Automatic Tube Current Modulation Research Articles

Evaluation of overexposure risk when there is a space between the subject and the couch in computed tomography: a phantom study.

The purpose of this study was to investigate the risk of overexposure associated with automatic tube current modulation (ATCM) and automatic couch height positioning compensation mechanism (AHC) in computed tomography (CT) systems, particularly in scenarios involving a gap between the subject and the couch. Results revealed that when AHC was enabled, CT dose index volume (CTDIvol) increased by approximately 10% at 2.5cm, 20% at 5.0cm, and 40% at 10.0cm gaps compared to close contact conditions. While the AHC function ensures consistent exposure doses and image quality regardless of subject positioning relative to the CT gantry isocenter, the study highlights a potential risk of overexposure when a gap exists between the subject and the couch. These findings offer valuable insights for optimizing CT imaging protocols and underscore the importance of carefully considering subject positioning in clinical practice.

The impact of automatic tube current modulation related settings of a modern GE CT scanner on image quality and patient dose; details do matter.

To investigate the operation principles of the automatic tube current modulation (ATCM) of a modern GE healthcare CT scanner, and the impact of related settings on image quality and patient dose. A dedicated phantom (Mercury 4.0) was scanned using two of the most frequently used clinical scanning protocols (chest and abdomen-pelvis). The preset protocol settings were used as starting points (reference conditions). Scan direction, scan mode (helical vs. axial), total beam width, tube potential (kVp), and ATCM settings were then modified individually to understand their impact on radiation dose and image quality. Regarding the ATCM settings, the SmartmA minimum and maximum mA limits, and the noise index (NI) values were varied. As surrogates of patient dose, the CTDIvol and DLP values of each scan were used. As surrogates of image quality were used the image noise and the detectability index (d') of five different materials (air, solid water, polystyrene, iodine, and bone) embedded in the Mercury phantom calculated with the ImQuest software. The scanning direction did not have any effect on ATCM curves, unlike what has been observed in CT scanners from other manufacturers. Total beam width does matter, however, the SmartmA limit settings and kVp selection had the greatest impact on image quality and dose. It was seen that improper minimum mA limit settings practically invalidated the ATCM operation. In contrast, when full modulation was allowed without restrictions, noise standard deviation, and detectability index became much more consistent across the wide range of phantom diameters. For lower kVp settings an impressive dose reduction was observed that requires further investigation. SmartmA is a tool that if not properly used may increase the patient doses considerably. Therefore, its settings should be carefully adjusted for each preset different clinical protocol.

Comparison of dose length product and image quality of a biphasic whole-body polytrauma CT protocol with and without the automatic tube voltage selection.

A significant source of man-made radiation is now linked to medical devices especially X-ray imaging based ones like CT scans which expose the body to cumulative ionizing radiation and thus attendant cancer risks. The aim of this study was to determine whether using a combination of Automatic Tube Current Modulation (ATCM) and Automatic Tube Voltage Selection (ATVS) during two-phase whole-body CT (2PWBCT) examinations would reduce the radiation dose while preserving the image quality. This was a prospective, observational, single-centre study of 127 adult patients who had undergone the 2PWBCT polytraumatic protocol. All were examined on a Somatom Drive scanner (Siemens). The patients were divided into two groups: ATCM only (42 patients) and ATCM +ATVS (85 patients). Patients' arm positions during examination and the examination dose length product (DLP) values were recorded, as well the standard deviations (SD) of the density in reference areas on CT scans for the image quality assessment. The DLP values and image quality in the groups were compared using ANOVA. Mean Total DLP (in mGy*cm): ATCM only: 3337 +/-797, ATCM+ATVS: 3402 +/-830; P=0.674. No effect of arm position (P=0.586). Mean density SD values in reference areas (in HU) in ATCM only: 49 +/-45, 15 +/-6, 9 +/-2, 12 +/-4, 10 +/-3, in ATCM+ATVS: 48 +/-45, 17 +/-6, 11 +/-3, 15 +/-6, 12 +/-4. SD values was higher in ATCM+ATVS group (P<0.001). Combination of ATVS and ATCM in polytraumatic 2PWBCT leads to no significant radiation load reduction compared with ATCM only but does lead to a slight degradation of image quality. The radiation load is significantly reduced if the patient has their arms behind the head when scanning, regardless of the activation of ATVS.

