- Détails du magazine
- Première publication
- 30 Dec 2008
- Période de publication
- 4 fois par an
- Accès libre
Pages: 61 - 67
Drawing blood and injecting drugs are common medical procedures, for which accurate identification of veins is needed to avoid causing unnecessary pain. In this paper, we propose a low-cost system for the detection of veins. The system emits near-infrared radiation from four light-emitting diodes (LEDs), with a charge-coupled device (CCD) camera located in the middle of the LEDs. The camera captures an image of the palm of the hand. A series of digital image-processing techniques, ranging from image enhancement and increased contrast to isolation using a threshold limit based on statistical properties, are applied to effectively isolate the veins from the rest of the image.
- NIR LEDs
- CCD camera
- palm vein
- Wiener filter
- Accès libre
A numerical study on the effect of conductivity change in cell kill distribution in irreversible electroporation
Pages: 69 - 76
Introduction: irreversible electroporation (IRE) is a tissue ablation technique and physical process used to kill the undesirable cells. In the IRE process by mathematical modelling we can calculate the cell kill probability and distribution inside the tissue. The purpose of the study is to determine the influence of electric conductivity change in the IRE process into the cell kill probability and distribution.
Methods: cell death probability and electric conductivity were calculated with COMSOL Multiphysics software package. 8 pulses with a frequency of 1 Hz, pulse width of 100 µs and electric field intensity from 1000 to 3000 V/Cm with steps of 500 V/Cm used as electric pulses.
Results: significantly, the electrical conductivity of tissue will increase during the time of pulse delivery. According to our results, electrical conductivity increased with an electric field intensity of pulses. By considering the effect of conductivity change on cell kill probability, the cell kill probability and distribution will change.
Conclusion: we believe that considering the impact of electric conductivity change on the cell kill probability will improve the accuracy of treatment outcome in the clinic for treatment with IRE.
- Finite Element Analysis
- electric conductivity
- pulsed electric field
- Accès libre
Attenuation parameters of polyvinyl alcohol-tungsten oxide composites at the photon energies 5.895, 6.490, 59.54 and 662 keV
Pages: 77 - 85
The growing demand for lightweight, non-toxic and effective X- and γ-ray shielding materials in various fields has led to the exploration of various polymer composites for shielding applications. In this study, tungsten filled polyvinyl alcohol (PVA) composites of varying WO3 concentrations (0 - 50 wt%) were prepared by solution cast technique. The structural, morphological, and thermal properties of the prepared composite films were studied using X-ray diffraction technique (XRD), Scanning electron microscopy (SEM) and Thermogravimetric analysis (TGA). The AC conductivity studies showed the low conductivity property of the composites. The X-ray (5.895 and 6.490 keV) and γ-ray (59.54 and 662 keV) attenuation studies performed using CdTe and NaI(Tl) detector spectrometers revealed a noticeable increase in shielding efficiency with increase in filler wt%. The effective atomic number (Zeff) calculated by the direct method agreed with the values obtained using Auto-Zeff software. The % heaviness showed that tungsten filled polyvinyl alcohol composites are lighter than traditional shielding materials.
- radiation shielding
- tungsten filled polyvinyl alcohol composite
- mass attenuation coefficient
- Accès libre
Determination of radiation doses to the skin due to 238U and 232Th series for the therapeutic application in the Merzouga sand baths
Pages: 87 - 96
In this work, we used CR-39 and LR-115 type II solid-state nuclear track detectors to measure 238U, 232Th,222Rn and 220Rn concentrations in Merzouga sand. The measured concentrations of 238U and 232Th in the studied sand samples vary from (332.59±16.62) mBq·cm−3 to (335.54±20.13) mBq·cm−3 and (80.43±4.02) mBq·cm−3 to (84.75±5.08) mBq·cm−3, respectively. We evaluated the radiation doses to the skin from the application of different sand baths by the patients by using a model based on specific alpha-dose and alpha-particle residual energy concepts. The maximum total equivalent dose to the skin due to the 238U and 232Th series from the cutaneous application of different sand baths by patients was found equal to (148.12±11.85) µSv y−1cm−2
- Solid Nuclear track detectors
- sand baths
- environmental radioactivity
- U and Th concentrations
- radiation dose assessment to skin
- Accès libre
Radiological and health hazards resulting from radioactivity and elemental composition of some soil samples
Pages: 97 - 110
Inspection of the radioactivity level in the soil is very important for human health and environmental protection. This study aims at evaluating the radiological hazards and pollution risks related to natural radionuclides and elements in the selected soil samples. Ten samples of soil were collected from different sites of Aurangabad-India and the level of radioactivity was measured using gamma-ray spectrometry with NaI (Tl) detector. Furthermore, the Physico-chemical properties such as pH, organic matter, electrical conductivity, moisture, soil texture, etc., and elemental composition of soils have been decided on using various standard techniques. The mean concentrations of 226Ra, 232Th, and 40K were 8.178, 17.408, and 96.496 Bq/kg, respectively, which are lower than the global average values of 35, 30, and 400 Bq/kg, respectively (UNSCEAR, 2000). The radiological hazard indices such as radium equivalent, absorbed dose, annual effective dose, internal index, external index, gamma index, excess lifetime cancer risk, etc., were calculated to assess the radiation hazards and compared with internationally recommended values which found to be lower than the permissibility limits.
