Background: CT techniques and procedures have been expanded in the past decades, leading to an increase in the use of CT. At the same time, the radiation dose to the patient and the concern surrounding this issue has also increased. Objectives: The goal of this study was to assess clinical image quality and x-ray dose from various computed tomography (CT) scanners in order to identify the CT scanners that produce the least radiation dose to patients with exact acceptable image quality for diagnosis. Patients and Methods: Non-randomized clinical image data were collected from six hospitals on 16, 32 and 64 slice CT scanners. A total of 900 patients who underwent chest, abdomen, and brain scans were used for image quality evaluation and dose assessment. The image qualities were evaluated by five observers on 1-5 visual grading scale. The CT dose volume index (CTDIV) and dose length product (DLP) was documented from the image display. Results: The averaged CTDIV was 64. 96, 70. 2, and 75 mGy for the brain, 11. 65, 15. 53 and 17. 11 mGy for the chest, and 13. 41, 18. 44, and 19. 42 mGy for the abdomen from 16, 32 and 64 slice scanners respectively. The averaged image quality scores were 3. 68, 3. 82, and 4. 81 for the abdomen, 3. 01, 4. 27, and 4. 42 for the chest, and 4. 92, 4. 94, and 4. 99 for the brain from 16, 32 and 64 slice scanners respectively. Conclusion: Sixteen slice CT scanner delivered the minimum radiation dose to patients in contrast with the 32 and 64 slice CT scanners, and the image quality was adequate for diagnosis. Both 32 and 64 slice CT scanners produced more than acceptable image quality as well as more than needed dose to patients. The patient dose from the 32 and 64 slice scannersmaybe reduced by dropping their image quality to close to the 16 slice CT scanner.

Primary and widely in use Computed Tomography (CT) dose descriptor is a volumetric CT Dose Index (CTDIV) that is usually measured by a pencil ionization chamber with active length of 100mm and polymethyl methacrylate (PMMA) phantom. CTDIV depends on scan parameters such as mAs, kV, collimation, tube rotation time but is independent of patient’s size and shape. For the purpose of a good estimation of dose received by the patients, American Association of Physicists in Medicine (AAPM) published the conversion factors for both 16 and 32cm (head and body phantoms respectively); through this, users can extract conversion factors according to lateral (LAT) and/or anterior-posterior (AP) sizes and calculate real CTDIV. Since this procedure is time consuming, we designed MATLAB-based software to reduce such calculations. To design the software, GUI toolbar of MATLAB software was used. To test the software, scan parameters of two patients for head and pelvis scan were read from PACS and lateral (LAT) and anterior-posterior (AP) sizes were measured. Finally, SSDEs were calculated for two patients by the software. The software can be measured based on AP and/or LAT measures and/or in special cases (under the age of 18) through patients’ age.

Background: Concern about radiation risk of computed tomography (CT) scan as a diagnostic modality has increased in recent years. Diagnostic reference levels (DRLs) is one of the tools to optimizing radiation dose of patients. CTDIV (Volume Computed tomography dose index) and DLP (Dose Length product) are used for assessment of DRLs. The CTDIV under/overestimate the patient dose. AAPM has introduced SSDE (Size-specific dose estimates) for estimation of patient. In this study, the DRLs of head and abdomen-pelvis CT examinations of adults is determined using CTDIV, DLP and SSDE. Materials and Methods: 680 CT examinations of head and abdomen-pelvis were collected from PACS (Picture archiving and communication system) in Imam Khomeini and Mostafa Khomeini hospitals. The Deff, CF and SSDE calculated using AAPM TG-204 and TG-220. Statistics analysis calculated using SPSS version 18. Results: For abdomenpelvis third quartile of CTDIV, SSDE and DLP was 9. 96, 13. 58 and 527 and values of 27. 62, 26. 79 and 402. 90 are determined for head, respectively that are lower than national DRLs. Also, calculated conversion factor (CF) for head and abdomen-pelvis was 0. 97 ±,0. 75and 1. 45 ±,0. 17, respectively. Conclusion: DRLs were lower than other studies in this study. Using the AEC (Auto Exposure Control) and different kVp in this hospitals can help optimization of patient dose. The SSDE must be calculable by radiographers to more accurate estimation of patient dose using CFs.

