Journal of Biomedical Physics and Engineering最新文献

Background: Magnetic Resonance imaging (MRI) is a valuable diagnostic tool by its non-invasive/non-ionizing nature.

Objective: This study aims to determine justification of MRI in hospitalized patients at a tertiary provincial referent medical center in a one-year period.

Material and methods: In the present retrospective and descriptive cross-sectional study, 438 admitted patients referred for MRI during 2017 were selected using systematic random sampling. The age, gender, investigated organ, the specialty of requesting physician, MRI with and without contrast, MRI diagnostic outcome were collected using checklists. Descriptive statistics and chi-square test were used for data analysis.

Results: The mean age of the patients was 42±26 years-old and female represented 53% of enrolled patients. The most and less prevalent investigated organs were the cerebrum and the orbit. After excluding cancer diagnosis, cancer staging, and therapeutic follow-up exams, MRI request was oriented in 64.3% and 77.2% of positive results was concordant with aforementioned diagnostic orientation (P<0.001). Oriented diagnostic MRI requesting is influenced by age, medical specialists and, investigated organ (P<0.001). The positive MRI is influenced significantly by oriented MRI request, gender, medical specialists and investigated organ (P<0.001). The diagnosis concordance of MRI is influenced significantly by oriented MRI request, medical specialists and investigated organ (P<0.001).

Conclusion: Appropriate implementation of medical imaging requires boosting employed rationality by the concerned physicians. The current suboptimal results to requesting MRI rationality should mandate supplementary educational programs as to incite the medical corpus more closely implementing the published medical practice guidelines.

Background: Methods for segmentation, i.e., Full-segmentation (FS) and Segmentation-rotation (SR), are proposed for maintaining Computed Tomography (CT) number linearity. However, their effectiveness has not yet been tested against noise.

Objective: This study aimed to evaluate the influence of noise on the accuracy of CT number linearity of the FS and SR methods on American College of Radiology (ACR) CT and computational phantoms.

Material and methods: This experimental study utilized two phantoms, ACR CT and computational phantoms. An ACR CT phantom was scanned by a 128-slice CT scanner with various tube currents from 80 to 200 mA to acquire various noises, with other constant parameters. The computational phantom was added by different Gaussian noises between 20 and 120 Hounsfield Units (HU). The CT number linearity was measured by the FS and SR methods, and the accuracy of CT number linearity was computed on two phantoms.

Results: The two methods successfully segmented both phantoms at low noise, i.e., less than 60 HU. However, segmentation and measurement of CT number linearity are not accurate on a computational phantom using the FS method for more than 60-HU noise. The SR method is still accurate up to 120 HU of noise.

Conclusion: The SR method outperformed the FS method to measure the CT number linearity due to its endurance in extreme noise.

Background: The immune system plays an extensive role in eliminating tumor cells. On the other hand, low-dose irradiation stimulates the immune system.

Objective: The present study aimed to investigate the therapeutic outcomes of localized high-dose radiotherapy (LH) alone and combined with total body low-dose irradiation (TB).

Material and methods: In this experimental study, B16F0 tumor cells were injected into the right flank of C57JL/6 mice. The mice were treated with LH alone (13 Gy X-rays to the tumor surface) (LH group) or combined with TB (85 mGy X-rays at the skin) (TB+LH group). Then the tumor volume, the mice's lifespan, the number of lymphocytes extracted from the spleen, and interferon gamma (IFN-γ) production were measured.

Results: Reduced number of lymphocytes, compared to non-irradiated mice (control group), was observed in LH and TB+LH groups. However, the identical number of cultured lymphocytes produced a higher level of IFN-γ in irradiated groups. Comparing the irradiated groups, the number of lymphocytes and their IFN-γ production, tumor growth control, and the mice's lifespan were statistically higher in TB+LH group.

Conclusion: Observing a higher level of IFN-γ in TB+LH group compared to LH group indicates that low-dose radiation enhanced the stimulating effects of high-dose radiation on the immune system. It caused the mice in TB+LH group to have a more prolonged lifespan and a lower tumor growth rate. Therefore, it is worth our attention for future studies to investigate whether total body low-dose irradiation can be utilized before radiotherapy to enhance its efficiency.

