Meta-Analysis of Contrast Enhanced Ultrasound in Judging Benign and Malignant Thyroid Tumors.

In recent years, the incidence of thyroid cancer (TC) patients has gradually increased, and it ranks first among all endocrine tumors. TC has no obvious characteristics at the initial stage of onset. Thyroid tumors (TT) have formed when they are discovered, and they are easy to see when they are diagnosed. The disease is confused, so it is necessary to rely on imaging methods for tumor diagnosis. Contrast-enhanced ultrasound (CEUS), as the most commonly used imaging method in current clinical testing, is simple, safe, highly sensitive, can accurately display tumor conditions, and has high clinical value in the judgment of TC tumors. This article uses meta-analysis to select 63 published studies on CEUS to determine benign and malignant (BAM) TT to analyze and explore its clinical application value. This article understands the analysis of BAM TT and its diagnostic methods, clarifies the diagnostic efficiency of CEUS for TT, imaging methods, and imaging characteristics, and uses statistical analysis to analyze its heterogeneity. In this paper, the meta-analysis of CEUS in judging BAM TT is mainly based on references. The sensitivity, specificity, and difference of CEUS in diagnosing BAM TT are analyzed. Real-time elastography (RTE) is the comparison experiment object, and CEUS is used to compare the diagnostic efficiency, pathological results, and diagnostic efficiency of thyroid nodules in CEUS mode. The results of the study show that the nodule with higher diagnostic sensitivity is the echo feature, with a sensitivity of 97.73%, followed by the halo feature, with a sensitivity of 86.36%. In terms of diagnostic specificity, the boundary feature is the most specific. The specificity is 89.47%. In the judgment of BAM tumor nodules, the most obvious difference is the echo feature, which is as high as 14.09, followed by the acoustic halo feature, and the difference is 10.65.

1. Introduction

TC is the most common malignant endocrine tumor in clinic, and it is the most common disease with the highest incidence in endocrinology [1, 2]. TC has basically no disease information in the early stage of onset, and it often coexists with other thyroid diseases at the onset of the disease. It is easy to be misled and misdiagnosed. For this reason, it is necessary to perform imaging screening at the early stage of TT and conduct research and investigation for TT [3, 4]. CEUS, as an important clinical imaging diagnostic method, has been promoted and expanded because of its meticulous imaging observation of TT and clear tumor nodules [5, 6]. Contrast-enhanced ultrasonography stands out in the judgment of TC tumors, but the traditional ultrasound examination of thyroid nodules has a large overlap in the image of BAM thyroid nodules, which makes the clinical practice of ultrasound diagnosis of BAM thyroid nodules facing major challenges [7, 8]. Because the number, shape, and structure of blood vessels in malignant tumor tissues usually undergo significant changes, CEUS can analyze the differences between the two by observing the dynamic perfusion function of the lesion and surrounding tissues and improve the diagnostic efficiency of TT [9, 10]. Contrast-enhanced ultrasound is a technique that enhances the backscattered echo with contrast agent and significantly improves the resolution, sensitivity, and specificity of ultrasonic diagnosis. With the improvement of instrument performance and the emergence of new acoustic contrast agents, contrast-enhanced ultrasound has been able to effectively enhance the two-dimensional ultrasound images and blood flow Doppler signals of substantive organs such as myocardium, liver, kidney, and brain.

In the meta-analysis of CEUS in judging BAM TT, many scholars at home and abroad have conducted research on it and achieved certain research results. Some scholars pointed out that CEUS is the only imaging technology that can continuously observe the contrast-enhanced phase. It utilizes its unique high contrast and spatial resolution, uses the blood pool microbubble contrast agent to dynamically evaluate the tumor enhancement intensity in real time, and filter the background tissue. Highly accurate description of tumor blood vessels by observation can judge different phases of the lesion [11]. Some scholars pointed out that in CEUS, attention should be paid to the location, shape, size, number, echo, capsule, boundary, relationship with pancreatic duct and bile duct, early and late enhancement, and regression of the lesion [12]. These studies on CEUS in judging BAM TT have certain theoretical support for the realization of meta-analysis in this paper. High-quality new acoustic contrast agents should have the following characteristics: (1) high safety and low side effects; (2) microbubbles are uniform in size, less than 10 microns in diameter and can be controlled. They can freely pass through capillaries and have hemodynamic characteristics similar to red blood cells; (3) it can produce rich harmonics; (4) good stability [13].

