Dosimetry of gamma chamber blood irradiator using Gafchromic EBT film

Diacetylene-Based Colorimetric Radiation Sensors for the Detection and Measurement of γ Radiation during Blood Irradiation

Blood and its cellular components are irradiated by ionizing radiation before transfusion to prevent the proliferation of viable T lymphocytes which cause transfusion associated-graft versus host disease. The immunodeficient patients undergoing chemotherapy for various malignancies are at risk of this disease. The international guidelines for blood transfusion recommend a minimum radiation exposure of 25 Gray (Gy) to the midplane of the blood bag, while a minimum dose of 15 Gy and a maximum dose of 50 Gy should be given to each portion of the blood bag. Therefore, precise dosimetry of the blood irradiator is essential to ensure the adequate irradiation of the blood components. The paper presents the fabrication of diacetylene-based colorimetric film dosimeters for the verification of irradiated doses. The diacetylene analogues are synthesized by tailoring them with different amide-based headgroups followed by their coating to develop colorimetric film dosimeters. Among all the synthesized diacetylene analogues, aminofluorene-substituted diacetylene exhibits the most significant color transition from white to blue color at a minimum γ radiation dose of 5 Gy. The quantitative study of color change is performed by the digitization of the scanned images of film dosimeters. The digital image processing of the developed film dosimeters facilitates rapid dose measurement which enables their facile implementation and promising application in routine blood irradiator dosimetry.

Radiation dose verification of an X-ray based blood irradiator using EBT3 radiochromic films calibrated using Gamma Knife machine

Aim

Blood irradiators (BI) initial acceptance testing and routine annual dosimetry checks require radiation dose measurements in order to comply with regulatory requirements.

Background

Traditionally thermo-luminescence dosimeters (TLD) have been used to measure the dose. The EBT3 film is reported to be a better dosimeter for low energy X-rays than its predecessors EBT2 and EBT. To the best of our knowledge, the use of EBT3 films to perform dosimetry on X-ray based BI has not been reported yet.

Materials and methods

We performed routine radiation dosimetry checks using EBT3 films on a new X-ray based BI and compared the results with TLD dosimetry. Calibration films were irradiated with radiation beam from a Co-60 Gamma Knife (GK) radiosurgery machine and, alternatively, using an Ir-192 high dose rate (HDR) brachytherapy device. The films were calibrated to cover a wide dose range from 1 to 40 Gy. Such a wide dose range has not been reported yet in BI film dosimetry.

Results

We obtained a relative difference of about 6.6% between doses measured using TLD and those measured using EBT3 films. Both irradiation methods using GK or HDR were found to be adequate for the calibration of the EBT3 Gafchromic films.

Conclusions

We recommend the use of EBT3 films in routine X-ray based BI dosimetry checks. The presented method takes advantage of available radiotherapy equipment that can be efficiently used for EBT3 films calibration. The method is fast, reproducible and saves valuable medical physicist's time.

Chondrocytes differentiated from human induced pluripotent stem cells: Response to ionizing radiation

Purpose

Data on the response of chondrocytes differentiated from hiPSCs (hiPSC-DCHs) to ionizing radiation (IR) are lacking. The aim of present study was to assess DNA damage response (DDR) mechanisms of IR-treated hiPSC-DCHs.

Methods and materials

The following IR-response characteristics in irradiated hiPSC-DCHs were assessed: 1) the kinetics of DNA DSB formation; 2) activation of major DNA repair mechanisms; 3) cell cycle changes and 4) reactive oxygen species (ROS), level of key markers of apoptosis and senescence.

Results

DNA DSBs were observed in 30% of the hiPSC-DCHs overall, and in 60% after high-dose (> 2 Gy) IR. Nevertheless, these cells displayed efficient DNA repair mechanisms, which reduced the DSBs over time until it reached 30% by activating key genes involved in homologous recombination and non-homologous end joining mechanisms. As similar to mature chondrocytes, irradiated hiPSC-DCH cells revealed accumulation of cells in G2 phase. Overall, the hiPSC-DCH cells were characterized by low levels of ROS, cPARP and high levels of senescence.

Conclusions

The chondrocyte-like cells derived from hiPSC demonstrated features characteristic of both mature chondrocytes and “parental” hiPSCs. The main difference between hiPSC-derived chondrocytes and hiPSCs and mature chondrocytes appears to be the more efficient DDR mechanism of hiPSC-DCHs. The unique properties of these cells suggest that they could potentially be used safely in regenerative medicine if these preliminary findings are confirmed in future studies.

Radiochromic film containing poly(hexa-2,4-diynylene adipate) as a radiation dosimeter

A radiation-sensitive polymer poly(hexa-2,4-diynylene adipate) (PHDA) was synthesized and incorporated into polyvinyl butyral films for radiation dose measurements in the 0.5 - 60 kGy range. PHDA undergoes crosslinking polymerization upon exposure to γ-rays, which changes its color from very pale yellow to deep orange-yellow. The color change is directly related to the absorbed dose. The absorption spectrum of the irradiated films features one absorption band around 500 nm with a shoulder around 465 nm. With increasing absorbed dose, the two bands grow in intensity and move towards higher wavelengths. The dosimeter is nearly insensitive to variations of the humidity in the range of 0-54% and temperature in the range of 30-45 °C during irradiation. The color intensifies after irradiation, both in the dark and in the light at room temperature, which reflects the continuing crosslinking polymerization. However, at - 4 °C, the color intensity does not change with time.

Dosimetric characteristics of a radiochromic polyvinyl butyral film containing 2,4-hexadiyn-1,6-bis(n-butyl urethane)

A radiation-sensitive compound 2,4-hexadiyn-1,6-bis(n-butyl urethane) (HDDBU) was synthesized, characterized by FTIR spectroscopy, and introduced into a thin polyvinyl butyral film to form a radiation dosimeter for industrial irradiation facilities. The monomer polymerizes under gamma radiation, inducing change in the film spectrum in the range of 200-400 nm. According to XRD spectroscopy, the film contains monomeric HDDBU in a non-crystalline state. The dose response function, radiation sensitivity, and dependences of the response on environmental factors were studied. Uncertainty of dose measurements with the proposed dosimetry system was analyzed in detail.

Dosimetry of gamma chamber blood irradiator using PAGAT gel dosimeter and Monte Carlo simulations

Currently, the use of blood irradiation for inactivating pathogenic microbes in infected blood products and preventing graft‐versus‐host disease (GVHD) in immune suppressed patients is greater than ever before. In these systems, dose distribution and uniformity are two important concepts that should be checked. In this study, dosimetry of the gamma chamber blood irradiator model Gammacell 3000 Elan was performed by several dosimeter methods including thermoluminescence dosimeters (TLD), PAGAT gel dosimetry, and Monte Carlo simulations using MCNP4C code. The gel dosimeter was put inside a glass phantom and the TL dosimeters were placed on its surface, and the phantom was then irradiated for 5 min and 27 sec. The dose values at each point inside the vials were obtained from the magnetic resonance imaging of the phantom. For Monte Carlo simulations, all components of the irradiator were simulated and the dose values in a fine cubical lattice were calculated using tally F6. This study shows that PAGAT gel dosimetry results are in close agreement with the results of TL dosimetry, Monte Carlo simulations, and the results given by the vendor, and the percentage difference between the different methods is less than 4% at different points inside the phantom. According to the results obtained in this study, PAGAT gel dosimetry is a reliable method for dosimetry of the blood irradiator. The major advantage of this kind of dosimetry is that it is capable of 3D dose calculation.

PACS number: 87.53.Bn