Dual-energy computed tomography quality control: Initial experiences with a semi-automatic analysis tool

PurposeA quality control (QC) system for dual-energy CT (DECT) was developed. The scope of the QC system was to monitor both the constancy of the CT images and the software used in calculating the DECT derived maps. Longitudinal analysis was based on a standard imaging protocol, a commercial multi-energy phantom, and a semi-automatic analysis tool. MethodsThe phantom consisted of an elliptical body section with round slots for interchangeable inserts. It was scanned with 90kVp/Sn150kVp, automatic tube current modulation, and 9.6 mGy CTDIvol. From the two conventional CT images, scanner manufacturer’s software was used to provide virtual monoenergetic images at two different energies, effective atomic number (Zeff) maps, and iodine concentration maps. The images were analyzed using an open-source tool allowing user-selected statistics of interest. The means and standard deviations of the phantom background and the iodine, calcium, and water inserts were recorded. The QC tool is available at github.com/tomakela/dectqatool. ResultsThe obtained results were generally highly consistent over time, except for the smaller diameter iodine inserts. A small change inZeff was observed after a DECT software update. The developed QC tool aided the analysis robustness: the segmentations were modifiable when needed, and small rotations or air bubbles in the water insert were easily corrected. ConclusionThe developed QC system provided easy-to-use workflow for constancy measurements. A small deviation due to change in the post-processing was detected. The proposed imaging protocol and analysis steps, and the reported measurement variations can aid in determining action levels for DECT QC.

Radiation exposure and cancer risk of pediatric head CT scans: Impact of age and scanning parameters

Computed tomography (CT) is a widely utilized imaging technique in various medical applications due to the advanced technology that allows the diagnosis of diseases efficiently. The aims of this study were (1) to assess the radiation dose and the probability of cancer incidence for pediatric head CT scans, and (2) to analyze the influence of age and other scanning parameters on radiation dose. A total of 224 pediatric patients, ranging in age from newborn to 18 years, were collected from three main hospitals in Saudi Arabia. The patient data were divided into four age groups: Group 1 (0 to < 1 year old), Group 2 (1 to < 5 years old), Group 3 (5 to < 10 years old), and Group 4 (10 to < 18 years old). Initially, descriptive statistics were conducted for the values of volume CT dose index (CTDIvol), dose-length product (DLP), effective dose, and probability of lifetime cancer risk. This was followed by applying the Kruskal-Wallis H and the Mann-Whitney U tests to investigate the influence of age and other scanning parameters, namely tube voltage, slice thickness, and the use of automatic tube current modulation (ATCM), on radiation dose. It has been found that as the age of patients increased, there was a corresponding increase in CTDIvol and DLP values and a decrease in effective doses and lifetime cancer risk. The patient's age accounted for 33.4% and 34.9% of the variations in CTDIvol and DLP, respectively, while tube voltage (kVp) settings accounted for 25.8% and 24.9%, respectively. There was an increase of 22.3% in CTDIvol reported for patients scanned with a slice thickness of 2 mm compared to those scanned at 2.5 mm, and a 2.2% dose increase between slice thicknesses of 2.5 mm and 5 mm. Radiation doses in the surveyed hospitals fall within acceptable limits. Further studies in Saudi Arabia should focus on evaluating patient doses based on the actual sizes, which determine radiation doses for pediatric CT imaging more accurately.

