جستجوی مقالات مرتبط با کلیدواژه « x-rays » در نشریات گروه « پزشکی »

Radiation protection is an essential issue in diagnostic radiology to ensure the safety of patients, healthcare professionals, and the general public. Lead has traditionally been used as a shielding material due to its high atomic number, high density, and effectiveness in attenuating radiation. However, some concerns related to the long-term health effects of toxicity, environmental disease as well as heavy weight of lead have led to the search for alternative lead-free shielding materials. Lead‑free multilayered polymer composites and non-lead nano-composite shields have been suggested as effective shielding materials to replace conventional lead-based and single metal shields. Using several elements with high density and atomic number, such as bismuth, barium, gadolinium, and tungsten, offer significant enhancements in the shielding ability of composites. This review focuses on the development and use of lead-free materials for radiation shielding in medical settings. It discusses the drawbacks of traditional lead shielding, such as toxicity, weight, and recycling challenges, and highlights the benefits of lead-free alternatives.

This study aimed to synthesize Samarium-doped TiO2 nanoparticles (Ti(Sm)O2 NPs) using solvothermal synthesis and evaluate their suitability as targeted imaging agents. The objectives were to enhance the stability and biocompatibility of the nanoparticles by coating them with polymeric materials and assess their imaging capabilities and safety. 

Ti(Sm)O2 NPs were synthesized using the solvothermal method with TiO2, NaOH, and deionized water. The resulting solution was filtered, dried, and processed in a Teflon-lined stainless steel autoclave. The obtained product was washed, dried, and coated with FDA-approved polymers including polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and carboxymethyl cellulose (CMC). Coating was achieved through a mixing process and subsequent drying. 

Characterization studies confirmed the desired morphology, crystal structure, optical properties, surface charge, and biocompatibility of the Ti(Sm)O2 NPs. In vivo imaging evaluations demonstrated their excellent imaging capabilities, particularly in distinguishing lung pathologies. Additionally, in vivo toxicity studies confirmed the nanoparticles biocompatibility and safety, with no adverse effects on organ function observed. 

In this study, Samarium-doped TiO2 nanoparticles WERE successfully synthesized and their potential as targeted imaging agents was evaluated. The coating of the nanoparticles with polymeric materials enhanced their stability and biocompatibility. The nanoparticles exhibited excellent imaging capabilities, particularly in distinguishing lung pathologies. Moreover, they demonstrated biocompatibility and safety in vivo. These findings contribute to the development of advanced contrast agents for biomedical applications, providing effective tools for targeted imaging and improving the diagnosis and monitoring of various lung pathologies.

Radiotherapy is a frequently used therapeutic modality for breast cancer. Dalbergin, a natural antioxidant, inhibits carcinogens and tumor progression. In the present study, we investigated the effect of Dalbergin on the response of T47D and MDA-MB-231 breast cancer cell lines to ionizing radiation. In this experimental in vitro study, doubling time of T47D and MDAMB- 231 were obtained from the growth curve. The cytotoxic effect of Dalbergin on T47D and MDA-MB-231 breast cancer cells were estimated via MTT assay. To determine the clonogenic ability, we treated T47D and MDA-MB-231 with Dalbergin for 48 h prior to irradiation, subsequent to which a colony assay was performed. Real-time polymerase chain reaction was employed to determine the gene expression level. Dalbergin inhibited proliferation of T47D and MDA-MB-231 in a time and concentration-dependent manner. Additionally, the most appropriate time for the treatment of these types of cancer cells was found to be 48 h and the drug's concentration in both cell lines was different. The IC50 values of T47D and MDA-MB-231 cells were 0.001 and 0.0001 μM, respectively. Moreover, this drug radiaosensitizes both cell lines effectively compared with the radiation only. Finally, the gene expression level of p53, Bcl-2, and STAT3 were investigated in cancer cells. Dalbergin showed apoptotic effects probably through the STAT/p53 signaling pathway. Therefore, Dalbergin could be considered as a radiosensitizer and its effects may be owing to increased cell death.

