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Showing 9 results for Ctdi
F. Bouzarjomehri, M. H. Zare, D. Shahbazi,
Volume 3, Issue 4 (3-2006)
Abstract
ABSTRACT Background: While the benefits of Computed Tomography (CT) are well known in accurate diagnosis, those benefits are not risk free. CT is a device with higher patient dose in comparison with other conventional radiological procedures. Is the reduction of exposures by requiring optimization of CT procedures [a principle concern in radiological protection]? In this study, the radiation dose of conventional and spiral CT were investigated and compared with European Commission Reference Dose Levels (EC RDLs). Materials and Methods: The dosimetric quantities proposed in the European Guidelines (EG) for CT are Weighted Computed Tomography Dose Index (CTDIW) for a single slice for axial scanning or per rotation for helical scanning and Dose-Length Product (DLP) for a complete examination. The patient-related data were collected for brain, neck, chest, abdomen and pelvis examination s in each scanner. For each type of examination, 10 typical patients were randomly included. CTDI with an active length of 10cm was measured in two CT scanners by using UNFORS (Mult-O-Meter 601) in head and body phantom (PMMA) with 16 cm and 32 cm in diameter respectively. Mean values of CTDIW , DLP and Effective Dose(ED) were estimated for those examinations . Results: CTDIW had a range of 15.8-24.7 mGy for brain, 16.1-30.6mGy for neck, 6.8-9.2 mGy for chest, 6.8-9.8 mGy for abdomen and pelvis. DLP had a range of 246.4-397.7 mGy.cm for brain, 104.6-262.2 mGy.cm for neck, 135-248.4 mGy.cm for chest, 187-298.9 mGy.cm for abdomen and 197.2-319.4 mGy.cm for pelvis. The mean values of effective dose were 0.74 mSv for brain, 0.9 mSv for neck, 3.1 mSv for chest, 3.7 mSv for abdomen and 5 mSv for pelvis. Conclusion: The obtained results in this study have shown that CTDIW and DLP are lower than EC RDLs and other studies, in other words , the performance of all scanners has been satisfactory as far as CTDIw and DLP are concerned. The CTDIW and DLP in the conventional CT are higher than the spiral CT values . With regard to ALARA principle, for the establishment of reference dose levels, the radiation dose with spiral CT scanners should be taken into account.
Dr. F. Bouzarjomehri, M. H. Zare, D. Shahbazi-Gahrouei,
Volume 4, Issue 3 (12-2006)
Abstract
Background: With the introduction of computed tomography in diagnostic radiology a new and fundamentally different imaging modality has become available. Meanwhile, it is clear that the absorbed doses by the patients during CT were relatively high in comparison with those of other diagnostic radiology techniques. The aim of this survey was to determine the average absorbed dose in Yazd province by CT examinations, and to survey the potential risks per year by these examinations.
Materials and Methods: This study was conducted in CT centers of Yazd during 2005-2006. The examination frequencies from 3 CT scanners were collected from all types of examinations. Effective dose were determined by CT Dose program (ImPACT CT patient dosimetry calculator). To use of this software, CTDIair, mAs and the thickness and number of slices in each type of CT examinations should have been measured. CTDIair was measured by pencil diode detector.
Results: It was estimated that the annual collective dose and caput dose were about 32.48 Person-Sv and 0.038 mSv, respectively for the Yazd population, which is lower than that reported for other countries. The numbers of examinations per 1000 people of Yazd was 18 which were equal to many other countries such as UK and New Zealand. The mean effective dose of each CT examinations was also lower than that of other countries.
Conclusion: Using the ICRP risk factors, radiation dose from CT could be induced to about 1 fatal cancer per year in Yazd. Therefore choosing CT imaging must be completely justified.
S.m. Ghavami, Dr. A. Mesbahi, I. Pesianian,
Volume 10, Issue 2 (9-2012)
Abstract
Background: X-ray computed tomography (CT)
examinations deliver a significant amount of radiation
doses to patients comparing to conventional radiography
examinations. The objective of the current
study was to analyze and investigate the average
patient received dose from axial and spiral CT exams
in a medical imaging center. Material and Methods:
In this study, the patient imaging technique, weight
and height were recorded. The patients’ doses
provided by CT unit in terms of CTDIw were also
recorded. Then, other dosimetric quantities including
dose-length product (DLP) and effective dose were
calculated for each patient using the recorded data.
The average values were obtained for all the studied
dosimetric quantities. Also, their distribution in terms
of examined regions and imaging mode ie, axial and
spiral CT were analyzed by SPSS software. Results:
For all patients, the mean effective dose of 4.4 mGy
with the standard deviation of 9.2 was found. The
CTDIw for axial group was two times higher than spiral
ones. Conversely, the effective dose of axial group
was less than spiral group. Additionally, the effective
doses of 2.3 and 5.2 mSv were found for axial and
spiral, receptively. For both quantities of CTDIw and
effective dose, the observed difference between axial
and spiral modes were significant (P<0.001).
