Dose reduction in a neonatal intensive care unit

Transcription

1 Dose reduction in a neonatal intensive care unit Poster No.: C-0908 Congress: ECR 2015 Type: Authors: Keywords: DOI: Scientific Exhibit C. V. Pul, N. Zegveld, M. Pareren, P. Andriessen, M. Boekhorst, G. F. Roos, T. Linden; Veldhoven/NL Thorax, Digital radiography, Radiation safety /ecr2015/C-0908 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 7

2 Aims and objectives The purpose of the study is to evaluate the image quality and Dose Area Product (DAP) of critically ill patients in the neonatal intensive care unit (NICU) using a digital X-ray system, for the different categories of neonates, in order to investigate the radiation dose to the infant and to determine whether there is room for further dose reduction. Methods and materials A digital Carestream DRX-Revolution was acquired for the NICU and implemented using the same image settings as used with a phosphor-based Shimadzu MX-100. We compared Contrast-to-Noise ratio (CNR) and Signal-to-Noise ratio (SNR) for thorax images between two systems (67/84 images of DRX/Shimadzu), with Regions of Interest (ROI) as shown in Figure 1. For the DRX system, dose-area-product (DAP) was listed. In an experimental setup, dose settings were measured using dosimeter Piranha, at 6 positions in the incubator, similar to the setup used by Mutch et al (3). At the NICU, 7 protocols are available for imaging, the protocol used depends on the weight of the premature infant. Therefore, in the experiment, the different weight categories were simulated using phantoms with different PMMA thickness and the detector dose was measured. For each category, effective dose was estimated using PCXMC (4). Next, with unaltered dose on detector, X-ray settings were optimized for imaging without the incubator being in the imaging chain. These optimized settings were also used to calculate the patient dose, representing a patient imaged while not being in the incubator. The possible dose reduction by imaging outside the incubator was then determined. Images for this section: Page 2 of 7

3 Fig. 1: Definition of Regions of Interest (ROIs) in the thorax images of neonatal patients. Left: Shimadzu image. Right: DRX image. Page 3 of 7

4 Results A significantly higher CNR is observed in DRX-images compared to Shimadzu-images (Figure 2, left panel) For the SNR of the lungs, no significant differences were observed between the two systems (Figure 2, right panel). As expected, the DAP increases for increasing weight class (Figure 3), since the kv and mas are adjusted. DAP in neonates of 3,8kg averages 0,58 µgy m2, for smaller neonates DAP is (much) lower. The absorption of the mattress and the Perspex holder in the incubator (directly above the detector) was determined in the phantom measurements and showed that the mean dose absorbed in mattress + holder was 38%. From the phantom measurements, effective dose was calculated and the effective dose was lower with 44% when imaged without incubator. Images for this section: Fig. 2: Left: Contrast-to-noise ratio measured between lung and mediastinum for the patients in the different weight classes. Right: Signal-to-noise ratios measured for the lungs in the same patients. The digital DRX system is indicated by the crosses and the old Shimadzu system by the red circles. Page 4 of 7

5 Fig. 3: DAP measured for each patient as a function of increasing weight class (in grams); Page 5 of 7

6 Conclusion Image quality of the digital DRX system is better than the phosphor-based system with respect to CNR ratio, although SNR is similar. Since phosphor-images were of acceptable quality as reviewed by the radiologists, further dose reduction might be possible in NICU by slightly adjusting the image parameters, though a careful approach is necessary since the SNR is not allowing for large adjustments. The DAP values observed in the images acquired by the DRX are considerably below Diagnostic Reference Level (5,6), which is defined at 1,5 µgy m2 for a newborn of 4 kg by the Dutch committee (6). The effective dose to the patient is not easily determined from the clinical DAP values. From the simulations in PCXMC (4) it can be estimated that a typical dose to the phantom is 5,5 mgy using a DAP value similar as measured in the clinical data. These values are smaller than the radiation doses mentioned in literature (1,2). Dose reduction is possible when imaging the newborn outside the incubator and might be considered for stable neonates. This can be achieved by only lowering mas values, though further research is necessary to determine the optimal parameter choices. Personal information Carola van Pul, PhD. Department of Clinical Physics, Maxima Medical Center, Veldhoven, The Netherlands; and School of Medical Physics and Engineering, Eindhoven University of Technology, The Netherlands; c.vanpul@mmc.nl Nikki Zegveld, Department of Radiology, Maxima Medical Center, Veldhoven, The Netherlands; nikki.zegveld@mmc.nl Mark van Pareren, Department of Radiology, Maxima Medical Center, Veldhoven, The Netherlands; mark.van.pareren@mmc.nl Peter Andriessen, Department of Neonatology, Maxima Medical Center, Veldhoven, The Netherlands; and Department of Paediatrics, Faculty of Health, Medicine and Life Science, Maastricht University, Maastricht, The Netherlands; p.andriessen@mmc.nl Mariska Boekhorst, Department of Radiology, Maxima Medical Center, Veldhoven, The Netherlands; m.boekhorst@mmc.nl George Roos, Department of Radiology, Maxima Medical Center, Veldhoven, The Netherlands; f.roos@mmc.nl Page 6 of 7

7 Toine vd Linden, Department of Radiology, Maxima Medical Center, Veldhoven, The Netherlands; References (1) Yu CC. Radiation safety in the neonatal intensive care unit: too little or too much concern? Pediatr Neonatol 2010 Dec;51(6): (2) Donadieu J, Zeghnoun A, Roudier C, Maccia C, Pirard P, Andre C, et al. Cumulative effective doses delivered by radiographs to preterm infants in a neonatal intensive care unit. Pediatrics 2006 Mar;117(3): (3) Mutch SJ, Wentworth SD. Imaging the neonate in the incubator: an investigation of the technical, radiological and nursing issues. Br J Radiol 2007 Nov;80(959): (4) Tapiovaara M, Lakkisto M, Servomaa A, Siiskonen T. A PC Based Monte Carlo program for calculating patient doses in medical X-ray examinations (5) Wall BF. Implementation of DRLs in the UK. Radiat Prot Dosimetry 2005;114(1-3): (6) NEDERLANDSE COMMISSIE VOOR STRALINGSDOSIMETRIE. Diagnostische referentieniveaus in Nederland Page 7 of 7