Frequency interference artifact

Abstract

A 40-year-old Caucasian male with prior history of hypertension, dyslipidemia, and coronary artery disease was admitted with severe right lower extremity swelling and tightness. An magnetic resonance venogram (MRV) confirmed acute deep venous thrombosis (DVT) of the right common femoral, common iliac and external iliac veins along with femoro-popliteal, tibial and peroneal vein DVT. Pharmacomechanical thrombectomy and thrombolysis (PMTT) was offered, given his young age and severe symptoms. An initial venogram was performed via right popliteal access. An EKOS (Ekos Corporation, Bothell, WA, USA) catheter was then inserted to achieve accelerated thrombolysis.The EKOS catheter is a mechanical thrombolysis catheter that uses acoustic microstreaming and ultrasonic agitation to alter thrombus structure and allow the thrombolytic therapy to be more effective. The catheter consists of a series of ultrasound transducer elements spaced approximately 1.0 cm apart along its leading tip to deliver ultrasound energy radially along with the coaxial infusion.A venous duplex was ordered 6 hours after the initiation of PMTT to assess the extent of thrombolysis. The images demonstrated an interesting finding of frequency interference artifact from the interaction of a linear ultrasound transducer (9-3 MHz) and the low frequencies emitted from the EKOS transducer elements (1.1 MHz, 0.45 W) at a pulse repletion frequency of 30 Hz and a duration of 2.5 ms.1,2 This interference artifact is well demonstrated on the spectral Doppler tracing obtained within the common femoral vein (CFV) (Panel A). In addition, the B-mode image of the CFV demonstrated diamond-shaped and spotlight-like artifacts arising from the bottom of the screen (Panel B). Frequency interference artifact is a type of susceptibility artifact that normally is caused by an external source such as a radio signal, television signal or a pulse oximeter. 3 In this case, the artifact originated from within the CFV owing to the ultrasound pulsations of the EKOS catheter.Panel A

Ultrasound imaging artifacts: How to recognize them and how to avoid them

“…68 The interaction between the frequency from the ultrasound transducer and the pulsations of lower frequencies from the EKOS system ends up creating a sort of fan-shaped, "windshield wiper" artifact ( Figure 21). The EKOS system is a form of catheter-based thrombolytic delivery system used to treat pulmonary emboli.…”

“…It uses acoustic microstreaming and ultrasonic agitation via ultrasound energy from a series of ultrasound transducer elements to alter thrombus structure and allow the thrombolytic therapy to be more effective. 68 The interaction between the frequency from the ultrasound transducer and the pulsations of lower frequencies from the EKOS system ends up creating a sort of fan-shaped, "windshield wiper" artifact ( Figure 21).…”

Artefakte in der Sonografie und ihre Bedeutung für die internistische und gastroenterologische Diagnostik – Teil 1: B-Mode-Artefakte

“…Die Schallgeschwindigkeit in Silikon (1485 m/s) unterscheidet sich nur gering von Fettgewebe [21]. Artefakte durch unterschiedliche Transducerfrequenzen wurden beschrieben [22,23].…”