This article mainly studies the meta-analysis of CEUS in judging BAM TT. Through systematic investigation, 63 published related literatures are selected to study them, to understand the analysis of BAM TT and their diagnosis methods, and to clarify the diagnosis of TT by CEUS. Efficiency, imaging methods, and imaging characteristics use statistical analysis to analyze their heterogeneity. In this paper, the meta-analysis of CEUS in judging BAM TT is mainly based on references. The sensitivity, specificity, and difference of CEUS in diagnosing BAM TT are analyzed. Real-time elastography (RTE) is the comparison experiment object, and CEUS was used to compare the diagnostic efficiency. In addition to conventional contrast harmonic imaging, ultrasound contrast technology also includes intermittent ultrasound imaging, energy contrast harmonic imaging, antipulse harmonic imaging, stimulated acoustic emission imaging, low mechanical index imaging, and contrast agent blasting imaging. No matter what method is used, an ultrasound device that can perform contrast must have sufficient bandwidth and high dynamic range and provide sufficient parameters [14].

2. Meta-Analysis of CEUS in Judging BAM TT

2.1. BAM TT

TT is mainly divided into two types, benign tumors and malignant tumors. Among them, the situation of benign tumors is very different from that of malignant tumors. The CEUS selected for meta-analysis is used to determine the correlation between BAM TT. In the literature, the BAM TT found and studied is shown in Table 1.

Table 1

Pathological results of TT in 63 references.

Diagnostic results	Pathologic diagnosis	Case number
Malignant (48)	Papillary thyroid carcinoma	43
	Medullary thyroid carcinoma	2
	Thyroid follicular carcinoma	1
	Undifferentiated carcinoma	1
	Sch cell carcinoma	1
Benign (43)	Nodular goiter	29
	Thyroid adenoma	9
	Focal subacute thyroiditis	2
	Atypical hyperplasia of follicular cells	1
	Chronic lymphocytic thyroiditis	2

It can be seen from Table 1 that among the 63 references cited, there are as many as 43 cases of malignant diagnosis of TC related to papillary thyroid carcinoma. In recent years, the incidence of TC has been on the rise, and due to the hidden symptoms of TC in the early stage, most patients have missed the best time for diagnosis and treatment when they use medical equipment for diagnosis and treatment. The occurrence of TC poses a great threat to the health and safety of patients. If the existence of TC can be detected and treated before the diagnosis and surgery, the deterioration of TC can be reduced, and the existence of TC can be detected and early treatment can prevent the disease from becoming cancerous. Note that most benign tumors do not become malignant, rarely relapse, grow slowly, and have little impact on the body. But this is not to say that benign tumors are not dangerous. On the contrary, some benign tumors do great harm to human body and must be paid close attention to. First, observe the location of tumor growth. When benign tumors grow in vital parts of the body and the space of these parts is quite limited, they can also cause fatal consequences.

At present, the most commonly used method for diagnosing TC is to use imaging methods to take images of the thyroid area to observe whether there are lesions in the thyroid area. Among these, the most economical imaging method is B-ultrasound, but B-ultrasound lacks specificity for the differentiation of BAM TT. It cannot clearly diagnose the BAM TT, and the misdiagnosis rate and missed diagnosis rate are relatively high. With the continuous development of science and technology, ultrasound diagnosis came into being. Because of its simplicity, safety, high sensitivity, and ability to accurately display tumor conditions, it has high clinical value in the judgment of TC tumors. However, the judgment of this technology in BAM TT is still in the exploratory stage. This article is mainly to study CEUS to judge BAM TT for meta-analysis, collect relevant research data, and use statistical methods for analysis and the diagnostic efficacy of CEUS make a judgment.

It should be noted that the scope of B-mode ultrasonography is very wide, and the preparation before examination is also different in different examination parts. (1) Abdominal examination: including liver, gallbladder, pancreas, spleen, and abdominal cavity. Generally, fasting examination should be carried out, because after eating, gas is produced in the stomach and intestines, which affects the penetration of ultrasound. The effect of fasting examination is the best. (2) Gynecological examination: you should drink water to hold your urine. When the bladder is full, squeeze open the intestinal tube to let the ultrasound better penetrate into the pelvic cavity and clearly show the normal and abnormal of the uterus and ovary. (3) Urinary system examination: you should drink more water. When the bladder is filled, the internal stones, tumors, and polyps can be better displayed. (4) Body surface tumors and lesions: they can be examined immediately without special preparation. (5) Blood vessel examination of heart and limbs, and no preparation is required.

