Evaluation of 18F-fluorothymidine positron emission tomography ([18F]FLT-PET/CT) methodology in assessing early response to chemotherapy in patients with gastro-oesophageal cancer.

BACKGROUND: 3'-Deoxy-3'-[18F]fluorothymidine ([18F]FLT) PET has limited utility in abdominal imaging due to high physiological hepatic uptake of a tracer. We evaluated [18F]FLT-PET/CT combined with a temporal-intensity information-based voxel-clustering approach termed kinetic spatial filtering (KSF) to improve tumour visualisation in patients with locally advanced and metastatic gastro-oesophageal cancer and as a marker of early response to chemotherapy. Dynamic [18F]FLT-PET/CT data were collected before and 3 weeks post first cycle of chemotherapy. Changes in tumour [18F]FLT-PET/CT variables were determined. Response was determined on contrast-enhanced CT after three cycles of therapy using RECIST 1.1. RESULTS: Ten patients were included. Following application of the KSF, visual distinction of all oesophageal and/or gastric tumours was observed in [18F]FLT-PET images. Among the nine patients available for response evaluation (RECIST 1.1), three patients had responded (partial response) and six patients were non-responders (stable disease). There was a significant association between Ki-67 and all baseline [18F]FLT-PET parameters. Area under the curve (AUC) from 0 to 1 min was associated with treatment response. CONCLUSIONS: The results of this study indicate that application of the KSF allowed accurate visualisation of both primary and metastatic lesions following imaging with the proliferation marker, [18F]FLT-PET/CT. However, [18F]FLT-PET uptake parameters did not correlate with response. Instead, we observe significant changes in tracer delivery following chemotherapy suggesting that further [18F]FLT-PET/CT studies in this tumour type should be undertaken with caution.

Glucagon increases energy expenditure independently of brown adipose tissue activation in humans.

AIMS: To investigate, for a given energy expenditure (EE) rise, the differential effects of glucagon infusion and cold exposure on brown adipose tissue (BAT) activation in humans. METHODS: Indirect calorimetry and supraclavicular thermography was performed in 11 healthy male volunteers before and after: cold exposure; glucagon infusion (at 23 °C); and vehicle infusion (at 23 °C). All volunteers underwent (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET)/CT scanning with cold exposure. Subjects with cold-induced BAT activation on (18)F-FDG PET/CT (n = 8) underwent a randomly allocated second (18)F-FDG PET/CT scan (at 23 °C), either with glucagon infusion (n = 4) or vehicle infusion (n = 4). RESULTS: We observed that EE increased by 14% after cold exposure and by 15% after glucagon infusion (50 ng/kg/min; p < 0.05 vs control for both). Cold exposure produced an increase in neck temperature (+0.44 °C; p < 0.001 vs control), but glucagon infusion did not alter neck temperature. In subjects with a cold-induced increase in the metabolic activity of supraclavicular BAT on (18)F-FDG PET/CT, a significant rise in the metabolic activity of BAT after glucagon infusion was not detected. Cold exposure increased sympathetic activation, as measured by circulating norepinephrine levels, but glucagon infusion did not. CONCLUSIONS: Glucagon increases EE by a similar magnitude compared with cold activation, but independently of BAT thermogenesis. This finding is of importance for the development of safe treatments for obesity through upregulation of EE.

Transplantation and Debulking Procedures for Neuroendocrine Tumors.

