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| 2. |
- Lorentsson, Robert, 1969, et al.
(författare)
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A 4-afc study comparing ultrasound machines using a greyscale phantom
- 2015
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Ingår i: IFMBE Proceedings. 16th Nordic-Baltic Conference on Biomedical Engineering. October 14-16, 2014, Gothenburg, Sweden. - Cham : Springer International Publishing. - 1680-0737. ; 48, s. 82-85
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Konferensbidrag (refereegranskat)abstract
- © Springer International Publishing Switzerland 2015. Two ultrasound machines, one high-end and one ordinary, were compared in terms of their ability to reproduce low-contrast objects using the same probe. Images containing 4 mm objects of four different contrasts were collected from a greyscale phantom at 35-42 mm depth. Six observers participated in a 4-alternative forced choice study based on 120 images. At this certain depth and object size the proportion of correct responses was higher (statistically significant) for the high-end machine at three of four contrast levels, indicating the possibility to discriminate between ultrasound machines using a limited number of images of a greyscale phantom. However, the number of images and number of observers needed are larger than usually used for constancy control.
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| 3. |
- Lorentsson, Robert, 1969, et al.
(författare)
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Comparison of the low-contrast detectability of two ultrasound systems using a grayscale phantom
- 2016
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Ingår i: Journal of Applied Clinical Medical Physics. - : Wiley. - 1526-9914. ; 17:6, s. 366-378
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to use a commercially available grayscale phantom to compare two ultrasound systems regarding their ability to reproduce clinically relevant low-contrast objects at different sizes and depths, taking into account human observer variability and other methodological issues related to observer performance studies. One high-end and one general ultrasound scanner from the same manufacturer using the same probe were included. The study was intended to simulate the clinical situation where small low-contrast objects are embedded in relatively homogeneous organs. Images containing 4 and 6.4 mm objects of four different contrasts were acquired from the grayscale phantom at different depths. Six observers participated in a 4-alternative forced-choice study based on 960 images. Case sample and human observer variabilities were taken into account using bootstrapping. At four of sixteen depth/size/contrast combinations, the visual performance of the high-end scanner was significantly higher. Thus, it was possible to use a grayscale phantom to discriminate between the two evaluated ultrasound systems in terms of their ability to reproduce clinically relevant low-contrast objects. However, the number of images and number of observers were larger than those usually used for constancy control.
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| 4. |
- Lorentsson, Robert, 1969, et al.
(författare)
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Method for automatic detection of defective ultrasound linear array transducers based on uniformity assessment of clinical images - A case study
- 2018
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Ingår i: Journal of Applied Clinical Medical Physics. - : Wiley. - 1526-9914. ; 19:2, s. 265-274
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to test an idea of and describe a concept of a novel method of detecting defects related to horizontal nonuniformities in ultrasound equipment. The method is based on the analysis of ultrasound images collected directly from the clinical workflow. In total over 31000 images from three ultrasound scanners from two vendors were collected retrospectively from a database. An algorithm was developed and applied to the images, 150 at a time, for detection of systematic dark regions in the superficial part of the images. The result was compared with electrical measurements (FirstCall) of the transducers, performed at times when the transducers were known to be defective. The algorithm made similar detection of horizontal nonuniformities for images acquired at different time points over long periods of time. The results showed good subjective visual agreement with the available electrical measurements of the defective transducers, indicating a potential use of clinical images for early and automatic detection of defective transducers, as a complement to quality control.
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