Third-generation dual-source 70-kVp chest CT angiography with advanced iterative reconstruction in young children: image quality and radiation dose reduction

Clinical Question Influence on Radiation Dose of Cardiac CT Scan in Children

Background: To assess the impact of different clinical questions on radiation doses acquired during cardiac computed tomography in children. Methods: A total of 116 children who underwent cardiac CT on a third-generation dual-source CT scanner were included. The clinical questions were divided into three main categories: the extent of scanning in the z-axis, coronary artery assessment and cardiac function assessment. Radiation dose values represented as a dose-length product (DLP) in mGy*cm were recorded from the CT scanner protocols. Results: There were significantly higher doses in cases with cardiac function assessment (median DLP 348 versus 59 mGy*cm, p < 0.01) and in cases with coronary artery assessment (median DLP 133 versus 71 mGy*cm, p < 0.01). Conclusion: The most important factor was the assessment of cardiac function, where the median radiation dose was 4.3× higher in patients with a request for cardiac function assessment. We strongly recommend that clinical requests for cardiac CT should be carefully considered in the paediatric population.

PURSUING OPTIMAL RADIATION DOSE IN PEDIATRIC CARDIAC CT: A REPORT FROM UNIVERSITY HOSPITAL LEUVEN

BACKGROUND

Computed tomography (CT) balances between high resolution and low radiation dose. Given the greater radiosensitivity of children, it is appropriate to use child-friendly CT-protocols that reduce radiation dose at acceptable image quality.This article states the radiation dose in pediatric cardiac CT-examinations at university hospital Leuven (Belgium) and compares with findings published by similar medical centers. The diagnostic accuracy was simultaneously compared, as it correlates with radiation dose.

MATERIAL AND METHODS

his retrospective observational study analyzed 58 CT-scans of 52 patients. The radiation dose was calculated in effective dose. The image quality was scored qualitatively with a 5-point scale. The diagnostic accuracy, a derivative representation of the image quality, was checked with findings from surgery or conventional angiography.

RESULTS

The mean effective dose in our study population was 1.3 ± 0.4 mSv. The qualitative image quality was on average 'good', elaborated with a score of 4.0 ± 0.2. The diagnostic accuracy was 92%. Comparative literature study provides a mean effective dose of 1.5 mSv and the reported diagnostic accuracy from other centers reaches ≥90%.

CONCLUSIONS

At our center pediatric cardiac CT-scans are obtained with good-to-excellent image quality and high diagnostic accuracy at low radiation doses. These results meet the radiation dose and diagnostic accuracy as published by comparable medical centers.

Pediatric Congenital Lung Malformations: Imaging Guidelines and Recommendations

Congenital lung malformations are a spectrum of developmental anomalies comprised of malformations of the lung parenchyma, airways, and vasculature. Imaging assessment plays a pivotal role in the initial diagnosis, management, and follow-up evaluation of congenital lung malformations in the pediatric population. However, there is currently a lack of practical imaging guidelines and recommendations for the diagnostic imaging assessment of congenital lung malformations in infants and children. This article reviews the current evidence regarding the imaging evaluation of congenital lung malformations and provides up-to-date imaging recommendations for pediatric congenital lung malformations.

Evaluation of complex congenital heart disease with prospective ECG-gated cardiac CT in a single heartbeat at low tube voltage (70 kV) and adaptive statistical iterative reconstruction in infants: a single center experience

The purpose of this study is to evaluate the radiation dose, image quality, and diagnostic accuracy of prospective ECG-gated cardiac CT at 70 kV and adaptive statistical iterative reconstruction (ASIR), with a single source, 512 slice MDCT in the diagnosis of complex congenital heart disease in infants. We retrospectively evaluated 47 infants (ages 1 day to 353 days) with prospective ECG-gated cardiac CT that was performed on a single source 512 slice CT at low tube voltage (70 kV) using a wide detector aperture, adaptive statistical iterative reconstruction algorithm (ASIR), and specific reconstruction software reducing coronary motion artifacts (SnapShot Freeze). All cardiac images were obtained during the first pass of contrast material through the anatomic structures of interest and the targets for the center of the acquisition window were set 45% of the R-R interval during one cardiac cycle without sedation and breath-hold. The median effective dose measured in our study was 0.64 ± 0.16 mSv. The average subjective overall image quality score was 4.34 ± 0.31 (range 3-5). For the determination of objective image quality, Mean Noise (HU), SNR, and CNR values ​​emerged as 20.8, 28.7(for pulmonary artery), and 27.1, respectively. Diagnostic accuracy was 100% for the main purposes for the main clinical indication. During cardiac CT examination, pathologies in addition to cardiac anomalies were found in 9/47 of cases (7 severe airway obstructions,1 posterior diaphragmatic hernia, 1 vertebral anomaly). Prospective ECG-gated cardiac CT scan at 70 kV and ASIR in infants with complex CHD provides low radiation dose (submillisievert) in a single heartbeat with a good objective and subjective image quality. It also provides important benefits in the diagnosis of additional pathology.

