The role of technetium-99m methoxyisobutylisonitrile scintigraphy in the differential diagnosis of cold thyroid nodules

Efficacy of dual use of Tc-99m-pertechnetate and Tc-99m-tetrofosmin scintigraphy for the assessment of thyroid nodules

INTRODUCTION

Radioisotope methods have shown to be useful in the non-invasive diagnosis of thyroid nodules over the past years. The present prospective study aims to evaluate the efficacy of gamma imaging using single and dual tracer using Tc-99m pertechnetate and Tc-99m tetrofosmin for evaluation and management of thyroid nodules.

METHODS

Dynamic (perfusion) imaging was performed after injecting 148-185 MBq (4-5 mCi) of Tc-99m pertechnetate followed by static imaging. A second, dynamic (perfusion) imaging study within same week was performed with 296-370MBq (8-10mCi) of Tc-99m tetrofosmin on same group of patients followed by early and delayed images. Results of radionuclide perfusion scan from both studies were compared qualitatively with postsurgical histopathology or fine needle aspiration cytology (FNAC).

RESULTS

Total 65 nodules in 50 patients were included in the study. With single tracer, the specificity and accuracy of Tc-99m pertechnetate was 23% and 45% and for Tc-99m tetrofosmin scan was 40% and 49%. When dual tracers were evaluated for the same group of patients, the specificity was 56% and accuracy was 55%.

CONCLUSION

Dual Tracer technique with Tc-99m pertechnetate and Tc-99m tetrofosmin could be helpful in selecting nodules need surgical intervention. This technique can be used for convenient and rapid diagnostic evaluation of thyroid nodules non-invasively. We suggest a combination of fine needle aspiration biopsy and dual use of Tc-99m-pertechnetate and Tc-99m-tetrofosmin as a routine diagnostic approach to thyroid nodules.

Diagnostic Performance of Technetium-99m Methoxy-Isobutyl-Isonitrile for Differentiation of Malignant Thyroid Nodules: A Systematic Review and Meta-Analysis

BACKGROUND

The purpose of the current study was to investigate the diagnostic performance of technetium-99m (Tc-99m) methoxy-isobutyl-isonitrile (MIBI) for differentiation of malignant thyroid nodules (TN) through a systematic review and meta-analysis.

METHODS

The MEDLINE/PubMed and EMBASE database, from the earliest available date of indexing through January 31, 2018, were searched for studies evaluating the diagnostic performance of Tc-99m MIBI for TN. The sensitivities and specificities were determined across studies, positive and negative likelihood ratios (LR+ and LR-) were calculated, and summary receiver operating characteristic curves were constructed.

RESULTS

Across 22 studies (2421 patients), the pooled sensitivity for Tc-99m MIBI thyroid scan was 0.87 [confidence interval (CI) 0.76-0.93] with heterogeneity (I² = 92.3) and a pooled specificity of 0.78 [CI 0.67-0.86] with heterogeneity (I² = 96.4). LR syntheses gave an overall LR+ of 4.0 [CI 2.5-6.3] and LR- of 0.17 [CI 0.09-0.32]. The pooled diagnostic odds ratio was 24 [CI 63-176]. The hierarchical summary receiver operating characteristic curve indicates that the area under the curve was 0.90 [CI 0.87-0.92]. In meta-regression analysis, no definite variable was the source of the study heterogeneity.

CONCLUSION

The current meta-analysis shows a moderate sensitivity and specificity of Tc-99m MIBI thyroid scan for differentiation of malignant TN. However, the diagnostic odds ratio was relatively low and the LR scattergram indicated that Tc-99m MIBI thyroid scan is not useful for confirming the presence of malignant TN or for its exclusion. Therefore, Tc-99m MIBI thyroid scans should be used restrictively and interpreted cautiously when assessing TN for malignancy.

[Evaluation of intra- and interobserver agreement of Technetium-99m-sestamibi imaging in cold thyroid nodules]

AIM

A supplementary diagnostic tool in the assessment of cold thyroid nodules is scintigraphic imaging with^99mTc-MIBI. Aim of this study was to investigate the validity of this tool by determining the intra- and interobserver agreement in the assessment of cold thyroid nodules in Tc-MIBI scintigrams.

METHODS

A retrospective study with 284 patients (16-85 years of age, 194 women, 90 men) was performed. They had at least one cold nodule and from each of whom were available at least one^99mTc-MIBI and the Tc- pertechnetate image. Eight physicians, active in nuclear medicine, reviewed the sctinti- grams twice in a random order. They were asked if they considered the combination a match, a mismatch, or inconclusive, and if the early or delayed image was more significant or if there was no difference.

