The added value of [18F]fluoro-L-DOPA PET in the diagnosis of hyperinsulinism of infancy: a retrospective study involving 49 children

Congenital hyperinsulinism and surgical outcome in a single tertiary center in Brazil

OBJECTIVE

Congenital hyperinsulinism (CHI) is a heterogeneous genetic disease characterized by increased insulin secretion and causes persistent hypoglycemia in neonates and infants due to dysregulation of insulin secretion by pancreatic β cells. Babies with severe hypoglycemia and for whom medical treatment has been ineffective usually require surgical treatment with near-total pancreatectomy. To evaluate the clinical and surgical aspects affecting survival outcomes in babies diagnosed with CHI in a single tertiary care center.

METHODS

Retrospective Cohort study involving a single university tertiary center for the treatment of CHI. The authors study the demographics, clinical, laboratory, and surgical outcomes of this casuistic.

RESULTS

61 % were female, 39 % male, Birth weight: 3576 g (±313); Age of onset of symptoms: from the 2nd hour of life to 28 days; Time between diagnosis and surgery ranged between 10 and 60 days; Medical clinical treatment, all patients received glucose solution with a continuous glucose infusion and diazoxide. 81 % of the patients used corticosteroids, 77 %. thiazide, 72 % octreotide, 27 % nifedipine; Neurological sequelae during development and growth: 54 % had some degree of delay in neuropsychomotor development, 27 % obesity. Surgery was performed open in 6 and 12 minimally invasive surgery (MIS).

HISTOPATHOLOGY

2 focal and 16 diffuse, Length of stay (days) was lower in MIS (p < 0.05). Survival was 100 %.

CONCLUSIONS

CHI is a rare and difficult-to-manage tumor that must be performed in a multidisciplinary and tertiary center. Most surgical results are good and the laparoscopic approach to disease has been the best choice for patients.

Molecular imaging of endocrine neoplasms with emphasis on 18F-DOPA PET: a practical approach for well-tailored imaging protocols

6-[18F]-L-fluoro-L-3, 4-dihydroxyphenylalanine (¹⁸F-DOPA) PET/CT can be a useful tool for the detection of different neuroendocrine tumors (NETs). The main determinants of ¹⁸F-DOPA uptake and retention by NETs are related to expression of LAT1/LAT2 transporters, expression and activity of AADC and biochemical phenotype, all being intimately inter-connected to their embryological origin. In order to improve sensitivity of ¹⁸F-DOPA PET, it is of main importance to perform indivisualized imaging protocols across primaries. This review provides a practical approach for performing well-tailored imaging protocols and describes the clinical value of the recommended radiopharmaceuticals.

PET/MRI in Pediatric Neuroimaging: Primer for Clinical Practice

Modern pediatric imaging seeks to provide not only exceptional anatomic detail but also physiologic and metabolic information of the pathology in question with as little radiation penalty as possible. Hybrid PET/MR imaging combines exquisite soft-tissue information obtained by MR imaging with functional information provided by PET, including metabolic markers, receptor binding, perfusion, and neurotransmitter release data. In pediatric neuro-oncology, PET/MR imaging is, in many ways, ideal for follow-up compared with PET/CT, given the superiority of MR imaging in neuroimaging compared with CT and the lower radiation dose, which is relevant in serial imaging and long-term follow-up of pediatric patients. In addition, although MR imaging is the main imaging technique for the evaluation of spinal pathology, PET/MR imaging may provide useful information in several clinical scenarios, including tumor staging and follow-up, treatment response assessment of spinal malignancies, and vertebral osteomyelitis. This review article covers neuropediatric applications of PET/MR imaging in addition to considerations regarding radiopharmaceuticals, imaging protocols, and current challenges to clinical implementation.

Hyperinsulinemic hypoglycemia in adolescents: case report and systematic review

BACKGROUND

Hyperinsulinemic hypoglycemia is the most common cause of severe and persistent hypoglycemia in neonates and children. It is a heterogeneous condition with dysregulated insulin secretion, which persists in the presence of low blood glucose levels.

CASE PRESENTATION

We report a case of a 15 year-old male with hyperinsulinemic hypoglycemia, who underwent a subtotal pancreatectomy after inadequate response to medical therapy. Pathological examination was positive for nesidioblastosis (diffuse β-cell hyperplasia by H-E and immunohistochemical techniques). The patient's blood glucose levels normalized after surgery and he remains asymptomatic after 1 year of follow-up. The systematic review allowed us to identify 41 adolescents from a total of 205 cases reported in 22 manuscripts, from a total of 454 found in the original search done in PubMed and Lilacs.

