Ultrasound focal lesion detectability phantoms

Abstract

Two phantoms for assessing the performance of ultrasound scanners regarding detectability of small focal lesions are described. The spherical simulated lesions in the phantoms have diameters of 2.4, 3.0, and 4.0 mm and backscatter coefficients which are 16, 9, and 6 dB below that of the surrounding tissue-mimicking material, the latter simulating normal tissue such as liver. Random positioning and relatively large numbers of lesions deal with the statistical problem related to mistaking a normal textural fluctuation, characteristic of ultrasound images of parenchymal tissue, to be a small lesion. All lesions have ultrasonic properties that are the same as those of the surrounding material except for the backscatter coefficient; therefore, artifacts resulting from attenuation, reverberation, and/or refraction are absent, and detectability of deeper lesions is not influenced by the presence of more proximal ones. A method is outlined for using the phantoms to determine bounding proximal and distal depths of resolution, or detectability, of focal lesions of a given object contrast and size. Tests for observer dependence involving five subjects resulted in standard deviations in the distal and proximal depths of less than 0.5 cm. A repeat of the observer dependence tests 18 months later showed little change in the results. In addition, results obtained by two experienced observers are also given for a variety of specific scanners, scanning heads, and scanning parameters.

Development of a catheter for combined intravascular ultrasound and photoacoustic imaging

“…Silica particles ͑Sigma-Aldrich, Inc.͒ with 0.5% weight concentration and an average size of 40 m were added to gelatin solution to act as ultrasound scatterers. 35 Optical scattering was mimicked by adding 20% of low-fat milk ͑volume concentration͒. 36 The overall size of the phantom's body was measured to be 40ϫ 35ϫ 30 mm while the lumen diameter was equal to 6 mm.…”

Comparison of the low‐contrast detectability of two ultrasound systems using a grayscale phantom

“…Regarding the phantom properties, to use objects formed as cylinders to evaluate the ability to detect spherical lesions has been questioned, since the effect of the slice thickness on the image is not taken in account 7 , 12 . Comparing the performance of different systems regarding contrast‐detail detectability could be misleading if the elevational resolution differs much between the systems at the actual depth.…”

“…The best way to perform a comparison of low‐contrast lesion detectability with real observers would be to choose a tissue mimicking phantom that makes it possible to acquire many statistically independent views of each target 10 , 11 from a phantom containing spherical objects of different sizes, contrasts and depths 7 , 12 , 13 . None of the six investigated manufacturers of commercial test equipment (CIRS, Gammex, Blue Phantom, Kyoto Kagaku, ATS, and Dansk Fantomservice) has a phantom like this in their product catalog.…”

Phantoms and automated system for testing the resolution of ultrasound scanners

“…Rotation at 2 rpm about a horizontal axis during congealing prevented lack of uniformity of glass bead and graphite distribution. More details regarding temperatures and techniques can be found in an earlier work (Madsen et al 1991) .…”

“…Phantoms for testing the resolution of ultrasound scanners using spherical simulated small focal lesions have been previously reported (Madsen et al 1991, 1994). Each section of these phantoms contains many spatially randomly distributed spherical simulated lesions (all with the same diameter and contrast) extending over a depth range from OS-15.5 cm.…”