RESULTS

Intraobserver agreement ranged from κ = 0.56 (moderate) to κ = 0.78 (substantial). Interobserver agreement ranged from κ = 0.44 to κ = 0.53 (moderate). Interobserver agreement for observers with more than 5 years of work experience in nuclear medicine ranged from κ=0.61 to κ = 0.70 (substantial), for observers with 2-5 years from κ = 0.53 (moderate) to κ = 0.61 (substantial) and for observers with < 2 years from κ = 0.47 to κ = 0.61. "No difference" was chosen in 70 resp. 77 % of all cases in session 1 resp. 2. The early image was preferred in 26 resp. 20 %, and the delayed one in 3 resp. 4 % of all cases.

CONCLUSION

The values of interobserver agreement of all eight observers show that the assessment of Tc-MIBI scintigrams is subject to a certain variance. Hence, they ought to be finally assessed by observers with at least 5 years of work experience.

Diagnostic accuracy of [99mTc]Tc-Sestamibi in the assessment of thyroid nodules

[^99mTc]Tc-Sestamibi (MIBI) is an increasingly used tool for evaluation of thyroid nodules. However, there is a lack of evidence about the accuracy of this method in the European population. The aim of this study was to assess the utility of MIBI for the differentiation of thyroid nodules in a large cohort. 161 patients underwent MIBI, followed by a thyroidectomy. We used a dual phase MIBI protocol. Interpretation of the images included a scoring system from 0 (absent) to 3 (increased); this was to provide a scale for the uptake of the thyroid nodule in comparison to the paranodular tissue. Additionally, we evaluated the tracer uptake trend in late images compared to early images. We used the final histopathology as the reference standard. Scores 0-1 in early images, scores 0-2 in late images, and an absence of increasing uptake in the thyroid nodule in late images, showed the best predictive values to exclude malignancy, respectively (negative predictive value (NPV) 89%). Highest sensitivity (91%) for malignant nodules was evident in early images with a score 1-3. Highest specificity (91%) was obtained when the negative was defined as an absence of uptake-increase, in the late images. This study confirms that the most valuable feature of MIBI is the high NPV. Thus, with the appropriate interpretation method, high sensitivity and specificity, and moderate PPV can be obtained.

Evaluation of hypofunctioning thyroid nodules with technetium-99m MIBI and ultrasonography

Background: Fine needle aspiration cytology (FNAC) cannot reliably differentiate follicular adenoma from follicular carcinoma (FC), which requires histological evidence of capsular or vascular invasion. FC is the most predominant thyroid cancer in our loco-regional environment, indicating the need for improvement in preoperative diagnostic accuracy of thyroid nodules to ensure appropriate and timely interventions.Objective: The purpose of this study was to assess the role of technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) scintigraphy and ultrasonography (USG) in the differential diagnosis of thyroid nodules.Methods: Forty-two patients with hypofunctioning thyroid nodules were prospectively studied with 99mTc-MIBI scintigraphy and USG to differentiate benign from malignant nodules. An injection of 740 MBq of 99mTc-MIBI was intravenously administered, followed by semiquantitative analysis of dual-phase scans using a 4-point (0 to 3) scoring system. USG was subsequently performed and interpretation was based on some sonographic criteria for malignancy. In the following days and weeks, patients underwent FNAC followed by surgery and histopathologic examination.Results: All malignant nodules were positive on 99mTc-MIBI and all but two malignant nodules were positive on USG. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy are, respectively, 100%, 70%, 65%, 100%, and 81% for 99mTc-MIBI scintigraphy; 87%, 78%, 68%, 91% and 81% for USG; and 83%, 100%, 100%, 96% and 64% for FNAC. There was no statistically significant difference between 99mTc-MIBI scintigraphy and USG performance for both benign (p = 0.317) and malignant (p = 0.573) nodules.Conclusion: 99mTc-MIBI scintigraphy and USG are important imaging modalities in the evaluation of thyroid nodules, particularly follicular neoplasms which are frequently associated with non-diagnostic cytology.

A gamma-distribution convolution model of 99mTc-MIBI thyroid time-activity curves

Background

The convolution approach to thyroid time-activity curve (TAC) data fitting with a gamma distribution convolution (GDC) TAC model following bolus intravenous injection is presented and applied to ^99mTc-MIBI data. The GDC model is a convolution of two gamma distribution functions that simultaneously models the distribution and washout kinetics of the radiotracer.

The GDC model was fitted to thyroid region of interest (ROI) TAC data from 1 min per frame ^99mTc-MIBI image series for 90 min; GDC models were generated for three patients having left and right thyroid lobe and total thyroid ROIs, and were contrasted with washout-only models, i.e., less complete models. GDC model accuracy was tested using 10 Monte Carlo simulations for each clinical ROI.