Evaluation of Changes in Dose Estimation on Abdomen CT Scan with Automatic Tube Current Modulation Using In-House Phantom

This study evaluates the effect of the Automatic Tube Current Modulation (ATCM) technique on pitch and effective diameter variation in estimating dose values and noise levels for abdominal examination on Philips Ingenuity CT scan machine using in-house Phantoms. The in-house phantoms are oval in shape with three effective diameter sizes, namely 23.2 cm, 28.3 cm, and 33.3 cm to represent abdominal region. The three size Phantoms were scanned using an Ingenuity 128 Philips CT scan with the abdominal protocol exposure parameters of 120 kVp tube voltage, Dose Right Index (DRI) variations of 10,11,12,13, and 14, and pitch variations of 0.6; 0.8; 1.0; 1.2; and 1.49. The changes in mAs, CTDIvol, and noise to the Philips reference value were then verified (i.e. an addition of one DRI value increases mAs by 12 %). For evaluation, a metric to express the change in DRI is defined as ΔDRI. The study demonstrates that noise level is influenced by object size; size information of the object could be useful to predict the change of tube current and pitch due to ATCM with respect to selected DRI. The DRI value is proportional to the tube current, thus selecting the DRI at a certain pitch will directly determine tube current. The ΔDRI in general, according to Philips specifications, is verified to be approximately 10 % to 13 %, except for DRI 10 to 11 which is relatively high on average 15 % to 17 %. Increasing DRI increases the CTDIvol. The CTDI/mAs constantly ranges of 0.06 to 0.07. The value could serve as a characteristic parameter for quality assurance. The ATCM specifications of the Ingenuity 128 CT Scanner is according to Philips regulations.

Influence of Body Mass Index and Abdominal Circumference on Radiation Dose During Abdominopelvic Computed Tomography

Background: Contrast-enhanced examinations of the abdomen region have a greater radiation exposure due to the multiphase abdominal computed tomography (CT) protocols. The use of automatic tube current modulation is known to reduce radiation dose and maintain or improve image quality for abdominal CT. However, using automatic tube current modulation can increase radiation dose for individuals with a larger body habitus. Objectives: The study aimed to assess the influence of body mass index and abdominal circumference on the effective dose for routinely performed contrast-enhanced abdomen and pelvis scans. Methods: A total of 160 subjects referred for routine CT abdomen and pelvis were included in the study and categorised into three groups according to their body mass index (BMI) [underweight: &lt;18.5 kg/m2, normal: 18.5-24.9 kg/m2, overweight: 25-29.9 kg/m2 and obese: (≥30 kg/m2]. All the scans were performed on a 128 MDCT scanner by Philips. The effective dose was calculated from the dose length product using region-specific conversion factors. Results: The effective dose was found to be 21.47 ± 2 mSv for the underweight group, 22.75± 2.3 mSv for the normal group, 25.02 ± 2.8 for the overweight group, and 29.7 ± 6.7 mSv for the obese group. Conclusion: The study reported a 32.39 % increase in effective dose for obese patients. The study also reported a significant increase in effective dose as BMI and abdominal circumference increased.

Diagnostic Validity Of Low Dose CT KUB In Demonstration Of Genitourinary Tract Calculi Compared To Normal Dose Ct Kub: A Provisional Study

