Keywords:
Performed at one institution, Diagnostic or prognostic study, Not applicable, Quality assurance, Filter insertions, Digital radiography, Conventional radiography, Radioprotection / Radiation dose, Paediatric, Musculoskeletal spine, Paediatrics
Authors:
M. Oseberg1, M. Sanden2, M. Riktor3; 1Kjeller/NO, 2Lørenskog/NO, 3Oslo/NO
DOI:
10.26044/ecr2020/C-10377
Methods and materials
The study was conducted at Akershus University Hospital (Norway).
Phantom and equipment
- The study was performed using a digital X-ray system, with image stitching equipment and software program ( Fig. 1 ).
- It was conducted on a pediatric anthropomorphic phantom.
Conducting of experiments
- Five scans on four different filters ( Fig. 2 ).
- Same exposure parameters:
- - 240 cm Source Image Distance (SID).
- - 66 Kilovolt (kV) in the first image.
- - 73 Kilovolt (kV) in the second image.
- - Automatic Exposure Control (AEC).
- The phantom stands in Posterior-Anterior position (Lateral radiographs were not included in this study).
- Two images, covering the spine and pelvis, are acquired during a craniocaudal scan.
- One single overview image is reconstructed from the series of overlapping images ( Fig. 3 ).
Calculation of radiation dose
- PCXMC software with Monte Carlo simulation to estimate the effective dose (ED) according to ICRP103 [9] was calculated based on the Dose-Areal-Product (DAP) (µGym2).
- Air Kerma (AK) was also calculated with PCXMC.
- The percentage changes are calculated relative to no filtration (0Al).
Image quality assessment
- Image criteria for the examination:
- Entire spine from cervical vertebrae level 7 to sacrum.
- Good visualizing of the intervertebral discs.
- Femoral heads.
Subjective image quality assessment:
- One muscle-skeleton radiologist and one pediatric radiologist, both experienced, independently analyzed the image quality.
- Subjective image quality was evaluated in Sectra Picture Archiving and Communication System (PACS) on computer monitors.
- Image quality was evaluated by using a 5-point scale (1 = worst, 5 = best) ( Fig. 4 ).
- The image score was accomplished by comparing one random image from each of the filtrations against the image without filtration (0Al).
- They considered how well they could see the image criteria.
Objective image quality assessment:
- The objective image quality was evaluated in PACS.
- It was assessed by calculating SNR and CNR for different tissues and analyzed using an oval-shaped Region of Interest (ROI).
- Three different ROI ( Fig. 5 ):
- Intervertebral disk
- Vertebral body
- Diaphragm
- The positioning of the ROI markers was done after consultation with a medical physicist.
- Signal to noise ratio (SNR) and contrast to noise ratio (CNR) was calculated from the ROI results.
- The percentage changes are calculated relative to no filtration (0Al).
Statistics
- The standard deviation was determined for the total DAP values (µGym2).
- Statistical data was displayed in graphs and tables.