Results

The nine clinical GDC models, obtained from least counting error of counting, exhibited corrected (for 6 parameters) fit errors ranging from 0.998% to 1.82%. The range of all thyroid mean residence times (MRTs) was 212 to 699 min, which from noise injected simulations of each case had an average coefficient of variation of 0.7% and a not statistically significant accuracy error of 0.5% (p = 0.5, 2-sample paired t test). The slowest MRT value (699 min) was from a single thyroid lobe with a tissue diagnosed parathyroid adenoma also seen on scanning as retained marker. The two total thyroid ROIs without substantial pathology had MRT values of 278 and 350 min overlapping a published ^99mTc-MIBI thyroid MRT value. One combined value and four unrelated washout-only models were tested and exhibited R-squared values for MRT with the GDC, i.e., a more complete concentration model, ranging from 0.0183 to 0.9395.

Conclusions

The GDC models had a small enough TAC noise-image misregistration (0.8%) that they have a plausible use as simulations of thyroid activity for querying performance of other models such as washout models, for altered ROI size, noise, administered dose, and image framing rates. Indeed, of the four washout-only models tested, no single model approached the apparent accuracy of the GDC model using only 90 min of data. Ninety minutes is a long gamma-camera acquisition time for a patient, but a short a time for most kinetic models. Consequently, the results should be regarded as preliminary.

[99mTc-MIBI scintigraphy of hypofunctional thyroid nodules. Comparison of planar and SPECT imaging]

99mTc-MIBI-scintigraphy allows to assess the dignity of hypofunctional thyroid nodules. A concordant pattern in MIBI- and pertechnetate-scintigraphy excludes malignancy with high accuracy. For increased MIBI-uptake histological evaluation is advised. The assessment of MIBI-isointense nodules is discussed controversially. Objective of our study was to analyse the prevalence of malignancy for isointense nodules and the diagnostic accuracy of image acquisition in SPECT-technique.

PATIENTS, METHODS

MIBI-scintigraphies were analysed retrospectively. Imaging was performed 60 min after intravenous injection of 510 MBq 99mTc-MIBI. Thyroid nodules were assessed as hypo-, iso- or hyperintense compared to the paranodular tissue.

RESULTS

83 of 225 patients underwent thyroid surgery (age 48.6 ± 12.6 years, 72% women). In 12 (14.5%) cases a papillary carcinoma was diagnosed. In planar imaging 12, 34 and 37, in tomographical imaging 16, 21 and 46 nodules, respectively, were classified as hypo-, iso- oder hyperintense. Among hypo-, iso- and hyperintense nodules in planar imaging 1, 5 and 6 carcinomas were found, resp. In tomographical imaging no, 4 and 8 carcinomas were found, respectively. Classification of iso- and hyperintense nodules as "suspicious for malignancy" showed for planar imaging a sensitivity, specificity, NPV and PPV of 91.7, 15.5, 91.7 and 15.6%, for tomographical imaging of 100, 22.5, 100 and 17.9%, respectively.

CONCLUSION

Hypofunctional thyroid nodules with iso- and hyperintense MIBI-Uptake have a comparable prevalence of malignancy. Image acquisition in SPECT-technique results in improved diagnostic sensitivity and negative predictive value.

Diagnostic performance of (99m)Tc-MIBI scan in predicting the malignancy of thyroid nodules: a meta-analysis

Several studies have investigated the diagnostic performance of (99m)Tc-MIBI scan in the evaluation of thyroid nodules suspicious for malignancy with conflicting results. The aim of our study is to meta-analyze published data on this topic. A comprehensive literature search of studies published through December 2012 regarding the diagnostic performance of (99m)Tc-MIBI scan in the evaluation of thyroid nodules suspicious for malignancy was carried out. Pooled sensitivity and specificity of (99m)Tc-MIBI scan on a per lesion-based analysis and the area under the ROC curve were calculated. Pathological reports of thyroid nodules were considered as reference standard. Twenty-one studies were included in the meta-analysis. Pooled sensitivity and specificity of (99m)Tc-MIBI scan in detecting malignant thyroid nodules were 85.1 % [95 % confidence interval (95 % CI): 81.1-88.5 %] and 45.7 % (95 % CI: 42.7-48.7 %), respectively, on a per lesion-based analysis, irrespective of eventual results of previous technetium pertechnetate ((99m)TcO4) or iodine-123 ((123)I) scan. The area under the ROC curve was 0.78. A sub-analysis restricted to data on hypofunctioning nodules on (99m)TcO4 or (123)I scans was performed: pooled sensitivity and specificity of (99m)Tc-MIBI scan in these nodules were 82.1 % (95 % CI: 77.2-86.3 %) and 62.8 % (95 % CI: 58.9-66.7 %), respectively, on a per lesion-based analysis. The area under the ROC curve was 0.81. (99m)Tc-MIBI scan is a sensitive diagnostic tool in predicting the malignancy of thyroid nodules. Therefore, this imaging method could be helpful in patients with thyroid nodules in which malignancy is suspected on the basis of conventional diagnostic techniques. Higher specificity can be reached when hypofunctioning thyroid nodules are considered.

