Size-specific Dose Estimate Research Articles

Comparison of Radiation Dose and Image Quality in Pediatric Abdominopelvic Photon-Counting Versus Energy-Integrating Detector CT.

Adoption of abdominal photon counting detector CT (PCD-CT) into clinical pediatric CT practice requires evidence that it provides diagnostic images at acceptable radiation doses. Thus, this study aimed to compare radiation dose and image quality of PCD-CT and conventional energy-integrating detector CT (EID-CT) in pediatric abdominopelvic CT. This institutional review board-approved retrospective study included 147 children (median age 8.5y; 80 boys, 67 girls) who underwent clinically indicated contrast-enhanced abdominopelvic PCD-CT between October 1, 2022 and April 30, 2023 and 147 children (median age 8.5y; 74 boys, 73 girls) who underwent EID-CT between July 1, 2021 and January 1, 2022. Patients in the 2 groups were matched by age and effective diameter. Radiation dose parameters (CT dose index volume, CTDIvol; dose length product, DLP; size-specific dose estimate, SSDE) were recorded. In a subset of 25 matched pairs, subjective image quality was assessed on a scale of 1 to 4 (1=highest quality), and liver attenuation, dose-normalized noise, and contrast-to-noise ratio (CNR) were measured. Groups were compared using parametric and/or nonparametric testing. Among the 147 matched pairs, there were no significant differences in sex (P=0.576), age (P=0.084), or diameter (P=0.668). PCD-CT showed significantly lower median CTDIvol, DLP, and SSDE (1.6mGy, 63.8mGy-cm, 3.1mGy) compared with EID-CT (3.7mGy, 155.3mGy-cm, 6.0mGy) (P<0.001). In the subset of 25 patients, PCD-CT and EID-CT showed no significant difference in overall image quality for reader 1 (1.0 vs. 1.0, P=0.781) or reader 2 (1.0 vs. 1.0, P=0.817), or artifacts for reader 1 (1.0 vs. 1.0, P=0.688) or reader 2 (1.0 vs. 1.0, P=0.219). After normalizing for radiation dose, image noise was significantly lower with PCD-CT (P<0.001), while CNR in the liver (P=0.244) and portal vein (P=0.079) were comparable to EID-CT. Abdominopelvic PCD-CT in children significantly reduces radiation dose while maintaining subjective image quality, and accounting for dose levels, has the potential to lower image noise and achieve comparable CNR to EID-CT. These data expand understanding of the capabilities of PCD-CT and support its routine use in children.

Size-Specific Dose Estimate for Chest of Adult Patients in 128- Slice Computed Tomography at Rajavithi Hospital

Aims: To determine the patient radiation dose using Size-Specific Dose Estimates (SSDEs) for chest CT in adult patients performed with 128-slice CT technology. Study Design: A descriptive cross-sectional study was conducted as a retrospective analysis. Place and Duration of Study: Department of Radiology, Rajavithi Hospital, between April 1 and September 30, 2021. Methods: We included 500 patients (209 males, 291 females). All patients underwent chest contrast enhancement with a venous phase protocol. The patient radiation dose in terms of SSDE was calculated based on AP+Lat dimensions, effective diameter, and water-equivalent diameter. SSDEs was measured from the middle slice of the scan range. The conversion factors following body size and composition were applied according to the AAPM Reports No. 204 and 220 recommendations. Additionally, the study assessed the effective dose and dose-length product (DLP). Key parameters, including DLP, CTDIvol, effective dose, and SSDEs at the 75th percentile, were evaluated to determine radiation dose levels. These values were then compared with established national and international diagnostic reference levels. Results: The study found that the mean DLP was 301.74 mGy·cm, CTDIvol was 8.38 mGy, effective dose was 4.22 mSv, SSDE (AP+Lat) was 11.80 mGy, SSDE (Effective Diameter) was 11.86 mGy, and SSDE (Dw) was 12.91 mGy. When compared with reference radiation dose values from Thailand and international standards, the DLP, CTDIvol, and effective dose values were found to be lower than both Thai and international reference values. In contrast, the SSDE (AP+Lat) was also lower than previously reported findings. Additionally, the study found no available comparative data for SSDE (Effective Diameter) and SSDE (Dw). Conclusion: The comparison of radiation dose values using SSDE across the three methods revealed highly consistent results. The SSDE values obtained from this study can serve as reference levels for the radiation doses received by patients undergoing CT scans at the Radiology Department of Rajavithi Hospital. These values are instrumental in assessing the appropriateness of radiation doses applied during CT imaging and can serve as benchmarks for future dose optimization efforts. Furthermore, this study highlights the significance of evaluating radiation doses in diagnostic imaging, providing valuable baseline data that enhances our understanding of the radiation risks associated with various types of examinations. Further research is warranted to investigate radiation exposure in computed tomography for other body regions.

