Positron emission tomography imaging of musculoskeletal tumors in the shoulder girdle

The shoulder girdle presents unique features for the preoperative planning of musculoskeletal tumors. This is the first trial to evaluate positron emission tomography (PET) analysis for preoperative planning in shoulder girdle tumors. Fifty-two patients were examined with fluorine 18 fluoro-2-deoxy-D-glucose (FDG)-PET and/or alpha-methyltyrosine (FMT)-PET. Imaging findings were visually inspected in conjunction with computed tomography and/or magnetic resonance imaging, and standardized uptake values (SUVs) were generated. FDG-PET may be useful for the detection of malignant tumors and screening for metastatic spread, with the qualitative assessment of heterogeneous biologic activity providing a correct approach for biopsy. The mean SUVs for malignant tumors were significantly higher than those for benign lesions. However, a useful cutoff SUV was not found in either FDG- or FMT-PET for differentiating malignant from benign tumors from receiver operating characteristic curve analysis. SUVs on FDG- and FMT-PET may merely be limited to differentiating malignant from benign tumors in the shoulder girdle.     

Positron emission tomography (PET) in the urooncological evaluation of the small pelvis

Positron emission tomography (PET) with the use of (¹⁸F)2-fluoro-d-2-desoxyglucose (FDG) has been investigated to be a highly sensitive and specific imaging modality in the diagnostic of primary and recurrent tumors and in the control of therapies in numerous non-urologic cancers. The aim of this review is to validate the significance of PET as a diagnostic tool in malignant urological tumors of the small pelvis. A systematic review of the current literature concerning the role of PET for malignant prostate, testicular and bladder tumors was carried out. The data indicate no additional role for PET in comparison with conventional imaging in tumor detection and local staging for prostate, bladder or testicular cancer. Tumor recurrence in prostate cancer seems to be more effectively identified with acetate and choline than with FDG, but this effect is more pronounced with higher PSA values. The value of PET in the identification of metastatic disease in either tumor entity can not be finally outlined as the clinical data are partly missing, controversial or in the process of evaluation. FDG-PET can be regarded as accepted imaging modality in the restaging of seminomatous germ cell tumors after chemotherapy.     

Evaluation of pleural diseases with FDG-PET imaging: preliminary report

BACKGROUND: Positron emission tomography (PET) with 18- fluorodeoxyglucose (FDG) is an accurate method for differentiating benign from malignant disease. The use of FDG-PET for the aetiological diagnosis of pleural disease was investigated in 25 patients. METHODS: PET was performed on each subject before invasive procedures were used to determine the aetiological diagnosis. The PET data were analysed by visual interpretation of coronal, sagittal, and transverse slices. RESULTS: Sixteen patients were found to have malignant pleural disease and nine had benign disease. All patients with histologically confirmed malignant disease showed FDG uptake within the pleural thickening which was intense in 14 cases and moderate in two. PET imaging showed the absence of FDG uptake and correctly categorised seven non-malignant lesions. Two patients with infectious pleural diseases showed a localised and moderate FDG uptake. CONCLUSION: Our preliminary results suggest that FDG-PET could be an effective tool for differentiating between benign and malignant pleural diseases.


     

The role of positron emission tomography in germ cell cancer

Positron emission tomography (PET) is a non-invasive tool for imaging regional metabolic processes, which adds another dimension to current anatomy-derived imaging techniques, i.e. metabolic imaging. To date, 2-¹⁸fluoro-2-deoxy-D-glucose (FDG) has been the only tracer used for imaging germ cell tumors (GCT), which can be distinguished from normal tissue by their different glucose utilization. However, FDG PET has several limitations: (1) inflammatory and granulomatous tissues also show extensive FDG uptake, (2) lesions <1 cm in size can often not be detected, and (3) mature teratoma is indistinguishable from normal and necrotic tissue. Studies assessing the clinical role of FDG PET in GCT suggest that the technique has a place as a standard tool in evaluating post chemotherapy seminoma residuals. Whether it also improves the assessment of the risks carried by clinical stage I non-seminoma patients and the early prediction of response to salvage chemotherapy is still under investigation, or at least needs to be confirmed by further trials. In relapsing patients with a mismatch between tumor markers and imaging data, FDG PET appears to be useful whenever salvage surgery is considered, although systematic trials are not yet available.     

