جستجوی مقالات مرتبط با کلیدواژه "توموگرافی کامپیوتری" در نشریات گروه "پزشکی"

 In this investigation, the position of the root apex of the maxillary second premolar and first molar teeth with the sinus floor was investigated using the Cone beam computed tomography (CBCT) method.

 In this descriptive-analytical study conducted in 2022-2023, 172 CBCT stereotypes were analyzed, including the first molar and second premolar of patients aged 20 to 60 at the radiology department of Isfahan Azad Dental School. The position of the apex of the teeth was checked in the sagittal and coronal planes. The state of the apex was divided into three categories based on the distance to the floor of the sinus: OS (root apex outside the sinus floor), CO (apex in contact with the sinus floor), and IS (apex inside the sinus floor) which reviewed by researchers, radiologists and endodontists, and the data were analyzed by Mann-Whitney test at the significance level of 0.05%.

 The OS position was the most common posterior root apex with a sinus floor. The highest amount was in the second premolar, and the lowest was in the palatal root of the upper first molar. IS position was most in the palatal root of the first molar and the least in the root of the second premolar. The position of the CO was observed predominantly in the mesiobuccal and distobuccal roots equally, and the lowest percentage was seen in the second premolar teeth. There was no significant difference in the position of the apex of the roots compared to the floor of the maxillary sinus between women and men, and age did not affect the position of the apex of the roots of the teeth (p value < 0.05).

 The apex of the roots of the maxillary first molar is closer to the sinus than the apex of the maxillary second premolar. The frequency of the roots whose apex was far from the sinus floor was more than the roots that were inside the sinus.

Craniometric differences have been demonstrated in different population and ethics under pathologic and normal situations. Using the medical images such as computer tomography is an accurate method for anthropometry of the skull and face. Anthropometric data are used in medicine in the screening, diagnosis, follow-up and treatment of diseases. The aim of the present study was to perform anthropometric measurements in order to determine the craniometric indices of the base of the skull in both males and females in Ilam.

In this study, 200 head CT scan images (100 men and 100 women, 35 to 50 years old) were collected from the PACS system of Imam Khomeini Hospital of Ilam. Anthropometric measurements including four linear measurements and three angular measurements were performed on these images. Cranial index was also calculated. The data were analyzed by SPSS 22 software using a p-value less than 0.05. 

A significant difference was observed in all linear measurements between males and females (p=0.0). In the angular measurements, on the other hand, only one angle showed a significant difference between males and females (p<0.05). Also, the the cranial index did not show a significant difference between two genders (p>0.05). In addition, categorization of the skulls based on the cranial index showed that 71% of people were mesocephalic, 17% were brachycephalic and 12% were dolichocephalic.

The present study recorded some useful data about the anthropometric ind of the skull in Ilam population, which can be used in research and clinic.

Due to the limitations of CT imaging, it is necessary to use magnetic resonance imaging (MRI) as a complementary method in the treatment planning process. This study aimed to compare contouring and treatment planning based on MRI/CT images with contouring and treatment planning based on CT images in the treatment of rectal cancer using helical tomotherapy.

In this prospective study, 12 patients with rectal cancer underwent MRI diagnostic imaging and CT imaging was also performed at an interval of one day. The contouring process was performed for each patient based on both methods. After that, a dose of 45 Gy was delivered to the planning target volume (PTV). Finally, the size of the treatment volumes and the parameters Dmean, V45, HI, CI, and D98% were extracted and compared from the treatment planning system.

CT-based contouring method compared to MRI/CT-based method showed higher averages for treatment volumes. In addition, in CT-based plans compared to MRI/CT-based plans, the average CI, V45, and D98% were significantly lower and the average HI was significantly higher.

The results of this study show that contouring based on MRI/CT images can estimate the size of treatment volumes smaller than contouring based on CT. Also, treatment plans based on MRI/CT images can provide more appropriate dose coverage for PTV.

