Showing papers in "Iranian Journal of Medical Physics in 2012"
TL;DR: The results indicate that the proposed combinatorial model produces optimum and efficacious parameters in comparison to other parameters and can improve the capability and power of globalizing the artificial neural network.
Abstract: Introduction This study is an effort to diagnose breast cancer by processing the quantitative and qualitative information obtained from medical infrared imaging. The medical infrared imaging is free from any harmful radiation and it is one of the best advantages of the proposed method. By analyzing this information, the best diagnostic parameters among the available parameters are selected and its sensitivity and precision in cancer diagnosis is improved by utilizing genetic algorithm and artificial neural network. Materials and Methods In this research, the necessary information is obtained from thermal imaging of 200 people, and 8 diagnostic parameters are extracted from these images by the research team. Then these 8 parameters are used as input of our proposed combinatorial model which is formed using artificial neural network and genetic algorithm. Results Our results have revealed that comparison of the breast areas; thermal pattern and kurtosis are the most important parameters in breast cancer diagnosis from proposed medical infrared imaging. The proposed combinatorial model with a 50% sensitivity, 75% specificity and, 70% accuracy shows good precision in cancer diagnosis. Conclusion The main goal of this article is to describe the capability of infrared imaging in preliminary diagnosis of breast cancer. This method is beneficial to patients with and without symptoms. The results indicate that the proposed combinatorial model produces optimum and efficacious parameters in comparison to other parameters and can improve the capability and power of globalizing the artificial neural network. This will help physicians in more accurate diagnosis of this type of cancer.
32 citations
TL;DR: It was showed that increasing J/Φ, as a measure of beam directionality, leads to improvement of beam performance and survival of healthy tissues surrounding the tumor, and the proposed system based on D-T neutron source, which is suitable for in-hospital installations, satisfies all in-air parameters.
Abstract: Introduction BNCT is an effective method to destroy brain tumoral cells while sparing the healthy tissues. The recommended flux for epithermal neutrons is 109 n/cm2s, which has the most effectiveness on deep-seated tumors. In this paper, it is indicated that using D-T neutron source and optimizing of Beam Shaping Assembly (BSA) leads to treating brain tumors in a reasonable time where all IAEA recommended criteria are met. Materials and Methods The proposed BSA based on a D-T neutron generator consists of a neutron multiplier system, moderators, reflector, and collimator. The simulated Snyder head phantom is used to evaluate dose profiles in tissues due to the irradiation of designed beam. Monte Carlo Code, MCNP-4C, was used in order to perform these calculations. Results The neutron beam associated with the designed and optimized BSA has an adequate epithermal flux at the beam port and neutron and gamma contaminations are removed as much as possible. Moreover, it was showed that increasing J/Φ, as a measure of beam directionality, leads to improvement of beam performance and survival of healthy tissues surrounding the tumor. Conclusion According to the simulation results, the proposed system based on D-T neutron source, which is suitable for in-hospital installations, satisfies all in-air parameters. Moreover, depth-dose curves investigate proper performance of designed beam in tissues. The results are comparable with the performances of other facilities.
18 citations
TL;DR: This phantom could be used with a range of radionuclide doses in simulation situations such as cold, hot, and background uptakes for the assessment of detection characteristics when a new similar clinical SPECT procedure is being simulated.
Abstract: Introduction Quality control is an important phenomenon in nuclear medicine imaging. A Jaszczak SPECT Phantom provides consistent performance information for any SPECT or PET system. This article describes the simulation of a Jaszczak phantom and creating an executable phantom file for comparing assessment of SPECT cameras using SIMIND Monte Carlo simulation program which is well-established for SPECT. Materials and Methods The simulation was based on a Deluxe model of Jaszczak Phantom with defined geometry. Quality control tests were provided together with initial imaging example and suggested use for the assessment of parameters such as spatial resolution, limits of lesion detection, and contrast comparing with a Siemens E.Cam SPECT system. Results The phantom simulation was verified by matching tomographic spatial resolution, image contrast, and also uniformity compared with the experiment SPECT of the phantom from filtered backprojection reconstructed images of the spheres and rods. The calculated contrasts of the rods were 0.774, 0.627, 0.575, 0.372, 0.191, and 0.132 for an experiment with the rods diameters of 31.8, 25.4, 19.1, 15.9, 12.7, and 9.5 mm, respectively. The calculated contrasts of simulated rods were 0.661, 0.527, 0.487, 0.400, 0.23, and 0.2 for cold rods and also 0.92, 0.91, 0.88, 0.81, 0.76, and 0.56 for hot rods. Reconstructed spatial tomographic resolution of both experiment and simulated SPECTs of the phantom obtained about 9.5 mm. An executable phantom file and an input phantom file were created for the SIMIND Monte Carlo program. Conclusion This phantom may be used for simulated SPECT systems and would be ideal for verification of the simulated systems with real ones by comparing the results of quality control and image evaluation. It is also envisaged that this phantom could be used with a range of radionuclide doses in simulation situations such as cold, hot, and background uptakes for the assessment of detection characteristics when a new similar clinical SPECT procedure is being simulated.
14 citations
TL;DR: According to the results of this study and other properties such as flexibility and harmlessness, it seems that ethyl methacrylate is a suitable material to be used as bolus in radiotherapy.