Introduction: Head scans are the most frequently performed computed tomography (CT) examinations worldwide. However, there is growing concern over the probability of increased cancer risks among the exposed populations. Diagnostic reference levels (DRLs) identify radiation dose that is not commensurate with clinical objectives. The aim of this study was to establish DRLs for CT head procedures and estimate effective dose (ED). Material and Methods: The dose absorbed by the head slice of a Rando Alderson phantom was measured using calibrated lithium fluoride thermoluminescent dosimeters (TLDs) exposed to a CT scanner operated on clinical parameters. The measurements were done at the periphery and center of the slice, and repeated twice with a new set of TLDs. The radiation dose absorbed by the TLDs was read using a Harshaw TLD reader, Model 5500. The measured doses were used to calculate the weighted CT dose index (CTDIw), CT dose index volume (CTDIV), and dose length product (DLP). Finally, the ED was calculated using the formula; ED = k × DLP, where k was considered as 0. 0021. Results: The mean absorbed dose was 30. 9 mGy, while the established CTDIV and DLP values for the head protocol were 40 mGy and 990 mGy. cm, respectively. Additionally, the ED was calculated as 2. 1 mSv. These values compared well with some international values. Conclusion: According to the results of the present study, the established CTDIV, DLP, and ED for head scan were well-compared with some international values, except in the cases using different scan lengths and scanner algorithms.

Computed tomography coronary angiography (CTCA) has generated a great interest over the past two decades, due to its high diagnostic accuracy and efficacy in the assessment of patients having coronary artery disease. This method is associated with high radiation dose and this has raised serious concerns in the literature. Effective dose (E) is a single parameter meant to reflect the relative risk from exposure to ionizing radiation. Therefore, it is necessary to calculate this parameter to indicate ionizing radiation relative risk. The aim of this study was to calculate the effective dose from 64-slice CTCA in Isfahan. To calculate the effective dose, an ionization chamber and a body phantom with diameter of 32 cm and length of 15 cm were used. CTCA radiation conditions commonly used in two centers were applied for this work. For all scans, computed tomography volume dose index (CTDIV), dose-length product (DLP), and effective dose were obtained using dose-length-product method. The obtained CTDIV, DLP, and effective dose were compared in two centers, and mean, maximum, and minimum values of effective dose for heart coronary CT angiography (CCTA) examinations and calcium score were compared with other studies. The amount of average, maximum, and minimum effective doses for heart CCTA examinations in two centers are 4.65 ± 0.06, 6.0489, and 3.492 mSv, respectively, and for calcium score test are, 1.04 ± 0.04, 2.155, and 0.98 mSv, respectively. CTDIV, DLP, and effective dose values did not show any significant difference in two centers. Although the effective dose of CTCA and calcium score was lower than that of other studies, it is reasonable to reduce the effective dose to the minimum possible value to reduce the risk of cancer associated with ionizing radiation. The results of this study can be used to introduce the effective dose as a local diagnostic reference dose (DRL) for CTCA examinations in Isfahan Province.