Size Specific Dose Estimates for Adult Patients in CT of the Kidney, Ureters, and Bladder (KUB) Based on Effective Diameter and Water Equivalent Diameter

Size Specific Dose Estimates for Adult Patients in CT of the Kidney, Ureters, and Bladder (KUB) Based on Effective Diameter and Water Equivalent Diameter

Comparison of Water-Equivalent and Effective Diameter-Based Size-Specific Dose Estimates in Computed Tomography Pulmonary Angiography: Implications for Radiation Dose Optimization

This retrospective study investigates dose estimation in computed tomography pulmonary angiography (CTPA) by analyzing 200 examinations from 96 male and 104 female patients. Two size-specific dose estimation (SSDE) methods were evaluated: one based on effective diameter (SSDEDeff) and the other on water-equivalent diameter (SSDEDw). The effective diameter (Deff) was manually measured using the lateral (LAT) and anteroposterior (AP) dimensions, while the water-equivalent diameter (Dw) was calculated from the region of interest (ROI) using mean Hounsfield Unit (HU) values and cross-sectional area. SSDE calculations were compared to the conventional CT dose metric, CTDIvol, to assess its underestimation relative to SSDEDw. The findings revealed a dose underestimation of up to 18% for CTDIvol compared to SSDEDw, particularly for patients with larger body habitus. SSDEDeff consistently overestimated the dose by 7.73% compared to SSDEDw, as Deff relied only on external dimensions while Dw considered tissue attenuation for a more individualized dose assessment. High correlations were observed between lateral diameter (dLAT) and both Deff (R2 = 0.9175) and Dw (R2 = 0.7578). However, the systematic overestimation by SSDEDeff emphasizes the importance of clearly specifying the metric used for SSDE, as differences can influence reported doses by 5-10%, affecting clinical dose monitoring and adherence to diagnostic reference levels. This study highlights the limitations of CTDIvol and SSDEDeff compared to SSDEDw, especially in regions with heterogeneous tissue. The results support the use of individualized radiation dose assessments to improve radiation safety, particularly in CTPA, which has seen increased application during the COVID-19 pandemic.

Establishment of baseline size-specific dose estimate (SSDE) for paediatric head computed tomography (CT) examinations

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.

HeadCTDosi: A python-based automated calculation of head water equivalent diameter and size specific dose estimate based on AAPM 220 report

The aim of the current study is to propose an algorithm for the automated calculation of water-equivalent diameter (Dw) and size-specific dose estimate (SSDE) from clinical computed tomography (CT) images in head protocol context, a python-based algorithm was developed in order to execute an interface to read DICOM images and compute the mentioned metrics. All CT datasets were retrospectively acquired by the Siemens emotion 16 C T scanner. The algorithm developed in this study presents a novel approach for preprocessing and analyzing DICOM images obtained from head CT scans. Exploiting a custom Python script, the preprocessing pipeline begins with the conversion of pixel values to Hounsfield Units (HU) to ensure quantitative analysis accuracy. Subsequently, Gaussian filtering reduced noise while preserving essential features, followed by thresholding using Otsu's method for head region segmentation. Morphological operations refined the binary mask, which enhanced the method for contour detection via active contours. The outcome of this procedure is an accurate measurement of the head size metrics, including lateral (LAT) and anteroposterior (AP) dimensions, effective diameter (Deff), and water equivalent diameter (Dw). Statistical analyses are performed to derive mean statistics and compute SSDE using a conversion factor derived from Dw. Validation of the proposed algorithm used images of patients who had undergone head examination in a major pediatric university hospital. The proposed algorithm was compared to IndoseCT v20 b for Dw and SSDE calculations. The Dw values from HeadCTDosi were strongly correlated to those of IndoseCT by R2 = 0.97 and the SSDE values also presented high correlation of R2 = 0.93. This study presents an improved algorithm for calculating Dw and SSDE in the context of head CT, which notably can outperform the manual, subjective, and time-consuming process of contouring the head region, positioning it as a potentially essential tool for routine clinical dose monitoring.

