Iranian Journal of Medical Physics
Volume:16 Issue: 6, Nov-Dec 2019

Nuclear accidents release large quantities of radioactive materials into the environment. Iodine-131 and cesium-137 are two radionuclides released during nuclear accident, which can pose the greatest cancer risks. These radionuclides can be moved to other areas through rain and wind. The aim of this study was to develop efficient and economical biological methods for the absorption of water-soluble radionuclides released after a nuclear accident.
The exposure of the algae to an aqueous solution of I-131 radionuclide was performed for 1, 2, and 3 h. The concentration activities of the samples were 27 μCi/ml and 270 μCi/ml. After the removal of the alga by centrifuging, the activities of the sample solutions were measured using a calibrated dose calibrator. The measured activities at the mentioned periods of time were statistically significant for both groups (P<0.05).
The obtained results of the current study revealed that the activity of radioiodine-131 decreased 1, 2, and 3 h after adding algae, compared to the control group at the same time (21.8, 32.33, 39.84 for 27 μCi/ml and 15.38, 21.53, and 30% for 270 μCi/ml, respectively). Furthermore, radioactive iodine is absorbed very well with this type of algae.
It can be concluded that Dunaliella salina can be used for the decontamination of radioiodine. This method can play a significant role in the decontamination of hazardous radioiodine after nuclear accidents.

The postmastectomy radiotherapy uses bolus to improve the coverage close to the skin; however, it needs to be removed in case of severe skin toxicity. This study investigated the effect of bolus parameters (i.e., frequency and thickness) for the superposition algorithm on skin dose in postmastectomy three-dimensional conformal radiotherapy (3D-CRT).
The present study was carried out ona total of 22 patients. First, all the plans were calculated without using bolus. Then, the plans were recalculated using different bolus frequencies (5, 10, 15, 20, 25) and thicknesses (0.5 and 1 cm). To evaluate the dose delivered to the skin, a 2-mm thick skin was profiled, and statistical analysis was performed by studying the dosimetric parameters (i.e., minimum, mean, and maximum) of chest wall skin.
The superficial coverage of planning target volume (PTV) was better by using bolus. In the case of skin, the bolus thickness had a significant impact on the minimum and mean doses for all bolus frequencies , while there was no significant effect on the maximum before 20-bolus frequency. The bolus frequency increase demonstrated a significant difference on all dosimetric parameters of the skin , except the maximum showed no significant difference between 0 and 5-bolus frequencies .
The obtained results indicated that the bolus use had generally a significant effect on the chest wall skin dosimetric parameters depending on bolus frequency and thickness. Therefore, the choice of bolus frequency and bolus thickness can affect the clinical decisions in certain cases.

In radionuclide imaging, object scatter is one of the major factors leading to image quality degradation. Therefore, the correction of scattered photons might have a great impact on improving the image quality. Regarding this, the present study aimed to determine the main and sub-energy windows for triple energy window (TEW) scatter correction method using the SIMIND Monte Carlo simulation code in Gadolinium-159 (Gd-159) imaging.
The energy window was set for various main energy window widths (i.e., 10%, 15%, and 20%) and sub-energy window widths (i.e., 3 and 6 keV).Siemens Medical System Symbia fitted with a high-energy collimator was used with Gd-159 point source positioned at seven locations inside the cylindrical water phantom. A comparison was made between the true primary to total ratio (calculated by SIMIND) and the primary to total ratio estimated using TEW method.
The findings of this study showed that 20% of the main energy windows with 3 and 6 keV sub-energy windows were optimal for the implementation of the TEW method in Gd-159.
According to the results, the optimal energy windows for Gd-159 scintigraphy were the sub-energy windows of 3 and 6 keV. These findings could be helpful in the quantification of Gd-159 imaging. In radio-nuclides imaging, object scatter is one of major factors which leads to degradation of image quality. Therefore, the correction of scattered photons has a great impact to improve the image quality. The aim of this work was to determine the main and sub-energy windows for the triple energy window (TEW) scatter correction method using Monte Carlo simulation SIMIND code for Gadolinium-159 (Gd-159) imaging. Energy window was set for various main energy window width (10,15 and 20%) and sub energy window width (3 and 6 keV). Siemens Medical System Symbia fitted with High Energy collimator (HE) was imaged with Gd-159 point source positioned at seven locations inside cylindrical water phantom. The true primary to total ratio (calculated by SIMIND) and the primary to total ratio estimated using TEW method were compared. A 20% of main energy window with 3 and 6 keV sub-energy windows were found to be optimal for implementation of the TEW method in Gd-159. The obtained results provide the optimal energy window for Gd-159 scintigraphy data and will aid the quantification of Gd-159 imaging.

In radiotherapy, the bolus is often used while treating the tumor under the uneven surfaces of the patients for correcting the anatomical irregularities and increasing skin dose. Wet cotton and wet gauze are still used in developing countries, since the use of wet cotton and wet gauze has certain disadvantages, there is a need for transparent bolus which should be similar to a universally accepted bolus in terms of properties with a lower cost (50% less expensive).
The present study was conducted to investigate the characteristics of transparent bolus (Senflab) material, such as transmission factor, percentage depth dose (PDD), stability over time and high dose, homogeneity and transparency using 6 and 15 MV photons beam and 12, 15, and 18 MeV electrons beam. Moreover, the new bolus material was compared with those of the commercially available Superflab and RW3 slab.
The percentage difference in the transmission factor of Senflab was less than ±1.9%, compared with Superflab and RW3. For PDD, the percentage difference was ±2.88% and ±1.26% for photons and electron beams, respectively. The performance of bolus remained constant both physically and dosimetrically after higher dose exposure. The percentage standard deviation was 0.0002% for a period of one month, and 0.0003% for the homogeneity. The transparency of the bolus material was good enough to display the set radiation treatment field.
This study shows the suitability of the new bolus for routine use in radiotherapy.

