[Doppler evaluation of thyroid hemodynamics after intravenous administration of contrast media]

Duplex Doppler ultrasound allows the evaluation of thyroid gland vascular flow by spectral analysis assessment. The objective of this prospective study was to employ Doppler ultrasound to evaluate the possible functional changes produced in normal subjects following intravenous iodized contrast medium injection.

The study was performed on 30 non-consecutive subjects, enrolled according to some inclusion criteria: male gender, age ranging between 19 and 70 years, absence of chronic liver disease, absence of thyroid disease, absence of sonographic changes in the thyroid gland, negative history for recent intravenous contrast medium administration. All patients were scheduled for a contrast-enhanced CT study. A non-ionic contrast medium (iomeprol) was employed at 350 mgI/mL concentration, 130-140 mL volume, and 2-4 mL/sec. injection rate. The Doppler ultrasound examination was carried out immediately before and about 30 minutes after the CT study. The systolic velocity, diastolic velocity, the resistive index, and the pulsatility index were measured at the level of one of the four thyroid arteries.

In most cases a slightly increasing trend of the four parameters considered was noted but none of these showed a statistically significant change. The mean systolic velocity was of 33 cm/sec. in the basal measurement and of 39 cm/sec. in the post-contrast measurement. The variation was positive in 17 cases, negative in 12, and absent in 1. The mean diastolic velocity was of 13 cm/sec. in the pre-contrast evaluation and of 14 cm/sec. in the second evaluation. The change was positive in 14 cases, negative in 12, and absent in 4. The mean resistive index was of 0.55 in the basal analysis and of 0.59 in the post-contrast one. The variation was positive in 20 patients, negative in 9, and absent in 1. The mean pulsatility index was of 0.99 in the basal measurement and of 1.14 in the second measurement. The change was positive in 23 subjects, negative in 5, and absent in 2.

Our series shows that no significant change in Doppler spectral analysis of thyroid flow is evident after administration of iodized contrast media, at least in euthyroid subjects and with the contrast doses and the examination intervals employed in our study. Doppler ultrasound is confirmed as an accurate and objective procedure in the evaluation of thyroid gland flow and may represent a useful tool in functional studies, as well as clinical applications in the assessment of thyroid gland disorders.