2.2. The Diagnostic Efficiency of CEUS for TT

The application of CEUS in the diagnosis of TT has been a hot research topic in recent years. Among the 63 relevant literatures selected for meta-analysis in this article, it has positive feedback on the evaluation of the effectiveness of CEUS in the diagnosis of TT. In the differentiation of BAM TT, CEUS technology can show the exact shape of the tumor in the image. In malignant TC, the tumor needs a large amount of blood supply because of its rapid growth. Therefore, it is in the blood vessel at the initial stage. Significant changes have taken place in terms of shape, quantity, and structure. This change is different from the shape of the original thyroid gland and the shape of benign tumors. Doctors can effectively detect and analyze the differences in the blood flow dynamics of the lesion and surrounding tissues through the images displayed by CEUS, thereby improving the thyroid gland.

Regarding the diagnosis of TT by CEUS, the imaging physicians first use CEUS to obtain images of TT. The physician adds 2.4 ml of microbubble contrast agent sulphur hexafluoride to 5 ml of 0.9% normal saline, generates bubbles in the normal saline and then repeatedly shakes to form a milky suspension microbubble liquid, and injects the liquid into the patient through a needle. After focusing on the lesion, the position of the detection probe antitheft neck thyroid nodule received its backscattered echo, try to keep the observation section unchanged, start the timer, observe the dynamic image for 3 minutes, and record and confirm. After the dynamic image is obtained, the data processing software is used to process the development stage of the thyroid tumor and the surrounding tissues and take pictures of the nodules in each part. The conditions that ultrasound contrast agents must meet, including nontoxic, ultimately degradable, or excreted from the body; it has strong scattering characteristics; its diameter should be small enough to be smaller than the diameter of red blood cells (7) μm, ensure that it can enter the arterial circulation through the pulmonary capillaries, so as to achieve the imaging effect without causing embolism; it has sufficient stability and the retention time in the blood allows ultrasonic imaging to show the perfusion (enhancement) and clearance (regression) process in the tissue; it has clear damage threshold, predictability, and repeatability and can be removed quickly; easy to produce, easy to store, and suitable price.

At this time, the diversified characteristics of CEUS of nodular goiter are clearly manifested. Because the thyroid lesions are mostly located in the epithelial cells of the glandular follicles, and their enlarged growth is obvious, the arteries and veins that provide nutrition for the tumor are covered. The adenoma is squeezed to the outside of the lesion, forming a very distinctive, blood-rich surrounding blood vessel, and branching out to the periphery. The most are unilateral hypoechoic nodules. The imaging feature is fast in and slow out, with relatively strong intensity obvious. Thyroid malignant tumor tissue has abundant new blood vessels, increased branching, uneven tube diameter, increased blood flow, accelerated blood flow, and disorderly distribution. There is no capsule around the lesion, and the blood supply is unclear. The initial growth time of imaging is delayed compared with surrounding tissues. The clearance time is earlier than the surrounding tissues, and the degree of enhancement is lower than that of the surrounding tissues, so it shows the characteristics of slow in and fast out, and the degree of enhancement is weakened.

When CEUS is used for imaging diagnosis of TT, among the 63 published research literatures on CEUS to determine BAM TT selected for meta-analysis, the ultrasound imaging characteristics of thyroid nodules are shown in Table 2.

Table 2

Ultrasound imaging characteristics of thyroid nodules.

	Benign	Malignant	x 2	P
Single shot	111	26	1.029	0.322
Multiple	118	37
Low echo	40	52	96.947	<0.001
Nonhypoechoic	189	11
Blood flow	108	42	7.524	0.007
No blood flow	121	41
Calcification	54	46	55.62	<0.001
No calcification	175	17
Clear boundary	195	30	39.368	<0.001
Boundary blur	34	33
Morphological rules	69	6	10.992	0.001
Irregular shape	160	57
Lymphadenopathy	3	12	31.745	<0.001
No enlargement of lymph nodes	225	51

Therefore, it can be seen that the main distinguishing characteristics of BAM TT are (1) the tumor contour is not clear, the border contour is irregular, and it is solitary; (2) the echo of the local lesion is uneven and the strength is mixed. Accompanied by echo attenuation and combined with hemorrhagic necrosis, a liquid dark area appears in the parenchyma; (3) calcification is obvious in the lesion, and sandstone-like calcification is the most common in microcalcification; (4) the blood flow signal can be seen in the lesion, and the blood flow signal is different and chaotic. Nodular goiter is mostly based on simple diffuse goiter. Due to the repeated progress of the disease, the follicular epithelium changes from diffuse hyperplasia to focal hyperplasia, and degenerative changes occur in some areas. Finally, nodules at different stages of development appear in the gland due to the repeated alternation of long-term proliferative and degenerative lesions. The lesion is actually a late manifestation of simple goiter.

