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COMPARISON BETWEEN COMPUTED TOMOGRAPHY AND 99m TC- PERTECHNETATE SCINTIGRAPHY CHARACTERISTICS OF THE THYROID GLAND IN CATS WITH HYPERTHYROIDISM

Authors

  • Ines E. Lautenschlaeger,

    Corresponding author
    1. Department of Veterinary Clinical Science, Small Animal Clinic—Surgery, Justus Liebig University, Giessen, Germany
    • Address correspondence and reprint requests to Ines E. Lautenschlaeger, Department of Veterinary Clinical Science, Small Animal Clinic—Surgery, Justus-Liebig University, Frankfurter Str. 108, 35392 Giessen, Germany. E-mail: ines.lautenschlager@googlemail.com

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  • Antje Hartmann,

    1. Department of Veterinary Clinical Science, Small Animal Clinic—Surgery, Justus Liebig University, Giessen, Germany
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  • Julia Sicken,

    1. Department of Veterinary Clinical Science, Small Animal Clinic—Internal Medicine, Justus Liebig University, Giessen, Germany
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  • Sabrina Mohrs,

    1. Department of Veterinary Clinical Science, Small Animal Clinic—Internal Medicine, Justus Liebig University, Giessen, Germany
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  • Volkher B. Scholz,

    1. Institute for Theoretical Physics, ETH Zurich, Zurich, Switzerland
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  • Reto Neiger,

    1. Department of Veterinary Clinical Science, Small Animal Clinic—Internal Medicine, Justus Liebig University, Giessen, Germany
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    • These authors have contributed equally to the paper.

  • Martin Kramer

    1. Department of Veterinary Clinical Science, Small Animal Clinic—Surgery, Justus Liebig University, Giessen, Germany
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    • These authors have contributed equally to the paper.


Abstract

Scintigraphy is currently the reference standard for diagnosing feline hyperthyroidism; however, computed tomography (CT) is more widely available in veterinary practice. The purposes of this prospective study were to describe the CT appearance of thyroid glands in cats with hyperthyroidism and compare CT findings with findings from 99mTc–pertechnetate scintigraphy. Twenty-five adult hyperthyroid cats were included. Plain CT images were acquired for each cat and the following characteristics recorded for each thyroid lobe: visibility, delineation, position, attenuation, shape, and subjective size. Scintigraphic images were also acquired and the following characteristics recorded: radiopharmaceutical uptake, delineation, ectopic foci, shape, and subjective size. In CT images, thyroid lobes were most commonly found between the second and fourth cervical vertebrae, dorsolateral to the trachea. Affected thyroid lobes (based on scintigraphy reference standard) were most commonly oval and moderately enlarged in CT images. A heterogeneous attenuation pattern (isoattenuating to adjacent soft tissues with hypo- and hyperattenuating foci) was most commonly found in affected thyroid lobes. A positive correlation (P < 0.01) was identified between CT and scintigraphy for left-to-right thyroid lobe size relationship and subjective size of the larger thyroid lobe. The CT estimated mass was significantly higher (median = 148.8; range = [0;357.6]) for the more active thyroid lobe compared to the less active thyroid lobe (median = 84.6; range = [0;312.3]); (W = 154; P < 0.01). Findings indicated that CT may not reliably differentiate unilateral vs. bilateral hyperthyroidism in cats; however, CT may be a reliable alternative test for correctly identifying the more active thyroid lobe.

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