Coronavirus disease 2019 (COVID-19) is presently a life-threatening condition, and despite of multiple attempts, no functional method has been introduced against this pandemic problem yet. In this study, for the first time, the possible antiviral aspects of mineral nanoparticles (MNPs) obtained from a natural source, thermal spring water, were evaluated.

At first, MNPs obtained from the Gishki thermal spring, Kerman province, Iran, were characterized by transmission electron microscope (TEM). Then, the presence of mineral elements in MNPs was identified by X-ray fluorescence (XRF), Energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma mass spectrometry (ICP-MS), and MTT assay. Finally, 17 cases suspected of COVID-19 were randomly selected, and their nasal swab samples were exposed to two concentrations of MNPs (50 and 100 u/mL).

The results of real-time polymerase chain reaction (RT-PCR) test manifested that MNPs had a destructive effect on 4 (33%) COVID-19 cases.

Therefore, MNPs of thermal spring water may act as an obstacle against COVID-19.

The effect of region of interest (ROI) size variation on producing accurate noise levels is not yet studied.  This study aimed to evaluate the influence of ROI sizes on the accuracy of noise measurement in computed tomography (CT) by using images of a computational and American College of Radiology (ACR) phantoms. In this experimental study, two phantoms were used, including computational and ACR phantoms. A computational phantom was developed by using Matlab R215a software (Mathworks Inc., Natick, MA Natick, MA) with a homogeneously +100 Hounsfield Unit (HU) value and an added-Gaussian noise with various levels of 5, 10, 25, 50, 75, and 100 HU. The ACR phantom was scanned with a Philips MX-16 slice CT scanner in different slice thicknesses of 1.5, 3, 5, and 7 mm to obtain noise variation. Noise measurement was conducted at the center of the phantom images and four locations close to the edge of the phantom images using different ROI sizes from 3×3 to 41×41 pixels, with an increased size of 2×2 pixels.  The use of a minimum ROI size of 21×21 pixels shows noise in the range of ±5% ground truth noise. The measured noise increases above the ±5% range if the used ROI is smaller than 21×21 pixels.   A minimum acceptable ROI size is required to maintain the accuracy of noise measurement with a size of 21×21 pixels.

Estimation of eye lens dose is important in head computed tomography (CT) examination since the eye lens is a sensitive organ to ionizing radiation. The purpose of this study is to compare estimations of eye lens dose in head CT examinations using local size-specific dose estimate (SSDE) based on size-conversion factors of the American Association of Physicists in Medicine (AAPM) Report No. 293 with those based on size-conversion factors of the AAPM Report No. 220. This experimental study is conducted on a group of patients who had undergone nasopharyngeal CT examination. Due to the longitudinal (z-axis) dose fluctuation, the average global SSDE and average local SSDE (i.e. particular slices where the eyes are located) were investigated. All estimates were compared to the measurement results using thermo-luminescent dosimeters (TLDs). The estimated and measured doses were implemented for 14 patients undergoing nasopharyngeal CT examination. It was found that the percentage differences of the volume CT dose index (CTDIvol), average global SSDE based on AAPM No. 220 (SSDEo,g), average local SSDE based on AAPM No. 220 (SSDEo,l), average global SSDE based on AAPM No. 293 (SSDEn,g) and average local SSDE based on AAPM No. 293 (SSDEn,l) against the measured TLD doses were 22.5, 21.7, 15.0, 9.3, and 2.1%, respectively. All comparisons between dose estimates and TLD measurements gave p -values less than 0.001, except for SSDEn,l (p -value = 0.566). SSDE based on AAPM Report No. 293 can be used to accurately estimate eye lens radiation doses by performing the calculations on a number of specific slices containing the eyes.

