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10.1245/ASO.2005.03.062
Annals of Surgical Oncology 12:152-160 (2005)
© 2005 Society of Surgical Oncology
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Original Article

Electrical Impedance Scanning of Thyroid Nodules Before Thyroid Surgery: A Prospective Study

Alexander Stojadinovic, MD1, Scott I. Fields, MD2, Craig D. Shriver, MD1, Sarah Lenington, PhD3, Ron Ginor, MD3, George E. Peoples, MD1, Henry B. Burch, MD1, Tamar Peretz, MD4, Herbert R. Freund, MD5 and Aviram Nissan, MD5

1 Department of Surgery, General Surgery Service, Walter Reed Army Medical Center, 6900 Georgia Avenue, N.W., Washington, DC 20307, USA
2 Department of Radiology, Hadassah University Hospital, Mount Scopus, Jerusalem, Israel, 91240
3 Mirabel Medical, 9020-1 Capitol of Texas Highway, Suite 250, Austin, Texas 78759, USA
4 Department of Oncology, Hadassah University Hospital, Mount Scopus, Jerusalem, Israel, 91240
5 Department of Surgery, Hadassah University Hospital, Mount Scopus, Jerusalem, Israel, 91240

Correspondence: Address correspondence and reprint requests to: Alexander Stojadinovic, MD; E-mail: alexander.stojadinovic{at}na.amedd.army.mil.


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Background: Electrical impedance scanning (EIS) is a novel imaging technique based on differential electrical conductivity and capacitance of malignant and normal human tissues. The aim of this study was to evaluate the accuracy of EIS in the detection of thyroid malignancies.

Methods: Patients with thyroid nodules scheduled for thyroid surgery were eligible for the study. Enrolled patients underwent EIS with a T-Scan 2000ED. Nodule location, size, and type (cystic vs. solid) measured by ultrasound, cytology results, thyroid conductivity, and capacitance calculated by EIS were recorded. EIS results were interpreted as positive or negative for malignancy and compared with final histopathology results. Study end points included EIS accuracy, sensitivity, specificity, negative and positive predictive values, and false-positive and false-negative rates.

Results: Sixty-four patients were enrolled onto the study, and all underwent either lobectomy-isthmusectomy (20%) or total thyroidectomy (80%). The mean tumor diameter was 2.64 ± 14.8 mm. Thyroid cancers were identified by histology in 30 patients (46.9%). There were 11 false-positive and four false-negative cases. The overall diagnostic accuracy of EIS was 76.6% (49 of 64 correct diagnoses). The sensitivity and specificity of EIS were 86.7% (26 of 30 true positive) and 67.6% (23 of 34 true negative), respectively. The corresponding positive and negative predictive values were 70.3% and 85.2%.

Conclusions: EIS is a potentially useful imaging modality for differentiating thyroid neoplasms. If these results are confirmed in large-scale trials, EIS may be an important part of the evaluation of thyroid nodules.

Key Words: Electrical impedance scanning • Thyroid nodule • Conductivity • Impedance


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Thyroid nodules are common in the adult population, and the incidence increases linearly with age. Clinically apparent nodules are found in 5% to 7% of adult women and .5% to 1.5% of adult men.1 The overwhelming majority of thyroid nodules are benign; only 5% of all solitary nodules in adults prove to be malignant.2 Solid thyroid lesions, however, have a 10% to 20% risk of malignancy.3

The most effective technique for diagnosing thyroid nodules is fine-needle aspiration (FNA). FNA has a consistent diagnostic accuracy that exceeds 90% in institutions with experience in all aspects of aspiration cytology.4 Up to 30% of patients with thyroid nodules undergoing FNA will have indeterminate cytological findings, in part because of the inability of the technique to distinguish follicular or Hürthle cell adenoma from carcinoma and some hypercellular goiters.5

The diagnosis of follicular or Hürthle cell carcinoma depends on the presence of capsular or vascular invasion, and this can be determined only by permanent-section histological evaluation and not FNA. Thus, patients with an FNA diagnosis of "follicular or Hürthle cell neoplasm/lesion," "indeterminate" results, or "nondiagnostic" cytology require thyroid resection for definitive diagnosis. A noninvasive diagnostic imaging technique that could reliably predict malignancy in a given nodule would be helpful in the evaluation of thyroid nodules and might prevent patients from having to undergo unnecessary diagnostic thyroidectomy. Electrical impedance scanning (EIS) shows promise in establishing the likelihood of cancer in human neoplasms.