CT colonography with spectral filtration and advanced modeled iterative reconstruction in the third-generation dual-source CT: image quality, radiation dose and performance in clinical utility

RATIONALE AND OBJECTIVES

To evaluate image quality, radiation dose and its diagnostic performance in clinical utility of CT colonography (CTC) applying spectral filtration and advanced modeled iterative reconstruction (ADMIRE) techniques in third-generation dual-source CT.

MATERIALS AND METHODS

A total of 125 patients for screening or diagnostic purposes underwent CTC at 120kVp standard dose (120kVp-STD) with filtered-back projection reconstruction (FBP) in supine position, then at a tin-filtered 150 kVp low dose (Sn150kVp-LD) and a tin-filtered 100 kVp ultra-low dose (Sn100kVp-ULD) with ADMIRE reconstruction in prone position. Radiation metrics were recorded. Objective and subjective image qualities were compared, and the diagnostic performance was assessed for both colonic and extracolonic findings using CTC reporting and data system (C-RADS).

RESULTS

The effective dose was significantly lower for Sn150kVp-LD and Sn100kVp-ULD than 120kVp-STD protocol, resulting in 22.5% and 87.5% reductions (1.55±0.30 and 0.25±0.07 mSv vs. 2.00±0.52 mSv; both p<0.01), respectively. Image noise and signal-to-noise ratio were improved significantly for Sn150kVp-LD with ADMIRE compared with 120kVp-STD, both of which had similar excellent 2D and 3D subjective image quality with equivalent diagnostic performance. Sn100kVp-ULD with ADMIRE had decreased subjective image quality and significant different C-RADS extracolonic-score (E-score) compared with 120kVp-STD, however, C-RADS colonic-score (C-score) of that showed no significantly difference.

CONCLUSION

Sn150kVp and Sn100kVp with ADMIRE reconstruction provide an alternative low dose CTC strategy and could be feasible in clinical screening or diagnostic scenarios.

Potential for Radiation Dose Reduction in Dual-Source Computed Tomography of the Lung in the Pediatric and Adolescent Population Compared to Digital Radiography

Low-dose dual-source computed tomography (DSCT) protocols for the evaluation of lung diseases in children and adolescents are of importance since this age group is particularly prone to radiation damage. The aim of this study was to evaluate image quality of low-dose DSCT of the lung and to assess the potential of radiation dose reduction compared to digital radiographs (DR). Three groups, each consisting of 19 patients, were examined with different DSCT protocols using tin prefiltration (Sn96/64/32 ref. mAs at 100 kV). Different strengths of iterative reconstruction were applied (ADMIRE 2/3/4). DSCT groups were compared to 19 matched patients examined with posterior–anterior DR. Diagnostic confidence, detectability of anatomical structures and small lung lesions were evaluated on a 4-point Likert scale (LS 1 = unacceptable, 4 = fully acceptable; a value ≥ 3 was considered acceptable). Effective dose (ED) was 31-/21-/9-fold higher in Sn96/Sn64/Sn32 compared to DR. Diagnostic confidence was sufficient in Sn96/Sn64 (LS 3.4/3.2), reduced in Sn32 (LS 2.7) and the worst in DR (LS 2.4). In DSCT, detectability of small anatomical structures was always superior to DR (p < 0.05). Mean lesion size ranged from 5.1–7 mm; detectability was acceptable in all DSCT groups (LS 3.0–3.4) and superior to DR (LS 1.9; p < 0.05). Substantial dose lowering in DSCT of the pediatric lung enables acceptable detectability of small lung lesions with a radiation dose being about 10-fold higher compared to DR.

Application of 70 kVp in abdominal CT angiography to reduce both radiation and contrast dosage and improve patient comfort for children

BACKGROUND

Low-tube voltage scanning improves CT attenuation value of contrast medium (CM). Thus, we hypothesized that 70 kVp in pediatric abdominal CT angiography (CTA) could be used to reduce both radiation and CM dose and improve patient comfort at the same time.

OBJECTIVE

To evaluate the feasibility of using 70 kVp in pediatric abdominal CTA to reduce radiation dose and CM dose and improve patient care for children.

MATERIALS AND METHODS

Forty-six children needing abdominal CTA were enrolled in the study group using low-dose scanning protocol with 70 kVp and 0.7-1.1 ml/kg contrast dose, and reconstructed with 50%ASIR-V. They were compared with other 46 children in control group with matching body weight and underwent conventional CT scans with 100 kVp, 1.2-1.8 ml/kg contrast dose and reconstructed using 50%ASIR. Image quality of large vessels was evaluated using a 5-point scale. CT value and standard deviation of descending aorta (Ao) was measured, and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Radiation dose, contrast dose, the maximum injection pressure between the two groups were also compared.

RESULTS

Score for displaying large vessels by 70 kVp images was 3.91±0.28, lower than that (4.17±0.38) of the control group (p < 0.05), but fully met the diagnostic requirements. CT value of Ao was 390.87±86.79HU in study group, which is higher than 343.93±49.94HU in control group, while there was no difference in SNR and CNR between two groups; the radiation dose, contrast dosage and injection pressure of the study group were 1.23±0.39mGy, 12.67±7.27 ml and 43.83±17.16psi, respectively, which are significantly lower than the 1.95±0.37mGy, 22.67±7.39 ml, and 77.59±19.68psi of control group.

