CT Dose Index Research Articles

Low-dose high-resolution chest CT in adults with cystic fibrosis: intraindividual comparison between photon-counting and energy-integrating detector CT

BackgroundRegular disease monitoring with low-dose high-resolution (LD-HR) computed tomography (CT) scans is necessary for the clinical management of people with cystic fibrosis (pwCF). The aim of this study was to compare the image quality and radiation dose of LD-HR protocols between photon-counting CT (PCCT) and energy-integrating detector system CT (EID-CT) in pwCF.MethodsThis retrospective study included 23 pwCF undergoing LD-HR chest CT with PCCT who had previously undergone LD-HR chest CT with EID-CT. An intraindividual comparison of radiation dose and image quality was conducted. The study measured the dose-length product, volumetric CT dose index, effective dose and signal-to-noise ratio (SNR). Three blinded radiologists assessed the overall image quality, image sharpness, and image noise using a 5-point Likert scale ranging from 1 (deficient) to 5 (very good) for image quality and image sharpness and from 1 (very high) to 5 (very low) for image noise.ResultsPCCT used approximately 42% less radiation dose than EID-CT (median effective dose 0.54 versus 0.93 mSv, p < 0.001). PCCT was consistently rated higher than EID-CT for overall image quality and image sharpness. Additionally, image noise was lower with PCCT compared to EID-CT. The average SNR of the lung parenchyma was lower with PCCT compared to EID-CT (p < 0.001).ConclusionIn pwCF, LD-HR chest CT protocols using PCCT scans provided significantly better image quality and reduced radiation exposure compared to EID-CT.Relevance statementIn pwCF, regular follow-up could be performed through photon-counting CT instead of EID-CT, with substantial advantages in terms of both lower radiation exposure and increased image quality.Key PointsPhoton-counting CT (PCCT) and energy-integrating detector system CT (EID-CT) were compared in 23 people with cystic fibrosis (pwCF).Image quality was rated higher for PCCT than for EID-CT.PCCT used approximately 42% less radiation dose and offered superior image quality than EID-CT.Graphical

Paediatric computed tomography diagnostic reference levels in Africa: A systematic review.

Improvements in computed tomography (CT) technology in terms of image quality and reduction in absorbed dose have increased its applications in medical imaging. Diagnostic reference levels (DRLs) help to identify high radiation doses that are unusually delivered to patients undergoing exposure to ionising radiation. The aim of this review was to provide an overview of published studies by African researchers towards establishing paediatric CT DRLs in Africa. The search for articles was conducted using some relevant literature search engines including PubMed, Scopus, Science Direct, Google Scholar and Web of Science. Two reviewers were involved in the article selection process which involved a three-stage screening process of identifying; article titles, abstracts and full-test reading. One hundred and seventy-four articles were identified from the database, PubMed (30), Scopus (21), Google Scholar (53), Web of Science (25) and Science Direct (45). Fifty duplicated articles were excluded before screening. Twelve peer-reviewed articles were included in this study based on the inclusion criteria. DRL values in terms of computed tomography dose index volume of head for the age groupings 0-1, 1-5, 5-10 and 10-15 were 27, 36.6, 39.5 and 47.5 mGy while the dose length product values were 461.6, 664, 872 and 978 mGy.cm respectively. The DRLs were calculated as 75th percentile of the local DRLs reported by the 12 articles included in this review. This review has shown that only few of the African countries (19%) have published studies on paediatric CT DRLs. There were variations in the DRLs published by the various authors which indicate that harmonisation and standardisation of paediatric CT protocols is essential for the optimisation of paediatric doses.

Radiation dose reduction and image quality in pediatric paranasal sinus CT: with automatic tube current modulation and iterative reconstruction technique.

