Model-based iterative reconstruction in ultra-low-dose pediatric chest CT: comparison with adaptive statistical iterative reconstruction

Image quality in CT thorax: effect of altering reconstruction algorithm and tube load

Non-linear properties of iterative reconstruction (IR) algorithms can alter image texture. We evaluated the effect of a model-based IR algorithm (advanced modelled iterative reconstruction; ADMIRE) and dose on computed tomography thorax image quality. Dual-source scanner data were acquired at 20, 45 and 65 reference mAs in 20 patients. Images reconstructed with filtered back projection (FBP) and ADMIRE Strengths 3-5 were assessed independently by six radiologists and analysed using an ordinal logistic regression model. For all image criteria studied, the effects of tube load 20 mAs and all ADMIRE strengths were significant (p < 0.001) when compared to reference categories 65 mAs and FBP. Increase in tube load from 45 to 65 mAs showed image quality improvement in three of six criteria. Replacing FBP with ADMIRE significantly improves perceived image quality for all criteria studied, potentially permitting a dose reduction of almost 70% without loss in image quality.

Outpatient Respiratory Management of Infants, Children, and Adolescents with Post-Prematurity Respiratory Disease: An Official American Thoracic Society Clinical Practice Guideline

Background: Premature birth affects millions of neonates each year, placing them at risk for respiratory disease due to prematurity. Bronchopulmonary dysplasia is the most common chronic lung disease of infancy, but recent data suggest that even premature infants who do not meet the strict definition of bronchopulmonary dysplasia can develop adverse pulmonary outcomes later in life. This post-prematurity respiratory disease (PPRD) manifests as chronic respiratory symptoms, including cough, recurrent wheezing, exercise limitation, and reduced pulmonary function. This document provides an evidence-based clinical practice guideline on the outpatient management of infants, children, and adolescents with PPRD. Methods: A multidisciplinary panel of experts posed questions regarding the outpatient management of PPRD. We conducted a systematic review of the relevant literature. The Grading of Recommendations, Assessment, Development, and Evaluation approach was used to rate the quality of evidence and the strength of the clinical recommendations. Results: The panel members considered the strength of each recommendation and evaluated the benefits and risks of applying the intervention. In formulating the recommendations, the panel considered patient and caregiver values, the cost of care, and feasibility. Recommendations were developed for or against three common medical therapies and four diagnostic evaluations in the context of the outpatient management of PPRD. Conclusions: The panel developed recommendations for the outpatient management of patients with PPRD on the basis of limited evidence and expert opinion. Important areas for future research were identified.

Modern pulmonary imaging of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a complex and serious cardiopulmonary morbidity in infants who are born preterm. Despite advances in clinical care, BPD remains a significant source of morbidity and mortality, due in large part to the increased survival of extremely preterm infants. There are few strong early prognostic indicators of BPD or its later outcomes, and evidence for the usage and timing of various interventions is minimal. As a result, clinical management is often imprecise. In this review, we highlight cutting-edge methods and findings from recent pulmonary imaging research that have high translational value. Further, we discuss the potential role that various radiological modalities may play in early risk stratification for development of BPD and in guiding treatment strategies of BPD when employed in varying severities and time-points throughout the neonatal disease course.

Recent Imaging Advancements for Lung Metastases in Children with Sarcoma

In children and adolescents affected by musculoskeletal sarcomas (both soft tissue and bone sarcomas), the presence of lung metastases is a frequent complication, that should be known since the patient's prognosis, as management, and treatment depend on it. During the staging phase, the detection of lung metastases should be sensitive and specific, and it should be carried out by minimizing the radiation exposure. To deal with this problem, imaging has reached important goals in recent years, thanks to the development of cone-beam CT or low-dose computed tomography, with some new iterative reconstruction methods, such as Veo and ASIR. Imaging is also fundamental for the possibility to perform lung biopsies under CT guidance, with less morbidity, less time-consumption, and shorter recovery time, compared to surgical biopsies.Moreover, important results have also been demonstrated in the treatment of lung metastases, due to the improvement of new mini-invasive image-guided percutaneous thermal ablation procedures, which proved to be safe and effective also in young patients.

