X, Y, and Z of 3D-USA
This course includes information on the display of both the static 3D image and the real-time 4D image. Included is a foundation of rotations (X, Y, and Z), data set acquisition methods, and the use of Quality settings.
Successful completion of this training is eligible for American Society of Radiology Technician (ASRT) Category A continuing education units (CEU).
Welcome to the Siemens Healthineers X, Y and Z of 3D tutorial. Before we begin, I would like to introduce myself briefly. I will be your guide to help you understand the information presented in this tutorial. During the course, I will be giving you a lot of detailed information. Click the information icon in the lower left corner for tutorial Navigation Tips. This tutorial has more information in the form of links placed on the page. To successfully complete this course, please view all available content. We hope you enjoy our tutorial. Click on the right arrow to continue. Upon completion of this tutorial, you will be able to: Describe the components of a data set. Explain freehand and automated acquisition of the data set. Associate threshold and opacity adjustments to changes in the voxel and image. Please note that the learning material is for training purposes only! For the proper use of the software or hardware, please always use the Operator Manual or Instructions for Use (hereinafter collectively “Operator Manual”) issued by Siemens Healthineers. This material is to be used as training material only and shall by no means substitute the Operator Manual. Any material used in this training will not be updated on a regular basis and does not necessarily reflect the latest version of the software and hardware available at the time of the training. The Operator Manual shall be used as your main reference, in particular for relevant safety information like warnings and cautions. Note: Some functions shown in this material are optional and might not be part of your system. The information in this material contains general technical descriptions of specifications and options as well as standard and optional features that do not always have to be present in individual cases. Certain products, product related claims or functionalities described in the material (hereinafter collectively “Functionality”) may not (yet) be commercially available in your country. Due to regulatory requirements, the future availability of said Functionalities in any specific country is not guaranteed. Please contact your local Siemens Healthineers sales representative for the most current information. The reproduction, transmission or distribution of this training or its contents is not permitted without express written authority. Offenders will be liable for damages. All names and data of patients, parameters and configuration dependent designations are fictional and examples only. All rights, including rights created by patent grant or registration of a utility model or design, are reserved. ACUSON Sequoia and Clarify VE Technology are trademarks of Siemens Medical Solutions USA, Inc. Copyright © Siemens Healthcare GmbH, 2018 Selecting the ► continues this course and confirms you have read and understand this disclaimer. Spatial relationships of anatomic structures are the basis of finding the presence or absence of pathology within the body. The sonographic exam has long entailed obtaining multiple, static, sequential 2D-mode images which the clinician mentally reconstructed. Real-time allows for imaging of organ motion while Doppler images vessel flow. The last step, the reconstruction of anatomy in 3D, now occurs in both static and real-time (4D). To create the 3D and 4D images, the ultrasound system acquires and stores a group of sequential 2D images which we call the volume. During the 4D acquisition, the ultrasound system continuously acquires and displays the volume information in a real-time format. Also known as real-time 3D ultrasound, time becomes the fourth dimension. Click on the right arrow to continue. Three dimensional and real-time 4D images have now become an integral part of the ultrasound exam. Called a data set, the 3D image is simply a group of 2D images stacked, like dominos, to create a 3D volume.1 The data set allows the clinician to review the exam on multiple planes, including those missing in conventional 2D imaging. Additionally, clinicians can compare datasets from earlier exams. This clearly demonstrates the need to understand the creation and utility of 3D and 4D imaging in all sonographic modalities. The 3D or 4D image depends directly on the quality of the 2D-mode image and patient body habitus. If the grayscale image is low-quality, the resulting data set will be suboptimal. Factors influencing the 3D/4D image. Obstetrics Gynecology Abdomen Size and activity of fetus Fetal position Fetal age Amount of amniotic fluid Soft tissue interfaces Uterine and ovarian condition and size Woman's age Pelvic and adnexal pathology Presence of pathology We are all familiar with the 2D-mode image composed of pixels.2 The pixels lie on two planes, the X and Y axis. The 2D-mode image lacks depth and is essentially flat2 showing depth and length. Two-dimensional imaging is done on two planes. The Y axis is the vertical plane.2, 3 The X axis is the horizontal plane.2, 3 We can change the appearance of the pixel through our adjustment of factors such as overall gain (brightness), or dynamic range. We are used to seeing the 2D-mode image; however, our world exists in