Abstract: Introduction Bolus is a soft and resilient material which is used for increasing skin dose or to even out the irregular patient contour. The main property of various materials used presently as bolus is the water-equivalent electron density. Ethyl methacrylate is used as a soft-liner in dentistry and its physical and chemical properties are proved to be nontoxic for human body. The goal of this study was to assess the feasibility of using this material as bolus in radiotherapy and also evaluating some parameters such as mass, electron densities, and transmission factors. Materials and Methods Computed tomography data from the sample material were acquired to assess mass and electron densities with various techniques (mA and kVp). Circular ROIs were delineated on CT DICOM images and densities were calculated using CT numbers. Transmission factors were calculated for 6 and 18 MV. Results Evaluation of our results are evident that showed that mass and electron densities of ethyl methacrylate are similar to those of water and soft tissue. Furthermore, transmission factors are close to those of water. Conclusion According to the results of this study and other properties such as flexibility and harmlessness, it seems that ethyl methacrylate is a suitable material to be used as bolus in radiotherapy.
13 citations
TL;DR: 99mTc-ceftriaxone may provide a promising candidate as a targeting radiopharmaceutical for imaging infectious foci due to Staphylococcus aureus in nuclear medicine because of its ease of conjugation method, high labeling efficiency, and high uptake in the infected muscle.
Abstract: Introduction Bacterial infection is one of the major causes of morbidity and mortality especially in developing countries. Nuclear medicine has an important role in helping the diagnosis of deep-seated infections by developing more specific radiopharmaceuticals. The aim of this study was to evaluate 99mTc-labeling ceftriaxone as a new radiopharmaceutical for Staphylococcus aureus infection imaging in nuclear medicine. Materials and Methods Radiolabeling of ceftriaxone was carried out by adding 370 MBq of 99mTc to 10 mg of ceftriaxone in the presence of 50 µg of SnCl2.2H2O at pH=5. The radiochemical purity and stability tests at room temperature and human blood serum were evaluated with ITLC. Intramuscular infection was induced by injection of Staphylococcus aureus into the left thigh muscle of the mice. The biodistribution of 99mTc-ceftriaxone was studied in normal and infected mice at various times post-injection. Results Radiochemical purity of the product was 94.5±5.4% with a good stability at room temperature and human serum, 80.6% and 71.2% after 24 h, respectively. The biodistribution studies showed the localization of 99mTc-ceftriaxone at the site of infection with high sensitivity without any significant accumulation in vital organs. Conclusion Due to the ease of 99mTc-ceftriaxone conjugation method, high labeling efficiency, and high uptake in the infected muscle, it may provide a promising candidate as a targeting radiopharmaceutical for imaging infectious foci due to Staphylococcus aureus in nuclear medicine.
12 citations
TL;DR: The discrepancies observed between the results obtained from heterogeneous and homogeneous phantoms suggest that Leksell Gamma Knife planning system (LGP) predictions which assume the target as a homogeneous material must be corrected in order to take care of the air- and bone-tissue inhomogeneities.
Abstract: Introduction Polymer gel dosimeters offer a practical solution to 3D dose verification for conventional radiotherapy as well as intensity-modulated and stereotactic radiotherapy. In this study, EGSnrc calculated and PAGAT polymer gel dosimeter measured dose profiles from single shot irradiation with 18 mm collimator of Gamma Knife in homogeneous and inhomogeneous phantoms were compared with each other. Materials and Methods The head phantom was a custom-built 16 cm diameter plexiglas sphere. Inside the phantom, there were two cubic cutouts for inserting the gel vials and inhomogeneities. Following irradiation with the Gamma Knife unit, the polymer gel dosimeters were scanned with a 1.5 T MRI scanner. For the purpose of simulation the simplified channel of 60Co source of Gamma Knife BEAMnrc and for extracting the 3D dose distribution in the phantom, DOSXYZnrc codes were used. Results Within high isodose levels (>80%), there are dose differences higher than 7%, especially between air inserted and PTFE inserted phantoms, which were obtained using both simulation and experiment. This means that these values exceed the acceptance criterion of conformal radiotherapy and stereotactic radiosurgery (i.e., within some isodose levels, less than 93% of prescription dose are delivered to the target). Conclusion The discrepancies observed between the results obtained from heterogeneous and homogeneous phantoms suggest that Leksell Gamma Knife planning system (LGP) predictions which assume the target as a homogeneous material must be corrected in order to take care of the air- and bone-tissue inhomogeneities.
10 citations
TL;DR: Agaricus bisporus cultivated edible mushroom in Tehran province- Iran were collected from 7 farms by two HPGe detectors as discussed by the authors, and the specific activity of 226Ra, 228Ra, 137Cs, 40K and 235U of the samples were measured.
Abstract: Introduction Natural and man made radioactive sources exist in our environment they can enter into our food chains. One of these is the soil-mushroom-human chain. High level doses of natural radiation can cause hazards to humans. Materials and Methods Samples of Agaricus bisporus cultivated edible mushroom in Tehran province- Iran were collected from 7 farms. Specific activity of 226Ra, 228Ra, 137Cs, 40K and 235U of the samples were measured by two HPGe detectors. Results Specific activity of 226Ra, 228Ra, 137Cs and 40K in the edible mushroom samples were equal to 0.06 ± 0.03 - 0.7 ± 0.2 Bq kg-1 dry, 1.4 ± 0.7 Bq kg-1 dry, 0.1 ± 0.03- 0.3 ± 0.1 Bq kg-1dry and 920 ± 400 - 1370 ± 900 Bq kg-1dry , respectively. Conclusion As the measured concentrations of the radionuclides of interest are close or lower than MDA (Minimum Detectable Activity). Consumption of the mushrooms would impose no health consequences to the consumers.
9 citations
TL;DR: In this article, the authors evaluated changes in the alpha band particularly alpha-1 of frontal and central areas of the head, when several areas were exposed simultaneously to magnetic field and found that increased blood perfusion in some areas is probably the cause of this reduction which requires more research.
