Strategies for Reducing Radiation Dose in CT for Pediatric Patients: How We Do It

Techniques and Strategies to Minimize Radiation Exposure in Pediatric Computed Tomography (CT) Abdominal Examinations: A Review

As children are more vulnerable to radiation-induced cancers and have longer life expectancies, it is essential to implement strict radiation protection measures in pediatric imaging. This study aimed to review radiation dose-minimizing measures in pediatric abdominal computed tomography (CT) examinations. A systematic search across various databases, including Web of Science, PubMed, SpringerLink, ScienceDirect, and Google Scholar, yielded a total of 7,314 articles. The search used keywords that aligned with the objectives of the study. This study included 77 publications after applying the criteria for inclusion and exclusion. We carefully reviewed these selected articles for compliance with the inclusion criteria and excluded them if they did not meet the specified criteria. Only 12 articles fulfilled the strict criteria. An in-depth review of 12 selected articles demonstrated the radiation dose reduction techniques and strategies, which include prefiltering and post-processing algorithms, careful adjustment of exposure parameters such as tube voltage (kVp) and current (mAs), and the establishment of diagnostic reference levels (DRL). Reduction of radiation exposure in pediatric CT imaging demands multifaceted approaches. To reduce the ionizing radiation dose while still obtaining high-quality diagnostic images, healthcare practitioners should adhere to DRL, adjust exposure factors, implement prefiltration, employ AI, and use post-processing algorithms.

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

OBJECTIVE

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

CT Assessment of Aortopulmonary Septal Defect: How to Approach It?

An aortopulmonary septal defect or aortopulmonary window (APW) is a rare cardiovascular anomaly with direct communication between the ascending aorta and the main pulmonary artery leading to a left-to-right shunt. It is accompanied by other cardiovascular anomalies in approximately half of patients. In order to avoid irreversible sequelae, interventional or surgical treatment should be performed as soon as possible. Cardiovascular CT, as a fast, non-invasive technique with excellent spatial resolution, has an increasing role in the evaluation of patients with APW, enabling precise and detailed planning of surgical treatment of APW and associated anomalies if present. This article aims to review the anatomical and clinical features of aortopulmonary septal defect with special emphasis on its detection and characterization by a CT examination.

Dual-Layer Detector Head CT to Maintain Image Quality While Reducing the Radiation Dose in Pediatric Patients

BACKGROUND AND PURPOSE

Radiation exposure in the CT diagnostic imaging process is a conspicuous concern in pediatric patients. This study aimed to evaluate whether 60-keV virtual monoenergetic images of the pediatric cranium in dual-layer CT can reduce the radiation dose while maintaining image quality compared with conventional images.

MATERIALS AND METHODS

One hundred six unenhanced pediatric head scans acquired by dual-layer CT were retrospectively assessed. The patients were assigned to 2 groups of 53 and scanned with 250 and 180 mAs, respectively. Dose-length product values were retrieved, and noise, SNR, and contrast-to-noise ratio were calculated for each case. Two radiologists blinded to the reconstruction technique used evaluated image quality on a 5-point Likert scale. Statistical assessment was performed with ANOVA and the Wilcoxon test, adjusted for multiple comparisons.

RESULTS

Mean dose-length product values were 717.47 (SD, 41.52) mGy×cm and 520.74 (SD, 42) mGy×cm for the 250- and 180-mAs groups, respectively. Irrespective of the radiation dose, noise was significantly lower, SNR and contrast-to-noise ratio were significantly higher, and subjective analysis revealed significant superiority of 60-keV virtual monoenergetic images compared with conventional images (all P < .001). SNR, contrast-to-noise ratio, and subjective evaluation in 60-keV virtual monoenergetic images were not significantly different between the 2 scan groups (P > .05). Radiation dose parameters were significantly lower in the 180-mAs group compared with the 250-mAs group (P < .001).

CONCLUSIONS

Dual-layer CT 60-keV virtual monoenergetic images allowed a radiation dose reduction of 28% without image-quality loss in pediatric cranial CT.