Our objective is to evaluate radiation dose and image quality in pediatric paranasal sinus computed tomography (CT) with automatic tube current modulation (ATCM) and sinogram-affirmed iterative reconstruction algorithm (SAFIRE). CT scans from 80 patients were divided into two groups: Group A [80 kVp, pitch 1.5, 40 mAs, the filtered back projection (FBP) algorithm] and Group B (70 kVp, pitch 3, ATCM with reference at 40 mAs, SAFIRE strengths 1-5). We have evaluated image quality and radiation dose. Group B demonstrated significantly lower volume computed tomography dose index, dose-length product, and effective dose than Group A (0.13±0.03 vs. 1.57±0.01mGy, 2.27±0.82 vs. 19.88±2.01mGy·cm, and 0.0081±0.0017 vs. 0.079±0.013mSv, respectively; P<.001). Increasing SAFIRE strengths correlated with noise reduction and SNR enhancement. Group B's noise and SNRsoft at SAFIRE strength 5 were comparable with Group A. Images reconstructed with SAFIRE strength 5 in Group B exhibit comparable image quality with FBP in Group A.

Characterization of kilovoltage x-ray image guidance system with a novel post-processing algorithm on a new slip ring-mounted radiotherapy system.

This study evaluates the performance of a kilovoltage x-ray image-guidance system equipped with a novel post-processing optimization algorithm on the newly introduced TAICHI linear accelerator (Linac). A comparative study involving image quality tests and radiation dose measurements was conducted across six scanning protocols of the kV-cone beam computed tomography (CBCT) system on the TAICHI Linac. The performance assessment utilized the conventional Feldkamp-Davis-Kress (FDK) algorithm and a novel Non-Local Means denoising and adaptive scattering correction (NLM-ASC) algorithm. Image quality metrics, including spatial resolution, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR), were evaluated using a Catphan 604 phantom. Radiation doses for low-dose and standard protocols were measured using a computed tomography dose index (CTDI) phantom, with comparative measurements from the Halcyon Linac's iterative CBCT (iCBCT). The NLM-ASC algorithm significantly improved image quality, achieving a 300%-1000% increase in CNR and SNR over the FDK-only images and it also showed a 100%-200% improvement over the iCBCT images from Halcyon's head protocol. The optimized low-dose protocols yielded higher image quality than the standard FDK protocols, indicating potential for reduced radiation exposure. Clinical implementation confirmed the TAICHI system's utility for precise and adaptive radiotherapy. The kV-IGRT system on the TAICHI Linac, with its novel post-processing algorithm, demonstrated superior image quality suitable for routine clinical use, effectively reducing image noise without compromising other quality metrics.

Establishing Local Diagnostic Reference Levels for CT Angiography Examinations

Objective: Computed tomography angiography (CTA) examinations are performed to diagnose blood vessel anomalies. However, this examination results in a significant radiation dose being received by the patient. Local diagnostic reference levels (DRLs) are necessary for determining the extent of radiation dose during examinations. Therefore, the main objective of this study is to establish local DRL values for CTA examinations.Material and Methods: In this study, a total of 213 participants underwent CTA examination; wherein: 67 underwent computed tomography (CT) cerebral angiography (CTCA), 80 underwent CT pulmonary angiography (CTPA), 40 underwent CT lower limb angiography with aortogram (CTLLA), and 26 underwent CT upper limb angiography (CTULA). Body mass index along with the circumference of the body were calculated. A number of dose descriptors; such as computed tomography dose index volume (CTDIvol) and dose length product (DLP), were collected, and DLP was used to calculate the effective dose, using the conversion factor.Results: For the angiography phase, CTCA, CTPA, CTLLA, and CTULA had median CTDIvol values of: 31.62, 6.38, 12.16, and 10.12 mGy, respectively. Median DLP and effective dose for CTCA were: 1388.64 mGy*cm &amp; 4.30 mSv, CTPA were 243 mGy*cm &amp; 3.41 mSv, CTLLA were 1855.86 mGy*cm &amp; 12.06 mSv, and CTULA were 945.98 mGy*cm &amp; 2.93 mSv, respectively. Conclusion: The estimated local DRLs were lower than the international standard for the angiographic phase; however, the dose exceeded the international standard when the entire examination was considered. This study revealed the need for dose optimization in CTA examinations.

