Journal of Biomedical Physics & Engineering
Volume:10 Issue: 6, Nov-Dec 2020

Considering the importance of photoneutron production in linear accelerators, it is necessary to describe and measure the photoneutrons produced around modern linear accelerators.

The aim of the present research is to study photoneutron production for the 18 MV photon beam of a Siemens Primus Plus medical linear accelerator.

This study is an experimental study. The main components of the head of Siemens Primus Plus linac were simulated using MCNPX 2.7.0 code. The contribution of different components of the linac in photoneutron production, neutron source strength, neutron source strength and photon and electron spectra were calculated for the flattening filter and flattening filter free cases for the 18 MV photon beam, and was scored for three fields of 5 × 5 cm2, 10 × 10 cm2 and 20 × 20 cm2 in size.

The results show that the primary collimator has the largest contribution to production of neutrons. Moreover, the photon fluence for the flattening filter free case is 8.62, 6.51 and 4.62 times higher than the flattening filter case for the three fields, respectively. The electron fluences for the flattening filter free case are 4.62, 2.93 and 2.79 times higher than with flattening filter case for the three fields under study, respectively. In addition to these cases, by increasing the field size, the contribution of neutron production related to the jaws is reduced, so that when the field size increases from 5 × 5 cm2 to 20 × 20 cm2, a 17.93% decrease in photoneutron production was observed.

In all of the accelerators, the neutron strength also increases with increasing energy. The calculated neutron strength was equal to 0.83×1012 neutron Gy −1 at the isocenter.

Radiation therapy techniques as Intensity Modulated Radiotherapy (IMRT), rapid arc have been used for treatment of cancer with high accuracy.

Verification of planned and delivered dose distribution is important, therefore current study aims to analyse quality assurance (QA) results of IMRT by Electronic Portal Imaging Device (EPID) and IMatriXX in head and neck Carcinoma (Ca H&N) patients.

In this experimental study, performance of an EPID and IMatriXX was assessed with dose measurements using ionization chamber. Calibrated IMatriXX and EPID are used for pre-treatment patient specific quality assurance (PSQA), for 122 patients’ plans of Ca H&N with IMRT treatment technique on linear accelerator. Dose images were acquired and compared with gamma evaluation (3% / 3 mm) and three scalar parameters, named average γ (γavg), maximum γ (γmax) and area gamma <1, were analyzed in the region of interest.

The γ correlation comparisons yielded average correlation of 0.990 and 0.982 for IMatriXX and EPID respectively. Maximum value of gamma is 0.998, while minimum gamma is 0.872 for IMatriXX and 0.953 for EPID. For students, unpaired ‘t’ test analysis is applied for comparison to two data sets. P-value was set at 0.005 which, for this study, was computed 0.001, showing good correlation between measured data with IMatriXX and EPID.

The EPID and IMatriXX have significantly improved dosimetric properties, resulting in more sensitive, accurate measurements before actual treatment. The result shows EPID can be replaced with other dosimetry method and ionization chamber measurements. Portal imager is an efficient, accurate and sensitive dosimetry tool and is also the basis of pre-treatment quality assurance protocol.

Some organs in the body are sensitive to radiation such as eyes, breast, and gonads. Protection of sensitive organs against radiation is necessary. Recently, many sensitive organ shields have been developed from different materials.

The aim of this study is to evaluate the dose reduction and image quality from implementation of Silicone Rubber-Lead (SR-Pb) as an alternative gonad shield in digital radiography (DR).

In this experimental study, the SR-Pb gonad shields with various thicknesses of 2, 4, 6, 8, and 10 mm were synthesized. This study used the Pb percentage of 5 wt%. An anthropomorphic phantom was used in abdomen plain examinations. The results obtained from the use of the SR-Pb was compared with standard gonad shield, i.e. lead apron. To measure the dose reduction, the Piranha detector was used. The image quality assessment was evaluated with the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR).

