ABSTRACT
Objective To evaluate the secondary cancer risk to various organs due to radiation treatment for early left-sided breast cancer using 6 MV X-ray flattening filter free (FFF) and flattening filter (FF) modes.Methods Two techniques,6 MV FFF and 6 MV FF X-rays modes,were used to develop the two tangential fields d-IMRT plans for 20 early left-sided breast cancer patients respectively.For all the patients,the dose to surrounding tissues was minimized as low as possible,the 95％ volume of the planning target volume (PTV) and clinical target volume (CTV) was consistent with the prescribed dose.The beam parameters and the plan optimization parameters of FFF modes were in consonance with FF modes.The radiation doses and volumes of the planning target volumes,organs at risk and normal tissue were detected by dose-volume histogram.And then,the excess absolute risk(EAR) of contralateral breast,ipsilateral lung,contralateral lung,thyroid and liver were calculated using the radiotherapy-induced secondary primary cancer risks models.Results The treatment plans of two groups met the requirements of clinical.The FFF d-IMRT techniques resulted in a systematic reduction of the organ equivalent dose (OED) (t =2.18-9.72,P ＜ 0.05),and the EAR (t =2.11-9.99,P ＜ 0.05) of contralateral breast,ipsilateral lung,contralateral lung,thyroid and liver was compared to the FF IMRT techniques,especially for the contralateral breast.Conclusions Both FFF and FF d-IMRT plans can achieve comparable target dose coverage in patients with early left-sided breast cancer,while the FFF d-IMRT techniques could reduce the excess absolute risk of contralateral breast,ipsilateral lung,contralateral lung,thyroid and liver.These results are of clinical importance,especially for the early-stage patients with an overall good prognosis.
ABSTRACT
Objective To evaluate the applicability of inhalation risk assessment model provided by US Environmental Protection Agency (USEPA ) in occupational health risk assessment in paper -making,chemical and electroplating industries.Methods A total of 1 1 factories in paper-making,chemical and electroplating industries were investigated. The risk assessment model of USEPA was used to assess occupational health risk levels,including cancer and non-cancer risks.These results were compared with occupational exposure limits,classification of occupational hazards and related literatures.Results The hazard quotient (HQ)of nasal lesions of the olfactory mucosa caused by hydrogen sulfide in paper-making industry was 36.3.The HQs of hyperplasia of nasal mucosa larynx and trachea caused by hydrogen chloride and cerebellar lesions caused by methyl chloride in organosilicon synthesis factory were 8.2 and 1.4 respectively.The HQs of decreased pulmonary function or increased severity of rhinitis and pneumonia caused by ammonia in pesticide factory were 1.2 and 1 .5 respectively.The HQ of impaired motor coordination caused by xylenes in chemical solvent factory was 2.4. The HQs of hyperplasia of nasal mucosa larynx and trachea caused by hydrogen chloride and nasal septum atrophy caused by hexavalent chromium in electroplating industry were 2.3-75.3 and 1 92.5 -25 675 respectively .The risk levels of paper-making,chemical and electroplating industries were all identified as high on the basis of evidence showing that HQs were all higher than 1 .The risk of lung cancer caused by hexavalent chromium in electroplating industry was 0.001 -0.1 647.The results of risk assessment were consistent with the reported literature.Conclusion Inhalation risk assessment model provided by USEPA can be used to assess the occupational health risks of paper -making, chemical and electroplating industries and have better identification ability.