Quantification of bone microarchitecture using photon-counting CT at different radiation doses: A comparison with µCT

PurposeAccurate measurements of trabecular bone microarchitecture are required for a proper assessment of bone fragility. Photon-counting detector CT (PCD-CT) has different technical properties than conventional CT, resulting in higher resolution and thereby potentially enabling in-vivo measurement of trabecular microarchitecture. The purpose of this study was to quantify trabecular bone microarchitectural parameters with PCD-CT at varying radiation doses and compare this to µCT as gold standard. MethodBoth distal radii, distal tibiae, femoral heads, and two vertebrae were dissected from one human. All specimens were scanned ex-vivo on a PCD-CT system (slice increment 0.1 mm; pixel size 0.1042–0.127 mm) and a µCT system (isotropic voxel size 49–68.4 µm). The radiation doses of the PCD-CT scans were varied from 2.5 to 120 mGy based on the volume CT dose index (CTDIvol32). For the PCD-CT scans, contrast-to-noise ratio and trabecular sharpness were calculated and compared between radiation doses. µCT and PCD-CT scans were registered. The trabecular bone was then segmented from all PCD-CT and µCT scans and split into cubes with 6-mm edge length. For each cube, bone volume over total volume, trabecular thickness, trabecular number, and trabecular heterogeneity were calculated and compared between corresponding PCD-CT and µCT cubes. ResultsWith increasing dose, contrast-to-noise ratio and trabecular sharpness values increased for the PCD-CT images. Already at the lowest dose, high correlations between the trabecular microarchitectural parameters between µCT and PCD-CT were found (R2 = 0.55–0.95), which improved with increasing radiation dose (R2 = 0.76–0.96 at 20 mGy). ConclusionsPCD-CT can be used to quantify trabecular bone microarchitecture, with accuracy comparable to µCT and at clinically relevant radiation doses.

Assessing the influence of dose modulation on water equivalent diameter estimation in pediatric head CT imaging

Pediatric head computed tomography (CT) scans necessitate precise determination of radiation dose to optimize image quality while minimizing patient exposure. This study explores the influence of head size variation on radiation dose and image quality using phantom and patients set, aiming to investigate the efficacy of Automatic Exposure Control (AEC) in dose modulation. Image noise and radiation dose were assessed using with and without AEC, maintaining a constant tube current of 180 mA. The correlation between CT dose index volume (CTDIvol) and water-equivalent diameter (Dw) was examined across 134 image sets, revealing an exponential relationship indicative of AEC's contribution to elevated radiation exposure in larger heads. Furthermore, a slice-based analysis demonstrated a consistent variation in tube current along the slice location, effectively modulated by Dw. However, discrepancies in tube current were observed in the caudal region, suggesting the influence of factors beyond section size. Refinement of analysis improved curve fitting, highlighting the importance of section size in dose modulation. AEC proved essential in maintaining image quality consistency across slices, with inactive AEC resulting in lower image noise in cranial slices. These findings highlight the significance of AEC-based dose modulation in pediatric head CT to ensure optimal image quality while minimizing radiation exposure, emphasizing the need for comprehensive understanding and implementation of AEC systems from different manufacturers.

Assessment of image quality and establishment of local acceptable quality dose for computed tomography based on patient effective diameter.

We aim to develop modified clinical indication (CI)-based image quality scoring criteria (IQSC) for assessing image quality (IQ) and establishing acceptable quality doses (AQDs) in adult computed tomography (CT) examinations, based on CIs and patient sizes. CT images, volume CT dose index ( ), and dose length product (DLP) were collected retrospectively between September 2020 and September 2021 for eight common CIs from two CT scanners at a central hospital in the Kingdom of Bahrain. Using the modified CI-based IQSC and a Likert scale (0 to 4), three radiologists assessed the IQ of each examination. AQDs were then established as the median value of and DLP for images with an average score of 3 and compared to national diagnostic reference levels (NDRLs). Out of 581 examinations, 60 were excluded from the study due to average scores above or below 3. The established AQDs were lower than the NDRLs for all CIs, except for oncologic follow-up for large patients (28 versus 26mGy) in scanner A, besides abdominal pain for medium patients (16 versus 15mGy) and large patients (34 versus 27mGy), and diverticulitis/appendicitis for medium patients (15 versus 12mGy) and large patients (33 versus 30mGy) in scanner B, indicating the need for optimization. CI-based IQSC is crucial for IQ assessment and establishing AQDs according to patient size. It identifies stations requiring optimization of patient radiation exposure.