CONCLUSIONS

Although very well reported in children, hyperinsulinemic hypoglycemia can occur in adolescents or young adults, as it happens in our reported case. These patients can be seen, treated and reported by pediatricians or adult teams either way due to the wide age range used to define adolescence. Most of them do not respond to medical treatment, and subtotal distal pancreatectomy has become the elected procedure with excellent long-term response in the vast majority.

18-F-L 3,4-Dihydroxyphenylalanine PET/Computed Tomography in the Management of Congenital Hyperinsulinism

Congenital hyperinsulinism (HI) is the most common cause of persistent hypoglycemia in neonates and infants. Several genetic mutations have been identified and are associated with 2 distinct histopathologic forms of disease: diffuse and focal. Targeted clinical evaluation to distinguish medically treatable disease from disease requiring surgical management can prevent life-threatening complications. Detection and localization of a surgically curable focal lesion using PET imaging with 18-F-L 3,4-dihydroxyphenylalanine ([18F]-FDOPA) has become standard of care. This article provides guidelines for the selection of patients who can benefit from [18F]-FDOPA-PET/computed tomography and protocols and tips used to diagnose a focal lesion of HI.

Functional characterization of ABCC8 variants of unknown significance based on bioinformatics predictions, splicing assays, and protein analyses: Benefits for the accurate diagnosis of congenital hyperinsulinism

ABCC8 encodes the SUR1 subunit of the β-cell ATP-sensitive potassium channel whose loss of function causes congenital hyperinsulinism (CHI). Molecular diagnosis is critical for optimal management of CHI patients. Unfortunately, assessing the impact of ABCC8 variants on RNA splicing remains very challenging as this gene is poorly expressed in leukocytes. Here, we performed bioinformatics analysis and cell-based minigene assays to assess the impact on splicing of 13 ABCC8 variants identified in 20 CHI patients. Next, channel properties of SUR1 proteins expected to originate from minigene-detected in-frame splicing defects were analyzed after ectopic expression in COSm6 cells. Out of the analyzed variants, seven induced out-of-frame splicing defects and were therefore classified as recessive pathogenic, whereas two led to skipping of in-frame exons. Channel functional analysis of the latter demonstrated their pathogenicity. Interestingly, the common rs757110 SNP increased exon skipping in our system suggesting that it may act as a disease modifier factor. Our strategy allowed determining the pathogenicity of all selected ABCC8 variants, and CHI-inheritance pattern for 16 out of the 20 patients. This study highlights the value of combining RNA and protein functional approaches in variant interpretation and reveals the minigene splicing assay as a new tool for CHI molecular diagnostics.

Visual interpretation, not SUV ratios, is the ideal method to interpret 18F-DOPA PET scans to aid in the cure of patients with focal congenital hyperinsulinism

INTRODUCTION

Congenital hyperinsulinism is characterized by abnormal regulation of insulin secretion from the pancreas causing profound hypoketotic hypoglycemia and is the leading cause of persistent hypoglycemia in infants and children. The main objective of this study is to highlight the different mechanisms to interpret the 18F-DOPA PET scans and how this can influence outcomes.

MATERIALS AND METHODS

After 18F-Fluoro-L-DOPA was injected intravenously into 50 subjects' arm at a dose of 2.96-5.92 MBq/kg, three to four single-bed position PET scans were acquired at 20, 30, 40 and 50-minute post injection. The radiologist interpreted the scans for focal and diffuse hyperinsulinism using a visual interpretation method, as well as determining the Standard Uptake Value ratios with varying cut-offs.

RESULTS

Visual interpretation had the combination of the best sensitivity and positive prediction values.

CONCLUSIONS

In patients with focal disease, SUV ratios are not as accurate in identifying the focal lesion as visual inspection, and cases of focal disease may be missed by those relying on SUV ratios, thereby denying the patients a chance of cure. We recommend treating patients with diazoxide-resistant hyperinsulinism in centers with dedicated multidisciplinary team comprising of at least a pediatric endocrinologist with a special interest in hyperinsulinism, a radiologist experienced in interpretation of 18F-Fluoro-L-DOPA PET/CT scans, a histopathologist with experience in frozen section analysis of the pancreas and a pancreatic surgeon experienced in partial pancreatectomies in patients with hyperinsulinism.