Timely diagnosis of patients with suspected COVID-19 using chest Computed tomography (CT) scan is of great benefit in reducing the severity of the disease. Previous studies did not address this issue, so, this study aimed to investigate the findings of chest CT scan images and the severity of lung involvement in patients hospitalized with COVID-19.

We performed a retrospective descriptive-analytical study in all patients admitted to Qaemshahr Razi Hospital with symptoms of COVID-19 and positive RT-PCR test results in 2019-2020. All chest scans were reviewed and reported by a radiologist. Data were analyzed using Chi-square and t-test.

The patients (n= 666) included 51.36% women and 48.64% men. The mean age of patients was 54.06±16.55 years. Moderate lung involvement was more common and ground-glass opacity (GGO) was the highest encountered pattern (39.33%). Also, in severe lung involvement, GGO pattern was found to be more prevalent (22.37%). Minimal lung involvement (0-25%), moderate lung involvement (25-50%), and sever lung involvement (> 75%) were seen in 6.75%, 22.29%, and 20.27%, respectively. Most of the patients were highly suggestive of COVID-19 and moderate lung involvement (45.97%) was found to be higher in this condition. No significant difference was seen between the extent of lung involvement in patients studied (P= 0.535).

The CT scan results in our patients in Mazandaran province with COVID-19 showed primarily GGO followed by consolidation and crazy paving patterns.

Using computed tomography (CT) scan may cause complications in the eye lens, thyroid gland, and breasts. One of the radiation protection methods to protect patients from unnecessary and unintended exposures is utilizing non-lead shields in CT-scan tests. Before designing and using these shields, it is necessary to study their performance by a simulation.

Bismuth, tungsten, and tin with absorption edges in diagnostic radiology energy ranges were selected for this research. Each of the metals along with the silicon was used as building blocks in the Monte Carlo simulation. To determine the mass attenuation coefficient of the samples, the beam was simulated as single energy. The energy range was selected according to the common imaging tests in diagnostic laboratories from 20 to 140 keV with 20 keV steps. The flat photon source with a radius of 5 mm was placed at the origin of the geometry. Information obtained from the simulation could specify that the shield had the most attenuation coefficient at which energies.

The shield containing 10% bismuth and 90% silicon showed more attenuation in the energies above 100 keV. Tungsten and tin shields also showed greater attenuation at medium and low energies.

By using the effect of attenuation window and selecting proper percentage and metal for the energy applied in diagnostic radiology, patients can be protected from radiation exposure to radiosensitive superficial organs.

Computed tomography (CT) scan of the chest is a common tool for imaging in pneumonia that is relatively easy and quick to detect. The aim of this study was to determine and evaluate the different characteristics of CT scan of patients with COVID-19 in Ahvaz hospitals.

The present survey was a descriptive-analytical retrospective study conducted in 2020. The statistical population included all patients referred to Corona Specialized Hospital who had positive COVID-19 and RT-PCR test and are hospitalized for treatment. Of these, 40 (22 men and 18 women) were included in the study. Patients who refused a CT scan of the chest or hospitalization, any coronary syndrome, any aortic or pulmonary embolism, or who were reluctant to participate were excluded from the study. All scans were reviewed and reported by a radiologist. The collected data were analyzed using Chi-square and t-test.

Image analysis indicated that multiple involvement was observed in 37 cases (92.5%). Frosted glass opacity (GGO) was more observed in the posterior sections (p <0.001). Consolidation was more common in the posterior sections, with the posterior section of the right lower lobe (RLL) being more involved (p <0.001). Crazy paving was more common in part 6 of the right middle lobe (15%) (p <0.001). Halo and reversed halo were observed in only 1 patient (2.5) and 2 (5%), respectively.

In conclusion, a typical CT-Scan sign obtained for patients with COVID-19 in Ahvaz, Iran, was multipolar bilateral sub pleural ground-glass opacity (most seen in RLL posterior segment) followed by consolidation and crazy paving.