Reproducibility of a single-volume dynamic CT myocardial blood flow measurement technique: validation in a swine model

BackgroundWe prospectively assessed the reproducibility of a novel low-dose single-volume dynamic computed tomography (CT) myocardial blood flow measurement technique.MethodsThirty-four pairs of measurements were made under rest and stress conditions in 13 swine (54.3 ± 12.3 kg). One or two acquisition pairs were acquired in each animal with a 10-min delay between each pair. Contrast (370 mgI/mL; 0.5 mL/kg) and a diluted contrast/saline chaser (0.5 mL/kg; 30:70 contrast/saline) were injected peripherally at 5 mL/s, followed by bolus tracking and acquisition of a single volume scan (100 kVp; 200 mA) with a 320-slice CT scanner. Bolus tracking and single volume scan data were used to derive perfusion in mL/min/g using a first-pass analysis model; the coronary perfusion territories of the left anterior descending (LAD), left circumflex (LCx), and right coronary artery (RCA) were automatically assigned using a previously validated minimum-cost path technique. The reproducibility of CT myocardial perfusion measurement within the LAD, LCx, RCA, and the whole myocardium was assessed via regression analysis. The average CT dose index (CTDI) of perfusion measurement was recorded.ResultsThe repeated first (Pmyo1) and second (Pmyo2) single-volume CT perfusion measurements were related by Pmyo2 = 1.01Pmyo1 − 0.03(ρ = 0.96; RMSE = 0.08 mL/min/g; RMSE = 0.07 mL/min/g) for the whole myocardium, and by Preg2 = 0.86Preg1 + 0.13(ρ = 0.87; RMSE = 0.31 mL/min/g; RMSE = 0.29 mL/min/g) for the LAD, LCx, and RCA perfusion territories. The average CTDI of the single-volume CT perfusion measurement was 10.5 mGy.ConclusionThe single-volume CT blood flow measurement technique provides reproducible low-dose myocardial perfusion measurement using only bolus tracking data and a single whole-heart volume scan.Relevance statementThe single-volume CT blood flow measurement technique is a noninvasive tool that reproducibly measures myocardial perfusion and provides coronary CT angiograms, allowing for simultaneous anatomic-physiologic assessment of myocardial ischemia.Key PointsA low-dose single-volume dynamic CT myocardial blood flow measurement technique is reproducible.Motion misregistration artifacts are eliminated using a single-volume CT perfusion technique.This technique enables combined anatomic-physiologic assessment of coronary artery disease.Graphical

A Proposal for a Process from as Low as Reasonably Achievable to an Ultra-Low-Level Goal in Chest Computed Tomography.

Background/Objectives: To define and evaluate a radiation dose optimization process for chest computed tomography (CT) imaging. Methods: Data from unenhanced and enhanced chest CT acquisitions performed between June 2018 and January 2020 in adult patients were included in the study. Images were acquired on a Siemens SOMATOM® Definition Edge CT. Dose values, including Dose.Length Product (DLP) and Volume CT Dose Index (CTDIvol), were collected. Low doses (LDs, 25th percentiles), achievable doses (ADs, 50th percentiles), and diagnostic reference levels (DRLs, 75th percentiles) were calculated before and after parameter modifications. A process was defined and applied to patient data. For unenhanced chest CT, data were differentiated according to three groups: high dose (HD), optimized dose (OD), and ultra-low dose (ULD). Dosimetric changes between protocols were expressed as mean CTDIvol % (CI95%). A Mann and Whitney statistical test was used. The diagnostic quality score (DQS) of a subset of 70 randomly selected CT examinations was evaluated by one radiologist. The DQS was scored according to a three-point Likert scale: (1) poor (definite diagnosis impossible), (2) fair (evaluation of major findings possible), and (3) excellent (exact diagnosis possible). Results: Data were collected from 1929 patients. For unenhanced chest CT protocols, only one process loop was run. A dose comparison between the chest CT protocol before the use of the process and the three groups showed a decrease of -38.3% (9.7%) and -93.4% (24.2%) for OD and ULD, respectively, and an increase of +29.4% (4.7%) for HD. For the enhanced chest CT protocol, two optimization loops were performed, and they resulted in a mean dose reduction of -50.0% (2.6%) compared to the pre-optimization protocol. For all protocols, the DQS was greater than or equal to 2. Conclusions: We proposed a radiation dose optimization process for chest CT that could significantly reduce the dose without compromising diagnosis.