This study showed the dose reduction was significant for all SR-Pb thicknesses, and incrementally increased with the increase of the SR-Pb thickness. The minimum and maximum of dose reduction were 22.8% for 2 mm and 66.9% for 10 mm SR-Pb, respectively.

Compared to the reference image without gonad shield, the SNR and CNR do not significantly change. Hence, the SR-Pb is probably to be used as an alternative gonad shield.

Spermatogenesis system is one of the most radiosensitive organs in the body. A usual therapeutic dose of radiation such as the conventional 2 Gy in each fraction of radiotherapy and lower doses seen in diagnostic radiology or a radiation disaster affect the process of spermatogenesis potently. Selenium and zinc are two important elements playing key roles in the development of sperms and also have radioprotective effects.

In this study aims to evaluate the radioprotective effect of zinc and selenium against radiation-induced mice testis injury.

In this experimental study, 30 mice were divided equally into 6 groups, including control selenium treated, zinc treated, radiation, radiation + selenium, radiation + zinc. Treatments started from 2 days before irradiation with 2 Gy cobalt-60 gamma rays. After 37 days, all mice were killed for histopathological evaluations.

Results showed that exposure to radiation caused a potent effect on spermatogenesis system. Treatment with selenium reversed these radiation effects potently, while zinc had some limited protective effects. Zinc treatment itself caused a detrimental effect on epididymis and, in combination with radiation, it leads to more damage to seminiferous tubules.

In contrast to previous studies that proposed zinc to protect spermatogenesis against various toxic agents, results of this study showed that although zinc may protect from some parameters, it potentiates radiation damage on seminiferous tubules and has a detrimental effect on the epididymis. By contrast, zinc and selenium could alleviate radiation-induced toxicity on the most of the evaluated parameters.

The ability to monitor kidney function after transplantation is one of the major factors to improve care of patients.

Authors recommend a computerized texture analysis using run-length matrix features for detection of changes in kidney tissue after allograft in ultrasound imaging.

A total of 40 kidney allograft recipients (28 male, 12 female) were used in this longitudinal study. Of the 40 patients, 23 and 17 patients showed increased serum creatinine (sCr) (increased group) and decreased sCr (decreased group), respectively. Twenty run-length matrix features were used for texture analysis in three normalizations. Correlations of texture features with serum creatinine (sCr) level and differences between before and after follow-up for each group were analyzed. An area under the receiver operating characteristic curve (Az) was measured to evaluate potential of proposed method.

The features under default and 3sigma normalization schemes via linear discriminant analysis (LDA) showed high performance in classifying decreased group with an Az of 1. In classification of the increased group, the best performance gains were determined in the 3sigma normalization schemes via LDA with an Az of 0.974 corresponding to 95.65% sensitivity, 91.30% specificity, 93.47% accuracy, 91.67% PPV, and 95.45% NPV.

Run-length matrix features not only have high potential for characterization but also can help physicians to diagnose kidney failure after transplantation.

Medical image fusion is being widely used for capturing complimentary information from images of different modalities. Combination of useful information presented in medical images is the aim of image fusion techniques, and the fused image will exhibit more information in comparison with source images.

In the current study, a BEMD-based multi-modal medical image fusion technique is utilized. Moreover, Teager-Kaiser energy operator (TKEO) was applied to lower BIMFs. The results were compared to six routine methods.

In this study, which is of experimental type, an image fusion technique using bi-dimensional empirical mode decomposition (BEMD), Teager-Kaiser energy operator (TKEO) as a local feature selection and Hierarchical Model And X (HMAX) model is presented. BEMD fusion technique can preserve much functional information. In the process of fusion, we adopt the fusion rule of TKEO for lower bi-dimensional intrinsic mode functions (BIMFs) of two images and HMAX visual cortex model as a fusion rule for higher BIMFs, which are verified to be more appropriate for human vision system. Integrating BEMD and this efficient fusion scheme can retain more spatial and functional features of input images.

