Dose Reduction Potential in Pediatric Chest CT: Comparative Analysis of Tube Voltage and Patient Protocol Presets Using a Custom Pediatric Chest Phantom

Radiation dose for common pediatric computed tomography examinations and evaluation of clinical image quality in pediatric chest CT scans.

With the rapid development of computed tomography (CT) technology, the widespread use of CT examinations in the evaluation of chest diseases in pediatrics has raised extensive concerns about radiation issues. This review first systematically summarizes the factors influencing radiation dose (detector, tube voltage, tube current-time product, field of view, and reconstruction algorithms) in pediatric chest computed tomography examinations. Methods to reduce radiation dose are also discussed, including the utilization of filters, automatic tube current modulation, automatic tube voltage selection, and organ dose modulation. Finally, the methods for individualized radiation dose calculation in pediatric chest CT examinations: effective dose, CT dosimetry software, Size-Specific Dose Estimate, and the Monte Carlo method are reviewed. Radiation exposure reduction is a multifaceted issue. This review aims to provide an optimal scanning scheme for pediatric chest CT from different perspectives.

Computed tomography (CT) has considerable impact in patient care. However, it is the most irradiating medical imaging technique in diagnostic radiology department. Optimization of pediatric CT is not well-practiced in developing countries. Protocols for some age groups were missed, and scan parameters are not adapted to the patient body size and age group. Furthermore, there are no established diagnostic reference levels to enhance dose optimization for pediatric patients at the local, regional, and national levels. Therefore, this study aimed to assess the optimization of routine pediatric CT examinations in Hawassa city, Ethiopia. A total of 360 pediatric dose records were reviewed for routine pediatric CT performed between January 1st, 2021 - May 30th, 2022. The data were analyzed using the statistical package for social science version 25 software. The Local Diagnostic Reference Levels (LDRLs) were established at the 75th percentile of CT dose quantities. The average KVp, mAs, and scan length used for pediatric head, chest, and abdomen CT were (112.8, 260.6, and 19.8), (112.9, 64.7, and 31.5), and (113.3, 79.4, and 32.9) respectively. The range of the established LDRLs in terms of volumetric CT dose index for the head, chest, and abdomen CT were (31.5 to 47, 2.3 to 6.1, 1.7 to 4.7) mGy. Whereas the range in terms of dose length product per scan for the head, chest, and abdomen CT were (723.4 to 1126.7, 55.9 to 258.9, and 38.1 to 242.5) mGy cm respectively. The obtained results show that the LDRLs for volumetric CT does index for head and chest CT were equivalent to the international studies. Whereas the local DRLs in terms of dose length product per scan were higher than the reports other studies except in Japan where the values for chest CT were comparable to the results of this study. Finally, the findings suggested that non-optimized pediatric head and chest CT were performed across all age groups.

Introduction: The importance of estimating patient-sized adjusted radiation dose for pediatric computed tomography (CT) has long been accepted. High doses of ionizing radiation to children are often common in chest CT examinations, as the volume CT dose index (CTDIvol) is measured by a 32 cm phantom. Our study aimed to evaluate the effectiveness of size-specific dose estimate (SSDE) to compensate for the underestimated pediatric absorbed dose. Material and Methods: CTDIvol and dose-length product (DLP) of 320 pediatric chest CT (<1, 1-5, 5-10, 10-15 years) were obtained from Picture-Archiving and Communication System (PACS) in a hospital affiliated with the Shiraz University of Medical Sciences. CTDIvol was converted to SSDE based on the patient's effective diameter. The Statistical Package for Social Science (SPSS) was used for data analysis. Results: The variations between standard phantom (32cm) and the patients' mean effective diameter were approximately 65, 57, 47, and 38, across <1, 1-5, 5-10, 10-15 year age groups, respectively. The mean of SSDE for each age group was significantly higher than the corresponding CTDIvol values. Also, mean CTDIvol and SSDE values differed between age groups significantly (p<0.001). Results showed a strong correlation between age and the two-dose indicators, CTDIvol (0.361) and SSDE (0.184), with p<0.05. Conclusion: Pediatrics receive radiation doses comparable to the dose for adult-sized patients in chest CT protocol if the dosimetry procedure is not individualized. Thus, applying a size-based conversion coefficient is paramount in estimating the absorbed dose in pediatric chest CT

Towards novel methods of dosimetry in pediatric and neonatal head computed tomography: Comparative study using two novel and cost effective fabricated in-house phantoms.