Evaluation of thyroid nodules--combined use of (99m)Tc-methylisobutylnitrile scintigraphy and aspiration cytology to assess risk of malignancy and stratify patients for surgical or nonsurgical therapy--a retrospective cohort study

OBJECTIVE

Thyroid nodules are a common clinical problem, and differentiation between benign and malignant nodules is essential. The aim of this study was to evaluate an approach for cold thyroid nodules including (99m)Tc-methylisobutylnitrile (MIBI) scintigraphy to assess risk of malignancy and stratify patients for therapy.

DESIGN

Retrospective cohort study; 391 patients with at least one cold thyroid nodule were consecutively admitted (between 1 January 2004 and 31 December 2006) and recommended for surgical or nonsurgical therapy.

MEASUREMENTS

Thyroid ultrasonography, (99m)Tc-pertechnetate scintigraphy, laboratory tests, fine needle aspiration cytology (FNAC) and MIBI scintigraphy.

RESULTS

57·3% (224/391) had one cold nodule, 17·9% (70/391) had several cold nodules, and 24·8% (97/391) had both cold and hot nodules. MIBI scintigraphy was classified into 'positive' (16·1%, 63/391), 'weakly positive' (19·2%, 75/391) or 'negative' (64·7%, 253/391). FNAC was classified into benign (87·9%, 247/281), nondiagnostic (6·8%, 19/281) or suspicious/malignant (5·3%, 15/281). 127 patients received surgery, revealing malignancy in 13·3% (17/127), predominantly papillary (64·7%, 11/17) and follicular carcinoma (23·5%, 4/17). MIBI scintigraphy was 'positive' (64·7%, 11/17) or 'weakly positive' (23·5%, 4/17) in most patients with malignant findings. FNAC was unavailable in 23·5% (4/17) with malignancy, positive in 38·5% (5/13) and negative in 61·5% (8/13). Among patients undergoing surgery, sensitivity, specificity, negative and positive predictive values for MIBI scintigraphy were 88·2%, 35·5%, 95·1% and 17·4%, for FNAC 38·5%, 90·6%, 90·6% and 38·5%, respectively, and for the combination (MIBI scan + FNAC) 92·3%, 30·6%, 96·3% and 16·9%. Benign MIBI-positive nodules were predominantly follicular adenomas (68%, 33/48).

CONCLUSION

Evaluation of cold thyroid nodules by MIBI scintigraphy aids therapeutic decisions: MIBI-negative findings support nonsurgical management in about two-thirds of patients, while MIBI-positive findings have an increased risk of malignancy, supporting surgical therapy. However, the positive predictive value was low, which requires further research.

Fine-needle aspiration in the work-up of thyroid nodules

Fine-needle aspiration (FNA) is the crucial diagnostic test used for the evaluation of patients with a thyroid nodule. The result of an FNA determines if a patient can be followed with repeated examinations or referred for surgery. The value of FNA can be enhanced by attention to technical details. Communication between operator and pathologist is essential. A pathologist's interpretation is aided if essential clinical information is provided on a requisition form. Although reporting terminology has been varied and confusing in the past, a proposal for a uniform reporting system provides 6 clearly defined and clinically relevant reporting categories and promises to standardize the reporting of thyroid FNA results.

(99m)Tc-sestamibi scanning in thyroid nodules with nondiagnostic cytology

BACKGROUND

Our aim in this study was to assess the relevance of (99m)Tc-sestaMIBI (MIBI) scan in the diagnostic evaluation of thyroid nodules with nondiagnostic cytology.

METHODS

In all, 74 patients with a single nodule and repeatedly nondiagnostic ultrasound-guided fine-needle aspiration cytology (US-FNAC) were enrolled. In all cases thyroid nodules were cold in (99m)Tc-pertechnetate (Tc) scans. Thyroid scans were also acquired 30 and 120 minutes after intravenous administration of MIBI. Nodules that concentrate MIBI were considered as positive (ie, suspicious for malignancy). Histologic findings were obtained after surgery in all patients.

RESULTS

No differences occurred in early and late MIBI images. None of 63 patients with a negative MIBI scan had a final histologic diagnosis of malignancy (ie, no false-negative results). Two patients with a final histologic diagnosis of papillary thyroid carcinoma (PTC) and 1 with follicular thyroid carcinoma (FTC) had a positive MIBI scan. Eight patients with a final histologic diagnosis of benign lesions (3 with follicular adenomas) also had MIBI-positive scans. The sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were, respectively, 100%, 88%, 89%, 27%, and 100%.