Gouty tophus of the patella evaluated by PET imaging

We report a case of gouty tophus of the patella, a rare lesion, which was evaluated using positron emission tomography (PET). This modality, which uses a combination of an amino-acid analog emitter, l-[3-¹⁸F]-alpha-methyl tyrosine (FMT), which neglects malignancies, and a glucose analog emitter, ¹⁸F-fluoro-2-deoxy-d-glucose (FDG), which neglects benign lesions, simulating the radiographic findings, may be useful for the preoperative evaluation of gouty tophus occurring in patella partita, including detection, differentiation from malignant tumors, and possible pathogenetic diagnosis. Received: April 12, 2001 / Accepted: July 11, 2001     

Positron emission tomography and breast masses: Comparison with clinical,mammographic, and pathological findings

Background: Positron emission tomography (PET) is a means of imaging tissue based upon its metabolic activity. Initial studies in the field of oncology suggest that PET may be useful for diagnosis, staging, and treatment of various tumors. Methods: Twenty-eight patients with 37 breast lesions were studied with PET using [fluorine-18] 2-deoxy-2-fluoro-D-glucose (FDG) to assess which clinico-pathological characteristics relate to FDG accumulation by the primary tumor. Results: PET-FDG was found to successfully discriminate malignant from benign breast lesions (p=0.02) and identify axillary lymph node metastases. FDG uptake by the primary tumor was found to be independent of age, menopausal status, race, tumor size, laterality, histologic differentiation, ploidy, DNA index, estrogen or progesterone receptor value, pathologic stage, and serum glucose. Higher tumor nuclear grade and S-phase were associated with more FDG accumulation by the primary tumor compared with normal breast tissue. PET-FDG correctly identified five malignant lesions that were indeter-minant for cancer both on clinical breast examination and mammography and identified one occult cancer that was neither palpable nor apparent mammographically. PET-FDG correctly identified clinical occult axillary metastatic cancer in five patients. Conclusions: This study shows that PET-FDG imaging can distinguish malignant from benign breast lesions among a diverse group of patients and suggests that PET-FDG may not only allow for preoperative staging of patients but also provide information about prognosis. This study provides impetus for continued research into PET-FDG imaging of breast lesions, which could have a major impact on the treatment of breast cancer. Presented at the 46th Annual Cancer Symposium of the Society of Surgical Oncology, Los Angeles, California, March 18–21, 1993.     

Positron-emission tomography with 18F-2-fluoro-2-deoxy-D-glucose (18FDG-PET) in the diagnosis of retroperitoneal lymph-node metastases from testicular tumors

Summary In 1991, this prospectively designed study was started to assess the potentials of positron emission tomography with ¹⁸FDG in the diagnostic workup for the detection of lymph node metastases in testicular cancer, since there were no data available concerning this subject at this time. In 54 patients (27 patients with pure seminoma, 27 patients with non-seminomatous tumors) ¹⁸FDG-PET results were compared with the findings obtained with abdominal computed tomography, serum level of tumor markers (AFP, β -HCG), and the histopathological findings after primary or post-chemotherapy retroperitoneal lymph node dissection. In 21 patients with pure seminoma (clinical stage I according to the Lugano classification) ¹⁸FDG-PET results were identical with those of the abdominal computed tomography, so PET does not add relevant informations in this group of patients. In 7 patients presenting with non-seminomatous testicular cancer (stage I), PET was not able to detect the existing micrometastases in 4 patients. In 1/7 case PET examination showed a suspicious focal lesion, this lymph node had 2 micrometastases within inflammatory changes. In 1/7 patient ¹⁸FDG-PET definitely revealed metastatic lesions, while the CT scans where judged to be unobtrusive and tumor marker levels were within the normal range. In the 4 patients with pure seminomas stage II B and II C (N = 6), that have undergone retroperitoneal lymph node dissection following chemotherapy, ¹⁸FDG-PET correctly predicted absence of tumor in 3 out of these 4, and in 1/4 patient the benign nature of a persistent large tumor after two cycles of polychemotherapy was correctly identified wich eventually turned out to be a ganglioneuroma. This lesion falsely was classified as malignant tumor with abdominal computed tomography, and in 2/4 patients post-chemotherapy residual retroperitoneal lesions in the CT scans could not be assessed exactly whether or not malignant tumor was present. In 20 patients presenting with non-seminomatous testicular cancer (stage II and III) ¹⁸FDG-PET was able to demonstrate therapeutic effects of chemotherapy by showing decreasing tracer activity in those regions, that had hypermetabolic foci prior to chemotherapy. It became evident in testicular cancer that there is a single entity which is not characterized by increased glucose metabolism, the mature teratoma. In lesions detected by abdominal computed tomography which do not present increased ¹⁸FDG uptake, mature teratoma as well as scar/necrosis or rare other tumors with normal glucose metabolism can be supposed, but additional characteristics based on different ¹⁸FDG uptake were not observed. In 1/20 case post-chemotherapy PET scan detected a hypermetabolic lesion, which was suspicious for metastatic spread, but in the histopathological examination this lesion was identified as inflammatory tissue reaction. Based on the data reported here in ¹⁸FDG-PET cannot be considered a standard diagnostic tool in the staging examinations in testicular cancer. It is of clinical relevance in patients who present residual tumor after chemotherapy. In this situation ¹⁸FDG-PET is helpful in deciding whether or not a residual mass post-chemotherapy contains active tumor. ¹⁸FDG-PET can not replace retroperitoneal lymph node dissection for staging purposes.      

