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Showing 56 results for Computed Tomography
Dr. N.n. Jibiri, A.a. Adewale,
Volume 12, Issue 1 (1-2014)
Abstract
Background: One of the means of assessing dose to patients from Computed tomography (CT) procedure is through the determination of the skin entrance dose (ESD) with the appreciation of the concern that ocular exposure effects from CT scan includes possible induction of cancer and cataract. Due to the relatively more recent introduction of CT scans, little work has been done in this area in the country including exposure dose on the lens of the eyes of patients undergoing Cranial Computed Tomography (C-CT). Materials and Methods: The Entrance Surface Dose (ESD) to the lens of eyes of 26 patients who had cranial CT procedures at a University Teaching Hospital in Ile-Ife, Nigeria has been determined in order to assess the level of radiation protection compliance and optimization of radiation safety at the hospital. Results: Results indicate that the doses to the patients ranged between 17.13 mGy and 51.98 mGy within the period under study. The average doses obtained for the pediatric patients (1.5-18 yrs), young adults (19-49 yrs) and adults (&ge50 yrs) were 31.14 ±11.02 mGy, 41.81±12.60 mGy and 31.97 ± 11.31 mGy respectively. The mean dose obtained in this study was lower than threshold for lens damage, therefore the dose recorded in this study is clinically safe. Conclusion: This study represents a requisite pedestal on the need for a nation-wide evaluation and investigation of optimization of procedures in radiological examinations with a view to establishing a national dosimetry protocol and reference dose level or guidance level in the country.
A. Janbabanezhad-Toori, Dr. M.r. Deevband, A. Shabestani-Monfared, R. Abdi, M. Nabahati,
Volume 14, Issue 3 (7-2016)
Abstract
Background: Computed Tomography (CT) is main contributor of population dose from diagnostic X-ray examinations. Children are more radiosensitive than adults, thus optimization of CT examination in these patients is essential. The purpose of this study was to evaluate dose delivered to pediatric patients’ undergoing CT examination of the common examinations and also establishing local Diagnostic Reference Levels (DRLs). Materials and Methods: Questionnaires were designed for data collection at seven public hospitals and information about patient, protocol and CT system were recorded during 2013 and 2014. Dose measurement was performed in four age groups: 0-1, 1-5, 5-10 and 10-15 years old and two CT dose quantity including CTDIw and DLP were calculated. Results: Values of 40, 48, 59.5, 59.5 mGy; 16.9, 16.9, 17.14, 17.14 mGy; 17, 17, 17, 17 mGy; 17, 17, 19.2, 19.2 mGy in terms of CTDIw and 448, 538, 758, 758 mGy cm; 129, 129, 154, 167 mGy cm; 184, 225, 306, 315 mGy cm; 289, 408, 595, 670 mGy cm in terms of DLP as regional DRL for brain, sinus, chest, abdomen and pelvic examinations were obtained respectively. Conclusion: The variations in dose of some examination were considerable. As the role and usage of CT technology continues to expand, it is important that all practitioners adapt optimized protocols, especially for pediatrics scanning, following proposed reference levels
C.l. Lai, M.j. Lai, C.h. Liu, C.c. Wu, S.w. Jao, Dr. C.w. Hsiao,
Volume 14, Issue 4 (10-2016)
Abstract
Background: This study assessed the optimal timing of computed tomography for detection of metastatic disease in locoregional lymph nodes in patients with rectal cancer who have undergone chemoradiotherapy. Materials and Methods: This observational retrospective study was performed in a single institution. All patients with locally advanced rectal cancer treated with chemoradiotherapy, followed by a total mesorectum excision from January 1, 2003 to December 31, 2012, were included. Lymph node metastases evident on preoperative computed tomography were compared with postoperative pathologic lymph node status. Results: The study population consisted of 108 patients: Group A (nodal negative on preoperative computed tomography, n = 52) and Group B (nodal positive on preoperative computed tomography, n = 56). Analysis of the computed tomography scans in Group A revealed a high ability (98.07%) to predict negative lymph nodes, compared to 58.92% for predicting positive lymph nodes in Group B. Conclusion: The results of this study suggest that the optimal timing of computed tomography for assessing lymph nodes after neoadjuvant chemoradiotherapy for rectal cancer is after 6 weeks; this timing might be key for prediction of complete clinical responses.
Gh.r. Fallah Mohammadi1, Dr. N. Riyahi Alam, Gh. Geraily, R. Paydar,
Volume 14, Issue 4 (10-2016)
Abstract
Background: This study presents patient specific and organ dose estimation in computed tomography (CT) imaging of thorax directly from patient CT image using Monte Carlo simulation. Patient's CT image is considered as the patient specific phantom and the best representative of patient physical index in order to calculate specific organ dose. Materials and Methods: EGSnrc /BEAMnrc Monte Carlo (MC) System was used for CT scanner simulation and DOSXYZnrc was used in order to produce patient specific phantom and irradiation of photons to phantom in step and shoot mode (axial mode). In order to calculate patient thorax organ dose, patient CT image of thorax as voxelized phantom was divided to a 64x64x20 matrix and 6.25 x 6.25 x 6.25 mm3 voxel size and this phantom was imported to DOSXYZnrc code. MC results in unit of Gy/particle were converted to absorbed dose in unit of mGy by a conversion factor (CF). We calculated patient thorax organ dose in MC simulation from all irradiated slices, in 120 kV and 80 kV photon energies. Results: Effective dose was obtained from organ dose and organ weighting factor. Esophagus and spinal cord received the lowest, and bone received the highest dose. In our study, effective dose in CT of thorax was 7.4 mSV and 1.8 mSv in 120 and 80 kV, respectively. Conclusion: The results of this study might be used to provide the actual patient organ dose in CT imaging and calculation of real effective dose based on organ dose.