Modern Paediatric Radiology: Meeting the Challenges in CT and MRI

Radiology plays a very important part in the diagnosis, treatment, and follow-up of children. Computed tomography and magnetic resonance imaging are the two most crucial developments in the modern era. However, the two modalities have their challenges to overcome. Radiation dose is the most unwanted side effect of computed tomography scans while longer scan time along with sedation is a major disadvantage in children during magnetic resonance imaging. Paediatric-specific protocol selection and limiting the exposure to the area of interest aid in reducing the dose during computed tomography scans. Faster scan protocols and sequences can result in imaging without sedation in magnetic resonance imaging. Considering the radiation exposure, "as low as reasonably achievable" principle should be followed strictly in the paediatric population. In this article, possible ways for minimising the radiation dose in computed tomography, as well as effective, short, and sedation-free magnetic resonance imaging, are discussed.

Keywords

computed X-ray tomography; magnetic resonance imaging; pediatrics; radiation exposure; X-ray.

Image quality and diagnostic accuracy of reduced-dose computed tomography enterography with model-based iterative reconstruction in pediatric Crohn's disease patients

This study assessed the image quality and diagnostic accuracy in determining disease activity of the terminal ileum of the reduced-dose computed tomography enterography using model-based iterative reconstruction in pediatric patients with Crohn's disease (CD). Eighteen patients were prospectively enrolled and allocated to the standard-dose (SD) and reduced-dose (RD) computed tomography enterography (CTE) groups (n = 9 per group). Image quality, reader confidence in interpreting bowel findings, accuracy in determining active CD in the terminal ileum, and radiation dose were evaluated. Objective image quality did not show intergroup differences, except for image sharpness. Although reader confidence in detecting mural stratification, ulcer, and perienteric fat stranding of the RD-CTE were inferior to SD-CTE, RD-CTE correctly diagnosed active disease in all patients. The mean values of radiation dose metrics (SD-CTE vs. RD-CTE) were 4.3 versus 0.74 mGy, 6.1 versus 1.1 mGy, 211.9 versus 34.5 mGy∙cm, and 4.4 versus 0.7 mSv mGy∙cm for CTDI_vol, size-specific dose estimation, dose-length product, and effective dose, respectively. RD-CTE showed comparable diagnostic accuracy to SD-CTE in determining active disease of the terminal ileum in pediatric CD patients. However, image quality and reader confidence in detecting ulcer and perienteric fat stranding was compromised.

EFFECTIVE DOSE AND EFFECT OF DOSE MODULATION FOR LOCALIZER RADIOGRAPHS USING APPLIED AND ALTERNATIVE SETTINGS ON TOSHIBA/CANON CT SYSTEMS

The purpose was to estimate the effective dose of Toshiba/Canon thorax localizer radiographs for available parameter settings, and to test their dose modulation ability. Localizer radiographs were acquired of anthropomorphic chest phantoms (body mass indices 29 and 23) using various settings (120-80 kV, 100-10 mA). The milliamperes values were compared from resulting helical scan data. Effective dose was computed for two computed tomography (CT) scanners (Aquilion Prime and One Genesis) using a Monte Carlo-based software. For the smaller phantom, all curves were superimposed. For the larger phantom, most curves were also superimposed, except for the one generated from the lowest parameters. The Aquilion Prime system yielded an effective dose of 0.40/0.56 mSv (male/female) using the default parameters. The localizer radiograph dose could be reduced by >90% without affecting the dose modulation. The dose was further reduced by 30-50% in the One Genesis CT system due to improved beam filtration.

Secondary Pulmonary Vein Stenosis Due to Total Anomalous Pulmonary Venous Connection Repair in Children: Extravascular MDCT Findings

