Abstract
The high incidence of defective ultrasound transducers in clinical practice has been shown in several studies. Recently, a novel method using only stored images for automatic detection of defective transducers was presented. The method makes it possible to remotely monitor many transducers at the same time and send a notification when a defective transducer is found. The purpose of the present study was to evaluate the novel method and assess how well it performs when compared to an established method as reference. To evaluate the novel method, in-air images were collected from 81 transducers in radiologic departments in nine hospitals. Two observers assessed the in-air images and marked the defects. Receiver operating characteristic (ROC)- and alternative free response receiver operating characteristic (AFROC)-curves and their figures of merit (FOM) were calculated for the novel method, using marked defects in the in-air images as reference truth. The area under the ROC curve was 0.88 (SD 0.06), and the AFROC FOM was 0.71 (SE 0.07). The result shows that the novel method has a good agreement with the in-air method for detecting defects in ultrasound systems. This indicates that the novel method could be a complement to the normal quality control for early, and automatic detection of defects.
Highlights
Ultrasound transducers are by nature exposed to harm, and the high incidence of defective transducers in clinical practice has been shown in several studies [1,2,3,4,5,6]
The increased depth resulted in darker regions in the edges of the extracted part of the images and made the alternative free response receiver operating characteristic (AFROC) figures of merit (FOM) value significantly smaller (0.64, p = 0.014) than the case, when the original depth was used
The decreased number of images resulted in some temporary false Systematic Dark Region (SDR) curves, but since the limit was 20 days, this did not affect the AFROC FOM
Summary
Ultrasound transducers are by nature exposed to harm, and the high incidence of defective transducers in clinical practice has been shown in several studies [1,2,3,4,5,6]. Mårtensson et al [1] tested 676 transducers from seven manufacturers using an electronic tester (FirstCall (Sonora Med ical Systems, Inc., Longmont, CO, USA)) and found that 39.8% exhibited some kind of transducer error. In a follow-up study [2] 299 transducers that were classified as fully functional the previous year were tested again. 27.1% of the transducers were found defective and the conclusion was that annual testing is not sufficient. [3] tested 151 transducers using FirstCall, of which 135 were tested using a tissue mimicking phantom. For the FirstCall and the phantom test the proportion of defective transducers was 17% and 16% respectively. One reason why the methods complement each other is that the electronic test of the transducer cannot find faults that are located in the scanner
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