Frick and Morse’s6 experiments of the 1920s, which identified significant differences in capacitance between healthy and malignant breast tissue, provided the impetus for the development of a new technological field that used electrical impedance for cancer detection. Subsequent studies established that cancer cells exhibit altered dielectric properties; in contrast to healthy tissue, malignant tumors demonstrate significantly higher capacitance and conductivity, with associated decreased electrical impedance.7 An operational EIS system was introduced in 1983 by Chaundhary et al.,8 who studied the dielectric properties of human breast tissue and identified a 20- to 40-fold higher conductivity and capacitance in malignant compared with healthy breast tissue. The differences in conductivity and capacitance between malignant and normal tissue are likely due to alterations in tissue-packing density, cellular orientation, water content, the amount of extracellular fluid, and membrane proteins.9

Several studies using noninvasive, real-time impedance imaging have established the safety and clinical applicability of this technology for breast cancer detection.10–15 However, electrical impedance imaging is not restricted to the diagnosis of breast cancer. A recent study has demonstrated the feasibility of EIS in differentiating between inflammatory and malignant cervical lymph nodes whose evaluation was equivocal by ultrasound.16 In a pilot study of thyroid EIS, we identified six of seven cancers and defined the need for a more flexible probe with a smaller recording surface.17 A new probe was designed for this study, which evaluated the clinical utility of EIS in the detection of thyroid malignancies.


   METHODS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
This is a prospective single-arm study approved by the institutional review boards/human use committees of participating centers. Consenting adult patients who had primary thyroid nodules (≥5 mm in diameter diagnosed clinically or by ultrasound and who were scheduled to undergo thyroid resection were eligible for the trial. Our previous experience has shown that thyroid biopsies performed shortly before EIS contribute to false-positive results; thus, patients who had prior biopsy or needle aspiration of the thyroid were enrolled ≥4 weeks after the diagnostic procedure.

Patients were excluded from this study if they had undergone prior neck or thyroid operation or thyroid biopsy or aspiration within the preceding 4 weeks. Patients were also excluded if they were pregnant, had an electrically powered implanted device (e.g., pacemaker), or had previously diagnosed cancer of the head or neck.

Study subjects underwent standard preoperative evaluation, including history, physical examination, and thyroid function studies. Clinical evaluation included the location, size, consistency, mobility, and extent of the primary thyroid neoplasm. Pre-EIS ultrasound recorded the lesion size, nature, and location. The extent of operation and the operative findings were recorded, along with the details of the histological evaluation.

Because this was a feasibility trial, the EIS findings did not influence clinical decision making. Patients who underwent lobectomy-isthmusectomy for a clinical or sonographic abnormality did not undergo further resection solely on the basis of a positive EIS finding in the contralateral lobe in the absence of an abnormality evident at operation. Thus, further resection was based on the standard of care and the findings at operation and not on EIS results.

FNA was performed with ultrasound guidance, 22-to 25-gauge needles, and 10-mL syringes. The needle was moved back and forth several times in the substance and through various portions of the thyroid nodule to reduce sampling error. The needle was withdrawn, and the contents were placed evenly as thin smears on glass slides, fixed immediately in Papanicolaou’s fixative to avoid specimen drying, and stained rapidly. Other slides were placed promptly in 95% alcohol fixative for improved detection of colloid. Residual aspirated material was submitted for cell- block development. Six or more clusters of thyroid follicular cells of >10 cells each on 2 different slides were required to confirm a benign diagnosis.

The EIS examination was performed before operation by using the T-Scan 2000ED (TransScan Medical, Austin, TX). This device consists of a flat-screen monitor with a computer mounted on the back (Fig. 1Go). A low-level, biocompatible electrical signal (1.0–2.5 V) was applied via a metal cylinder connected to a computer. The patient, seated upright at approximately 45°, held the cylinder while a noninvasive, handheld T-Scan 2000ED probe was applied by the investigator to the skin overlying the thyroid gland. The probe consists of an 8 x 8 matrix of sensors that measure electrical current. An EIS examination requires the placement of a conducting gel on the surface thyroid probe and on the metal cylinder used to transmit electrical voltage.