CONCLUSION

Use of 70 kVp in pediatric abdominal CTA provides diagnostic quality images while significantly reduce radiation and contrast dose, as well as injection pressure to improve patient comfort for children.

Sensitivity of High-Pitch Dual-Source Computed Tomography for the Detection of Anomalous Pulmonary Venous Connection in Infants

PURPOSE

 To evaluate the sensitivity, specificity, and interobserver reliability of high-pitch dual-source computed tomography angiography (CTA) in the detection of anomalous pulmonary venous connection (APVC) in infants with congenital heart defects and to assess the associated radiation exposure.

MATERIALS AND METHODS

 78 pulmonary veins in 17 consecutively enrolled patients with congenital heart defects (6 females; 11 males; median age: 6 days; range: 1-299 days) were retrospectively included in this study. All patients underwent high-pitch dual-source CTA of the chest at low tube voltages (70 kV). APVC was evaluated independently by two radiologists. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV), and interobserver agreement were determined. For standard of reference, one additional observer reviewed CT scans, echocardiography reports, clinical reports as well as surgical reports. In cases of disagreement the additional observer made the final decision based on all available information.

RESULTS

 Detection of APVC with high-pitch dual-source CTA revealed a good sensitivity (91 %) and specificity (99 %), with PPV and NPV of 98 % and 97 %. Interobserver agreement was almost perfect (Kappa = 0.84). The median DLP was 3.8 mGy*cm (IQR 3.3-4.7 mGy*cm) and the median radiation dose was 0.33 mSv (IQR 0.26-0.39 mSv).

CONCLUSION

 High-pitch dual-source CTA in infants with congenital heart defects allows for accurate and reliable assessment of APVC at a low radiation dose.

KEY POINTS

  · High-pitch dual-source CTA enables detection of anomalous pulmonary vein connection with high sensitivity in infants.. · Interrater reliability in the detection of anomalous pulmonary vein connection with high-pitch dual-source CTA is almost perfect.. · Radiation dose of high-pitch dual-source CTA in the cardiac examination of infants is low..

CITATION FORMAT

· Well L, Weinrich JM, Meyer M et al. Sensitivity of High-Pitch Dual-Source Computed Tomography for the Detection of Anomalous Pulmonary Venous Connection in Infants. Fortschr Röntgenstr 2021; 193: 551 - 558.

Comparison of quantitative image quality of cardiac computed tomography between raw-data-based and model-based iterative reconstruction algorithms with an emphasis on image sharpness

BACKGROUND

Image sharpness is commonly degraded on cardiac CT images reconstructed using iterative reconstruction algorithms.

OBJECTIVE

To compare the image quality of cardiac CT between raw-data-based and model-based iterative reconstruction algorithms developed by the same CT vendor in children and young adults with congenital heart disease.

MATERIALS AND METHODS

In 29 patients with congenital heart disease, we reconstructed 39 cardiac CT datasets using raw-data-based and model-based iterative reconstruction algorithms. We performed quantitative analysis of image sharpness using distance_25-75% and angle_25-75% on a line density profile across an edge of the descending thoracic aorta in addition to CT attenuation, image noise, signal-to-noise ratio and contrast-to-noise ratio. We compared these quantitative image-quality measures between the two algorithms.

RESULTS

CT attenuation did not show significant differences between the algorithms (P>0.05) except in the aorta. Image noise was small but significantly higher in the model-based algorithm than in the raw-data-based algorithm (4.8±2.3 Hounsfield units [HU] vs. 4.7±2.1 HU, P<0.014). Signal-to-noise ratio (110.2±50.9 vs. 108.4±50.4, P=0.050) and contrast-to-noise ratio (91.0±45.7 vs. 89.6±45.1, P=0.063) showed marginal significance between the two algorithms. The model-based algorithm showed a significantly smaller distance_25-75% (1.4±0.4 mm vs. 1.6±0.3 mm, P<0.001) and a significantly higher angle_25-75% (77.0±4.3° vs. 74.1±5.7°, P<0.001) than the raw-data-based algorithm.

CONCLUSION

Compared with the raw-data-based algorithm, the model-based iterative reconstruction algorithm demonstrated better image sharpness and higher image noise on cardiac CT in patients with congenital heart disease.

Feasibility of bronchial wall quantification in low- and ultralow-dose third-generation dual-source CT: An ex vivo lung study

PURPOSE

To investigate image quality and bronchial wall quantification in low- and ultralow-dose third-generation dual-source computed tomography (CT).