An array of treatment modalities is currently available in the management of patients with neuroendocrine tumors (NETs). Complete resection of the primary tumor and all metastatic lesions represents the only approach possessing intent to cure. However, due to patients' disease frequently being at an advanced stage on initial diagnosis only a minority of individuals are candidates for radical procedures. Cytoreductive surgery (debulking) may potentially confer improvements in quality of life and prolong overall survival. In light of the recent introduction of effective nonsurgical treatment options, the indication for cytoreductive surgery needs to be carefully assessed. The presence of nonresectable liver metastases is not a contraindication for resection of the primary tumor including locoregional disease in small bowel NETs. Resection of primary pancreatic NETs in the setting of unresectable metastatic liver disease may have a beneficial effect on the prognosis of selected patients with a tumor requiring less aggressive local surgery. Liver transplantation presents a generally accepted approach in meticulously selected patients with unresectable liver metastases. Stringent and validated selection criteria are not available. While overall survival is satisfactory, high recurrence rates hinder outcomes and call for the development and implementation of neoadjuvant and adjuvant concepts. Advances in intestinal transplantation over time may justify consideration of an individual with advanced neuroendocrine tumor disease unresponsive to standard medical or surgical treatment.

Modified liver-free multivisceral transplantation for a metastatic small bowel neuroendocrine tumor: a case report.

Neuroendocrine tumors originating from the small bowel frequently metastasize to the lymph nodes and/or liver. Although surgical extirpation of the primary tumor and locoregional metastases epitomizes the management of patients with such tumors, this is not always possible with conventional surgical techniques. Nonresectable, slow-growing tumors involving the mesenteric root represent a generally accepted indication for deceased donor intestinal and multivisceral transplantation. Furthermore, vascularized sentinel forearm flaps offer opportunities for monitoring graft rejection and tailoring immunosuppression regimens. Here, we report the first documented case of modified liver-free multivisceral transplantation preceded by neoadjuvant 177-lutetium peptide receptor radionuclide therapy in a patient with a small bowel neuroendocrine tumor and extensive lymph node metastases in the mesenterium. At a follow-up of 21 months the patient is biochemically and radiologically disease-free.

The role of early ¹8F-FDG PET/CT in prediction of progression-free survival after 9°Y radioembolization: comparison with RECIST and tumour density criteria.

PURPOSE: This study evaluated the ability of (18)F-FDG PET/CT imaging to predict early response to (90)Y-radioembolization in comparison with contrast-enhanced CT (CECT) using RECIST and lesion density (Choi) criteria. Progression-free survival (PFS) in patients with liver metastases at 2 years and decline in tumour markers were the primary end-points of the study. METHODS: A total of 121 liver lesions were evaluated in 25 patients (14 men, 11 women) with liver-dominant metastatic colorectal cancer who underwent (18)F-FDG PET/CT and CECT before and 6-8 weeks after treatment. Changes in SUV(max), tumour density measured in terms of Hounsfield units and the sum of the longest diameters (LD) were calculated for the target liver lesions in each patient. The patient responses to treatment were categorized using EORTC PET criteria, tumour density criteria (Hounsfield units) and RECIST, and were correlated with the responses of tumour markers and 2-year PFS using Kaplan-Meier plots and the log-rank test for comparison. Multivariate proportional hazards (Cox) regression analysis was performed to assess the effect of relevant prognostic factors on PFS. RESULTS: Using (18)F-FDG PET/CT response criteria, 15 patients had a partial response (PR) and 10 patients had stable disease (SD), while using RECIST only 2 patients had a PR and 23 had SD. Two patients had a PR, 21 SD and 2 progressive disease using tumour density criteria. The mean changes in SUV(max), sum of the LDs and tumour density after treatment were 2.9 ± 2.6, 7.3 ± 14.4 mm and 1.9 ± 13.18 HU, respectively. Patients who had a PR on (18)F-FDG PET/CT had a mean decrease of 44.5 % in SUV(max) compared to those with SD who had a decrease of only 10.3 %. The decreases in SUV(max) and sum of the LDs were significant (p < 0.0001, p < 0.05, respectively) while the decrease in tumour density was not (p > 0.1065). The responses on the (18)F-FDG PET/CT studies were highly correlated with the responses of tumour markers (p < 0.0001 for LDH, p = 0.01 for CEA and p = 0.02 for Ca19-9), while the responses on the CECT studies using both RECIST and tumour density criteria were not significantly correlated with the responses of tumour markers. The responses on (18)F-FDG PET/CT studies also significantly predicted PFS (the median PFS in those with a PR was 12.0 months and in those with SD was 5 months, p < 0.0001), while RECIST and tumour density did not significantly predict PFS. Multivariate analysis demonstrated that responses on (18)F-FDG PET/CT studies and decreases in SUV(max) of ≤ 2.0 were the strongest predictors of PFS. CONCLUSION: Early response assessment to (90)Y-radioembolization using (18)F-FDG PET/CT is superior to RECIST and tumour density, demonstrating a correlation with tumour markers and significantly predicting PFS in patients with liver metastases. This could enable early response-adapted treatment strategies to be employed.