CONCLUSIONS

A negative MIBI scan in a cold nodule accurately excludes malignancy when US-FNAC is reported as nondiagnostic. This avoids the need for more invasive diagnostic procedures (ie, surgery) and positively influences the cost-effectiveness profile. A MIBI scan may be performed by acquiring images 30 minutes after tracer administration alone. Histology is still necessary to distinguish benign from malignant disease in a MIBI-positive nodule but unnecessary surgery could have been reduced from 71 to 8 cases in our series.

99mTc-MIBI Imaging in the presurgical characterization of thyroid follicular neoplasms: relationship to multidrug resistance protein expression

Recently, thyroid (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) scintiscanning has been proposed in an attempt to preoperatively identify thyroid malignancies, but discrepant results have been reported for oncocytic lesions. The aim of this study was to investigate the usefulness of visual and semiquantitative analyses of (99m)Tc-MIBI scintigraphy for preoperatively characterizing thyroid nodules with indeterminate cytologic diagnoses, segregating in advance nononcocytic variants from those that are oncocytic. This study also aimed to analyze the relationship between (99m)Tc-MIBI images and P-glycoprotein (P-gp)/multidrug resistance-associated protein-1 (MRP1) immunohistochemical expression.

METHODS

Fifty-one consecutive patients with cold thyroid nodules cytologically diagnosed as nononcocytic or oncocytic follicular neoplasm were prospectively studied. Visual and semiquantitative (99m)Tc-MIBI scanning was performed and the diagnoses of the lesions were histologically proven by subsequent thyroidectomy. Immunohistochemical evaluation of P-gp and MRP1 was also performed on surgical samples.

RESULTS

Visual and semiquantitative (99m)Tc-MIBI scintiscans showed a low specificity in preoperatively discriminating malignant oncocytic lesions. In nononcocytic nodules, the semiquantitative method was more accurate than the visual (94.44% and 77.78%, respectively). P-gp protein expression was negative in all thyroid lesions, whereas apical plasma membrane MRP1 expression was found in 78% of the lesions with a negative (99m)Tc-MIBI retention index, compared with 11% of lesions with a positive retention index, correlating most strongly with a negative (99m)Tc-MIBI RI in those cases with strong MRP1 apical expression.

CONCLUSION

Semiquantitative (99m)Tc-MIBI scintigraphy is an adjunctive method to predict preoperatively the malignant behavior of nononcocytic follicular thyroid nodules indeterminate at fine-needle aspiration biopsy, with a potential impact on the definition of their clinical management. Moreover, the good correlation found between immunohistochemical apical expression of MRP1 and the scintigraphic findings supports the (99m)Tc-MIBI results and provides tissue information on the molecular mechanisms responsible for (99m)Tc-MIBI images in thyroid lesions.

Current role of radionuclide imaging in differentiated thyroid cancer

Nuclear medicine plays an integral role in the management of differentiated thyroid cancer. This editorial aims to provide a summary of the current role of radionuclide imaging, including whole body iodine scan and fluorodeoxyglucose (FDG)-positron emission tomography (PET), in the diagnostic work-up and follow-up of patients with thyroid cancer.

Prospective trial evaluating electrical impedance scanning of thyroid nodules before thyroidectomy: final results

BACKGROUND

Electrical impedance scanning (EIS) identifies tissue impedance changes associated with malignancy. Methods to distinguish benign from malignant thyroid nodules, particularly in patients with indeterminate cytology are lacking.

PURPOSE

To determine the diagnostic accuracy of EIS in the preoperative evaluation of thyroid nodules.

PATIENTS AND METHODS

From September 2002 to December 2006, 216 patients underwent thyroid fine needle aspiration (FNA) and EIS prethyroidectomy in this prospective cohort study. EIS, either positive or negative for malignancy, was correlated with final histopathology. A focal bright spot over a thyroid nodule correlating with increased conductivity and/or capacitance >25% baseline sternocleidomastoid muscle impedance defined positive EIS. Study endpoints were EIS accuracy, sensitivity (Sn), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV). This study has been registered in the National Institutes of Health's public trials registry at ClinicalTrials.gov. The registration number is NCT00571077.