Despite the fact that doses to paediatric patients from computed tomography (CT) examinations are of special concern, only few data or studies for setting of paediatric diagnostic reference levels (DRLs) have been published. In this study, doses to children were estimated from chest and head CT, in order to study the feasibility of DRLs for these examinations. It is shown that for the DRLs, patient dose data from different CT scanners should be collected in age or weight groups, possibly for different indications. For practical reasons, the DRLs for paediatric chest CT should be given as a continuous DRL curve as a function of patient weight. For paediatric head CT, DRLs for a few age groups could be given. The users of the DRLs should be aware of the calibration phantom applied in the console calibration for different paediatric scanning protocols. The feasibility of DRLs should be re-evaluated every 2-3 y.

Estimates of individual patient risk, and epidemiologic studies assessing potential late effects, must use patient size–specific dose estimates—they cannot use only scanner output (volume CT dose index or dose-length product).

Background.Patients, especially children, are exposed to substantially high doses of ionising radiation during computed tomography (CT) procedures. Children are several times more susceptible to ionising radiation than adults. Diagnostic reference levels (DRLs) are an important tool for monitoring and optimising patient radiation exposure from radiological procedures. The aim of this study is to estimate the ionising radiation exposure doses and set local DRLs for head CT examinations according to age and to compare local DRLs with national and European DRLs and with literature data in other countries.Materials and methods.Scan parameters of single-phase head CT examinations were collected. Patients were grouped by age in the following intervals: <1, 1−5, 5−10, 10−15 and 15−18 years. Local age-based DRLs set as the 3rd quartile of the median dose-length product (DLP) were calculated. Literature analysis was performed on PubMed search engine on inclusion criteria: publication date 2015–2020, used keywords paediatric computed tomography, paediatric CT, diagnostic reference levels (DRLs). The 23 articles discussing paediatric DRLs were further analysed.Results.Data was collected from 194 paediatric head CT examinations performed in 2019. The median DLP values for head CT were 144.3, 233.7, 246.4, 288.9, 315.5 for <1, 1−5, 5−10, 10−15 and 15−18 years old groups. Estimated local DRLs for head CT examinations are 170, 300, 310, 320, 360 mGy*cm for <1, 1−5, 5−10, 10−15 and 15−18 years age groups respectively and 130, 210, 275, 320 mGy*cm for 0−3 months, 3 months−1 year, 1−6 years and ≥ 6 years age groups respectively. Conclusions.Results of this study showed that settled new local DRLs of head CT examinations were 2–4 times lower than national DRLs and about 2 times lower than European DRLs. Moreover, the study indicated that paediatric head CT doses are significantly lower in comparison with those indicated in the majority of published data from other hospitals over the last 6 years. Patient dose assessment and local DRLs establishment plays important role in future exposure optimisation.

