Initial clinical evaluation of stationary digital chest tomosynthesis in adult patients with cystic fibrosis

The correlation between point-of-care ultrasound and digital tomosynthesis when used with suspected COVID-19 pneumonia patients in primary care

Background

The use of lung ultrasound (LU) with COVID-19 pneumonia patients should be validated in the field of primary care (PC). Our study aims to evaluate the correlation between LU and radiographic imaging in PC patients with suspected COVID-19 pneumonia.

Methods

This observational, prospective and multicentre study was carried out with patients from a PC health area whose tests for COVID-19 and suspected pneumonia had been positive and who then underwent LU and a digital tomosynthesis (DT). Four PC physicians obtained data regarding the patients’ symptoms, examination, medical history and ultrasound data for 12 lung fields: the total amount of B lines (zero to four per field), the irregularity of the pleural line, subpleural consolidation, lung consolidation and pleural effusion. These data were subsequently correlated with the presence of pneumonia by means of DT, the need for hospital admission and a consultation in the hospital emergency department in the following 15 days.

Results

The study was carried out between November 2020 and January 2021 with 70 patients (40 of whom had pneumonia, confirmed by means of DT). Those with pneumonia were older, had a higher proportion of arterial hypertension and lower oxygen saturation (sO2). The number of B lines was higher in patients with pneumonia (16.53 vs. 4.3, p < 0.001). The area under the curve for LU was 0.87 (95% CI 0.78–0.96, p < 0.001), and when establishing a cut-off point of six B lines or more, the sensitivity was 0.875 (95% CI 0.77–0.98, p < 0.05), the specificity was 0.833 (95% CI 0.692–0.975, p < 0.05), the positive-likelihood ratio was 5.25 (95% CI 2.34–11.79, p < 0.05) and the negative-likelihood ratio was 0.15 (95% CI 0.07–0.34, p < 0.05). An age of ≥ 55 and a higher number of B lines were associated with admission. Patients who required admission (n = 7) met at least one of the following criteria: ≥ 55 years of age, sO2 ≤ 95%, presence of at least one subpleural consolidation or ≥ 21 B lines.

Conclusions

LU has great sensitivity and specificity for the diagnosis of COVID-19 pneumonia in PC. Clinical ultrasound findings, along with age and saturation, could, therefore, improve decision-making in this field.

The evolving role of radiological imaging in cystic fibrosis

PURPOSE OF REVIEW

Radiological imaging has a crucial role in pulmonary evaluation in cystic fibrosis (CF), having been shown to be more sensitive than pulmonary function testing at detecting structural lung changes. The present review summarizes the latest published information on established and evolving pulmonary imaging techniques for assessing people with this potentially life-limiting disorder.

RECENT FINDINGS

Chest computed tomography (CT) has taken over the predominant role of chest radiography in many centres for the initial assessment and surveillance of CF lung disease. However, several emerging techniques offer a promising means of pulmonary imaging using less ionizing radiation. This is of particular importance given these patients tend to require repeated imaging throughout their lives from a young age. Such techniques include ultra-low-dose CT, tomosynthesis, dynamic radiography and magnetic resonance imaging. In addition, deep-learning algorithms are anticipated to improve diagnostic accuracy.

SUMMARY

The recent introduction of triple-combination CF transmembrane regulator therapy has put further emphasis on the need for sensitive methods of monitoring treatment response to allow for early adaptation of treatment regimens in order to limit irreversible lung damage. Further research is needed to establish how emerging imaging techniques can contribute to this safely and effectively.

QUANTIFICATION OF PULMONARY PATHOLOGY IN CYSTIC FIBROSIS-COMPARISON BETWEEN DIGITAL CHEST TOMOSYNTHESIS AND COMPUTED TOMOGRAPHY

PURPOSE

Digital tomosynthesis (DTS) is currently undergoing validation for potential clinical implications. The aim of this study was to investigate the potential for DTS as a low-dose alternative to computed tomography (CT) in imaging of pulmonary pathology in patients with cystic fibrosis (CF).

