Detectors and Sample Racks

The detector arrangement consists of 12 detector scintillation counters arranged in two rows of six wells each. For special measurements – or if a detector is faulty – it is possible to disable individual detectors selectively. Washable plastic racks are used to place the samples into the wells. The sample diameter can be up to 14.5 mm in the rack and up to 16 mm when placed directly into the detector, any length being accommodated. Easily exchangeable plastic inserts in each detector provide contamination protection.

The Multitasking Microprocessor System

The highly sophisticated microprocessor system allows simultaneous counting, analysis and data output. The instrument is capable of storing the counts up to 4 sample racks and evaluating them later, so that samples can be measured even during the calculation and printout of the standard curve. Buffering of data at all input/ output points effectively eliminates operator waiting, and thus allows multitasking, i.e. several functions are performed simultaneously.

High Voltage Adjustment and Standardization

To ensure optimum performance of the LB 2111 system, the instrument performs a quality control using pre- programmed routing programs for High Voltage Adjustment and Standardization. In the high voltage adjust program, the high voltage supply to each detector is automatically modified by successive amounts until an optimum count rate is reached for the isotope in use. The adjustment can be done with ¹²⁵I, ¹²⁹J or ⁵⁷Co using a single source or 12 sources. The standardization program is used to correct for any slight variations of the crystal efficiencies. Since the efficiency of the crystal is specific for the isotope being measured, the instrument must be standardized for each isotope routinely counted. In the standardization routine, a single source is counted in each detector (or 12 matched sources are counted simultaneously), correction factors are calculated and stored to compensate for any differences between wells.

Since the standardization must be carried out only after the optimum high voltage gain adjustment is complete, the standardization program automatically performs a high voltage adjustment prior to the relative efficiency measurements and calculations. The background counts in each well are also determined and stored during standardization for use in raw CPM correction.

Data Input

In the MEASUREMENT and the ROUTINE MEASUREMENT mode, the data are directly entered from the counter into the computer. (The routine measurement bypasses the pauses in the program where the operator may review or edit the data). CPM data may also be entered manually with each count being entered in to sequences of tubes defined for the specific assay. The re-run option automatically reprocesses the last set of data entered, allowing the user to analyze a group of counts repeatedly to evaluate the effect to changes made in the para meter mode on the same set of data, i.e. a change in curve fit selection. By choosing to use a stored standard curve, the LB 2111 will automatically evaluate new unknown sample CPM (either directly from the counter or manually entered) using the last standard curve run on a particular assay. When this option is selected, a reference must be run with the new unknown sample.

Data Protection

Information stored in the instrument is protected against loss for at least three months in the event of a power failure or if the interment is switched off.

Computer Connection

The LB 2111 is supplied as standard with a V.24/RS 232 interface. Communication settings are user selectable. Test number, sample ID, CPM and/or results with patient ID are transmitted.

Dialog and Printout

Data input and output are handled via a video screen with keyboard and high speed printer.

Dimensions LB 2111:

Width: 395 mm, height: 235 mm,depth: 510 mm
Weight: approx. 39 kg
Power Supply: 220 V, 50 Hz; 110 V, 60 Hz; alternative power supplies on applications