RESULTS

EIS correctly diagnosed 96 of 110 patients with malignant and 75 of 106 patients with benign dominant thyroid nodules: Sn = 87%, Sp = 71%, PPV = 76%, NPV = 84%: overall EIS accuracy = 79%. Pretest cancer probability of 51% (110 of 216) increased to 76% (96 of 127) post-EIS, and preoperative use of EIS would result in a significant reduction (71%, 75 of 106) in number of operations performed for benign nodules. EIS performance was similar for 109 patients with indeterminate FNA: Sn = 83%, Sp = 67%, PPV = 61%, NPV = 87%, accuracy = 73%. Pretest probability of cancer increased from 39% (42 of 109) to 61% (35 of 57) post-EIS. The use of EIS would result in a significant reduction (67%, 45 of 67) in the number of purely diagnostic thyroidectomy for indeterminate FNA.

CONCLUSION

EIS shows promise in differentiating thyroid nodules. Further EIS hardware and software optimization is warranted to improve upon the already favorable negative predictive value in indeterminate thyroid nodules.

Evaluation and imaging of a thyroid nodule

The approach to the thyroid nodule has been incrementally modified over the past decade. The widespread adoption of fine needle aspiration in the 1980s, coupled with increased use of serial ultrasound monitoring, arguably led to the biggest changes in recommendations for surgical intervention during the past 50 years. For the office-based practitioner, thyroid nodule presentation patterns are changing with discoveries of more thyroid "incidentalomas" and with new risk assessment challenges associated with small (<1 cm) nodules. At the same time, improved primary evaluation techniques, most notably the increasing use of small, portable ultrasound imaging units, are making many clinicians more comfortable in recommending less invasive follow-up.

Characterization of follicular thyroid nodules at fine needle aspiration biopsy using double phase thallium-201 imaging: comparison of visual and semiquantitative analyses

OBJECTIVE

To compare visual and semiquantitative indices of double phase thallium-201 thyroid scintigraphy (DTS) for differentiation of malignant nodules by indeterminate fine needle aspiration biopsy (FNAB) results.

DESIGN

DTS (early; 15 minutes; delayed, 2 hour) were performed after injection of 37MBq of thallium-201 in 60 patients with indeterminate FNAB.

MAIN OUTCOME

With grade 4 and 5, sensitivity and specificity were 51.4% and 78.3%, respectively. With early lesion to nonlesion ratio (L/N) 1.49, sensitivity and specificity were 97.3% and 39.1%, respectively. With delayed L/N 1.89, sensitivity and specificity were 70.3% and 78.3%, respectively. With wash-out rate (WR) 18.93%, sensitivity and specificity were 89.2% and 82.6%. Early L/N was superior to delayed L/N and WR for the detection of malignant thyroid nodules.

CONCLUSION

Visual assessment had a limited value for differentiation of follicular nodules. The optimal semiquantitative indices were 1.49 for early L/N and 1.89 for delayed L/N. Also, optimal WR was 18.93%. The early L/N was superior to delayed L/N and WR for the detection of malignant thyroid nodular lesions. However, visual assessment and early L/N of DTS showed similar results. Visual analysis and semiquantitative indices of DTS could not differentiate follicular carcinoma and follicular variant of papillary thyroid cancer.

Respective Roles of Thyroglobulin, Radioiodine Imaging, and Positron Emission Tomography in the Assessment of Thyroid Cancer

Depending on the iodine supply of an area, the incidence of thyroid cancer ranges between 4 and 12/100,000 per year. To detect thyroid cancer in an early stage, the assessment of thyroid nodules includes ultrasonography, ultrasonography-guided fine-needle aspiration biopsy, and conventional scintigraphic methods using (99m)Tc-pertechnetate, (99m)Tc-sestamibi or -tetrofosmin, and (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in selected cases. After treatment of thyroid cancer, a consequent follow-up is necessary over a period of several years. For following up low-risk patients, recombinant thyroid-stimulating hormone-stimulated thyroglobulin and ultrasonography is sufficient in most cases. After total thyroidectomy and radioiodine ablation therapy, thyroid-stimulating hormone-stimulated thyroglobulin should be below the detection limit (eg, <0.5 ng/mL, R: 70-130). An increase of thyroglobulin over time is suspicious for recurrent or metastatic disease. Especially in high-risk patients, aside from the use of ultrasonography for the detection of local recurrence and cervial lymph node metastases, nuclear medicine methods such as radioiodine imaging and FDG-PET are the methods of choice for localizing metastatic disease. Radioiodine imaging detects well-differentiated recurrences and metastases with a high specificity but only moderate sensitivity. The sensitivity of radioiodine imaging depends on the activity administered. Therefore a low activity diagnostic (131)I whole-body scan (74-185 MBq) has a lower detection rate than a high activity post-therapy scan (3700-7400 MBq). In patients with low or dedifferentiated thyroid cancer and after several courses of radioiodine therapy caused by metastatic disease, iodine negative metastases may develop. In these cases, despite clearly elevated levels of thyroglobulin, radioiodine imaging is negative or demonstrates only faint iodine uptake. The method of choice to image these iodine negative metastases is FDG-PET. In recent years the combination of PET and computed tomography has been introduced. The fusion of the metabolic and morphologic information was able to increase the diagnostic accuracy, reduces pitfalls and changes therapeutic strategies in a reasonable number of patients.