It is necessary to have an automated noise measurement system working accurately to optimize dose in computerized tomography (CT) examinations. This study aims to develop an algorithm to automate noise measurement that can be implemented in CT images of all body regions. In this retrospective study, our automated noise measurement method consists of three steps as follows: the first is segmenting the image of the patient. The second is developing a standard deviation (SD) map by calculating the SD value for each pixel with a sliding window operation. The third step is estimating the noise as the smallest SD from the SD map. The proposed method was applied to the images of a homogenous phantom and a full body adult anthropomorphic phantom, and retrospectively applied to 27 abdominal images of patients. For a homogeneous phantom, the noises calculated using our proposed and previous algorithms have a linear correlation with R2 = 0.997. It is found that the noise magnitude closely follows the magnitude of the water equivalent diameter (Dw) in all body regions. The proposed algorithm is able to distinguish the noise magnitude due to variations in tube currents and different noise suppression techniques such as strong, standard, mild, and weak ones in a reconstructed image using the AIDR 3D algorithm. An automated noise calculation has been proposed and successfully implemented in all body regions. It is not only accurate and easy to implement but also not influenced by the subjectivity of user.

Radiotherapy has become a part of therapeutic process of more than 50 percent of patients suffering from cancer. However, recent studies have shown that radiation therapy might affect the expression of adhesive molecule related genes such as E-cadherin and cause cancer cells to move and migrate. Besides, various studies have reported that the expression of E-cadherin changes differently after radiation treatment. There are several studies which showed the loss of E-cadherin function after radiation; however, this reduction has not been observed in others.

This study aims to investigate the effect of different radiation doses of X-ray on changes that might occur in the expression of E-cadherin gene in colorectal cancer cell line HT-29.

In this experimental study, the cells cultured in flasks were irradiated with X- rays in different doses, including 0.1, 2.5, 5, and 10 Gy; then, the expression of E-cadherin gene was measured using real-time PCR.

The expression of E-cadherin did not change significantly in post-irradiated HT-29 cell line after different radiation doses of X-ray.

The results showed that low, medium and high doses of X- radiation did not change the expression of E-cadherin gene in HT-29 cancer cells. However, it has been reported that radiation mostly downregulated the expression of E-cadherin and mediated metastasis formation and invasiveness in different cancer cell lines. Therefore, further studies need to be conducted to investigate the effects of radiation dose on the molecular pathways contributing to regulation of E-cadherin in HT-29 cell line.

Noise reduction is a method for reducing CT dose; however, it can reduce image quality. This study aims to propose a selective mean filter (SMF) and evaluate its effectiveness for noise suppression in CT images. This experimental study proposed and implemented the new noise reduction algorithm. The proposed algorithm is based on a mean filter (MF), but the calculation of the mean pixel value using the neighboring pixels in a kernel selectively applied a threshold value based on the noise of the image. The SMF method was evaluated using images of phantoms. The dose reduction was estimated by comparing the image noise acquired with a lower dose after implementing the SMF method and the noise in the original image acquired with a higher dose. For comparison, the images were also filtered with an adaptive mean filter (AMF) and a bilateral filter (BF). The spatial resolution of the image filtered with the SMF was similar to the original images and the images filtered with the BF. While using the AMF, spatial resolution was significantly corrupted. The noise reduction achieved using the SMF was up to 75%, while it was up to 50% using the BF. SMF significantly reduces the noise and preserves the spatial resolution of the image. The noise reduction was more pronounced with BF, and less pronounced with AMF.

Global health authorities are trying to work out the current status of the novel coronavirus (COVID-19) outbreak and explore methods to reduce the rate of its transmission to healthy individuals. In this viewpoint we provide insights concerning how health care professionals can unintentionally shift the novel coronavirus type to more drug-resistant forms. It is worth noting that viruses usually have different sensitivities to physical and chemical damaging agents such antiviral drugs, UV and heat ranging from extremely sensitive (ES) to extremely resistant (ER) based on a bell-shaped curve. Given this consideration, the widespread infection of people with such ER viruses would be a real disaster. Here, we introduce a modified treatment method for COVID-19-associated pneumonia. In this proposed method, COVID-19 patients will receive a single dose of 100, 180 or 250 mSv X-ray radiation that is less than the maximum annual radiation dose of the residents of high background radiation areas of Ramsar that is up to 260 mSv. In contrast with antiviral drugs, a single dose of either 100, 180 or 250 mSv of low LET X-rays cannot exert a significant selective pressure on the novel coronavirus (SARS-CoV-2) and hence does not lead to directed accelerated evolution of these viruses. Moreover, Low Dose Radiation (LDR) has the capacity of modulating excessive inflammatory responses, regulating lymphocyte counts, and controling bacterial co-infections in patients with COVID-19.