The work aimed at establishing DRLs for adult CT examination of the head in Rivers State, Nigeria. The dose report and scan parameters for adult Head examination was retrospectively surveyed during the study period of four months in three CT center. Sixty-nine patient folders, comprising twenty-five subjects for center A, twenty-three subjects for center B, and twenty-one subjects for center C were included. Data on CT dose index (CTDIVol) and dose length product (DLP) displayed on CT scanner console from three (3) selected hospitals were recorded for each facility. The percentile (75th) was assessed for all centers to set up center-unique DRLs. Lastly, a summed percentile (75th) for mean of DLP and CTDIV in the entire centers was assessed to obtain DRLs in adult Head examinations across investigated area. Facts were analyzed with the aid of SPSS (version 25.0). The modern files (digital) of 24 female and 45 male patients with age bracket 16-100 years old were analyzed. Centre-unique percentile (75th) of mean DLP and CTDIV of three centers A, B, and C were 39 mGy and 820 mGy.cm, 70.9 mGy, and 1330 mGy.cm, 55 mGy, and 1158 mGy.cm, respectively. The head CT examination DRLs for the area was 54.9 mGy and 1103 mGy.cm. The Head CT examination’s DRLs for the state of Rivers has been obtained. Nonetheless, variation between CT scan center was noted, CTDIVol is lower than recommendations of European Commission (EC) of 60mGy. The DLP is slightly supper than EC value of 1000 mGy.cm. Personnel training and more awareness on optimization of dosage may still aid to further guide down the dosage of radiation within the location compared to international values. Therefore, centers with fairly lower values than the state derived DRLs (LDRL) should retain their values, while those whose values are higher should implement dose optimization.

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.

Background: There is an increase in pediatric Computed Tomography (CT) imaging with advancement in technology but CT radiation dose produces significant adverse effects. The objective of this experimental phantom study is to develop an age-based low-dose pediatric CT head protocol. Materials and Methods: Polymethyl methacrylate (PMMA) pediatric head mimicking phantom scanning was performed on a CT scanner using various combinations of tube voltage (kV) and product of tube current and exposure time (mAs) setting. Images were reconstructed by iterative reconstruction iDose4 level 1-5. Quantitative assessment of image quality (IQ) was done by calculating Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR), and Image Noise (IN). Radiation dose indices (RDI) were measured by recording Volumetric CT Dose Index (CTDIV) and Dose length product (DLP). Figure of Merit (FOM) was calculated to study overall effects between IQ and RDI. IQ and RDI obtained using different exposure settings were compared. Result: Optimized age-based low-dose protocols were developed based on IQ analysis and RDI. For pediatric CT head, with age less than one year kV and mAs of 80 and 150 and for one–, five years age kV and mAs of 100 and 200 with iDose4 level-3 was found to be optimum low dose protocol. Conclusion: The experimental phantom study concluded that with use of low kVp and mAs, radiation dose was reduced to 62% for less than 1-year age group and 51% for 1-5 year age group and also with use of iterative reconstruction technique iDose4 level-3 diagnostic image quality was maintained.

Background: Approximation of radiation risks in computed tomography (CT) requires knowledge of specific organ doses. A Rando phantom and thermoluminescent dosimeters (TLDs) provide a proxy for in-vivo measurements. In this study, measured chest CT doses were used to calculate dose length product (DLP), a dosimetric needed for estimation of effective dose (E). Method and Materials: Ninety-five calibrated TLDs embedded at peripheral and central positions of Rando phantom chest slice measured chest CT dose during imaging using Phillips Brilliance 64-slice CT scanner. Three measurements were conducted each with new TLDs. Irradiated TLDs were read with a Harshaw TLD reader (Model 3500). One-way ANOVA test verified statistical significance of TLD measurements. TLD doses were used to calculate chest CT dose given as dose length product (DLP), a product of chest slice CT dose measured by volumetric CT dose index (CTDIV) multiplied by scan length. Consequently, E was calculated as the product of DLP and k, an adult chest conversion factor published by International Commission on Radiological Protection Publication 103. Results: Differences in mean TLDs measurements were statistically significant (p=0. 032). The mean chest slice peripheral and center doses were 3. 61 ±,0. 6 and 4. 60 ±,0. 31 mGy respectively. Adult chest CT dose was 178. 8 ±,15 mGy. E was estimated as 2. 5 ±,0. 21 mSv. It is than the range (5. 6 –,9. 3 mSv) found in literature. Conclusion: E relates radiation exposure to stochastic effects. The estimated value (E = 2. 5±, 0. 21 mSv), reveals that chest CT protocol used was optimized.