METHODS

A lung specimen from a formerly healthy male was scanned using third-generation dual-source CT at standard-dose (51 mAs/120 kV, CTDI_vol 3.41 mGy), low-dose (1/4th and 1/10th of standard dose), and ultralow-dose setting (1/20th). Low kV (70, 80, 90, and Sn100 kV) scanning was applied in each low/ultralow-dose setting, combined with adaptive mAs to keep a constant dose. Images were reconstructed at advanced modeled iterative reconstruction (ADMIRE) levels 1, 3, and 5 for each scan. Bronchial wall were semi-automatically measured from the lobar level to subsegmental level. Spearman correlation analysis was performed between bronchial wall quantification (wall thickness and wall area percentage) and protocol settings (dose, kV, and ADMIRE). ANOVA with a post hoc pairwise test was used to compare signal-to-noise ratio (SNR), noise and bronchial wall quantification values among standard- and low/ultralow-dose settings, and among ADMIRE levels.

RESULTS

Bronchial wall quantification had no correlation with dose level, kV, or ADMIRE level (|correlation coefficients| < 0.3). SNR and noise showed no statistically significant differences at different kV in the same ADMIRE level (1, 3, or 5) and in the same dose group (P > 0.05). Generally, there were no significant differences in bronchial wall quantification among the standard- and low/ultralow-dose settings, and among different ADMIRE levels (P > 0.05).

CONCLUSION

The combined use of low/ultralow-dose scanning and ADMIRE does not influence bronchial wall quantification compared to standard-dose CT. This specimen study suggests the potential that an ultralow-dose scan can be used for bronchial wall quantification.

Pediatric head computed tomography with advanced modeled iterative reconstruction: focus on image quality and reduction of radiation dose

BACKGROUND

Iterative reconstruction has become the standard method for reconstructing computed tomography (CT) scans and needs to be verified for adaptation.

OBJECTIVE

To assess the image quality after adapting advanced modeled iterative reconstruction (ADMIRE) for pediatric head CT.

MATERIALS AND METHODS

We included image sets with filtered back projection reconstruction (the cFBP group, n=105) and both filtered back projection and ADMIRE reconstruction (the lower-dose group, n=109) after dose reduction. All five strength levels of ADMIRE and filtered back projection were adapted for the lower-dose group and compared with the cFBP group. Quantitative parameters including noise, signal-to-noise ratio and contrast-to-noise ratio and qualitative parameters including noise, white matter and gray matter differentiation of the supra- and infratentorial levels, sharpness, artifact, and diagnostic accuracy were also evaluated and compared with interobserver agreement.

RESULTS

There was a mean dose reduction of 30.6% in CT dose index volume, 32.1% in dose length product, and 32.1% in effective dose after tube current reduction. There was gradual reduction of noise in air, cerebrospinal fluid and white matter with strength levels of ADMIRE from 1 to 5 (P<0.001). Signal-to-noise ratio and contrast-to-noise ratio in all age groups increased among strength levels of ADMIRE, in sequence from 1 to 5, with statistical significance (P<0.001). Gradual reduction of qualitative parameters was noted among strength levels of ADMIRE in sequence from 1 to 5 (P<0.001).

CONCLUSION

Use of ADMIRE for pediatric head CT can reduce radiation dose without degrading image quality.

Dual-source computed tomography of the lung with spectral shaping and advanced iterative reconstruction: potential for maximum radiation dose reduction

BACKGROUND

Radiation dose at CT should be as low as possible without compromising diagnostic quality.

OBJECTIVE

To assess the potential for maximum dose reduction of pediatric lung dual-source CT with spectral shaping and advanced iterative reconstruction (ADMIRE).

MATERIALS AND METHODS

We retrospectively analyzed dual-source CT acquisitions in a full-dose group (FD: 100 kV, 64 reference mAs) and in three groups with spectral shaping and differing reference mAs values (Sn: 100 kV, 96/64/32 reference mAs), each group consisting of 16 patients (age mean 11.5 years, standard deviation 4.8 years, median 12.8 years, range 1.3-18 years). Advanced iterative reconstruction of images was performed with different strengths (FD: ADMIRE Level 2; Sn: ADMIRE Levels 2, 3 and 4). We analyzed dose parameters and measured noise. Diagnostic confidence and detectability of lung lesions as well as anatomical structures were assessed using a Likert scale (from 1 [unacceptable] to 4 [fully acceptable]).

RESULTS

Compared to full dose, effective dose was reduced to 16.7% in the Sn 96 group, 11.1% in Sn64, and 5.5% in Sn32 (P<0.001). Noise values of Sn64_ADM4 did not statistically differ from those in FD_ADM2 (45.7 vs. 38.9 Hounsfield units [HU]; P=0.132), whereas noise was significantly higher in Sn32_ADM4 compared to Sn64_ADM4 (61.5 HU; P<0.001). A Likert score >3 was reached in Sn64_ADM4 regarding diagnostic confidence (3.2) and detectability of lung lesions (3.3). For detectability of most anatomical structures, no significant differences were found between FD_AM2 and Sn64_ADM4 (P≥0.05).

CONCLUSION

In pediatric lung dual-source CT, spectral shaping together with ADMIRE 4 enable radiation dose reduction to about 10% of a full-dose protocol while maintaining an acceptable diagnostic quality.