three spatial dimensions. In medical imaging, the 3D data set adds the third, volume plane, called the Z axis2 or depth. A series of sequential 2D-mode images make up the 3D data set. The Z axis is depth (arrow). Once we add the volume we now describe the smallest part as a voxel.4 This reconstructed Z axis is the result of the 2D-mode images placed within the 3D matrix creating a volume.4 An interpolation technique, or averaging between the volumes, fills in missing data between the voxels.1 The 3D data displays on three planes that differ from 2D imaging. The reconstructed images display anatomy as a volume rather than the traditional slice seen with 2D imaging. The first thing to understand is the orthogonal planes used during a 3D reconstruction. This cube illustrates the orthogonal placement of the 3D volume. The A plane (blue), B plane (red) and C plane (yellow) intersect at 90 degrees to create the voxel.2 The C plane adds the depth to the data set.2 The 3D data set is a series of 2D-mode images. The reconstructed image is simply a single image taken from within the data set. The center dot or cross-hairs placed on the image show the reconstructed image pivot point. This is the location where the planes intersect.4 The left set of blocks shows a set of 27 voxels. If we wanted to create a 2D image, we would use a subset of this data (right diagram).4 The red dot represents one pivot point or axis for rotating the planes.2 The three orthogonal planes and the volume display in a format called the multiPlanar image. When the 3D volume anatomy displays as a MultiPlanar Rendering or MPR, the images represent the three planes with orthogonal relationships.3 These planes are called: The A plane which is the acquisition plane, B plane which is 90 degrees lateral to the A plane, and the C plane which is 90 degrees coronal to the A plane. The A, B, and C planes are the same as the X, Y, and Z planes2 mentioned earlier, however, there may be only indirect correlation.3 A colored dot or cross-hairs on the image shows where the three planes intersect.3, 4 Moving this marker moves you within the 3D data set. This MPR image of a fetal brain shows the three reconstructed planes (right) plus the volume reconstruction (left). Note the reference dot (arrow) found in the center of the brain showing the pivot point for the three orthogonal planes. The acquisition plane displays on the upper right (A plane) with the 90-degree orthogonal image (B plane) on the middle left. The coronal plane (C plane) displays on the lower right. The volume reconstruction shows the intersection of the three planes (dotted circle). MultiSlice is the display of multiple sequential images from any plane of the 3D data set.2 This MultiSlice image of the fetal heart shows how we use information from the 3D data set. Like computed tomography or magnetic resonance images, multiple parallel slices of the chosen plane display. This allows for study of sequential anatomy and structures, as with this image of the fetal heart, without the need for a new acquisition. This image shows the pivot point as a reference dot within the aortic root. The horizontal lines represent the displayed slices. This image is the acquisition plane taken of the left ventricular outflow tract (LVOT) showing the left atrium and ventricle, aortic valve, aortic root, and the right and left ventricle. The dot placement is in the aorta.5 Ninety degrees to the LVOT, the three-vessel view appears,5 showing the ascending and descending aorta, pulmonary artery, and the superior vena cava. The Z in the lower right corner indicates a zoomed image. Ultrasound systems often use shared control panel controls that allow for rotation of the 3D and 4D image. The central dot, or reference point, seen in the MPR views, or volume, shows not only the intersection of the planes but the pivot location. This image of an ultrasound system control panel shows the use of multifunction rotary controls. The Angle control rotates the image around the X axis, the spectral Doppler (D) control rotates the image around the Y axis, and the color Doppler (C) control rotates the image around the Z axis. The M-mode rotary control also allows adjustment of the MPR Slicing. Remember, manipulations affect ALL planes simultaneously around a central axis, but only the active plane correlates to the respective X-, Y-, or Z-dial control maneuvers. Click on the icon below to learn more about rotations Click the right arrow to continue. Learn More about Volume Rotation Volume Rotation Tab TitleTextX axisX axis manipulations rotate the active image horizontally on the display. The icon displayed by the system varies when viewing the 3D image (without box) or the volume (box) around the central point. The image or data set rotates on the X axis around on a horizontal plane similar to a rotisserie. An example of an X axis 3D volume rendering rotation icon. An example of an X axis 3D image rotation icon. Y axisY axis manipulations rotate the volume (box) or active image (without box) vertically on the display around the central point. The image or data set rotates on the Y axis around a vertical plane similar to a drill or a ballet dancer performing a pirouette. An example of a Y axis 3D volume rendering rotation icon. An example of a Y axis 3D image rotation icon. Z axisZ axis manipulations rock the volume (box) or active image (without box) clockwise or counterclockwise around the central point. The image or data set rotates on the Z axis resulting in moving the image back and forth in a rocking motion. An example of a Z axis 3D volume icon rotation with an obliquely oriented volume rendering. An example of a Z axis 3D image rotation icon. One method to obtain qualitative 3D volumes is by using standard imaging (freehand) transducers. Transducers that support automated 3D acquisition provide quantitative data. The transducer mechanically sweeps through the region of interest (ROI) while stationary. This is called an automated acquisition. 