This study aims to review the existing literature on diagnostic reference levels (DRLs) in paediatric computed tomography (CT) procedures and the methodologies for establishing them. A comprehensive literature search was done in the popular databases such as PubMed and Google Scholar under the key words ‘p(a)ediatric DRL’, ‘dose reference level’, ‘diagnostic reference level’ and ‘DRL’. Twenty-three articles originating from 15 countries were included. Differences were found in the methods used to establish paediatric CT DRLs across the world, including test subjects, reference phantom size, anatomical regions, modes of data collection and stratification techniques. The majority of the studies were based on retrospective patient surveys. The head, chest and abdomen were the common regions. The volume computed tomography dose index (CTDIvol) and dose–length product (DLP) were the dosimetric quantities chosen in the majority of publications. However, the size-specific dose estimate was a growing trend in the DRL concept of CT. A 16 cm diameter phantom was used by most of the publications when defining DRLs for head, chest and abdomen. The majority of the DRLs were given based on patient age, and the common age categories for head, chest and abdomen regions were 0–1, 1–5, 5–10 and 10–15 years. The DRL ranges for the head region were 18–68 mGy (CTDIvol) and 260–1608 mGy cm (DLP). For chest and abdomen regions the variations were 1.0–15.6 mGy, 10–496 mGy cm and 1.8–23 mGy, 65–807 mGy cm, respectively. All these DRLs were established for children aged 0–18 years. The wide range of DRL distributions in chest and abdomen regions can be attributed to the use of two different reference phantom sizes (16 and 32 cm), failure to follow a common methodology and inadequate dose optimisation actions. Therefore, an internationally accepted protocol should be followed when establishing DRLs. Moreover, these DRL variations suggest the importance of establish a national DRL for each country considering advanced techniques and dose reduction methodologies.

BackgroundWith the clinical release of a photon counting detector-based computed tomography (CT) system, the potential benefits of this new technology need to be evaluated clinically. Literature concerning this new generation of detector is sparse, especially in the field of pediatric radiology. Therefore, this study outlines our initial experience with ultra-low dose chest CT imaging on the new photon counting CT system.Materials and methodsA pediatric phantom (1-year old, CIRS ATOM phantom, model 704 [CIRS-computerized imaging reference system, Norfolk, VA]) was scanned at different dose levels and different image quality levels to define a protocol for clinical examinations. Next, 20 consecutive pediatric non-contrast ultra-low dose chest CT examinations were evaluated for radiation dose and diagnostic image quality using a 4-point Likert-scale—1 = excellent, 4 = bad image quality—by two radiologists in a consensus reading. This retrospective analysis was approved by the local research ethics committee.ResultsChest CT examinations performed at ultra-low radiation dose (effective dose 0.19 ± 0.07 mSv; size-specific dose estimate 0.45 ± 0.14 mGy) in pediatric patients ages (2.6 ± 1.8 years) show good to excellent image quality for lung structures (1.4 ± 0.4) and moderate image quality for soft tissue structures (2.8 ± 0.2).ConclusionPediatric ultra-low dose chest CT examinations are feasible with the new generation photon counting detector-based CT system. The benefits of this technology must be evaluated for pediatric patients from the outset.

BackgroundIn recent times, size-specific dose estimate (SSDE) has been the ideal metric for accurate estimation of individual patient doses in computed tomography (CT) examinations. The objective of this study was to estimate patient radiation doses based on SSDE and the water-equivalent diameter (DW) as an effect tool for dose optimization in paediatric head CT at two facilities in Tamale Metropolis, in the northern region of Ghana. This is a preliminary retrospective study conducted on 57 paediatric patients (comprising 32 males and 25 females), aged newborns to 16 years old, who underwent head CT examinations. Patient head sizes were determined in terms DW, which was calculated by manual contouring the circumference of the CT images excluding the background to measure the region of interest (ROI) using the mid-slice axial CT images. SSDE was calculated as the product of CTDIvol and the size-specific conversion coefficients (CTDIvol, 16 to SSDE) obtained from the American Association of Physicists in Medicine (AAPM) Report 293.ResultsAt facility ‘A’, the median SSDE values for patients, aged 3 months to 1 year, 1 to 6 years, and older than 6 years were 46.1 mGy, 39.6 mGy, and 48.2 mGy, respectively. The corresponding CTDIvol values were 42.3 mGy, 39.1 mGy, and 51.7 mGy. Facility ‘B’ reported median SSDE values of 36.0, 39.2, and 43.8 mGy, with corresponding CTDIvol values of 28.7, 39.8, and 46.9 mGy for the same age categories. For all age groups, the two facilities showed significant differences in SSDE values (44.72 mGy vs. 39.77 mGy, p = 0.009) and CTDIvol values (45.72 mGy vs. 40.60 mGy, p = 0.03). Some of the age group doses were up to 25.3% in CTDIvol and 25.8% in SSDE higher than those found in published data.ConclusionsThe SSDEs estimated showed significant variations between the two facilities, indicating a possible variability of scan protocols for paediatric head CT examinations. The SSDEs obtained in this study could be useful for optimization of paediatric routine head CT examinations.