Abstract: Introduction Increase in alpha band is observed when blood perfusion in frontal area of head decreases. The present study evaluated some changes in the alpha band particularly, alpha-1 of frontal and central areas of the head, when several areas were exposed simultaneously to magnetic field. Materials and Methods Five points of head (F3, F4, Cz, T3, and T4) of twenty healthy male participants were exposed to magnetic fields simultaneously by five separate coils at different frequencies of 45, 17, 10, 5, and 3 Hz, in five separate sessions. The magnetic field intensity was 100 µT at 1.5 cm distance from the coil. At the end, relative powers over these areas in common frequency and alpha-1 bands were evaluated by paired t-test. Results Significant reduction (p<0.05) in alpha-1 band was observed by exposure of local ELF magnetic field at frequencies of higher than 5 Hz in closed-eye. These reductive effects were enormous at 5 and 45 Hz frequency. Conclusion Observed reduction in alpha-1 band may be due to the influence of magnetic field exposure on production centers of alpha band, particularly the thalamus. Hence, increased blood perfusion in some areas is probably the cause of this reduction which requires more research.
8 citations
TL;DR: The various steps of planning and quality control of Siemens linear accelerators for IMRT, using film dosimetry have been acceptable according to the standard protocols and possible sources of errors are discussed.
Abstract: Introduction Intensity Modulated Radiation Therapy (IMRT) has made a significant progress in radiation therapy centers in recent years. In this method, each radiation beam is divided into many subfields that create a field with a modulated intensity. Considering the complexity of this method, the quality control for IMRT is a topic of interest for researchers. This article is about the various steps of planning and quality control of Siemens linear accelerators for IMRT, using film dosimetry. This article in addition to review of the techniques, discusses the details of experiments and possible sources of errors which are not mentioned in the protocols and other references. Materials and Methods This project was carried out in Isfahan Milad hospital which has two Siemens ONCOR linear accelerators. Both accelerators are equipped with Multi-Leaf Collimators (MLC) which enables us to perform IMRT delivery in the step-and-shoot method. The quality control consists of various experiments related to the sections of radiation therapy. In these experiments, the accuracy of some components such as treatment planning system, imaging device (CT), MLC, control system of accelerator, and stability of the output are evaluated. The dose verification is performed using film dosimetry method. The films were KODAK-EDR2, which were calibrated before the experiments. One of the important steps is the comparison of the calculated dose with planning system and the measured dose in experiments. Results The results of the experiments in various steps have been acceptable according to the standard protocols. The calibration of MLC and evaluation of the leakage through the leaves of MLC was performed by using the film dosimetry and visual check. In comparison with calculated and measured dose, more that 80% of the points have to be in agreement within 3% of the value. In our experiments, between 85 and 90% of the points had such an agreement with IMRT delivery. Conclusion The EDR2 films are suitable for quality control of IMRT. According to complexity of the quality control for IMRT, the physicists of each center have to develop specific guidelines according to their equipments and limitations. An accurate treatment planning system with capability of inverse planning is an essential need for IMRT. The result of the planning system has to be compared with experiments in various situations.
7 citations
TL;DR: The observed differences over locations and measured doses between this study and the others revealed the dynamic nature of this phenomenon, and necessitate performing the periodic studies in these areas.
Abstract: Introduction The exposure of human beings to ionizing radiation from natural sources is a continuing and inescapable feature of life on earth. For most individuals, this exposure exceeds that from all man-made sources combined. Materials and Methods In this study, the annual effective dose in high level environmental background radiation areas (HLEBRAs) of northern city of Ramsar in Iran was determined. For dosimetry, a gamma radiation dosimeter was used. Measurements were performed in more than 90 points in five districts with HLEBR around and near hot springs. Results In some areas, the annual effective dose from outdoor external gamma radiation in HLEBRAs (30 mSv/y) exceeded the annual effective dose limit for radiation workers. Our results are evident that the population dose from normal background radiation in HLEBRAs is 200 times higher than corresponding values in Ramsar sea shore. To estimate the cosmic ray contribution, dose measurements were performed on the sea surface one km off the sea shore. Conclusion The observed differences over locations and measured doses between this study and the others revealed the dynamic nature of this phenomenon, and necessitate performing the periodic studies in these areas. Moreover, cytogenetic and immunologic researches for studying the long term effects of these high level environmental radiations on the residents of these HLEBRAs are necessary.
6 citations
TL;DR: In this article, a new method is introduced for detection of sperms in microscopic videos, where several frames of these videos are transformed to wavelet sub-bands and bit-related planes are constructed separately, the acquired bit planes are mapped by different local mapping functions and decision is made using continuity and discontinuity of the mapping results.
Abstract: Introduction Automated methods for sperm characterization in microscopic videos have some limitations such as: low contrast of the video frames and possibility of neighboring sperms to touch each other. In this paper a new method is introduced for detection of sperms in microscopic videos. Materials and Methods In this work, first microscopic videos are captured from specimens of human semen. Several frames of these videos are transformed to wavelet sub-bands and bit-related planes are constructed from wavelet sub-bands separately. Finally, the acquired bit planes are mapped by different local mapping functions and decision is made using continuity and discontinuity of the mapping results. Based on the above decision procedure, each region of the microscopic image is assigned to either a sperm or other parts of semen. Results Performance of the proposed method was evaluated by two sets of microscopic videos which have been captured from semen of some infertile men. The first sets belonged to semen specimens with low densities of sperms and the second set belonged to semen specimens with high densities of sperms. Conclusion The results of this study revealed that the proposed method in this work is more efficient in sperm detection and extraction compared with the current approaches in both scenarios. Furthermore, it is evident that for specimens with higher sperm densities the proposed method improved sperm detection also reduces false detection rate considerably.