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  		FIG. 1. The T-Scan 2000ED electrical impedance scanning device consists of a flat-screen monitor with a computer mounted on the back, a handheld probe, and a metal cylinder.

 
Tissue-related conductivity and capacitance with the high-resolution targeted mode were calculated with a computer software program based on the values of electrical current measured on the skin surface overlying the thyroid gland. The recordings of each thyroid lobe were performed in a predetermined sequence in accordance with the real-time image-acquisition technique (frequency range, 50– 20,000 Hz). The display of the impedance data was presented as a real-time gray level impedance map.

Baseline measurements of conductivity and capacitance were obtained from the proximal sternomastoid muscle in all patients. Conductivity and capacitance were recorded over clinically and sonographically apparent nodules, as well as areas of focal bright spots on the thyroid. The change in conductivity was calculated as the difference in conductivity between the proximal sternomastoid muscle and the thyroid nodule. Comprehensive thyroid EIS took 5 to 15 minutes to complete. An EIS finding of a focal bright white spot correlating with increased conductivity (>25%) or both conductivity and capacitance (decreased impedance) above baseline measurements in the proximal sternomastoid muscle was suggestive of malignancy. Focal bright spots associated with decreased impedance over the palpable or an ultrasound-documented thyroid lesion that could not be attributed to a local artifact (artery, bone, or cartilage) or skin lesion was regarded as EIS positive and suggestive of thyroid cancer (Fig. 2Go). The locations of focal bright spots that were not evident clinically or sonographically were correlated with final pathologic findings.



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  		FIG. 2. Focal bright spots associated with increased conductivity and/or capacitance over the thyroid nodule that could not be attributed to local artifacts or skin lesions were regarded as positive electrical impedance scans and as suggestive of thyroid cancer.

 
Study participants underwent thyroid lobectomy-isthmusectomy or total thyroidectomy, as indicated by the primary pathology. The histopathologic diagnosis for all patients was reviewed and confirmed by an attending pathologist. The primary tumor size, location, consistency, mobility, histological subtype and grade, extrathyroidal extension of disease, multifocality, and coexistent benign pathology were recorded. The results of EIS—positive or negative (Fig. 3Go) for malignancy—were compared with the gold standard of permanent-section histopathologic diagnosis to compute the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for EIS.



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  		FIG. 3. True-negative electrical impedance scanning study characterized by a homogeneous gray level impedance map devoid of bright spots or focal areas of increased conductivity or capacitance.

 
The successful identification of thyroid cancer and the accuracy, sensitivity, specificity, and positive and negative predictive values of EIS were determined:


True-positive examinations in all cases were based on pathologically proven malignancy. False-negative findings on EIS were identified by clinical examination, ultrasound, or FNA and confirmed histologically. Board-certified radiologists interpreted the thyroid ultrasound results, and experienced thyroid cytologists reviewed fine-needle aspirates. Summary statistics were obtained by using established methods. All values are expressed as mean ±SD unless indicated otherwise. Comparisons of means of continuous variables were performed with Student’s t-test. In all statistical analyses, a two-tailed P value <.05 was considered statistically significant. Data analyses were performed with SPSS version 10 for Windows (SPSS Inc., Chicago, IL).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
There were 64 study subjects (mean age, 47.6 years; SD, 17.2 years). Most patients were female and clinically and chemically euthyroid (Table 1Go). FNA was indeterminate (n = 24) or suspicious (n = 7) in 31 (48.4%) patients. The final histopathologic diagnosis of the 24 indeterminate lesions included hyperplastic/adenomatous nodule (n = 7), multinodular goiter (MNG; n = 5), papillary thyroid carcinoma (PTC; n = 5), follicular adenoma (n = 4), follicular carcinoma (n = 2), and Graves’ disease (n = 1). Among the cytologically suspicious cases, there were two PTCs and Hürthle cell adenomas each and one MNG, medullary thyroid carcinoma, and follicular adenoma each. Thus, 70.8% (17 of 24) of indeterminate and 57.1% (4 of 7) of suspicious FNAs proved to be benign.


