Comparison of Image Quality and Radiation Dose between High-Pitch Mode and Low-Pitch Mode Spiral Chest CT in Small Uncooperative Children: The Effect of Respiratory Rate

Multi-institutional Protocol Guidance for Pediatric Photon-counting CT

Performing CT in children comes with unique challenges such as greater degrees of patient motion, smaller and densely packed anatomy, and potential risks of radiation exposure. The technical advancements of photon-counting detector (PCD) CT enable decreased radiation dose and noise, as well as increased spatial and contrast resolution across all ages, compared with conventional energy-integrating detector CT. It is therefore valuable to review the relevant technical aspects and principles specific to protocol development on the new PCD CT platform to realize the potential benefits for this population. The purpose of this article, based on multi-institutional clinical and research experience from pediatric radiologists and medical physicists, is to provide protocol guidance for use of PCD CT in the imaging of pediatric patients.

Axial or Helical? CT imaging of the thorax for dyspnoea patients with free-breathing using 16 cm wide-detector CT

AIM

To compare image quality and radiation dose between fast-helical mode (FHM) and two-axial mode (TAM) in chest computed tomography (CT) with 16 cm wide-detector for emergency patients with dyspnoea.

MATERIALS AND METHODS

Ninety-six emergency chest CT patients who cannot comply with breathing instructions were prospectively divided randomly into two groups: the FHM group (n=48, helical scan with 80 mm collimation and pitch 0.992:1), the TAM group (n=48, two axial scans with 160 mm collimation). Both groups used 0.28 seconds rotation speed and automatic tube current modulation. All scans were performed in free breathing. CT value, image noise, and signal-to-noise ratio (SNR) were measured on the descending thoracic aorta, lung parenchyma, and paraspinal muscle at the carina level. Two radiologists assessed images for subjective image quality, motion artefacts and diagnostic confidence. The volume CT dose index and dose-length product (DLP) were evaluated and effective dose (ED) was calculated.

RESULTS

The TAM group required less exposure time than the FHM group (0.56 versus 1.14 seconds, p<0.001), reduced the frequency of motion artefacts caused by the diaphragm and heart by 50% and provided higher diagnostic confidence score (3.83 versus 3.58, p<0.05). TAM resulted in 24% lower DLP (96.76±31.58 versus 126.99±33.37 mGy·cm) and ED (1.36±0.44 versus 1.78±0.47 mSv) than FHM (p<0.001), but there was no difference in the CT value, image noise, and SNR between the two groups (p>0.05).

CONCLUSIONS

TAM with 16 cm detector coverage further reduces the exposure time in chest CT for dyspnoea patients and ensures good image quality with 24% radiation dose reduction, compared with fast-helical chest CT with 80 mm collimation.

Chest CT features of coronavirus disease 2019 (COVID-19) pneumonia: key points for radiologists

COVID-19 is an emerging infection caused by a novel coronavirus that is moving so rapidly that on 30 January 2020 the World Health Organization declared the outbreak a Public Health Emergency of International Concern and on 11 March 2020 as a pandemic. An early diagnosis of COVID-19 is crucial for disease treatment and control of the disease spread. Real-time reverse-transcription polymerase chain reaction (RT-PCR) demonstrated a low sensibility; therefore chest computed tomography (CT) plays a pivotal role not only in the early detection and diagnosis, especially for false negative RT-PCR tests, but also in monitoring the clinical course and in evaluating the disease severity. This paper reports the CT findings with some hints on the temporal changes over the course of the disease: the CT hallmarks of COVID-19 are bilateral distribution of ground glass opacities with or without consolidation in the posterior and peripheral lung, but the predominant findings in later phases include consolidations, linear opacities, “crazy-paving” pattern, “reversed halo” sign and vascular enlargement. The CT findings of COVID-19 overlap with the CT findings of other diseases, in particular the viral pneumonia including influenza viruses, parainfluenza virus, adenovirus, respiratory syncytial virus, rhinovirus, human metapneumovirus, etc. There are differences as well as similarities in the CT features of COVID-19 compared with those of the severe acute respiratory syndrome. The aim of this article is to review the typical and atypical CT findings in COVID-19 patients in order to help radiologists and clinicians to become more familiar with the disease.

Initial clinical experience with high-pitch dual-source CT as a rapid technique for thoraco-abdominal evaluation in awake infants and young children

AIM

To evaluate dual-source high-pitch computed tomography (HPCT) imaging of the chest and abdomen as a rapid scanning technique to obtain diagnostic-quality imaging evaluation of infants and young children without sedation.

MATERIALS AND METHODS

Fifty-three paediatric patients (age 24.1±2 months) who underwent chest or abdomen HPCT (≥1.5) and standard pitch CT (SPCT, <1.5) on a dual-source 128-row multidetector CT system were included in the study. Image quality assessment was performed by two paediatric radiologists for diagnostic confidence, image artefacts, and image noise. Objective image noise was measured.