Tube current reduction and iterative image reconstruction for computed tomography myelography

This study aimed to systematically evaluate the impact of a low-dose (LD) protocol using tube current reduction on image quality, the confidence for intervention planning and guidance, and diagnostic yield for computed tomography (CT) myelography. We retrospectively analyzed 68 patients who underwent CT myelography, with 34 investigations performed with a standard-dose (SD) and 34 investigations performed with a LD protocol (using tube current reduction). The different scans were matched considering variables such as sex, age, presence of spinal instrumentation, and body diameter. All images were evaluated by two readers (R1 and R2) using Likert scales. Image noise was measured using attenuation values of paraspinal muscle tissue. Images were reconstructed with model-based iterative reconstruction (post-myelography diagnostic scans) or hybrid reconstruction (planning, periprocedural, and diagnostic scans). Image quality, overall artifacts, image contrast, and confidence for planning or intervention guidance were rated good to perfect for both SD and LD scans according to evaluations of both readers. Inter-reader agreement was good to very good for the images from intervention planning (κ ≥ 0.80) as well as for intervention guidance (κ ≥ 0.77), as well as for diagnostic scans (κ ≥ 0.85). Image noise was similar between SD and LD scans performed for planning of the interventional procedures (model-based iterative reconstruction: SD 45.37 ± 7.29 HU vs. LD 45.17 ± 9.12 HU; hybrid reconstruction: SD 46.05 ± 7.43 HU vs. LD 45.05 ± 8.69 HU; p > 0.05). The volume-weighted CT dose index (CTDIvol) and size-specific dose estimate (SSDE) were significantly lower for the planning scans as well as the periprocedural scans when using the LD protocol as compared to the SD protocol (p < 0.05). In conclusion, implementation of a LD protocol with tube current reduction for CT myelography is a feasible option to reduce radiation exposure, especially when combined with iterative image reconstruction. In our study, LD imaging did not have a relevant negative impact on image quality, confidence for intervention planning or guidance, or diagnostic certainty for CT myelography.

Radiation dose assessment of pediatric computed tomography of the chest: the need to consider patient size.

To evaluate the radiation dose of chest computed tomography (CT) examinations of pediatric patients and the extent to which volume CT dose index (CTDIvol) underestimates radiation dose in comparison to size specific dose estimates (SSDE). Single-center, retrospective study of consecutive unenhanced pediatric (age<18years) chest CTs between October 2015 and October 2016. Radiation dose as well as demographic and clinical data were recorded from 133 chest CTs. Patients were grouped into 4 categories based on mean effective diameter of the chest. SSDE was generated for each patient according to the water equivalent and effective diameter and compared to CTDIvol. Factors associated with higher radiation doses were assessed. CTDIvol underestimated radiation dose by 54.7%, 47.6%, 40.2%, and 31.2% (P<.001) for effective diameter groups 1 to 4, respectively, when compared to SSDE (calculated according to the water equivalent). When calculated according to the effective diameter, CTDIvol underestimated radiation dose by 47.6%, 39.4%, 27%, and 12.3% (P<.001) for effective diameter groups 1 to 4, respectively, when compared to SSDE. CT dose parameters, age, weight, Dw, and mean effective diameter were variables associated with higher radiation doses. CTDIvol systematically underestimated radiation dose in comparison to SSDE in pediatric patients submitted to chest CT and should not be used as the primary parameter to monitor CT protocols in these patients. SSDE calculated according to effective diameter also underestimates the radiation dose compared to SSDE calculated based on water equivalent.