Performance of Iterative Reconstruction in Image Space Algorithm in Combination with Automatic Tube Current Modulation Compared to Filtered Back Projection in Brain CT Scan.

High-quality images with minimum radiation dose are considered a challenge in Computed Tomography (CT) scans. The current study aimed to assess the efficacy of the Iterative Reconstruction in Image Space (IRIS) algorithm combined with Automatic Tube Current Modulation (ATCM) compared to Filtered Back Projection (FBP) in brain CT scans. In this cross-sectional study, 200 patients underwent to brain CT scan, and images were then reconstructed using both FBP and IRIS. The CT Number (CTN), noise, and Signal-to-Noise Ratio (SNR) were computed for different tissues from CT images. The performance of two algorithms under different exposure conditions was evaluated using a water phantom. Two experienced radiologists assessed the image quality. Volume CT Dose Index (CTDIvol) and Dose Length Product (DLP) were recorded for each scan. FBP reconstruction exhibited higher noise and lower SNR compared to IRIS, both with and without ATCM. Noise levels significantly increased for FBP combined with ATCM. Subjective analysis showed higher performance for IRIS without ATCM compared to other approaches. The mean CTDIvol with and without ATCM was 20.04±3.33 and 36.37±4.65 mGy, respectively. In the phantom study, the noise with IRIS remained lower than that with FBP even with a 42% dose reduction. IRIS algorithm can preserve the image quality when radiation dose is significantly reduced by ATCM in brain CT scan. Implementation of IRIS combined with ATCM is recommended for brain CT examinations.

Image Findings and Radiation Dose in Lung CT Scan of Patients With COVID-19 in Hamadan

Background: Computed tomography (CT) scan plays an important role in the diagnosis of the COVID-19. Lung involvement appears in different forms on CT images. Absorbed dose to the patients may exceed diagnostic reference levels. This study aimed to investigate clinical symptoms, findings of lung CT scan, and absorbed dose to the patients. Methods: This cross-sectional descriptive study was conducted in two CT scan centers in Hamadan: Besat and Sina. CT images of 163 patients with positive real-time polymerase chain reaction (PCR) tests were interpreted by six experienced radiologists. Volume CT dose index (CTDIvol), dose length product (DLP), and effective dose were calculated in both centers and compared using the Mann-Whitney statistical test. Results: The most common findings in the CT images were ground-glass opacification (GGO), consolidation, and the combination of GGO and consolidation. CTDIvol, DLP, and effective dose to the patients were respectively 1.64±5.24 mGy, 177.12±59.03 mGy.cm, and 3.01±1.00 mSv in Sina hospital and 4.58±1.91 mGy, and 2.60±1.02 mSv in Besat hospital. The difference between quantities in the two centers was statistically significant (P&gt;0.05). Conclusion: The most common findings in lung CT images of patients with positive polymerase chain reaction (PCR) tests were GGO and consolidation. Furthermore, there were differences in radiation dose to patients between hospitals, indicating the need for optimization.

Application of low-dose CT in image-guided radiotherapy based on CT-linac

BackgroundImage-guided radiation therapy (IGRT) involves online medical imaging systems. CT-guided imaging systems not only have high image quality but also allow for direct dose calculation for radiation treatment planning, making it an ideal image guidance method. However, the imaging dose from CT images may pose additional risks to patients. Therefore, the aim of this study was to evaluate the substitutability of using low-dose CT images for IGRT. Materials and methodsThe CIRS-062 phantom, Catphan 604 phantom, CT dose index phantom were used to obtain the conversion curves of the CT values to the relative electron density (RED), image quality, and imaging dose of the low-dose CT, respectively. Catphan 604 phantom and clinical cases were used to analyze the feasibility of low-dose CT for dose calculation. ResultsNo significant differences were observed in the conversion curves of CT values to RED between low-dose and standard-dose CT scans. In terms of image quality, the geometric distortion of low-dose CT was 0.1 mm, which was the same as that of standard-dose CT. The spatial resolution of the images was 0.42–0.45 lp/mm, which was slightly better than that of standard-dose CT (0.40–0.44 lp/mm). The image uniformity was 98.4%–99.0%, slightly worse than that of standard-dose CT (99.4%–99.5%), but still met the clinical requirements. The imaging dose was 2.96–4.62 mGy, significantly lower than that of standard-dose CT (9.71–26.68 mGy), especially for head CT protocol. In terms of dose calculation, the γ passing rates were not lower than 98% for either the Catphan 604 phantom or the clinical cases. ConclusionLow-dose CT can significantly reduce the imaging dose without a significant loss of image quality and can be directly used for dose calculation in radiation treatment planning, providing a safer and more effective image guidance method for IGRT.

