In vivo measurements during radiation treatment of head and neck cancer patients

PurposeThe evaluation of quality of head and neck patient irradiation by analysis of entrance and exit doses measurements, calculation of midline doses, dosimetric errors calculation and analysis, and defining their sources.Material and MethodsThe study included 262 patients (300 fields). 1015 entrance and 863 exit doses were measured. 863 midline doses were calculated. 50 measurements wre performed using TLD and the remaining by semiconductor diodes.ResultsThe mean dosimetric errors of midline, entrance and exit doses were respectively 0.42%, −1.04% and −0.27%. Numerous sources of errors were found and some of them were corrected during the treatment. There were the following most important factors influencing the value of dosimetric error: kind of wedge filters and fixating masks, SSD, tumour and detector localization, irradiation technique, time of radiotherapy and discrepancies between real and measured thickness of irradiated volume.ConclusionThe value of dosimetric error is not constant and it may change during long time of fractionated radiation treatment. Some anatomical (tumour localisation, density of surrounding tissues) and techical (irradiatin technique, immobilization masks, wedge filters and the discrepancy between planned and real SSD) parameters of irradiation have to be precisely defined and checked out during the treatment because they can be the main sources of dosimetric errors

66. Late effects of CNS prophylactic irradiation in childhood due to LLA using Magnetic Resonance Spectro-skopy. (preliminary report)

PurposeThe aim of this study was to evaluate changes in magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) of the brain in survivars with Acute Lymphoblastic Leukemia to assess neurotixicity follow profilactic brain irradiation.MethodsTen from 100 patients with LLA treated in Department of Pediatric Hematology from 1990 to 1995 and irradiated in Centre of Oncology were icluded in MRI and MRS studies. The study group included 6 male and 4 female. All patients had been irradiated for brain using fraction dose of 1,8 Gy up to total dose of 18 Gy and had recived MTX based chemotherapy in doses depending on level of risk. Two of them were included in low risk and eight in intermediate risk.ResultsMRI of brain was abnormal in 5 cases. There were mild white matter changes.The changes were Been in H- MRS metabolite ratios. In one of these cases we observed a impair of verbal functions.ConclusionsThe MRS could be valuable method to access brain tissue metabolism after radiotherapy. That noninvasive method may be recomended for children with LLA to observe neurotoxicity of profilactic irradiation

Adherence measurements and corrosion resistance in primer/hot-dip galvanized steel systems

This paper focuses on the adherence during ageing of a primer (made of polyester resins crosslinked with melamine) applied onto hot-dip galvanized (HDG) steel for coil coating application and its influence on corrosion protection. A chromium-free surface treatment, composed of fluorotitanic acid, phosphoric acid, manganese phosphate, and vinylphenol was applied on the HDG steel to obtain high corrosion resistance and high adherence of a polyester and melamine primer. The influence of the manganese phosphate on the corrosion and adherence was investigated. To measure the adherence between the metal and the primer, a three-point flexure test was set up. The adherence was then linked with corrosion resistance during ageing, using electrochemical impedance spectroscopy