Deterioration of Retro-Reflective Sheet Under Outdoor Weathering and Weather-O-Meter

ABSTRACTMore than one million road signs are installed over thousands of kilometers of highways in India. It is a matter of great concern that there is no strategy to assess their deterioration in terms of quality of retro reflective sheets under natural outdoor weathering and artificial accelerated weathering. The work reported in this paper is focused on how fast the deterioration of reflective sheets of different colors is occurring under natural weathering conditions in India. The deterioration is simulated with artificial weathering under Xenon-Arc chamber with known parameters of weather prevailing in India. This study will help in evaluating the performance of retro-reflective sheets in hours in weather-o-meter to same level of deterioration in the field in terms of days. Data for co-efficient of retro-reflectivity was collected for White, Yellow, Red, Orange, Green, and Blue Type III reflective sheets over a period of seven years in natural weather conditions of Delhi.The best-fit curves technique was adopted to predict the life of retro reflective sheets of different colors in terms of days/months to reach its minimum allowable level. The higher values of R2 for all colors indicate that there is a strong relationship between deterioration and age of reflective sheets in terms exposure in months/days, similarly the R2 values were also found high when the exposure was made in weather-o-meter for few hours. It means that weather conditions in weather-o-meter are exactly being stimulated with prevailing weather conditions in Delhi. The study concludes that over a period of seven years the deterioration of blue color sheet is maximum and deterioration of green color sheet is minimum. This conclusion is also evident from physical parameters such as appearance of signs installed in India. The signs with blue base normally need early replacement in comparison to the signs made out of green sheet for National Highways. The parameters, which were set in weather-o-meter, need the exposure of different hours for different colors of sheets for achieving minimum allowable level of reflectivity as per ASTM standard. The tentative results indicate that reduction of retro reflectivity after 124 months outdoors could be achieved in 90 hours exposure in weather-o-meter. The deterioration varies from color to color and the exposure hours are different for different colours of sheets. This is due to difference in the properties of the pigments used in reflective sheets

Deterioration of Retro-Reflective Sheet Under Outdoor Weathering and Weather-O-Meter

More than one million road signs are installed over thousands of kilometers of highways in India. It is a matter of great concern that there is no strategy to assess their deterioration in terms of quality of retro reflective sheets under natural outdoor weathering and artificial accelerated weathering. The work reported in this paper is focused on how fast the deterioration of reflective sheets of different colors is occurring under natural weathering conditions in India. The deterioration is simulated with artificial weathering under Xenon-Arc chamber with known parameters of weather prevailing in India. This study will help in evaluating the performance of retro-reflective sheets in hours in weather-o-meter to same level of deterioration in the field in terms of days. Data for co-efficient of retro-reflectivity was collected for White, Yellow, Red, Orange, Green, and Blue Type III reflective sheets over a period of seven years in natural weather conditions of Delhi. The best-fit curves technique was adopted to predict the life of retro reflective sheets of different colors in terms of days/months to reach its minimum allowable level. The higher values of R2 for all colors indicate that there is a strong relationship between deterioration and age of reflective sheets in terms exposure in months/days, similarly the R2 values were also found high when the exposure was made in weather-o-meter for few hours. It means that weather conditions in weather-o-meter are exactly being stimulated with prevailing weather conditions in Delhi. The study concludes that over a period of seven years the deterioration of blue color sheet is maximum and deterioration of green color sheet is minimum. This conclusion is also evident from physical parameters such as appearance of signs installed in India. The signs with blue base normally need early replacement in comparison to the signs made out of green sheet for National Highways. The parameters, which were set in weather-o-meter, need the exposure of different hours for different colors of sheets for achieving minimum allowable level of reflectivity as per ASTM standard. The tentative results indicate that reduction of retro reflectivity after 124 months outdoors could be achieved in 90 hours exposure in weather-o-meter. The deterioration varies from color to color and the exposure hours are different for different colours of sheets. This is due to difference in the properties of the pigments used in reflective sheets

Utilization and incorporation of tumor volume data in staging and prognostication of head and neck squamous cell carcinoma treated with definitive radiotherapy: A systematic review

Head and neck squamous cell cancers (HNSCC) are a group of heterogeneous tumors, evident by their diverse behavior and natural history. The largest diameter of tumor measured for T classification may not necessarily reflect the true tumor dimension. There is a need to take into account certain other feature(s) of these tumors other than the maximum single dimension which can reflect the true tumor burden more accurately. Tumor volume has been shown to be a useful and accurate tool burden because it is a measurement of tumor burden in all three dimensions. This review article has compiled and reviewed the literature published in past on impact of tumor volumes (TVs) on the prognosis of head and neck cancers. A comprehensive literature search was performed in PubMed for terms “clonogens,” “TV” or “primary TV (PTV)” or “nodal volume” or “total TV (TTV)” or “volumetric analysis of TV in head and neck” or “predicting response in head and neck cancer” “prognostic factors head and neck cancers” and “outcome in head and neck cancer.” We identified 33 studies which have commented on the impact of TV in HNSCC on treatment outcome, 9 of these had analyzed PTV, 11 studies had analyzed total nodal volume, and 14 studies have analyzed TTV. Besides these, we have dealt with laryngeal cancers separately with 9 studies. This review article is also aimed to enhance our knowledge further regarding how best a physician can incorporate TV data in staging and predicting response to radiotherapy