We compared our method with IHS, DWT, LWT, PCA, NSCT and SIST methods. The simulation results and fusion performance show that the presented method is effective in terms of mutual information, quality of fused image (QAB/F), standard deviation, peak signal to noise ratio, structural similarity and considerably better results compared to six typical fusion methods.

The statistical analyses revealed that our algorithm significantly improved spatial features and diminished the color distortion compared to other fusion techniques. The proposed approach can be used for routine practice. Fusion of functional and morphological medical images is possible before, during and after treatment of tumors in different organs. Image fusion can enable interventional events and can be further assessed.

Multiple Sclerosis (MS), distinguished by aggravating the function of central nervous system because of inflammatory demyelination. The most sensitive method for MS diagnosis is Magnetic resonance imaging (MRI). To distinguish inactive and active MS lesions, contrast-enhanced T1-weighted imaging (CE T1WI) is being used as a gold standard. There are some contraindications in gadolinium based contrast agents (GBCAs) usage. Moreover, diffusion-weighted imaging (DWI) can discover diffusion changes involved inflammatory lesions.

The current research aims at investigating if typical DWI (3 directional) and 12 directional DWI could be a substitute for CE T1WI in order to show active lesions of MS.

In this cross-sectional study, 138 patients with CNS symptoms were examined. For all patients, along with CE T1WI, 3 & 12 directional DWI were performed. Intraclass correlation coefficient (ICC), receiver operating characteristic (ROC), the sensitivity versus specificity plot and the area under the curve (AUC) were calculated.

There was a contrast enhancement in CE T1WI for 114 patients (82.6%); in addition, hyper-intense lesions on DWI 3 and DWI 12 were shown in 107 (77.5%) and 117 patients (84.7%) in order. Sensitivity, specificity and AUC were 94.7%, 62.5% and 84% for DWI 12. Moreover, the results were 86%, 62.5 and 79% for the sensitivity, specificity and AUC for DWI 3 respectively.

In spite of lower sensitivity of 12 directional DWI compared to CE T1WI, it could be used as a diagnostic sequence in differentiating enhanced lesions from non-enhanced ones when CE-MRI is a worry.

Lactobacillus acidophilus and Lactobacillus casei are gram-positive probiotics and members of the genus Lactobacillus. These bacteria are widely applicable in food and dairy industries. Increasing bacterial load and decreasing fermentation time make them more profitable for manufacturers.

This study was aimed at assessing the biological effects of short-term exposure of L. acidophilus and L. casei to 2.4 GHz Wi-Fi radiofrequency electromagnetic fields (RF-EMF) generated by a Wi-Fi router on the lactic acid production and proliferation of these probiotic bacteria.

This experimental study was performed on pure culture strains of L. acidophilus and L. casei, first direct vat sets (DVS) were activated in MRS broth for 24 hours then transferred to new culture mediums. Afterward, these mediums were exposed to RF-EMF for 15, 30, 45 and 60 minutes. The control samples were sham-exposed. After 72 hours of incubation on MRS agar cell counts were enumerated.

Exposure for 30, 45 and 60 minutes significantly increased the growth of L. acidophilus and L. casei. No difference was found between the growth of the samples exposed to RF-EMF for 15 minutes compared to that of sham-exposed bacteria. In addition, lactic acid concentration in L. acidophilus medium was amplified after 15, 30 and 45 minutes of exposure. However, in L. casei samples, only 30 and 60 min exposures could stimulate the production of lactic acid.

L. acidophilus and L. casei probiotic bacteria exposed for a short time to radiofrequency electromagnetic radiation (RF-EMF) generated by a widely used commercial Wi-Fi router show significantly increased proliferation and lactic acid production.

Early detection of peri-implant bone defects is highly important because these defects eventually lead to gingival recession, bone loss and implant failure.

This study aimed to assess and compare the efficacy of periapical radiography and three CBCT systems for the detection of peri-implant dehiscence defects.

