![]() The measurements from a model observer, well designed for the task, are quick, precise, and objective. Since model observers generally involve simple detection and discrimination tasks - in which a known target profile embedded in noise is discriminated from a known alternative profile - the development of models has typically considered diagnostic features in terms of signal and noise characteristics. Quantifying the performance of medical imaging modalities can be done either by using human or model (mathematical) observers. Which consequently is an important performance measure of an ultrasound system. This objective is closely related to low‐contrast detectability One of the quantitative objectives in the B‐mode image is to detect and, if possible, identify the presence of limited‐size tissue masses (lesions) within or adjacent to a reference tissue. The acoustic properties of the patient, the transmitter unit, how the beams are formed, the properties of the transducer, the receiver, how the signals and the image are processed, the quality of the display, and finally the ability of the user to drive the scanner and probe and interpret the displayed information all affect the probability for a correct diagnosis. There are many steps involved from the actual examination to the outcome of the same. The purpose of the medical ultrasound system is to reproduce the echogenicity of the patient as accurately as possible. However, the number of images and number of observers were larger than those usually used for constancy control. 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. At four of sixteen depth/size/contrast combinations, the visual performance of the high‐end scanner was significantly higher. Case sample and human observer variabilities were taken into account using bootstrapping. Six observers participated in a 4‐alternative forced‐choice study based on 960 images. ![]() Images containing 4 and 6.4 mm objects of four different contrasts were acquired from the grayscale phantom at different depths. The study was intended to simulate the clinical situation where small low‐contrast objects are embedded in relatively homogeneous organs. ![]() One high‐end and one general ultrasound scanner from the same manufacturer using the same probe were included. 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. ![]()
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