The Pearson correlation was applied to determine the existing relationship between radionuclides and radiological health hazard parameters, as well as with the physicochemical properties of the soil samples. The major and trace elements presented in soils were measured and their mean concentration was ranked in the formed order (Mg>Na>Ca>K>N>Mn>Fe>P>Zn>Cu). The pollution risk parameters (Geo-accumulation index, contamination factor, degree of contamination, pollution load index, and potential ecological risk index) related to the elements in the samples were assessed and results shown that the soils under study are unpolluted with the measured elements. Generally, the radioactivity levels and pollution risks indices in the soils of the study area are within the permissible safety limits and do not cause any significant health threat to humans. Thus, the presented data provide a general background of the detectable radionuclides for the study area and can be helpful in the future as a reference for more extensive studies in the same field.
- health hazards
- gamma spectrometry
- physico-chemical properties
- absorbed dose
- Accès libre
Pages: 111 - 117
The purpose of the study was to analyze single fraction Gamma Knife stereotactic radiosurgery (SRS) for uveal melanoma (UM). In the treatment of UMs, the dose distribution exhibited by an irregular eye surface has more calculation uncertainty. A tissue-equivalent bolus was placed on the left eye surface of a human head-shaped phantom. It was assumed that the treated eye is fixed using retrobulbar anesthesia and suture on extraocular muscles for phantom study. Leksell stereotactic frame was fixed around phantom’s head and the stereotactic computed tomography (CT) was performed. Two sets of scans were acquired (a) without bolus and (b) with a bolus of 1.0 cm thickness. These scans were transferred into a treatment planning system (TPS). The skull contouring was performed using stereotactic CT images. The target, visual pathways, and eye lens were delineated in stereotactic CT space created on TPS. A clinical relevant plan was designed on the CT study set “a” to deliver a radiation dose of 30Gy at tumor margin. The plan superimposed over CT study set “b” and compiled for convincing treatment strategy. The tumor coverage was 95% at 50% prescription isodose line. The conformity index, selectivity and the gradient index were 1.27, 0.80 and 3.28 respectively. The left optic nerve and eye lens received a maximum dose of 11.1 Gy and 11.0 Gy respectively. The treatment plan overlay showed similar planning indices and critical organ doses. The plan comparison showed: an irradiated volume received the radiation dose > 15 Gy varies < 1.0% whereas the volume received < 15 Gy were larger (> 1.0%) in the study set “b”. The distant lateral points from the target volume which describe the phantom’s eyelid showed a radiation dose of 3.2 Gy - 2.5 Gy. The doses to these points were misled and ignored in the CT study set “a”. The eye bolus provides better dosimetric information in the estimation of low dose areas which is commonly misled on TPS in SRS planning for UMs.
- Gamma Knife
- stereotactic radiosurgery
- uveal melanoma
- Accès libre
Pages: 119 - 125
Background: Ionizing radiation has an indispensable role in diagnostic radiology and clinical treatments. Apparently, medical exposure in diagnostic radiology pertains to be the preeminent man-made source of radiation.
Objective: The aim of the present scientific study is to calculate the Entrance Surface Dose (ESD) and Effective Dose (ED) in digital radiography in Mazandaran province.
Materials and methods: The study was performed on 3600 patients in digital X-ray rooms 15 hospitals and the required data were collected from two age groups (10>15 years and adults) in each projection. Based on the results of this study, ESD and ED were calculated for skull (PA), skull (lateral), cervical spine (AP), cervical spine (lateral), chest (PA), chest (lateral), abdomen (AP), lumbar spine (AP), lumbar spine (lateral), pelvis (AP), thoracic spine (AP) and thoracic spine (lateral) examinations. It was calculated using PCXMC software (version 2.0).
Results: In this study, mean ESDs for the 10-15 year group varied from 0.97±0.21 mGy to 3.62±1.38 mGy for chest (PA) and lumbar spine (lateral), respectively. For the adult group varied from 1.05±0.31 to 3.85±1.44 for cervical spine (AP) and lumbar spine (lateral), respectively. And also ED value was from in the range of 10.40 µSv to 378.46 µSv for skull (PA) 10-15 year group and abdomen adults, respectively
Conclusion: This survey revealed a significant variation in the radiation dose of digital radiology examinations among hospitals in Mazandaran province. Application of a dose reference level (DRL) could be an optimization procedure for reducing the patient’s dose in Mazandaran province.
- diagnostic radiology
- patient dose
- dose reference level
- entrance surface dose
- effective dose