RESULTS

Most of the CT examinations were performed in children who were >1 year old (n=15 and n=20) followed by ≤1 year old (n=8 and n=10) in SPCT and HPCT, respectively. The mean radiation dose (SSDE) from HPCT was 1.96±1 mGy compared to 2.2±1 mGy for SPCT (p=0.3). No major artefacts were reported and overall image quality of all HPCT examinations was acceptable diagnostically. In addition, objective image noise values were not significantly different between HPCT compared with SPCT (11±3 versus 11±5, p=0.7).

CONCLUSION

Ultra-fast, HPCT can be performed without the need for sedation as a potential alternative to anaesthetised magnetic resonance imaging in infants and young children.

Trends in radiation dose and image quality for pediatric patients with a multidetector CT and a third-generation dual-source dual-energy CT

AIM

To provide an overview on dose reduction and image quality after the installation of a third-generation dual-source CT (dsCT) in a Pediatric Radiology Department.

MATERIALS AND METHODS

We included pediatric patients (< 20 years old) undergoing CT for oncological staging (neck, chest and abdomen) or low-dose chest CT for lung diseases. Each of these two groups were further divided in two age groups (≤ or > 10 years old) including patients scanned in the same period of two consecutive years, in 2017 with a 16-row LightSpeed CT (GE Healthcare) or in 2018 with a Somatom Force dsCT (Siemens Healthineers). Technical parameters such as kVp, mAs, slice thickness, exposure times and dose indicators were retrieved and compared. Image quality was evaluated in consensus by two radiologists on a five-point semiquantitative scale. Nonparametric tests were used.

RESULTS

In oncological patients, significantly lower kVp and tube current with better image quality were achieved with the dsCT. Radiation dose (total DLP) was 5-6 times lower with dsCT, thanks also to virtual non-contrast images. In low-dose chest CT, the frequent use of tin filter required higher tube current; a total DLP 3 times lower was achieved with dsCT in patients ≤ 10 years old. The image quality was better with the dsCT in low-dose chest CT protocols.

CONCLUSION

The third-generation dsCT provides high-quality images with reduced motion artifacts at lower dose.

Radiation exposure during videofluoroscopic swallowing studies in young children

OBJECTIVES

Swallowing difficulties are best assessed by videofluoroscopic swallowing studies (VFSS). However, limiting radiation exposure is important, especially in young children. The purpose was to evaluate radiation dose in young children during VFSS, and to investigate factors associated with it.

METHODS

Children with swallowing difficulty who underwent VFSS from February 2012 to July 2014 were recruited. Dose area product (DAP) and screening time were offered by the fluoroscopy machine, and effective dose was calculated from the DAP using a conversion coefficient published by the National Radiological Protection Board (NRPB-R262). The age, gender, height, weight, body mass index (BMI), body surface area (BSA), underlying disease of the subject children, and results of VFSS were investigated.

RESULTS

In 89 children (mean age 1.57 ± 2.17, 55 boys and 34 girls), mean effective dose was 0.29 ± 0.20 mSv, mean DAP was 2.41 ± 1.65 Gy cm², and mean screening time was 2.24 ± 0.99 min. The effective dose correlated with the screening time (r = 0.598, p < 0.001), age (r = 0.210, p = 0.049), height (r = 0.521, p < 0.001), weight (r = 0.461, p < 0.001), and BSA (r = 0.493, p < 0.001). There was no such correlation with gender, BMI, underlying disease, or the results of VFSS.

CONCLUSIONS

The effective dose during VFSS (0.29 mSv) in young children, which is affected by screening time, age, and body size, is considerably lower than the pediatric radiation exposure limit of 1 mSv per year. However more than 4 VFSS annually would exceed this limit. Our findings will help physicians to reduce the radiation exposure and provide a useful references for future pediatric VFSS guidelines.

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 .

Ultrafast pediatric chest computed tomography: comparison of free-breathing vs. breath-hold imaging with and without anesthesia in young children

BACKGROUND

General anesthesia (GA) or sedation has been used to obtain good-quality motion-free breath-hold chest CT scans in young children; however pulmonary atelectasis is a common and problematic accompaniment that can confound diagnostic utility. Dual-source multidetector CT permits ultrafast high-pitch sub-second examinations, minimizing motion artifact and potentially eliminating the need for a breath-hold.

OBJECTIVE

The purpose of this study was to evaluate the feasibility of free-breathing ultrafast pediatric chest CT without GA and to compare it with breath-hold and non-breath-hold CT with GA.

