Imaging the neonate in the incubator: an investigation of the technical, radiological and nursing issues

Neonatal digital chest radiography- should we be using additional copper filtration?

OBJECTIVES

Copper filtration removes lower energy X-ray photons, which do not enhance image quality but would otherwise contribute to patient radiation dose. This study explores the use of additional copper filtration for neonatal mobile chest imaging.

METHODS

A controlled factorial-designed experiment was used to determine the effect of independent variables on image quality and radiation dose. These variables included: copper filtration (0 Cu, 0.1 Cu and 0.2 Cu), exposure factors, source-to-image distance and image receptor position (direct / tray). Image quality was evaluated using absolute visual grading analysis (VGA) and contrast-to-noise ratio (CNR) and entrance surface dose (ESD) was derived using an ionising chamber within the central X-ray beam.

RESULTS

VGA, CNR and ESD significantly reduced (p < 0.01) when using added copper filtration. For 0.1 Cu, the percentage reduction was much greater for ESD (60%) than for VGA (14%) and CNR (20%), respectively. When compared to the optimal combinations of parameters for incubator imaging using no copper filtration, an increase in kV and mAs when using 0.1-mm Cu resulted in better image quality at the same radiation dose (direct) or, equal image quality at reduced dose (in-tray). The use of 0.1-mm Cu for neonatal chest imaging with a corresponding increase in kV and mAs is therefore recommended.

CONCLUSION

Using additional copper filtration significantly reduces radiation dose (at increased mAs) without a detrimental effect on image quality.

ADVANCES IN KNOWLEDGE

This is the first study, using an anthropomorphic phantom, to explore the use of additional Cu for digital radiography neonatal chest imaging and therefore helps inform practice to standardise and optimise this imaging examination.

Evaluation of radiation dose to organs of neonatal patients during portable X-ray examination in incubators: A Monte Carlo simulation study

BACKGROUND

Infants admitted to neonate intensive care units (NICUs) are placed in incubators to maintain body temperature and condition, which undergo normal radiographs and are exposed to radiation. Furthermore, different incubator structures in different hospitals exhibit varying object to image receptor distance (OID), source to image receptor distance (SID), presence of canopy, which results in variations in X-ray radiation conditions and doses absorbed by the neonatal patients.

OBJECTIVE

To measure organ dose exposed to neonatal patient in different incubator settings.

METHODS

A portable X-ray was performed on a neonatal patient placed in an incubator to identify disease progress, the injection path of the drug, and various factors. To minimize direct contact between neonatal patients and image receptor, radiologic technologists place the image receptor on a tray underneath the incubator and place the portable X-ray tube on top of the acrylic canopy of the incubators. SID and OID settings and value of organ dose exposed to the patient varied based on the incubator structure, and the organ absorbed dose was determined using Monte Carlo N-Particle (MCNP) simulation, PC-based Monte Carlo program (PCXMC) 2.0 simulation, and neonate phantoms.

RESULTS

Evaluations of organ dose of neonatal patients in three hospitals with different incubator settings reveal that the average organ dose differs by 36% depending on change in OID and SID settings and reduces by 10% with an acrylic canopy. Therefore, owing to the presence of an acrylic canopy on the top of the incubator and the longer SID with the corresponding shorter OID, a lower dose was absorbed by organs of neonatal patient.

CONCLUSION

Our results provide proof that proper incubator standard decreases organ dose to neonatal patient during continuously diagnostic X-ray procedure.

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

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.

Optimising image quality and radiation dose for neonatal incubator imaging

INTRODUCTION

Neonates often require imaging within incubators however limited evidence exists as to the optimal method and acquisition parameters to achieve these examinations. This study aims to standardise and optimise neonatal chest radiography within incubators.

METHODS

A neonatal anthropomorphic phantom was imaged on two different incubators under controlled conditions using a DR system. Exposure factors, SID and placement of image receptor (direct v tray) were explored whilst keeping all other parameters consistent. Image quality was evaluated using absolute visual grading analysis (VGA) with contrast-to-noise ratio (CNR) also calculated for comparison. Effective dose was established using Monte Carlo simulation using entrance surface dose within its calculations.

RESULTS

VGA and CNR reduced significantly (p < 0.05) whilst effective dose increased significantly (p < 0.05) for images acquired using the incubator tray. The optimal combinations of parameters for incubator imaging were: image receptor directly behind neonate, 0.5 mAs, 60 kV at 100 cm SID, however, if tray needs to be used then these need to be adapted to: 1 mAs at maximum achievable SID. Effective dose was highest for images acquired using both incubator tray and 100 cm SID owing to a decrease in focus to skin distance. There is significant increase (p < 0.01) in VGA between using 0.5 mAs and 1 mAs but an apparent lack of increase between 1 and 1.5 mAs.

CONCLUSION

Using the incubator tray has an adverse effect on both image quality and radiation dose for incubator imaging. Direct exposure is optimal for this type of examination but if tray needs to be used, both mAs and SID need to be increased slightly to compensate.

IMPLICATIONS FOR PRACTICE

This study can help inform practice in order to both standardise and optimise chest imaging for neonates in incubators.

