Review article – A narrative review on the reduction of effective dose to a paediatric patient by using different combinations of kVp, mAs and additional filtration whilst maintaining image quality

This paper reviews the literature for lowering of dose to paediatric patients through use of exposure factors and additional filtration. Dose reference levels set by The International Commission on Radiological Protection (ICRP) will be considered. Guidance was put in place in 1996 requires updating to come into line with modern imaging equipment. There is a wide range of literature that specifies that grids should not be used on paediatric patients. Although much of the literature advocates additional filtration, contrasting views on the relative benefits of using aluminium or copper filtration, and their effects on dose reduction and image quality can vary. Changing kVp and mAs has an effect on the dose to the patient and image quality. Collimation protects adjacent structures whilst reducing scattered radiation

Experimental article – Reducing effective dose to a paediatric phantom by using different combinations of kVp, mAs and additional filtration whilst maintaining image quality

Purpose: To determine whether using different combinations of kVp and mAs with additional filtration can reduce the effective dose to a paediatric phantom whilst maintaining diagnostic image quality. Methods: 27 images of a paediatric AP pelvis phantom were acquired with different kVp, mAs and additional copper filtration. Images were displayed on quality controlled monitors with dimmed lighting. Ten diagnostic radiographers (5 students and 5 experienced radiographers) had eye tests to assess visual acuity before rating the images. Each image was rated for visual image quality against a reference image using 2 alternative forced choice software using a 5-point Likert scale. Physical measures (SNR and CNR) were also taken to assess image quality. Results: Of the 27 images rated, 13 of them were of acceptable image quality and had a dose lower than the image with standard acquisition parameters. Two were produced without filtration, 6 with 0.1mm and 5 with 0.2mm copper filtration. Statistical analysis found that the inter-rater and intra-rater reliability was high. Discussion: It is possible to obtain an image of acceptable image quality with a dose that is lower than published guidelines. There are some areas of the study that could be improved. These include using a wider range of kVp and mAs to give an exact set of parameters to use. Conclusion: Additional filtration has been identified as amajor tool for reducing effective dose whilst maintaining acceptable image quality in a 5 year old phantom

Reducing effective dose to a paediatric phantom by using different combinations of kVp, mAs and additional filtration whilst maintaining image quality

Purpose: To determine whether using different combinations of kVp and mAs with additional filtration can reduce the effective dose to a paediatric phantom whilst maintaining diagnostic image quality. Methods: 27 images of a paediatric AP pelvis phantom were acquired with different kVp, mAs and additional copper filtration. Images were displayed on quality controlled monitors with dimmed lighting. Ten diagnostic radiographers (5 students and 5 experienced radiographers) had eye tests to assess visual acuity before rating the images. Each image was rated for visual image quality against a reference image using 2 alternative forced choice software using a 5-point Likert scale. Physical measures (SNR and CNR) were also taken to assess image quality. Results: Of the 27 images rated, 13 of them were of acceptable image quality and had a dose lower than the image with standard acquisition parameters. Two were produced without filtration, 6 with 0.1mm and 5 with 0.2mm copper filtration. Statistical analysis found that the inter-rater and intra-rater reliability was high. Discussion: It is possible to obtain an image of acceptable image quality with a dose that is lower than published guidelines. There are some areas of the study that could be improved. These include using a wider range of kVp and mAs to give an exact set of parameters to use. Conclusion: Additional filtration has been identified as amajor tool for reducing effective dose whilst maintaining acceptable image quality in a 5 year old phantom

The Influence of CT Reconstruction Methods on the Accuracy of Monitoring Lung Nodule Diameters at Different Dose Levels

Purpose: This study aims to investigate the effect of filtered back projection (FBP) and sinogram-affirmed iterative reconstruction (SAFIRE) on the accuracy of lung nodule diameter measurements at different dose levels. Method: 48 CT images were acquired (at tube-current time product of 10, 20, 30 and 40 mAs) using an anthropomorphic phantom Lungman N1 ©, containing simulated spherical lung nodules of +100 Hounsfield Units of 5, 8 and 12mm diameter. Images were reconstructed with FBP and SAFIRE strengths 1, 3, and 5. Twelve participants, with radiographic experience, performed nodule diameter measurements for all images. Nodule edge sharpness was calculated for all images by measuring the angle of profile edge slope.Contrast to Noise Ratio (CNR) values were obtained from pixel values in regions of interest (ROIs) in the lung nodule and background air. Measurement accuracy was assessed by calculating the absolute error percentage (AEP) between participant’s measurements and actual nodule size.Results: There is no significant difference in nodule diameter measurement between mAs values and reconstruction algorithms (p-value 0,009 - 0,969). AEP showed no significant difference (p-value 0,041-0,969) for any of the reconstruction algorithms. Discussion: Previous research using SAFIRE suggests a decrease of mAs while maintaining image quality. Furthermore, SAFIRE has the ability to increase CNR and decrease image artefacts. However, the findings in this study suggest that accuracy of lung nodule measurement does not improve with an increase of CNR values nor the line profiles of edge sharpness. Conclusion: Our study suggests that image dose levels can be reduced without compromising nodule diameter measurement accuracy, regardless of reconstruction method