Objective: Renal colic is a common clinical condition. Our objective is to evaluate the diagnostic accuracy of low dose CT KUB for detection of urinary stones, to minimize radiation dose to the patients, and to analyze diagnostic accuracy of LDCT KUB in comparison to standard dose CT KUB. We speculate the LDCT KUB may reduce patient radiation dose while maintaining diagnostic value.&#x0D; Materials and Methods: This comparative cross sectional validation study was conducted at Department of Radiology in Benazir Bhutto Hospital, Rawalpindi June 2021 to Feb 2022. After approval of hospital ethical committee, a sample of 49 kidneys of 31 patients was collected by non-probability consecutive sampling technique. Included were the patients diagnosed with renal calculi referred from other departments. All the included patients were scanned by Toshiba Aquilion 16 slices, using automated tube current modulation, without any oral or IV contrast. CT scan started from diaphragm down to pubic symphysis with standard dose CT (SDCT) followed by low dose CT (LDCT). After the data was recorded, statistical package for social sciences, version 20.0 (SPSS Inc., Chicago, Illinois, USA) was used to analyse the data and generate results. Mean + standard deviation was calculated for qualitative data while frequency and percentage for qualitative variables. The means were compared by independent sample t test while the agreement between standard and low dose was depicted by kappa value.&#x0D; Results: A total of 49 kidneys of 31 patients with renal stones was included in this study. The mean age of the patients ranged from 27 years to 48 years with a mean of 36.42 + 9.97 year. In gender distribution, 75.5 % (37) were male while 24.5 % (12) were females. More than half 59 % (29) were right while 41 % (20) were left kidneys.&#x0D; Conclusion: This study demonstrated that LDCT was a productive and effective technique in the detection of urothelial stones despite considerable reduction in radiation dose and exposure as seen in SDCT.

“Triple-low” radiation dose bronchial artery CT angiography before bronchial artery embolisation: a feasibility study

To explore the feasibility of a "triple-low" dose (low tube voltage, low tube current, and low contrast agent volume) bronchial artery computed tomography (CT) angiography (CTA) to replace routine dose bronchial artery CTA before bronchial artery embolisation (BAE). CTA was obtained from 60 patients with body mass index (BMI)<30 kg/m2 using a 256 multi-section iCT system, and they were divided into two groups: (1) group A: 100 kVp, 100 mAs, 50 ml contrast medium (CM); (2) group B: 120 kVp, automatic tube current modulation (ACTM), 80 ml CM. CT attenuation of the thoracic aorta, image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated, and subjective image quality scores and traceability scores assessed. The effective radiation dose was calculated. The radiation dose was reduced by 79.7% in group A compared to group B (p<0.05). The CT attenuation of the thoracic aorta was increased by approximately 13% in group A compared to group B (p<0.05). Higher image noise, lower SNR, and CNR were obtained in group A compared to group B (all p<0.05). Both subjective image quality scores and traceability scores did not differ between groups A and B (both p>0.05). It is feasible to use the "triple-low" dose CTA protocol for patients with a body mass index (BMI)<30 kg/m2. The radiation dose was reduced by 79.7%, and the dose of contrast medium was reduced by 37.5% to ensure the diagnostic value.

Pathology-based radiation dose in computed tomography: investigation of the effect of lung lesions on water-equivalent diameter, CTDIVol and SSDE in COVID-19 patients.

Lung lesions can increase the CT number and affect the water-equivalent diameter (Dw), Dw-based conversion factor (CFw), and Dw-based size-specific dose estimate (SSDEw). We evaluated the effect of COVID-19 lesions and total severity score (TSS) on radiation doseconsidering the effect of automatic tube current modulation (ATCM) and fixed tube current (FTC). A total of 186 chest CT scans were categorised into five TSS groups, including healthy, minimal, mild, moderate and severe. The effective diameter (Deff), Dw, CFw, Deff-based conversion factor (CFeff), volume computed tomography dose index (CTDIVol), pathological dose impact factor (PDIF) 1 and SSDEw were calculated. TSS was correlated with Dw (r=0.29, p-value=0.001), CTDIVol (ATCM) (r=0.23, p=0.001) and PDIF (r=- 0.51, p-value=0.001). $\overline{{\mathrm{SSDE}}_{\mathrm{w}}}$ (FTC) was significantly different among all groups. $\overline{{\mathrm{SSDE}}_{\mathrm{w}}}$ (ATCM) was greater for moderate (13%) and mild (14%) groups. Increasing TSS increase the Dw and causes a decrease in CFw and $\overline{{\mathrm{SSDE}}_{\mathrm{w}}}$ (FTC), and can increase $\overline{{\mathrm{SSDE}}_{\mathrm{w}}}$ (ATCM) in some Dw ranges.

