فهرست مطالب

Medical Physics - Volume:17 Issue: 1, 2020
  • Volume:17 Issue: 1, 2020
  • تاریخ انتشار: 1398/11/08
  • تعداد عناوین: 9
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  • Asnaeni Ansar, Dahlang Tahir *, Bualkar Abdullah, Nurhasmi Nurhasmi, Jusmawang Jusmawang, Satrial Male, Ruth Meisye Kaloari Pages 1-6
    Introduction
    Phantom is an object that can be used to investigate the accuracy of radiation dose delivered to patients. Phantom is usually produced from the combination of the silicone rubber as a matrix and glycerin as a filler to form a composite for the replacement of the human soft tissue. The composite is imaged using computed tomography (CT) simulator for the determination of the attenuation coefficient.
    Material and Methods
    The Phantom in the current study has been synthesized from silicone rubber with and without the addition 10% and 20% of glycerin. The type of silicone rubber in this study was Room Temperature Vulcanized (RTV) 52 with blue catalyst by a ratio of 100:5 (wt%). Samples were scanned using CT simulator to obtain the images and then exported to the Eclipse treatment planning system for analysis. The region of interest (ROI) was at the center of an area of 50×50 pixels to determine the CT number.
    Results
    The ROI results for the sample without and with the addition of glycerin 10% and 20% resulted in the CT values of 287.4, 280.5, and 225.2 HU, respectively, which were within the ROI range of the human soft tissue. The attenuation coefficients of the 3 samples were 0.239, 0.238±0.001, and 0.233±0.001 cm-1 for no glycerin, glycerin 10%, and glycerin 20%, respectively. The values of the half-value layer were 2.902±0.001, 2.911±0.001, and 2.980± 0.001 cm for phantom with no glycerin, glycerin 10%, and glycerin 20%, respectively.
    Conclusion
    Phantoms in the current study were indicative of high potentials as an object of research for radiotherapy and educational purposes. Moreover, the composite with glycerin 20% could be the best surrogate of tissue in order to study human liver.
    Keywords: Attenuation Coefficient, Silicone Elastomer, Phantoms, Imaging Tomography, X-Ray Computed
  • Mohammad Ashrafinia, Asghar Hadadi *, Dariush Sardari, Elham Saeedzadeh Pages 7-14
    Introduction
    The utilization of high-energy photons in the medical linear accelerator can lead to photoneutron production. This study aimed to evaluate the effect of the physical components of the head, including flattening filter (FF) andmultileaf collimator (MLC), as well as the dependence of therapeutic field size on the photoneutron spectrum, dose, and flux.
    Material and Methods
    The present study reported the simulation of the fundamental linac head components of the Varian Clinac 2100 performing in X-ray mode with 18 MV energy by the FLUKA code. The percentage depth dose and lateral dose profile were measured using a PTW thimble chamber to ensure the simulation reliability.
    Results
    Photoneutron spectrum analysis indicated that neutrons with highest relative biological effectiveness were delivered to the phantom surface, and opening the field from 0×0 to 40×40  shifted the spectrum by 24.545% to the higher energies. The target and the vicinity parts played the most prominent roles in neutron contamination. The relationship between the field size and the photoneutron dose was non-linear, and it reached a peak of 20×20 . Although using small fields formed by the MLC contribute to a lower dose compared to those shaped by the jaws, MLC-equipped machines result in 21.98% higher dose. Moreover, the flattening filter removal unexpectedly increased the isocenter photoneutron dose by 11.63%. This undesirable dose can be up to 2.54 mSv/Gy for the reference field at the isocenter while the out-of-field dose is about 0.5 mSv/Gy for most of the field dimensions.
    Conclusion
    As a result, it is critical to consider this unwanted absorbed dose, which is seriously influenced by the implemented therapeutic conditions.
    Keywords: Fast Neutrons, Linac, Monte Carlo, FLUKA
  • Atef El Taher, Ali Abojassim, Laith Najam *, Hussien Mraity Pages 15-20
    Introduction

    Given that the groundwater is a radon contaminated and used as a source for drinking water, then measuring the amount contamination is of high necessity.

    Material and Methods

    The measurement was performed using RAD-7 detector.

    Results

    The measured radon concentration values ranged 1.20-15.43 Bq/l with the mean of 5.18±0.39 Bq/l. The estimated total annual effective doses based on radon concentrations in drinking water were within the range of 6.34-81.62 µSv/y for infants, 2.34-30.04 µSv/y for children, and 3.07-39.42 µSv/y for adults. Moreover, the corresponding mean values were estimated at 27.41±2.06, 10.08±0.76, and 13.23±0.99 µSv/y, respectively.

    Conclusion

    The total annual effective dose in all samples were within the global average level of ingestion exposure dose value (0.1 mSv/y from radon concentrations) reported by the United Nations Scientific Committee on Effects of Atomic Radiations. Therefore, there are no risks for the consumption of these water samples.

