Gold nanoparticle and mean inactivation dose of human intestinal colon cancer HT-29 cells

Background: Mean inactivation dose is a useful radiobiological parameter for the comparison of human cell survival curves. Objectives: Given the importance and accuracy of these parameters, in the present study, the radio sensitivity enhancement of colon cancer (HT-29) cells in the presence of gold nanoparticles (GNPs) were studied using the mean inactivation dose (MID). Materials and Methods: Naked-GNPs with 50 nm diameters were incubated with HT-29 cells. The cytotoxicity and uptake of these particles on HT-29 cells were assessed. After determining the optimum GNPs concentration, the cells were incubated with gold nanoparticle for 24 hours. The change in the MID value as well as the radio sensitization enhancement under irradiation with 9 MV X-ray beams in the presence of GNPs were evaluated by multiple (3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)MTS assay. Results: Cell survival in the presence of GNPs was more than 90% and the maximum uptake of GNPs was observed at 60 μM of gold nanoparticles. In contrast, in the presence of GNPs combined with radiation, cell survival and MID value significantly decreased, so that the radio sensitization enhancement was 1.4. Conclusions: Due to the significant reduction in the mean inactivation dose of colon cancer cells in the presence of gold nanoparticles, it seems that GNPs are suitable options to achieve a new approach in order to improve radiotherapy efficiency without increasing the prescribed radiation dose

Optimization of a tunable process for rapid production of calcium phosphate microparticles using a droplet-based microfluidic platform

Calcium phosphate (CaP) biomaterials are amongst the most widely used synthetic bone graft substitutes, owing to their chemical similarities to the mineral part of bone matrix and off-the-shelf availability. However, their ability to regenerate bone in critical-sized bone defects has remained inferior to the gold standard autologous bone. Hence, there is a need for methods that can be employed to efficiently produce CaPs with different properties, enabling the screening and consequent fine-tuning of the properties of CaPs towards effective bone regeneration. To this end, we propose the use of droplet microfluidics for rapid production of a variety of CaP microparticles. Particularly, this study aims to optimize the steps of a droplet microfluidic-based production process, including droplet generation, in-droplet CaP synthesis, purification and sintering, in order to obtain a library of CaP microparticles with fine-tuned properties. The results showed that size-controlled, monodisperse water-in-oil microdroplets containing calcium- and phosphate-rich solutions can be produced using a flow-focusing droplet-generator microfluidic chip. We optimized synthesis protocols based on in-droplet mineralization to obtain a range of CaP microparticles without and with inorganic additives. This was achieved by adjusting synthesis parameters, such as precursor concentration, pH value, and aging time, and applying heat treatment. In addition, our results indicated that the synthesis and fabrication parameters of CaPs in this method can alter the microstructure and the degradation behavior of CaPs. Overall, the results highlight the potential of the droplet microfluidic platform for engineering CaP microparticle biomaterials with fine-tuned properties

New formula for Calculation of Cobalt-60 Percent Depth Dose

Introduction:  On  the  basis  of  percent  depth  dose  (PDD)  calculation,  the  application  of  dosimetry  in  radiotherapy  has  an  important  role  to  play  in  reducing  the  chance  of  tumor  recurrence. The aim of this study is to introduce a new formula for calculating the centeral axis  percent depth doses of Cobalt-60 beam.   Materials and Methods: In the present study, based on the British Journal of Radiology (BJR)  table, nine new formulas are developed and evaluated for depths of 0.5 - 30 cm and fields of  )4 4( × ) 45 45 ( × − cm 2 .    To  evaluate  the  agreement  between  the  formulas  and  the  table,  the  average of the absolute differences between the values was used and the formula with the least  average was selected as the best fitted formula. The Microsoft Excel 2000 and the Datafit 8.0 soft  wares were used to perform the calculations.      Results: The results of this study indicated that one amongst the nine formulas gave a better  agreement with the PDDs listed in the table of BJR. The new formula has two parts in terms of  log (A/P). The first part as a linear function with the depth in the range of 0.5 to 5 cm and the  other one as a second order polynomial with the depth in the range of 6 to 30 cm. The average of  the differences between the tabulated and the calculated data using the formula ( Δ ) is equal to  0.3152.   Discussion  and  Conclusion:  Therefore,  the  calculated  percent  depth  dose  data  based  on  this  formula has a better ageement with the published data for Cobalt-60 source. This formula could be  used to calculate the percent depth dose for the depths and the field sizes not listed in the BJR table

An Analytical-empirical Calculation of Linear Attenuation Coefficient of Megavoltage Photon Beams