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  		TABLE 1. Patient characteristics (n = 64)
 
All 31 of the cytologically equivocal lesions were excised, and EIS results indicated 9 true-positive (PTC, n = 8; follicular cancer, n = 1), 13 true-negative, 7 false-positive (MNG, n = 3; Follicular adenoma, n = 2; Hürthle cell adenoma, n = 2), and 2 false-negative (PTC and medullary thyroid carcinoma) nodules. Seventy-five percent (18 of 24) of cytologically indeterminate (11 true negatives and 7 true positives) and 57.1% (4 of 7) of suspicious (2 true negatives and 2 true positives) lesions were diagnosed correctly by EIS. Eighty percent of patients underwent total thyroidectomy.

EIS results were analyzed on a per patient and per nodule basis. The clinical and sonographic characteristics of 89 palpable nodules are listed in Table 2Go. The mean maximum nodule diameter was 2.6 cm. Most thyroid nodules were firm to palpation (69.7%), solid in consistency (76.4%), and mobile (97.8%).


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  		TABLE 2. Nodule characteristics (n = 89)
 
No adverse events were associated with EIS. Correlations between pathologic diagnosis and EIS findings are listed in Table 3Go. There were 30 patients (46.9%) with differentiated thyroid cancers. EIS was positive in 22 (88%) of 25 patients with papillary cancers and in all patients (4 of 4) with follicular cancers. EIS was negative in 4 of the 30 cancer cases: 2 with indeterminate FNAs, 1 with papillary cancer diagnosed by FNA, and 1 in whom FNA was not performed.


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  		TABLE 3. Pathologic diagnosis and EIS findings by patient
 
The mean tumor size was 2 cm; however, six sub-centimeter papillary cancers ranging in size from .5 to 8 mm in diameter were identified by EIS. Specificity for patients with MNG, hyperplastic/adenomatous nodules, and follicular adenoma was 69% (9 of 13), 73% (8 of 11), and 80% (4 of 5), respectively.

The overall accuracy of EIS was 76.6%. The sensitivity, specificity, positive predictive value, and negative predictive value of thyroid EIS were 86.7%, 67.6%, 70.3%, and 85.2%, respectively (Table 4Go). The EIS algorithm performance for the 31 indeterminate or suspicious lesions was not significantly different, with an accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 71.0% (22 of 31), 81.8% (9 of 11), 65.0% (13 of 20), 56.3% (9 of 16), and 86.7% (13 of 15), respectively.


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  		TABLE 4. Electrical impedance scanning (EIS) results (per patient)
 
There was no significant difference in conductivity or capacitance between benign and malignant thyroid nodules (Table 5Go). Among nodules correctly diagnosed by EIS, there was a significant difference in conductivity, capacitance, and change in conductivity and capacitance between true-negative and true-positive EIS cases (Table 6Go). The mean conductivity was increased 45% for true-positive relative to true-negative thyroid EIS; mean capacitance was increased 22%. The change in conductivity was increased 815%, and the change in capacitance was increased 275%.


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  		TABLE 5. Comparison between benign and malignant nodules
 

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  		TABLE 6. Comparison between EIS true-negative and true-positive nodules
 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Thyroid nodules are a common clinical problem. However, a small (approximately 5%–10%) proportion of all nodules actually harbor malignancy.18 Although various clinical factors, such as patient age, family history, radiation exposure, symptoms, nodule size, and regional lymph node enlargement, predict an increased risk of malignancy, the lack of these factors does not reliably exclude thyroid cancer.5 FNA and ultrasound are the two most commonly used methods to evaluate solitary or dominant thyroid nodules. Ultrasound can determine and monitor the size, location, and consistency of the abnormality and guide FNA, but it cannot alone differentiate benign from malignant nodules. With an established diagnostic accuracy of 90% to 95% in the best of hands, FNA is the most reliable and cost-effective initial test for evaluating patients with thyroid nodules.2

However, 10% to 30% of dominant nonfunctioning thyroid nodules evaluated by FNA are cytologically indeterminate or nondiagnostic, and studies of patients undergoing repeat needle aspiration demonstrate a high rate of underlying malignancy.5,19 Consequently, a vexing problem is the group of patients with solid dominant thyroid nodules subjected to diagnostic thyroidectomy on the basis of a cytological diagnosis of follicular or Hürthle cell neoplasm or inconclusive FNA. Adenomas and carcinomas in this diagnostic category are indistinguishable on the basis of cytological features. Identification of differential human telomerase reverse transcriptase gene and galectin 3 protein expression in FNA samples from benign and malignant thyroid neoplasms suggests that these markers may be clinically useful adjuncts for the selection of the subset of malignant solid thyroid nodules.20,21 However, presently no biochemical or genetic test is applied routinely to discriminate benign from malignant follicular neoplasms.

