The Use of Power Doppler Ultrasound in the Differentiation Of Benign From Malignant Thyroid Nodules in Duhok – Kurdistan Of Iraq

Maysaloon Shaman Saeed
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Keywords : Thyroid, Nodule, Doppler, Power, Vascularity, Ultrasound.
Medical Journal of Babylon  13:3 , 2016 doi:1812-156X-13-3
Published :31 December 2016

Abstract

In the last decade, nodular diseases of the thyroid gland has become an important subject for most of the surgeons and clinicians, trying to reach a proper early detection yielding a preferable outcomes, the study done to evaluate the diagnostic performance of Power Doppler sonography in detecting the nature of thyroid nodules, correlated with fine needle aspiration (FNA) results, helping in the differentiation of their benign from malignant behavior, a total of 200 patients with thyroid nodular disease, age ranging (18 – 69) years, (176 females, 34 males) referred to the radiological department in Azadi teaching hospital, examined by grey scale, color and power Doppler ultrasound; correlation with FNA was done to all nodules, Doppler Ultarsonography is helpful in comparison with FNA results; in the diagnosis of the nature of thyroid nodules, peripheral Doppler vascular arrangements seen more in the benign nodules while central distribution was seen more in the malignant ones.

Introduction

Thyroid nodular disease has relatively high frequency in the general population with prevalence of (4-7%) by palpation alone, and (13-67%) by sonographic evaluation [1,2]. In addition to Conventional Ultrasound , the Power Doppler system is a color mapping technique used to get the strength of the Doppler signal coming from the flow rather than the frequency shift of the signal , enables proper estimation of the blood flow based on the number of blood cells regardless of their velocity, so it is considered more sensitive than conventional color Doppler in the imaging of the small vessels of the tumors [3,4] , the use of conventional and Doppler sonography is more widely applied for the assessment of suspected malignant lesions (see figure 1 ) [2-6].

Materials and methods

A cross-sectional study was performed in which 200 patients were recruited whom referred from physicians and consultants in  Azadi Teaching Hospital, diagnosed with different types of thyroid nodular disease. The range of age for the patients was (18 -69) +_ 7.8 years and their mean was (43.9) +_ 8.9, conducted from June 2014 till October 2015.
All the patients were examined, by two well known specialized radiologists with experience of several years in Doppler and ultrasound examinations using the available Siemens Acuson X300 real time scanner with VF13-5MHz linear array transducer multidirectional scan; axial, coronal and longitudinal  were  done for  both lobes and isthmus with caudal angulation of the probe in the suprasternal notch to identify any retrosternal extension of the gland. With proper setting of the machine to avoid artifacts and noise, Grey scale, Color Doppler, as well as Power Doppler examination were done, results were all correlated with the results of fine needle aspiration done by two known specialized pathologists. Unfortunately it was not possible to use biopsy as gold standard as many of the patients, preferred to go outside the country and were unavailable to follow up.
Inclusion criteria: nodules more than 1 cm in size .
Exclusion criteria: purely cystic lesions.
The pattern of vascularity  arranged relative to each nodule  was classified  as (Avascular, Predominantly peripheral vascular, Predominantly central vascular) patterns of vascularity [4-10],  fine needle aspiration was done for all detected nodules by specialized pathologists, using 10 mm plastic syringes by a specialized histopathologist under ultrasonic guidance, with the use of 22-25 gauge needles, all results were compared with the Power ultrasonic findings.
      Data collected using Microsoft Excel 2010 sheet, converted into SPSS version 22    statistical package .Fisher’s exact test was used throughout with a significance level of P < 0.05.
Calculations of measures of validity (sensitivity, specificity, predictive values, diagnostic accuracy and likelihood ratios) were done according to Petrie and Sabin [11].




Results

A total number of 200 nodules were examined, 176 of them were in females and 34 in male populations, the age range was between (18 – 69) +_ 7.8, with the mean age of 43.9% +_ 8.9 were seen.

Discussions

During the past decade the application of Ultrasonography has greatly increased in the differential diagnosis of benign and malignant tumors. Several authors have claimed that Doppler sonography helps considerably [12,13], while others consider this method of limited diagnostic value [14, 15]. In our study females formed the vast majority of the patients examined (four times more than males), and these results were in agreement with [4,15]. In our study, the nodular vascular signals were absent in 27% of benign nodules, these results were comparable with those of [4,5,16,17] and it was absent in 3.4 % of malignant ones which was lesser than those of [4,5], (about 22%) of the total number in both, and this result indicates that absence of vascularity did not exclude malignancy completely, the same that found in [4,5,16,19]. We noticed moderate values of sensitivity and NPV, and hence of the total accuracy of the Avascular pattern in detecting the benign nature of the nodule, this is probably because the term Avascular means deficient vsacularity both centrally and peripherally and is more related to the examiner consideration ,we hope in the next studies to have a more detailed and exact points to consider the nodule as non vascular with confidence. Peripheral type of vascularity was more common in benign nodules, in our study, these results were comparable with those found by [4, 5, 15, 16, 17] and showed well sensitivity and specificity vales, as well as PPV , the NPV wasn’t so high because the nodules size we took were more than 1 cm, while in the study done by [6,9] we noticed more values because the nodules included in their studies were more than 2.5 cm , this reflects that the more the size of the nodule increased, the more properly oriented peripheral distribution of vascularity it has, nearly equal results seen in [5, 14, 15, 19], and slightly lower results seen in [4, 18, 19, 20]. Central type of vascularity was more common in malignant thyroid nodules, also seen in [15, 16, 17, 18, 19, 20] and proved to be highly valuable in predicting malignant thyroid nodules, show in 81% sensitivity, 98% specificity, 94% positive predictive value and 93% negative predictive value, these results were more than those found by [4, 5,15,18, 19, 20] .This is probably because in the previous mentioned studies the sample volume was lesser. The likelihood ratio of a positive test proved to be highly valuable in all the patterns seen, which gives an impression of an accurate, delicate information s, with great power of the ultrasound results in comparing the pretest from post test patients. Other more detailed studies regarding the malignant nodular behavior and systemic as well lymph node distribution, are hoped in the future.

Conclusions

Power Doppler sonography, although it is less helpful in few non vascular nodules, might contribute in the differential diagnosis of thyroid nodules and helping the physician in reaching exact diagnosis and treatment.

References

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