A comparison of the performance of 68Ga-DOTATATE PET/CT and ¹²³I-MIBG SPECT in the diagnosis and follow-up of phaeochromocytoma and paraganglioma.

PURPOSE: To compare the sensitivity of (123)I-metaiodobenzylguanidine (MIBG) SPECT and (68)Ga-DOTATATE PET/CT in detecting phaeochromocytomas (PCC) and paragangliomas (PGL) in the initial diagnosis and follow-up of patients with PCC and PGL disease. METHODS: Retrospective analysis of 15 patients with PCC/PGL who had contemporaneous (123)I-MIBG and (68)Ga-DOTATATE imaging. RESULTS: Of the 15 patients in the series, 8 were concordant with both modalities picking up clinically significant lesions. There were no patients in whom both modalities failed to pick up clinically significant lesions. There was discordance in seven patients: 5 had positive (68)Ga-DOTATATE and negative (123)I-MIBG, and 2 (12 and 14) had negative (68)Ga-DOTATATE and positive (123)I-MIBG. Utilizing (123)I-MIBG as the gold standard, (68)Ga-DOTATATE had a sensitivity of 80 % and a positive predictive value of 62 %. The greatest discordance was in head and neck lesions, with the lesions in 4 patients being picked up by (68)Ga-DOTATATE and missed by (123)I-MIBG. On a per-lesion analysis, cross-sectional (CT and MRI) and (68)Ga-DOTATATE was superior to (123)I-MIBG in detecting lesions in all anatomical locations, and particularly bony lesions. CONCLUSION: First, (68)Ga-DOTATATE should be considered as a first-line investigation in patients at high risk of PGL and metastatic disease, such as in the screening of carriers for mutations associated with familial PGL syndromes. Second, if (123)I-MIBG does not detect lesions in patients with a high pretest probability of PCC or PGL, (68)Ga-DOTATATE should be considered as the next investigation. Third, (68)Ga-DOTATATE hould be considered in preference to (123)I-MIBG in patients in whom metastatic spread, particularly to the bone, is suspected.

In high risk hypertensive subjects with incidental and unilateral renal artery stenosis percutaneous revascularization with stent improves blood pressure control but not glomerular filtration rate.

AIM: In high-risk hypertensive subjects (HTs) with incidental unilateral renal artery stenosis (RAS), the effectiveness of percutaneous revascularization with stent (PR-STENT) on blood pressure (BP) and glomerular filtration rate (GFR) is not established. METHODS: Eighteen HTs aged 65.7 ± 9.2 years with angiographically diagnosed unilateral RAS (≥ 60%) were randomized to receive PR-STENT (N=9) or to NO-STENT (N=9). BP (mercury sphygmomanometer) and GFR (99mTc-DTPA clearances during renal scintigraphy) were evaluated yearly for three years. Echo-Doppler of renal arteries was performed to verify the anatomic patency and flow velocities of the reperfused artery. Analysis of variance compared BP and GFR values changes from baseline to the follow-up; differences for continuous variables were evaluated between groups with the Tukey's post hoc test after adjustment for age, change of BP between baseline and at the follow-up, GFR and body mass index (BMI). RESULTS: Baseline systolic BP and GFR values were not different between groups. The significantly greater GFR increase observed in PR-STENT than in NO-STENT at univariate analysis at the end of follow-up (62.5 ± 19.2 vs. 42.24 ± 17.6, P<0.02) disappeared after adjustment for confounding factors. However, systolic BP remained significantly lower in PR-STENT than in NO-STENT (140.1 ± 4.6 vs. 170.0 ± 8.3, P<0.0001) also after adjustment for age, GFR and BMI. CONCLUSION: PR-STENT reduces systolic BP without improving GFR. Due to the strong association between high BP and renal damage, this study raises the question on whether PR-STENT should be performed in all HTs with unilateral and incidental RAS.

