Integration of Three-Dimensional Echocardiography in Routine Clinical Practice

Data Acquisition

Several parameters must be considered before data acquisition:

• 1

  Mode of acquisition

• 2

  Acquisition beats

• 3

  Volumetric size

There are three modes of data acquisition: (1) narrow-angled acquisition, (2) zoom acquisition, and (3) wide-angled acquisition. The choice of acquisition mode depends on the structure of interest. If the patient has mitral stenosis, a zoom acquisition is best to focus mainly on the mitral valve and reduce the chances of stitch artifacts and a higher frame rate. If left ventricular or right ventricular function were the object of interest, then a wide-angled acquisition would be preferable so that the entire ventricle could be acquired.

Acquisition beats pertain to the number of beats required to build a larger volume. Most systems allow a one-beat acquisition, for instance, of the left ventricle but also have the option of a lower frame rate with higher spatial resolution or a higher frame rate with lower spatial resolution. The most ideal acquisition is a one-beat acquisition with high frame rate and high spatial resolution. However, the physics of ultrasound does not allow this, so there is a tradeoff. The acquisition of valve pathology is best performed by using a one-beat acquisition since it avoids stitch artifacts. However, with a lower frame rate, fine structures may not be optimally visualized.

Image Display and Analysis

There are several methods of image display:

• 1

  Volume-rendered imaging

• 2

  Wire-frame image

• 3

  Surface-rendered image

• 4

  2D slice planes

Most systems now acquire data and immediately display images on the ultrasound system without any delay in processing. A volume-rendered image is preferable for visualizing all anatomic structures. Endocardial tracing of a ventricle or chamber results in a wire-frame image, which then can be displayed as a surface-rendered image when a surface is placed over the wire-frame rendition of the structure. A 3D volume can also be displayed as 2D slices to demonstrate ventricular wall motion or measure an orifice such as atrial septal defect (ASD), ventricular septal defect (VSD), or the mitral valve area.

There are many approaches to RT3DE image display. However, after acquiring the data, the cut plane should be displayed so that it can be easily interrupted by the reader or others who are not familiar with RT3DE.

Transducer Technology

Several ultrasound vendors offer products with 3D imaging capabilities incorporated into a 2D imaging probe or an independent 3D imaging probe. With advanced electronics, significant miniaturization has resulted in a fully sampled 3D transesophageal echocardiography probe. Obviously, having one integrated 2D-3D transducer is key, particularly when trying to promote an imaging protocol with 3D imaging. However, in systems with separate 2D and 3D transducers, 3D imaging could be performed after the 2D standard protocol is obtained or even prior to the 2D exam (see Chapter 3 ). Essentially, the balance of spatial resolution and frame rate is more evident in 3DE compared with 2DE.