Iranian Journal of Medical Physics
Volume:18 Issue: 2, Mar-Apr 2021

Neutron dosimetry is a challenging subject in radiation protection. Responses of neutron dosimeters mostly depend on the neutron energy spectrum. Dosimeter response corresponding to a dose-equivalent in the calibration field is different from responses in other neutron fields. Consequently, the dose estimated by neutron dosimeters may be associated with great uncertainty. Therefore, the present study aimed to modify the response in different neutron fields in order to reduce this uncertainty.

Thermo-luminescent dosimeters (TLDs) are widely used to determine neutron dose-equivalent. In the present study, a set of TLD-600 and TLD-700 dosimeters included in a TLD card was utilized to determine the response to “fast” neutrons of 241Am-Be,252Cf, and 239Pu-Be standard fields in four dose-equivalents of 5, 10, 15, and 20 mSv. Meanwhile, 241Am-Be was regarded as the calibration field.

As evidenced by the obtained results, for equal dose-equivalents, the original responses in 252Cf and 239Pu-Be fields are smaller, compared to those in the 241Am-Be filed. The maximum discrepancies were obtained at 26.8% and 42.5% occurring at 20 and 5 mSv, respectively. After the application of a correction factor equal to the average of relative responses (i.e., in 241Am-Be to two other fields) corresponding to all dose-equivalents considered, these differences reduced to 12.4% and 21.7%.

It can be concluded that the correction method used in the present study could enhance the accuracy of dose estimated by TLDs in fast neutron fields.

Accurate and early diagnosis of cancer is an important issue in modern healthcare systems. Raman spectroscopy, as a non-invasive optical technique for evaluating intact tissues at a molecular level, has attracted the researchers’ attention. Despite recent advances, efforts are still being made to improve the sensitivity and specificity of Raman spectroscopy-based cancer detection. The present study aimed to identify three classes of breast tissues, that is, normal tissues, benign lesions, and cancer tissues, using an artificial neural network (ANN).

To improve the ANN discrimination power, a novel topologically optimized ANN, known as self-constructing neural network (SCNN), was developed in this study. The ant colony optimization algorithm was applied to optimize the topology of the network. The results of SCNN were compared with the conventional ANN, that is, multilayer perceptron (MLP).

Based on the results, the developed SCNN showed a classification accuracy of 95%.

In this study, a novel neural network (SCNN) was proposed, which was topologically optimized to improve the discrimination power of ANNs. The SCNN accuracy was determined to be 95% in Raman spectroscopy-based breast cancer diagnosis.

Tumor motion is a challenging issue in radiotherapy, which complicates the process of tumor delineation, localization, and dose delivery. External surrogate radiotherapy is one of the available strategies that provides motion dataset for a consistent prediction model to track tumor motion using internal-external markers. Regarding this, the present study was conducted to investigate the effect of implanted fiducial on 3D uniform dose distribution.

For the purpose of the study, a Monte Carlo code was utilized to simulate clip with different dimensions and material structures against four therapeutic beams. Moreover, a combinational clip made of golden and covered by polymethyl methacrylate (PMMA) was proposed to be used with lower dose perturbation. Finally, it was proposed to implant a clip outside tumor volume at specific distances from tumor site to keep dose uniformity on tumor volume. To investigate this issue, the correlation coefficient parameter was calculated as the metric among the motion dataset of tumor and clip.

Based on the results, dose perturbation caused by implanted clip was remarkable at hadron therapy depending on its size and material, mainly at the downstream part of the clip.

As the findings indicated, the golden marker covered with PMMA could remarkably reduce dose perturbation. The most important concern in this domain is the presence of a possible correlation between tumor motion and motion of the clip implanted outside the tumor volume. The results of the correlation coefficient revealed a close relationship between tumor motion and clip motion.