Molecular imaging of β-cells: diabetes and beyond

Since diabetes is becoming a global epidemic, there is a great need to develop early β-cell specific diagnostic techniques for this disorder. There are two types of diabetes (i.e., type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM)). In T1DM, the destruction of pancreatic β-cells leads to reduced insulin production or even absolute insulin deficiency, which consequently results in hyperglycemia. Actually, a central issue in the pathophysiology of all types of diabetes is the relative reduction of β-cell mass (BCM) and/or impairment of the function of individual β-cells. In the past two decades, scientists have been trying to develop imaging techniques for noninvasive measurement of the viability and mass of pancreatic β-cells. Despite intense scientific efforts, only two tracers for positron emission tomography (PET) and one contrast agent for magnetic resonance (MR) imaging are currently under clinical evaluation. β-cell specific imaging probes may also allow us to precisely and specifically visualize transplanted β-cells and to improve transplantation outcomes, as transplantation of pancreatic islets has shown promise in treating T1DM. In addition, some of these probes can be applied to the preoperative detection of hidden insulinomas as well. In the present review, we primarily summarize potential tracers under development for imaging β-cells with a focus on tracers for PET, SPECT, MRI, and optical imaging. We will discuss the advantages and limitations of the various imaging probes and extend an outlook on future developments in the field.

Pancreatic uptake and radiation dosimetry of 6-[18F]fluoro-L-DOPA from PET imaging studies in infants with congenital hyperinsulinism

METHODS

After injecting 25.6 ± 8.8 MBq (0.7 ± 0.2 mCi) of 18F-Fluoro-L-DOPA intravenously, three static PET scans were acquired at 20, 30, and 40 min post injection in 3-D mode on 10 patients (6 male, 4 female) with congenital hyperinsulinism. Regions of interest (ROIs) were drawn over several organs visible in the reconstructed PET/CT images and time activity curves (TACs) were generated. Residence times were calculated using the TAC data. The radiation absorbed dose for the whole body was calculated by entering the residence times in the OLINDA/EXM 1.0 software.

RESULTS

The mean residence times for the 18F-Fluoro-L-DOPA in the liver, lungs, kidneys, muscles, and pancreas were 11.54 ± 2.84, 1.25 ± 0.38, 4.65 ± 0.97, 17.13 ± 2.62, and 0.89 ± 0.34 min, respectively. The mean effective dose equivalent for 18F-Fluoro-L-DOPA was 0.40 ± 0.04 mSv/MBq. The CT scan used for attenuation correction delivered an additional radiation dose of 5.7 mSv. The organs receiving the highest radiation absorbed dose from 18F-Fluoro-L-DOPA were the urinary bladder wall (2.76 ± 0.95 mGy/MBq), pancreas (0.87 ± 0.30 mGy/MBq), liver (0.34 ± 0.07 mGy/MBq), and kidneys (0.61 ± 0.11 mGy/MBq). The renal system was the primary route for the radioactivity clearance and excretion.

CONCLUSIONS

The estimated radiation dose burden from 18F-Fluoro-L-DOPA is relatively modest to newborns.

18F-DOPA PET/CT and 68Ga-DOTANOC PET/CT scans as diagnostic tools in focal congenital hyperinsulinism: a blinded evaluation

Purpose

Focal congenital hyperinsulinism (CHI) is curable by surgery, which is why identification of the focal lesion is crucial. We aimed to determine the use of 18F–fluoro-dihydroxyphenylalanine (18F-DOPA) PET/CT vs. 68Ga-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic-acid-1-Nal3-octreotide (68Ga-DOTANOC) PET/CT as diagnostic tools in focal CHI.

Methods

PET/CT scans of children with CHI admitted to Odense University Hospital between August 2005 and June 2016 were retrospectively evaluated visually and by their maximal standardized uptake values (SUV_max) by two independent examiners, blinded for clinical, surgical and pathological data. Pancreatic histology was used as the gold standard. For patients without surgery, the genetic profile served as the gold standard.

Results

Fifty-five CHI patients were examined by PET/CT (18F-DOPA n = 53, 68Ga-DOTANOC n = 18). Surgery was performed in 34 patients, no surgery in 21 patients. Fifty-one patients had a classifiable outcome, either by histology (n = 33, 22 focal lesions, 11 non-focal) or by genetics (n = 18, all non-focal). The predictive performance of 18F-DOPA PET/CT to identify focal CHI was identical by visual- and cut-off-based evaluation: sensitivity (95% CI) of 1 (0.85–1); specificity of 0.96 (0.82–0.99). The optimal 18F-DOPA PET SUV_max ratio cut-off was 1.44 and the optimal 68Ga-DOTANOC PET SUV_max cut-off was 6.77 g/ml. The area under the receiver operating curve was 0.98 (0.93–1) for 18F-DOPA PET vs. 0.71 (0.43–0.95) for 68Ga-DOTANOC PET (p < 0.03). In patients subjected to surgery, localization of the focal lesion was correct in 91%, and 100%, by 18F-DOPA PET/CT and 68Ga-DOTANOC PET/CT, respectively.

