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Microwave ovens: Advice for new users
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Microwave ovens: Advice for new users


Can someone experienced with a microwave processor give advice?

Answer 1.

In making your final decision about the purchase of a laboratory microwave oven, you may also find it helpful to use some simple microwave calibration tools to determine objectively if a particular microwave oven will suit your specific needs.

These tools are quick and simple assessments that show you just how evenly your clinical specimens will be heated in a microwave oven.

1. Neon Bulb Array.
Because our eyes can not sense microwaves, they appear invisible to us.  A Neon Bulb Array is a tool that indirectly shows the nonuniformity of microwave power in a microwave oven.  In principle, microwave irradiation increases the kinetic energy of the neon gas molecules.  The neon bulbs glow orange where the microwave power is high enough to ionize the gas molecules (~5 mw/cm2).  The neon bulb array is useful for determining the areas of uniform power, cycle time, and magnetron warm-up time in a microwave oven.

2. The Agar-Saline-Giemsa tissue phantom.
Agar-Saline-Giemsa tissue phantoms are used to simulate the size, shape, and absorbance characteristics of biological specimens to verify that the microwave oven will uniformly heat the specimens.

Small agar phantoms (1 cm x 0.5 cm2 blocks or 2 cm diameter by 0.3 cm thickness discs) that contain 0.002% commercial Giemsa stain are added to molten 2% agar in 0.9% sodium chloride.  The Giemsa dyes respond to microwave heating by showing different colors at different temperatures.  When ASG tissue phantoms are irradiated in an optimized microwave cavity, they show a uniform color change.

These tools have been described and published in peer-reviewed journals since 1990 and have been independently verified by other laboratories.  They are commercially available or you can prepare them yourself.

Brief list of references

  1. Login, G. R., N. Tanda, and A. M. Dvorak. Calibrating and standardizing microwave ovens for microwave-accelerated specimen preparation.  A review. Cell Vision 3: 172-179, 1996.
  2. Login, G. R., and A. M. Dvorak. The Microwave Toolbook. A Practical Guide for Microscopists. Boston: Beth Israel Hospital, 1994.
  3. Login, G. R., J. B. Leonard, and A. M. Dvorak. Calibration and standardization of microwave ovens for fixation of brain and peripheral nerve tissue. Companion to Methods Enzymol 15: (in press), 1998.
  4. Login, G. R. The need for clinical laboratory standards for microwave-accelerated procedures. J Histotechnol 21: 1-3, 1998 (Editorial).

Gary Login, Assistant Professor of Oral Pathology
Beth Israel Deaconess Medical Center

Answer 2.

My experience thus far is purely from a vendors view.
The benefits so far:

  1. You can process without xylene
  2. Turnaround can be minutes as opposed to hours.
  3. cost savings about 1/5 of a traditional processor.
     (Not counting the reagent savings)
  4. Loads of up to 90 cassettes can be processed in one run.

Dawn  M. Truscott, HT(ASCP)
Product Specialist
Carl Zeiss, Inc.

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