SARS-COVID-2 is a single-strand RNA, β-coronavirus strand that causes COVID-19 disease,which The virus has caused a worldwide epidemic. The new virus is responsible for the development of acute pneumonia and acute respiratory distress syndrome. Middle East Respiratory Syndrome is another type of coronavirus that originated in Saudi Arabia and has caused a regional epidemic. Despite some similarities between Covid 19 and other coronavirus-related diseases, some of its CT scan and clinical findings remain unknown. The aim of this study was to evaluate the differences between Covid 19 and Mers disease in different stages of the disease in terms of clinical aspects and CT scan.

For this review study, in order to identify related articles, among the databases of Pabmad, Google Sclar, Scopus and Web of Science with the keywords "COVID-19", "MERS-CoV", "Computed Tomography" and "Chest The search was completed and 30 articles were found. Among them, 21 English-language articles related to SARS were collected and relevant statistical information was collected.

At first glance, Covid 19 has a much lower mortality rate than MERS. The death rate is 3.2% in Corona and 4.24% in Mers. The most common radiological signs found in Covid 19 and Mercer are frosted glass (GGO), lung consolidation, and GGO coated lung consolidation. Fever, cough, headache and sore throat are the most common clinical symptoms of these two diseases and in the next categories of shortness of breath and ARDS are seen in patients with severe symptoms.

No statistically significant difference was seen in the mean number of chest CT scan findings between Covid 19 and MERS patients except in pleural effusion.

Accurate diagnosis of vertical root fracture (VRF) is a fundamental importance in endodontics. Because of poor prognosis of VRF, digital radiographs with two horizontal angles have limitations in VRF detection. Also, Gutta-percha can produce artifacts that impair CBCT scan accuracy. The aim of this study was to compare accuracy of CBCT and digital radiography system in vertical root fracture in endodentically treated teeth.

In this study, 60 endodentically treated single teeth were selected and randomly coded. The teeth were divided into two groups: 30 with induced root fracture and 30 with no fracture. CBCT scan and digital radiographs with two horizontal angles with a difference of fifteen degrees for all teeth were performed. Two observers assessed the CBCT images and digital radiographies for presence of VRF. The statistical analysis used in this study was Weighted Kappa.

CBCT had the highest sensivity (75.8) and specificity (90). Digital radiography with 68.3 sensitivity and 79.1 specificity were not as efficient as CBCT (P<0.05).

According to this study, the accuracy of CBCT seems to be higher than that of digital radiography in detecting VRF and provides the most reliable data in comparison of digital radiography.

For prevent damage to the roof anterior ethmoid during sinuses surgery, diagnostics connection of upper middle concha and shape this region is important. In addition, the expansion of the pneumatized middle concha (concha bulousa, CB) may affect the formation of the ethmoid roof. The aim of this study was to investigate the relationship between pneumatized middle concha and the anterior ethmoid roof dimensions by CT scan.
In this analytic cross-sectional study, coronal CT scans of 379 patients with sinusitis symptoms were consecutively investigated. In order to measure the width of the anterior ethmoid roof, two points were selected and considered as reference points in the anterior cranium including external and internal parts of the ethmoid roof on the first coronal slice. Then, the largest axial diameter of CB was measured.
Mean (±SD) axial diameter of the CB and width of the anterior ethmoid roof at the right side were respectively 3.78 (1.99) and 7.71 (1.31) mm (r= 0.17, P= 0.002). Mean (±SD) axial diameter of the CB and width of the anterior ethmoid roof at the left side were respectively 4.09 (2.24) and 7.73 (1.5) mm (r= 0.21, P Pneumotized middle concha and its size increase has a positive relationship with increase in the width of the anterior athmoid roof. This finding can be useful when planning for sinus surgeries to avoid iatrogenic damage to the ethmoid roof.

