Leak and Scattering Assessment by Optically Stimulated Luminescence Dosimetry in a Helical Linear Accelerator / Valoración de Fuga y Dispersión por medio de Dosimetría de Luminiscencia Estimulada Ópticamente (OSL) en un Acelerador Lineal Helicoidal

Radiation absorbed doses to organs outside the radiation therapy treatment beam can be significant and therefore of clinical interest. Two sets of out-of-beam measurements were performed measuring the leak dose and the scattered dose, at 5 points within the accelerator components (accelerator tube and collimator) and at 21 points on the equipment and surroundings based on a positioning scheme. For this purpose, 52 Optically Stimulated Luminescence (OSL) dosimeters were used in a latest generation helical linear accelerator. Of the 200 cGy fired at a cheese-like phantom, 0.332% of the out-of-beam dose contribution was found to come from the leak and 0.784% was transformed into scattering. For these dose values, estimates of the risk of second tumors in long-term survivors indicate a reduced probability of acquiring a second secondary radiation malignancy, based on information from the 1990 BEIR Committee report.

La dosis absorbida de radiación a órganos fuera del haz de tratamiento de radioterapia puede ser significativa y, por lo tanto, de interés clínico. Se realizaron dos sets de mediciones fuera del haz para determinar la dosis de fuga y la dosis dispersa, en 5 puntos dentro de los componentes del acelerador (tubo de aceleración y colimador) y 21 puntos en el equipo y alrededores basado en un esquema de posicionamiento. Para este fin se utilizaron 52 dosímetros de luminiscencia estimulada ópticamente (OSL, Optically Stimulated Luminescence), en un acelerador lineal helicoidal de última generación. De los 200 cGy disparados a un maniquí tipo queso, se encontró que el 0.332% de la contribución de dosis fuera del haz provenía de la fuga y 0.784% se transforma en dispersión. Para estos valores de dosis, las estimaciones del riesgo de segundos tumores en los supervivientes a largo plazo indican una reducida probabilidad de contraer una segunda malignidad por radiación secundaria, según la información del informe del Comité BEIR de 1990.

Analysis on eye lens doses and hand doses of working operator in 125I seed source implantation / 中华放射医学与防护杂志

Objective To measure the doses to eye lens and hands of workers,using thermo luminescent dosimeter (TLD) and optically stimulated luminescence dosimeter (OSLD).Methods TLDs in the same batch were annealed,packed and stuck to the flat abdomen of Alderson-Phantom at a distance of about 15 cm from 125I seed source,while irradiated at different doses:1.0,1.5,3.0,5.0,10.0,12.0,20.0,25.0,30.0,50.0 and 60.0 μ Gy.And then TLDs were measured by dosimeters to establish a dose calibration curve.By implanting seed source into the selected lung for 14 cases,belly for 10 cases,pelvic for 5 case and neck for 6 cases while placing calibrated TLDs on the left,middle and right above eyes,left and right hands of the workers to obtain the location-specific kerma values.Finally,the conversion factors Hp (3) and Hp (0.07) were used to calculate the values of dose equivalent to eye lens and hands.Additionally,OSLDs were used to measure the doses to workers in the same way.Results The TLD-measured eye lens dses to the operator and his assistant were 0.8 and 1.6 mSv in lungs,1.3 and 1.2 mSv in bellies,0.9 and 0.6 mSv in pelves,0.3 mSv in necks,respectively.Meanwhile,hand doses to the operator and his assistant were 1.4 and 2.1 mSv in lungs,1.2 and 1.0 mSv in bellies,0.5 and 0.9 mSv in pelves,0.1 mSv in necks,respectively.The maximum doses to eye lens and hands were 1.2 and 1.0 mSv,respectively in a single treatment.OSLD-measured dose equivalents from lung therapy were 0.2 and 0.1 mSv for eye lens of the operator and his assistant and 0.4 and 0.6 mSv for hands.For belly therapy,the accumulated dose equivalent to hands of the operator was 0.1 mSv while those for other types of therapy were 0 mSv.Conclusions TLDs have the capability to measure not only accumulated dose but also dose equivalent from a single therapy According to ICRP 118 publication and as estimated in the present study,the number of therapy should be not more than 17 every year.OSLDs only give the accumulated dose,the accuracy of which needs to be studied in low-dose measurement.

The measurements of eye lens dose for occupational staff in interventional procedures / 中华放射医学与防护杂志

Objective To establish methods of measuring the eye lens dose to interventional staff,to obtain relevant dose data and to provide a scientific basis for reducing eye lens dose.Methods Two kinds of dosimeters,thermoluminescent dosimeter (TLD) and optically stimulated luminescence dosimeter (OSLD),were selected to measure the personal dose equivalent HP (3) to eye lens of occupational staff in several kinds of interventional procedures,including cardiovascular interventional procedures,cerebrovascular interventional procedures etc.Five types of Digital Subtraction Angiography (DSA) equipment were chosen in the study,including single tube equipment and double tube equipment.Results The eye lens dose HP (3) to interventional staff varied significantly with different interventional procedures.The lowest dose is shown in the coronary angiography procedure,while the highest dose shown in the cerebral stenting procedure.For the same type of interventional procedure,the eye lens dose to the primary interventionist was the highest.For same interventionist,the dose to the left eye was obviously higher than that to the right eye.In addition,the measured results of OSLD were apparently higher than that of TLD.Conclusions Both TLD and OSLD could be used to measure eye lens dose,and the ways of calibrating TLD to evaluate personal dose equivalent HP (3) were feasible.The reason of significant difference between the measured results of TLD and OSLD needs further research.