Assay Programming and Data Reduction
The GENESYS Genii Series gamma counters contain advanced data reduction features suitable for calculating all versions of RIA, IRMA, Ratio and Screening assays. With the flexibility to independently choose curve fit, response variable (transformation) and graph paper, the GENESYS Genii gives you the power to adequately handle the wide range of radioimmunoassays available for clinical and research applications; from the routine through the esoteric.
The range of popular curve fits include: point to point, cubic spline, straight line, weighted straight line and four parameter logistic (4PL).
Response variables include: %B/TC, %B/B0, CPM, TC/B, B0/B, 1/CPM, CPM/(standard #), %CPM/ (High Standard), CPM/(TC-CPM) and (TC-CPM)/CPM.
Standard curve axes choices are: Linear-Linear, Semi-Log, Log-Log, Logit-Log, Linear-Log and Log-Linear.
With this variety of choices, even the most demanding applications can be met with ease. Here is a brief description of each curve fit algorithm.
Point to Point
This curve fit connects adjacent standard points with a straight line. This is a “connect the dots” approach, and is quite commonly used in older software packages and for connecting particularly difficult data. This curve fit is best used when there are many standard points within the curve, or when there is a very sharp change in slope. This curve fit minimizes curvature errors.
The Cubic Spline is actually not a single curve, but rather a series of curvilinear segments, which are joined together at “knots”. These knots are the standard points. Therefore, the overall curve must pass through the mean of each of the standard points exactly. The cubic spline fit is very commonly used in IRMA assays, where a larger number of standard points is typical. Due to the nature of the cubic spline equation, the standard curve must contain at least 4 points in order to fill the equation.
This curve fit utilizes a single, straight line to fit all standard points within the curve. This fit, therefore, requires that all points on the curve be first “linearized”. This is most often accomplished by using a Logit-Log or bound type of transformation. By first linearizing the data, fitting errors will be minimized.
Weighted Straight Line
This curve fit begins as a straight line, then adds “weighting factors” as needed. These weighting factors are particularly helpful to minimize the effect of stray points which are further from the most stable portion of the curve (mid dose). The weighting factor changes the slope of the curve to maximize the influence on the mid-dose area of the curve.
Four Parameter Logistic
The four parameter logistic curve fit is based upon the “All Fit” program originally developed at NIH. It is basically an extension of the two parameter Logit-Log method. By its nature, the 4PL, like the cubic spline must have at least four standard points in order to plot a curve. The four parameter is the most “robust” of all the curve fits, and is the most widely suitable for a variety of applications from sigmoidal or J-shaped RIA’s to high sensitivity IRMAs.
The nature of the 4PL equation requires that the GENESYS Genii SERIES gamma counters perform many iterations of highly complex calculations in order to achieve the best fitting curve.
Quality Control Software
The GENESYS Genii Series multi-well gamma counter comes equipped with software to allow quality control evaluation and storage.
Probably the most useful feature of all within the QC software, is its ability to update the QC limits – either for a marked range or for the entire table. There are no manual calculations involved, GENESYS does all the work when you select UPDATE LIMITS.
With complete QC reports, including Levey-Jennings charts, no more manual plotting is required.
After run number 31 is reached, the oldest run is removed and all other runs moved up one. In this way GENESYS always keeps the most current 30 QC runs available.
As you can see, GENESYS QC software is extremely versatile and comprehensive and an integral part of the GENESYS Genii Series.
Decay Corrected Stored Curve
The following assay was run with the stored curve feature. Note the decay correction of the standards:
When using a stored curve, the user is able to:
- SAVE TIME: When only running the QC’s and unknowns, the user has saved time in sample preparation and reading the assay. This increases the turn-around time; which is especially important in Stat situations.
- MAINTAIN ACCURACY: The assay standards are corrected for isotope decay, minute by minute. Verifying Quality Control tubes gives added assurance.
- SAVE MONEY: Tubes and reagents are saved each time a stored curve is run. This allows for doing tests in-house that were once send outs because of the low volume.
While I125 is certainly the most commonly used isotope in the clinical laboratory, other applications and uses often arise. In Nuclear Medicine facilities, research laboratories, extended clinical and esoteric testing often require the use of different isotopes. The GENESYS Genii Series gamma counters are designed to effectively and efficiently count a wide variety of isotopes, vastly extending the useful range beyond routine RIA.