ESTIMATION OF PATIENT RADIATION DOSE WITH SIZE SPECIFIC DOSE ESTIMATE (SSDE) METHOD IN ABDOMEN CT-SCAN EXAMINATION AT SEMEN GRESIK HOSPITAL

CT-Scan abdomen is an examination to see the anatomy and pathology of the abdominal organs, and the scanning image results are in the form of three-dimensional axial images of the body. The radiation dose released from the CT-Scan examination is more significant than other radiology modalities. Therefore, it is very important to estimate the patient's dose accurately. Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) are dose parameters used in CT-Scan to describe the dose value received by the patient. However, these parameters are the output of the CT-Scan, not as the dose received by the patient. The Size Specific Dose Estimate (SSDE) method based on AAPM Report No. 204 is used to determine the estimated dose received by the CT-Scan Abdomen patient. Calculations are done manually and with IndoseCT software. The data used are secondary data of 60 patients, namely 21 females and 39 males, who were on the CT-Scan Abdomen examination without contrast from the Instalasi Radiologi Rumah Sakit Semen Gresik. The SSDE value is obtained from the multiplication between the conversion factor and CTDIvol, where the conversion factor is an effective diameter function. The analysis examined the error value in manual calculations and IndoseCT software in men and women, the relationship between effective diameter and scanning radiation output (CTDIvol), and dose estimation estimates (SSDE). The difference in SSDE values between manual calculations and IndoseCT software was insignificant. The highest error value in women was 3% and 3.2% in men. Meanwhile, the relationship between effective diameter (Deff) and scanning radiation output (CTDIvol) and dose estimation estimates (SSDE) showed that the correlation between effective diameter (Deff) and CTDIvol showed a stronger correlation, namely with R2 around 0.7 in women and men, compared to the correlation between effective diameter (Deff) and SSDE with R2 around 0.03 in women and 0.2 in men. Keywords: CT-Scan, Abdomen, Size Specific Dose Estimate (SSDE).

Development of a novel automated algorithm for patient dosimetry in computed tomography: a step towards the facilitation of size-specific dose estimates and organs dosimetry estimations in a busy clinical workflow

Abstract Accurate dosimetry in computed tomography (CT) is essential for patient safety and effective radiation management. This study presents the development of an automated algorithm designed to enhance patient dosimetry by facilitating size-specific dose estimates (SSDE) and organ dose estimations. Utilizing a Python-based script, the proposed method integrates advanced image preprocessing, contour detection, and mathematical calculations to quantify key metrics from CT images. This automated approach addresses the limitations of manual measurement techniques. A retrospective analysis was conducted on CT axial images from examinations acquired with an 80-detector scanner. The algorithm processes DICOM images, converts pixel values to Hounsfield Units, applies Gaussian smoothing, windowing, and thresholding, followed by morphological operations to refine segmentation. It measures the water equivalent diameter (Dw) and estimates both region SSDE and organ doses, incorporating tissue attenuation. Validation was performed using an adult anthropomorphic ATOM phantom, with organ doses measured by optically stimulated luminescence dosimeters. The results demonstrated the algorithm’s potential in estimating SSDE and organ doses. Validation of the automated method revealed strong correlations for Dw and SSDE between the proposed method and manual measurements of five expert reviewers ranging from 0.86 to 0.99 for determination coefficient. Comparative analysis of organ doses showed close agreement between results from experimental setup against the proposed algorithm. The automated algorithm estimated brain dose with a mean of 21.8 mGy, while measurements from the ATOM phantom and CT Expo indicated 19.74 mGy and 23.05 mGy, respectively. For lung doses, the automated algorithm estimated 12.5 mGy compared to 11.0 mGy from the ATOM phantom and 13.1 mGy from CT Expo. Liver doses were measured at 12.7 mGy by the automated method, versus 12.1 mGy from the ATOM phantom and 11.1 mGy from CT Expo. This study shows the potential of automated image analysis techniques in enhancing dosimetry accuracy in CT examinations.