Background: In this study, a method for linear attenuation coefficient calculation was introduced. Methods: Linear attenuation coefficient was calculated with a new method that base on the physics of interaction of photon with matter, mathematical calculation and x-ray spectrum consideration. The calculation was done for Cerrobend as a common radiotherapy modifier and Mercury. Results: The values of calculated linear attenuation coefficient with this new method are in acceptable range. Also, the linear attenuation coefficient decreases slightly as the thickness of attenuating filter (Cerrobend or mercury) increased, so the procedure of linear attenuation coefficient variation is in agreement with other documents. The results showed that the attenuation ability of mercury was about 1.44 times more than Cerrobend. Conclusion: The method that was introduced in this study for linear attenuation coefficient calculation is general enough to treat beam modifiers with any shape or material by using the same formalism; however, calculating was made only for mercury and Cerrobend attenuator. On the other hand, it seems that this method is suitable for high energy shields or protector designing

Effective point of measurement in cylindrical ion chamber for megavoltage photon beams

Introduction: For dose measurement in Megavoltage (MV) photon beams with ion chambers, the effect of volume occupied by the air cavity is not negligible. Therefore, the result of measurement should be corrected with a displacement perturbation correction factor (Pdis) or using an effective point of measurement (EPOM). The aim of this study is to calculate the EPOM for cylindrical ion chamber and to evaluate the fixed EPOM that was recommended by standard dosimetry protocols. Materials and Methods: Percent depth doses (PDDs) for 6 MV and 18 MV were measured with two types of chambers for different depths and field sizes. The EPOM was calculated using results obtained from measurement data for two types of chambers, comparison of the readings, and using dosimetry, mathematical, and statistical consideration. For displacement correction factor �r=0, �r= 0.6r and different �r, the minimum standard deviations ratio (SDRs) were calculated at several depths and field sizes. Results: Maximum level of SDRs was about 0.38 and 0.49 (when assuming variable �r) for 6 MV and 18 MV, respectively (which was less than 0.5 and acceptable). This quantity was greater than one (for assuming �r= 0.6r) and greater than 2 when there was no shift (�r =0) Conclusion: The results show that the recommended shift for cylindrical ion chamber in dosimetry protocols (upstream of 0.6r) is not correct and using a fixed value for the EPOM at all photon beam energies, depths, and field sizes is not suitable for accurate dosimetry

Impact of Prolonged Fraction Delivery Time Modelling Stereotactic Body Radiation Therapy with High Dose Hypofractionation on the Killing of Cultured ACHN Renal Cell Carcinoma Cell Line

Introduction: Stereotactic body radiotherapy delivers hypofractionated irradiation with high dose per fraction through complex treatment techniques. The increased complexity leads to longer dose delivery times for each fraction. The purpose of this study is to investigate the impact of prolonged fraction delivery time with high-dose hypofractionation on the killing of cultured ACHN cells. Methods and Materials: The radiobiological characteristics and repair halftime of human ACHN renal cell carcinoma cell line were studied with clonogenic assays. A total dose of 20 Gy was administered in 1, 2 or 3 fractions over 15, 30 or 45 min to investigate the biological effectiveness of radiation delivery time and hypofractionation. Cell cycle and apoptosis analysis was performed after 3-fraction irradiation over 30 and 45 min. Results: The α/β and repair half-time were 5.2 Gy and 19 min, respectively. The surviving fractions increased with increase in the fraction delivery time and decreased more pronouncedly with increase in the fraction number over a treatment period of 30 to 45 min. With increase in the total radiation time to 30 and 45 min, it was found that with the same total dose, 2- and 3-fraction irradiation led to more cell killing than 1-fraction irradiation. 3-fraction radiation induced G2/M arrest, and the percentage of apoptotic cells decreased when the fraction delivery time increased from 30 min to 45 min. Conclusion: Our findings revealed that sublethal damage repair and redistribution of the cell cycle were predominant factors affecting cell response in the prolonged and hypofractionated irradiation regimes, respectively

Estimating effective doses of critical organs due to abdomen and pelvic CT scans using impact CT dosimetry

Using computed tomography (CT) scans in clinical diagnosis has been dramatically increased during recent years. This technique is associated with high levels of radiation dose to patients compared to other imaging methods. Therefore, using accurate and precise methods of estimating the absorbed dose in CT scans is of prime importance. The present study aims to estimate the absorbed and effective doses due to abdomen and pelvic CT scans using ImPACT dose tool. Demographic data and dosimetry data the CT scan of the abdomen and pelvic for 52 patients were used to calculate the critical organs' absorbed and effective doses. The data of CT scans were registered into ImPACT dose tool. In addition, a new equation for estimating the body effective dose using body mass index (BMI) was proposed. The findings showed that the absorbed dose of the most organs was within the dose thresholds recommended by the ICRP103. In addition, the averaged effective dose was less than the predicted value by ICRP-103. Furthermore, a new equation was proposed to estimate the effective dose of the body as a function of patient's BMI. The estimated values by this equation were well in agreement with the calculated dose by ImPACT (R2>0.95). Using our proposed equation for the effective dose calculation, the effective dose of a patient during an abdomen and pelvic CT scan can be estimated