In this vitro study, 124 titanium implants were placed in bovine ribs. The bone pieces were then mounted in boxes in the form of mandible and red dental wax was used to simulate the soft tissue. Crestal bone defects with 2, 3, and 4 mm depth were created in the ribs using a round bur. Periapical and CBCT images were then obtained. Images were investigated by two oral and maxillofacial radiologists twice with a two-week interval. The results were analyzed using chi-square, Kappa coefficient, Cochrane’s Q and McNemar tests as well as the receiver operating characteristic (ROC) curve.

The two observers showed good agreement in detection of sound and defective samples on periapical radiographs and CBCT scans. The level of agreement was low in detection of two samples with 2 mm defects on CBCT scans taken with Planmeca and NewTom 3G systems at the time of second assessment. NewTom 3G had the highest sensitivity (68.9%, 74.2% and 86.3%, respectively) and specificity (100% for all three) compared to other systems for detection of 2, 3 and 4 mm crestal bone defects.

The inter-observer agreement increased with increase in depth of defects. NewTom 3G had the highest accuracy for detection of crestal bone defects.

Patients suffering from osteoarthritis undergo surgery to replace hip joints with hip prosthesis implants. Today most acetabular cups of hip prostheses are made of Ultra-High-Molecular-Weight-Polyethylene. However, these materials acting as acetabular cups of the implant have been recalled since patients have been feeling uncomfortable and abstained from physical activities. A newly introduced material, 30% Carbon Reinforced Polyetherketone, possess better isotropic mechanical properties and lower wear rates.

The research aims to compare the von-Mises stresses and deformation in static and dynamic loading of Ultra-High Molecular-Weight-Polyethylene to 30% Reinforced Carbon Fiber Polyetherketone using Finite Element Analysis.

An analytical study was performed to evaluate material selection and their contact performances of acetabular cups. Four pairs have been analyzed under loading conditions following ASTM F2996-13 and ISO 7206-4 standards. The acetabular cups options are made of 30% Carbon Reinforced Fiber Polyetherketone or Ultra-High-Molecular-Weight-Polyethylene. Besides, the femoral head and steam options are either Alumina Ceramic or Cobalt Chrome Molybdenum.

The yield strength of Ultra-High-Molecular-Weight-Polyethylene is considerably small, resulting in the acetabular cup to fail when applied to high loading conditions. Carbon Reinforced Polyetherketone with Alumina Ceramic yielded 65% lower deformation at stumbling phase.

Since the study focuses on linear isotropic material properties, Alumina Ceramic dominates a higher elastic modulus than Cobalt Chrome Molybdenum, nominating it the best fit combination for lower von-Mises stresses, acting on the Carbon Reinforced Polyetherketone acetabular cup.

Mitoxantrone is a chemotherapy anti-cancer drug, which can have side effects on healthy cells like secondary cancers. On the other side, Melatonin is a hormone that is responsible for the daily rhythm adjustment and has several properties to be anticancer and anti-inflammatory. Recently, it has been shown that all living cells produce ultraweak photon emission (UPE) spontaneously and continuously. The intensity of UPE is in the order of a few, up to 104 photon/(cm2 sec) (or 10−19 to 10−14 W/cm2) measurable by photodetectors. UPEs are produced from diverse natural oxidative and biochemical reactions, especially free radical reactions and the simple cessation of excited molecules. Also, it has been evidenced that UPE has a signaling role at a distance among different cell cultures.

Here, we investigate the effect of UPE among similar cells (i.e. “Autooptic effect”) by using mirrors around the cell plate(s).

In this experimental research, the HepG2 cells were co-treated by melatonin as a genoprotective and silver nanoparticles as a carrier against mitoxantrone’s genotoxicity. Our results are analyzed based on the Comet assay method, and the genoprotective effect of melatonin is investigated in presence of (and without) mirrors against the genotoxicity of mitoxantrone. Additionally, the autooptic effect is investigated in presence of Ag nanoparticles (NPs).