Concurrent nonfunctioning parathyroid carcinoma and parathyroid adenoma

Parathyroid carcinoma is a rare etiology of primary hyperparathyroidism characterized by severe clinical symptoms of hypercalcemia and markedly elevated serum parathormone levels. Nonfunctioning parathyroid carcinoma is an inactive form of the disease. There are less than 30 reports of nonfunctioning parathyroid carcinoma in the English literature and the association with parathyroid adenoma has not been described. This report describes a patient with concurrent nonfunctioning parathyroid carcinoma and a functioning parathyroid adenoma.

[Diagnosis of thyroid nodule. Application of evidence-based medicine]

OBJECTIVE

The frequency of thyroid nodules requires an appropriate and consistent undertaking of such pathology by the entire medical profession. Over the past few years, the ANAES (National Agency of Health Accreditation and Evaluation - 1995 - 1997) had formulated medical recommendations. Our work aimed at updating such recommendations considering recent literature developments and their level of evidence.

MATERIAL AND METHODS

We have selected high-level of evidence's articles published since 1997 dealing with the diagnostic undertaking of thyroid nodule. Such analysis was conducted using the search engine "Medline" and the level of evidence of the selected articles was evaluated by taking into account the professional recommendations of the "literature analysis and gradation of recommendations' guide" of ANAES.

RESULT

At present, two diagnostic tests are necessary in the diagnostic evaluation of a thyroid nodule (ultrasonography and fine-needle aspiration).

CONCLUSION

The medical recommendation will hence result in the synthesis of these two different diagnostic tests, nevertheless fine-needle aspiration being essential and having priority in evaluating the risk of cancer.

Differentiation of Malignant and Benign Solitary Thyroid Nodules Using 30- and 120-Minute Tc-99m MIBI Scans

Technetium-99m methoxy isobutylisonitrate (MIBI) has been found to be taken up by various tumors, including thyroid cancer. We prospectively evaluated 77 patients with cold thyroid solitary nodules on Tc-99m pertechnetate scintigraphy to evaluate the diagnostic value of Tc-99m MIBI scintigraphy. The aim of this study was to find out if thyroid nodules can be characterized on the basis of retention of MIBI and whether preoperative evaluation of malignancy is possible using this method. Single injection, dual-phase (30 and 120 minutes) thyroid scintigraphy using Tc-99m MIBI was performed in all these patients. In the following days and weeks, all patients underwent surgery. Using the 120/30-minute thyroid lesion to background radiouptake ratio (RUR), malignant and benign thyroid nodules could be separated with a sensitivity, specificity, and positive predictive value of 84.4%, 95.45%, and 93.33%, respectively. The mean RUR for malignant thyroid lesions was found to be 1.57+/-0.32, whereas for benign lesions, the ratio was significantly lower, 0.32+/-0.19. In conclusion, fine needle aspiration cytology along with the 120/30 minutes Tc-99m MIBI scintigraphy ratio appears to be useful in the preoperative assessment of solitary thyroid nodules.

Differentiated thyroid cancer and outcome in iodine deficiency

AIMS

Factors influencing prognosis and long-term outcome of thyroid cancer have been described by several groups. We wished to asses the previously described prognostic factors in a moderately iodine deficient region in Hungary.

METHODS

Four hundred and fifty-four out of 492 patients who had surgery for papillary thyroid cancer (PTC, 386 cases) and follicular thyroid cancer (FTC, 106 cases) between 1971 and 1998 were analyzed. Survival curves were compared using the Kaplan-Meier method and Cox regression analysis.

RESULTS

The 10 and 20-year survival rates were 87.9 and 84% for PTC, and 78.2 and 78.2% for FTC. In PTC, extrathyroidal invasion (p<0.0001), lymph node metastasis (p<0.0001), distant metastasis (p<0.0001), and age over 40 years (p=0.002) were significant adverse predictors. In FTC, extrathyroidal invasion (p=0.003) distant metastases (p<0.0001), and age over 40 years (p=0.011) were significant adverse predictors.

CONCLUSION

Iodine intake did not appear to influence survival. The incidence of follicular cancer, which has less favourable prognosis, was higher in iodine deficient regions. This supports the importance of iodine supplementation in these areas.