TL;DR: The present method has the advantage of ease of setup and matching with clinical conditions and the maximum percentage difference of errors for the applied methods is higher than analogous devolves elsewhere reports which could be due to setup parameters such as SSD and field size.
Abstract: Introduction Superficial X-ray therapy is one of the most important treatment methods in radiotherapy especially in the treatment of superficial skin lesions (Up to 300 kVp). Quality of the X-ray beam that can be expressed by Half-Value Layer (HVL), are important indices for this type of treatment effective energy of photon and Homogeneity Coefficient (HC). Materials and Methods The HC of the superficial X-ray machine at 180 kVp was determined by an experimental method and also by simulation (EGSnrc code) and the results were compared. The exposure after the first (0.5 mmCu) and second (1 mmCu) attenuation layers were measured by Farmer dosimeter for three different field sizes. The HC was derived from these experimental data and was compared with corresponding results acquired by EGSnrc code package. The BEAMnrc code was used to transport photons and electrons at exit level of the applicator, DOSXYZnrc code for calculation of absorbed dose in the phantom, and BEAMDP for drawing the output spectra. Results Results showed that the mean percentage difference of errors obtained by experimental data and simulation method is 3.3% and the average energy of output spectra in 180 kVp after passing through filters and attenuation layers increases to 15.3% to 25.4%. Conclusion The maximum percentage difference of errors for the applied methods is higher than analogous devolves elsewhere reports which could be due to setup parameters such as SSD and field size. However, the present method has the advantage of ease of setup and matching with clinical conditions.
TL;DR: The constructed phantom after minor corrections can be used as a method of choice for inter-comparison analysis of TPS and to fill the existing gap for accurate QA program in intracavitary brachytherapy.
Abstract: Introduction Dosimetric accuracy is a major issue in the quality assurance (QA) program for treatment planning systems (TPS). An important contribution to this process has been a proper dosimetry method to guarantee the accuracy of delivered dose to the tumor. In brachytherapy (BT) of gynecological (Gyn) cancer it is usual to insert a combination of tandem and ovoid applicators with a complicated geometry which makes their dosimetry verification difficult and important. Therefore, evaluation and verification of dose distribution is necessary for accurate dose delivery to the patients. Materials and Methods The solid phantom was made from Perspex slabs as a tool for intracavitary brachytherapy dosimetric QA. Film dosimetry (EDR2) was done for a combination of ovoid and tandem applicators introduced by Flexitron brachytherapy system. Treatment planning was also done with Flexiplan 3D-TPS to irradiate films sandwiched between phantom slabs. Isodose curves obtained from treatment planning system and the films were compared with each other in 2D and 3D manners. Results The brachytherapy solid phantom was constructed with slabs. It was possible to insert tandems and ovoids loaded with radioactive source of Ir-192 subsequently. Relative error was 3-8.6% and average relative error was 5.08% in comparison with the films and TPS isodose curves. Conclusion Our results showed that the difference between TPS and the measurements is well within the acceptable boundaries and below the action level according to AAPM TG.45. Our findings showed that this phantom after minor corrections can be used as a method of choice for inter-comparison analysis of TPS and to fill the existing gap for accurate QA program in intracavitary brachytherapy. The constructed phantom also showed that it can be a valuable tool for verification of accurate dose delivery to the patients as well as training for brachytherapy residents and physics students.
TL;DR: In this article, the results of controlled synthesis and application of gold coated Fe3O4/SiO2 nano-shells combined with the optical property of gold for enhancement of selective photothermal interaction with cancerous cells based on the surface plasmon resonance (SPR) Phenomena.
Abstract: Introduction In this study, we describe the results of controlled synthesis and application of gold coated Fe3O4/SiO2 nano-shells combined with the optical property of gold for enhancement of selective photothermal interaction with cancerous cells based on the surface plasmon resonance (SPR) Phenomena. Materials and Methods Magnetite Nano-Particles (MNPs) were prepared by means of co-precipitation. MNPs were modified with a thin layer of Silica using the Stober method. The amino-modified Fe3O4/SiO2 nano-shells were covered with gold colloids as a self-assembeled process. In-vitro assays were performed to determine the effect of apoptosis of the cells based on the cells morphological changes. Results The biologically inert nano-shells (85 nm) with a Magnetite/Silica core and a gold shell were optically activated. A successful laser-hyperthermia based on the thermal effect of surface plasmon resonance was performed using different gold concentrations. The thermal profile effects of laser power are presented as ideal cases of nanoshell-assisted photo-thermal therapy. The thermally-induced cell death has been shown to be dependent on NPs concentration and laser power density. The power densities of 157 and 184 W/cm2 caused complete cell death at the focal point of the laser beam.Cell damage was reduced by decreasing the power density of laser. Also, a larger area of damage on cell culture plates was observed at longer intervals of laser irradiation. Conclusion An optimized laser-(SPR) hyperthermia was obtained using a concentration of gold coated Fe3O4/SiO2 nano-shells concentration=0.1 mg/ml at intensity=157 W/cm2 at 60s.
TL;DR: A 3D reconstruction method based on a combination of GVF algorithm and cubic Bezier Spline curves which was fast and also the final surface was smooth with G2 continuity.