APPLICATION OF SIZE SPECIFIC DOSE ESTIMATE (SSDE) AS A LOCAL DIAGNOSTIC REFERENCE LEVEL IN HEAD CT SCAN EXAMINATION AT INDRIATI HOSPITAL SOLOBARU, DR. MOEWARDI HOSPITAL SURAKARTA, SLEMAN HOSPITAL, AND NATIONAL BRAIN CENTER HOSPITAL JAKARTA

CT scan is a modality that produces a higher radiation dose compared to other modalities in radiodiagnostic installations. The radiation dose received by patients from examinations with this CT scan device is expressed in the volume CT Dose Index (CTDIvol) and Dose Length Product (DLP), which are dose indicators from the Indonesian Diagnostic Reference Level (DRL) value regulated in the Decree of the Head of the Nuclear Energy Regulatory Agency (BAPETEN) nationally. However, the CTDIvol value is only an indicator of the output dose from the CT scan, and the DLP value is an indicator of the total dose during the examination, which is influenced by the length of the scan. Both do not represent the specific dose received by the patient because the patient's dose depends not only on the output dose but also on the patient's characteristics. The patient's dose, which includes the output dose and patient characteristics, is called the Size-Specific Dose Estimate (SSDE), which is used to estimate the dose received by the patient by including a correction factor depending on the patient's dimensions. This study aims to calculate the SSDE value in a CT Head examination with a standard protocol using the same type of device, namely a 128-slice CT scan in several hospitals. The values of CTDIvol and DLP patients are obtained from the dose report displayed on the CT scan monitor screen in the IndoseCT software. The patient samples studied were patients undergoing CT Head examinations from March 2023 to February 2024, with 100 patients in each hospital. The results of this study obtained local DRL values based on SSDE calculated at Indriati Hospital, Moewardi Hospital, Sleman Hospital, and the National Brain Center Hospital and then compared them with the national TPD values. Based on the SSDE value from Indriati Hospital, the TPD value was 30.26 mGy, Sleman Hospital was 39.5 mGy, Dr. Moewardi Hospital was 49.3 mGy, and RSPON was 51.7 mGy. The TPD value of CT Head examinations without contrast from each hospital was still below the national TPD value of 60 mGy. Keywords: CT scan, diagnostic reference level (DRL), local DRL, national DRL, Size-Specific Dose Estimate (SSDE), IndoseCT.

CT surveillance for type 1 autoimmune pancreatitis: cumulative radiation dose and diagnostic performance for disease relapse.

Long-term follow-up is essential for type 1 autoimmune pancreatitis (AIP) patients due to high relapse rates. The cumulative radiation dose from repeated CT scans during follow-up should not be ignored. We aim to investigate the cumulative radiation dose in AIP patients undergoing CT surveillance and the diagnostic performance of CT in detecting disease relapse. The diagnostic performance of MRI from a secondary cohort during the same period was also investigated. This retrospective single-institutional study included 247 type 1 AIP patients with one or more follow-up CT scans, and 120 patients with MR follow-ups. Four metrics were utilized to report the radiation dose, including the volume computed tomography dose index, the dose length product, size-specific dose estimate and effective dose. The diagnostic performance for AIP relapse was assessed, taking the final clinical diagnosis in retrospect as the reference standard. With a median 2.3-year follow-up period, AIP patients followed up with CT exhibited a median cumulative radiation dose of 37.5 mSv. 11.3% of patients have accumulated doses exceeding 100 mSv. For the 169 patients followed over a year, 30.8% sustained an average annual radiation dose surpassing 20 mSv. The sensitivity/specificity/accuracy of CT for detecting abdominal organ relapse was 64.1%/99.6%/97.0%. For AIP patients followed up with MRI, the sensitivity for detecting disease relapse was 90.5%. Considering the accumulation of radiation dose in AIP patients and the insufficient sensitivity in detecting disease relapse with CT, safer and more sensitive imaging follow-up strategies should be explored. Question CT, as the primary imaging modality for autoimmune pancreatitis (AIP) follow-up, raises concerns regarding radiation exposure and lacks reported diagnostic performance in detecting AIP relapse. Findings CT in AIP follow-up causes significant cumulative radiation exposure and exhibits insufficient sensitivity in relapse detection. Clinical relevance Type 1 AIP necessitates long-term imaging follow-up, yet current guidelines lack consensus regarding the prioritization of CT or MRI for such follow-up. CT is widely used but has radiation concerns and limited sensitivity, calling for safer, efficient strategies.

Clinical diagnostic reference levels and image quality metrics for CT in oncology patients.

