A comparison of fixed tube current (FTC) and automatic tube current modulation (ATCM) CT methods for abdominal scanning : implications on radiation dose and image quality

PURPOSE: There has been a huge increase in the use of abdominal CT scanning in recent years. This has contributed to an increase in radiation dose administered to patients. Abdominal CT scans generally require higher exposure factors when compared to other anatomical regions. This drives a need for urgent optimisation of the radiation dose and image quality for abdominal CT examinations. The aim of this thesis is to evaluate Fixed Tube Current (FTC) and Automatic Tube Current Modulation (ATCM) on image quality and radiation dose during abdominal CT examinations across a range of scanning parameters. MATERIALS AND METHODS: Using a Toshiba Aquilion 16 CT scanner (120 kVp, 0.5 seconds tube rotation), an adult ATOM dosimetry and abdominal anthropomorphic phantom were exposed to a series of FTC and ATCM CT protocols with variations in tube current as follows: FTC - 100, 200, 250, 300 and 400mA; ATCM - low dose+, low dose, standard, quality and high quality. The pitch factors evaluated included were 0.688, 0.938 & 1.438 and the detector configurations included were 0.5×16 mm, 1.0×16 mm and 2.0×16 mm. Radiation doses for nine abdominal organs were directly measured using the Metal Oxide Semiconductor Field Effect Transistors (MOSFET). Effective dose (ED) was measured and estimation comprised of three methods: mathematical modelling with k-factors and dose length product DLP, direct with MOSFET and indirectly with Monte Carlo simulation (ImPACT). Effective risk (ER) was estimated using MOSFET data and Brenner’s equations / BEIR VII 2006 report. The raw data for ATCM radiation dose was corrected using an equivalence equation. The ATCM corrected and uncorrected data were compared against FTC. Image quality was assessed using SNR (five abdominal organs) and a relative visual grading analysis (VGA) method (five different axial images). Image quality evaluation was performed by the researcher after testing agreement between against five different observers. RESULTS: There were no significant differences in the mean radiation doses between FTC and corrected ATCM across a range of acquisition protocols (P>0.05). This was with the exception of the 300mA/quality protocols, and for a fast pitch factor with 0.5×16mm detector configurations. These had significantly lower doses for FTC (P<0.05). These differences were up to 13% for the mean abdominal organ doses, effective doses and the effective risk. In addition, for all acquisition parameters, the mean radiation dose was significantly higher (P<0.05; 17%-23%) for uncorrected ATCM when compared to FTC. In terms of image quality, there were no differences in SNR values between FTC and ATCM for the majority of acquisition protocols, excepting the higher mean SNR value (P<0.05) for the FTC at 100mA/low dose + and 200 mA/ low dose (pancreas, left and right kidneys). Conversely, the mean SNR values were significantly higher (P<0.05) for the ATCM scans for 300mA/quality and fast pitch factor (1.438) (liver, spleen and pancreas) than FTC. Finally, relative VGA scores for both FTC and ATCM demonstrated no significant difference, except for ‘quality’ ATCM scans (image # 1, image # 2) and a fast pitch factor (1.438) for image #2 and #3. CONCLUSION: FTC and corrected ATCM were generally similar in terms of radiation dose and image quality except for some acquisition parameters; 300mA/quality tube current and fast (1.483) pitch factor FTC was lower than the corrected ATCM. However, the uncorrected ATCM produced higher radiation dose when compared with FTC techniques. In addition, FTC and ATCM generally produced similar SNR, again with the exception of some protocols. The SNR was higher for FTC than ATCM at lower tube current (pancreas, left and right kidneys), at 300mA/quality and fast pitch factor (1.438) SNR values for ATCM higher than FTC (liver and spleen). However, the ATCM technique is able to produce higher mean relative VGA scores for upper and middle abdominal organs. Further investigation of image quality and radiation dose difference between FTC and ATCM is required

Impact of gonad shielding for AP pelvis on dose and image quality on different female sizes : a phantom study

