Improved prediction of thyroid lobar mass from parameters obtained by routine thyroid scintigraphy

Estimation of thyroid mass both from parameters derived from thyroid scintigraphy and clinical palpation for purposes of therapeutic dosimetry has not been tested for accuracy. To more precisely determine thyroid mass 90 thyroid lobes from 45 autopsies without history of thyroid disease were studied. Specimens were dissected free of nonthyroidal tissue and assessed for volume, maximum depth (D), width (W), length (L) and mass (M). Using a linear regression model and applying known lobar depth, the most accurate formula to predict true lobar mass (in grams) was 4.9D + 0.07L2W-2.3 (in cms). Length and width would be obtainable in vivo from routine scintigraphic measurements (in cm) and depth would be most accurately determined by ultrasound. For most clinical circumstances where lobar depth is unknown we found the best formula for mass (g) to be 0.1L2W (in cm).