Elsevier

Radiography

Volume 27, Issue 1, February 2021, Pages 75-80
Radiography

Mobile chest imaging of neonates in incubators: Optimising DR and CR acquisitions

https://doi.org/10.1016/j.radi.2020.06.005Get rights and content

Abstract

Introduction

Neonates are a particularly vulnerable patient group with complex medical needs requiring frequent radiographic examinations. This study aims to compare computed radiography (CR) and direct digital radiography (DDR) portable imaging systems used to acquire chest x-rays for neonates within incubators.

Methods

An anthropomorphic neonatal chest phantom was imaged under controlled conditions using one portable machine but captured using both CR and DDR technology. Other variables explored were: image receptor position (direct and incubator tray), tube current and kV. All other parameters were kept consistent. Contrast-to-noise ratio (CNR) was measured using ImageJ software and dose-area-product (DAP) was recorded. Optimisation score was calculated by dividing CNR with the DAP for each image acquisition.

Results

The images with the highest CNR were those acquired using DDR direct exposures and the images with lowest CNR were those acquired using CR with the image receptor placed within the incubator tray. This is also supported by the optimisation scores which demonstrated DDR direct produced the optimal combination with regards to CNR and radiation dose. The CNR had a mean increase of 50.3% when comparing DDR direct with CR direct respectively. This was also evident when comparing DDR and CR for in-tray acquisitions, with CNR increasing by a mean of 43.5%. A mean increase of 20.4% was seen in CNR when comparing DDR tray exposures to CR direct.

Conclusion

DDR direct produced images of highest CNR, with incubator tray reducing CNR for both CR and DDR. However, DDR tray still had better image quality compared to CR direct.

Implications for practice

Where possible, DDR should be the imaging system of choice for portable examinations on neonates owing to its superior image quality at lower radiation dose.

Introduction

To ensure radiographic practice follows the principles of radiation dose protection, it is necessary to perform dose optimisation studies to find and ensure lowest radiation dose whilst maintaining images of diagnostic quality.1 The need for optimisation is even more essential when imaging neonates due to their growth and quickly dividing cells, placing them at greater risk of cellular mutations and developing cancers in later life.2 Neonatal radiography is a vital resource in diagnosing and treating the frequent and often life-threatening conditions affecting neonates, with many conditions requiring multiple chest X-rays to diagnose and monitor their progress.3 Previous studies4, 5, 6, 7 on neonatal optimisation have focused preliminary on acquisition parameters, incubator design, and/or attenuation whilst using one imaging system. Recent evidence8 also found significant variation between existing working practice when imaging neonates highlighting the need to standardise and optimise this area of imaging. An area of variation identified within this study8 was the different imaging systems (Computed Radiography (CR) and Direct Digital Radiography (DDR)) used and available at each hospital.

Since the introduction of digital systems into clinical practice, there has been a need to review dose optimisation to ensure adherence with the ALARP principle.1 It has been noted that exposure factors have not evolved and adapted much for digital systems and remain similar to those used with film-screen radiography.9 Both CR and DDR systems promised radiation dose reduction with superior image quality owing to their high detective quantum efficiency (DQE) and post-processing capabilities.10 There are many studies comparing CR and DDR in adult patients for various imaging examinations,11, 12, 13, 14, 15 however only one study was found relating CR and DDR to neonatal imaging.16 This study was a retrospective analysis only comparing image quality between CR and DDR. This study concluded that image quality for DDR was superior to CR; however, there was wide inter-rater variability and no radiation dose measures were provided. In addition, the images used in the comparisons were based on different size and weight neonates, and the location of the image receptor (directly behind neonate or in incubator tray) was not specified.16 An interesting finding within this study was that technical difficulties were encountered with DDR, this was also seen in previous studies8,17 whereby the limitations of DDR were noted especially in terms of the digital image receptor being too large to fit within the incubator tray.

The aim of this study was to explore the differences in radiation dose and image quality for neonatal incubator imaging acquired with both CR and DDR portable imaging systems.

Section snippets

Method

This study was conducted using an experimental phantom approach with a neonatal anthropomorphic phantom imaged under controlled conditions.

Results

Of the 36 acquired images from the study, the images with the highest CNR were acquired using the DDR system with the image receptor directly behind the phantom (Fig. 3 and Table 1). Conversely, the images with lowest CNR were those acquired using the CR system with the image receptor placed within the incubator tray (Fig. 3).

When comparing DDR and CR for images acquired with the image receptor directly behind the neonate, the CNR had a mean increase of 50.3% (Table 2). This was also evident

Discussion

This study was the first to explore the use of both CR and DDR for neonatal imaging using an anthropomorphic phantom under controlled conditions. It consolidated many previous findings together with making several new novel ones. This study found that DDR had superior CNR compared to CR for all acquired images under various conditions. On average, CNR of the images acquired with DDR were double that of CR. This was not surprising as many studies12,15,16,30 have found DDR to be superior to CR

Conclusion

This study was the first study to compare DDR and CR imaging systems for neonatal imaging using anthropomorphic phantoms under controlled conditions. This study found that DDR produced images of higher image quality than CR, with CNR for DDR, on average, double that of CR. In addition, incubator tray reduced CNR for both CR and DDR compared to when using a direct exposure. However, interestingly, the incubator tray exposures using DDR had an increase in CNR compared with a CR direct exposure.

Conflict of interest statement

None.

Acknowledgment

Thank you to School of Healthcare Science at Bangor University for facilitating and supporting this study.

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