There are several techniques for reducing the delivered dose from CT (Computed tomography) scanning such as the automatic exposure control (AEC). This technique modulates the tube current regarding the patient size and weight. The aim of this study was to estimate the effect of the AEC on the radiosensitive organs effective doses in women undergoing chest CT scanning.
This study was a cross-sectional, analytical and quantitative study that was performed during 3 months in the imaging section of the Firoozgar educational and therapeutic hospital (belonging to Shahid Beheshti University of Medical Sciences) in the spring of 2017. CT scan exposure parameters were gathered and registered for 54 women undergoing chest CT scan. 25 of these scans were performed using AEC system and 29 of them were performed without using AEC. CT dose indexes in the center and peripheral regions of the standard phantom were calculated using the exposure parameters. Weighted CT dose index was also calculated and effective organ doses were obtained using CT-Expo software, version 2 (Medizinische Hochschule, Hannover, Germany) for two mentioned groups. In addition, noise was measured for these two groups as an image quality parameter.
Calculated weighted CT dose indexes were 9.94 mGy and 12.46 mGy using AEC system and without using AEC, respectively. The calculated effective doses were equal to 5.4 mSv and 6.3 mSv using AEC and without using AEC, respectively. Maximum organ effective doses were 15, 14, 14 and 14 mSv for breast, esophagus, lung and thymus respectively in the non-using AEC system imaging technique.
Our measurements indicated a decrease about 15% in weighted CT dose index (from 12.46 to 9.94 mGy) using AEC system. Beside of this fact, the noise increased about 11.3% (from 4.2 to 4.74) using AEC system. So, it can be said that using of AEC was an effective way for dose reduction in women undergoing chest CT scanning, and the additional noise was in the acceptable range.

Distribution of dose depends on the treatment field and the presence of multiple collimators sheet at the direction of the photons. The aim of this study is evaluating and comparing the effects of the presence and absence of electrons contamination on the dose distribution with the use of computed tomography.
Subjects and Varian linear accelerator (2100 C / D) was simulated with Primo and BEAMnrc codes for photon with 5.9 MV nominal energy. This study was done for 15 patients with eyes tumor undergoing single field photon therapy.
The maximum depth dose treatment volume aggregation in the presence and the absence of electrons contamination was occurred at 1.3cm3 and 2cm3, respectively. Differential dose volume histogram concluded 80% of total dose in the presence and absence of electrons, 90%±0.5 and 80%±2 of the eye volume covered, respectively.
The main goal of radiation therapy is delivering the highest dose to the planning treatment volume and minimal radiation dose to organs at risk. In this case, the percent of the eye and treatment volume which taken 80% and 90% dose has 10% reduction and 5% increased by removing electrons contamination, respectively.

Due to the presence of radiosensitive organs in the abdominopelvic region and increasing the number of requests for CT scan examinations, concerns about increasing radiation doses in patients has been greatly elevated. Therefore, the goal of this study was to determine the absorbed dose of radiosensitive organs and the effective dose in patients underwent abdominopelvic CT scan using ImPACT CT patient dosimetry Calculator (version 1.0.4, Imaging Performance Assessment on Computed Tomography, www.impactscan.org).
This prospective cross-sectional study was conducted in Imam Reza Hospital from November to February 2015 February 2015 in the Imam Reza Hospital, in Urmia, Iran. The demographic and dosimetric information of 100 patients who underwent abdominopelvic CT scan in a 6-slice CT scanner were obtained through the data collection forms. The demographic data of the patients included age, weight, gender, and BMI. The dosimetric parameters included pitch value, CT dose volume index (CTDIvol), dose-length product (DLP), tube voltage, tube current, exposure time, collimation size, scan length, and scan time. To determine the absorbed dose of radiosensitive organs and also the effective dose in patients, ImPACT CT patient dosimetry calculator was used.
The results of this study demonstrated that the mean and standard deviation (SD) of patient's effective dose in abdominopelvic CT scan was 4.927±0.164 mSv. The bladder in both genders had the greatest mean organ dose, which was 64.71±17.15 mGy for men and 77.56±18.48 mGy for women (P The effective dose values of this examination are in the same range as previous studies, as well as International Commission on Radiological Protection (ICRP) recommendations. However, the radiation dose from CT scan has the largest contribution to the medical imaging. According to the ALARA principle, it is recommended that the scan parameters, especially mAs, should be chosen so that the patient dose is minimum, and the image quality is maximum. Furthermore, other imaging modalities are used as an alternative to the CT scan.