Arterial hypertension and thyroid disorders: what is important to know in clinical practice?

This review describes the pathogenic mechanisms of blood pressure (BP) regulation and long-term control in thyroid disorders. Variations from the euthyroid status affect virtually all physiological systems but the effects on the cardiovascular system are particularly pronounced. Thyroid disorders induce several hemodynamic changes leading to elevated BP as a consequence of their interaction with endothelial function, vascular reactivity, renal hemodynamic and renin-angiotensin system. However, in thyroid disorders, the regulation of BP and the development and maintenance of variable forms of arterial hypertension (HT) are different. Hyperthyroidism results in an increased endothelium-dependent responsiveness secondary to the shear stress induced by the hyperdynamic circulation, and contributes to reduce vascular resistance. Conversely, hypothyroidism is accompanied by a marked decrease in sensitivity to sympathetic agonists with an increase of peripheral vascular resistance and arterial stiffness. Furthermore in animal models, hypothyroidism reduces the endothelium-dependent and nitric oxide-dependent vasodilatation. HT due to thyroid disorders is usually reversible with achievement of euthyroidism, but in some cases pharmacological treatment for BP control is required. In hyperthyroidism, ß-blockers are the first-choice treatment to control BP but when they are contraindicated or not tolerated, ACE-inhibitors or calcium-channel blockers (CCB) are recommended. Hypothyroidism is a typical low rennin HT form showing a better antihypertensive response to CCB and diuretics; indeed in hypothyroidism a low-sodium diet seems further to improve BP control. Randomized clinical trials to compare the efficacy on BP control of the antihypertensive treatment in thyroid disorders are needed.

Modern PET imaging for paragangliomas: relation to genetic mutations.

AIM AND METHODS: Paragangliomas (PGL) are neural crest-derived tumours that are found along the autonomic neural network throughout the body and can be multiple and/or metastatic. Nuclear medicine imaging in combination with conventional imaging is required to fully delineate the extent of the disease. The performance of molecular imaging modalities is widely dependent on tumour biology. RESULTS: In the present paper we discuss the recent publications focused on the role of positron emission tomography (PET) imaging and the relationship between tracer uptake patterns and genetic mutations associated with the disease. CONCLUSION: Recent advances in genetic and molecular pathogenesis of PGL have allowed for the identification of new molecular diagnostic and therapeutic radiopharmaceuticals tailored to genetic abnormalities. However, the optimal diagnostic imaging algorithm remains to be determined.

Diagnostics of neuroendocrine tumours.

Neuroendocrine tumours (NETs) are rare pathologies which origin from neuroectodermic and endodermic cells and that can produce peptides and amino acids. About 70% of NETs derive from gastroenterohepatic (GEP) system and the other 30% from the different sites through the body. They are distinguished into single and multiple localizations and also into sporadic, familial multiple endocrine-related forms and recurrent forms. Moreover, when they produce hormones they usually are symptomatic; yet, they are characterized by the synthesis and secretion in the blood stream of several tumor-specific markers or can express somatostatin receptors in their cellular surface. The diagnosis and follow-up of NETs rely on laboratory studies, histopathology and the combination of anatomical and functional imaging, with the latter being the main method for monitoring response to therapy. In recent years, nuclear medicine has contributed to the impressive development of the knowledge of NETs in terms of biology (receptor scintigraphy), pharmacology (development of new tracers) and therapy (radiometabolic therapy). Nuclear medicine procedures for diagnosis and treatment of NETs are based on the biological properties of these tumours: the expression of somatostatin receptors. Somatostatin receptor scintigraphy not only has a crucial role in diagnosis and staging of NETs, but also in assessing suitability for treatment with cold and radiolabelled somatostatin analogues, as well as in monitoring response to treatment and detecting recurrent disease. In conventional nuclear medicine, the two most important functional imaging modalities are ¹¹¹In-octrescan and ¹²³I-MIBG. Over the last 5 years, due to the development of new tracers, such as 68Ga labelled-DOTA-peptides PET and ¹8F-DOPA, PET has also been employed with significant benefits in the diagnosis and management of NETs.