Reirradiation with IMRT for recurrent head and neck cancer: A single-institutional report on disease control, survival, and toxicity

AimTo study and explores the feasibility and efficacy of re-irradiation (Re-RT) for locally recurrent head and neck cancer (HNC) and second primary (SP) malignancies.BackgroundThe most common form of treatment failure after radiotherapy (RT) for HNC is loco-regional recurrence (LRR), and around 20–50% of patients develop LRR. Re-irradiation (Re-RT) has been the primary standard of care in the last decade for unresectable locally recurrent/SP HNC.Materials and methodsIt was a retrospective analysis in which we reviewed the medical records of 51 consecutive patients who had received Re-RT to the head and neck region at our institute between 2006 and 2015.ResultsForty-eight patients were included for assessment of acute and late toxicities, response evaluation at 3 months post Re-RT, and analyses of locoregional control (LRC) and overall survival (OS). The median LRC was 11.2 months, and at 2 and 5 years the LRC rates were 41% and 21.2%, respectively. A multivariate analysis revealed two factors: initial surgical resection performed prior to Re-RT, and achievement of CR at 3 months after completion of Re-RT to be significantly associated with a better median LRC. The median OS was 28.2 months, and at 1, 2, and 5 years, OS were 71.1%, 55.9% and 18%, respectively. A multivariate analysis revealed initial surgical resection performed prior to Re-RT, and achievement of CR at 3 months post completion of Re-RT being only two factors significantly associated with a better median OS. Acute toxicity reports showed that no patients developed grade 5 toxicity, and 2 patients developed grade 4 acute toxicities.ConclusionRe-RT for the treatment of recurrent/SP head and neck tumors is feasible and effective, with acceptable toxicity. However, appropriate patient selection criteria are highly important in determining survival and treatment outcomes

Tumour volumes: Predictors of early treatment response in locally advanced head and neck cancers treated with definitive chemoradiation

AimTo analyse and predict early response 3 months post definitive chemoradiation (CCRT) utilising tumour volume (TV) measurement in locally advanced head and neck cancers (LAHNC).BackgroundLAHNC are 3-dimentional lesions. The largest diameter of these tumours measured for T-classification may not necessarily reflect the true tumour dimensions. TV accurately reflects the tumour burden because it is a measurement of tumour burden in all three dimensions.Materials and methodsIt is a single institutional prospective study including 101 patients with LAHNC treated with definitive CCRT. TV data noted were primary tumour volume (PTV), total nodal volume (TNV) and total tumour volume (TTV). Response evaluation was done at 3 months after the completion of definitive CCRT and patients were categorised either having achieved complete response (CR) or residual disease.ResultsPatients who had not achieved CR were found to have larger TV compared with those who had achieved CR. There were significant inverse correlations between PTV and response (median 16.37[[ce:hsp sp="0.25"/]]cm3 vs. 45.2[[ce:hsp sp="0.25"/]]cm3; p[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.001), and between TTV and response (median 36.14[[ce:hsp sp="0.25"/]]cm3 vs. 66.06[[ce:hsp sp="0.25"/]]cm3; p[[ce:hsp sp="0.25"/]

Dosimetric impact of setup errors in head and neck cancer patients treated by image-guided radiotherapy

To assess and analyze the impact of setup uncertainties on target volume coverage and doses to organs at risk (OAR) in head and neck cancer (HNC) patients treated by image-guided radiotherapy (IGRT). Translational setup errors in 25 HNC patients were observed by kilovoltage cone beam computed tomography (kV CBCT). Two plans were generated. Plan one – the original plan which was the initially optimized and approved plan of the patient. All patients were treated according to their respective approved plans at a defined isocenter. Plan two – the plan sum which was the sum of all plans recalculated at a different isocenter according to setup errors in x, y, and z-direction. Plan sum was created to evaluate doses that would have been received by planning target volume (PTV) and OARs if setup errors were not corrected. These 2 plans were analyzed and compared in terms of target volume coverage and doses to OARs. A total 503 kV CBCT images were acquired for evaluation of setup errors in 25 HNC patients. The systematic (mean) and random errors (standard deviation) combined for 25 patients in x, y, and z directions were 0.15 cm, 0.21 cm, and 0.19 cm and 0.09 cm, 0.12 cm, and 0.09 cm, respectively. The study showed that there was a significant difference in PTV coverage between 2 plans. The doses to various OARs showed a nonsignificant increase in the plan sum. The correction of translational setup errors is essential for IGRT treatment in terms of delivery of planned optimal doses to target volume