Several factors affect the success rate of dental implants, including the quality of bone. Schwartz for the first time described the use of computed tomography (CT) to classify bone density. Cone-beam CT (CBCT) has replaced CT in various fields due to lower dose and cost. This study aimed to evaluate the effect of exposure factors on reliability of CBCT in determining density.
In this study, CT dose index phantoms including nine different concentrations of 76% meglumine with active ingredient of iodine were subjected to CBCT imaging with Planmecca 3D Mid under different exposure conditions. To obtain Hounsfield unit from CT, CT imaging from the phantoms was performed under standard conditions. Hounsfield unit and voxel values from CBCT and CT were recorded under all conditions, then, the difference and correlation between them was evaluated using paired-samples t-test and linear regression.
The results of this study showed excellent correlation between voxel values from CBCT and Hounsfield unit from CT (R=0.847). With changing the kVp conditions and mA this correlation remained high (R>0.8). There was no significant difference between the voxel values from CBCT and Hounsfield unit from CT under standard exposure conditions (P=0.6). However, variation in the amount of radiation exposure factors caused a significant change in CT and CBCT values, which could affect reliability of voxel values from CBCT (P=0.049).
Our findings exhibited no significant difference between voxel values from CBCT and Hounsfield unit from CT. Furthermore, changes in exposure factors can affect the reliability of voxel values.

Clinical and radiographic diagnosis of vertical root fracture is difficult. The aim of this study is to compare two different resolutions of CBCT and CMOS digital sensor for diagnosis of vertical root fracture. In this diagnostic in vitro study, 80 single rooted teeth were selected and after canal preparation were sectioned from 2 mm below the CEJ. The teeth were put in two groups 40 teeth with induced root fracture and 40 remained intact served as control samples. Teeth were put in dry mandible and 2 layers of wax was used as soft tissue. All samples were imaged by CBCT with two resolutions and CMOS sensor with 0,and ±15 degrees. Positive predictive value(PPV) and negative predictive values(NPV) of the techniques were calculated with Ratio test. The reliability in diagnosis of fracture in CBCT was 100% and the reliability in researcher in radiography was 75%. No significant difference was found between the two resolutions of CBCT, but there was a significant difference between CBCT and CMOS digital sensor(P<0.07). CBCT had higher ability in VRF detection comparing to digital radiography with CMOS sensor, while both resolutions of CBCT have same abilities

Total knee arthroplasty is an accepted method for treatment of osteoarthritis of the knee. Measuring the distal femoral rotation is one of the most important problems in such operations. In the conventional 2D method, measuring the angle is based on CT scan images but these methods usually contain errors. In this study, the three-dimensional measurement of the aforementioned angle was investigated.
In this research, using CT scans and 3D modeling, 3D lower extremity models of 40 patients were extracted. The rotation of distal femur was measured for plane perpendicular to the anatomical and the plane of mechanical axis of femur. Four axes were drawn on these planes using anatomical landmarks: posterior condylar line (PCL), anatomical and surgical transepicondylar line (ATEA䤱), and the Whiteside line (WL).
The mean difference of these measurements on the plane perpendicular to the mechanical axis of the femur, between PCL and WL, STEA, ATEA was 3.41, -1.31, 5.53; and angles on the plane perpendicular to the anatomical axis of femur were -0.74, -1.26, and 5.67, respectively. In addition, Bland-Altman diagram was plotted between every two measurements and no relationship found, except for STEA and ATEA.
The measurements between PCL, ATE, and STEA are not affected by the plane on which these measurements are carried out on, except for the 4 degrees difference present in WL axis. With a greater sample size and proper grouping, some relationship might be found between the aforementioned axes.

