Rapid Microwave-assisted fixation of fresh tissue

• US 20020177183A1
• Filed: 05/22/2002
• Published: 11/28/2002
• Est. Priority Date: 05/22/2001
• Status: Active Grant

• Current Assignee: Ted Pella Inc.
• Original Assignee: Ted Pella Inc.
• Inventors: Giberson, Richard T., Elliott, Douglas Edwin
• Granted Patent: US 6,875,583 B2
• Time in Patent Office: Days
• US Class Current: 435/40.5
• CPC Class Codes: G01N 1/30 Staining; Impregnating ; Fixation; Dehydration; Multistep processes for preparing samples of tissue, cell or nucleic acid material and the like for analysis
• CPC Class Codes: G01N 1/44 Sample treatment involving radiation, e.g. heat
• CPC Class Codes: G01N 33/483 Physical analysis of biological material

Abstract

A rapid method of microwave-assisted formalin fixation of tissue that is described as: (a) a two-step process; (b) applicable to large (>5 mm thick) and small (<5 mm thick) tissues; (c) exposure of fresh tissue (i.e. a surgical biopsy) in a formalin solution to continuous microwave irradiation; (d) formalin circulated and cooled to maintain a constant temperature; (e) microwave-assisted formalin fixation performed at a temperature between 4° C. and 40° C.; (f) a temperature probe used to monitor fixative temperature in the cavity (g) after processing via microwave-assisted formalin fixation, the tissue can be processed by microwave methods or in an automatic tissue processor into paraffin for diagnostic evaluation. The two step process consists of a first low power microwave run followed by a second high power microwave run. An alternate embodiment of the present invention employing a one step MW oven process using other selected fixatives (glyoxal, glyoxal based and other aldehyde fixatives, alcohol, acetone, etc.)

Claims

1. A method to fixate a tissue specimen, said method comprising the steps of:

suspending the tissue specimen in a circulating fluid stream;

first irradiating the specimen with a low power microwave radiation for a first set time; and

then irradiating the specimen with a high power microwave radiation for a second set time.

2. The method of claim of claim 1, wherein the low power is less than about 250 watts.

3. The method of claim 1, wherein the high power is more than about 450 watts.

4. The method of claim 1 further comprising the step of selecting the fluid to be formalin.

5. The method of claim 1 further comprising the step of controlling a fluid depth around the tissue specimen to fully immerse the tissue specimen.

6. The method of claim 3 further comprising the step of controlling the fluid temperature in the range of about 4°

C. to 40°

C., wherein a cooling effect of the fluid prevents the microwave radiation from heating the specimen beyond the range of about 4°

C. to 40°

C.

7. The method of claim 6 further comprising the step of setting the first set time in the range of about 2-90 minutes, and setting the second set time in the range of about 2-40 minutes.

8. The method of claim 1 further comprising the step of ceasing the irradiating for a period between the first set time and the second set time.

9. A method of fixation comprising the steps of:

placing a specimen in a solution of formalin within a microwave oven;

circulating the formalin solution about the specimen;

maintaining a temperature control from about 4°

C.-40°

C.;

first operating the microwave oven in the range of about 250 watts or less power for a first preset time, thereby promoting a diffusion of formalin into the specimen without converting methylene glycol into formaldehyde within the formalin solution; and

then operating the microwave oven wattage to a second wattage of about 450 watts or more of power for a second preset time, thereby promoting the chemical conversion of methylene glycol into formaldehyde and forming a uniform chemical fixation of the tissue.

10. The method of claim 9 further comprising the step of ceasing the operating of the microwave oven between the first preset time and the second preset time.

11. A method to fixate a tissue specimen, said method comprising the steps of:

suspending the tissue specimen in a circulating fluid stream; and

irradiating the specimen with a set power microwave radiation for a set time.

12. The method of claim 11, wherein the set power is less than about 900 watts.

13. The method of claim 11 further comprising the step of selecting the fixative fluid to be selected from the group consisting of:

aldehydes, glyoxal, alcohol, acetone, Prefer™

, Preserve™

, GlyoFixx, and SafeFix II.

14. The method of claim 11 further comprising the step of controlling a fluid depth around the tissue specimen to fully immerse the tissue specimen.

15. The method of claim 12 further comprising the step of controlling the fluid temperature in the range of about 4°

C. to 40°

C.

16. The method of claim 11 further comprising the step of setting the set time in the range of about 2-120 minutes.

17. A method of fixation comprising the steps of:

placing a specimen in a fixative solution within a microwave oven;

selecting the fixative solution to be selected from the group consisting of aldehydes, glyoxal, alcohol, acetone, Prefer™

, Preserve™

, GlyoFixx, and SafeFix II;

circulating the fixative solution about the specimen;

maintaining a temperature control from about 4°

C.-40°

C.; and

operating the microwave oven in the range of about 900 watts or less power, thereby promoting a diffusion of the fixative solution into the specimen and forming a uniform chemical fixation of the tissue.