2.3. Statistical Analysis

Analysis software this study uses STATA 12.0 software for statistical analysis. The heterogeneity in the heterogeneity test can be caused by many factors, such as the researcher's different experimental design methods and test quality, different participants, or the threshold effect and other reasons. The commonly used testing methods for heterogeneity testing are statistical methods, mainly x2 test and I2 test.

x2 test

x 2 test is a common statistical method for heterogeneity testing, and the calculation formula of statistics is as follows:

Among them, W is the weight value of the i-th study, Y is the effect size of the i-th individual, M is the average effect size of all individuals, and k is the corresponding number of individuals. x2 test is actually the weighted sum of squared deviations of the effect size. Its test is widely used but the test power is low.

(2) I2 test

I 2 is the heterogeneity evaluation index, which reflects the proportion of the heterogeneity part in the total variation of the effect size. It does not depend on any unit and the size and distribution of the true effect size. Its calculation formula is

The value of I2 is in the range of 0-100%. The larger the value of I2, the greater the heterogeneity between individuals. The detection of heterogeneity is mainly to ensure whether there is a threshold effect in the diagnostic efficacy of the relevant references used for the diagnosis of BAM TC tumors by CEUS. For qualitative testing, if P > 0.05, the literature has a threshold effect, and the literature's diagnostic performance indicators can be used. The literature results are for reference. On the contrary, if P < 0.01, the literature does not have a threshold effect and its diagnostic performance the indicator is invalid and the document cannot be used as a reference.

In addition, STATA is a complete and integrated statistical software that provides its users with data analysis, data management, and professional chart drawing. It has many functions, including linear mixed model, equilibrium repetition, and polynomial proby model. In terms of classified data, it can realize parameter estimation, contingency table analysis, contingency coefficient, exact probability, epidemiological table analysis, etc.

3. Research and Analysis

3.1. Research Objects

The main content of this article is to study the related research papers of CEUS in judging BAM TT and index the references with keywords with CEUS and judging BAM TT. The scope of the index is in CNKI, Wanfang database, etc. The VIP database uses a fuzzy search strategy to search relevant documents since 2016 and manually retrieve 63 relevant documents for meta-analysis. The 63 related research papers used in this article to study CEUS to determine BAM TT were combined and tested, and the diagnostic efficacy of each index of CEUS was studied, the overall sensitivity value of the research literature combined, and the combined effect size analysis of CEUS the data results are shown in Table 3.

Table 3

Meta effect analysis of CEUS.

	Sensitivity	Specificity	Positive likelihood ratio	Negative likelihood ratio	Odds ratio
CEUS	0.86	0.88	5.91	0.18	36.3
	(0.82-0.89)	(0.85-0.9)	(3.89-9)	(0.13-0.25)	(18.53-71.13)

3.2. Research Standards

The inclusion criteria of the research literature are (1) the relevant literature published after 2016 on the diagnosis of BAM TT by CEUS is prospective or retrospective; (2) the selected literature sample size is greater than 20 cases; (3) the diagnostic criteria for TT is CEUS imaging; (4) references with complete information such as pathology reports, conference papers, abstracts, and conclusions; (5) four grids for the diagnosis of thyroid nodules by CEUS can be obtained from the references table data.

4. CEUS to Judge BAM TT Meta-Analysis Experimental Research Analysis

4.1. Sensitivity, Specificity, and Difference of CEUS in Diagnosing BAM TT

In this article, in the meta-analysis for judging BAM TT by CEUS, the pathological results of thyroid nodules studied in 63 references are used as reference objects, and the sensitivity, specificity, and difference of each symbol of tumor nodules under CEUS are made. Analysis and research, the results are shown in Figure 1.

Figure 1

Sensitivity, specificity, and difference of contrast-enhanced ultrasonography in the diagnosis of BAM TT.

It can be seen from Figure 1 that in the diagnosis of BAM thyroid nodules by CEUS, the nodule with higher diagnostic sensitivity is the echo feature, with a sensitivity of 97.73%, followed by the acoustic halo feature, with a sensitivity of 86.36. %. In terms of diagnostic specificity, the boundary feature is the most specific, with a specificity of 89.47%. In the judgment of BAM tumor nodules, the most obvious difference is the echo feature, which is as high as 14.09, followed by the acoustic halo, the difference is 10.65.

4.2. The Diagnostic Efficacy of Two Imaging Methods

Among the selected 63 cases of CEUS to determine BAM thyroid tumor meta-analysis, there are many comparisons of CEUS imaging with other imaging methods to prove the superiority of CEUS in the diagnosis of BAM TT. This paper selects real-time elastography (RTE) as the research literature that compares the diagnostic efficiency of the experimental object with the CEUS and summarizes the diagnostic results studied. The data results are shown in Figure 2.