Abstract: Introduction 3D reconstruction of an object from its 2D cross-sections (slices) has many applications in different fields of sciences such as medical physics and biomedical engineering. In order to perform 3D reconstruction, at first, desired boundaries at each slice are detected and then using a correspondence between points of successive slices surface of desired object is reconstructed. Materials and Methods In this study, Gradient Vector Flow (GVF) was used in order to trace the boundaries at each slice. Then, cubic Bezier Spline curves were used to approximate each of obtained contours and to approximate the corresponding points of different contours at successive slices. The reconstructed surface was a bi-cubic Bezier Spline surface which was smooth with G2 continuity. Results Our presented method was tested on SPECT data of JASZCZAK phantom and human's left ventricle. The results confirmed that the presented method was accurate, promising, applicable, and effective. Conclusion Using GVF algorithm to trace boundaries at each slice, and cubic Bezier Spline curves to approximate the obtained rough contours yield to the procedure of reconstruction which was fast and also the final surface was smooth with G2 continuity. So far, some mathematical curves such as spline, cubic spline, and B-spline curves were used to approximate the computed contour during a time consuming procedure. This study presented a 3D reconstruction method based on a combination of GVF algorithm and cubic Bezier Spline curves. There was a good trade-off between speed and accuracy in using cubic Bezier Spline curves which is especially useful for training students.
TL;DR: A brief review of the different types of breast cancer and their treatments using conventional and modern radiotherapy methods, as well as the treatment efficacy and side effects of breast radiotherapy are presented.
Abstract: Breast cancer is the most common cancer in women after skin cancer. In Iran, the presentation age of this cancer is younger than the global average. There are different therapeutic methods for treatment of breast cancer and the choice of treatment depends on the stage of the disease as well as its type and characteristics. Therapeutic methods include surgery, radiotherapy, and systemic therapies, each consisting of a variety of techniques. The two main surgical techniques are lumpectomy and mastectomy. The main systemic methods are biological therapy (immunotherapy), hormone therapy, and chemotherapy. Radiotherapy is mainly categorized into external-beam radiotherapy and brachytherapy. In this paper, we present a brief review of the different types of breast cancer and their treatments using conventional and modern radiotherapy methods, as well as the treatment efficacy and side effects of breast radiotherapy.
TL;DR: It could be observed that examinations that imparted the highest ESD were thorax PA when compared with the established dose level, and these results call for quality assurance program (QAP) in diagnostic X-ray units in Nigeria hospitals.
Abstract: Introduction Radiation exposures from diagnostic medical examinations are generally low and are almost always justified by the benefits of accurate diagnosis of possible disease conditions. Therefore, entrance skin dose (ESD), body organ dose (BOD), and effective dose (ED) from adult patients undergoing routine thorax posterior-anterior (PA) and thorax right lateral (RLAT) were estimated in University Hospital, Port Harcourt, Southern Nigeria. Materials and Methods Totally, 102 patients were considered in this work. Using software packages to carry out ESD, BOD, and ED is a recent resource in dosimetry and is being widely used in hospitals. The software used in this work was CALDose_X 5.0. The software makes use of the technical exposure parameters and the tube output of the X-ray machine. Results The estimated ESD median values were 0.96 and 1.85 mGy for thorax posterior anterior (PA) and right lateral (RLAT), respectively. The highest BOD was in the adrenals (270 µGy) for thorax PA and Liver (263 µGy) for thorax RLAT. Similarly, ED for thorax PA and RLAT examination were 0.068 and 0.107 mGy, respectively. Conclusion It could be observed that examinations that imparted the highest ESD were thorax PA when compared with the established dose level. Therefore, these results call for quality assurance program (QAP) in diagnostic X-ray units in Nigeria hospitals.
Journal Article•
TL;DR: In this article, using the Monte Carlo simulation, the possibility of using the CR-39 detector for direct measurement of Radon and progeny in water is investigated, assuming the random position and angle of alpha particle emitted by Radon, alpha energy and angular spectrum that arrive at the detector, the calibration factor, and the suitable depth of chemical etching of the detector in air and water.
Abstract: Introduction CR-39 detectors are widely used for Radon and progeny measurement in the air. In this paper, using the Monte Carlo simulation, the possibility of using the CR-39 for direct measurement of Radon and progeny in water is investigated. Materials and Methods Assuming the random position and angle of alpha particle emitted by Radon and progeny, alpha energy and angular spectrum that arrive at CR-39, the calibration factor, and the suitable depth of chemical etching of CR-39 in air and water was calculated. In this simulation, a range of data were obtained from SRIM2008 software. Results Calibration factor of CR-39 in water is calculated as 6.6 (kBq.d/m)/(track/cm) that is corresponding with EPA standard level of Radon concentration in water (10-11 kBq/m). With replacing the skin instead of CR39, the volume affected by Radon and progeny was determined to be 2.51 mm for one m of skin area. The annual dose conversion factor for Radon and progeny was calculated to be between 8.8-58.8 nSv/(Bq.h/m). Conclusion Using the CR-39 for Radon measurement in water can be beneficial. The annual dose conversion factor for Radon and progeny was calculated to be between 8.8-58.8 nSv/ (Bq.h/m).
TL;DR: In this paper, an optimized method for obtaining X-ray diffraction patterns of different types from biological tissues was introduced. But the method was not suitable for the detection of cancerous breast tissue.