3D images may provide slightly better image resolution, but 4D imaging provides the ability to collect information about movements and spatial relationships of a structure. The data sets can be collected, stored, and viewed in 3D. Time is the fourth dimension which allows for the presentation of captured motion. Standard imaging transducers require you to move the transducer by using either a fan/rocking or linear/sliding motion.2 These movements occur on the elevation plane of the transducer. Also called hand held ultrasound (HHUS), this is a freehand acquisition of the data set. In freehand 3D imaging, you can use the two motion methods to acquire a 3D volume. This method requires you to move the transducer over the region of interest resulting in a quantitative 3D data set. Due to the lack of geometric accuracy and position sensors, freehand acquisitions do not allow for measurement of anatomy as we do not know the interval between the 2D-mode slices.4 A series of 2D images are recorded as the sonographer scans over the anatomy. Click on the icon below to learn more about acquiring the freehand data set. Click the right arrow to continue. Learn More about Freehand 3D Learn More about Freehand 3D 3D Freehand Imaging Tips3 Use the highest frequency transducer possible. Apply gel to the entire area of scanning. Use consistent transducer pressure. Optimize the 2D image in a 2D-mode. Position the transducer over the anatomy of interest. Maintain slow, constant speed. Suspend patient respiration as movement distorts the image. Mechanical automated volume imaging transducers contain a motor to ensure consistent data acquisition. Often called ‘wobblers’, the motor automatically sweeps the transducer elements through the selected region of interest (ROI) while the transducer is held stationary. The ultrasound system computer records the position and sweep speed, allowing for calibration and measurement of image structures. When activated by the sonographer, the motor inside the transducer aligns with the far side of the ROI and then performs an automated sweep across the entire 3D region of interest. Upon completion of the sweep, 3D software creates a rendering of the scanned anatomy. Click on the icon below to learn more about automated 3D and 4D. Click the right arrow to continue. Learn More about Automated 3D & 4D Learn More aboutAutomated 3D & 4D Tab TitleTextAutomated AcquisitionTo perform an automated transducer sweep, the transducer remains stationary, situated in the center of the region or area of interest. Most automated transducers perform a sweep that is oriented with the 2D preview image in the center of the sweep fulcrum. Upon activation of the 3D or 4D acquisition, the transducer motor pivots to sweep through the entire region of interest in a fan-like manner. The angle of the sequential 2D-mode is fixed resulting in an increase in distance between slices with increasing depth. This loss of 2D image data at depth results in a decrease in image quality4 underscoring the importance of using the the smallest ROI and sweep angle possible. 4D, or 4-dimensional, is the real-time, automated acquisition of volume datasets. The fourth dimension is time. 4D sonography is also known as real-time 3D sonography. The display of the surface rendering is the result of continuous sweeping back and forth of the array to produce the 4D image. Automated Imaging Tips Use the highest frequency transducer possible. Optimize the 2D image in 2D-mode. Use the smallest possible ROI or volume of interest (VOI). When possible, use a high Quality setting to increase image detail. Adjust the volume angle (how far the transducer sweeps during acquisition) as small as possible. Hold the transducer still, with light even pressure during acquisition. QualityThe Quality setting on an ultrasound system allows us to select the resolution and acquisition time. The chosen level, quality versus time, is a compromise between image detail and the speed of the data set sweep. The Quality setting determines the number of 2D images acquired in the sweep. A higher Quality setting obtains more 2D images, has an slower data collection time which may result in a higher image quality. Lowering the Quality setting increases the volume rate; however, the data set resolution decreases due to fewer 2D images used in image reconstruction. The targeted anatomy will help you decide the importance of either seeing the separation of structures (lateral or spatial resolution) or detection of moving anatomy (temporal resolution) for each data set. These fetal phantom images show how line density changes detail of a surface rendering. The displayed MPR shows the B plane on the top right (asterisk), the A plane in the middle, and the C plane on the lower right (arrowhead). The left image shows a high line density setting the right shows a low density setting. Increasing or decreasing the volume rate also changes the axial, lateral, spatial, and temporal resolution.4 Additional factors influencing the volume