The Challenge

ELGEMS, a wholly-owned subsidiary of GE Medical Systems, was searching for the means to reduce production costs in its Millennium VG series Gamma camera, while at the same time maintaining top accuracy and efficiency.

The Millennium VG camera performs highest-quality functional anatomic mapping. It contains a complex array of devices that enable the patient to sit or lie on a movable table while the camera performs real-time automatic body contouring. Imaging is performed by two Nal detector assemblies with high-precision collimators mounted on the gantry. The collimators incorporate variable geometry detectors that feature 90° and 180° positioning for complete anatomical coverage.

In order to control the various motors driving the movable table and the adjustable collimators along the various axes, several drive controllers were needed. Such a configuration tended to be both costly and space consuming. What was needed was a compact and cost-efficient assembly of multi-axis drivers that could concurrently control the scanner motors while guaranteeing the highest level of reliability and functionality.

Elmo’s Solution

In order to meet the special requirements of the Millennium VG scanners, Elmo decided to design an innovative assembly – the ELG-2000 – that consists of two separate drive units:
the ELG-15/55 and the ELG-15/200. The two units are derived from Elmo’s field-proven Violin series of miniature servo amplifiers for DC brush motors. Each unit is a multi-axis controller containing three current amplifiers for three different axes, a built-in power supply with a single-phase AC input, a DC-to-DC converter and a MOSFET-based shunt regulator for 15A current.

The entire ELG-2000 assembly is therefore capable of controlling six axes in the Millennium VG scanner: two axes for the movable table, and two axes for each collimator. The assembly can be further enhanced in the future to incorporate more drive units to provide added multi-axis motion control.

ELGEMS estimates that incorporation of the ELG-2000 assembly into the Millennium VG scanners has provided savings of 10% in production costs, stemming from reduced assembly time and lower component prices. The miniature system, one-fifth in size of the drive previously used, can be quickly and easily mounted And just as important: a major side benefit of the ELG-2000 assembly has been a significant enhancement in system performance and reliability.

One of the two ELG-2000 units. The two units together provide simultaneous control over six motion axes.