METHODS

DTS and CT were performed as part of the routine triannual follow-up in 31 CF patients. Extent of disease was quantified according to modality-specific scoring systems. Statistical analysis included Spearman's rank correlation coefficient (r) and Krippendorff's alpha (α).

MAJOR FINDINGS

The median effective dose was 0.14 for DTS and 2.68 for CT. Intermodality correlation was very strong for total score and the subscores regarding bronchiectasis and bronchial wall-thickening (r = 0.82-0.91, P < 0.01). Interobserver reliability was high for total score, bronchiectasis and mucus plugging (α = 0.83-0.93) in DTS.

CONCLUSION

Chest tomosynthesis could be a low-dose alternative to CT in quantitative estimation of structural lung disease in CF.

Evaluation of carbon nanotube x-ray source array for stationary head computed tomography

PURPOSE

Stationary computed tomography (s-CT) conceptually offers several advantages over existing rotating gantry-based CT. Over the last 40 yr, s-CT has been investigated using different technological approaches. We are developing a s-CT system specifically for head/brain imaging using carbon nanotube (CNT)-based field emission x-ray source array technology. The noncircular geometry requires different assessment approaches as compared to circular geometries. The purpose of the present study is to investigate whether the CNT source array meets the requirements for stationary head CT (s-HCT).

METHODS

Multiple prototype CNT x-ray source arrays were manufactured based on the system requirements obtained from simulation. Source characterization was performed using a benchtop setup consisting of an x-ray source array with 45 distributed focal spots, each operating at 120 kVp, and an electronic control system (ECS) for high speed control of the x-ray output from individual focal spots. Due to the forward-angled geometry of the linear anode, the projected focal spot shape is expected to vary at wide angle views. A pinhole method was implemented to determine the effective focal spot size (FSS) in the imaging plane at a range of angular viewpoints with a flat panel detector. The output spectrum and half value layer (HVL) were also evaluated for a range of viewing angles to characterize the beam quality across the fan-beam. Dosimetry was performed on a simulated scan to evaluate total exposure.

RESULTS

The prototype CNT x-ray source array demonstrated adequate specifications for a s-HCT imaging machine. The source array was operated at 120 kVp with long-term stability over a full year of regular laboratory use. Multiple cathode current measurements were used to confirm submicrosecond accuracy with regards to exposure time and subsequently dose control. All 45 focal spots were measured with an average value of 1.26 (±0.04) mm × 1.21 (±0.03) mm (equivalent to IEC 1,0). The x-ray spectrum was found to be appropriately filtered based on sources used in existing rotary CT systems. A stable and reliable output of 0.04 mAs per emitter and a resulting dose of 0.015 mGy per projection were observed over several months of rigorous phantom imaging. Dose per projection was regulated by the ECS and measured with ±0.5% tolerance.

CONCLUSIONS

The CNT x-ray source array was found to meet the requirements for the proposed stationary head CT scanner, with regard to FSS, beam quality, and dose precision. The remaining challenges are related to the overall system design of a nonrotating CT scanner with distributed sources. The next phase of the project will incorporate multiple CNT source arrays with multirow detectors in a proof-of-concept study and analysis of a fully functional s-HCT system.

Novel imaging techniques for cystic fibrosis lung disease

With an increasing number of patients with cystic fibrosis (CF) receiving highly effective CFTR (cystic fibrosis transmembrane regulator protein) modulator therapy, particularly at a young age, there is an increasing need to identify imaging tools that can detect and regionally visualize mild CF lung disease and subtle changes in disease state. In this review, we discuss the latest developments in imaging modalities for both structural and functional imaging of the lung available to CF clinicians and researchers, from the widely available, clinically utilized imaging methods for assessing CF lung disease-chest radiography and computed tomography-to newer techniques poised to become the next phase of clinical tools-structural/functional proton and hyperpolarized gas magnetic resonance imaging (MRI). Finally, we provide a brief discussion of several newer lung imaging techniques that are currently available only in selected research settings, including chest tomosynthesis, and fluorinated gas MRI. We provide an update on the clinical and/or research status of each technique, with a focus on sensitivity, early disease detection, and possibilities for monitoring treatment efficacy.