Cancer imaging - making the most of your gamma camera

As MRI threatens the use of bone scintigraphy for skeletal metastases and 18F-fluorodeoxyglucose positron emission tomography (18FDG-PET) emerges as the main focus in nuclear oncology, the future role of the gamma camera in cancer imaging appears unclear. However, there is a range of pre-existing conventional gamma camera techniques that have incremental benefit over CT and other structural imaging techniques, but are yet to be fully exploited in the care of cancer patients. This article reviews some of the more advanced conventional nuclear medicine techniques for cancer imaging. Often gamma camera techniques perform close to 18FDG - PET or provide complementary information.Where 18FDG - PET is diagnostically superior, the incremental cost-effectiveness gain of 18FDG - PET over conventional gamma camera techniques has not always been fully evaluated.

A comparison of radionuclide thyroid angiography, (99m)Tc-MIBI scintigraphy and power Doppler ultrasonography in the differential diagnosis of solitary cold thyroid nodules

We prospectively studied 43 patients with solitary cold thyroid nodules greater than 1.5 cm in diameter to determine the comparative diagnostic value of radionuclide thyroid angiography (RTA), technetium-99m methoxyisobutylisonitrile ((99m)Tc-MIBI) scintigraphy and power Doppler ultrasonography (PDUS) in the differentiation of benign and malignant thyroid nodules. Perfusion of the nodules in RTA was compared with the perfusion in the surrounding normal thyroid tissue and classified as follows: 0, avascular; 1, hypovascular; 2, isovascular; 3, hypervascular. (99m)Tc-MIBI uptake in the nodules compared with that in surrounding thyroid tissue was scored for both early and delayed images as follows: 0, cold; 1, decreased; 2, equal; 3, increased. PDUS patterns were classified as nodule vascularisation patterns. The malignancy criteria were set as follows: hypervascular nodule with rapid washout in RTA; complex ring sign with anarchic structure or delta sign in PDUS, and positive retention and increased uptake in the nodule in the early and delayed (99m)Tc-MIBI images. These data were compared with the histopathological results. Histology revealed thyroid carcinoma in nine patients (five cases of papillary carcinoma, three of follicular carcinoma and one of medullary carcinoma) and benign conditions in 34 patients (30 cases of nodular goitre, three of lymphocytic thyroiditis and one of follicular adenoma). Sensitivity, specificity and accuracy were, respectively, 0.89, 1.00 and 0.97 for RTA, 1.00, 0.76 and 0.81 for PDUS, and 0.67, 0.91 and 0.86 for (99m)Tc-MIBI scintigraphy (when nodules with increased uptake in both the early and the delayed images and a positive retention index were considered as malignant). RTA, (99m)Tc-MIBI scintigraphy and PDUS could be helpful in the preoperative assessment of solitary cold thyroid nodules. In this study, RTA was found to be the most accurate and specific method for differentiation of malignant from benign thyroid nodules.

Evaluation of thyroid nodules with technetium-99m MIBI and technetium-99m pertechnetate

BACKGROUND

Most thyroid centers use fine-needle aspiration (FNA) and technetium-99m pertechnetate for the preoperative assessment of thyroid nodules. This approach is sufficient in most cases other than follicular neoplasm, and follicular carcinoma is more common than papillary carcinoma in developing countries such as in our center. Technetium 99m-methoxyisobutylisonitrile (MIBI) proposed for myocardial perfusion was also found to be taken up by a variety of tumors including thyroid cancer.

METHODS

We evaluated MIBI uptake of nodular thyroid disease and compared it with pertechnetate scan, FNA, and histologic findings for the differentiation of malignant thyroid nodules from benign lesions. Seventy-one patients were included in the study. Three-phase pertechnetate scintigraphy was completed after a single injection of 150 MBq. Perfusion/uptake mismatch (uniform perfusion with cold uptake) was regarded as positive for malignancy, whereas perfusion/uptake match (cold perfusion with cold uptake) was regarded as negative. After 1 week, 400 MBq of MIBI was injected, images were obtained at 20 minutes and 2 hours, and evaluated semiquantitatively by use of a 4-point (0-3) scoring system. MIBI scans were considered positive if there was uptake superior to normal thyroid tissue on early and delayed images (score = 3). In the following days and weeks, all patients underwent FNA followed by surgery.

RESULTS

Histopathologic diagnosis revealed a total of 23 thyroid carcinomas, 21 (91%) and 19 (83%) were positive on MIBI and pertechnetate, respectively. Of the 48 patients with benign nodules, 11 (23%) and 29 (60%) were positive on MIBI and pertechnetate, respectively. The specificity of MIBI, pertechnetate, and FNA is 77%, 40%, and 90%, respectively.

CONCLUSIONS

In combination with FNA and three-phase pertechnetate scan, MIBI could be helpful in preoperative assessment of thyroid nodules. Intense MIBI activity increases the probability of thyroid cancer, whereas reduced activity drastically decreases the probability of malignancy.