rate include the acquisition depth, VOI size, and Quality. Sweep Angle The sweep angle is the distance the mechanical 3D transducer moves the array during the data set acquisition. Use a wider sweep angle with a large or superficial structure such as in the following situations: Quiet late pregnancy fetus.2 Uterine imaging to include the fundus to the cervix or right to left ovaries. Use a smaller sweep angle when you wish to decrease acquisition time such as when: Imaging an active fetus. Obtaining a fetal heart data set. Angle selections change the volume rate displayed during 4D imaging.2 Small angle selections increase the volume rate while large angles decrease the volume rate. These images of a fetal phantom show how angle adjustment changes the 3D data set. The displayed MPR shows the B plane on the top right (asterisk), the A plane in the middle, and the C plane on the lower right (arrowhead). Ten degrees is the smallest angle size (left) with an increase to 45-degrees (middle), and the largest angle at 75-degrees (right). Increasing or decreasing the Angle changes the number of 2D slices available in each plane. The 3D image displayed on the monitor is a rendering of the volume data. We can adjust the resulting image by changing the threshold and opacity. Done at the voxel level, these system adjustments change the image creating the appearance of a 3D object. Two controls, the opacity, and threshold of the data set allows us to render the surface of a structure.4 Keep in mind, multiple adjustments result in the optimal image. Click on the icon below to learn more about voxel adjustments. Click the right arrow to continue. Learn More about Voxel Processing Learn More about Voxel Processing Tab TitleTextThreshold2, 4During obstetric imaging, a fetal face is often an expectation; however, factors such as the presence of vernix in the amniotic fluid obstruct our view. To minimize the effect the low-level echoes created by the vernix, we adjust the Threshold level. If we wish to remove information obstructing a structure, in our example, the face, we would increase the threshold to remove echoes. Remember! The fetal image quality depends on many factors including amniotic fluid amounts, maternal habitus, placental location, and the presence of artifacts. Opacity2, 4Opacity allows the creation of a softer or sculptured appearance of the imaged structure. Increasing the opacity level results in a solid appearance of a structure. Decreasing results in a transparent appearance. To visualize the fetal face, we use a lower opacity as we wish to see a smooth skin surface. In gynecologic imaging, a high opacity level helps image a myoma, fibroma, endometrial disease or hemorrhagic cysts. Explore the links below for the Glossary, References, and Further Reading opportunities. Glossary Glossary 2D, or 2-dimensional - Describes the single slice image acquisition that is used in B-mode imaging. The ultrasound image displayed on the monitor represents two dimensions. 3D imaging - Calibrated or freehand single sweep through volume of tissue. 4D imaging - Continuous real-time 3D sweeps through volume of tissue using mechanical transducers. A plane –Acquisition plane. B plane – Ninety degrees to the acquisition plane. C plane – Coronal plane to the acquisition plane. Data Set and Volume – Saved 3D/4D. multiPlanar – More than one plane. Opacity – Adjusts the surface density. Pixel – Term describing the smallest element of a digital image. Region of interest (ROI) – An area showing the whole area of data acquisition. Surface rendering – Creation of an image structure with a skin-like appearance. Threshold – Filters or adds low-level echo information from the 3D volume. Transparency – Adjustment of how well we see through a voxel. Volume of Interest (VOI) – Defines how to display the volume. Also called a Render Box. Voxel – The small, box-like structure within a slice of the data set. X axis – Line indicating horizontal rotation around a central point. Y axis – Line indicating vertical rotation around a central point. Z axis – Line indicating clockwise or counterclockwise rotation around a central point. References / Further Reading References / Further Reading 1. Kremkau, F.W. (2016). Sonography: Principles and Instruments. 9 ed., St. Louis: Elsevier. 2. Lunsford, B. (2017). 3D and 4D imaging in obstetrics and gynecology. In Stephenson, S.R. and Dmitrieva, J., (Eds.), Diagnostic Medical Sonography: Obstetrics and Gynecology (pp. 805-836). Philadephia: Wolters Kluwer. 3. Raatz Stephenson, S.R. (2005). 3D and 4D sonography history and theory. Journal of Diagnostic Medical Sonography. 21(5): 392-399. 4. Hedrick, W. (2013). Technology for diagnostic sonography. St. Louis, MO: Elsevier. 5. Jantarasaengaram, S. and Vairojanavong, K. (2010). Eleven fetal echocardiographic planes using 4-dimensional ultrasound with spatio-temporal image correlation (STIC): a logical approach to fetal heart volume analysis. Cardiovascular Ultrasound. 8(1): 41. Congratulations! You have completed the X, Y, and Z of 3D tutorial. Listed below are the key points presented in this tutorial. Take time to review the material before you try the final quiz. Download and print a copy of the detailed Course Review In this tutorial you have learned to: Describe the components of a data set. Explain freehand and automated acquisition of the data set. Associate threshold and opacity adjustments to changes in the voxel and image. eSieImage is a trademark of Siemens Medical Solutions, USA, Inc.