Case Report: A dropped probe can lead to a dropped diagnosis - by Tony Forshaw

PERTH, Australia - Sept. 26, 2014 - PRLog -- n effective Quality Assurance (QA) protocol is a critical component to the quality ultrasound laboratory. QA emphasis has largely been placed on sonographer training and ongoing professional development, with little consideration for evaluation of transducer integrity. Typical routine preventative maintenance programs (carried out by the ultrasound vendors) consist primarily of a visual inspection for probe damage and an electrical leakage safety test. More sophisticated testing protocols may also include the use of a 2D test phantom, however this is not considered a routine test by vendors, nor is it particularly effective for evaluating individual element function [1]. An additional specialized testing procedure is required to assess the proper functioning of the elements, test integrity of the cabling, and assess for delamination of the lens from the transducer elements [2].

Previous research has highlighted the alarming incidence of defective transducers currently in use in clinical practice, estimating it as high as 40% [3]. Transducers may be faulty due to: weak or “dead” elements, delamination of the lens, and/or cable damage. The effect of transducer damage on image quality has also been well described using phantoms, however the difficulty arises in identifying faulty probes during real-life scanning in that the image quality might not appear deteriorated [4]. The sonographer may fail to notice a progressive loss of image quality over time. Additionally wide variation of image quality between patients makes comparison difficult; poor image quality often attributed to the patient rather than the machine, particularly in cardiac imaging.

This case describes an instance of misdiagnosed mitral regurgitation observed following serial transthoracic echocardiography with a faulty transducer. Although the 2D image quality was largely unaffected, the severity of MR was grossly underestimated due to a faulty transducer. FirstCall testing of the transducer reported 25 transducer elements (out of an available 96) which were failing to generate a pulse sufficiently. The transducer passed electrical safety and other usual tests as part of the vendor’s routine testing. There was no visible external damage to the transducer.

Without the benefit of side-by-side comparison, or an effective transducer testing protocol, the severity of the MR lesion in the current case could have been missed entirely. This report highlights the need for routine testing of transducers, above the level of testing performed as part of a preventative maintenance service.

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