Size based dependence of patient dose metrics, and image quality metrics for clinical indicator-based imaging protocols in abdominal CT procedures

IntroductionDiagnostic reference level (DRL) values for computed tomography (CT) based on clinical indication are warranted since imaging protocols are indication-dependent. This study proposes clinical DRL values using the CT dose metrics and five patient size-related parameters while considering image quality. MethodsThe volumetric CT dose index (CTDIvol), dose-length product (DLP) and five size-related parameters of size-specific dose estimates (SSDE), namely the anterior-posterior (AP) dimension, lateral (LAT) dimension, sum dimension, effective diameter, and the body mass index (BMI), were used to calculate DRL values for CT chest-abdomen-pelvis (CAP) and abdomen-pelvis (AbP) protocols. DRL values of the clinical indications for cancer, urinary system stones and other pathologies were assessed based on the BMI classifications using the median and 75th percentile. An image subtraction algorithm was used to assess the image quality metrics (IQM) of the CT images. ResultsThe 75th percentile for SSDEAP dimension for CAP cancer was 19.7, 14.9 and 12.7 mGy at Hospitals A, C and E, respectively. The median DLP for other AbP pathologies was 556.3, 1452.0 and 1960.7 mGy.cm for normal weight, overweight and obese patients, respectively, at Hospital A. The image quality varied among BMI classifications for different clinically indicated examinations. Although the dose increased with BMI, the image quality index was consistent because automatic tube current modulation (ATCM) was used. ConclusionDRL values are influenced by patient size-related parameters and the clinical indication protocols, while the image quality index is independent of the BMI. Implications for practiceSize-related clinical DRL values and image quality index can be used to monitor and optimise dose and image quality. Acquisition parameters and image quality indexes should be investigated and adjusted when unusually high DRL values are noted.

The effect of contact radiation shielding on breast dose during CT abdomen-pelvis: a phantom study.

This study aims to investigate if contact shielding reduces breast radiation dose during computed tomography (CT) abdomen-pelvis examinations using automatic tube current modulation to protect one of the four most radiosensitive organs during CT examinations. Dose measurements were taken with and without contact shielding across the anterior and lateral aspects of the breasts and with and without organ dose modulation (ODM) to quantify achievable dose reductions. Although there are no statistically significant findings, when comparing with and without shielding, the mean breast surface dose was reduced by 0.01μSv without ODM (1.92-1.91μSv, p=0.49) and increased by 0.03μSv with ODM (1.53-1.56μSv, p=0.44). Comparing with and without ODM, the mean breast surface dose was reduced by 0.35μSv with shielding (1.91-1.56μSv, p=0.24) and by 0.39μSv without shielding (1.92-1.53μSv, p=0.17). The addition of contact shielding does not provide significant breast surface radiation dose reduction during CT abdomen-pelvis.

Development of phantom for current modulation quality assurance test on computed tomography.

Automatic tube current modulation (ATCM) in computed tomography (CT) is a powerful tool for reducing the dose delivery to the patient during the scan. A phantom is used to perform the ATCM quality control (QC) test, assessing how the CT system adapts the tube current as a function of object size. Considering quality assurance recommendations (Brazilian and international), we developed a dedicated phantom for the ATCM test. The phantom was built-in high-density polyethylene in a cylindric shape with three different sizes. To verify the applicability of this phantom, we tested it in two different CT scanners (Toshiba and Philips). The results demonstrated concordance between a discrete change in phantom size, and the corresponding change in the tube current, indicating that the CT system could adapt current when a discrete attenuation shift occurred. The developed phantom might be used in ATCM QC tests.