Background: Children have a potential risk from radiation exposure because they are more sensitive to radiation than adults. Objective: The purpose of this work is to estimate image quality according to tube voltage (kV) and radiation dose in pediatric computed tomography (CT) using deep learning reconstruction (DLR). Methods: Phantom images of children and adults were obtained for kV, radiation dose, and image reconstruction methods. The CT emits a fan beam to the opposite detector, and the geometry of the detector was symmetrical. Phantom images of children and adults were acquired at a volume CT dose index (CTDIvol) from 0.5 to 10.0 mGy for tube voltages at 80, 100, and 120 kV. A DLR was used to reconstruct the phantom image, and filtered back projection (FBP) and iterative reconstruction (IR) were also performed for comparison with the DLR. Image quality was evaluated by measuring the contrast-to-noise ratio (CNR) and noise. Results: Under the same imaging conditions, the DLR images of pediatric and adult phantoms generally provided improved CNR and noise compared with the FBP and IR images. At a similar CNR and noise, the FBP, IR, and DLR of the pediatric images showed a dose reduction compared with the FBP, IR, and DLR of the adult images, respectively. In terms of the effect of tube voltage, the CNR of the 100 kV DLR images was higher than that of the 120 kV DLR images. Conclusion: According to the results, since pediatric CT images maintain the same image quality at lower doses compared with adult CT images, DLR can improve image quality while reducing the radiation dose in children’s abdominal CT scans.

Children are at greater risk of radiation exposure than adults because the rapidly dividing cells of children tend to be more radiosensitive and they have a longer expected life time in which to develop potential radiation injury. Some studies have surveyed computed tomography (CT) radiation doses and several studies have established diagnostic reference levels according to patient age or body size; however, no survey of CT radiation doses with a large number of patients has yet been carried out in South Korea.The aim of the present study was to investigate the radiation dose in pediatric CT examinations performed throughout South Korea.From 512 CT (222 brain CT, 105 chest CT, and 185 abdominopelvic CT) scans that were referred to our tertiary hospital, a dose report sheet was available for retrospective analysis of CT scan protocols and dose, including the volumetric CT dose index (CTDIvol), dose-length product (DLP), effective dose, and size-specific dose estimates (SSDE).At 55.2%, multiphase CT was the most frequently performed protocol for abdominopelvic CT. Tube current modulation was applied most often in abdominopelvic CT and chest CT, accounting for 70.1% and 62.7%, respectively. Regarding the CT dose, the interquartile ranges of the CTDIvol were 11.1 to 22.5 (newborns), 16.6 to 39.1 (≤1 year), 14.6 to 41.7 (2–5 years), 23.5 to 44.1 (6–10 years), and 31.4 to 55.3 (≤15 years) for brain CT; 1.3 to 5.7 (≤1 year), 3.9 to 6.8 (2–5 years), 3.9 to 9.3 (6–10 years), and 7.7 to 13.8 (≤15 years) for chest CT; and 4.0 to 7.5 (≤1 year), 4.2 to 8.9 (2–5 years), 5.7 to 12.4 (6–10 years), and 7.6 to 16.6 (≤15 years) for abdominopelvic CT. The SSDE and CTDIvol were well correlated for patients <5 years old, whereas the CTDIvol was lower in patients ≥6 years old.Our study describes the various parameters and dosimetry metrics of pediatric CT in South Korea. The CTDIvol, DLP, and effective dose were generally lower than in German and UK surveys, except in certain age groups.

