Functional analysis of magnetic resonance studies of the heart.

To calculate left ventricle volumes and ejection fraction, magnetic resonance images (MRI) were acquired in an oblique position in end-diastole and end-systole. The ejection fraction values were compared with results of gated blood pool studies with 99mTc-labelled erythrocytes (correlation coefficient 0.8). Determination of regional wall motion was also possible. A method for acquiring sequences of 16 images per heartbeat was developed. It allows the detection of disturbances of wall motion by using Fourier analysis.

The influence of elevated iodide supply on the autonomously functioning thyroid gland.

A pharmacokinetic two-compartment model of iodine metabolism has been established on the basis of data from the literature and our own experimental investigations. By this model it is possible to estimate the effects either of prolonged elevation of iodide supply or of a single administration of a high dose of inorganic iodide in the presence of autonomously functioning thyroid tissue. Prolonged elevation of iodide supply in regions of iodine deficiency will cause manifest hyperthyroidism in many cases of thyroidal autonomy (cases with facultative hyperthyroidism). The administration of a single high dose of iodide, as it is proposed for the situation of an accident in a nuclear power station (100 mg NaI) in order to reduce the radiation burden to the surrounding population, carries almost no risk in cases of thyroid autonomy.

Clinical significance of endogenously labelled thyroid hormones in the diagnosis of thyroidal autonomy.

The clinical value of the determination of 123I concentration in serum 48 hrs after tracer administration (123I)48 is investigated with special regard to thyroidal autonomy. Serum radioiodine concentration, thyroid radioiodide uptake at 4 and at 48 hrs were measured in 74 healthy subjects and patients with simple goiter, in 36 patients with thyroidal autonomy (diagnosis by thyroid suppression test), and in 20 hyperthyroid patients. 83% of the patients with elevated radioiodine concentration belonged to the group of thyroidal autonomy. The product of radioiodine concentration and thyroid radioiodide uptake is a much better parameter. 95% of the patients in which this product was elevated, belonged to the autonomy group (5% diagnostic error). Also in the control group the diagnostic error was 5%. The combination of (123I)48 with the result of the TRH-test is very useful in excluding thyroidal autonomy, if (123I)48 is normal and the TRH-test is positive (100% of the patients have regulated thyroid glands). 94% of the patients having elevated (123I)48 and a negative TRH-test belonged to the group of thyroidal autonomy. A very useful combination for the diagnosis of borderline hyperthyroidism is the determination of the product of (123I)48 and the uptake48 together with the pulse rate or fine tremor of the fingers (or TRH-test). The results suggest that the determination of (123I)48 is a very good parameter of thyroidal autonomy beside the thyroid suppression test. It may be used alone for the diagnosis of thyroidal autonomy if the suppression test is contraindicated. In the diagnosis of borderline hyperthyroidism its determination makes the suppression test unnecessary in many instances.

[Determination of the serum concentration of radioiodine with 123I]. / Messung der Radiojodkonzentration im Serum mit 123J.

Though the half-life of 123I is much shorter than that of 131I, the determination of the radioiodine concentration 48 hrs after tracer administration (123I)48h can be done with the same precision. This precision is achieved by the fivefold dose given to the patient and the fourfold specific count rate. In 36 euthyroid patients with thyroidal autonomy the 123I concentration in serum was determined 48 hrs after tracer administration and was compared with the values obtained in a control group (n = 74). The diagnosis of thyroidal autonomy can be supported by the measurement of (123I)48h. The combination of (123I)48h and thyroidal radioiodine uptake seems to make the diagnostic decision more precise.

Thyroid hormone concentrations in dialysate during hemodialysis in children.

Thyroxine (T4) concentration in dialysate in the course of hemodialysis was determined in 15 children. Concentrations were measured by a modified radioimmunoassay. During hemodialysis there was a slight increase in T4 concentration. At the end of hemodialysis T4 concentration was about 50% higher than soon after the onset of hemodialysis. The loss of T4 into dialysate during hemodialysis was 19.2 microgram; the loss of T3 was less than 75 ng. The amount of the daily loss of thyroid hormones into dialysate was found to be in the range of normal urinary excretion. The lowering of serum thyroid hormone concentrations in children on hemodialysis cannot be explained by the loss of hormones into dialysate.