18F-Fluorodeoxyglucose Positron Emission Tomography: Useful Technique for Predicting Malignant Potential of Gastrointestinal Stromal Tumors

The malignant potential of gastrointestinal stromal tumors (GISTs) is difficult to diagnose before surgery because the diagnoses are based on tumor diameter and mitotic index. The progression of small GISTs is always observed because they do not seem to have malignant potential. ¹⁸F-Fluorodeoxyglucose (FDG)-positron emission tomography (PET) is a useful technique for assessing tumor activity. The objective of this study was to determine if FDG-PET is useful for predicting the malignant potential of gastric GISTs. Ten patients diagnosed with gastric GISTs participated. FDG-PET was performed on all of them before tumor resection. A whole-body image was initiated 40 minutes after the injection of 275 to 370 MBq FDG. FDG uptake was assessed by a standardized uptake value. All tumors had FDG uptake. There was a significant correlation between the FDG uptake and both the Ki67 index and the mitotic index but not the tumor diameter. The FDG uptake and malignant potential of gastric GISTs had a significant correlation. FDG-PET may be of considerable value for predicting the malignant potential of gastric GISTs before surgery. A gastric GIST with a high FDG uptake should be regarded as having malignant potential.     

Positron emission tomography for benign and malignant disease

Functional imaging using radiolabeled probes that specifically bind and accumulate in target tissues has improved the sensitivity and specificity of conventional imaging. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) has shown improved diagnostic accuracy in differentiating benign from malignant lesions in the setting of solitary pulmonary nodules. FDG-PET has become useful in preoperative staging of patients with lung cancer, and is being tested with many other malignancies for its ability to change patient management. This article provides an overview of the current status of FDG-PET and presents the challenges of moving toward routine use.     

F-18 FDG positron emission tomography in diagnosis and follow-up of patients with musculoskeletal tumors

The purpose of this study was to assess the value of F-18 FDG whole body positron emission tomography in the primary and follow-up diagnosis of musculoskeletal tumors.Between May 1994 and January 2000, 79 patients [36 females, 43 males; mean age: 44 years (9-78)] suffering from different musculoskeletal tumors were additionally examined with PET.In total, 100 whole body PET examinations (48 for primary staging, 52 for follow-up) were performed using a PET scanner [ECAT EXACT 47 (921)] with an axial field of view of 16.2 cm. The tracer was 370 MBq F-18 FDG. The results were compared to those achieved with conventional diagnostic tools such as CT, MRT, bone scan, and histology.In the primary staging, PET exhibited a sensitivity of 100% and a specificity of 50% (two false-positive results). In examinations for follow-up purposes, we found a sensitivity of 88.9% and a specificity of 92.0%. In the diagnosis of skeletal and extraskeletal metastases (100 PET inspections), the sensitivity was 87.5% and the specificity 89.7%.Besides this, PET was compared with standard diagnostic tools used in the follow-up procedures of those patients who had received chemo- and/or radiotherapy. In addition, the procedure was used to search for the unknown primary tumors in cases of secondary metastases in the skeleton and compared as well.PET with F-18 FDG as tracer has become an important additional method in the diagnosis of musculoskeletal tumors. It can be used for primary staging, search for metastases, and post therapeutic control.Negative results were seen when PET was used to search for metastases when the tumor was smaller than 5 mm, in cases of inflammatory diseases, and the differentiation of low-grade malignant tumors from benign lesions.     