Abstract: Introduction Individual X-Ray diffraction patterns of biological tissues are obtained via interference of coherent scattering with their electrons. Many scientists have distinguished normal and cancerous breast tissue, bone density, and urinary stone types using the X-Ray diffraction patterns resulting from coherent scattering. The goal of this study was to introduce an optimized method for obtaining X-ray diffraction patterns of different types from biological tissues. Materials and Methods A special tool constituting primary and scatter collimators as well as a sample holder was designed and built. All measurements were done using an X-ray tube, the above-mentioned tool, and a semiconductor detector (HPGe). The X-ray diffraction patterns of some tissue-equivalent materials (acrylic, polyethylene, nylon, and calcium carbonate) and biological tissues (adipose, muscle, and bone) were obtained. Results The corresponding peak positions for adipose, muscle, bone, acrylic, polyethylene, nylon, and calcium carbonate in corresponding X-ray diffraction patterns are located in 1.1±0.055 nm-1, 1.41±0.072, 1.6±0.08 nm-1, 0.8±0.04 nm-1, 1.03±0.051 nm-1, 1.22±0.061 nm-1, and 1.7 ± 0.085 nm-1, respectively. Conclusion The X-ray diffraction patterns obtained in this study were in good agreement relative to previous measurements in terms of peak position. This study introduces a useful setup for extraction of X-ray diffraction patterns from different biological tissues.
TL;DR: It is shown that image distortion can be reduced by decreasing slice thickness and phase encoding steps and the SENSE technique was shown to decrease the amount of image distortion, efficiently.
Abstract: Introduction Echo-planar imaging (EPI) is a group of fast data acquisition methods commonly used in fMRI studies. It acquires multiple image lines in k-space after a single excitation, which leads to a very short scan time. A well-known problem with EPI is that it is more sensitive to distortions due to the used encoding scheme. Source of distortion is inhomogeneity in the static B0 field that causes more geometric distortion in phase encoding direction. This inhomogeneity is induced mainly by the magnetic susceptibility differences between various structures within the object placed inside the scanner, often at air-tissue or bone-tissue interfaces. Methods of reducing EPI distortion are mainly based on decreasing steps of the phase encoding. Reducing steps of phase encoding can be applied by reducing field of view, slice thickness, and/or the use of parallel acquisition technique. Materials and Methods We obtained three data acquisitions with different FOVs including: conventional low resolution, conventional high resolution, and zoomed high resolution EPIs. Moreover we used SENSE technique for phase encoding reduction. All experiments were carried out on three Tesla scanners (Siemens, TIM, and Germany) equipped with 12 channel head coil. Ten subjects participated in the experiments. Results The data were processed by FSL software and were evaluated by ANOVA. Distortion was assessed by obtaining low displacement voxels map, and calculated from a field map image. Conclusion We showed that image distortion can be reduced by decreasing slice thickness and phase encoding steps. Distortion reduction in zoomed technique resulted the lowest level, but at the cost of signal-to-noise loss. Moreover, the SENSE technique was shown to decrease the amount of image distortion, efficiently.
TL;DR: Based on patient dose measurements, thermoluminescent dosimeters were used to obtain the diagnostic reference level arising from panoramic radiography, and third quartile of mean absorbed dose distribution arising from a particular examination has been adopted as diagnostic referencelevel.
Abstract: Introduction The present work describes a study in which, based on patient dose measurements, thermoluminescent dosimeters were used to obtain the diagnostic reference level arising from panoramic radiography. Materials and Methods Ten panoramic units and a sample of 15 patients per X-ray unit were studied. Two thermoluminescent dosimeter chips were placed on the skin surface of selected organs. Mean value of two ESDs was taken as the measured representation dose at the point of interest. Results Mean ESD on parotid glands derived from panoramic radiography was equal to 369.2 µGy. Individual patients' dose value varied from 180.1 to 470.3 µGy. Conclusion Third quartile of mean absorbed dose distribution arising from a particular examination has been adopted as diagnostic reference level. Based on this definition, local diagnostic reference level arising from panoramic radiography of the greater Khorasan province is equal to 400 µG.
TL;DR: The results of the simulations have shown that dose calculation in water phantom would introduce errors in the dose calculation around brachytherapy sources, and it is suggested that the correction factors of different tissues be applied after dose calculations in water phantoms, in order to decrease the errors of brachyTherapy treatment planning.
Abstract: Introduction After the publication of Task Group number 43 dose calculation formalism by the American Association of Physicists in Medicine (AAPM), this method has been known as the most common dose calculation method in brachytherapy treatment planning. In this formalism, the water phantom is introduced as the reference dosimetry phantom, while the attenuation coefficient of the sources in the water phantom is different from that of different tissues. The purpose of this study is to investigate the effects of the phantom materials on the TG-43 dosimetery parameters of the Cs-137 brachytherapy source using MCNP4C Monte Carlo code. Materials and Methods In this research, the Cs-137 (Model Selectron) brachytherapy source was simulated in different phantoms (bone, soft tissue, muscle, fat, and the inhomogeneous phantoms of water/bone) of volume 27000 cm3 using MCNP4C Monte Carlo code. *F8 tally was used to obtain the dose in a fine cubical lattice. Then the TG-43 dosimetry parameters of the brachytherapy source were obtained in water phantom and compared with those of different phantoms. Results The percentage difference between the radial dose function g(r) of bone and the g(r) of water phantom, at a distance of 10 cm from the source center is 20%, while such differences are 1.7%, 1.6% and 1.1% for soft tissue, muscle, and fat, respectively. The largest difference of the dose rate constant of phantoms with those of water is 4.52% for the bone phantom, while the differences for soft tissue, muscle, and fat are 1.18%, 1.27%, and 0.18%, respectively. The 2D anisotropy function of the Cs-137 source for different tissues is identical to that of water. Conclusion The results of the simulations have shown that dose calculation in water phantom would introduce errors in the dose calculation around brachytherapy sources. Therefore, it is suggested that the correction factors of different tissues be applied after dose calculation in water phantoms, in order to decrease the errors of brachytherapy treatment planning.
