Reminder: EE PhD Oral Examination - Amin Nikoozadeh, Friday, June 4, 2010; 9:30 a.m.

Stanford University Oral Defense - Department of Electrical Engineering

 

Speaker: Amin Nikoozadeh

 

Title: Intracardiac Ultrasound Imaging Using Capacitive Micromachined Ultrasonic Transducer (CMUT) Arrays

 

Advisor: Professor B. T. Khuri-Yakub

 

Date: Friday, June 04, 2010
Time: 09:30 AM (Refreshments at 9:15 AM)

Location: Clark Center Auditorium (Basement, entrance across from Nexus)

Map: http://ucomm.stanford.edu/map/?q=Clark%20Center&sf=a.BLDG_NAME

ABSTRACT
Atrial fibrillation, the most common type of cardiac arrhythmia, now affects more than 2.2 million adults in the US alone. Currently, electrophysiological interventions are performed under fluoroscopic guidance, which does not provide adequate soft-tissue resolution and exposes the patient and the operator to harmful ionizing radiation. Intracardiac echocardiography (ICE) provides real-time anatomical information that has proven valuable in reducing the fluoroscopy time and enhancing procedural success. Currently, piezoelectric transducer technology dominates the ultrasound imaging market. For ICE catheters, however, the limited available space and stringent packaging requirements challenge efforts to build a piezoelectric transducer array at the tip of the catheter for forward-looking imaging. This difficulty arises from the piezoelectric transducer manufacturing process, which is based on meticulous and labor-intensive steps.

 

I have developed two types of multi-functional forward-looking ICE catheters using capacitive micromachined ultrasonic transducer (CMUT) technology: MicroLinear (ML) and Ring catheters. The ML catheter enables real-time forward-looking 2-D imaging using a 1-D CMUT array. The Ring catheter uses a ring-shaped 2-D CMUT array that enables real-time forward-looking 3-D imaging. Both of these catheters are equipped with custom-designed front-end circuits that are integrated with the transducer at the catheter tip.

 

In this talk, I will describe the main components of these catheters. I will show how the integrated front-end IC improves the SNR by more than 20 dB. I will explain how all the components are integrated in the tight space available for full catheter construction with 100% yield. This task involved numerous challenges, especially in the case of Ring catheter, wherein, I successfully flip-chip bonded 8 IC’s (1.2 mm × 1 mm) and a Ring array (2.5 mm in diameter) to a flexible substrate with a total of 244 interconnects. I will also present in-vivo imaging results obtained using these catheters. In the last part of the talk, I will introduce a new CMUT structure that exhibits ideal piston-like plate movement. Contrary to a conventional CMUT, the top plate in the proposed structure does not need to be operated in flexural mode. This results in significantly improved fill-factor, and thus, a more efficient transducer.