A. Saravanakumar, K. Vaideki, Dr. K.n. Govindarajan, B. Devanand, S. Jayakumar, S.d. Sharma,
Volume 14, Issue 4 (10-2016)
Abstract
Background: To suggest South India CT diagnostic reference levels (DRLs) by collecting radiation doses for the most commonly performed CT examinations. Materials and Methods: A pilot study investigated the most frequent CT examinations. 110 CT sites were asked to complete a survey booklet to allow the recording of CT parameters for each of 3 CT examinations during a 1 year time period. Dose data such Volumetric Computed Tomography Dose Index (CTDIv) and Dose length product (DLP) on a minimum of 50 average-sized patients in each category were recorded to calculate a mean site CTDIvol and DLP value. The rounded 75th percentile was used to calculate a DRL for each site and the region by compiling all results. Results are compared with international DRL data. Results: Data were collected for 16,500 patients. All equipment had multislice capability (2-256 slices). DRLs are proposed using CTDIvol (mGy) and DLP (mGy.cm) for CT head (47 and 1041 respectively), CT chest (10 and 445 respectively), and CT abdomen (12 and 550 respectively). These values are lower than current DRLs and comparable to other international studies. Wide variations in mean doses are noted across the region. Conclusion: Baseline figures for South India CT DRLs are provided on the most frequently performed CT examinations. It was noted that there was a wide variation in mean doses among the CT scanners used during diagnosis. The differences in CT doses between CT scanner departments as well as identical scanners suggest a large potential for optimization of examinations.
S. Azimi, Prof H. Mozdarani, A. Mahmoudzadeh,
Volume 15, Issue 2 (4-2017)
Abstract
Background: Medical diagnostic procedures such as X-ray and computed Tomography (CT) scan account for considerable percent of patient's exposure to ionizing radiation. The exposure of cells to Ionization radiation results in induction of DNA damage and chromosomal aberrations. Contrast media (CM) are widely used in diagnostic radiology and CT scan. The aim of this study was to study adverse genetic effects of combined administration of non ionic contrast media and low dose X-rays in peripheral blood Lymphocytes of patients following abdominal CT scan. Materials and Methods: A total of 55 patients underwent abdominal CT scan with injection of non ionic contrast media (30 patients with omnipaque 300 mg/ml and 25 patients with visipaque 270 mg/ml) as well as 13 patients undergoing abdominal CT scan (without contrast), selected as control group, were enrolled in this study. Peripheral blood leukocytes were obtained in heparin containing tubes and cultured for the micronucleus test, or were directly used for apoptosis and DNA damage with the neutral comet assay. Results: The frequency of micronuclei, apoptosis and percentage of DNA damage was increased in most patients after the injection of contrast media, significantly different from the control group as compared with the samples obtained before and after injection of contrast media (P<0.05). Conclusion: The present study suggest that non ionic contrast media (omnipaque 300 mg/ml and visipaque 270 mg/ml) may cause a significant increase of cytogenetic damage in peripheral blood lymphocytes. This effect might be caused by the enhancement of radiation dose by CM that eventually may lead to the manifestation of ill health such as cancer.
C. Gong, Dr. X. Tang, S. Fatemi, H. Yu, W. Shao, D. Shu, C. Geng,
Volume 16, Issue 1 (1-2018)
Abstract
Background: Boron neutron capture therapy (BNCT) is a binary radiotherapy combining biochemical targeting with neutron irradiation. However, monitoring the boron distribution is a fundamental problem in BNCT. Prompt gamma rays emitted by boron capture reaction can be used to address the issue. Materials and Methods: The general-purpose Monte Carlo toolkits Geant4 and MCNP were used for the simulations. A cubic phantom with soft tissue was used to study the prompt gamma emission during BNCT. The Chinese hybrid phantom with arbitrary tumors was constructed and used to acquire the 0.478 MeV prompt gamma rays in BNCT. Tomographic images were reconstructed with the maximum likelihood expectation maximization (MLEM) algorithm. Results: Comparison between MCNP and Geant4 showed a similar gamma rays emission rate in soft tissue. Up to 30 gamma ray peaks were found in the simulation, and 0.478 MeV prompt gamma ray from boron was clearly observed. The single brain tumor with variable diameter from 1 cm to 4 cm in the heterogeneous anthropomorphic phantom was each time found to be recognizable in the reconstructed image. Furthermore, in a patient with four tumors, the variable distance between the source and the tumors leads to a neutron attenuation thus resulting in an inhomogeneous number of prompt gammas. Conclusion: The SPECT system for a heterogeneous phantom in BNCT was simulated with Geant4. The results show that BNCT-SPECT is valid for the reconstruction of the boron capture interaction position for a heterogeneous patient.