Definitive diagnosis of follicular or Hürthle cell carcinoma requires histological evidence of capsular or vascular invasion by the tumor. As such, these thyroid neoplasms are virtually always treated with resection, and frozen-section analysis for follicular neoplasms seldom alters intraoperative decision making in selecting patients with malignancy for total thyroidectomy.22 Nondiagnostic FNA should not be regarded as benign, because the rate of malignancy in these cytologically indeterminate or nondiagnostic follicular lesions is 20% to 30% and is as high as 44% in the presence of cytologic atypia.23 Thus, although FNA is useful for precluding operation for cytologically benign thyroid abnormalities, it cannot eliminate diagnostic lobectomy-isthmusectomy in such nondiagnostic or indeterminate nodules.24

Adjunctive imaging modalities such as thyroid scintigraphy and ultrasound have been used to determine the risk of malignancy in cytologically indeterminate dominant thyroid nodules. Although these imaging studies may be helpful in individual cases, they have not proven useful in affecting overall surgical decision making. The negative predictive value of these adjunctive tests is insufficient to avoid diagnostic operation in patients with a negative result.25 However, new sonographical criteria have been developed to aid clinical decision making, and high-resolution ultrasound with color Doppler flow mapping shows promise in the differential diagnosis of follicular lesions.26,27

In patients with thyroid nodules and oncocytic cytology, novel diagnostic imaging modalities such as the 99mTc-sestamibi scan lack sufficient specificity to meaningfully guide management decisions.28 The dual-phase thallium-201 thyroid scan has shown promising results in preliminary studies. Initial data show the thallium-201 thyroid scan to be an accurate and cost-effective diagnostic test for equivocal FNA cytological diagnoses in nonfunctioning thyroid nodules.29–31 Further large-scale studies are warranted before thallium-201 thyroid scanning can be incorporated into the diagnostic evaluation of solid thyroid nodules.

The selection of the relatively few malignant lesions out of the multitude of benign thyroid neoplasms remains challenging. Emerging technologies are being evaluated systematically in an effort to refine clinical decision making aimed at reducing the need for diagnostic thyroidectomy for cytologically indeterminate solid thyroid nodules. A rapid, safe, noninvasive, and cost-effective imaging technique that could reliably distinguish benign from invasive follicular and Hürthle cell neoplasms would be a significant contribution to achieving that aim.

The principle that electrical impedance is significantly reduced in malignant tissues was the basis for the development of EIS. Studies of the electrical properties of breast carcinoma enabled the application of this technology to the detection of breast cancer.8,10–12 Recent data suggest that EIS has sufficient negative predictive value (95%) to permit patients with probably malignant (Breast Imaging and Reporting Data System IV) mammographic lesions to avoid unnecessary diagnostic intervention, and software improvements have improved EIS sensitivity (92%), particularly with small (<1-cm) cancers. 13,14,32,33 In a prospective single-institution study of 141 women, EIS was shown to improve the sensitivity of breast mammography from 90% to 98%.34

In an EIS examination, a low level electrical signal is conveyed to the patient through a handheld cylindrical electrode. A multisensor element probe placed on top of the target tissue records the current at each of its sensor elements. This device transmits noninvasive diagnostic information in the form of a two-dimensional real-time impedance map representing the electrical conductivity and the capacitance of the examined organ. Healthy tissue appears as a uniform gray background, whereas an area of higher conductivity or capacitance (lower impedance, such as malignant tumors) is identified as bright white spots on the display screen.

EIS has been shown to be a rapid and safe realtime noninvasive imaging technique that is applicable not only to the breast, but also to other clinically relevant and accessible areas of the body.16,35 Malich et al.16 addressed a pertinent and challenging clinical problem: the differentiation of inflammatory and malignant lymphadenopathy by using EIS. With an EIS sensitivity and specificity of 88% and 82%, respectively, for sonographically suspicious lymph nodes, their preliminary data provide a basis for further study of the clinical utility of EIS in this setting.

