Thermographic studies of phantom and canine kidneys thawed by microwave radiation.

Abstract

Whole organs, such as kidneys, must be thawed quickly and uniformly to prevent damage during thawing due to excessive heating. Electromagnetic heating with microwaves thaws the kidneys quickly but frequently produces "hot spots" with heat damage. To study heat damage, phantom gelatin kidneys with different dielectric constants and canine kidneys perfused with 12.5% glycerol, ethylene glycol, or dimethyl sulfoxide before freezing were microwave thawed, and the interior temperature was measured by thermography. Phantom kidneys were thawed free standing and canine kidneys were either free standing or packed in a gel mixture. Both phantom and canine kidneys were split symmetrically and separated with a sheet of Styrofoam to facilitate immediate separation and evaluation of the halves after thawing (approximately 3 sec). All the phantoms, regardless of dielectric properties, had areas less than 0 degrees C or greater than 37 degrees C after thawing. The free-standing canine kidneys and the gel-packed ethylene glycol-perfused kidneys had frozen areas (less than 0 degrees C) and hot spots (greater than 37 degrees C). However, glycerol- and dimethyl sulfoxide-perfused kidneys packed in gel before thawing had no areas less than 0 degrees C or greater than 37 degrees C. Altering the geometry from a "kidney shape" to a cylindrical shape with increased volume improved the uniformity of thawing and was more effective than altering the dielectric constant over the range evaluated.

AI evidence extraction

Main findings

Microwave thawing produced non-uniform temperature distributions with frozen areas and/or hot spots in all phantom kidneys and in free-standing canine kidneys and gel-packed ethylene glycol-perfused kidneys. Glycerol- and dimethyl sulfoxide-perfused canine kidneys packed in gel showed no areas <0°C or >37°C after thawing. Changing organ geometry to a larger cylindrical shape improved thawing uniformity more than changing dielectric constant over the evaluated range.

Outcomes measured

• Thawing uniformity assessed by interior temperature distribution (thermography)
• Presence of frozen areas (<0°C) after thawing
• Presence of hot spots (>37°C) after thawing

Limitations

• No microwave frequency, power, or dosimetry (e.g., SAR) reported in the abstract
• Sample size not reported
• Outcome focused on temperature distribution/thermal damage risk rather than biological endpoints beyond heating
• Animal/phantom model; generalizability to other organs or clinical settings unclear from abstract

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": "microwave radiation (electromagnetic heating)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Phantom gelatin kidneys and canine kidneys (perfused with 12.5% glycerol, ethylene glycol, or dimethyl sulfoxide)",
    "sample_size": null,
    "outcomes": [
        "Thawing uniformity assessed by interior temperature distribution (thermography)",
        "Presence of frozen areas (<0°C) after thawing",
        "Presence of hot spots (>37°C) after thawing"
    ],
    "main_findings": "Microwave thawing produced non-uniform temperature distributions with frozen areas and/or hot spots in all phantom kidneys and in free-standing canine kidneys and gel-packed ethylene glycol-perfused kidneys. Glycerol- and dimethyl sulfoxide-perfused canine kidneys packed in gel showed no areas <0°C or >37°C after thawing. Changing organ geometry to a larger cylindrical shape improved thawing uniformity more than changing dielectric constant over the evaluated range.",
    "effect_direction": "mixed",
    "limitations": [
        "No microwave frequency, power, or dosimetry (e.g., SAR) reported in the abstract",
        "Sample size not reported",
        "Outcome focused on temperature distribution/thermal damage risk rather than biological endpoints beyond heating",
        "Animal/phantom model; generalizability to other organs or clinical settings unclear from abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave thawing",
        "electromagnetic heating",
        "thermography",
        "kidney",
        "phantom model",
        "canine",
        "hot spots",
        "cryobiology",
        "dielectric constant",
        "geometry"
    ],
    "suggested_hubs": []
}

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