Intravascular ultrasound (IVUS) imaging is widely used in interventional cardiology as a diagnostic tool for assessing a diseased vessel, such as an artery, within the human body to determine the need for treatment, to guide the intervention, and/or to assess its effectiveness. IVUS imaging uses ultrasound echoes to form a cross-sectional image of the vessel of interest. Typically, the ultrasound transducer on an IVUS catheter both emits ultrasound pulses and receives the reflected ultrasound echoes. The ultrasound waves pass easily through most tissues and blood, but they are partially reflected by discontinuities arising from tissue structures (such as the various layers of the vessel wall), red blood cells, and other features of interest. The IVUS imaging system, which is connected to the IVUS catheter by way of a patient interface module, processes the received ultrasound echoes to produce a cross-sectional image of the vessel where the catheter is located.
There are two types of IVUS catheters in common use today: solid-state and rotational, with each having advantages and disadvantages. Solid-state IVUS catheters use an array of ultrasound transducers (typically 64) distributed around the circumference of the catheter and connected to an electronic multiplexer circuit. The multiplexer circuit selects array elements for transmitting an ultrasound pulse and receiving the echo signal. By stepping through a sequence of transmit-receive pairs, the solid-state IVUS system can synthesize the effect of a mechanically scanned transducer element, but without moving parts. Since there is no rotating mechanical element, the transducer array can be placed in direct contact with the blood and vessel tissue with minimal risk of vessel trauma and the solid-state scanner can be wired directly to the imaging system with a simple electrical cable and a standard detachable electrical connector.
In the typical rotational IVUS catheter, a single ultrasound transducer element fabricated from a piezoelectric ceramic material is located at the tip of a flexible driveshaft that spins inside a plastic sheath inserted into the vessel of interest. The transducer element is oriented such that the ultrasound beam propagates generally perpendicular to the axis of the catheter. The fluid-filled sheath protects the vessel tissue from the spinning transducer and driveshaft while permitting ultrasound signals to propagate from the transducer into the tissue and back. As the driveshaft rotates (typically at 30 revolutions per second), the transducer is periodically excited with a voltage pulse to emit a short burst of ultrasound. The same transducer then listens for the returning echoes reflected from various tissue structures, and the IVUS imaging system assembles a two dimensional display of the vessel cross-section from a sequence of several hundred of these ultrasound pulse/echo acquisition sequences occurring during a single revolution of the transducer.
Manufacturers typically focus on maximizing the fidelity of the images generated by an IVUS imaging device. Thus, these devices generally include a large number of elements to optimize image quality and consistency so that detailed images of vessel morphology are generated. As a result, manufacturing the imaging device can be complex. For example, solid-state imaging devices, such as those illustrated in FIGS. 2 and 3, can be configured with numerous transducers and associated transducer control circuits. For example, an imaging device 200 can include eight or more transducer control circuits 202 that are used to control sixty-four or more transducers 204. Manufacturing can be inefficient and expensive because of the complexity of the devices. The large number of elements also increases the size of solid-state imaging devices. This can have adverse effects on maneuverability of the device within a patient's vasculature. Further, in some instances, diagnostic procedures do not necessarily require a high resolution image of vessel morphology. Rather, only clinically acceptable lumen measurements may be needed. Currently, however, such measurements can be determined only by analyzing a detailed image generated using a complex, expensive, and large IVUS device.
Accordingly, there remains a need for improved devices, systems, and methods for providing a compact intravascular device for generating vessel measurements that can be manufactured in an efficient manner.
The present disclosure addresses one or more of the shortcomings in the prior art.