Draw wire sensors offer precision in operating theatres 

Chris Jones, Managing Director at Micro-Epsilon (UK) Ltd discusses how draw-wire displacement sensors are helping medical operating theatres in a number of critical applications, including X-ray machines, CT scanners, patient tables and flexible surgical arms.

Utilisation and cost efficiency are now just as important measures to medical operating theatres as they have always been to manufacturing companies. The latest operating tables, for example, offer numerous functions for precise handling of the patient, but need to be efficient and cost-effective.

Typically, operating tables are modular in design and offer multiple adjustment options for the precise positioning of the patient during an operation. As well as the height of the table, the horizontal position and several angular functions for the head, torso and legs also need to be adjustable.

In order to enable these adjustments, suitable measuring devices are required. Draw-wire displacement sensors are ideal for this, combining a compact design with high precision and long service life. The sensors can integrate easily with the operating table, offering an excellent price/performance ratio for the customer.

The principle of a draw-wire displacement sensor is relatively straightforward, hence its inherent reliability. The sensor works rather like a tape measure, except with a draw-wire sensor; the user does not have to read off the measurement of the extended tape. The rotation of the drum on which the steel wire is wound is measured automatically and the measurement signal is output in either analogue or digital formats. The drum itself incorporates a long-life spring drive, which ensures the steel wire is rewound. (Refer to pictures on the right).

The latest X-ray machines also require precise positioning so that they can provide high quality images of patients. The digital camera on these machines has to be aligned exactly with the X-ray tubes so that high resolution recordings can be produced. The cameras, X-ray tubes, the table and the wall stands can be moved on several axes, providing maximum flexibility.

Draw-wire sensors can be used to position the mechanical moving parts. The synchronisation controller in the X-ray unit then uses the displacement data from the sensors to ensure that the X-ray tube and camera move parallel to each other.

Similarly, Computer Topography (CT) equipment requires fast, precise but cost effective measurement systems. Spiral, helical and dual source CT systems all require more precise, faster sensors.

The length measurement equipment for the horizontal reclined position is important here. In order to obtain the best possible overall image of the target, the individual X-ray sections, which normally travel through the object, have to be measured with smaller and smaller spacing. To do this, the sections are compiled in a 3D model to obtain voxels (volumetric and pixel). Based on this complete volume data set, any 3D views or sectional planes can be produced. In order to correctly align the sections, the horizontal position of the couch must be measured precisely. Therefore, a measuring system with very high resolution and long measuring range is required. Here, draw-wire sensors can offer resolutions down to 0.001% of the measuring range.

Draw-wire sensors are not only suitable for horizontal and vertical axis measurements; they can also be used to measure angles on operating tables and flexible surgical arms.

Flexible surgical arms are used to assist surgeons during surgical procedures, providing them with several degrees of freedom of movement. Starting from a calibrated zero point, the arm, which is attached to an operating table, automatically performs the required incremental movements. An endoscopic camera is guided by the robot arm, achieving a 360-degree view with up to 80-degrees incline from the perpendicular of the endoscope.

Typically, the arm must be immune to MR and X-rays and so sensors cannot be used in the area directly above the operating table. Therefore, direct measurement of the angular movements of the arm with angle sensors is not possible. However, the angle of rotation can be measured indirectly by using draw-wire sensors, which are installed underneath the operating table. Several sensors are required, which provide either an angle proportional output signal (potentiometer) or a digital incremental output.

Micro-Epsilon in profile
Micro-Epsilon is a major global manufacturer of sensors, headquartered in Germany. The company's range of displacement sensors measure everything from to distance, position, vibration, dimensions and thickness, using both contact and non-contact measurement techniques. These techniques include 1D, 2D and even 3D laser-optical sensors and systems, eddy-current, capacitive, LVDT & inductive, potentiometric and draw-wire principles.  Additionally Micro Epsilon has developed its own range of non-contact infrared temperature sensors that can measure virtually any target temperature from -40 to +3,300^°C.

With more than 30 years' experience in the industry, Micro-Epsilon isn't just a sensor manufacturer. The company is highly innovative and understands the importance of providing complete solutions and support services for its customers. The firm is renowned for its expertise in consulting, development and application of industrial sensors to complex, customer-specific solutions for measurement, inspection and automation. The focus is on selling technical advantage to its customers.       

For further information on draw wire displacement sensors, e-mail: info@micro-epsilon.co.uk  or view website: www.micro-epsilon.co.uk  Refer to page 310

The StomacherÒ 80 microbag, from Seward Ltd

The StomacherÒ 80 microbag, from Seward Ltd, is designed specifically for use in the Stomacher 80 microBiomaster to prepare and process biological samples at volumes as low as 250µL to 5 mL.

The key to the microBag's micro-processing capabilities is its novel "V" shape, which enables it to be processed by a single paddle in the Stomacher machine. This unique design gives the scientist the choice of diluent-free sample processing, whilst ensuring a completely homogenised sample with maximal cell recovery.

The "V" shape also ensures the successful recovery of every drop of the processed sample, which is vital when processing volumes down to 250µL. Once homogenised, the sample can be pulled down to the tip of the V between thumb and forefinger, the homogenate can then be extracted using either a pasteur pipette, or by cutting the bag to a sufficient height to enable use of a standard pipette. This simple sampling and extraction process is shown on the Seward website www.seward.co.uk/video.htm (click on the Stomacher 80 Biomaster video).

The Stomacher® 80 microBiomaster provides flexible small tissue processing capabilities for clinical, life science and microbiology applications. The microBiomaster utilises all the Stomacher 80 bag range, in addition to its own Stomacher 80 microBag. This enables it to process samples from 250µL to 80mL.

The Stomacher® has been proven in laboratories around the world to be a valuable tool in industry, research, education and healthcare. In scientific procedures the quality of the sample and its preparation are critical to accurate results, Stomacher has been and continues to be developed to achieve this.

For further information, view website: www.seward.co.uk  Refer to page 304 

Thermo Scientific Barnstead Nanopure water
purification systems exceed industry standards

Thermo Fisher Scientific, added a new water quality specifications for the Thermo Scientific Nanopure Life Science water purification system. Thermo Fisher evaluated the system to see how well it cleared bacteria, pyrogens and nucleases from a sample using highly sensitive testing protocols. The results indicate that Nanopure-purified water can be used in scientific applications that are most sensitive to these impurities. Customers who traditionally purchase nuclease-free bottled water or who treat water with DEPC (Diethylpyrocarbonate) will benefit from the efficiencies of having an on-demand source of nuclease-free water.

Thermo Fisher tested the bacteria and pyrogen levels in conjunction with Nelson Laboratory of, Salt Lake City. The testers found that the pyrogen level in the Nanopure water was <0.001 EU/ml, and the bacteria level was <0.01 CFU/ml. Thermo Scientific Genomics in Milwaukee, Wis. tested for the presence of nucleases, and the testers found that RNase level was <0.003 ng/ml and the DNase level was <0.4 pg/ml.  All measurements exceeded current industry standards. 

Customers who require pyrogen and nuclease-free water can use the Nanopure Life Science unit to produce ultrapure water on demand. The system utilizes an ultrafilter to clear these biological impurities from the water. The integration of the ultrafilter into the main water flow of the system enables continuous rinsing of the filter and provides additional protection from potential contamination for a life-span of up to two years. This cost-effective pure water system produces extremely high-quality nuclease-free and pyrogen-free water.

To view or download the new Thermo Scientific Waterbook, which showcases the new Nanopure specifications and the entire portfolio of Thermo Scientific laboratory water purifications products, view website: www.thermoscientific.com/waterbook  Refer to page 282