Optimal tube voltage for abdominal enhanced CT in children: a self-controlled study

Background

The use of weight-adapted pediatric computed tomography (CT) tube voltage protocols has been suggested, but a consensus standard has not been established and clinical available studies are not sufficient.

Purpose

To determine the best tube voltage for low dose abdominal CT imaging in children.

Material and Methods

Eighty-seven cases who needed three CT exams in a 1–3-month interval between scans were enrolled (mean age = 4.69 ± 3.20 years). The three scans were performed with three different tube voltages at 80 kV, 100 kV, and 120 kV, keeping the same radiation dose and same contrast injection protocol. Patients were divided into five groups for analysis based on their body weight. The subjective image quality of the three exams were evaluated using a 4-point scale (4 being the best) for image noise and image quality. The objective evaluation in terms of CT values and standard deviation in aorta, liver, spleen, pancreas, and kidney were measured to calculate the degree of enhancement and contrast-to-noise ratio (CNR) of organs. One-way ANOVA was used to compare the subjective and objective image quality with respect to different tube voltages and different patient weights.

Result

The 80-kV tube voltage provided the highest overall enhancement and CNR for the entire patient population and the best objective image quality for the 6.1–28.0 kg subgroup.

Conclusion

Patient weight-dependent tube voltage selection maximizes image quality for abdominal enhanced CT in children. The optimal tube voltage for children with weight <28 kg is 80 kV; higher voltages should be selected for children weighing 28.1–50.0 kg.

Initial experience with cinematic rendering for the visualization of extracardiac anatomy in complex congenital heart defects†

OBJECTIVES

Detailed anatomical information is essential for planning of surgical therapy in patients with congenital heart disease. We wanted to determine whether cinematic rendering, the novel 3-dimensional visualization technique, could help paediatric cardiac surgeons achieve better preoperative visualization of the extracardiac anatomy in patients with complex congenital heart defects. Therefore, cinematic rendering was compared to the traditional volume rendering technique by means of a questionnaire with predefined criteria.

METHODS

Picture sets from 20 infant patients (mean age = 17 days) were generated from computed tomography data with both the cinematic rendering and the volume rendering techniques. These were presented side by side in a digital high-resolution portfolio without labelling them. Three experienced paediatric cardiac surgeons were provided with these portfolios and a questionnaire. They were asked to evaluate the images individually in predefined categories on a 4-point Likert scale from 1 = 'fully acceptable' to 4 = 'unacceptable'.

RESULTS

Cinematic rendering scored significantly better values on the Likert scale in 7 of 9 categories, namely 'spatial impression in general', 'depth perception', 'delineation of the atrial appendages/pulmonary veins/peripheral pulmonary arteries', 'assessability of the anterior interventricular sulcus' and 'assessability of the aortic arch branches'.

CONCLUSIONS

Cinematic rendering is a valuable software tool, and our data suggest that it provides significantly better visualization than volume rendering. The surgeons appraised improved depth perception and delineation of structures adjacent to the heart as the most significant advantages.

User-Friendly Vendor-Specific Guideline for Pediatric Cardiothoracic Computed Tomography Provided by the Asian Society of Cardiovascular Imaging Congenital Heart Disease Study Group: Part 1. Imaging Techniques

Optimal performance of pediatric cardiothoracic computed tomography (CT) is technically challenging and may need different approaches for different types of CT scanners. To meet the technical demands and improve clinical standards, a practical, user-friendly, and vendor-specific guideline for pediatric cardiothoracic CT needs to be developed for children with congenital heart disease (CHD). In this article, we have attempted to describe such guideline based on the consensus of experts in the Asian Society of Cardiovascular Imaging CHD Study Group. This first part describes the imaging techniques of pediatric cardiothoracic CT, and it includes recommendations for patient preparation, scan techniques, radiation dose, intravenous injection protocol, post-processing, and vendor-specific protocols.

Advanced CT Techniques for Decreasing Radiation Dose, Reducing Sedation Requirements, and Optimizing Image Quality in Children

CT is an invaluable diagnostic tool for pediatric patients; however, concerns have arisen about the potential risks of ionizing radiation associated with diagnostic imaging in young patients, particularly for pediatric populations that may require serial CT examinations. Recent attention has also been focused on the immediate and long-term risks of administration of anesthetic medications to infants and young children who require sedation to undergo imaging examinations. These concerns can be mitigated with use of advanced CT techniques that can decrease scan time and radiation dose while preserving image quality. In this article, current state-of-the-art CT acquisition techniques are reviewed as part of a comprehensive strategy to reduce radiation dose, decrease sedation needs, and optimize image quality in infants and young children. Three imaging strategies are discussed, including (a) dual-energy CT (DECT), (b) imaging with a low tube potential, and (c) rapid scanning. Consolidating multiphase imaging protocols into a single phase with virtual nonenhanced imaging on DECT scanners, as well as use of low tube voltage, can reduce the radiation dose while increasing the conspicuity of contrast material-enhanced structures with a reduced volume of iodinated contrast material and a reduced rate of injection. Rapid scanning techniques with either ultrahigh pitch at dual-source CT or with wide-area detector single-source CT facilitate scanning without the need for sedation in many children. ^©RSNA, 2019 See discussion on this article by Szczykutowicz .