In CT, the volumetric CT dose index (CTDIvol), dose-length product (DLP) and patient's size-specific dose estimates (SSDE) are used as diagnostic reference level (DRL) metrics. To develop clinical local DRL values for CT chest-abdomen-pelvis (CAP) examinations using the CTDIvol, DLP and SSDE, and to determine the image quality achieved. In total, 201 cancer patients were included in the study. The scanning parameters, dose metrics from the CT unit and participants' body mass index (BMI) were documented. The local CT DRL values for CAP examinations were defined as the median and 75th percentiles of the dose distribution. The local DRL values given in terms of median CTDIvol ranged between 8.4 mGy and 12.7 mGy for the different types of cancers. The median DLPs ranged from 848 to 1173.4 mGy.cm for the various cancers. Generally, the radiation dose was directly proportional to the BMI and number of scan phases. Significant differences were observed between the DRLs for the various size-related parameters, number of scan phases and BMI classifications. The image quality was clinically satisfactory. No baseline data for clinical DRL values were available for this medical oncology department. The achieved DRLs were similar to published size-specific DRLs. The image quality was maintained during CT imaging. Dose optimisation and image quality assessment should be implemented to ensure optimal scanning parameters for different cancers in CT CAP examinations. The first size-specific local DRL values for CT CAP investigations carried out on oncology patients in South Africa have been established.

Pediatric contrast-enhanced chest CT on a photon-counting detector CT: radiation dose and image quality compared to energy-integrated detector CT.

Photon counting detector (PCD) CT benefits from reduced noise compared with conventional energy-integrating detector (EID) CT, which should translate to improved image quality and reduced radiation exposure for pediatric patients undergoing chest CT with IV contrast. To determine the differences in radiation exposure and image quality of PCD CT and EID CT in pediatric chest CT with intravenous (IV) contrast. In this institutional review board-approved retrospective observational study, 20 scan pairs (20 PCD CT; 20 EID CT) for children who underwent chest CT with IV contrast on both a PCD CT (Siemens NAEOTOM Alpha) and an EID CT (Siemens SOMATOM Definition Edge or Force) within 12months were reviewed independently by three pediatric radiologists for three subjective quality features on 5-point Likert scales: overall quality, small structure delineation, and motion artifact. Objective measures of image quality (image noise, signal-to-noise ratio, and contrast-to-noise ratio) were assessed by a single radiologist in several locations in the chest through region of interest measurement of Hounsfield units (HU) and standard deviation. Patient-related and radiation exposure parameters were collected for each scan and summarized with median and interquartile range (IQR). The Wilcoxon rank-sum test was utilized to compare groups. A P < 0.05 indicated statistical significance. Inter-observer agreement of subjective image quality metrics was analyzed using weighted kappa. Age (14.2years vs 13.8years, P= 0.15), height (P= 0.13), weight (P= 0.21), and BMI (P = 0.24) did not significantly differ between groups. There were 10 male and 3 female patients. Compared to EID CT, PCD CT showed lower radiation exposure parameters including volumetric CT dose index, 1.7mGy (IQR 1.1-2.4mGy) vs 3.8mGy (IQR 2.0-4.7mGy) (P< 0.01), and size-specific dose estimate, 2.6mGy (IQR 1.8-3.1mGy) vs 5.0mGy (IQR 3.3-6.2mGy) (P< 0.01). Objective image quality of lung parenchyma was improved on the PCD CT scanner, including image noise 119.5 HU (IQR 95.4-135.7 HU) vs 143.1 HU (IQR 125.4-169.8 HU) (P < 0.01), signal-to-noise ratio (SNR) -6.1 (IQR -8.4 to -4.8) vs -4.9 (IQR -5.6 to -3.8) (P= 0.01), and contrast-to-noise ratio -63.9 (-84.1 to -57.5) vs -60.5 (-76.3 to -52.5) (P = 0.01). Motion artifact was improved on the PCD CT scanner (P< 0.01). No significant differences in overall image quality or small structure delineation were identified (P= 0.06 and P= 0.31). PCD CT pediatric chest CT had significantly reduced radiation exposure, improved image quality, and reduced motion artifact compared with EID CT.