Minimally invasive radio-guided surgery for primary hyperparathyroidism: From preoperative to intraoperative localization imaging.

The introduction and successful implementation of minimally invasive radio-guided parathyroidectomy (MIRP) has revolutionized the surgical approach to remove parathyroid adenomas. A prerequisite for such success is an accurate localization of the offending adenoma. To achieve this goal, a multimodality approach is commonly employed using a combination of anatomical and functional imaging. Of the anatomical cross-sectional techniques, ultrasonography is the most widely available but is operator-dependent and has reduced sensitivity, specially in the presence of thyroid nodules. Similarly, computed tomography and magnetic resonance imaging have low sensitivities but provide value in detecting retrotracheal, retro-oesophageal and mediastinal adenomas. Functional imaging with 99(m)Tc-Sestamibi is currently the most vital imaging procedure in this respect with variable protocols including dual-phase and dual isotope imaging. The sensitivity and specificity can improve by acquiring in single photon emission tomography (SPECT) mode and using co-registration with low dose CT to provide anatomical data (SPECT/CT). The current recommended approach is the combination of functional imaging with 99(m)Tc-Sestamibi and high-resolution ultrasound (US), supplemented with intraoperative gamma probe in certain cases and quick persurgical measurement of parathyroid hormone. This review aims to explore the utility of various imaging modalities, alone and in combination, in detecting parathyroid adenoma and facilitating the current approach of MIRP.

Functional assessment in the multimodality imaging of pancreatic neuro-endocrine tumours.

Pancreatic neuroendocrine tumours comprise a heterogeneous group that are rare but could result in serious manifestations. Surgical excision provides the best approach to treatment but many patients may have small lesions that are difficult to detect, or present with wide spread disease by the time of diagnosis. In addition to clinical assessment and biochemical tests, imaging is a major factor in establishing the diagnosis. Cross-sectional imaging such as US, CT and MR, play a major role in the initial assessment. However, they may miss small lesions or metastatic spread. Functional Imaging became possible with the development of somatostatin receptor imaging using 111In-octreotide, which when combined with anatomical imaging could provide enhanced detection. A major improvement has been achieved by combining receptor and PET inaging through the use of 68Ga-DOTA complexes that have been shown to have a much better sensitivity than other imaging modalities and can provide the basis for radionuclide treatment with 90Y or 177Lu labelled with DOTA complexes.

Dual PET/CT with (18)F-DOPA and (18)F-FDG in metastatic medullary thyroid carcinoma and rapidly increasing calcitonin levels: Comparison with conventional imaging.