Detection of local recurrence of soft-tissue sarcoma with positron emission tomography using [18F]fluorodeoxyglucose

Background: It is often difficult to detect a local recurrence of soft-tissue sarcomas due to disturbance of the normal anatomy by previous surgery and radiotherapy. The aim of this study was to assess the value of positron emission tomography (PET) with [¹⁸F]fluoro-2-deoxy-d-glucose (FDG) for detecting local recurrences. Methods: In the period 1992–1995, 17 patients with proven or suspected local recurrence of soft-tissue sarcoma were examined using FDG-PET. Fifteen of these patients were ultimately proven to have a recurrence. Results: Recurrence was visualized in 14 patients (93%). Small tumors (maximum diameter 0.5 cm) were as easily visible as large lesions (maximum diameter 20 cm). In one patient the PET scan was positive, but the recurrence could not be proven histologically. Recurrence was proven 1 year later. A recurrent low-grade liposarcoma was not visualized. The two patients with benign lesions had a negative PET scan. The mean glucose metabolic rate was calculated to be 13.2 μmol/100 g/min (range 1.9–28.4). A correlation was found between the histological malignancy grade and the metabolic rate (p<0.05; Kruskal-Wallis). Conclusion: PET with FDG is a useful addition to the diagnostic armamentarium for detecting local recurrence of soft-tissue sarcomas and provides an indication of the malignancy grade of the recurrent lesion. Presented at the 47th Annual Meeting of The Society for Surgical Oncology, Houston, Texas, March 17–20, 1994.     

Risk of malignancy in thyroid incidentalomas identified by fluorodeoxyglucose-positron emission tomography.

BACKGROUND: Thyroid tumors often exhibit increased metabolic activity, as evidenced by enhanced glucose uptake on positron emission tomography (PET) with use of (18)F-fluorodeoxyglucose (FDG). The incidence of new thyroid lesions found on routine FDG-PET has not been previously reported. METHODS: A retrospective review of all patients who underwent FDG-PET imaging at our institution from June 1, 1996, through March 15, 2001, identified patients with a newly diagnosed thyroid lesion. Thyroid incidentaloma was defined as a thyroid lesion seen initially on FDG-PET in a patient without a history of thyroid disease. Available follow-up data were documented. RESULTS: One hundred and two of 4525 FDG-PET examinations (2.3%) demonstrated thyroid incidentalomas. Eighty-seven of 102 patients had no thyroid histology because of other malignancies. Fifteen patients had thyroid biopsy: 7 (47%) with thyroid cancer, 6 (40%) with nodular hyperplasia, 1 with thyroiditis, and 1 with atypical cells of indeterminate origin. The average standardized uptake values were higher for malignant compared with benign lesions. CONCLUSIONS: Thyroid incidentaloma identified by FDG-PET occurred with a frequency of 2.3%. Of the thyroid incidentalomas that underwent biopsy, 47% were found to be malignant. Given the risk of malignancy, patients with new thyroid lesions on PET scan should have a tissue diagnosis if it will influence outcome and management. Standardized uptake values may be helpful in predicting benign versus malignant histology.     

Integrated FDG-PET-CT: its role in the assessment of bone and soft tissue tumors

Purpose  

The purpose of this study was to evaluate prospectively, whether integrated 2-deoxy-2-[¹⁸F]fluoro-d-glucose positron emission tomography-computed tomography (FDG-PET-CT) is more accurate for determination musculoskeletal tumors compared with separate interpretation of CT and FDG-PET, because most of the current clinical data come from patients studied with PET.     