Imaging neonates within an incubator - A survey to determine existing working practice

INTRODUCTION

There is limited and confusing evidence within the literature regarding the optimal techniques when imaging neonates within incubators; in particular, whether to place the image receptor directly behind the neonate or in the incubator tray. For this reason, radiology departments across Wales and North West England were surveyed to explore existing working practice with regards to incubator imaging.

METHOD

A self-designed survey was developed using a systematic approach. The survey was sent to 31 radiology departments across Wales and North West England whom had a neonatal unit in order to assess existing techniques used when imaging neonates within the incubator. The survey was split into three main domains: 1) general/demographics, 2) exposure factors and technique, and 3) incubator design.

RESULTS

Nineteen departments responded (64%) demonstrating a wide variation in practice for incubator imaging. The minimum and maximum exposure factors used for neonatal chest x-ray imaging varied from 55 kV to 65 kV and 0.5 mAs-2 mAs. Fifty-eight percent of departments used the incubator tray as standard practice with the remaining forty two percent not using the tray for various reasons including, image quality, artefacts and misalignment. Sixty-three percent of departments use the maximum achievable SID for incubator imaging which demonstrates wide variability as the SID would be dependent upon: incubator design, portable machine and radiographer height.

CONCLUSION

The survey demonstrates a wide variation in existing practice for neonatal incubator imaging.

IMPLICATIONS FOR PRACTICE

This study supports the need for standardisation and further optimisation work to ensure best practice for this vulnerable patient group.

A systematic review of incubator-based neonatal radiography - What does the evidence say?

OBJECTIVES

This systematic review aimed to explore the impact of incubator design (canopy, mattress, and mattress support) on neonatal imaging in terms of imaging technique, radiation dose and image quality.

KEY FINDINGS

A systematic literature review was performed by searching multiple healthcare databases. Following study selection and extraction, 7 articles were deemed eligible and included within the study. Of these 7 studies, six were experimental phantom based with the remaining one being a retrospective analysis. Four studies reported a percentage reduction in beam attenuation for incubator components ranging from 12% to 72% with one other study reporting a reduction but with no numerical data. This wide variation in radiation beam attenuation from the incubator components was correlated with image quality within five studies, two suggesting reduced image quality when using the incubator tray under the mattress support whilst the other three found no significant difference. Although the seven studies reported that incubator components reduced X-ray beam intensity, there was limited evidence on whether this required an increase in exposure factors. Only one study suggested increasing exposure parameters to accommodate for the increase in beam attenuation when using an incubator tray.

CONCLUSION

The literature clearly demonstrates that with existing incubator designs, there is considerable beam attenuation between placing the image receptor directly behind the neonate as oppose to the incubator tray. However, this radiation beam attenuation is not well correlated to neonatal radiation dose or image quality effects and therefore is very confusing when considering clinical implementation.

IMPLICATIONS FOR PRACTICE

This review highlights the need for standardisation and further optimisation work to ensure best practice for this vulnerable patient group.

DOSE EVALUATION FOR DIGITAL X-RAY IMAGING OF PREMATURE NEONATES

X-ray radiography is a commonly used diagnostic method for premature neonates. However, because of higher radiosensitivity and young age, premature neonates are more sensitive to the detrimental effects of ionising radiation. Therefore, it is important to monitor and optimise radiation doses at the neonatal intensive care unit (NICU). The number of x-ray examinations, dose-area product (DAP) and effective doses are evaluated for three Dutch NICUs using digital flat panel detectors. Thorax, thorax-abdomen and abdomen protocols are included in this study. Median number of examinations is equal to 1 for all three hospitals. Median DAP ranges between 0.05 and 1.02 μGy m2 for different examination types and different weight categories. These examinations result in mean effective doses between 4 ± 4 and 30 ± 10 μSv per examination. Substantial differences in protocols and doses can be observed between hospitals. This emphasises the need for up-to-date reference levels formulated specifically for premature neonates.

Effect of comfort pads and incubator design on neonatal radiography

BACKGROUND

There has been increasing interest in patient dose reduction in neonatal intensive care units. Removing comfort pads for radiography has been identified as a potential means to decrease patient dose.

OBJECTIVE

To assess the effect of comfort pads and support trays on detector entrance exposure (DEE) and image quality for neonatal radiography, and its implication for patient dose.

MATERIALS AND METHODS

Comfort pads and support trays from three incubator and warmer systems were examined. The attenuation of the primary beam by these structures was measured using a narrow beam geometry. Their effect on DEE and image quality was then assessed using typical neonatal chest radiography techniques with three configurations: 1) both the comfort pad and support included in the beam, 2) only the support tray included and 3) both the comfort pad and support tray removed.

RESULTS

Comfort pads and support trays were found to attenuate the primary beam by 6-15%. Eliminating these structures from the X-ray beam's path was found to increase the detector entrance exposure by 28-36% and increase contrast-to-noise ratio by more than 21%, suggesting room for patient dose reduction when the same image quality is maintained.

CONCLUSION

Comfort pads and tray support devices can have a considerable effect on DEE and image quality, with large variations among different incubator designs. Positioning the image detector directly underneath neonatal patients for radiography is a potential means for patient dose reduction. However, such benefit should be weighed against the risks of moving the patient.