Conclusion: Our results showed that although the
patient doses in the current study was comparable
with the reported values by similar studies in other
countries, it was higher than the reported values of a
similar study in Iran. Exposure technique’s optimaization
and further review in routine CT examinations
were recommended. Iran. J. Radiat. Res., 2012 10(2):
89‐94
L. Sadri, Dr. H.r. Khosravi, S. Setayeshi,
Volume 11, Issue 4 (10-2013)
Abstract
Background: Patient radiation doses from computed tomography (CT) are increasing due to the number of CT examinations performed every day. The aim of this study was assess and evaluate patient radiation doses for adult’s common CT examinations to derive local diagnostic guidance levels for common CT examinations. Materials and Methods: Volume and weighted computed tomography dose index (CTDIvol,w) and dose length product (DLP) of four common CT examinations including head, head sinus, chest, abdomen and pelvis were measured for 8 different CT scanners using standard head and body phantoms. The image quality of acquired scan images were assessed according to European Commission (EC) image quality criteria guidelines. Results: The mean measured CTDIw for head base head cerebrum, head sinus, chest and abdomen-pelvis were 71.8, 29.7, 35.8, 9.8 and 12.9 mGy, respectively. The DLP for head, head sinus, chest and abdomen-pelvis were 500, 371, 225 and 482 mGy.cm. The results of our study were shown more patient doses in terms of DLP for head sinus in compare with other studies while CTDIw values for head base and sinus were higher than EC measurements. Conclusion: The great variations of CTDIw and DLP observed among hospitals and relatively high values of DLP in some centers are evidence that radiation doses of patients from CT examinations is not fully optimized. It was concluded that future studies of continues optimization to minimize the dose without affecting image quality are needed.
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.
Phd. C. Anam, F. Haryanto, R. Widita, I. Arif, G. Dougherty, D. McLean,
Volume 16, Issue 3 (7-2018)
Abstract
Background: In the tube current modulation (TCM) technique, tube current is changed dynamically during the scanning process. To quantify the effect of a dynamic tube current, a distinct calculator is needed to estimate the CT output radiation dose in terms of volume CT dose index (CTDIvol) and individual patient dose in terms of size-specific dose estimate (SSDE). This study developed a specific calculator for CT scanning using the TCM technique. Materials and Methods: The tube current was extracted from the DICOM header for every slice, and averaged over the scan length. The water equivalent diameter (Dw) and SSDE values were calculated for each tube rotation. The software was retrospectively applied to 57 patients who had undergone abdominal and thoracic CT examinations using a multi-detector CT, the Somatom Emotion 6. Results: The differences between the calculated CTDIvol and the CTDIvol reported by the CT scanner were 4.4 ± 1.2% and 6.0 ± 2.0% for abdominal and thoracic examinations, respectively. The average tube current was found to be linearly correlated with Dw with R2 values of 0.707 and 0.696 for abdominal and thoracic examinations, respectively. The average tube current was also linearly and strongly correlated with the SSDE with R2 values of 0.941 and 0.887 for abdominal and thoracic examinations, respectively. Conclusion: Calculator for estimating CTDIvol and SSDE specifically for TCM in CT scanning has been successfully developed. The difference between calculated CTDIvol values using this calculator and reported CTDIvol values were less than 10%.
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.
Ph.d., M.r. Deevband, M. Ghorbani, A. Eshraghi, Y. Salimi, E. Saeedzadeh, M.r. Kardan, S. Sadeghi, D. Divband, M. Ahmadi,
Volume 19, Issue 1 (1-2021)
Abstract
Background: The present study intended to determine and report patient effective dose on the basis of patients and exposure data. Materials and methods: A nationwide computed tomography (CT) survey was provided as a report of patient doses in 2015-2016. Scan details were collected for nearly 2,000 adults and children in four age groups subjected to CT examinations. From total 565 CT scanners in different models in Iran, 120 different scanners were sampled. ImpactDose software was used to calculate the effective dose (ED) by collecting the necessary data also as an alternative fast method, the ED was estimated by multiplying dose length product (DLP) and a conversion factor. Results: There was a high variation in doses received by patients. The estimated EDs by the DLP and conversion factor were lower (except for sinus protocol) than those by ImpactDose software (p=0.014). The mean EDs were 1.09, 0.66, 7.70 and 13.29 mSv for adult patients’ procedures of head, sinus, chest and abdomen-pelvis, respectively. In terms of CTDIvol and DLP, in Iran the mean effective doses were significantly lower than other countries. Conclusion: Publishing guidelines and exposure tables according to patient situations is necessary to decrease variations in doses and exposure parameters. Since the DLP conversion factor leads to a considerable discrepancy in calculating ED, when there is a need for precise dose calculations, the DLP conversion factor should not be used. Furthermore, it is suggested that ED be used as DRL, instead of CTDIvol.
Ph.d., Gh.r. Fallah Mohammadi, L. Hesamnezhad, M. Mahdavi,
Volume 19, Issue 4 (10-2021)
Abstract
Background: Conventional radiation dosimetry methods in computed tomography (CT) are not able to measure the dose distribution along the patient’s longitudinal axis. To calculate the dose index on a CT scan, the dose distribution from the center of the radiation field must be calculated. In this study, the most appropriate integral interval for calculating the CT dose index in the axial mode was determined using the Monte Carlo (MC) method based on X-ray photon energy and slice thickness. Materials and Methods: The computed tomography dose index (CTDI) phantom was simulated in the EGSnrc/BEAMnrcMC system and was irradiated with several X-ray energies and several slice thicknesses and dose profiles in phantom were investigated. The area under the dose profile and the scatter to primary radiation dose ratio (SPR) were calculated. Results: The range of scattered beams from the center of the radiation field reaches 450 mm in 140 kV and a 40 mm slice thickness. The SPR value for all levels of X-ray photon energy (between 80 and 140 kV) significantly decreases as slice thickness increases. CT scan imaging technical factors greater than 310 mm from the center of the slice thickness have no effect on the behavior of the scattered radiation. Conclusion: The primary beams are more affected by the energy of the photons, and the scatter beams are more strongly affected by the slice thickness. For 64-slice scanners, the polymethyl methacrylate (PMMA) phantom length should be between 700 mm and 900 mm to yield accurate CTDI estimations.
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