Introduction In clinical practice AP pelvis standard protocols are suitable for average size patients. However, as the average body size has increased over the past decades, radiographers have had to improve their practice in order to ensure that adequate image quality with minimal radiation dose to the patient is achieved. Gonad shielding has been found to be an effective way to reduce the radiation dose to the ovaries. However, the effect of increased body size, or fat thickness, in combination with gonad shielding is unclear. The goal of the study was to investigate the impact of gonad shielding in a phantom of adult female stature with increasing fat thicknesses on SNR (as a measure for image quality) and dose for AP pelvis examination. Methods An adult Alderson female pelvis phantom was imaged with a variety of fat thickness categories as a representation of increasing BMI. 72 images were acquired using both AEC and manual exposure with and without gonad shielding. The radiation dose to the ovaries was measured using a MOSFET system. The relationship between fat thickness, SNR and dose when the AP pelvis was performed with and without shielding was investigated using the Wilcoxon signed rank test. P-values < 0.05 were considered to be statistically significant. Results Ovary dose and SNR remained constant despite the use of gonad shielding while introducing fat layers. Conclusion The ovary dose did not increase with an increase of fat thickness and the image quality was not altered. Implications for practice Based on this phantom study it can be suggested that obese patients can expect the same image quality as average patients while respecting ALARA principle when using adequate protocols

A Cross-Sectional Evaluation of Knowledge About Breast Cancer and Perceived Barriers to the Uptake of Mammogram Screening Among Northern Saudi Women: A Population-Based Study

Muhannad Faleh Alanazi,1 Ashokkumar Thirunavukkarasu,2 Maily Alrowily,3 Nouf Alaqel,4 Abdulelah Alaqel,5 Mutlaq Alruwaili,5 Nouf Nashmi M Alazmi,5 Osamah Alhassan,5 Mona Fahad M Aljarallah,5 Afrah Mohaimeed Altaymani5 1Division of Radiology, Department of Internal Medicine, College of Medicine, Jouf University, Sakaka, Saudi Arabia; 2Department of Community and Family Medicine, College of Medicine, Jouf University, Sakaka, Saudi Arabia; 3Aljouf Health Cluster, Ministry of Health, Sakaka, Aljouf, Saudi Arabia; 4Department of Diagnostic Radiology, Prince Mutab Bin Abdulaziz Hospital, Sakaka, Aljouf, Saudi Arabia; 5College of Medicine, Jouf University, Sakaka, Aljouf, Saudi ArabiaCorrespondence: Muhannad Faleh Alanazi, Division of Radiology, Department of Internal Medicine, College of Medicine, Jouf University, Sakaka, 72388, Saudi Arabia, Tel +966555 393 871, Email [email protected]: Mammogram screening (MS) is the gold-standard method for early detection of breast cancer (BC), and its use has been proven to minimize BC-related deaths and reduce treatment costs. However, recent epidemiological surveys have reported that rates of mammogram uptake by the Saudi female population are low. Here, we assessed the knowledge of BC and perceived barriers to MS uptake among pre-eligible northern Saudi women.Participants and Methods: We administered a standard and validated Arabic questionnaire to 400 women aged 40– 69 years. SPSS version 21.0 (IBM Corporation, Armonk, NY, USA) was used for data analysis. We applied logistic regression analysis to find the factors associated with participants’ knowledge of BC and MS. Spearman correlation test was applied to find the correlation between knowledge and barrier scores.Results: The study participants reported that smoking habits (61.3%) and unhealthy food habits (57.8%) were the most common risk factors for BC. Of the studied participants, 56.3% had low or medium degrees of knowledge about BC risk factors and MS. The degree of knowledge was significantly associated with education level (adjusted odds ratio [aOR], 2.35; 95% confidence interval [CI]. = 1.61– 3.13; P = 0.008) and a family history of BC (aOR, 3.66; 95% CI, 1.94– 5.49; P < 0.001). Fear of a BC diagnosis (50.8%) and concerns regarding test procedures were the most common barriers to MS uptake. We also found a negative correlation between participants’ knowledge and perceived barriers to MS (rho = − 0.389, P < 0.001).Conclusion: We recommend that concerned authorities offer women multiple health education sessions covering BC risk factors and the necessity for pre-eligible women to undergo MS spaced at regular intervals at different facilities. Furthermore, a multicentric mixed-methods survey is warranted to find the qualitative aspects of barriers to MS.Keywords: breast cancer, screening, risk factors, mammogram, knowledg