A Study of Fixed Current and Automatic Tube Current Modulation at a Fixed Low Tube Voltage in Low-dose Computed Tomography (CT) Imaging of Infant Lungs

Background: With the development of computed tomography (CT) technology, the number of infants undergoing CT examination has increased. Recently, problems associated with radiation exposure have attracted the public attention, and low-dose CT examination has become the research focus. Objectives: This study aimed to explore the feasibility of a fixed ultralow tube current combined with iDose4 iterative reconstruction at a low tube voltage (80 kV) in low-dose CT scanning of infant lungs. Patients and Methods: Ninety infants, aged 0 - 3 years, undergoing enhanced chest CT scan (including plain CT scan and arterial scan), were included in the experimental group. In the experimental group, plain CT scan was performed at 80 kV under a fixed tube current (30 mA), and arterial phase CT scan was carried out at 80 kV with automatic tube current modulation (30 - 150 mA). Meanwhile, 90 infants, aged 0 - 3 years, undergoing non-enhanced chest CT scan, were randomly recruited as the control group. For the control group, plain CT scan was performed at 80 kV with automatic tube current modulation (30-150 mA). In each examination, the iDose4 iterative reconstruction technique was used for reconstruction. The volume CT dose index (CTDIvol), dose-length product (DLP), effective dose (ED, measured using a 32-cm diameter phantom), signal-to-noise ratio (SNR), and overall subjective quality of plain CT scans were analyzed and compared between the experimental and control groups. Results: Regarding the radiation dose in different age groups, the ED (mSv) was significantly lower in the experimental group compared to the control group (0-1-year-old subgroup: 0.48 ± 0.05 mSv in the experimental group vs. 0.91 ± 0.19 mSv in the control group, P &lt; 0.05; 1-2-year-old subgroup: 0.50 ± 0.01 mSv in the experimental group vs. 0.75 ± 0.10 mSv in the control group, P &lt; 0.05; and 2-3-year-old subgroup: 0.46 ± 0.05 mSv in the experimental group vs. 0.79 ± 0.11 mSv in the control group, P &lt; 0.05). The image SNR was higher in the control group compared to the experimental group (P &lt; 0.05), while the difference in subjective image quality was not significant between the experimental and control groups (P &lt; 0.05). Conclusion: The chest CT examination of infants, aged 0 - 3 years, at a low tube voltage (80 kV) and a fixed tube current (30 mA), combined with the iDose4 iterative reconstruction technique, and the obtained images met the diagnostic criteria...

Impact of the automatic tube current modulation (ATCM) system on virtual monoenergetic image quality for dual-source CT: A phantom study

PurposeTo assess the impact of the automatic tube current modulation (ATCM) on virtual monoenergetic images (VMIs) quality in dual-source CT(DSCT). Materials and methodsAcquisitions were performed on DSCT using the Mercury phantom. The acquisition parameters for an abdomen-pelvic examination with single-energy CT(SECT) and dual-energy CT(DECT) imaging were used. Acquisitions were performed for each imaging mode using fixed mAs and ATCM. The mAs value was set to obtain a volume CT dose index of 11 mGy in fixed mAs acquisitions. This value was used as the reference mAs in ATCM acquisitions. The noise power spectrum and task-based transfer function at 40,50,60 and 70 keV levels were computed on VMIs and SECT images. The detectability index (d′) was calculated for a lesion with an iodine concentration of 10 mg/mL. ResultsThe noise magnitude on VMIs was higher with the ATCM system than with fixed mAs for all energy levels and section diameters of 21,26 and 31 cm. The noise texture and spatial resolution were similar between the fixed mAs and ATCM acquisitions for both imaging modes. The d’ values were lower for all energy levels with ATCM than with fixed mAs acquisitions for 21 and 26 cm diameters by −39.82 ± 9.32%, similar at 31 cm diameter −4.13 ± 0.24% and higher at 36 cm diameter 10.40 ± 6.69%. It was higher on VMIs at all energy levels compared to SECT images. ConclusionsThe ATCM system could be used with DECT imaging to optimize patient exposure without changing the noise texture and spatial resolution of VMIs compared to fixed mAs and SECT.