The results indicated that Ag NPs with lower concentrations of melatonin made more protection as genoprotective agent, and the same results obtained by increasing access’ cells to drug.

The autooptic effect could increase the genoprotective effect of melatonin.

The damage of the central nervous system due to Multiple Sclerosis (MS) leads to many walking disorders in this population. However, current ankle-foot orthoses prescribed for improving walking disorders for these patients are not clinically cost-efficient.

This study aimed to design and fabricate a dynamic ankle foot orthosis and a new spring-damper joint mechanism that could adapt the walking problems of MS patients and evaluate the immediate effect of the new orthosis on the speed, range of motion, moment, total work and ground reaction force during walking.

In this case-series study, after the design and fabrication of a new orthosis, the kinetics and kinematics of walking of four patients with MS were assessed in a case series study.

Walking speed improved with the new orthosis in two participants. The sagittal range of motion (ROM) increased for most of the participants. The sagittal moments increased for hip, knee and ankle joints in most of the measurements. The total joint work showed noticeable difference in the ankle joint. The increased values of vertical component of the ground reaction force (VGRF) were negligible and the increase in the impulse of VGRF was noticeable for only one participant.

The new orthosis had positive effects kinetic and kinematic parameters of walking such as the increased velocity by two subjects and also a more normal sagittal ROM, moment and work, suggesting the potential usefulness of the new orthotic device for MS population.

New advancements have increased the capabilities of computed tomography as a sectional medical imaging modality. An important note is assessing absorbed dose to patients and minimizing it when performing computed tomography examinations. One approach to control dose is to establish diagnostic reference levels.

This study aimed to investigate diagnostic reference levels of computed tomography in Hamadan.

This work was conducted as an experimental study. Computed tomography dose index (CTDI) was measured using a Piranha quality control kit, head and body CTDI phantoms for brain, lung, abdomen-pelvic and coronary CT angiography examinations. Volume Computed Tomography Dose Index (CTDIvol) was calculated from obtained data and 3rd quartile of that was determined as diagnostic reference levels.

Diagnostic reference levels (DRLs) in terms of CTDIvol for brain, lung, abdomen-pelvic and coronary CT angiography were 50/25, 6/73, 22/01 and 32/06 mGy respectively in Hamadan. Difference between displayed CTDIvol and measured CTDIvol is not significance for all examinations (p>0.05).

DRLs depend on to many dose affecting parameters in CT. DRL for brain CT is greater than other scan regions. Application of DRLs which resulted from this study can help to optimize radiation dose to the patients while maintaining acceptable diagnostic images quality.

This work proposes a deep learning model for skin cancer detection from skin lesion images. In this analytic study, from HAM10000 dermoscopy image database, 3400 images were employed including melanoma and non-melanoma lesions. The images comprised 860 melanoma, 327 actinic keratoses and intraepithelial carcinoma (AKIEC), 513 basal cell carcinoma (BCC), 795 melanocytic nevi, 790 benign keratosis, and 115 dermatofibroma cases. A deep convolutional neural network was developed to classify the images into benign and malignant classes. A transfer learning method was leveraged with AlexNet as the pre-trained model. The proposed model takes the raw image as the input and automatically learns useful features from the image for classification. Therefore, it eliminates complex procedures of lesion segmentation and feature extraction. The proposed model achieved an area under the receiver operating characteristic (ROC) curve of 0.91. Using a confidence score threshold of 0.5, a classification accuracy of 84%, the sensitivity of 81%, and specificity of 88% was obtained. The user can change the confidence threshold to adjust sensitivity and specificity if desired. The results indicate the high potential of deep learning for the detection of skin cancer including melanoma and non-melanoma malignancies. The proposed approach can be deployed to assist dermatologists in skin cancer detection. Moreover, it can be applied in smartphones for self-diagnosis of malignant skin lesions. Hence, it may expedite cancer detection that is critical for effective treatment.