Improving image quality with model-based iterative reconstruction algorithm for chest CT in children with reduced contrast concentration

OBJECTIVE

To evaluate model-based iterative reconstruction (MBIR) in improving the image quality of chest CT in children with reduced concentration contrast medium (CM).

METHODS

Fifty-six children (median age of 4 years) who received low-dose enhanced chest CT were enrolled as the study group and compared with the control group of 56 children. Both groups used the automatic tube current modulation to achieve age-based noise index values of 11-15 HU. The study group used 100 kVp and reduced CM concentration of 270 mgI/ml, and the images in this group were reconstructed with 50% adaptive statistical iterative reconstruction (ASIR) and MBIR. The control group used 120 kV and standard CM of 320 mgI/ml, and the images in this group were reconstructed with ASIR only. Subjective image quality and objective image quality of the three image sets were evaluated. The subjective quality included overall image noise, enhancement degree, lesion (including mediastinum mass, pulmonary space-occupying lesions, and parenchymal infiltrative lesions) conspicuity, and beam-hardening artifacts. The objective quality included the measurement of noise in the left ventricle and back muscle to calculate signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of ventricle.

RESULTS

There was no difference in radiation dose between the study (CTDIvol of 1.79 ± 1.45 mGy) and control (1.68 ± 0.92 mGy) groups (p = 0.65). However, the study group used 19.7% lower CM dose than the control group (5.84 ± 2.69 vs. 7.27 ± 3.80 gI), and the enhancement in all images met the diagnostic requirements. MBIR reduced image noise by 58.6% and increased SNR and CNR by 143.6% and 165.7%, respectively, compared to ASIR images in the control group. The two ASIR image sets had similar image quality.

CONCLUSION

MBIR improved the image quality of low-radiation-dose chest CT in children at 19.3% reduced CM dose.

Visualization of pleural fissures in infants on computed tomography

Purpose

For infants with prenatally detected lung lesions, a chest CT is performed prior to surgery. The chest CT is performed as close to the surgery date as possible, because it is presumed that the visualization of lung fissures would be poor in the immediate neonatal setting. However, this presumption has never been formally studied. The purpose of this study is to assess differences in lung fissure visualization on chest CT in different infant age groups.

Methods

This was a retrospective study of clinically indicated chest CT approved by the institutional review board performed in infants of different ages. The visibility of pleural fissures was subjectively assessed by three pediatric radiologists who were blinded to age group.

Results

In the 0–2 months age group, 80% of all fissure segments were visible versus 92% in the 5–6 months group (p=0.04) and 95% in the 7–9 months group (p=0.01).

Conclusions

The ability to visualize pleural fissures on CT increases with infant age. This observation should be taken into consideration when choosing the optimal timing of preoperative CT for asymptomatic congenital lung lesions.

Imaging pediatric gastrointestinal stromal tumor (GIST)

BACKGROUND

Gastrointestinal stromal tumors (GIST) are extremely rare in children. Imaging plays a key role in staging and monitoring therapy (surgical and with tyrosine kinase inhibitors). The vast majority of articles addressing imaging of GIST base on adults and are based on CT. The subtype "pediatric GIST" - if at all - is only mentioned in a dependent clause. Although the imaging features in children and adults are similar, histology, clinical course and thus imaging approach are different.

METHODS

A PubMed search using the search terms "Gastrointestinal stromal tumor, GIST, WT GIST, children, pediatric, carney's triad, imaging, staging, follow-up, MRI, CEUS, ultrasonography, Positron emission tomography" was conducted. Studies that reported on laparoscopy, endoscopy and surgical techniques only were excluded.

RESULTS

Based on our selective literature review, we present alternative radiological imaging strategies using MRI, contrast enhanced ultrasound (CEUS) and PET-CT to stage and follow-up pediatric GIST patients. As pediatric GIST often is a chronic disease, minimizing exposure to ionizing radiation is mandatory.

CONCLUSION

MRI, contrast enhanced ultrasound and PET-CT instead of CT are the imaging modalities to evaluate pediatric GIST.

TYPE OF STUDY

Systematic review LEVEL OF EVIDENCE: III.

Pediatric gastrointestinal stromal tumors-a review of diagnostic modalities

Gastrointestinal stromal tumors are exceedingly rare tumors in the pediatric population, as a result many clinicians either may never see this diagnosis or will encounter it only a few times throughout their careers. It is imperative in the pediatric population to follow appropriate steps to ensure a swift diagnosis and referral to specialized centers that are equipped with the multidisciplinary teams accustomed to treating rare diseases. This review aims to discuss the most recent data available on the diagnostic modalities utilized in cases of suspected Pediatric GIST.

Diagnostic yield of 90-kVp low-tube-voltage carotid and intracerebral CT-angiography: effects on radiation dose, image quality and diagnostic performance for the detection of carotid stenosis

OBJECTIVE

To investigate the impact of low-tube-voltage 90-kVp acquisition combined with advanced modeled iterative reconstruction algorithm (Admire) on radiation exposure, image quality, artifacts, and assessment of stenosis in carotid and intracranial CT angiography (CTA).