Background: The same conversion factors (k-factors) of Single CT (SECT) are applied to estimate the Effective Dose (ED) in Dual Energy Computed Tomography (DECT). However, k-factors for different organs need independently validating for DECT, due to the different conditions in DECT.

Objective: This study aimed to calculate organ dose and k-factors in different imaging protocols (liver, chest, cardiac, and abdomen) for male and female phantoms.

Material and methods: This Monte Carlo Simulation study used Monte Carlo N-Particle (MCNP) code for modeling a Siemens Somatom Definition Flash dual-source CT scanner. The organ dose, dose length product, and k-factors were calculated for the Medical Internal Radiation Dose (MIRD) of male and female phantoms.

Results: For the male phantom, the k-factors for the liver, chest, cardiac, and abdomen-pelvis imaging protocols are equal to 0.020, 0.012, 0.016, and 0.014 mSv.mGy^-1cm^-1, respectively. For the female phantom, the corresponding values are equal to 0.026, 0.023, 0.036, and 0.018, respectively. These values for DECT are different from those corresponding values for SECT, especially for the female phantom.

Conclusion: The calculated k-factors for DECT can be used as reference values for the estimation of ED in DECT.

Background: Multiple sclerosis (MS) as a complex neurological abnormality is marked with loss of myelin and axons due to chronic inflammatory and autoimmune responses. The modulatory properties of the low dose radiation (LDR) on inflammatory and immune responses have well known.

Objective: The current research aimed to assess the impacts of LDR on the disability in patients suffering from MS.

Material and methods: This experimental pilot study was done on 10 patients with secondary progressive multiple sclerosis (SPMS). After magnetic resonance imaging, the SPMS patients were treated by LDR at a daily dose of 2 Gray for 5 consecutive days (totally 10 Gray dose) using a linear accelerator. The extent of the disability was evaluated one week after the completion of radiotherapy using expanded disability status scale (EDSS).

Results: After receiving radiotherapy, the patients had a feeling of wellbeing of some sort. The mean of EDSS was significantly reduced after radiotherapy compared with before irradiation (7.4±0.45 vs 6.35±1.18; P<0.017). EDSS more decreased in younger SPMS patients (P=0.0001), and in the women after LDR (P=0.027).

Conclusion: Radiotherapy can reduce fatigue and EDSS in patients with SPMS. The age and gender of patients may influence the LDR efficacy.

Background: Ophthalmic brachytherapy using radioactive plaques is an effective technique for the treatment of uveal melanoma. Ru-106 eye plaques are considered as interesting issue due to their steep gradient dose. The pre-planning evaluation of dosimetric parameters is essential for the treatment planning system.

Objective: The current study aims at providing dose distributions of six Ru-106 eye plaques (CCA, CCB, CGD, CIB, COB and COD) using radiochromic EBT3 film, Geant4 Monte Carlo toolkit and the treatment planning software (Plaque Simulator).

Material and methods: In this experimental study, an in-house phantom was employed for depth dose measurements with EBT3 films. Also, Geant4.10.5 scoring mesh was implemented to obtain the 2D dose distribution of the plaques. The results were compared with Plaque Simulator software and the manufacturer's (BEBIG) data. The gamma index criterion (3%/3 mm) was used to evaluate dose distributions obtained by the film measurements and Geant4 simulation.

Results: A good agreement was achieved between simulation and experimental results. Gamma index passing rate was 94.2%, 89.3%, 88.2%, 82.2%, 92.2% and 90.1% for CCA, CCB, CGD, CIB, COB and COD plaques, respectively. Absolute dose rate (mGy/min) obtained by EBT3 film at the depth of 2 mm was 79.4 mGy/min, 81.0 mGy/min, 78.6 mGy/min, 62.2 mGy/min, 75.2 mGy/min and 81.2 mGy/min for CCA, CCB, CGD, CIB, COB and COD plaques, respectively.

Conclusion: The measured dose distributions and lateral dose profiles may be utilized in the treatment planning system to cover clinical volumes such as the clinical target volume and the gross tumor volume.