Radiologic Assessment of Osteosarcoma Lung Metastases: State of the Art and Recent Advances

The lung is the most frequent site of osteosarcoma (OS) metastases, which are a critical point in defining a patient’s prognosis. Chest computed tomography (CT) represents the gold standard for the detection of lung metastases even if its sensitivity widely ranges in the literature since lung localizations are often atypical. ESMO guidelines represent one of the major references for the follow-up program of OS patients. The development of new reconstruction techniques, such as the iterative method and the deep learning-based image reconstruction (DLIR), has led to a significant reduction of the radiation dose with the low-dose CT. The improvement of these techniques has great importance considering the young-onset of the disease and the strict chest surveillance during follow-up programs. The use of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT is still controversial, while volume doubling time (VDT) and computer-aided diagnosis (CAD) systems are recent diagnostic tools that could support radiologists for lung nodules evaluation. Their use, well-established for other malignancies, needs to be further evaluated, focusing on OS patients.

A feasibility study of pulmonary nodule detection by ultralow-dose CT with adaptive statistical iterative reconstruction-V technique

PURPOSE

To evaluate the clinical value of ultralow-dose CT (ULDCT) with adaptive statistical iterative reconstruction-V (ASiR-V) in the detection of pulmonary nodules in a Chinese population.

METHOD

One hundred eighty-eight patients (16.41 ≤ BMI ≤ 29.87 kg/m²) with pulmonary nodules detected on low-dose chest CT (LDCT) underwent local ULDCT at the center of the chosen nodule with a scan length of 3 cm. LDCT was performed using the Assist kV (120/100 kV)/Smart mA mode and at 120 kV/2.8 mAs for ULDCT. After scanning, CT images were reconstructed with ASiR-V 50%. For both scans, nodule diameters were measured and reference standards were established for the presence and types of lung nodules found on LDCT. The sensitivity of ULDCT was compared against the standard, and logistic regression analysis was used to determine the independent predictors for nodule detection.

RESULTS

Compared with LDCT (0.93 ± 0.32 mSv), a 89.7% dose decrease was seen with ULDCT, for which the calculated effective dose was 0.096 ± 0.006 mSv (P < 0.001). LDCT showed 188 nodules, including 123 solid and 65 subsolid nodules. The overall sensitivity for nodule detection in ULDCT was 90.4% (170/188), and 98.2% (54/55) for nodules ≥ 6 mm. In multivariate analysis, nodule types and diameters were independent predictors of sensitivity (P < 0.05). However, patients' BMI had no effect on nodule detection (P > 0.05).

CONCLUSIONS

ULDCT can be used in the management of pulmonary nodules for people with BMI ≤ 30 kg/m² at 10% radiation dose of LDCT.

Feasibility study of using one-tenth mSv radiation dose in young children chest CT with 80 kVp and model-based iterative reconstruction

CT has become a routine imaging modality based on its excellent ability of displaying lung structures and diseases. But, how to reduce radiation dose of routine CT examination is a concern for radiologists. Our study aimed to evaluate the feasibility of using 80kVp and a model-based iterative reconstruction (MBIR) algorithm to achieve one-tenth mSv dose chest CT in infants and young children. Thirty-two cases (study group, average age 1.71 ± 1.01 years) underwent non-contrast chest CT examination at low dose with 80 kV, 4mAs and was reconstructed with MBIR (LD-MBIR) and the standard adaptive statistical iterative reconstruction (ASIR) algorithm (LD-ASIR); another group (control group) of 32 children underwent routine-dose chest CT with 100 kV and was reconstructed with ASIR only (RD-ASIR). The subjective and objective image quality of the three groups were measured and statistically compared. The radiation dose for the low dose scan was 0.09 ± 0.02 mSv, 6% of the routine dose. All LD-MBIR images were diagnostically acceptable. Compared with the RD-ASIR images, the LD-MBIR images were similar in noise in the left ventricle, muscles, lung field, on-par in displaying large airways, lung lucency and mediastinum, but were inferior in displaying lung marking, small airways and mediastinum. Thus, MBIR images with low dose in pediatric chest CT can be used in the diagnosis for lung field and air way disorders in infants and young children.

Image quality comparison between model-based iterative reconstruction and adaptive statistical iterative reconstruction chest computed tomography in cystic fibrosis patients

INTRODUCTION

Cystic fibrosis (CF) predominantly affects young adults. Accurate radiological assessment of pulmonary disease is vital for predicting exacerbations, one of the leading causes of morbidity and mortality. We evaluated the image quality of model-based iterative reconstruction (MBIR) ultra-low-dose CT chest (ULD-CT) in CF evaluation.