Assessment of Interobserver and Intraobserver Variabilities in the Measurements of Anteroposterior (AP) and Lateral (LAT) Diameters on Paediatric CT images for Size-Specific Dose Estimation

Introduction Both interobserver and intraobserver variability evaluations are important to validate the data reliability and ensure consistency in measurements. to assess the variability in anteroposterior (AP) and lateral (LAT) diameter measurements of the head and abdomen for determination of effective diameter among paediatric population. The measurements were conducted by various observers.Methods Fifty CT images of paediatric head and abdomen were randomly selected from from five different age groups of paediatric patients, all aged below 18 years old. All images were acquired using the standard exposure protocol for head and abdomen CT scanning. The anteroposterior (AP) and lateral (LAT) diameters were measured on selected CT images of the head and abdomen at specific levels. To ensure measurement consistency, diameters were consistently measured at defined positions: the middle slice for the head and a position between the kidneys or the second lumbar vertebra for the abdomen. All diameter measurements were conducted by three observers and repeated three times. Statistical analysis, including the intraclass correlation coefficient (ICC) and Bland-Altman method for intraobserver and interobserver agreement, were employed to assess measurement consistency.Results The findings showed excellent reliability in all measurements (LCC values &gt; 0.9) for both interobserver and intraobserver. The variability between student, physicist and radiologist was high. The deviation of observer measurements between all observers were also significant for AP and LAT diameters of head and abdomen of the selected CT images. Discussions The findings resulted in high reliability, showing strong agreement among measurements and low variability in measurements among all observers and amongst all participating centres. The variability between the principal investigators was lower, but still substantial. The deviation of observer measurements from the gold rater were also significant for all CT parameters. Conclusion We found excellent reliability for both intra- and interobserver measurements.

Size-specific dose estimates calculated using patient size measurements from scanned projection radiograph in high-resolution chest computed tomography.

Size-specific dose estimates (SSDE) are used to assess patient-specific radiation exposure in Computed Tomography (CT), complementing the volume CT dose index (CTDIvol). This study compared SSDE calculated using patient's lateral size from scan projection radiograph (SPR) with SSDE calculated using water equivalent diameter (Dw) from tomographic images in adult chest high-resolution CT (HRCT). In a single-centre study, the CTDIvol and dose-length product (DLP) were recorded from HRCT dose reports of adult patients. Lateral width (SLat), at the centre of the scan range, from the SPR was measured and the SSDE (SSDER) was calculated using conversion factors related to SLat. Average CT number, area of the slice, and lateral size of the patient (AxLat) were measured on the middle slice. The Dw and SSDE from Dw (SSDEW) were calculated. SSDER and SSDEW were compared using Wilcoxon signed rank test. Correlation between patient size and dosimetry parameters were investigated using Spearman Correlation test with statistical significance at P < 0.05. Bland-Altman plot was also used to test agreement between the two SSDE values. Median CTDIvol, DLP, SSDER and SSDEW were 11.0 mGy, 372 mGy.cm, 11.6 mGy and 12.9 mGy, respectively. Small but statistically significant differences (P < 0.03) were found between SLat and AxLat as well as between SSDER and SSDEW. Bland-Altman analysis resulted in borderline agreement between SSDE values. Moderate correlations were observed between dosimetry quantities and patient size measurements (ρ > 0.640; P < 0.001). SSDEw showed statistically significant correlation (ρ = 0.587 and P < 0.001) with SSDER. SSDER may be used to assess patients' absorbed radiation dose, before the scan, in adult chest HRCT. The median value of SSDER was about 10% lower than the median value SSDEW. However, the SSDEW should be used after the scan to establish effective dose and radiation risk to the patient.

Introduction and evaluation of size-specific DLP for radiation dose estimation in CT examinations.

The increased utilization of computed tomography (CT) has raised concerns about patient radiation exposure. Effective dose (ED), which requires precise estimation, is crucial for assessing and managing these risks. Traditional ED estimation methods, which are based on the dose-length product (DLP), often lack accuracy due to variations in patient size and anatomy. This study aims to evaluate the efficacy of size-specific DLP (SS-DLP), a novel metric that combines the size-specific dose estimate (SSDE) with scan length, to provide a more accurate estimation of radiation exposure from CT examinations. Focusing on adult chest-abdomen-pelvis (CAP) scans, we calculated SSDE and SS-DLP and utilized two simulation tools, Radimetrics and WAZA-ARI, for a detailed analysis. Our findings indicate that SS-DLP is highly correlated with EDs from Monte Carlo simulations, suggesting its reliability. Additionally, SS-DLP showed a moderate reduction in errors based on patient sex and body mass index compared to traditional DLP-based methods. Thus, SS-DLP offers a more accurate and personalized radiation exposure estimate, potentially enhancing patient safety.