Effect of patient characteristics on vessel enhancement on arterio-venous fistula CT angiography in a retrospective cohort study.

To evaluate the effects of various patient characteristics on vessel enhancement on arterio-venous fistula (AVF) computed tomography (CT) angiography (AVF-CT angiography). A total of 127 patients with suspected or confirmed shunt stenosis and internal AVF complications were considered for inclusion in a retrospective cohort study. The tube voltage was 120 kVp, and the tube current was changed from 300 to 770 mA to maintain the image quality (noise index: 14) using automatic tube current modulation. To evaluate the effects of age, sex, body size, and scan delay on the CT number of the brachial artery or vein, we used correlation coefficients and multivariate regression analyses. There was a significant positive correlation between the CT number of the brachial artery or vein and age (R = 0.21 or 0.23, P < .01). The correlations were inverse with the height (r = -0.45 or -0.42), total body weight (r = -0.52 or -0.50), body mass index (r = -0.21 or -0.23), body surface area (body surface area [BSA]; r = -0.56 or -0.54), and lean body weight (r = -0.55 or -0.53) in linear regression analysis (P < .01 for all). There was a significant correlation between the CT number of the brachial artery or vein and scan delay (R = 0.19 or 01.9, P < .01). Only the BSA had significant effects on the CT number in multivariate regression analysis (P < .01). The BSA was significantly correlated with the CT number of the brachial artery or vein on AVF-CT angiography.

Comparison of image quality and radiation dose of different scanning methods used for computed tomography of the unilateral shoulder.

The effect of different computed tomography (CT) scanning methods of the shoulder on image quality is uncertain. To compare the effect of different methods of CT scanning of the right shoulder on image quality and radiation dose. A total of 30 adults were divided into five groups. Group A received scans centered on the body's long axis, a scout direction of 0° + 90°, and automatic tube current modulation (ATCM). The other four groups (B, C, D, E) received isocenter scans centered on the shoulder with different scout directions (B and C: 0° + 90°, D: 0°, E: 0° + 270°) and tube currents (B: 420 mA; C, D, E: ATCM). The volume CT dose index (CTDIvol), dose-length product (DLP), image objective noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were compared. Three subjective measures were also compared (noise, stripe artifacts, diagnostic confidence). The five groups differed significantly in all subjective and objective indexes. The CTDIvol and DLP decreased in the order of groups C, A, B, E, and D; the differences between groups A and B were not significant (P > 0.05). Groups B, C, and E had better SNR and CNR than groups A and D (P < 0.01). Subjective evaluations indicated group D was worse than groups B, C, and E (P < 0.05). In the ATCM system that uses the last scout view, CT of the shoulder should use isocenter scanning with the lateral scout view when the tube is away from the long axis of the body as the last execution direction.

Patient dose reduction for a localizer radiograph with an additional tin filter in chest-abdomen-pelvis, spine, and head computed tomography examinations.

This study aimed to evaluate the dose reduction potential of adding a tin filter to localizer radiographs (LR) on computed tomography (CT) examinations in both phantom and clinical studies. LRs were performed using combinations of 120 kVp and 20mA (120/20), 100 kVp with a tin filter, and 50mA or 20mA (Sn100/50, Sn100/20). For the phantom experiment, entrance surface doses (ESD) of the LRs were evaluated for each protocol using an anthropomorphic phantom. This retrospective clinical study included 700 patients (300 for chest-pelvis, 200 for spine, and 200 for head CTs). The volume CT dose indices (CTDIvols) of the main CT scans were recorded and placed into one of three groups based on body mass index (BMI): underweight, normal-weight, and overweight, to evaluate the effect of LR acquisition conditions on the performance of the automatic tube current modulation technique of subsequent CT scans. The ESDs of all LRs with the Sn100/50 protocol were 0.03mGy, a decrease of more than 80% compared to those of the 120/20 protocol. Moreover, the Sn100/20 protocol reduced ESD to 0.02mGy. In chest-pelvis CT, there were no significant differences in the CTDIvol between with and without a tin filter for each BMI group. However, the lateral LRs with the tin filter on the spine CT slightly reduced the CTDIvol in normal-weight and overweight patients. Although there is room to optimize the acquisition conditions for larger patients, an additional tin filter for LR is a useful means to efficiently reduce ESDs.