    Keywords: Radon concentrations, ground water, Annual Effective Dose, Qassim, Saudi Arabia
  • Jaffar Jaffar Fatahi Asl, Mohammad Eskandari, Abdol Hossein Bigdeli *, Fatemeh Jahangirimehr Pages 21-26
    Introduction

    Protection against harmful effects of ultraviolet radiation (UV) is measured under Ultraviolet Protection Factor (UPF) scale. The utilization of protective clothing is the best way to deal with the damage caused by ultraviolet radiation. The purpose of this study was to compare the ultraviolet ray protective factor of pure cotton and cotton coated with titanium dioxide (TiO2) nanoparticles using the electrospinning method with two natural and artificial generators.

    Material and Methods

    This is an analytical-descriptive study in which, a pure cotton fabric and a cotton fabric coated with nanoparticles of dioxiditenium were coated for 10, 20 and 40 minutes, as an example, with the titanium dioxide with two types of sunlight and artificial light (widespread and dotted) beams. UV radiation divided into three spectra A, B and C that we use UV-C to measurement. Finally, the comparison of the average UV-c radiation penetration from different fabrics were conducted. We use SPSS Ver.22 to analyze data and p-value<0.05. 

    Results

    The highest and the lowest amount of penetration were for pure and coated cotton fibers for 40 min of UV-C radiation, respectively. As the beam decreases, the UPF rises. In nano-coated fabrics, the amount of beam penetration is lower and absorption is higher giving higher UPF.

    Conclusion

    Due to the very low UPF, cotton fabrics are not suitable for utilization in areas with UV radiation. Therefore, in order to protect against UV radiation, fabrics coated with TiO2 nanoparticles can be used in the domain of health care.

    Keywords: Cotton Fabric Electrospinning Nanoparticle, Ultraviolet-C Beam Ultraviolet Protection Factor
  • Mpumelelo Nyathi * Pages 27-34
    Introduction
    Radical radiation therapy of head and neck cancers may injure the salivary glands and reduce their function. Single-photon emission computed tomography (SPECT) images maybe used to evaluate function post-therapy. However, accurate quantification is hindered by the partial volume effects (PVEs). The present study involved the introduction of a PVEs quantification technique aimed at improved quantification of the salivary glands function.
    Material and Methods
    The parotid and submandibular salivary glands were mimicked with hollow spheres. The left parotid (LP), right parotid (RP), left submandibular (LSM), and right submandibular (RSM) salivary glands had diameters; 16, 14, 11, and 12 mm, respectively. Technetium-99m solution (activity concentration; 300 kBq/mL) filled the salivary glands prior to implanting into a hollow head and neck phantom later filled with the technetium-99m solution (activity concentration; 1440 Bq/mL). A SPECT image was acquired on 128 × 128 matrix size over 30 min and reconstructed using filtered back projection algorithm (Butterworth filter with a cut-off frequency of 0.9 cycles per pixel and an order of 9). Reconstructed images were quantified using ImageJ software.
    Results
    The image counts extracted from the LP, RP, RMS, and LMS salivary glands SPECT images were 672 019, 494 842, 398 091, and 262 908, respectively after the quantification of PVEs, compared to 486 320, 347 534, 272 940, and 175 307 before the quantification of PVEs. The respective quantitative errors were 27%, 29%, 31%, and 33%.
    Conclusion
    Quantification of PVEs allows recovery of image counts spread outside the image pixels leading to improved quantification.
    Keywords: SPECT, salivary glands, Radiation Therapy
  • John Owusu Banahene *, Prince Appiah, Daniel Adjei, Benjamin Gbekor, Collins Azah, Paul Amoah, Joseph Amoako, Emmanuel Darko, Godfred Asiedu, Philip Owusu Manteaw Pages 35-37
    Introduction

    Nuclear moisture density gauges are widely used in construction industry in different countries across the world, including Ghana, on a large scale. Like all irradiating devices, the nuclear gauges should be subjected to radiation safety assessment based on radiation protection and safety principles. Regarding this, the objective of this research was to investigate the radiation safety of the nuclear moisture density gauges to ensure the absence of any leakages from the radioactive source.

    Material and Methods

    For the purpose of the study, a survey meter (RADOS-120) was used to measure and record the radiation dose once at a distance of 1 m from the surfaces of all sides of the nuclear moisture density gauge and very close distance from the surfaces of the device. Moreover, the device was examined using radiation contamination test and counts on a standard block.

    Results

    A total of nine nuclear moisture density gauges manufactured by Troxler Electronics Inc. in the USA were evaluated within a period of 3 years. The minimum and maximum average dose rates were 0.49 and 66.67 μSv/h, respectively. The highest and lowest average dose rates were recorded in 2017 and 2016 on the devices with serial numbers of 38260 and 32839, respectively.