TL;DR: In this article, a new nanoconjugate made up of Protoporphyrin IX (PpIX) and gold nanoparticles (GNP) was used to provide nucleation sites for cavitation.
Abstract: Introduction When a liquid is irradiated with high-intensity and low-frequency ultrasound, acoustic cavitation occurs and there are some methods to determine and quantify this phenomenon. The existing methods for performing these experiments include sonochemiluminescence (SCL) and chemical dosimetric methods. The particles in a liquid decrease the ultrasonic intensity threshold needed for cavitation onset. In this study, a new nanoconjugate made up of Protoporphyrin IX (PpIX) and gold nanoparticles (GNP), i.e., Au-PpIX was used to provide nucleation sites for cavitation. The nonradiative relaxation time of PpIX in the presence of GNPs is longer than the similar time for PpIX without GNPs. This effect can be used in medical diagnostic and therapeutic applications. Materials and Methods The acoustic cavitation activity was investigated studying integrated SCL signal in the wavelength range of 400-500 nm in polyacrylamide gel phantom containing luminol using a cooled CCD spectrometer at different intensities of 1 MHz ultrasound. In order to confirm these results, a chemical dosimetric method was utilized, too. Results SCL signal level in gel phantom containing Au-PpIX was higher than the other phantoms. These results have been confirmed by the chemical dosimetric data. Conclusion This finding can be related to the existence of PpIX as a sensitizer and GNPs as cavitation nuclei. In other words, nanoparticles have acted as the sites for cavitation and have increased the cavitation rate. Another theory is that activation of PpIX has produced more free radicals and has enhanced the SCL signal level.
TL;DR: The results obtained in this study show that the DLP values obtained in Khorasan Province-Iran are lower than European Commission reference dose levels (EC RDL), in other words performance of all the scanners were satisfactory.
Abstract: Introduction Computed Tomography scans are a very important tool for diagnosis and assessment of response to treatment in the practice of medicine. Ionizing radiation in medical imaging is undoubtedly one of the most powerful diagnostic tools in medicine. Yet, as with all medical interventions, there are potential risks in addition to the clear potential benefits. Materials and Methods Two reference dose quantities have been defined in order to promote the use of good technique in CT. These are weighted CT dose index (CTDIw) in (mGy) for a single slice in serial scanning or per rotation in helical scanning, and dose–length product (DLP) per complete examination (mGy.cm), All measurements were performed using a pencil shaped ionization chamber introduced into polymethyl methacrylate cylindrical brain and body phantoms. This survey was performed on 7 CT scanners in Khorasan Province-Iran. Results DLP for brain, chest, abdomen and pelvic examinations had a range of 255 - 1026, 76-1277, 48-737, 69-854 mGy.cm, respectively. Conclusion The results obtained in this study show that the DLP values obtained in this province are lower than European Commission reference dose levels (EC RDL), in other words performance of all the scanners were satisfactory.
TL;DR: Administration of 5-ALA-GNPs, intensification of ROS generating and the subsequent elevation of photobleaching results in higher treatment efficiency, and more rapid clearance of PpIX has an important implication in clinical application of 5/105 cells that decreases the undesirable effects on healthy tissues.
Abstract: Introduction During the process photodynamic therapy (PDT), bleaching of photosensitizer induced by irradiation and generation of reactive oxygen species (ROS) can provide some information concerning the efficiency of treatment. Since gold nanoparticles (GNPs) have been highlighted as efficient drug delivery systems, in this study, by utilizing GNPs conjugated with 5 aminolevulinic acid (5-ALA-GNPs), the photobleaching of ALA-induced protoporphyrin IX (PpIX) was estimated on a colon carcinoma tumor model. Materials and Methods CT26 tumor models were prepared by subcutaneous injection of 5×105 cells into the right flank of Balb/c inbred mice. To estimate the time required to reach maximum concentration of PpIX in the tumors, the fluorescence signal of PpIX was monitored and PDT was performed by intratumoral injection of 5-ALA-GNPs, GNPs, and 5-ALA in separated groups for 15 min with a cycle of 5 min irradiation and 1 min darkness. The photobleaching rate was calculated from recorded fluorescence signals at the darkness intervals. Results The maximum fluorescence of PpIX was recorded 3 and 5 hr after injection of 5-ALA and 5-ALA-GNPs, respectively. Despite the low PpIX accumulation in tumors receiving conjugate, the photobleaching rate of PpIX was determined to be higher than 5-ALA. The reduction of the fluorescence signal due to 5-ALA-GNPs clearance was higher than that of 5-ALA. Conclusion Administration of 5-ALA-GNPs, intensification of ROS generating and the subsequent elevation of photobleaching results in higher treatment efficiency. Also, more rapid clearance of PpIX has an important implication in clinical application of 5-ALA-GNPs that decreases the undesirable effects on healthy tissues.
TL;DR: It can be concluded that attenuation properties of applicator wall doesn't have a significant difference with water and therefore the Flexiplan treatment planning system accuracy is further confirmed.