Given the potential utility of EIS for the differential diagnosis of suspicious cervical lymph nodes in the latter report, we conducted a pilot study of EIS for thyroid nodules. Six of 7 histologically confirmed cancers among 37 thyroid nodules were identified by EIS.17 However, the larger breast probe used in that study was found cumbersome and unsuitable for neck scanning. A more flexible probe with a smaller recording surface designed specifically for EIS of the neck (T-Scan 2000ED) was developed for this study.

This is the first study to evaluate the clinical performance of thyroid EIS for patients with dominant thyroid nodules requiring diagnostic or therapeutic thyroid resection. The preliminary results reported here demonstrate that thyroid EIS is a safe, rapid, noninvasive, and sensitive imaging modality. The accuracy, sensitivity, and specificity of thyroid EIS were 76.6%, 86.7%, and 66.7%, respectively. EIS algorithm performance was similar for cytologically indeterminate and suspicious thyroid nodules. Increased sensitivity provides a basis for heightened clinical suspicion for malignancy with a positive EIS result. The increased negative predictive value (85.2%) associated with EIS has important clinical implications if EIS is to be used as a screening test. A high negative predictive value is valuable to surgeons because it provides increased certainty with patient treatment decisions. As such, a negative thyroid EIS may be helpful in the clinical setting of an indeterminate FNA by providing increased confidence to avoid diagnostic thyroidectomy and by directing close follow-up for selected patients without significant risk factors for thyroid cancer. Although the sensitivity and specificity of EIS are promising, they are lower than those reported for FNA. It is best to consider EIS a potential adjunct to FNA rather than a replacement for this useful diagnostic technique.

For this study, we selected a highly conservative 4 weeks as the waiting period from the time of FNA to EIS examination. From a practical standpoint, this delay between examinations may contribute to patient anxiety. EIS study before FNA would have many patients undergo an additional study that may not be helpful. Our clinical experience with EIS for lymphadenopathy, thyroid nodules, and breast cancer screening suggests that 2 weeks is an adequate waiting period after FNA to avoid errors in EIS results and is a reasonable waiting period for patients with indeterminate cytology.

The value of this study is that it will permit further EIS algorithm performance modification based on the cancers identified in this patient cohort. The important information derived from the change in conductivity from baseline measurements points to an objective criterion that may be used in addition to the spot-based (focal brightness) standard used in this study. The performance and interpretation of thyroid EIS requires knowledge of cervical anatomy and experience with the device. The potential pitfalls that may contribute to false-positive bright spots include superficial skin lesions, tracheal and thyroid cartilage, the carotid artery, the clavicular head, and air bubbles. Use of objective criteria such as an increment above baseline in conductivity (45%), if supported by further data accumulated in this trial, will likely improve the clinical performance of thyroid EIS.

Poor contact of the probe with the skin overlying the thyroid, as well as superficially located nodules, can create false-positive EIS findings.16 Improvements in the present thyroid EIS probe flexibility, as well as probe size reduction, will limit erroneous results, particularly with large glands and lesions approximating the skin surface. Malignant nodules in the substernal portion of substantial thyroid glands will remain inaccessible to noninvasive EIS given the overlying bony anatomy.

The principal limitation of this study is the small sample size; however, the preliminary data support continued efforts to optimize EIS algorithm performance and to further study the clinical utility of EIS for differentiating benign from malignant thyroid nodules—particularly those with indeterminate FNA results. The advantages of safety, convenience, and patient acceptance characteristic of the real-time, noninvasive T-Scan 2000ED suggest that widespread clinical use is feasible.

Indeterminate needle aspirates of dominant thyroid nodules may be associated with a significant risk of malignancy. Therefore, before physicians can select with certainty those patients with solid thyroid neoplasms and equivocal cytology for nonsurgical management on the basis of negative EIS, further large-scale trials are warranted. The data obtained in this study will be analyzed to better characterize malignant and benign lesions by improvement of both the software and hardware components of the TransScan ED. Larger trials with an improved device will determine the role of EIS in the management of thyroid nodules.

Received for publication March 19, 2004. Accepted for publication October 8, 2004.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

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