Octave Frequency Analysis were measured and sound intensity level [SIL] for bus drivers were calculated. Results, which are obtained from separate buses were compared together and too with standard levels. the normalized noise exposure levels [LEX, 8h] in Ikaroos bus drivers[82dB A] were higher than that of in Man bus drivers [77/6dB A] and this Values were higher than that of in Shahab bus drivers[75dB A].SIL values for Ikaroos bus drivers were higher than other that of other bus drivers. Results obtained of Frequency Analysis showed that age of buses in mid frequencies ws a meaningful on noise increase. Results showed that type and age of buses were effective factors in drivers' noise exposure levels [LEX, 8h], which was consistent with previous studies in this field