The utility of F-18 fluorodeoxyglucose whole body PET imaging for determining malignancy in cystic lesions of the pancreas

Previous studies have suggested that whole body positron-emission tomography (PET) can distinguish between benign and malignant cysts of the pancreas. Patients were identified (n=68) who had undergone whole body PET imaging for a cystic lesion of the pancreas between Jan. 1997 and May 2005. Cross-sectional imaging studies were reviewed by a single blinded radiologist, and positive PET studies were reviewed by a blinded nuclear medicine physician. Operative resection was performed in 21 patients (31%), and 47 patients were managed with radiographic follow-up. F-18 Fluorodeoxyglucose (FDG)-avid lesions were identified in eight of the 68 patients (12%). Within the resected group of patients (n=21), four of the seven patients (57%) with either in situ or invasive malignancy (adenocarcinoma: 3 of 5, papillary mucinous carcinoma: 1 of 2) had positive PET imaging (mean SUV, 5.9; range 2.5-8.0), and 2 of the 14 patients (14%) with benign lesions had positive PET imaging (serous cystadenoma, n=1, SUV=3.3; pseudocyst n=1, SUV=2.7). All lesions proven to be malignant with increased FDG uptake had highly suspicious findings on cross-sectional imaging. Within the group of resected patients, the sensitivity of PET for identifying malignant pathology was 57%, and the specificity was 85%. The sensitivity and specificity of PET for malignancy in this study was lower than previously reported, and PET findings did not identify otherwise occult malignant cysts. We do not believe whole body FDG-PET to be essential in the evaluation of cystic lesions of the pancreas.     

Overexpression of hexokinase-2 in giant cell tumor of bone is associated with false positive in bone tumor on FDG-PET/CT

Introduction

The aim of the current study was to evaluate the usefulness of maximum standardized uptake value (SUV_max) in 2-deoxy-2-F¹⁸-fluoro-d-glucose positron emission tomography combined with computed tomography (18F-FDG-PET/CT) for preoperative differential diagnosis between benign and malignant bone tumors.

Materials and methods

Seventy-nine patients with bone tumors were examined by FDG-PET prior to histopathological diagnosis. The SUV_max was calculated and compared between benign and malignant lesions, and among different histopathological subgroups, to identify false-positive histological subtypes.

Results

There was a statistically significant difference in the SUV_max of benign (3.7?±?3.3; n?=?17) and malignant (5.3?±?3.3; n?=?62) bone tumors. However, receiver operating characteristic curve analysis revealed the poor accuracy of this distinction. The cut-off value was determined to be 2.6, while the value of sensitivity and specificity was calculated to be 74.2 and 64.7?%, respectively. Giant cell tumor of bone (9.0?±?2.0; n?=?5) displayed a higher SUV_max than osteosarcoma (4.2?±?2.3; n?=?18). Immunohistochemical analysis demonstrated that markers of these cancers, hexokinase-2 (HK-2) and glucose transporter type 1 (GLUT-1), supported our findings.

Conclusion

The poor accuracy of SUV_max in 18F-FDG-PET/CT in distinguishing malignant from benign bone tumors was confirmed; some benign bone tumors showed high FDG uptake. Giant cell tumor of bone was a major false-positive histopathological subtype of bone tumors, showing high FDG accumulation. HK-2 contributed significantly to FDG uptake, whereas GLUT-1 appeared to play no role in FDG uptake in giant cell tumor of bone.     

Evaluation of 18F-2-deoxy-2-fluoro-<Emphasis Type="SmallCaps">d</Emphasis>-glucose Positron Emission Tomography for Gastric Cancer

Positron emission tomography (PET) with ¹⁸F-2-deoxy-2-fluoro-d-glucose (FDG) has been investigated as a means of detecting certain primary tumors and their metastatic disease in recent years. The aim of this study was to compare the performance of FDG-PET and operative assessment with formal pathologic staging. Altogether, 85 patients had undergone surgical treatment for gastric cancer with curative intent, with FDG-PET preoperatively. The results using FDG-PET were compared with those using computed tomography (CT); they were also correlated with the pathologic findings. For quantitative analysis, the regional tumor uptake was measured by the standard uptake value (SUV) using a region of interest technique. Using FDG-PET, the primary tumor was visualized in 75.2% of patients. A comparison of the FDG uptake and the clinicopathologic findings showed that there was a significant association between FDG uptake and the depth of invasion, the size of the tumor, and lymph node metastasis. FDG-PET scans had less accuracy for diagnosing locoregional lymph nodes than CT because of a significant lack of sensitivity (23.3% vs. 65.0%). The survival rate for patients with high FDG uptake (SUV > 4) was significantly lower than that for those with low FDG uptake (SUV < 4) (p < 0.05). FDG-PET was successful in detecting the primary gastric cancer lesion but not for finding early-stage gastric cancers. Detection of nodal metastasis also was not possible by FDG-PET. However, FDG-PET appears to provide important additional information concerning the aggressiveness of the tumor and the prognosis in patients with gastric cancer.     