METHODS

We compared ULD-CT with standard adaptive statistical iterative reconstruction (ASIR) low-dose CT (LD-CT). Subjective assessment of contrast and noise were performed for each study. Background noise, signal to noise ratio (SNR) and contrast to noise ratio (CNR) were calculated and compared between the CT studies. Conspicuity of major structures was assessed. These aspects of image quality were compared to determine whether ULD-CT was superior to LD-CT in assessment of CF.

RESULTS

The ULD-CT achieved median effective dose of 0.073 mSv, comparable to one standard chest radiograph and significantly lower than the median LD-CT dose of 1.22 mSv. ULD-CT had lower subjective contrast and higher subjective noise when compared to LD-CT. Objectively measured background noise was lower in ULD-CT (16.33 HU vs 38.53 HU, P < 0.0001) compared to LD-CT. ULD-CT had higher median CNR (52.65 vs 22.09, P < 0.0001) and SNR in lung (9.08 vs 7.29, P = 0.002) compared to LD-CT. ULD-CT was equal to LD-CT in identification of trachea, bronchi, pleural and pericardium. Interobserver reliability showed agreement of 80-92%.

CONCLUSIONS

The image quality of ULD-CT is similar to LD-CT, at 1/16th the dose. MBIR constructed ULD-CT is an effective imaging modality for CF surveillance, with potential applications in other disease settings.

The impact of adaptive iterative dose reduction 3D on the improvement of shoulder image quality in head and neck CTA

OBJECTIVE

The aim of this study was to determine the impact of adaptive iterative dose reduction 3 D (AIDR3D) on the improvement of shoulder image quality in low-radiographic dose head and neck CT angiography (CTA).

MATERIALS AND METHODS

Ninety patients who underwent CTA examination were randomly divided into two groups, namely group A (n = 45) and B (n = 45). Patients in group A were scanned under 120 kV and 300 mA, with images reconstructed by filtered back projection (FBP), and patients in group B were scanned under 80 kV and auto mA with images reconstructed by AIDR3D. Image quality was accessed by two experienced radiologists. The noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of common carotid artery (CCA) at C7 level, and radiation dosage were compared between the two groups.

RESULTS

The score of CCA in group B was significantly higher than group A (p < 0.05), and there were no significant differences in the scores of carotid sinus and internal carotid artery between the two groups (p > 0.05). The score of intracranial artery in group B was lower than that of group A, however, the image quality in group B can meet the requirement of clinical diagnosis. The noise value of CCA at C7 level in group B was significantly lower than that of group A (p < 0.05). SNR and CNR values of CCA at C7 level in group B were significantly higher than those of group A (p < 0.05). Effective radiation dose in group B was significantly decreased compared with group A (p < 0.05).

CONCLUSION

AIDR3D remarkably improved image quality in low-radiographic dose head and neck CTA over FBP, which made the low-dose CTA images meet the requirement of clinical diagnosis.

Ultra-low dose chest computed tomography: Effect of iterative reconstruction levels on image quality

PURPOSE

To optimize image quality and radiation dose of chest CT with respect to various iterative reconstruction levels, detector collimations and body sizes.

METHOD

A Kyoto Kagaku Lungman with and without extensions was scanned using fixed ultra-low doses of 0.25, 0.49 and 0.74 mGy CTDI_vol, and collimations of 40 and 80 mm. Images were reconstructed with the lung kernel, filtered back projection (FBP) and different ASIR-V levels (10-100%). Contrast-to-noise ratios (CNR) were calculated for 12 mm simulated lesions of different densities in the lung. Image noise, signal-to-noise ratios (SNR), variations in Hounsfield units (HU), noise power spectrum (NPS) and noise texture deviations (NTD) were evaluated for all reconstructions. NTD was calculated as percentage of pixels outside 3 standard deviations to evaluate IR-specific artefacts.

RESULTS

Compared to the FBP, image noise reduced (5-55%) with ASIR-V levels irrespective of dose or collimation. SNR correlated positively (r ≥ 0.925, p ≤ 0.001) with ASIR-V levels at all doses, collimations, and phantom sizes. ASIR-V enhanced the CNR of the lesion with the lowest contrast from 12.7-42.1 (0-100% ASIR-V) at 0.74 mGy with 40 mm collimation. As expected, higher SNR and CNR were measured in the smaller phantom than the bigger phantom. Uniform HU were observed between FBP and ASIR-V levels at all doses, collimations, and phantom sizes. NPS curves left-shifted towards lower frequencies at increasing levels of ASIR-V irrespective of collimation. A positive correlation (r ≥ 0.946, p ≥ 0.001) was observed between NTD and ASIR-V levels. NTD of the FBP was not significantly (p ≤ 0.087) different from NTD of ASIR-V ≤ 20%. The data from the NPS and NTD indicates a blotchier and coarser noise texture at higher levels of ASIR-V, especially at 100% ASIR-V.