Abstract: Introduction Interaluminal brachytherapy is one of the important methods of esophageal cancer treatment. The effect of applicator attenuation is not considered in dose calculation method released by AAPM-TG43. In this study, the effect of High-Dose Rate (HDR) brachytherapy esophageal applicator on dose distribution was surveyed in HDR brachytherapy. Materials and Methods A cylindrical PMMA phantom was built in order to be inserted by various sizes of esophageal applicators. EDR2 films were placed at 33 mm from Ir-192 source and irradiated with 1.5 Gy after planning using treatment planning system for all applicators. Results The results of film dosimetry in reference point for 6, 8, 10, and 20 mm applicators were 1.54, 1.53, 1.48, and 1.50 Gy, respectively. The difference between practical and treatment planning system results was 0.023 Gy (<2.7%), on average. Conclusion Due to the similar practical results for different esophageal applicators, it can be concluded that attenuation properties of applicator wall doesn't have a significant difference with water and therefore the Flexiplan treatment planning system accuracy is further confirmed.
TL;DR: In this paper, the reproducibility and uniformity of the ionization chambers at the Italian National Center of Oncological Hadron-therapy (CNAO) were analyzed using a series of preliminary testes.
Abstract: Introduction Hadron-therapy is an effective technique used to treat tumors that are located between or nearby vital organs. The Italian National Center of Oncological Hadron-therapy (CNAO) has been realized as the first facility in Italy to treat very difficult tumors with protons and Carbon ions. The on-line monitor system for CNAO has been developed by the Department of Physics of the University of Torino and Italian National Institute of Nuclear Physics (INFN). The monitoring system performs the on-line checking of the beam intensity, dimension, and beam position. Materials and Methods The monitor system is based on parallel plate ionization chambers and is composed of five ionization chambers with the anodes fully integrated or segmented in pixels or strips that are placed in two boxes. A series of measurements were performed that involve the background current and the detectors have been characterized by means of a series of preliminary testes in order to verify reproducibility and uniformity of the chambers using an X-ray source. Results The measured background currents for StripX, StripY and Pixel chambers are five orders of magnitude smaller than the nominal treatment current. The reproducibility error of chambers is less than 1%. The analysis of the uniformity showed that the monitor devices have a spread in gain that varies, but only about 2%. Conclusion The reproducibility and the uniformity values are considered as a good result, taking into account that the X-ray energy range is several orders of magnitude smaller than the particle energies used at CNAO.
TL;DR: Heterogeneous hypothesis testing method which uses S coefficients of received wave for construction of its decision function may be a suitable choice for detection of backscattered signals in breast radar.
Abstract: Performance of the proposed method was evaluated in two different scenarios, in which the breast was considered homogenous and heterogeneous, respectively. The obtained results showed that the proposed method detected breast backscattered signals 55% and 49% better than existing methods in two above scenarios. Conclusion Performance of S transform was 21% better than discrete wavelet transform in detection of weak backscattered signals. So it can be concluded that hypothesis testing method which uses S coefficients of received wave for construction of its decision function may be a suitable choice for detection of backscattered signals in breast radar.
TL;DR: In this article, a tissue-like phantom and an optical setup in reflectance mode were developed and the algorithm of multispectral imaging method was then written in Matlab environment.
Abstract: Introduction Non-invasive Fluorescent Reflectance Imaging (FRI) is used for accessing physiological and molecular processes in biological media. The aim of this article is to separate the overlapping emission spectra of quantum dots within tissue-equivalent phantom using SVD, Jacobi SVD, and NMF methods in the FRI mode. Materials and Methods In this article, a tissue-like phantom and an optical setup in reflectance mode were developed. The algorithm of multispectral imaging method was then written in Matlab environment. The setup included the diode-pumped solid-state lasers at 479 nm, 533 nm, and 798 nm, achromatic telescopic, mirror, high pass and low pass filters, and EMCCD camera. The FRI images were acquired by a CCD camera using band pass filter centered at 600 nm and high pass max at 615 nm for the first region and high pass filter max at 810 nm for the second region. The SVD and Jacobi SVD algorithms were written in Matlab environment and compared with a Non-negative Matrix Factorization (NMF) and applied to the obtained images. Results PSNR, SNR, CNR of SVD, and NMF methods were obtained as 39 dB, 30.1 dB, and 0.7 dB, respectively. The results showed that the difference of Jacobi SVD PSNR with PSNR of NMF and modified NMF algorithm was significant (p<0.0001). The statistical results showed that the Jacobi SVD was more accurate than modified NMF. Conclusion In this study, the Jacobi SVD was introduced as a powerful method for obtaining the unmixed FRI images. An experimental evaluation of the algorithm will be done in the near future.
TL;DR: The photon absorbed doses from radon progeny in all major organs of the human body through a simulation of the Oak Ridge National Laboratory (ORNL) adult phantom are studied using MCNPX2.4.0 Monte Carlo code and calculations.
Abstract: Introduction The potential hazards posed by exposure to radiation from radon have been of great concern worldwide, since it is especially associated with increased risk of lung cancer. Some radioisotopes of radon progeny deposited in the human lungs emit β particles followed by the γ rays. While γ rays are comparatively less damaging to the respiratory system than α and β particles, it is the principal deposited energy in other organs. Materials and Methods In order to establish a quantitative estimate of hazards caused by the radiation, this paper studies the photon absorbed doses from radon progeny in all major organs of the human body through a simulation of the Oak Ridge National Laboratory (ORNL) adult phantom using MCNPX2.4.0 Monte Carlo code and calculations which were performed in photon/electron mode. Results Effective dose due to photons from radon progeny deposited in the human lungs was about 1.69 µSvWLM-1. Based on UNSCEAR2006 reports, the effective dose of these photons per year is about 5.76´10-1mSv in for radon concentration of 31000 Bq/m3 (the maximum concentration of radon in Iran). Therefore, this value is comparable with 1mSv (The annual allowable effective dose). Conclusion The dosimetry of photons particularly in areas with high levels of exposure to radon and radon's decay products is important because all organs receive the photon absorbed dose from radon progeny.