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IMPROVED CARDIAC GATING FOR MEDICAL IMAGING

IP.com Disclosure Number: IPCOM000192581D
Publication Date: 2010-Jan-25

Publishing Venue

The IP.com Prior Art Database

Abstract

A technique for improved cardiac gating is disclosed. The technique allows partial recovery of data from abnormal beats and reduces data lost due to view start time not coinciding with beat start time. The method described herein allows logical division of heartbeat cycle and optimal synchronization to Electrocardiography (ECG) during image acquisition by use of other ECG wave forms (P, Q, S, and T).

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RP13295

IMPROVED CARDIAC GATING FOR MEDICAL IMAGING

BRIEF ABSTRACT

    A technique for improved cardiac gating is disclosed. The technique allows partial recovery of data from abnormal beats and reduces data lost due to view start time not coinciding with beat start time. The method described herein allows logical division of heartbeat cycle and optimal synchronization to Electrocardiography (ECG) during image acquisition by use of other ECG wave forms (P, Q, S, and T).

KEYWORDS

    Cardiac gating, signal to noise ratio, SNR, ECG, electrocardiogram, waveform, abnormal beats, synchronization, logical division, heartbeat cycle

DETAILED DESCRIPTION

    The heart of a living patient beats in quasi-periodic cycles. Static imaging of the beating heart suffers from image blurring due to the motion. Generally, imaging is synchronized to the beating using electrocardiogram (ECG) signal. Such synchronization is referred to as cardiac gating. The cardiac gating allows capturing and viewing the motion in cine mode. For cardiac gating, the heart cycle is divided into equal time bin phases, and each phase is treated separately.

    However, patients needing heart imaging often exhibit irregular heart rate and irregular heartbeats. As shown in Figure 1, abnormal heart rate results in

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RP13295

Signal to Noise Ratio (SNR) reduction. Bad beats are caused by muscular motion or electronic noise. Typically a bad beat causes a loss of a few adjacent beats. For example in traditional gated SPECT, typical scenario is as flows: each view lasts about 30 seconds, the detector moves to new position in about 2 seconds, heart rate is about1 beat / second, about 60 views are acquired (in dual detectors - 2 views are concurrently acquired). Therefore, typical total acquisition time is (30+2)*30/60= 16 min. Average lost time is about 3 seconds/view (~9.50%) due to detector motion and view start time not coinciding with beat start time. Further, each abnormal beat causes rejection of the two adjacent heart cycles. Thus, 20% abnormal beats cause about 36% acquisition time loss while compensating for adjacent bad beats.

    Further, in several imaging modalities, such as single Photon Emission Computed Tomography (SPECT), Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) among others, the imaging system acquires data in views separated in time. Gated image reconstruction requires analysis of the views having the same phase. Signal to Noise Ratio (SNR) per phase further decreases due to the division of the acquisition time. Data is collected for a shorter time for each phase. As shown in Figure 2, data is lost due to view start time not coinciding with beat start time.

    Furthermore, often the entire data set must be rejected (and the study repeated) if at least one of the view-phase sub-sets is devoid of valid data. As total acquisition time...