BACKGROUND: To evaluate the role of a multi-imaging PET with (18)F-DOPA and (18)F-FDG in comparison with conventional imaging (CI) in recurrent medullary thyroid carcinoma (MTC). METHODS: 18 MTC patients who had thyroidectomy were included; they presented with elevated and rapidly increasing calcitonin levels during follow up. CI had revealed metastatic deposits in 9 patients. Patients were referred to us for a PET/CT with (18)F-DOPA and (18)F-FDG. Histologic/cytologic confirmation of recurrent MTC was obtained in at least one PET-positive lesion in all patients. RESULTS: Foci of abnormal uptake were observed in 15 patients at (18)F-DOPA and in 11 at (18)F-FDG; 8 patients showed the same number of positive lesions with both tracers, 2 showed more lesions on (18)F-FDG, 1 was positive at (18)F-FDG alone and 5 at (18)F-DOPA alone. In 3 patients with a DOPA-positive loco-regional relapse a re-operation with curative intent was offered. SUV(max) values were higher for (18)F-FDG compared to (18)F-DOPA (mean 12.7+/-4.1 vs. 5.5+/-2.1, p<0.05). Calcitonin was higher in PET-positive patients compared to PET negative ones, while no significant differences were observed between (18)F-DOPA and (18)F-FDG positive patients. CONCLUSIONS: In MTC patients with rapidly increasing calcitonin levels during follow up, (18)F-DOPA has a good sensitivity and a complementary role with (18)F-FDG PET/CT in detecting metastatic deposits. In our experience, the sensitivity of a multi-imaging (18)F-DOPA &(18)F-FDG PET/CT approach is greater than that obtained with CI. The higher SUV(max) values found with (18)F-FDG in some patients may reflect more aggressive tumors.

Endocrine tumors: the evolving role of positron emission tomography in diagnosis and management.

Endocrine tumors comprise a range of benign and malignant conditions that produce a spectrum of clinical symptoms and signs depending on the specific hormones they produce. The symptoms and presentations of these tumors are often independent of their size and location. Because of their expression of cell membrane receptors or production of specific types of hormones or peptides, endocrine tumors can be identified with functional radionuclide imaging much more readily compared to standard cross-sectional imaging. In recent years, 18F-fluoro-deoxy- D-glucose positron emission tomography (18F-FDG-PET) has emerged as a useful tool for diagnosing and assessing many tumors. In this review we describe how PET, using 18F-FDG and other radiopharmaceuticals can be useful in the diagnosis and management of a wide range of endocrine tumors.

Multiorgan dysfunctions in diabetic patients: the role of functional imaging.

Functional imaging plays a central role in the evaluation of some of the clinical problems faced by diabetic patients. In cardiovascular disease, myocardial perfusion imaging, particularly when complemented by gated SPECT, is a powerful tool not only for establishing the diagnosis of coronary artery disease, but also for providing prognostic information in both the general and diabetic populations. Although promising, its role in screening of asymptomatic diabetic patients is yet to be established, and its role as a potential 'one-stop shop' also needs further study. PET is currently the gold standard for viability assessment, and also provides prognostic data, but its widespread use is limited by cost and availability. Hybrid imaging with PET/CT is promising, and could revolutionise cardiac imaging by combining functional and anatomic information. In the investigation of the diabetic foot, labelled leukocyte imaging is the nuclear medicine test of choice to diagnose osteomyelitis. It is likely that SPECT/CT will further improve diagnostic accuracy, but more studies are needed. Combined leukocyte and bone marrow imaging is of value in distinguishing osteomyelitis from neuropathic osteoarthropathy in the diabetic foot; PET and PET/CT may also be of value in these cases, but their wider role is currently inconclusive. The value of bone scintigraphy in the diabetic foot, even as a screening test, is questionable. Functional imaging methods can also be employed in the evaluation of other diabetic complications, including the assessment of left ventricular function, renal scarring and gastric emptying, but these methods are not widely used in current clinical practice.

Clinical indications for Gallium-68 positron emission tomography imaging.