Background: Dementia involves a neuronal loss in the primary somatosensory cortex of the parietal lobe, causing dementia patients to perceive pain stimuli hardly. The function of temperature sensation declines. Studies measuring brain blood volume using near-infrared light have reported that patients suffering from dementia have less activation than healthy elderly people. However, the majority of these studies used tests related to cognitive function and the frontal lobe, and few have examined thermal sensation.

Objective: The present study aimed to investigate the effect of cold and warm stimulation on cerebral blood volume in elderly and young subjects.

Material and methods: This observational study measured changes in oxygenated hemoglobin concentrations in the frontal cortex during cold and warm stimulation in elderly and young subjects using a near-infrared light device. The mean and standard deviation of the change in oxygenated hemoglobin concentration before and after cold and warm stimulation, as well as the center-of-gravity values, were compared between the young and the elderly.

Results: During warm stimulation, the younger subjects showed an increase in blood oxygenated hemoglobin levels; however, the difference was not significant. For the elderly, no change was observed during the task. The center of gravity values was lower in the young compared to the elderly which was similar to the reaction threshold. No significant changes were observed during cold stimulation.

Conclusion: Thermal sensation thresholds were impaired in the elderly compared to the young; however, cerebral blood volume changes were unclear.

Human is usually exposed to environmental radiation from natural and man-made sources. Therefore, it is important to investigate the effects of exposure to environmental radiation, partly related to understanding and protecting against the risk of exposure to environmental radiation with beneficial and adverse impacts on human life. The rapid development of technologies causes a dramatic enhancement of radiation in the human environment. In this study, we address the biological effects caused by different fractions of non-ionizing electromagnetic irradiation to humans and describe possible approaches for minimizing adverse health effects initiated by radiation. The main focus was on biological mechanisms initiated by irradiation and represented protection, and safety approaches to prevent health disorders.

Background: Substantial data indicate that genetic and environmental factors play a key role in determining the risk of Alzheimer's disease (AD). Moreover, it is known that having relatives with AD increases the risk of developing this disease.

Objective: This study is aimed at investigating whether having a family history of AD, may increase the risk of COVID-19 in a cohort-based study.

Material and methods: Participants of this retrospective cohort study were previously enrolled in the SUMS Employees Cohort (SUMSEC). All participants including those whose SARS-CoV-2 infection was confirmed by positive PCR test and chest CT scan were requested to respond to interviewer-administered questionnaires. Moreover, AD was diagnosed via memory and thinking impairment, concentration problems, confusion with location, and problems in finishing daily tasks.

Results: The total numbers of female and male participants with a family history of AD were 463 and 222 individuals, respectively. When all types of family history of AD were considered, a 51.3% increase was found in the relative frequency of the participants with both family history of AD and confirmed COVID-19 compared with those only with a family history of AD.

Conclusion: Despite the limitations of our study, and from a broader perspective, our findings can further support the concept that AD risk haplotypes including APOE are linked to the same morbidities from cardiovascular disease and obesity that increase vulnerability to COVID-19. Given this consideration, millions of APOE ε4 carriers around the globe should be advised to take additional precautions to prevent life-threatening diseases such as COVID-19.

Passive and hybrid passive Ankle foot orthoses (AFOs) are the prevalent prescription in drop foot patients to prevent toe dragging during the swing phase. While, these AFOs have some limitations like inability to overcome foot slap, limitation in forward propulsion and inappropriate power generate at the push off. The aim of this study was to design a novel spring damper and evaluate the immediate effects of this AFO on improving the ankle kinetic and kinematic in drop foot patients. This AFO was generated from carbon composite frame and foot section with posterior hinge and spring damper actuator that controlled plantar flexion resistance at the early stance, freely dorsi flexion movement with the ability to store energy during mid-stance movement as well as restore this energy at the pre swing phase. This AFO was assessed on ten drop foot patients who used Posterior Leaf Spring AFO conditions and walked at their self-comfortable walking speed. Then the ankle kinetic and kinematic data in two conditions of with PLS (Posterior Leaf Spring) AFO, and novel spring damper AFO were assessed. Results showed a significant improve in the immediate effect of the kinetic and kinematic parameters. In conclusion, spring damper AFO improved all ankle angles in entire gait cycle as well as the ankle moments and power. Therefore, this AFO should be consider as a selective AFO in drop foot patients.