Less Dose, Same Care: Evaluating Computed Tomography Utilization for Pediatric Appendicitis

BackgroundAn ultrasonography-first, magnetic resonance imaging-second protocol, and attention to dose reduction was implemented to reduce computed tomography rates for appendicitis at our institution. We aimed to compare current computed tomography usage and report radiation doses at our children's associated system hospitals and referring nonsystem hospitals. MethodsA retrospective study of pediatric patients who underwent appendectomy and had a preoperative computed tomography scan between June 2020 and June 2023 was performed. Demographics and imaging details were abstracted from the medical record. Size-specific dose estimates and effective dose estimates were calculated for each computed tomography. Size-specific dose estimates were compared with American College of Radiology Dose Index Registry diagnostic reference levels. ResultsOf 1,419 patients, 409 (29%) received a computed tomography for appendicitis, a 56% reduction from previous years (2012–2015) (P < .001). Overall, 352 computed tomography scans had dose data available, of which 291 (83%) were performed at system hospitals and 61 (17%) at nonsystem hospitals. The median size-specific dose estimate per computed tomography was 11.0 mGy (interquartile range 7.0, 17.4) for nonsystem hospitals and 9.1 mGy (interquartile range 6.6, 14.0) for system hospitals. The median effective dose per computed tomography was 6.7 mSv (interquartile range 4.3, 12.9) at nonsystem hospitals and 5.1 mSv (interquartile range 3.3, 9.4) at system hospitals. Nienty-three (n = 273) computed tomography scans performed at system hospitals and 30 computed tomography scans (n = 61) at nonsystem hospitals exceeded American College of Radiology Dose Index Registry age-based diagnostic reference levels. ConclusionThe ultrasonography-first, magnetic resonance imaging–second protocol resulted in a significant decrease in computed tomography use for appendicitis diagnosis. Comparison of doses to American College of Radiology Dose Index Registry reference levels suggests that computed tomography protocol optimization may allow for dose reduction at some facilities.

Evaluating the Utilization of the National Cancer Institute Computed Tomography Program for Calculating Size-specific Dose Estimate and Effective Dose in Computed Tomography in Thai Pediatric Patients

The objectives of this study were to assess the feasibility of utilizing computational calculations and the simulation of the National Cancer Institute computed tomography (NCICT) dosimetry system to obtain size-specific dose estimate (SSDE) and effective dose values resulting from the most common CT examinations in Thai pediatric patients and to evaluate age- and size-specific k conversion factor. For the calculation methods, SSDEs were calculated using the American Association of Physicists in Medicine Report No. 220 and 293 methodologies. The results revealed that SSDEs derived from CT scans of the body, obtained through the two different methods, varied by within 10%. The size of the patient and the scanning distance had an impact on the variability of E values derived from NCICT. Age- and size-specific k conversion factors may be used as a first line to estimate risk for the pediatric patients.

Size specific dose estimates and effective dose in multiphase abdomen-pelvis CT examinations

This study estimated the size-specific dose estimates (SSDE) in different scan phases and inter-phase variations of multi-phase abdomen-pelvis CT examinations. Various methods employed for determination of SSDE, which takes into account the size of the patient, were compared for 51 multiphase abdomen-pelvis CT examinations using custom written software. These methods are based on effective diameter, water equivalent diameter derived from region of interest and segmentation techniques, diameter of central image and whole scan series. Significant variation was observed in SSDE of pre-contrast phase in comparison to other phases. The effective dose was also estimated and correlated with SSDE. The results indicate that the underestimation in the dose estimated using the machine parameter, CTDIvol, was in the range of 10%–60% when compared with SSDE. This study concludes that the average SSDE of the whole examination is a better representation of patient dose in the case of multi-phase examinations. It highlights the need for integration of SSDE calculating software in the CT scanner systems for accurate estimation of patient doses.