Smokers and non-smokers are at the risk of developing lung cancer when exposed to alpha rays as a result of the relatively low levels of radium and radon that may be present in different tobacco species. There is a great interest in studies and research on the radionuclides in narghile tobacco emitting alpha particles to know the relationship between smoking narghile and cancer, especially lung cancer. This study was conducted to measure the alpha rays in 30 different narghile samples in the markets of Iraq. Radon concentrations were determined using time-tested passive radio doses containing CR-39 solid-state pathway detectors. The radon concentrations in samples varied from27.44±4.4 Bq/m3 to 214.61±18.1 Bq/m3 with the mean value of 65.60±41.04 Bq/m3. The annual effective dose varies from 0.69±0.09 mSv/y to 5.41±2.20 mSv/y with the mean value of 1.64±1.03 mSv/y. The lung cancer risk cases per year vary from 12.46±2.11 to 97.45±7.34 with the mean value of 29.77±18.63 per million people. The effective radium content ranged between 0.054Bq/kg and 0.425Bq/kg with the mean value of 0.131 of Bq/kg, while the radon emission values for the mass and surface units ranged from 0.410 to 3.212 with the mean of 0.996 mBq/kg.h and 9.040 to 70.703 with the mean value of 21.943mBq/m2.h, respectively. The results of the study showed that alpha rays are within the internationally accepted limits and presently do not pose a threat to human health and life in terms of the radiation activity of the investigated narghile tobacco species in this study.

Dental panoramic radiography (DPR) is one of the most frequent diagnostic X-ray procedures, the application of which is currently on a growing trend. During DPR, several radiosensitive tissues, such as the lens of the eyes, parotid gland, and thyroid gland, contribute to the radiation field, and it is necessary to monitor their received dose. The aim of this study was to evaluate the radiation dose to the lens of the eyes, parotid gland, and thyroid gland in patients undergoing DPR at Lorestan Province, Western Iran.
This cross-sectional study was performed on 180 patients of both genders referred to DPR at two most crowded hospitals in Khorramabad, Iran, namely Tamin-e Ejtemaei (TE) and Shohada-ye Ashayer (SA) hospitals. The radiation dose measurements were carried out using LiF (Mg, Cu, P) thermoluminescent dosimeters (TLDs). To measure the absorbed dose received by the lens of the eyes, parotid gland, and thyroid gland in each patient, five sets of three TLDs, wrapped in a thin plastic bag, were positioned over each eyelid and the anatomical position of the parotid and thyroid glands. The TLDs were read within 24 h of exposure.
The mean absorbed dose received by the lens of the eyes, parotid gland, and thyroid gland were obtained as 155, 160, and 72 µGy for the TE Hospital, respectively. These values were obtained as l24, 558, and 56 µGy, respectively, for the SA Hospital. The results revealed a statistically significant difference between the organs located outside and inside the primary beam in terms of the absorbed dose (P<0.001).
The absorbed dose received by the lens of the eyes and thyroid gland was generally lower than the values reported in similar studies. Nevertheless, the absorbed dose received by the parotid gland in the SA Hospital exceeded the recommended dose reference level of 400 µGy in DPR.

Myocardial perfusion imaging is a nuclear medicine imaging method that is used to detect coronary artery diseases. One of the main sources of error in this imaging method is the detection of Compton scattered photons in the photopeak energy window used for data acquisition. This results in the degradation of the image contrast, and therefore decreases the diagnostic accuracy.

In this study, the efficiency of dual-energy window (DEW) correction method regarding the reduction of the undesirable influence of scattering was investigated using the images acquired from the 3D-NCAT simulated phantom, and a group of patients (18 males and 27 females) in both rest and stressful situations. To evaluate the scatter correction method, the image contrasts are calculated before and after applying the scatter correction.

The results obtained from this study indicated that the calculated image contrasts enhanced by applying the scatter correction in both simulation and patient studies. In the simulation study, the relative values of increase in image contrast are about 10.15% and 12.58% when using a k value equal to 0.5, and the linear fitting method, respectively. In the patient study, the relative values of increase in image contrasts regarding the rest and stress situations were about 13.63% and 10.84% for females and 12.03% and 10.56% for males, respectively.

The utilization of the DEW method for scatter correction of cardiac SPECT images results in an increase in the image contrast and the improvement of the image quality.

Medical workers in the departments of radiology, computed tomography, nuclear medicine, and radiotherapy are always exposed to ionizing radiations. Complete blood count (CBC) test is commonly used to monitor the health of radiation workers. The aim of this study was to evaluate the hematological parameters of radiation workers of Isfahan, Iran, and reveal the effectiveness of the CBC tests in the prediction of the radiation effects on the health of such workers.
The current study was conducted on 160 radiation workers and 103 healthy people using CBC tests. To obtain the main aim of the study the obtained results of the two groups were compared in terms of blood parameters.
The hematocrit in the male radiation workers was estimated at 45.98±3.00, which was significantly higher than that of the control group (44.33±2.41%, P<0.05). However, mean corpuscular hemoglobin concentration and platelets counts were of lower levels in radiation workers, compared to the control group (P<0.05). The lymphocyte percentage of female radiation workers was 33.78±7.47%, which was significantly lower than that of the controls (37.84±8.97%, P<0.05).
The CBC test can be used to follow up on the overall health status of radiation workers. However, it is essential to perform complementary methods, such as chromosomal changes, cytokines, and interleukins evaluation, for the early detection of radiation effects.