Exposure to ultraviolet (UV) radiation causes oxidative damage and cancer in the epidermis. The thickening of the skin layer seems to be correlated with carcinogenicity. The present study aimed to induce trichoepithelioma, a rare benign skin lesion, in an animal model and investigate the relationship between the radiation dose of UV waves and the thickening of skin layers resulting from high-frequency ultrasound images.

To investigate skin damage process, 25 C57BL6 mice were irradiated with Ultraviolet B-rays (UVB) (5 times a week for 9 weeks) with an energy density of 135, 270, 405, 540, 675, 810, 945, 1080, and 1215 J/m2, from the first week to the ninth week, respectively. The thickness of the skin layer was weekly measured by ultrasound images. The correlation between the thickness of the skin layer and the radiation energy density was analyzed by Pearson correlation analysis.

The thickness of the skin layer demonstrated a significant increase in the 7th week of exposure during the injury process due to UV radiation, as compared to zero-day (P˂0.05). Furthermore, it showed a 38 % increase in the 7th week. The obtained results illustrated a significant correlation coefficient of more than 0.97 between the thickness of the skin layer and the energy density of UV radiation. Microscopic sections in the long-term UV-irradiated group confirmed trichoepithelioma.

As evidenced by the obtained results, prolonged irradiation for 9 weeks induced an animal model of trichoepithelioma.

The most common impact of X-ray is the induction of cancer after chronic exposure. The current study was conducted to investigate the effects of low X-ray doses on some liver functions and proteins among diagnostic technicians working at Kirkuk hospitals, Kirkuk, Iraq. To this purpose, the parameters, such aspartate aminotransferase (AST), alanine aminotransferase (ALT), total protein, albumin, globulin, serum ferritin (s.ferritin), malondialdehyde (MDA), and glutathione (GSH) were measured in this study.

In total, 20 male diagnostic technicians with a mean age of 39.55±10.02 years participated in this study. On the other hand, 20 male healthy controls with a mean age of 39.9±10.29 years were selected from outside of the hospitals. Five ml of blood was taken from each individual (technicians and controls). All parameters were measured with their own techniques.

According to the results, significant increase (p <0.001) was observed in the levels AST, ALT, and s.ferritin; however, there were remarkable decreases in the values of MDA, total protein, albumin, globulin, and GSH (p <0.001) among diagnostic technicians, compared to the control group.

Based on the results, it was revealed that chronic exposure to low X-rays doses from conventional X-ray machine may change significantly the values of ALT, AST, s. ferritin, MDA, total protein, albumin, globulin, and GSH in diagnostic technicians who are exposed to an overdose at their workplace. It is importance to utilize radiation protection tools, hold training courses, and follow up the technicians to reduce the effect of radiation on these individuals.

Today, the use of ionizing radiation in medicine has grown as an important tool for diagnosis and treatment of diseases. However, the harmful effects of radiation should be also considered. Some substances such as lycopene and curcumin can reduce or increase the harmful effects of radiation on humans. So the aim of this study was to evaluate the radioprotective effects of lycopene and curcumin based on the MN assay.

In this study, the effects of lycopene and curcumin on reducing or increasing the harmful effects of radiation were studied using the micronucleus assay. The effects of lycopene (5 μg/mL) and curcumin (5 μg/mL) were evaluated at radiation doses of 2 and 6 Gy.

The results indicated that the simultaneous use of curcumin and lycopene can be radioprotective at low radiation doses (2 Gy; p <0.001) and radiosensitizing at high doses (6 Gy; P>0.05).

Based on the present results, further research using other methods may contribute to our understanding of the effect of simultaneous use of curcumin and lycopene at low and high doses of X-ray radiation.

The left atrial appendage )LAA( occlusion using a purpose-built device is a growing procedure. This study aimed to develop a computer-aided diagnostic system for the recognition of the LAA in echocardiographic images.