BACKGROUND: (68)Ga-PET imaging is showing slow but steady progress when compared to (18)F-FDG PET. The advantage of in-house preparation of (68)Ga without necessity of a cyclotron, and the new generator configuration with future possibility of freeze-dried kits would make it a promising PET agent for the future. METHODS: An exhaustive literature exploration was performed using the search engines High-Wire Press, Pubmed, Embase and library databases. Recent reviews on the subject and up-to-date studies on the topic were found that described the role of (68)Ga-PET imaging. Clinical experiences, including our own are described. RESULTS: Recent resurgence in development of peptides labelled with radiometals, for diagnostic and therapeutic purposes, resulted in a new beginning for (68)Ga-PET imaging. Pre-clinical experience employing animal models and investigation of tracer kinetics/tumour uptake measurements using dynamic (68)Ga-PET have provided data regarding identification of Somatostatin receptors subtypes on many tumours. Present published experiences including our own support these and highlight current clinical utility of (68)Ga-PET imaging. (68)Ga-DOTATOC and (68)Ga-DOTANOC are the most prominent radiopharmaceuticals used nowadays. CONCLUSION: (68)Ga-PET is employed in the management of neuroendocrine tumours and neural crest tumours (phaeochromocytoma and paraganglioma) with diagnostic and therapeutic implications where it compliments present radiologic and scintigraphic procedures. Diagnosis and radiotherapy treatment planning for meningiomas in pertinent clinical setting is another potential use of (68)Ga-PET. Limited studies have shown its utility in prostate cancer but further studies are contemplated. Therefore, current experience tends to open a new horizon for the clinical utility of (68)Ga-PET imaging in future.

Multimodality imaging of the parathyroid glands in primary hyperparathyroidism.

Primary hyperparathyroidism is a common endocrine disorder, affecting approximately 1 in 500 women and 1 in 2,000 men. Surgical removal of the hyperfunctioning parathyroid gland is the primary curative treatment. The last decade has witnessed the development of minimally invasive parathyroidectomy, which is based on the fact that the vast majority of cases are caused by single adenomas. However, the success of this technique relies on accurate preoperative localisation of the parathyroid lesions. The imaging modalities used vary at different institutions according to local expertise and availability, but include high resolution ultrasound, radionuclide studies, computed tomography (CT) and magnetic resonance imaging (MRI). Ultrasound and 99mTc sestamibi scintigraphy, particularly when complemented by single photon emission computed tomography (SPECT), are currently the imaging techniques of choice for preoperative localisation of parathyroid adenomas; a combination of the two methods further improves the sensitivity and accuracy of detection. CT is less commonly used for preoperative localisation and usually reserved for cases of failed parathyroidectomy, for the detection of suspected ectopic glands. MRI appears to be useful in patients with persistent or recurrent hyperparathyroidism, who have previously undergone surgery. Cross-sectional imaging is also useful in cases where the findings at sonography and scintigraphy are discordant. SPECT/CT appears promising, but further studies are needed to evaluate its role in preoperative localisation.

Review. 18F-FDG PET in the diagnosis and follow-up of thyroid malignancy.

The diagnosis of carcinoma of the thyroid is usually made in the process of investigating a thyroid nodule with clinical examination, Technetium-99m scan, ultrasonography and fine-needle aspiration (FNA) cytology. The follow-up is mainly based on 123-iodine and 131-iodine scans and serum thyroglogulin measurement. The aim of the present review was to establish the role of 18F-FDG PET in the differential diagnosis of doubtful thyroid nodules and in the follow-up of patients with increased serum thyroglobulin levels and negative iodine-scan. It remains to be defined if metabolic imaging with PET could be a useful routine procedure in the management of thyroid tumours since the majority of them are well-differentiated and therefore have less avidity to 18F-FDG. In the present work we collected the specific literature derived from MEDLINE over the last 10 years to clarify the potential clinical value of 18F-FDG PET in thyroid malignancies. An emerging role for 18F-FDG PET is in the assessment of incidental finding of a thyroid nodule which, when showing high FDG uptake should be regarded as a possible malignancy that needs further assessment. Another well-documented role for 18F-FDG PET is in the investigation of cases of established well-differentiated thyroid carcinomas presenting with high thyroglobulin and negative iodine imaging. An increase of the 18F-FDG uptake in these tumours indicates a shift towards lesser differentiation (with more aggression and poor prognosis) and may benefit from alternative management. 18F-FDG PET can be considered a routine functional imaging method in detecting iodine-negative recurrent disease in thyroid cancer patients with elevated serum thyroglobulin levels during follow-up. 18F-FDG PET seems to be useful also in differential diagnosis of suspected thyroid nodules, especially using the semi-quantitative SUV analysis.