Optimal image quality and radiation doses with optimal tube voltages/currents for pediatric anthropomorphic phantom brains.

Using pediatric anthropomorphic phantoms (APs), we aimed to determine the scanning tube voltage/current combinations that could achieve optimal image quality and avoid excessive radiation exposure in pediatric patients. A 64-slice scanner was used to scan a standard test phantom to determine the volume CT dose indices (CTDIvol), and three pediatric anthropomorphic phantoms (APs) with highly accurate anatomy and tissue-equivalent materials were studied. These specialized APs represented the average 1-year-old, 5-year-old, and 10-year-old children, respectively. The physical phantoms were constructed with brain tissue-equivalent materials having a density of ρ = 1.07 g/cm3, comprising 22 numbered 2.54-cm-thick sections for the 1-year-old, 26 sections for the 5-year-old, and 32 sections for the 10-year-old. They were scanned to acquire brain CT images and determine the standard deviations (SDs), effective doses (EDs), and contrast-to noise ratios (CNRs). The APs were scanned by 21 combinations of tube voltages/currents (80, 100, or 120 kVp/10, 40, 80, 120, 150, 200, or 250 mA) and rotation time/pitch settings of 1 s/0.984:1. The optimal tube voltage/current combinations yielding optimal image quality were 80 kVp/80 mA for the 1-year-old AP; 80 kVp/120 mA for the 5-year-old AP; and 80 kVp/150 mA for the 10-year-old AP. Because these scanning tube voltages/currents yielded SDs, respectively, of 12.81, 13.09, and 12.26 HU, along with small EDs of 0.31, 0.34, and 0.31 mSv, these parameters and the induced values were expediently defined as optimal. The optimal tube voltages/currents that yielded optimal brain image quality, SDs, CNRs, and EDs herein are novel and essentially important. Clinical translation of these optimal values may allow CT diagnosis with low radiation doses to children's heads.

Proposing Multiregional Diagnostic Reference Levels for Common CT Angiography Examinations in Saudi Arabia.

Diagnostic reference levels (DRLs) are crucial tools for optimizing radiation exposure during different radiological examinations. This study aimed to establish preliminary DRLs for commonly performed computed tomographic angiography (CTA) examinations in Saudi Arabia. Data for three types of CTA examinations (cerebral, pulmonary, and lower-extremity) were collected from six medical cities across Saudi Arabia. Data sets related to 723 CTAs with a mean patient weight of 75 kg were analysed in detail. The DRL values were determined based on the 75th, median, and 25th CT dose index volume (CTDIvol) and dose length product (DLP) values. The established DRLs were 1221 mGy cm for cerebral CTAs, 475 mGy cm for pulmonary CTAs, and 1040 mGy cm for lower-extremity CTAs. These values were comparable to those reported in other studies. This study provides preliminary DRLs for three common CTA procedures in Saudi Arabia. The widespread implementation of a low kVp and a high level of image reconstruction (IR) presents an opportunity for further dose reduction. These findings can serve as a foundation for future nationwide DRL surveys and the optimization of CTA imaging protocols in Saudi Arabia.