METHODS

Dual-energy CTA studies of 43 patients performed on a third-generation 192-slice dual-source CT were retrospectively evaluated. Intraindividual comparison of 90-kVp and linearly blended 120-kVp equivalent image series (M_0.6, 60% 90-kVp, 40% Sn-150-kVp) was performed. Contrast-to-noise and signal-to-noise ratios of common carotid artery, internal carotid artery, middle cerebral artery, and basilar artery were calculated. Qualitative image analysis included evaluation of artifacts and suitability for angiographical assessment at shoulder level, carotid bifurcation, siphon, and intracranial by three independent radiologists. Detection and quantification of carotid stenosis were performed. Radiation dose was expressed as dose-length product (DLP).

RESULTS

Contrast-to-noise values of all arteries were significantly increased in 90-kVp compared to M_0.6 (p < 0.001). Suitability for angiographical evaluation was rated excellent with low artifacts for all levels in both image series. Both 90-kVp and M_0.6 showed excellent accordance for detection and grading of carotid stenosis with almost perfect interobserver agreement (carotid stenoses in 32 of 129 segments; intraclass correlation coefficient, 0.94). dose-length product was reduced by 40.3% in 90-kVp (110.6 ± 32.1 vs 185.4 ± 47.5 mGy·cm, p < 0.001).

CONCLUSION

90-kVp carotid and intracranial CTA with Admire provides increased quantitative and similarly good qualitative image quality, while reducing radiation exposure substantially compared to M_0.6. Diagnostic performance for arterial stenosis detection and quantification remained excellent. Advances in knowledge: 90-kVp carotid and intracranial CTA with an advanced iterative reconstruction algorithm results in excellent image quality and reduction of radiation exposure without limiting diagnostic performance.

Investigation of an appropriate contrast-enhanced CT protocol for young patients following the Fontan operation

PURPOSE

Children with congenital heart diseases (CHDs) may need to be followed up with contrast-enhanced CT following the Fontan operation because complications such as the occlusion of conduits may occur. The purpose of the present study was to develop an adequate contrast-enhanced CT protocol for children with CHD following the Fontan operation.

MATERIALS AND METHODS

Between July 2012 and July 2017, 29 CT examinations for 26 patients aged 2-11 years (median 5 years) with CHD following the Fontan operation were performed using dual-source CT. A non-ionized contrast medium was injected through the dorsum manus vein. Scanning began 60 or 70 s after the start of the injection. The delayed phase was randomly selected to be 60 s in 14 cases and 70 s in 15 cases. We evaluated the enhancement of conduits following the Fontan operation at delayed phases.

RESULTS

The CT numbers of conduits at 60 and 70 s were 185 ± 46 and 185 ± 31 HU, respectively (P = 0.97).

CONCLUSION

In contrast-enhanced CT for children after the Fontan operation, both of the delayed phases (60 and 70 s) appeared to be adequate for evaluating intraconduit patency.

Radiation dose management for pediatric cardiac computed tomography: a report from the Image Gently 'Have-A-Heart' campaign

Children with congenital or acquired heart disease can be exposed to relatively high lifetime cumulative doses of ionizing radiation from necessary medical imaging procedures including radiography, fluoroscopic procedures including diagnostic and interventional cardiac catheterizations, electrophysiology examinations, cardiac computed tomography (CT) studies, and nuclear cardiology examinations. Despite the clinical necessity of these imaging studies, the related ionizing radiation exposure could pose an increased lifetime attributable cancer risk. The Image Gently "Have-A-Heart" campaign is promoting the appropriate use of medical imaging studies in children with congenital or acquired heart disease while minimizing radiation exposure. The focus of this manuscript is to provide a comprehensive review of radiation dose management and CT performance in children with congenital or acquired heart disease.

Using imaging as a biomarker for asthma

There have been significant advancements in the various imaging techniques being used for the evaluation of asthmatic patients, both from a clinical and research perspective. Imaging characteristics can be used to identify specific asthmatic phenotypes and provide a more detailed understanding of endotypes contributing to the pathophysiology of the disease. Computed tomography, magnetic resonance imaging, and positron emission tomography can be used to assess pulmonary structure and function. It has been shown that specific airway and lung density measurements using computed tomography correlate with clinical parameters, including severity of disease and pathology, but also provide unique phenotypes. Hyperpolarized ¹²⁹Xe and ³He are gases used as contrast media for magnetic resonance imaging that provide measurement of distal lung ventilation reflecting small-airway disease. Positron emission tomography can be useful to identify and target lung inflammation in asthmatic patients. Furthermore, imaging techniques can serve as a potential biomarker and be used to assess response to therapies, including newer biological treatments and bronchial thermoplasty.

Single-energy pediatric chest computed tomography with spectral filtration at 100 kVp: effects on radiation parameters and image quality

BACKGROUND

Most of the applied radiation dose at CT is in the lower photon energy range, which is of limited diagnostic importance.