The three-dimensional (3D) echocardiographic images of the LAA of 26 patients successfully treated with an LAA occluder were used in this study. A total of 208 3D derived two-dimensional images in the axial plane were derived from each 3D dataset. Then, 562 images in which the LAA boundaries were highly recognizable were selected for this study. The proposed convolutional neural network (CNN) in this study was based on open-source object identification and classification platform compiled under the You Only Look Once algorithm. Finally, 419 and 143 images were used for training and testing the algorithm, respectively.

Algorithm performance on the identification of the LAA region on a set of 143 images was compared to that reported for the traced regions on the same images by an expert in echocardiography using an intersection over the union (IOU) algorithm. The algorithm was able to correctly identify the LAA region in all 143 examined images with an average IOU of 90.7%.

The proposed image-based CNN algorithm in this study showed high accuracy in the recognition of the LAA boundaries in the echocardiographic images. The method can be used in the development of algorithms for the automated analysis of the area of the LAA used for device sizing and procedural planning in the LAA occlusion procedures.

This paper aimed to outline the procedure for determining the activity concentrations of naturally occurring radionuclides (i.e., 226Ra, 232Th, and 40K) in surface soil samples collected from Mazandaran province, Iran.

In total, 61 samples were collected between longitude 50˚ 34′ and 54˚ 10′ east and latitude 35˚ 47′ and 36˚ 35′ north from uncultivated locations of Mazandaran province, Iran. The measurements were performed by the gamma spectrometry system using a High Purity Germanium detector.

The mean levels of 226Ra, 232Th, and 40K were found to be 20 Bqkg-1 (without considering high-level areas), 33 Bqkg-1, and 421 Bqkg-1, respectively. The results were compared with those of different countries across the world. The radiological hazard to the natural radioactivity was assessed by calculating the absorbed dose rate, the radium equivalent activity, the external and internal hazard indices, and the outdoor and indoor annual effective dose rate. The mean radium equivalent without considering three high-level areas was estimated at 100.8 Bqkg-1.

Results indicated that no radiological risk may threat the residents of the areas under study, except for regions near the hot spring in Sadat Shahr and Lavich, Iran. Without considering high-level areas, the mean radium equivalent activity was 100.8 Bqkg-1 that was about 73% lower than the permissible maximum. Moreover, internal and external hazard indices were less than the unit. The mean absorbed dose rate, as well as the outdoor and indoor annual effective dose rates were 48.56 nGyh-1, 238.4 µSv y-1, and 292.6 µSv y-1, respectively.

Low-density bulk metallic glass (BMG) with good structural characteristics has the potential of being used for structural radiation shielding purposes. This study was conducted on two new low-density titanium (Ti)-based BMGs (i.e., Ti32.8Zr30.2Ni5.3Cu9Be22.7 and Ti31.9Zr33.4Fe4Cu8.7Be22) to investigate their photon and fast neutron shielding capacities.

The mass attenuation coefficients, half-value layers, effective atomic numbers, and exposure buildup factors of the two BMGs were calculated at the photon energy values of 15 keV and 15 MeV. Computation of mass attenuation coefficients and effective atomic numbers was accomplished using the XCOM and auto-Zeff software, respectively. In addition, the geometric progression procedure-based computer code EXABCal was used for calculating the exposure buildup factors of BMG. The fast neutron removal cross-sections were also calculated for the two BMGs. The calculated photon and fast neutron shielding parameters for BMGs were compared with those of lead (Pb), heavy concrete, and some recently developed glass shielding materials and then analyzed according to their elemental compositions.

The results showed that though Pb had a better photon shielding capacity, Ti-BMG attenuated photons better than heavy concrete. Furthermore, BMG had a higher neutron removal cross-section, compared to heavy concrete and some recently developed glass shielding materials. The neutron removal cross-sections of Ti32.8Zr30.2Ni5.3Cu9Be22.7 and Ti31.9Zr33.4Fe4Cu8.7Be22 were obtained as 0.1663 and 0.1645 cm-1,respectively.

his study revealed that Ti-based BMG with high strength and low density have potential applications in high-radiation environments, particularly in nuclear engineering for source and structural shielding.