Patient dose increase caused by posteroanterior CT localizer radiographs

IntroductionThe aim of this study was to compare the output dose (volume CT dose index [ CTDIvol], and dose length product [DLP]) of automatic tube current modulation (ATCM) determined by localizer radiographs obtained in the anteroposterior (AP) and posteroanterior (PA) directions. MethodsOne hundred and twenty-four patients who underwent upper abdomen and/or chest–to–pelvis computed tomography (CT) were included. Patients underwent two series of CT examinations, and localizer radiographs were obtained in the AP and PA directions. The horizontal diameter of the localizer radiograph, scan length, CTDIvol, and DLP were measured. ResultsThere was no significant difference in the scan length; however, all the other values were significantly higher in the PA direction. The mean horizontal diameter was 33.1 ± 2.6 cm and 35.4 ± 2.9 cm in the AP and PA directions of the localizer radiographs, respectively. The CTDIvol and DLP in the PA direction increased by approximately 7–8%.Bland-Altman plots between AP and PA localizer directions in upper abdominal CT showed a positive bias of 1.1 mGy and 30.0 mGy cm for CTDIvol and DLP, respectively. Correspondingly, chest–to–pelvic CT showed a positive bias of 0.93 mGy and 69.3 mGy cm for CTDIvol and DLP, respectively. ConclusionThe output dose of ATCM determined by localizer radiographs obtained in the PA direction was increased compared to the AP direction. Localizer radiographs obtained in the AP direction should be preferred for optimizing the output dose using ATCM. Implications for practiceBased on the evidence of this study, localizer radiographs obtained in the AP direction should be preferred for optimizing the output dose in CT examinations.

Assessment of the knowledge level of radiographers and CT technologists regarding computed tomography parameters in Iran

ObjectiveTo evaluate the knowledge of CT technologists and radiographers concerning CT parameters, in order to keep CT users be aware of all CT parameters and their impact on image quality and patient dose while keeping their knowledge up to date. MethodsThis cross-sectional descriptive-analytic study was conducted in Zanjan province, Iran, using a valid and reliable online questionnaire with 53 questions distributed to 153 radiology personnel. Each questionnaire included questions about demographic characteristics and CT parameters, including kVp, mAs, image noise, slice thickness, pitch and automatic tube current modulation (ATCM), and the effects of these parameters on image quality and radiation dose. ResultsA response rate of 61.0% (94/153) was achieved. This study enrolled 30 radiographers and 64 CT technologists. There was no significant difference in the mean scores of the two groups (52.16 ± 9.90 vs. 56.09 ± 12.00, t ​= ​−1.545, P ​= ​0.126). CT personnel had the highest and lowest knowledge scores in image reconstruction (t ​= ​−28.33, P ​= ​0.001) and mAs (t ​= ​4.27, P ​= ​0.590), respectively, whereas radiographers had the highest and lowest knowledge scores in the fields of image noise (t ​= ​9.85, P ​= ​0.015) and kVp (t ​= ​−12.73, P ​= ​0.007), respectively. ConclusionsThe total knowledge scores of CT technologists and radiographers for various scan parameters affecting image quality and dose were insufficient. Thus, it is recommended that regular retraining courses be held to enhance and update technologists’ knowledge.