One of the training tools in health care is computer simulators; the purpose of this area of education is training outside the clinic in a manageable framework, and, in the field of health care, computed tomography simulator is a kind of educational software. This research was a cross-sectional study, and was conducted in order to compare the learning of radiology students using traditional training method with computed tomography simulator, moreover, to investigate their views about using simulators for training. In this regard, 61 students in the school of radiology were measured before training. Then, the population was divided randomly into two groups: one group was trained with a computerized tomography simulator and the other was trained by traditional method at hospital; subsequently, views of students trained by simulator software were measured. For data analysis, 20th-version SPSS software was used. Statistically significant differences between the scores within both groups before and after training were observed. The most important features of the simulator from Students’ perspective were: enhance readiness and reduce stress level before training, compatibility of simulator environment with real device protocols, and speed up learning. Outcomes of this study showed that computer simulators provided learning in a virtual environment can be adapted for training radiology students. Thus, professional skills can improve before facing a real patient.

The Panoramic radiography is one of the routine techniques in implant imaging. Although there are some limitations with this technique, panoramic radiography is radiographic choice for basic evaluation for implant treatment. Many studies have been designed to determine magnification in panoramic images but most of them were performed on dry skulls or radiographic phantoms. In recent studies CT or CBCT are used as gold standard. The aim of this study was to determine vertical magnification of panoramic images using renovated CT sections in anterior and posterior regions of both jaws. 30 panoramic radiographs (Planmeca EC or CC Proline) were selected from patients of implant department and Particular anatomic landmarks were selected in those images. Vertical dimensions of these landmarks were measured in both panoramic and renovated cross sectional CT images by a digital caliper and vertical magnification was calculated as the ratio of image dimensions to the real dimensions. The mean vertical magnification of panoramic radiographs in anterior and posterior maxillae were 1.22±0.02 and 1.16±0.02, respectively. The mean vertical magnification of panoramic radiograph in anterior and posterior mandible were 1.20±0.02 and 1.13±0.02, respectively. The differences between magnification in mandible and maxillae were significant (P<0.001). The differences between magnification in anterior and posterior regions of both jaws were not significant (P=0.11). Vertical magnification of panoramic images (Planmeca EC or CC Proline) in different regions in both jaws were between 1.13 to 1.22.

Cone beam computed tomography (CBCT) is an alternative to a CT scan in dental treatments. Metals used in dentistry may cause production of artifacts due to beam hardening phenomenon. The aim of this study was to compare the beam hardening artifacts produced in New Tom VG, PlanmecaPromax 3D, Max and Somatom Sensation 64-Slice CT. In this descriptive study an implant drilling model was used [IMP 1003-L-HD].The implants (Dentis) were placed in the canine, premolar and molar areas. The identical images were evaluated by two radiologists. The number of artifacts in each image was determined using the scale provide due to reference books Kruskal-Wallis test was used to compare mean values of data. NewTom VG had the maximum resolution (4.53±0.48) and PlanmecaPromax had the lowest resolution. (1.8±0.84). The results showed significant difference between the three Scanners (P<0.001). Given the high quality of the images produced by NewTom VG and the lower exposure dosesand costs in comparison to CT, the use of this scanner in dental procedures is recommended, especially in patients with extensive restorations, multiple prostheses and previous implants.

Both 2-dimentional and 3-dimentional computerized tomographies (CT) are useful for measurement of tissue volume and reconstruction of maxillofacial areas. The aim of this study was to compare these two modalities for volumetric measurement of maxillary sinus. This study was done on four human skulls obtained from the collections of department of anatomy. Sinus walls were sealed by rose wax and then actual volume of the sinuses were measure by water injection, as our gold standard. This measurement was performed three times for each sinus and the mean values of measurements were calculated. The skulls were also assessed radiologically by two dimensional and three dimensional CT. The results were compared by statistical methods. No significant difference was found between two-dimensional and three dimensional CT measurement with actual sinus volume (P>0.05). The difference between two aforementioned CT methods was also insignificant (P > 0.05). Volumetric measurements of maxillary by sinus two-dimensional and three-dimensional reconstructed image methods are reliable and accurate.