MATERIALS AND METHODS

Young (≤3 years old) pediatric outpatients scheduled for chest CT under GA were recruited into the study and scanned using one of three protocols: GA with intubation, lung recruitment and breath-hold; GA without breath-hold; and free-breathing CT without anesthesia. In all three protocols an ultrafast high-pitch CT technique was used. We evaluated CT images for overall image quality, presence of atelectasis and motion artifacts.

RESULTS

We included 101 scans in the study. However the GA non-breath-hold technique was discontinued after 15 scans, when it became clear that atelectasis was a major issue despite diligent attempts to mitigate it. This technique was therefore not included in statistical evaluation (86 remaining patients). Overall image quality was higher (P=0.001) and motion artifacts were fewer (P<.001) for scans using the GA with intubation and recruitment technique compared to scans in the non-GA free-breathing group. However no significant differences were observed regarding the presence of atelectasis between these groups.

CONCLUSION

We demonstrated that although overall image quality was best and motion artifact least with a GA-breath-hold intubation and recruitment technique, free-breathing ultrafast pediatric chest CT without anesthesia provides sufficient image quality for diagnostic purposes and can be successfully performed both without and with contrast agent in young infants.

Image quality and radiation dose of ECG-triggered High-Pitch Dual-Source cardiac computed tomography angiography in children for the evaluation of central vascular stents

Assess image quality and radiation dose of ECG-triggered High-Pitch Dual-Source CTA for the evaluation central vascular stents in children. We included all children ≤ 21 years old with one or more central vascular stents and available prospective ECG-triggered High-Pitch Dual-Source CTA performed at our institution between January 2015 and August 2017. Demographic and scanner information was retrieved. Two board-certified pediatric radiologists blinded to the clinical data, independently reviewed and scored each case using a four-point quality score. Scores 1, 2 and 3 were considered of diagnostic image quality. Inter-observer agreement and non-parametric test were used. 18 patients (10 girls, 8 boys) with a mean age of 9.47 ± 7.38 years (mean ± SD) met inclusion criteria. Thirty-two central vascular stents were evaluated. Mean quality score was 2.07 ± 0.94 with 12.5% (4/32) of the cases classified as unevaluable. Interobserver agreement was excellent (k = 0.86). There is no significant difference between quality score and stent location (p = 0.07). There is a significant difference with stent material as all non-diagnostic scores were only seen in covered stents made of platinum-iridium (p < 0.001). There was no association between image quality and age, height, weight, BSA, heart rate, radiation dose or stent lumen size (p > 0.05). ECG-triggered high-pitch spiral DS-CTA offers appropriate image quality for assessment of central vascular stents in children.

Depiction of the native coronary arteries during ECG-triggered High-Pitch Dual-Source Coronary Computed Tomography Angiography in children: Determinants of image quality

OBJECTIVE

Assess the image quality of ECG-triggered High-Pitch Dual-Source CTA for the evaluation of native coronaries in children.

MATERIALS AND METHODS

Between August 2014 and September 2017, 45 children with morphologically normal cardiac chambers had cardiac prospective ECG-triggered High-Pitch Dual-Source CTA. Two pediatric radiologists blinded to clinical data, independently reviewed each case. The coronary arteries were evaluated using a four-point scale quality score according to the coronary segment. Attenuation, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured using values from the air, inter-ventricular septum and ascending aorta at the level of the sinuses of Valsalva.

RESULTS

225 coronary segments were assessed showed a mean score of 2.40 ± 0.73, 94.2% had diagnostic image quality. The best and worst average quality were seen in segment 5 and 2, respectively. Inter-observer agreement was moderate for all segments except for segment 1, which was excellent. Worse quality scores were significantly associated with younger patients and low body mass index as well as with higher heart rates in all segments. The mean observed heart rate and BSA in patients with diagnostic image quality were below 77 bpm and over 1.4 m² respectively. There is no significant association between attenuation, SNR and CNR with image quality.

CONCLUSIONS

Prospective ECG-triggered High-Pitch Dual-Source Computed Tomography Angiography achieves consistent and diagnostic image quality for coronary artery assessment at a low effective dose in pediatric patients.

High-pitch dual-source paranasal sinus CT in agitated patients with maxillofacial trauma: analysis of image quality, motion artifacts, and dose aspects