Purpose: To evaluate extravascular findings on thoracic MDCT angiography in secondary pulmonary vein stenosis (PVS) due to total anomalous pulmonary venous connection (TAPVC) repair in children. Materials and Methods: All patients aged ≤18 years with a known diagnosis of secondary PVS after TAPVC repair, confirmed by echocardiography, conventional angiography, and/or surgery, who underwent thoracic MDCT angiography studies between July 2008 and April 2021 were included. Two pediatric radiologists independently examined MDCT angiography studies for the presence of extravascular thoracic abnormalities in the lung, pleura, and mediastinum. The location and distribution of each abnormality (in relation to the location of PVS) were also evaluated. Interobserver agreement between the two independent pediatric radiology reviewers was studied using kappa statistics. Results: The study group consisted of 20 consecutive pediatric patients (17 males, 3 females) with secondary PVS due to TAPVC repair. Age ranged from 2 months to 8 years (mean, 16.1 months). In children with secondary PVS due to TAPVC repair, the characteristic extravascular thoracic MDCT angiography findings were ground-glass opacity (19/20; 95%), septal thickening (7/20; 35%), pleural thickening (17/20; 85%), and a poorly defined, mildly heterogeneously enhancing, non-calcified soft tissue mass (17/20; 85%) which followed the contours of affected pulmonary veins outside the lung. There was excellent interobserver kappa agreement between two independent reviewers for detecting extravascular abnormalities on thoracic MDCT angiography studies (k = 0.99). Conclusion: Our study characterizes the extravascular thoracic MDCT angiography findings in secondary pediatric PVS due to TAPVC repair. In the lungs and pleura, ground-glass opacity, interlobular septal thickening, and pleural thickening are common findings. Importantly, the presence of a mildly heterogeneously enhancing, non-calcified mediastinal soft tissue mass in the distribution of the PVS is a novel characteristic thoracic MDCT angiography finding seen in pediatric secondary PVS due to TAPVC repair.

Extravascular MDCT Findings of Pulmonary Vein Stenosis in Children with Cardiac Septal Defect

Purpose: To retrospectively investigate the extravascular thoracic MDCT angiography findings of pulmonary vein stenosis (PVS) in children with a cardiac septal defect. Materials and Methods: Pediatric patients (age ≤ 18 years) with cardiac septal defect and PVS, confirmed by echocardiogram and/or conventional angiography, who underwent thoracic MDCT angiography studies from April 2009 to April 2021 were included. Two pediatric radiologists independently evaluated thoracic MDCT angiography studies for the presence of extravascular thoracic abnormalities in: (1) lung and airway (ground-glass opacity (GGO), consolidation, pulmonary nodule, mass, cyst, septal thickening, fibrosis, and bronchiectasis); (2) pleura (pleural thickening, pleural effusion, and pneumothorax); and (3) mediastinum (mass and lymphadenopathy). Interobserver agreement between the two independent pediatric radiology reviewers was evaluated with kappa statistics. Results: The final study group consisted of 20 thoracic MDCT angiography studies from 20 consecutive individual pediatric patients (13 males (65%) and 7 females (35%); mean age: 7.5 months; SD: 12.7; range: 2 days to 7 months) with cardiac septal defect and PVS. The characteristic extravascular thoracic MDCT angiography findings were GGO (18/20; 90%), septal thickening (9/20; 45%), pleural thickening (16/20; 80%), and ill-defined, mildly heterogeneously enhancing, non-calcified soft tissue mass (9/20; 45%) following the contours of PVS in the mediastinum. There was a high interobserver kappa agreement between two independent reviewers for detecting extravascular abnormalities on thoracic MDCT angiography studies (k = 0.99). Conclusion: PVS in children with a cardiac septal defect has a characteristic extravascular thoracic MDCT angiography finding. In the lungs and pleura, GGO, septal thickening, and pleural thickening are frequently seen in children with cardiac septal defect and PVS. In the mediastinum, a mildly heterogeneously enhancing, non-calcified soft tissue mass in the distribution of PVS in the mediastinum is seen in close to half of the pediatric patients with cardiac septal defect and PVS.

Cardiovascular imaging modalities in the diagnosis and management of rheumatic heart disease

Rheumatic heart disease (RHD) is prevalent in sub-Saharan Africa, where the capacity for diagnosis and evaluation of disease severity and complications is not always optimal. While the medical history and physical examination are important in the assessment of patients suspected to have RHD, cardiovascular imaging techniques are useful for confirmation of the diagnosis. Echocardiography is the workhorse modality for initial evaluation and diagnosis of RHD. Cardiovascular magnetic resonance is complementary and may provide additive information, including tissue characteristics, where echocardiography is inadequate or non-diagnostic. There is emerging evidence on the role of computed tomography, particularly following valve replacement surgery, in the monitoring and management of RHD. This article summarises the techniques used in imaging RHD patients, considers the evidence base for their utility, discusses their limitations and recognises the clinical contexts in which indications and imaging with various modalities are expanding.