Figure 2

Analysis of diagnostic efficacy of two imaging methods.

It can be seen from Figure 2 that in the research comparison of real-time elastography and CEUS for the diagnosis of BAM TT, CEUS is far superior to real-time elastography due to its superiority in performance, in terms of accuracy, sensitivity, and difference. Positive predictive value and negative predictive value are more mature than real-time elastography, which is helpful for doctors to make better judgments on the BAM tumor nodules in the image.

Besides, there are many ways to observe deformation. According to the obtained image, it may be one-dimensional, two-dimensional, or three-dimensional, or just a single value, or video or an image. In most cases, the results presented to the operator are accompanied by a conventional image showing the distribution of different hardness in the tissue. The classification of elastic imaging technology mainly depends on the way of observing deformation. At present, elastic imaging technology using ultrasound and nuclear magnetic resonance imaging occupies a dominant position. There are many other elastic imaging methods, including the application of optical or mechanical pressure sensors.

4.3. Pathological Results of Thyroid Nodules in CEUS Imaging

In the diagnosis of BAM TT by CEUS, there are also documents that judge tumor nodules based on the CEUS mode. This article selects this case to analyze the pathological results of thyroid nodules in the CEUS mode. The pathological diagnosis of tumor nodules is divided into two groups, small tumor nodules (0.5 cm < maximum diameter ≤ 1 cm) and large tumor nodules (maximum diameter > 1 cm). The pathological diagnosis results are shown in Table 4.

Table 4

Pathological results of thyroid nodules in CEUS imaging.

		Uniform low enhancement	Early low enhancement	Uneven low enhancement	Equal enhancement	Annular enhancement	High enhancement
Thyroid nodules with maximum diameter > 1 cm	Benign	0	0	11.5	19.2	23.1	46.2
	Malignant	33.3	13.3	41.3	12	0	0
0.5 cm < maximum diameter ≤ 1 cm thyroid nodule	Benign	5.6	0	0	22.2	11.1	61.1
	Malignant	33.3	14.3	4.8	47.6	0	0

It can be seen from Figure 3 that among the pathological results of thyroid nodules in CEUS mode, in the small tumor nodule group, the benign tumor nodules have the strongest pathological characteristics in the high-enhancement mode, accounting for 46.2%, and their malignant nodules tumor nodules have the strongest pathological features in the uneven low-enhancement mode, 41.3%. Among the large tumor nodules group, the benign tumor nodules have the strongest pathological features in the high-enhancement mode, which is 61.1%, and their malignant tumor nodules the strongest pathological feature was 47.6% in the iso-enhancement mode.

Figure 3

Pathological results of thyroid nodules in CEUS imaging.

4.4. Effectiveness of Pathological Diagnosis of Thyroid Nodules with CEUS

The meta-analysis of the CEUS mode in the diagnosis of pathological diagnosis of thyroid nodules can be used for data collection in selected references. Figure 3 is the analysis of the pathological results of the thyroid nodules in the CEUS mode, which can judge tumors the BAM characteristics of nodules. Figure 4 is an analysis of the diagnostic efficiency of BAM pathology, and its sensitivity, difference, positive predictive value, and negative predictive value are studied and analyzed. The results are shown in Figure 4. Scanning has little significance in distinguishing benign and malignant lesions. Most benign and malignant parenchymal nodules have low function relative to the surrounding normal gland tissue. Therefore, cold nodules are rarely specific, and the overlapping uptake of radionuclides by the surrounding normal gland tissue can miss the diagnosis of small nodules. Many thyroid cancers can take TC, so there are still some cancer cases in hot nodules.

Figure 4

Pathological diagnosis of thyroid nodules by contrast-enhanced ultrasonography.

It can be seen from Figure 4 that in the analysis of the effectiveness of CEUS in the diagnosis of BAM tumor nodules, the sensitivity of the diagnosis feature with or without a complete enhancement ring is the strongest, and its negative predictive value is also the strongest. In terms of specificity, the gradient enhancement mode is the strongest, and the positive predictive value is the late enhancement mode the clearest.

5. Conclusions

CEUS has high sensitivity and specificity for judging BAM TC tumors and has high clinical diagnostic value for TT, and it is worthy of clinical application. In this paper, 63 references are selected for meta-analysis of CEUS to determine BAM TT. It is also the most economical but highly sensitive imaging technology that provides a good basis for early detection and treatment. The development of CEUS in the diagnosis of BAM TC tumors will be further enhanced with the development of science and technology, and its future application in the preclinical stage is expected.