Background Image quality benefits from high-pitch scanning in agitated patients by reducing acquisition time. Purpose To compare image quality and exposure parameters in patients with maxillofacial trauma on second- and third-generation dual-source computed tomography (DSCT). Material and Methods Four groups were compared. Group 1 was examined on second-generation DSCT (120 kV/50 mAs, pitch 3.0). The other three groups were examined on third-generation DSCT. Group 2 was scanned with 120 kV/50 mAs, pitch 2.2. Automated exposure control (AEC) was used in group 3 and group 4 with pitch factors of 2.2 and 3.0, respectively. Images of third-generation DSCT were reconstructed with iterative reconstruction (IR), of second-generation DSCT with filtered back-projection. CTDIvol, acquisition time, and image quality were compared. Results Thirty patients were included in each group. Average CTDIvol (2.76 ± 0.00 mGy, 2.66 ± 0.00 mGy, 0.74 ± 0.23 mGy, and 0.75 ± 0.17 mGy) was significantly lower on third-generation DSCT with AEC ( P < 0.001). Subjective image quality was rated worst in group 4 due to strong high-pitch artifacts, while in the remaining three groups it was rated good or very good with good inter-observer agreement (k > 0.64). Average acquisition time was significantly shorter with third-generation DSCT (0.47 s, 0.36 s, 0.38 s, 0.30 s; P < 0.001). Conclusion Third-generation DSCT yields faster acquisition times and substantial dose reduction with AEC. A pitch of 2.2 should be preferred, as it results in fewer artifacts. If AEC is used, latest IR ensures that diagnostic image quality is guaranteed.

Evaluating the effect of increased pitch, iterative reconstruction and dual source CT on dose reduction and image quality

Objective:

To compare radiation dose and image quality of thoracoabdominal scans obtained with a high-pitch protocol (pitch 3.2) and iterative reconstruction (Sinogram Affirmed Iterative Reconstruction) in comparison to standard pitch reconstructed with filtered back projection (FBP) using dual source CT.

Methods:

114 CT scans (Somatom Definition Flash, Siemens Healthineers, Erlangen, Germany), 39 thoracic scans, 54 thoracoabdominal scans and 21 abdominal scans were performed. Analysis of three protocols was undertaken; pitch of 1 reconstructed with FBP, pitch of 3.2 reconstructed with SAFIRE, pitch of 3.2 with stellar detectors reconstructed with SAFIRE. Objective and subjective image analysis were performed. Dose differences of the protocols used were compared.

Results:

Dose was reduced when comparing scans with a pitch of 1 reconstructed with FBP to high-pitch scans with a pitch of 3.2 reconstructed with SAFIRE with a reduction of volume CT dose index of 75% for thoracic scans, 64% for thoracoabdominal scans and 67% for abdominal scans. There was a further reduction after the implementation of stellar detectors reflected in a reduction of 36% of the dose–length product for thoracic scans. This was not at the detriment of image quality, contrast-to-noise ratio, signal-to-noise ratio and the qualitative image analysis revealed a superior image quality in the high-pitch protocols.

Conclusion:

The combination of a high pitch protocol with iterative reconstruction allows significant dose reduction in routine chest and abdominal scans whilst maintaining or improving diagnostic image quality, with a further reduction in thoracic scans with stellar detectors.

Advances in knowledge:

High pitch imaging with iterative reconstruction is a tool that can be used to reduce dose without sacrificing image quality.

Free-breathing high-pitch 80kVp dual-source computed tomography of the pediatric chest: Image quality, presence of motion artifacts and radiation dose

OBJECTIVES

To investigate image quality, presence of motion artifacts and effects on radiation dose of 80kVp high-pitch dual-source CT (DSCT) in combination with an advanced modeled iterative reconstruction algorithm (ADMIRE) of the pediatric chest compared to single-source CT (SSCT).

MATERIALS AND METHODS

The study was approved by the institutional review board. Eighty-seven consecutive pediatric patients (mean age 9.1±4.9years) received either free-breathing high-pitch (pitch 3.2) chest 192-slice DSCT (group 1, n=31) or standard-pitch (pitch 1.2) 128-slice SSCT (group 2, n=56) with breathing-instructions by random assignment. Tube settings were similar in both groups with 80 kVp and 74 ref. mAs. Images were reconstructed using FBP for both groups. Additionally, ADMIRE was used in group 1. Effective thorax diameter, image noise, and signal-to-noise ratio (SNR) of the pectoralis major muscle and the thoracic aorta were calculated. Motion artifacts were measured as doubling boarders of the diaphragm and the heart. Images were rated by two blinded readers for overall image quality and presence of motion artifacts on 5-point-scales. Size specific dose estimates (SSDE, mGy) and effective dose (ED, mSv) were calculated.

RESULTS

Age and effective thorax diameter showed no statistically significant differences in both groups. Image noise and SNR were comparable (p>0.64) for SSCT and DSCT with ADMIRE, while DSCT with FBP showed inferior results (p<0.01). Motion artifacts were reduced significantly (p=0.001) with DSCT. DSCT with ADMIRE showed the highest overall IQ (p<0.0001). Radiation dose was lower for DSCT compared to SSCT (median SSDE: 0.82mGy vs. 0.92mGy, p<0.02; median ED: 0.4 mSv vs. 0.48mSv, p=0.02).

CONCLUSIONS

High-pitch 80kVp chest DSCT in combination with ADMIRE reduces motion artifacts and increases image quality while lowering radiation exposure in free-breathing pediatric patients without sedation.