Optimising image quality and radiation dose for neonatal incubator imaging

Establishing weight-based diagnostic reference levels for neonatal chest X-rays

INTRODUCTION

As weights among neonates can vary from <900 g to >2.5 kg, weight-based Diagnostic Reference Levels (DRLs) specific to the neonatal intensive care unit (NICU) are essential. Repeated radiation exposure to this sensitive patient group raises concerns regarding high cumulative radiation doses and the potential for long-term health detriment. This study aimed to establish weight-based DRLs for neonates undergoing mobile chest radiography (CXR) in the NICU.

METHODS

Neonates were classified into three discrete groups; <1000, 1000-2500 and >2500 g. Data were collected prospectively over three months; 95 DAP values were collected, and five were excluded due to poor technique, leaving 90 patients that met the inclusion criteria for mobile CXR in the NICU. Dose-area-product (DAP) in mGycm², the peak kilovoltage (kVp) and the product of tube current and exposure time (mAs) were retrieved from the Picture Archiving and Communication System (PACS). Images and radiological reports were also analysed to confirm diagnostic image quality (IQ). Local DRLs (LDRLs) were derived using the median DAP, and national DRLs were suggested using the 3rd quartile value.

RESULTS

The proposed LDRLs for neonates weighing <1000 g was 2.7 mGycm², for neonates weighing between 1000 g and 2500 g, it was 3.7 mGycm², and for neonates weighing >2500 g it was 6.6 mGycm². The radiation dose received by the 90 (100%) neonates included in the study fell below 11.4 mGycm²; of these, 82% of the DAP values fell below the study institution's existing LDRL of 7.25 mGycm².

CONCLUSION

Weight-based DRLs provide crucial information on doses to this specific radiation-sensitive group. This work recommends using weight-based categories for DRLs and serves as a benchmark for neonatal CXR standardisation and optimisation.

IMPLICATIONS FOR PRACTICE

The proposed weight-based DRLs can be adopted for neonates' locally, nationally and internationally.

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.