Linear Motion Solutions for Medical Imaging Applications

by Christopher Nook

The number of medical imaging systems continues to grow at a projected annual rate of 6.8 percent, and linear motion control systems have become vital to the successful development, advancement, and deployment of these important pieces of medical equipment.

Medical imaging systems are now diagnostic and treatment mainstays in just about every area of clinical care, including cardiology, oncology, neurology, and trauma care. To meet growing demand, original equipment manufacturers (OEMs) need to leverage effective, modular linear motion solutions to control costs, streamline production, and beat the competition. This article will examine the various types of medical imaging systems, their motion control needs and challenges, and effective linear motion solutions for medical imaging applications.

Medical Imaging Applications that Need Motion Control

There are many types of medical imaging systems. The primary medical imaging applications that rely on linear motion control systems are:

Computed Tomography (CT) Scanners – Devices that produce 3D images of internal organs, bones, and tissues using a large series of 2D x-ray images. These images are taken using a single-axis rotating structure known as a gantry, which is driven by lead screw assemblies.
Magnetic Resonance Imaging (MRI) Scanners – Using powerful magnets that create a magnetic field that forces hydrogen atoms within the body into a certain alignment, this non-invasive diagnostic technology produces human physiological images. MRI devices distribute radio frequency energy throughout the body. This energy is interrupted by body tissue in different ways that are signaled back to the device to create an image.
Positron Emission Tomography (PET) Scanners – Measuring radiation emissions from the body that are generated by radioactive elements consumed by the patient, PET scanners produce physiological images of specific organs or tissues. They are used to identify the presence and/or growth of cancer cells.
Ultrasound Machines – These devices use sound waves to create images of what’s inside the body, such as to view a developing fetus or detect internal flaws.
X-Ray Machines – Although x-ray technology has a long history in medicine, the instantaneous availability of x-ray images in digital format is revolutionizing diagnostic radiology and sparking a growing number of applications, particularly in dentistry and surgery.

Linear Motion Control Requirements

Linear motion control systems must precisely position patients and scanning heads to achieve accurate, reliable, and trustworthy imaging results. However, this high-precision performance must be achieved in the face of challenges that are unique to the medical diagnostic environment.

Specifically, the linear motion control assemblies in medical imaging devices must operate in a fashion that is comfortable for the patient and suitable for medical diagnostic and treatment settings. They must operate smoothly, quietly, and with as little maintenance necessary as possible.

Precision-engineered lead screws are the optimal solution for medical imaging applications. Lead screws and the linear guides on which they travel can be designed to substantially reduce noise generation while simultaneously providing smooth, problem-free operation. Lead screws that are made from specially engineered plastics with internal lubrication of the screw and nut can dramatically reduce maintenance, service calls, and downtime. It’s also beneficial to utilize modular motion control systems because they can simplify engineering, reduce costs, and facilitate assembly.

Single-Plane vs. Multi-Axis Motion Control Solutions

In engineering a medical imaging system, designers initially need to determine the kinematic motion required by the device, and sometimes the algorithms needed to achieve the specified motion. The most rudimentary type of linear motion control drives single-plane motion, such as moving a patient table in and out of a scanning mechanism or up and down. This is most commonly achieved with horizontal X-Y lead screw assemblies.

However, many of today’s medical imaging devices are much more sophisticated, requiring complex and challenging kinematics. For example, some systems utilize an imaging arc, often referred to as a C-arc gantry. These systems rotate both the imaging beam source and detector 180 degrees around the patient, requiring coordination of lead screw assemblies in X, Y, and Z planes around the patient table, as well as three-axis motion control to move the table vertically and horizontally, and to tilt the table from front to back and side to side.

Even more complex kinematics are involved to support isocentric linear motion. In devices that support this function, the imaging beam is maintained at a specific point on the patient’s body while the imager and patient table move separately through many passes to create a 360-degree image. Because these motion control systems must drive up to nine axes of linear motion through the X, Y, and Z planes—all while keeping image resolution centered on a point that may only be millimeters wide—they require extremely challenging loop computations. Lead screws are the preferred solution for all ranges of medical imaging positioning complexity because of their smooth, quiet, maintenance-free, and precise operation.

Configuring Lead Screws for Your Medical Imaging Application

Configuring lead-screw assemblies to meet your particular medical device design demands a thorough understanding of the kinematics and range of motion requirements, as well as available lead screw materials and performance characteristics. Modular lead screw assemblies that are optimized for your specific application can improve performance, minimize maintenance, and reduce costs.

To learn more about lead screw assembly options for medical device design control, download a copy of our Syringe Pump Case Study.