Estimating Effective Diameter and Scan Length of Abdomen and Pelvis for Radiation Dose Optimization in Computed Tomography Imaging Suitable for the Indian Population – A Preliminary Study

Abstract Background: Utilization of computed tomography (CT) has dramatically increased during the last decade with a concurrent increase in exposure to ionizing radiation. Even low levels of exposure have been linked to the development of cancer. Various dose reduction and optimization techniques have been attempted to minimize the risk. Dose optimization becomes crucial when scanning thin and small-built individuals, particularly children. Reference phantoms of European or North American descent are used to develop radiological protocols. CT dose index (CTDI) metrics like scan length, volume CTDI, and dose-length product help to measure the amount of radiation dose received by patients during CT scans. Methodolgy: We studied the anatomical dimensions of the CT abdomen and pelvis from the topographic and tomographic images using the standard bony landmarks in 340 children and 500 adults (F = 250, M = 250) and. Cross-sectional measurements and effective diameter were also used to generate CT phantom models. Results: Using measured variables, phantom models have been generated in different age groups in children and adults representative of the Indian population showing a significant increase in dimensions from pediatric to adult phantom. Dimensions vary from classic reference phantoms of European or North American descent. Conclusion: Diagnostic reference levels must be adjusted according to the age of the patient, size of organs, or surface area of examination as body proportions vary between age groups, sex, and race. Data from this study can be used to generate the age- and sex-specific preset protocols for dose optimization in the adult Indian and pediatric population to minimize exposure risk, particularly in young children.

Establishing Diagnostic Reference Levels and Radiation Dose for Pediatric Head Age-Based Using Computed Tomography in Khartoum State

Computed tomography (CT) is a powerful clinical tool for the diagnosis and management of patients, enabling faster and more accurate diagnosis and the avoidance of interventional surgical techniques. A diagnostic reference level (DRL) is a tool used to aid in optimization of protection in the medical exposure of patients for diagnostic and interventional procedures. It is used in medical imaging with ionizing radiation to indicate whether, in routine conditions, the patient dose or administered activity (amount of radioactive material) from a specified procedure is unusually high or low for that procedure. Radiation dosage variance is one of the topics that arise when dealing with CT devices within medical imaging centers. Diagnostic reference levels have not been established in Sudan. The aim of this study is to propose DRLs for CT of the head for 4 pediatric age groups. The 2 levels that this study covers are volume CT dose index based on a 16-cm phantom (CTDIvol [mGy]) and the dose-length products (DLPs [mGy • cm]). These levels were investigated by conducting a survey to 6 healthcare facilities. The survey consists of questions focused on pediatric exposure parameters, CT protocols, and radiation doses for pediatric age groups &lt;1, 1-5, 5-10, and 10-16 years. For the 4 age groups in the 6 facilities that responded, the mean, 25th, 50th, and 75th percentile values of CTDIvol (mGy) for head CT were for infants (&lt;1 year), 21.2, 14.4, 17.6, and 27.0, respectively; for 1-5 years, 36.5, 15.7, 34.5, and 38.1, respectively; for 5- to 10-year group, the CTDIvol was found to be 40, 15.7, 33.5, and 47.6, respectively, and for the last group of 10-16 years, 41.6, 15.7, 37.4, and 58.3, respectively. The corresponding DLP (mGy • cm) for head CT, the mean, 25th, 50th, and 75th percentile values were as follows: for infants (&lt;1 year), 472.9, 326.9, 385.3, and 545.5, respectively; for 1-5 years, 742.9, 509.1, 689.3, and 902.9, respectively; for 5-10 years, 1,130.4, 501.7, 924.2, and 1,667.4, respectively; for 10-16 years, 1,226.4, 595.4, 870.1, and 1,255.3, respectively. The total mean CTDIvol (mGy) was 38.0, and the total mean DLP (mGy · cm) was 1,001.6. These values have been compared with other values from other similar studies; the summary for these comparisons concluded that the majority of CTDIvol 16-cm phantom and DLP 16-cm phantom values for the head were higher than DRLs reported from other studies in other countries. Therefore, for risk reduction, it is necessary to establish DRLs for pediatric CT in Sudan.