Radiosensitization using nanoparticles is proposed as a novel strategy for treatment of different cancers. Superparamagnetic iron oxide nanoparticles (SPIONs) have been reported to enhance effects of radiotherapy in several researches. The objective of this research is to investigate the radiosensitization properties of polyglycerol coated SPIONs (PG-SPIONs) on U87-MG cancer cells. In this experimental study, polyglycerol coated SPIONs were synthesized by thermal decomposition method and characterized by FTIR, TEM and VSM analysis. Cellular uptake of nanoparticles by cells was examined via AAS. Cytotoxicity and radiosensitization of nanoparticles in combination with radiation were evaluated by MTT and colony assay, respectively. Mean size of nanoparticles was 17.9±2.85 nm. FTIR verified SPIONs coating by Polyglycerol and VSM showed that they have superparamagnetic behaviour. Viability significantly (P < 0.001) decreased at concentrations above 100µg/ml for SPIONs but not for PG-SPIONs (P > 0.05). Dose verification results by TLD for doses of 2 and 4 Gy were 2±0.19 and 4±0.12 Gy respectively. The combination index for all situations was less than 1 and the effect is antagonism. However, PG-SPIONs combination with 6 MV X-ray reduced survival of U87-MG cells compared to radiation alone but the effect is antagonism.

Coronary computed tomography angiography (CCTA) is an important modality in diagnosis of coronary artery disease (CAD). Owing to the fact that computed tomography (CT) examinations are performed using ionizing radiation; applying radiation dose-reduction strategies seems to be necessary. Lowering tube voltage (in kV) according to the patient’s body mass index (BMI) or weight is an approach that is investigated by many researchers. The goal of this study was to evaluate the impact of low tube voltage CCTA on radiation dose and image quality in order to decrease radiation dose in selected patients who meet inclusion criteria of the introduced protocol.

Patients with clinical indications of CCTA who met inclusion criteria were classified in two groups randomly. Imaging of two groups was performed using 120 kV and 100 kV, respectively. Subjective and objective parameters of image quality and radiation dose of two groups were measured. Afterward, data were analyzed by appropriate statistical tests using SPSS software.

While differences in image quality between two groups were not significant, radiation dose of patients who underwent 100 kV CCTA was significantly lower than the other group. Effective doses (EDs) of first and second groups were 22.30 ± 5.48 mSv and 13.82 ± 2.00 mSv, respectively (P < 0.001).

Lowering tube voltage in non-obese patients is an effective and practical approach to radiation dose reduction without missing image quality that should be considered especially for female patients.

This study aims to investigate radiation beam geometry of Cyberknife beam and change in dosimetric characteristics of six megavoltage (6MV) flattening filter free (FFF) beam after passing through high density cadmium free compensator alloy.

In this experimental study, changes in FFF beam dosimetric characteristics after passing through compensator alloy was measured. Transmitted intensity of FFF beam was measured in air by an ion chamber at a source to detector distance (SDD) of 800mm. Extended SDD measurement also has been performed at a distance of 1270mm to analyze scattering due to compensator. Linear attenuation coefficient (µeff) was measured for cadmium free compensator alloy using simple exponential attenuation model. Percentage depth doses (PDDs) have been measured by a radiation field analyzer with compensator material to observe the beam hardening and change in surface doses and depth doses.

Linear attenuation coefficient of compensator alloy was measured 0.042 (Standard Deviation ±0.00099) mm-1 and it was found that there is no change with increase in collimator size. Even after increasing distance source from detector, µeff has no change. PDDs were found to increase with thickness of compensator. PDD from a 60mm collimator size increased by 5% and 6% at a depth of 100mm and 200mm, respectively in water. PDD also increased with collimator size less significantly. Surface dose was found to decrease with increase in compensator thickness.

Cyberknife beam has been found to be narrow beam geometry. FFF beam contains lesser scattered photons. Presence of high density compensator filters out the soft x-ray photon causes significant dosimetric changes.