    Conclusion

    The assessment of the nuclear moisture density gauges under study revealed noradiation contamination leakage. Furthermore, all the evaluated gauges were shown to function properly and were safe for the intended purposes.

    Keywords: Calibration, Background Radiation, Dose Rate, Radiation Source
  • Rezvan Ravanfar Haghighi *, Sabysachi Chatterjee, Sepideh Sefidbakht, Reza Jalli, Vani Vardhan Chatterjee Pages 38-47
    Introduction
    The performance of computed tomography is routinely checked using phantoms, which are known as important diagnostic imaging tools. Depending upon the aim of the study, different phantoms are designed, while trying to satisfy certain levels of diversities in their application.
    Material and Methods
    The present study describes the construction of an inexpensive phantom designed for simultaneous measurements of 12 different samples. The body of the phantom, test tube holders, and test tubes were made of materials of low attenuation coefficient. Body of the phantom was filled with water. Test tubes filled with solutions of known chemical compositions were mounted on the test tube holders.  The whole phantom was scanned at 80, 100, 120, 140 kVp to evaluate the performance of the CT system. Using Hounsfield Unit (HU) data from these liquid samples of known electron density, the phantom was calibrated for electron density measurements.
    Results
    The system's accuracy and reproducibility were verified by measuring the HU values for some known materials. According to the results obtained from the experimental datawith liquid samples, the accuracy of the water and noise was within ±3.2 HU and 0.6%, respectively. Moreover, the image uniformity error was less than ±2 HU, and CT system's linearity for calibration was estimated with 99.9% confidence.
    Conclusion
    The present system gives satisfactory results with known samples and can be used with confidence for characterizing unknown materials.
    Keywords: Computed Tomography Phantom, Quality Control Attenuation, photoelectric effect
  • S.Ehsan Razavi *, Hamed Khodadadi Pages 48-57
    Introduction
    Segmentation of brain images especially from magnetic resonance imaging (MRI) is an essential requirement in medical imaging since the tissues, edges, and boundaries between them are ambiguous and difficult to detect, due to the proximity of the brightness levels of the images.
    Material and Methods
    In this paper, the graph-based method is proposed to solve the segmentation of MRI brain images wherein a weighted undirected graph is assigned to the image with each edge of the graph corresponding to an image pixel. The edge weight between two nodes demonstrated the similarity between two pixels of the image. Thereafter, a cost function, such as relative extremes and turning point, was assigned to the graph, which matched the derivation of the function. Minimization of this cost function, which was equivalent to the shortest path in a graph, led to image segmentation.
    Results
    The advantageof the graph method over other methods is the simultaneous construction of spatial information at a high rate. Moreover, this method is implemented on the pixels in the space and can partition MRI brain images with low error in an effort to improve the previous methods. The comparisons demonstrated that the accuracy of the MRI brain image segmentation would be improved through the application of the present method.
    Conclusion
    The obtained results of the current study indicated the high accuracy of the proposed method (about 97.5%), compared to other similar methods. Therefore, this method can accurately distinguish various types of brain MRI tissues and have clinical applications.
    Keywords: Image Processing, magnetic resonance imaging, Brain, Segmentation
  • Hamza Sulemana *, Stephen Inkoom, Edem Sosu, Cyril Schandorf Pages 58-65
    Introduction

    The study aimed to assess absorbed and effective doses in organs through computed tomography (CT) examinations using automatic exposure control (AEC) and fixed tube current (FTC) techniques.

    Material and Methods

    Scanning parameters were obtained for routine adult CT examinations and used to estimate the organ absorbed and effective doses using CT-Expo software. The estimated effective doses were based on International Commission on Radiological Protection publication 103 recommendations.

    Results

    Regarding the scans performed with AEC, doses to head, chest, abdomen and pelvic organs were within the range of 19.7-41.8, 6.4-17.4, 19.2-20.9, and 10.5-24.9 mGy respectively. Moreover, the effective doses for the mentioned organs were 1.6, 6.1, 6.4 and 5.4 mSv respectively. Considering FTC technique, doses to organs ranged 16.7-75.5, 4.1-52.2, 10.6-33.2 and 5.2-38.7 mGy respectively. Moreover, the mean effective doses of FTC were 2.1, 6.9, 9.4 and 6.1 mSv, respectively. Examinations performed with AEC technique induced a dose reduction of 9% and 34% for head organs, 52, 62 and 25% for chest organs, 16% and 14% for abdomen organs, and 11% and 10% for pelvic organs, compared to the FTC. A dose increase of 3% was observed for testes. The mean effective doses for scans with AEC were 13-46% lower than those obtained by FTC.

    Conclusion

    According to the obtained results of the current study, the estimated doses for scans with AEC technique were in a lower level compared to FTC technique. Accordingly, it is recommended to utilize this technique for CT examinations to ensure optimal dose reduction to radiosensitive organs.

    Keywords: Computed Tomography, organ dose, Radiation Dosimetry, Radiology