Characterizing pediatric head patient size in Moroccan population: Establishing age-dependent relationships for accurate CT dose estimation

Accurate dose estimation in computed tomography (CT) scans is crucial and relies on precise normalization of output dose, typically measured by the volume CT dose index (CTDIvol). Key metrics, including effective diameter (Deff) and water-equivalent diameter (Dw), play pivotal roles in characterizing patient size. However, a notable gap exists in delineating the specific relationships between age and head patient size (Deff and Dw) for pediatric patients in Morocco. The primary objective of this study was to establish these critical associations between patient age and head patient size (Deff and Dw), providing a foundation for calculating size-specific dose estimates (SSDE) in pediatric head CT examinations. A retrospective analysis of data from 134 pediatric patients, aged 0–13 yr, comprising 71 males and 63 females who underwent head CT scans, was conducted. Utilizing the Radiant DICOM Viewer, patient sizes were measured in terms of both lateral and anterior-posterior dimensions for Deff and Dw calculations based on CT images in DICOM format. Our analysis revealed robust correlations between patient size (Deff and Dw) and the patient’s age, with R2 values ranging from 0.65 to 0.86. Notably, larger Dw values were consistently observed compared to Deff. For male patients, Deff measurements ranged from 9.02 to 18.77 cm, with Dw values spanning 9.83 to 20.16 cm. Female patients exhibited Deff values ranging from 8.77 to 17.41 cm and Dw values ranging from 8.92 to 18.37 cm. These findings shed light on the crucial relationship between age and patient size, facilitating more precise dose calculations.

A Segmentation-based Automated Calculation of Patient Size and Size-specific Dose Estimates in Pediatric Computed Tomography Scans

Background and Purpose: Size-specific dose estimates (SSDE) have been introduced into computed tomography (CT) dosimetry to tailor patients’ unique sizes to facilitate accurate CT radiation dose quantification and optimization. The purpose of this study was to develop and validate an automated algorithm for the determination of patient size (effective diameter) and SSDE. Materials and Methods: A MATLAB platform was used to develop software of algorithms based on image segmentation techniques to automate the calculation of patient size and SSDE. The algorithm was used to automatically estimate the individual size and SSDE of four CT dose index phantoms and 80 CT images of pediatric patients comprising head, thorax, and abdomen scans. For validation, the American Association of Physicists in Medicine (AAPM) manual methods were used to determine the patient’s size and SSDE for the same subjects. The accuracy of the proposed algorithm in size and SSDE calculation was evaluated for agreement with the AAPM’s estimations (manual) using Bland–Altman’s agreement and Pearson’s correlation coefficient. The normalized error, system bias, and limits of agreement (LOA) between methods were derived. Results: The results demonstrated good agreement and accuracy between the automated and AAPM’s patient size estimations with an error rate of 1.9% and 0.27% on the patient and phantoms study, respectively. A 1% percentage difference was found between the automated and manual (AAPM) SSDE estimates. A strong degree of correlation was seen with a narrow LOA between methods for clinical study (r &gt; 0.9771) and phantom study (r &gt; 0.9999). Conclusion: The proposed automated algorithm provides an accurate estimation of patient size and SSDE with negligible error after validation.

Evaluation of an in-use chest CT protocol in lung cancer screening - A single institutional study.

Lung cancer is the most common cause of cancer-related death worldwide and therefore there has been a growing demand for low-dose computed tomography (LDCT) protocols. To investigate and evaluate the dose and image quality of patients undergoing lung cancer screening (LCS) using LDCT in Norway. Retrospective dosimetry data, volumetric CT dose index (CTDIvol) and dose-length product (DLP), from 70 average-size and 70 large-size patients who underwent LDCT scan for LCS were included in the survey. Effective dose and size-specific dose were calculated for each examination and were compared with the American Association of Physicists in Medicine (AAPM) requirement. For a quantitative image quality analysis, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were determined for different regions in the chest with two iterative reconstruction techniques, iDose and Iterative Model Reconstruction. Differences in dose and image quality between average-size and large-size patients were evaluated by Independent sample t test, and Wilcoxon signed rank test within the same patient group. The independent sample t test revealed significant differences (p < .05) in dose values between average-size and large-size patients. Mean CTDIvol and DLP for average-size patients were 2.8mGy and 115mGy.cm, respectively, with appropriate increment for the large-size patients. Image quality (image noise, SNR, and CNR) did not significantly differ between patient groups when images were reconstructed with a model based iterative reconstruction algorithm. The screening protocol assessed in this study resulted in CTDIvol values that were compliant with AAPM recommendation. No significant differences in objective image quality were found between patient groups.