Comparative thyroid gland volume by two methods: Ultrasonography and planar scintigraphy

Summary

Background:

Knowledge of thyroid gland volume plays a key role in the treatment of thyroid diseases by radioactive iodine 131I. Radioiodine therapy is a routine procedure of treatment hyperthyroidism for over 50 years.

Material/Methods:

Today modern diagnostic has a number of medical diagnostics instruments whose using to estimate of thyroid volume. Undoubtedly these method we can include a ultrasonography (US) and planar scintigraphy (PS) whose characterized by noninvasive.

Results/Conclusions:

The aims of this papers is evaluate of thyroid volume on the basis of method ultrasonography and planar scintigraphy.

Background

Knowledge of thyroid gland volume plays a key role in the treatment of thyroid diseases by radioactive iodine 131I [1]. Radioiodine therapy is a routine procedure of treatment hyperthyroidism for over 50 years [2].

Today modern diagnostic has a number of medical diagnostics instruments which are used to estimate of thyroid volume. Undoubtedly these method we can include a ultrasonography (US) and planar scintigraphy (PS) which are characterized by noninvasive.

Ultrasonography is a primary imaging method of thyroid. The study is a safe, cheap and generally available. It provides information about thyroid size and structure [2,9,10]. The method makes the most of ultrasonic waves which are penetrating deep into the neck and then record the returning waves-bounced.

Radioisotope methods obtains information not only thyroid size but also on it’s a morphology and function. The source of this information are quanta gamma whose the most commonly used emitters are 131I and 99mTc [4–6].

The aims of this papers is evaluate of thyroid volume on the basis of methods: ultrasonography and planar scintigraphy.

Material and Methods

All patients who were found to have hyperthyroidism at 109 Military Hospital were examined by US and PS. Patients (40 women) diagnosed in this period were qualified to radioiodine therapy.

Ultrasonography

The study was realized on a apparatus SANOACE PICO MEDISON with a head linear part 7.5 MHz frequency. In study patients had a toss head. During the study measured the maximum dimensions of thyroid panels: length (L), width (W) and thickness (T). Additionally it evaluated echogenicity as well as to states a presence of goiters changes in the glandular tissue.

Thyroid volume was calculated using Braun [7] expression:

$${\text{V}}_{\text{US}}=0.479\cdot L\cdot W\cdot T$$ (1)

For in the each lobes was calculated its volume and then thyroid lobes volume added together:

$${\text{V}}_{\text{Thyroid}}={\text{V}}_{\text{RL}}+{\text{V}}_{\text{LL}}$$ (2)

Planar scintigraphy

The study was realize on gamma camera TH/33 MEDISO POLSKA company with HEGP (High energy general purpose) collimator, often with a special design to reduce the distance between the collimator face and the thyroid, and a computer matrix size of 128×128 pixels are used. Acquisition time of a 5 minutes after tracer administrations (24 h) about 4 MBq activity, energy windows set to 131I. Thyroid volume was calculated using Interview program using Himanka and Larson expression [11]. ROI (area of interest) was set manually for each patient.

$${\text{V}}_{\text{PS}}=0.33\cdot A^{3/2},\text{A}-\text{thyroid\hspace{0.17em}area}$$ (3)

Statistics

The analysis was performed STATISTICA 6.0. Calculated arithmetic mean, standard deviation (SD), mode, median, minimum and maximum values, determined correlation between V_US vs. V_PS.

Results

Both variables had normal distribution tested Chi-squared method. Table 1 shows the results of thyroid volume for both method.

Table 1.

The statistic results of thyroid volume for ultrasonography (US) and planar scintigraphy (PS).

Variable	Mean	Median	Mode	Minimum	Maximum	SD
US	28.98	27.40		11.41	54.54	11.41
PS	30.62	26.33	13.90	11.78	62.55	14.09

A average volume of thyroid gland obtained by US was 28.98 ml, for PS 30.62 ml.

Figure 1 shows linear dependence V_US vs. V_PS (r=0.94).

Figure 1.

The relationship between two methods of evaluating an thyroid gland volume: ultrasonography and planar scintigraphy.

Discussion

Ultrasonography is a essential study of thyroid gland that only limitation is the inability of showing gland located under breastbone notch. The exact calculation of thyroid volume is a essential parameter for calculated of therapeutic radioiodine dose [8].

In the literature there are reports which stressed usefulness both methods (US and PS) to assess a thyroid volume and thus to calculated radioiodine dose.

Lucas [1] presents usefulness of US in the calculated therapeutic radioiodine dose. In conducting the study on 121 patients in 74 (98,6%) states the usefulness effectiveness of treatment of hyperthyroidism by radioactive iodine ¹³¹I. In the remaining group of 13 patients showed normal function thyroid, at 61 patients appeared hypothyroidism after therapy. Washe [12] shows that thyroid volume calculated by Himaka expression is on average 33% higher that the values obtained by US method. Isselt [13] in compared thyroid volume four methods: US, PS, SPET (Single Photon Emission Tomography) and MRI (Magnetic Resonance Imaging). In study included 25 patients (3 man and 22 women) whose diagnosed with GB (Graves Basedov) disease who referred to radioiodine treatment. The mean thyroid volume were: 26.1 ml, 35.2 ml, 29.6 ml and 33.9 ml. Correlation coefficient of PS vs. MRI (r=0.61) was less than the ultrasound vs. MRI (r=0). In the present work compared thyroid volume gland using US I PS method. The results obtained Himaka expression proved to be comparable with ultrasound. Measurements based on the interpretation of scintigraphy study are performed by the error resulting from the lack of measurement of the depth and precision mark of the thyroid gland area. The resulting of correlation ratio is comparable to obtained by Isselt for US vs. MRI.

Accuracy also depends on the behavior of the measurement geometry: the distance detector neck. Error interpretation of the results of ultrasound is directly related both to the characteristics of the person conducting the test, its experience and its manual capacity.

Conclusions

1. There is a correlation between thyroid volume obtained by US vs. PS

2. The impact on the outcome of the skills contractors.