The GENESYS Genii Series gamma counters utilize a NaI(tl) crystal detector. These detectors incorporate a monoline well-type configuration, ensuring superior geometry and counting efficiency over through-hole styles. The well is bored deeply to accommodate varying sample sizes with minimal loss of efficiency due to “angle of incidence”. This unique crystal design enables the GENESYS to count high energy isotopes without the need for extremely large diameter detectors. Having many wells counting simultaneously, along with the high efficiency design of our crystals greatly increases the throughput.
Each GENESYS detector contains extra crystal mass at the bottom of the detector to allow better “stopping power” for higher energy isotopes. Greater efficiency is achieved than with traditional small diameter detectors. Two stage lead shielding provides excellent shielding between detectors, with additional heavy lead plates surrounding the entire detector array. This provides very low background radiation levels, for improved signal to noise ratio and superior counting results.
For assays involving the use of more than one isotope simultaneously (i.e. B12_Folate), The GENESYS Genii Series gamma counters employ simultaneous dual label counting. Simply put, both isotopes are counted at the same time, spilldown between spectra is automatically eliminated. A correction is applied to each well when running dual label assays to account for any spilldown of the high energy isotope into the lower energy window. Any two isotopes may be counted simultaneously.
For situations involving higher energy isotopes (i.e. Cr51, In111, Fe59, etc.), a feature known as crosstalk correction is employed, thereby eliminating the effects in adjacent detectors. Crosstalk makes counting high energy isotopes possible while still retaining all the precision and accuracy of a single well system. Any contributing activity which might “cross-over” from one well to the next, is monitored and subtracted out, without the need to “shut off” every other detector.
One important application for this high energy capability is in the area of P.E.T. counting. The GENESYS Genii Series gamma counters has a 4096 channel ADC, this give the Genesys Genii 1/4 KEV resolution. The isotope window is set with an upper and lower window, in 1 KEV increments, up to 1000 KEV ( 2000 KEV for the HE Models). With this option, you can set a wide window to scan unknowns for any interfering isotopes.
The GENESYS Series gamma counters offer more flexibility in assay editing than any gamma counters ever available. The Genii allows you to edit your curve post counting run to ensure the best curve fit has been chosen.
Standards, controls, and Q.C.’s may be fully compared.
Of course all editing is documented.
Being completely solid state and built with great care and precision, the GENESYS Genii Series gamma counters have a reputation for being extremely reliable and requiring very minimal servicing. We include a one year limited warranty with each GENESYS Genii gamma counter.
This warranty includes prompt and courteous response by our factory authorized service engineers*. Each service engineer is supplied with all the parts and information necessary to complete the job quickly and properly. LTI keeps an internal service team to help in quickly identifying the problem. In most cases the answer is very simple. Many times it is an applications issue rather than an actual instrument failure. Our trained service staff is ready to respond to your needs, and in most cases is able to clear up the difficulty without incurring any down time to the user.
* For customers in the U.S. LTI provides a one year on site service warranty. International customers receive a one year parts warranty and all service labor is performed by the local authorized LTI distributor.
Instrument Quality Control
The GENESYS Genii Series incorporates software containing complete programs for monitoring and documentation of all instrument parameters. the routines include: Background Check, Detector Efficiency Check, Chi-Square interpretation, Automatic Detector Gain Adjustment, Normalization of Detectors, FWHM Detector Resolution test and RAM Tests.
To Insure the accuracy of any multi-well gamma counter, background radiation levels and detector efficiencies must be monitored often, and documented to satisfy regulatory agencies. The GENESYS Genii provides simple routines for these requirements under the DAILY COUNTER CHECKS Library. The results are automatically calculated, along with a summary printout, if desired.
Detector drifts are automatically flagged. If the matching falls outside acceptable limits, recommendations for action are displayed on the screen.
Through SYSTEM DIAGNOSTICS, the GENESYS Genii can perform multiple system self-checks. All tests are automatic and potential problems are flagged and identified. Tests included are: Memory, Printer, RAM and PRAM, FWHM and CHI Square test.Through the ISOTOPE LIBRARY, the GENESYS Genii can be normalized and efficiency calculated (calibrated) quite easily, Each of the detectors are mathematically matched and a summary report can be printed for your record.
If your primary use is in nuclear medicine counting wipes or in-vitro tests such as GFR, Red Cell Volume, Shilling or Plasma Volume – then our Multi-Wiper may be better suited to your needs.
The Multi-Wiper is a multi well counter / wipe counter specifically designed for nuclear medicine, it takes the hassle out of counting wipe samples by reporting results directly in DPM and identifies what isotopes are causing a “hot” wipe to fail.
The Multi-Wiper, a one of a kind wipe counter made just for you.