Dr. A. Chaparian, H. Karimi Zarchi,
Volume 16, Issue 1 (1-2018)
Abstract
Background: Computed tomography angiography (CTA) scan is a suitable imaging technique to evaluate the blood vessels. However, one major disadvantage is the potential risk of cancer related to ionizing radiation exposure during the procedures. The aim of this investigation was to estimate the risk of exposure induced cancer death (REID) values for some common computed tomography angiography (CTA) scans. Materials and Methods: The scan parameters and patient gender and age were collected for a total of 251 patients undergoing CTA scans of the head (51), carotid (50), abdomen (50), thoracic (50) and the lower extremities (50). The effective diameter, scan length, effective tube current and the dose-length product (DLP) values were obtained for each patient. The organ doses and the effective dose were calculated by the ImpactDose program. The REID values were estimated for the different CTA scans by the calculated organ doses and corresponding age- and sex- specific risk factors. Results: The REID values for the CTA scans of head were 17±4 and 20±3 per million, carotid were 35±9 and 67±14 per million, the lower extremities were 60±26 and 64±24 per million, thoracic were 97±28 and 204±72 per million, and for abdomen were 101±25 and 194±72 per million, for males and females, respectively. Conclusion: The results of this investigation showed that CTA scans are associated with non-negligible risk of exposure induced cancer. A variation in radiation cancer risk as a function of age and gender of the patients was demonstrated and found that the younger female patients were at the highest risk.
Y. Salimi, Ph.d. M.r. Deevband, P. Ghafarian, M.r. Ay,
Volume 16, Issue 4 (10-2018)
Abstract
Background: Positron Emission Tomography-Computed Tomography (PET-CT) is a useful hybrid imaging modality in the diagnosis of various malignancies. This modality imposes almost 20 mSv radiation dose to the patient. The purpose of the present study was to evaluate the uncertainties in calculated CT effective dose in TUBE CURRENT MODULATION-activated scans by Impact-Dose software. Materials and Methods: Sixty total body DICOM (30 male and 30 female) whole body PET-CT images were selected. Volume CT Dose Index (CTDIvol) was recorded for each of the procedures. The image was divided into 5 regions of head & neck, chest, abdomen, pelvis and lower limbs according to special anatomical markers. Effective doses for total body and separate organs were calculated by means of Impact-Dose software once with global CTDIvol and once with a summation of doses calculated by 5 Regional CTDIvol and related scan ranges. Results: The difference among effective doses for some organs and total body were considerable. The mean and standard deviation (SD) of the coefficient of variations (CV%) for total body, breast, gonads, liver, lung, red bone marrow (RBM), thyroid, kidneys, and uterus were 12.56, 11.61, 9.44, 8.1, 11.31, 5.93, 8.61, 6.03 and 12.49, respectively. Uncertainties were higher for smaller patients by 19 noise indexes while these changes were higher for bigger patients and 22 noise indexes. Conclusion: The tube current variation depends on the acquisition and patient parameters. For measuring and reporting the total body and organs’ effective doses in order to estimate the risks of CT’s radiation for total body PET-CT procedures, the tube current variations must be considered.
R. Afzalipour, H. Abdollahi, M.s. Hajializadeh, S. Jafari, Ph.d, S.r. Mahdavi,
Volume 17, Issue 3 (6-2019)
Abstract
Background: The Diagnostic reference levels (DRLs) play a critical role in the optimization of radiation dose especially, in some conditions like pediatrics. They are useful indicators by which the radiologists can be aware of delivered excess radiation doses to the patients, and take corrective actions if necessary. In order to meet some requirements for establishing the national computed tomography DRLs tables, much studies are needed all around the country. Materials and Methods: All active computed tomography (CT) scanners in public and private centers in Tehran were identified and checked for quality assurance and control certification. Eleven centers were chosen to be studied according to CT examination frequencies. Weighted CT dose index (CTDIw) and dose length product (DLP) for head, sinus, chest and abdomen/pelvis scans of children were obtained from scanner’s operator consoles and classified into four groups based on their ages (A; <1 year, B; 1-5 years, C; 5-10 years and D; 10-15 years). The 3rd quartiles of CTDIw were considered as DRLs and compared with the reported European :::union::: (EU) and United Kingdom (UK) ones. Results: DRLs for head, sinus, chest and abdomen/pelvis scans were found to be 86.76, 31.33, 6.33, 7.65 mGy; 43.38, 31.33, 6.33, 7.65 mGy; 43, 31.33, 6.33, 7.65 mGy and 44.53, 31.33, 6.33, 7.65 mGy in the four groups (A-D) respectively. They are lower than the reported DRLs in EU and UK. Conclusion: There are variations in the radiation dose between the CT centers and identical scanners indicating the necessity for dose optimization. The data reported in this study can be remarkably useful in this concern.
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