OBJECTIVE

To investigate image quality and effects on radiation parameters of 100-kVp spectral filtration single-energy chest CT using a tin-filter at third-generation dual-source CT in comparison to standard 100-kVp chest CT.

MATERIALS AND METHODS

Thirty-three children referred for a non-contrast chest CT performed on a third-generation dual-source CT scanner were examined at 100 kVp with a dedicated tin filter with a tube current-time product resulting in standard protocol dose. We compared resulting images with images from children examined using standard single-source chest CT at 100 kVp. We assessed objective and subjective image quality and compared radiation dose parameters.

RESULTS

Radiation dose was comparable for children 5 years old and younger, and it was moderately decreased for older children when using spectral filtration (P=0.006). Effective tube current increased significantly (P=0.0001) with spectral filtration, up to a factor of 10. Signal-to-noise ratio and image noise were similar for both examination techniques (P≥0.06). Subjective image quality showed no significant differences (P≥0.2).

CONCLUSION

Using 100-kVp spectral filtration chest CT in children by means of a tube-based tin-filter on a third-generation dual-source CT scanner increases effective tube current up to a factor of 10 to provide similar image quality at equivalent dose compared to standard single-source CT without spectral filtration.

Radiation dose levels in pediatric chest CT: experience in 499 children evaluated with dual-source single-energy CT

BACKGROUND

The availability of dual-source technology has introduced the possibility of scanning children at lower kVp with a high-pitch mode, combining high-speed data acquisition and high temporal resolution.

OBJECTIVE

To establish the radiation dose levels of dual-source, single-energy chest CT examinations in children.

MATERIALS AND METHODS

We retrospectively recorded the dose-length product (DLP) of 499 consecutive examinations obtained in children <50 kg, divided into five weight groups: group 1 (<10 kg, n = 129); group 2 (10-20 kg, n = 176); group 3 (20-30 kg, n = 99), group 4 (30-40 kg, n = 58) and group 5 (40-49 kg, n = 37). All CT examinations were performed with high temporal resolution (75 ms), a high-pitch mode and a weight-adapted selection of the milliamperage.

RESULTS

CT examinations were obtained at 80 kVp with a milliamperage ranging between 40 mAs and 90 mAs, and a pitch of 2.0 (n = 162; 32.5%) or 3.0 (n = 337; 67.5%). The mean duration of data acquisition was 522.8 ± 192.0 ms (interquartile range 390 to 610; median 490). In the study population, the mean CT dose index volume (CTDIvol₃₂) was 0.83 mGy (standard deviation [SD] 0.20 mGy; interquartile range 0.72 to 0.94; median 0.78); the mean DLP₃₂ was 21.4 mGy.cm (SD 9.1 mGy.cm; interquartile range 15 to 25; median 19.0); and the mean size-specific dose estimate (SSDE) was 1.7 mGy (SD 0.4 mGy; interquartile range 1.5 to 1.9; median 1.7). The DLP₃₂, CTDI_vol32 and SSDE were found to be statistically significant in the five weight categories (P < 0.0001).

CONCLUSION

This study establishes the radiation dose levels for dual-source, single-kVp chest CT from a single center. In the five weight categories, the median values varied 15-37 mGy.cm for the DLP₃₂, 0.78-1.25 mGy for the CTDI_vol32 and 1.6-2.1 mGy for the SSDE.

Pediatric 320-row cardiac computed tomography using electrocardiogram-gated model-based full iterative reconstruction

BACKGROUND

Full iterative reconstruction algorithm is available, but its diagnostic quality in pediatric cardiac CT is unknown.

OBJECTIVE

To compare the imaging quality of two algorithms, full and hybrid iterative reconstruction, in pediatric cardiac CT.

MATERIALS AND METHODS

We included 49 children with congenital cardiac anomalies who underwent cardiac CT. We compared quality of images reconstructed using the two algorithms (full and hybrid iterative reconstruction) based on a 3-point scale for the delineation of the following anatomical structures: atrial septum, ventricular septum, right atrium, right ventricle, left atrium, left ventricle, main pulmonary artery, ascending aorta, aortic arch including the patent ductus arteriosus, descending aorta, right coronary artery and left main trunk. We evaluated beam-hardening artifacts from contrast-enhancement material using a 3-point scale, and we evaluated the overall image quality using a 5-point scale. We also compared image noise, signal-to-noise ratio and contrast-to-noise ratio between the algorithms.

RESULTS

The overall image quality was significantly higher with full iterative reconstruction than with hybrid iterative reconstruction (3.67±0.79 vs. 3.31±0.89, P=0.0072). The evaluation scores for most of the gross structures were higher with full iterative reconstruction than with hybrid iterative reconstruction. There was no significant difference between full and hybrid iterative reconstruction for the presence of beam-hardening artifacts. Image noise was significantly lower in full iterative reconstruction, while signal-to-noise ratio and contrast-to-noise ratio were significantly higher in full iterative reconstruction.

CONCLUSION

The diagnostic quality was superior in images with cardiac CT reconstructed with electrocardiogram-gated full iterative reconstruction.