SPECT/CT imaging in large multinodular goiters and poorly defined nodular thyroid disease

1279 Objectives Assessing the additional impact of SPECT/CT images in patients with large nodular goiters with or without intrathoracic extension or nodules difficult to define in planar images. Methods Forty-five patients with nodular goiter evaluated with thyroid scintigraphy since 2008 to date that underwent SPECT/CT imaging because of intrathoracic extension or poorly defined nodules were included in the study. Twenty-three cases were submitted for therapeutic 131I dose calculation. Twenty-four had a diagnosis of intrathoracic multinodular goiter (MNG), 4 had grade III-IV MNG without prior evidence of intrathoracic extension, 4 had echographic nodules not visualized on the planar images and 13 had nodules with not clearly defined uptake. Planar images were obtained 30 minutes after i.v. injection of 185 MBq of 99mTc-pertechnetate using a pin-hole collimator. SPECT/CT images were acquired using an Infinia Hawkeye 4 gamma camera, in a 180° anterior orbit in 32 steps, selecting a 128 x 128 matrix with a pixel size of 4.42 mm, immediately followed by low-dose CT (140 keV, 2.5 mA, 1.9 pitch). SPECT images were processed with OSEM in a Xeleris 2 workstation. CT-based attenuation correction was always performed. Results In all patients the anatomic information provided by CT images allowed a more precise definition of the glandular and nodular size. In 15 patients (43%) the glandular size by SPECT-CT was higher than that observed in the planar images (most of them because of intrathoracic growth not seen in planar images), in 13 patients (37%) new nodules were detected (7 with decreased and 6 with increased uptake) and a change in the pattern of nodular uptake was observed in 2 patients (from cold to hot in 1 case and the reverse situation in the other). An improved definition of the nodular uptake comparing to planar images was evident in 8 patients. Tracheal compression was detected in 19 patients with a minimum diameter of 8 mm. In 7 patients submitted for radioiodine dose calculation a surgical indication was suggested as the best therapeutic option after SPECT/CT images. Conclusions SPECT-CT is an unusual indication in the assessment of nodular thyroid disease, although with important impact in specific clinical situations. In patients with large MNG, particularly those with intrathoracic extension, an increase of the glandular volume and/or the presence of new nodules can be detected in more than two thirds of the cases. In patients sent for radioiodine dose calculation the accurate additional information obtained with SPECT/CT images about the volume of the gland and the tracheal diameter provides a one-stop-shop alternative to avoid the need for further studies allowing a more precise definition of the calculated dose. A change in management from medical to surgical can also be determined by SPECT/CT images in a significant number of cases. RESEARCH SUPPORT: No