Panoramic imaging is one of the most common imaging methods in dentistry. Regarding the side-effects of ionizing radiation, it is necessary to survey different aspects and details of panoramic imaging. In this study, we compared the absorbed x-ray dose around two panoramic x-ray units: PM 2002 CC Proline (Planmeca, Helsinki, Finland) and Cranex Tome (Soredex, Helsinki, Finland).

In this cross-sectional study, 15 thermoluminescet dosemeters (TLD-100) were placed in 3 semi-circles of 40cm, 80cm and 120cm radii in order to estimate x-ray dose. Around each unit, the number of TLDs in each semi-circle was 5 with equal intervals. The center of semicircles accords with the patient’s position. Each TLD was exposed 40 times. These dosemeters were read out with a Harshaw Model 4000 TLD Reader (USA). The calibration processing and the reading of dosemeters were performed by the Atomic Energy Organization of Iran.

The mean absorbed dose in three lines of PM 2002 CC Proline was 123.2±15.1, 118.0±11.0 and 108.0±9.1 µSv, (p=0.013). The results were 140.4±15.2, 120.2±10.4 and 111.6±11.2 µSv in Cranex Tome (p=0.208), which reveals no significant difference between two systems.

There are no significant differences between the mean absorbed dose of surveyed models in panoramic imaging by two units (PM 2002 CC Proline and Cranex Tome). These results were less than occupational exposure recommended by ICRP, even at the highest calculated doses.

The present study was conducted to implement a simple practical independent quality check of depth dose and isotropy of the Intrabeam™ therapeutic X-ray machine using radiochromic EBT2 film. Theindependent quality check of 1.5, 3.5, and 5-cm spherical Intrabeam™ applicators was accomplished using particular EBT2 film cutting pieces with internal rounded edges in a water phantom. Prior to this measure, the film was calibrated at three distances from the 5-cm applicator in water to clarify the effects of beam spectrum and dose rate alteration on film response. To this end, three calibration curves were plotted. The results of the one-way analysis of variance showed a critical difference between film pieces receiving equal doses at various distances (P<0.05). Therefore, depth dose curves were designed using all three calibration curves. Smaller applicators represented steeper dose fall-off, compared to the larger sizes. In this regard, 14.97%, 17.59%, and 30.92% of the relative mean doses were measured at 1 cm depth of 1.5-cm, 3.5-cm, and 5-cm applicators, respectively. A 10%/1mm gamma index was satisfied for the lateral dose evaluation of corresponding depth relative to Z-direction. The approach implemented in this study could be carried out as a rapid monthly quality check method for the dose distribution evaluation oftheIntrabeam device.

Whole spine scanography (WSS) is a radiologic examination that requires whole body X-ray exposure. Consequently, the amount of patient radiation exposure is higher than the radiation dose following routine X-ray examination.

Several studies have evaluated the patient effective dose (ED) following single exposure film-screen WSS. The objective of this study was to evaluate patient ED during WSS, based on the automatic image pasting method for multiple exposure digital radiography (APMDR). Further, the calculated EDs were compared with the results of previous studies involving single exposure film-screen WSS.

We evaluated the ED of 50 consecutive patients (M:F = 28:22) who underwent WSS using APMDR. The anterior-posterior (AP) and lateral (LAT) projection EDs were evaluated based on the Monte Carlo simulation.

Using APMDR, the mean number of exposures was 6.1 for AP and 6.5 for LAT projections. LAT projections required more exposures (6.55%) than AP projections. The mean ED was 0.6276 mSv (AP) and 0.6716 mSv (LAT). The mean ED for LAT projections was 0.6061 mSv in automatic exposure control (AEC) and 0.7694 mSv in manual mode. The relationship between dose-area-product (DAP) and ED revealed a proportional correlation (AP, R2 = 0.943; LAT, R2 = 0.773). Compared to prior research involving single exposure screen-film WSS, the patient ED following WSS using APMDR was lower on AP than on LAT projections.

Despite multiple exposures, ED control is more effective if WSS is performed using APMDR in the AEC mode.