CONCLUSION

In comparison with the FBP technique, ASIR-V enhanced quantitative image quality parameters at all ultra-low doses tested. Moreover, the use of ASIR-V showed consistency with body size and collimation. Hence, ASIR-V may be useful for improving image quality of chest CT at ultra-low doses.

Forward-Projected Model-Based Iterative Reconstruction in Screening Low-Dose Chest CT: Comparison With Adaptive Iterative Dose Reduction 3D

OBJECTIVE

The objective of this study is to compare forward-projected model-based iterative reconstruction solution (FIRST), a newer fully iterative CT reconstruction method, with adaptive iterative dose reduction 3D (AIDR 3D) in low-dose screening CT for lung cancer. Differences in image noise, image quality, and pulmonary nodule detection, size, and characterization were specifically evaluated.

MATERIALS AND METHODS

Low-dose chest CT images obtained for 50 consecutive patients between December 2015 and January 2016 were retrospectively reviewed. Images were reconstructed using FIRST and AIDR 3D for both lung and soft-tissue reconstruction. Images were independently reviewed to assess image noise, subjective image quality (with use of a 5-point Likert scale, with 1 denoting far superior image quality; 2, superior quality; 3, equivalent quality; 4, inferior quality; and 5, far inferior quality), pulmonary nodule count, size of the largest pulmonary nodule, and characterization of the largest pulmonary nodule (i.e., solid, part solid, or ground glass).

RESULTS

Across all 50 cases, measured image noise was lower with FIRST than with AIDR 3D (lung window, 44% reduction, 41 ± 7 vs 74 ± 8 HU, respectively; soft-tissue window, 32% reduction, 11 ± 2 vs 16 ± 2 HU, respectively). Readers subjectively rated images obtained with FIRST as comparable to images obtained with AIDR 3D (mean [± SD] Likert score for FIRST vs AIDR 3D, 3.2 ± 0.3 for soft-tissue reconstructions and 3.0 ± 0.3 for lung reconstructions). For each reader, very good agreement regarding nodule count was noted between FIRST and AIDR 3D (interclass correlation coefficient [ICC], 0.83 for reader 1 and 0.78 for reader 2). Excellent agreement regarding nodule size (ICC, 0.99 for reader 1 and 0.99 for reader 2) and characterization of the largest nodule (kappa value, 0.92 for reader 1 and 0.82 for reader 2) also existed.

CONCLUSION

Images reconstructed with FIRST are superior to those reconstructed AIDR 3D with regard to image noise and are equivalent with regard to subjective image quality, pulmonary nodule count, and nodule characterization.

First experiences with model based iterative reconstructions influence on quantitative plaque volume and intensity measurements in coronary computed tomography angiography

PURPOSE

Investigate the influence of adaptive statistical iterative reconstruction (ASIR) and the model-based IR (Veo) reconstruction algorithm in coronary computed tomography angiography (CCTA) images on quantitative measurements in coronary arteries for plaque volumes and intensities.

METHODS

Three patients had three independent dose reduced CCTA performed and reconstructed with 30% ASIR (CTDI_vol at 6.7 mGy), 60% ASIR (CTDI_vol 4.3 mGy) and Veo (CTDI_vol at 1.9 mGy). Coronary plaque analysis was performed for each measured CCTA volumes, plaque burden and intensities.

RESULTS

Plaque volume and plaque burden show a decreasing tendency from ASIR to Veo as median volume for ASIR is 314 mm³ and 337 mm³-252 mm³ for Veo and plaque burden is 42% and 44% for ASIR to 39% for Veo. The lumen and vessel volume decrease slightly from 30% ASIR to 60% ASIR with 498 mm³-391 mm³ for lumen volume and vessel volume from 939 mm³ to 830 mm³. The intensities did not change overall between the different reconstructions for either lumen or plaque.

CONCLUSION

We found a tendency of decreasing plaque volumes and plaque burden but no change in intensities with the use of low dose Veo CCTA (1.9 mGy) compared to dose reduced ASIR CCTA (6.7 mGy & 4.3 mGy), although more studies are warranted.