Deep learning assisted differentiation of hepatocellular carcinoma from focal liver lesions: choice of four-phase and three-phase CT imaging protocol

PURPOSE

To evaluate whether a three-phase dynamic contrast-enhanced CT protocol, when combined with a deep learning model, has similar accuracy in differentiating hepatocellular carcinoma (HCC) from other focal liver lesions (FLLs) compared with a four-phase protocol.

METHODS

Three hundred and forty-two patients (mean age 49.1 ± 10.5 years, range 19-86 years, 65.8% male) scanned with a four-phase CT protocol (precontrast, arterial, portal-venous and delayed phases) were retrospectively enrolled. A total of 449 FLLs were categorized into HCC and non-HCC groups based on the best available reference standard. Three convolutional dense networks (CDNs) with the input of four-phase CT images (model A), three-phase images without portal-venous phase (model B) and three-phase images without precontrast phase (model C) were trained on 80% of lesions and evaluated in the other 20% by receiver operating characteristics (ROC) and confusion matrix analysis. The DeLong test was performed to compare the areas under the ROC curves (AUCs) of A with B, B with C, and A with C.

RESULTS

The diagnostic accuracy in differentiating HCC from other FLLs on test sets was 83.3% for model A, 81.1% for model B and 85.6% for model C, and the AUCs were 0.925, 0.862 and 0.920, respectively. The AUCs of models A and C did not differ significantly (p = 0.765), but the AUCs of models A and B (p = 0.038) and of models B and C (p = 0.028) did.

CONCLUSIONS

When combined with a CDN, a three-phase CT protocol without precontrast showed similar diagnostic accuracy as a four-phase protocol in differentiating HCC from other FLLs, suggesting that the multiphase CT protocol for HCC diagnosis might be optimized by removing the precontrast phase to reduce radiation dose.

Individualization of computed tomography protocols for suspected pulmonary embolism: a national investigation of routines

Objective

Given the extensive use of computed tomography (CT) in radiation-sensitive patients such as pregnant and pediatric patients, and considering the importance of tailoring CT protocols to patient characteristics for both the radiation dose and image quality, this study was performed to investigate the extent to which individualization of CT protocols is practiced across Norway.

Methods

This cross-sectional study involved collection of CT protocols and administration of a mini-questionnaire to obtain additional information about how CT examinations are individualized. All public hospitals performing CT to detect pulmonary embolism were invited, and 41% participated.

Results

Tailoring a standard protocol to different patient groups was more common than using dedicated protocols. Most of the available radiation dose-reduction approaches were used. However, implementation of these strategies was not systematic. Children and pregnant patients were examined without using dedicated CT protocols or by using protocol adjustments focusing on radiation dose reduction in 30% and 39% of the hospitals, respectively.

Conclusion

Practice optimization is needed, especially the development of dedicated CT protocols or guidelines that tailor the existing protocol to pediatric and pregnant patients. Practice might benefit from a more systematic approach to individualization of CT examinations, such as inserting tailoring instructions into CT protocols.

International Expert Consensus Statement on Chest Imaging in Pediatric COVID-19 Patient Management: Imaging Findings, Imaging Study Reporting, and Imaging Study Recommendations

Coronavirus disease 2019 (COVID-19) has quickly spread since it was first detected in December 2019 and has evolved into a global pandemic with over 1.7 million confirmed cases in over 200 countries around the world at the time this document is being prepared. Owing to the novel nature of the virus and the rapidly evolving understanding of the disease, there is a great deal of uncertainty surrounding the diagnosis and management of COVID-19 pneumonia in pediatric patients. Chest imaging plays an important role in the evaluation of pediatric patients with COVID-19; however, there is currently little information available describing imaging manifestations of COVID-19 in pediatric patients and even less information discussing the utilization of imaging studies in pediatric patients. To specifically address these concerns, a group of international experts in pediatric thoracic imaging from five continents convened to create a consensus statement describing the imaging manifestations of COVID-19 in the pediatric population, discussing the potential utility of structured reporting during the COVID-19 pandemic, and generating consensus recommendations for utilization of chest radiographs and CT in the evaluation of pediatric patients with COVID-19. The results were compiled into two structured reporting algorithms (one for chest radiographs and one for chest CT) and eight consensus recommendations for the utilization of chest imaging in pediatric COVID-19 infection. © RSNA, 2020.