Prospective evaluation of soft tissue masses and sarcomas using fluorodeoxyglucose positron emission tomography

BACKGROUND: The differentiation of soft tissue sarcoma (STS) from benign masses is difficult owing to their clinical and radiological similarities. Accurate staging is hindered by the large number of sites at which metastases may be found. This study examined the value of whole-body [18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) in patients presenting with soft tissue masses. METHODS: Thirty patients with a soft tissue mass suspected to be malignant were evaluated with FDG PET. The images were evaluated qualitatively and quantitatively for uptake of FDG to determine whether benign lesions could be differentiated from malignant tumours, and for the presence of metastases. RESULTS: Thirty-one masses were removed from 30 patients; 12 were benign and 19 were malignant STSs. Using qualitative assessment of the FDG PET images, all the high-grade STSs (n = 12) were correctly identified, but low-grade STS (n = 7) could not be differentiated from a benign lesion. Using a quantification assessment, there was a 95 per cent sensitivity and a 75 per cent specificity in diagnosing STS. Three patients had metastases at presentation; two were correctly identified by FDG PET. Conclusion: FDG PET has a role in distinguishing high-grade STS from low-grade or benign STS and may have a role in staging malignant tumours.     

18F-FDG PET/CT在胆道系统恶性肿瘤中的应用

目的探讨~(18)F-FDG PET/CT诊断胆道系统恶性肿瘤的价值。方法回顾性分析34例临床疑似胆道恶性肿瘤患者的PET/CT影像资料,均获得术后病理结果,其中12例经手术切除淋巴结或淋巴结穿刺活检对18枚淋巴结获得病理诊断;与病理结果对照,计算PET/CT对胆道恶性病变原发灶、淋巴结转移的灵敏度、特异度、阳性预测值、阴性预测值及准确率。结果 34例中,31例为恶性病变,3例为良性病变。PET/CT诊断胆道恶性肿瘤原发灶的灵敏度100%(31/31),特异度66.67%(2/3),阳性预测值96.88%(31/32),阴性预测值100%(2/2),准确率97.06%(33/34)。胆道恶性病变原发灶最大标准摄取值(SUV_(max))为8.42±4.27;3例胆道良性疾病SUV_(max)分别为12.90、2.00及1.90。共18枚淋巴结获得病理结果,包括转移性淋巴结13枚,良性增生5枚。PET/CT诊断淋巴结转移的灵敏度76.92%(10/13),特异度60.00%(3/5),阳性预测值83.33%(10/12),阴性预测值50.00%(3/6),准确率72.22%(13/18)。结论 PET/CT对胆道系统恶性肿瘤的诊断具有重要价值。     

Preoperative evaluation of thyroid nodules with 18FDG-PET/CT

BACKGROUND: Fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography ((18)FDG-PET/CT) has become an important tool in the postoperative management of de-differentiated thyroid cancer. The utility of this imaging modality in the preoperative assessment of thyroid nodules is unclear. This study was designed to determine whether (18)FDG-PET/CT improves the preoperative diagnosis of thyroid nodules. METHODS: A total of 31 patients with 48 lesions underwent fine-needle aspiration and (18)FDG-PET/CT before surgical resection of thyroid nodules. PET/CT images were obtained 1 hour after intravenous administration of (18)FDG. Standard uptake values were calculated for regions of increased (18)FDG uptake. CT scans were evaluated to identify thyroid pathology. Final pathologic diagnoses were compared with PET/CT findings. RESULTS: Fifteen of 48 lesions were malignant and 33 were benign. Nine of 15 malignant lesions were (18)FDG-avid (sensitivity 60%). Thirty of 33 benign lesions were (18)FDG-cold (specificity 91%). Positive and negative predictive values were 75% and 83%, respectively. CONCLUSIONS: (18)FDG-PET/CT provides a high negative predictive value for malignancy, making this a potentially useful tool in the evaluation of thyroid nodules with indeterminate fine-needle aspiration. However further studies with larger sample sizes are needed to determine the true efficacy of this test.