The purpose of this study is to present the multivariate analysis of the size-specific dose estimate (SSDE) and E in pediatric computed tomography (CT) imaging. Pediatric patients scheduled for CT scans of the head, thorax, and abdomen from July 2022 to February 2024 were included in the prospective study. The water-equivalent diameter (Dw), SSDE, and E were computed for each examination using the dose report of CT console display computed tomography dose index (CTD1vol) and dose length product (DLP). The correlation between SSDE and E on CTD1vol, Dw, AreaROI, body mass index, Size⁄(LAT+AP), age, fsize, and HUmean in the region of interest was examined using the multivariate statistical analysis with 95% level of significance (P < 0.05). The relationship between Dw and Size⁄(LAT+AP), Size⁄(LAT+AP), and fsize versus age was investigated using linear regression analysis. The mean values of SSDE for noncontrast head CT and contrast-enhanced CT were found 71.36 mGy and 97.38 mGy, respectively. While as, the mean SSDE for contrast-enhanced thorax CT was observed to be 5.82 mGy, which is less than the mean SSDE of 6.40 mGy for noncontrast thorax CT imaging. The range of the SSDE for contrast-enhanced abdomen CT is 2.05 mGy to 22.13 mGy with a mean SSDE of around 5.71 mGy and for noncontrast abdomen imaging, mean value of SSDE was 5.58 mGy. The mean value of “E” for noncontrast thorax CT imaging was observed to be 2.7 mSv with minimum and maximum 1.17 mSv to 10.10 mSv respectively, which less than the mean effective dose is of 3.64 mSv observed for contrast enhanced thorax CT imaging. The multivariate analysis suggests that SSDE is significantly correlated with CTD1vol, Dw, and E is found significantly dependent on DLP for both contrast enhanced and noncontrast imaging with p < 0.05. A strong positive correlation was found between Dw and Size⁄(LAT+AP), form linear regression analysis. The SSDE is crucial for radiologists evaluating pediatric CT scans and is now an international standard expected to be widely adopted. The strong positive correlation between Dw versus Size⁄(LAT+AP), indicates that Size⁄(LAT+AP),can be used as surrogate in estimate SSDE when Dw calculation is not feasible for pediatric CT imaging.

Purpose: To investigate the effectiveness of automatic exposure control (AEC) in pediatric CT examinations in terms of volume CT dose index (CTDIvol), size‐specific dose estimates (SSDE), and water‐equivalent size‐specific dose estimates (SSDEw). Methods: We selected 179 pediatric chest CT examinations of patient ages 1 ∼ 15 taken with or without AEC (AEC: 88, FIXED: 91). A 16 slice MDCT(Sensation 16, Siemens) was used with tube potentials of 80kVp. The reference level for AEC was different for each patient. We assigned CT exams into one of four age groups: under 2, 25, 6&amp;–10, and under 15. We segmented body regions using a seeded region growing method. The effective diameter (Deff) and the water‐equivalent diameter (DW) were calculated at each slice. CTDIvol was extracted from the conventional DICOM dose report image using optical character recognition (OCR) technique, and then SSDE and SSDEw were derived according to AAPM TG 204 based on Deff and DW. The patient dose was compared for with and without AEC exams using those 3 CT dose metrics. Results: Patient dose of exams with AEC was lower in all age groups regardless of the 3 CT dose metrics. CTDIvol, SSDE, and SSDEw with AEC were 1.61±1.13, 2.85±1.29, and 3.23±1.53 mGy and those without AEC were 2.86±1.34, 5.42±2.61, and 6.21±1.93 mGy, which represent dose reduction of AEC exams by 56.3%, 52.6%, and 52.0%, respectively. Conclusions: Our study revealed that patient dose of exams with AEC was substantially lower than that without AEC by 52 ∼ 56.3 % in pediatric chest CT examinations. Our study results suggest that AEC technique is recommended in pediatric CT exams. The research was supported by the Converging Research Center Program through the Ministry of Education, Science and Technology (2012K001498)