Conclusion

18F-DOPA PET/CT was excellent in predicting focal CHI and superior compared to 68Ga-DOTANOC PET/CT. Further use of 68GA-DOTANOC PET/CT in predicting focal CHI is discouraged.

Electronic supplementary material

The online version of this article (10.1007/s00259-017-3867-1) contains supplementary material, which is available to authorized users.

Role of (18) F-FDOPA PET/CT imaging in endocrinology

(18) F-FDOPA (6-[18F]-L-fluoro-L-3, 4-dihydroxyphenylalanine)-based PET/CT imaging can be a useful tool for the detection of different neuroendocrine tumours (NETs). (18) F-FDOPA is taken up into the cells via the neutral amino acid transporter (LAT1/4F2hc). This transporter is also coupled to the mammalian target of rapamycin (mTOR) signalling pathway. (18) F-FDOPA PET/CT may be performed for confirmation of diagnosis of pheochromocytoma/paraganglioma, staging at initial presentation, restaging and follow-up of patients. In SDHx-related syndromes, (18) F-FDG PET/CT should be performed in addition to (18) F-FDOPA PET/CT. (18) F-FDOPA PET/CT is also invaluable in the detection staging/restaging of carcinoid tumours and has greater sensitivity as compared to somatostatin receptor scintigraphy. (18) F-FDOPA PET/CT can also distinguish between focal vs diffuse CHI. It is not as useful in adult hyperinsulinism due to increased background uptake, but the problem may be overcome with the help of premedication with carbidopa. It has limited use in pancreatic NETs. (18) F-FDOPA PET/CT is a good modality for detection of persistent and residual medullary thyroid cancer (MTC), but (18) F-FDG PET/CT may be needed in aggressive tumours. In summary, F-DOPA PET/CT has widespread utility in the diagnosis of different neuroendocrine tumours.

18F-FDOPA PET/CT imaging of insulinoma revisited

PURPOSE

(18)F-FDOPA PET imaging is increasingly used in the work-up of patients with neuroendocrine tumours. It has been shown to be of limited value in localizing pancreatic insulin-secreting tumours in adults with hyperinsulinaemic hypoglycaemia (HH) mainly due to (18)F-FDOPA uptake by the whole pancreatic gland. The objective of this study was to review our experience with (18)F-FDOPA PET/CT imaging with carbidopa (CD) premedication in patients with HH in comparison with PET/CT studies performed without CD premedication in an independent population.

METHODS

A retrospective study including 16 HH patients who were investigated between January 2011 and December 2013 using (18)F-FDOPA PET/CT (17 examinations) in two academic endocrine tumour centres was conducted. All PET/CT examinations were performed under CD premedication (200 mg orally, 1 - 2 h prior to tracer injection). The PET/CT acquisition protocol included an early acquisition (5 min after (18)F-FDOPA injection) centred over the upper abdomen and a delayed whole-body acquisition starting 20 - 30 min later. An independent series of eight consecutive patients with HH and investigated before 2011 were considered for comparison. All patients had a reference whole-body PET/CT scan performed about 1 h after (18)F-FDOPA injection. In all cases, PET/CT was performed without CD premedication.

RESULTS

In the study group, (18)F-FDOPA PET/CT with CD premedication was positive in 8 out of 11 patients with histologically proven insulinoma (73 %). All (18)F-FDOPA PET/CT-avid insulinomas were detected on early images and 5 of 11 (45 %) on delayed ones. The tumour/normal pancreas uptake ratio was not significantly different between early and delayed acquisitions. Considering all patients with HH, including those without imaging evidence of disease, the detection rate of the primary lesions using CD-assisted (18)F-FDOPA PET/CT was 53 %, showing 9 insulinomas in 17 studies performed. In the control group (without CD premedication, eight patients), the final diagnosis was benign insulinoma in four, nesidioblastosis in one, and no definitive diagnosis in the remainder. (18)F-FDOPA PET/CT failed to detect any tumour in these patients.

CONCLUSION

According to our experience, CD administration before (18)F-FDOPA injection leads to low residual pancreatic (18)F-FDOPA activity preserving tumoral uptake with consequent insulinoma detection in more than half of adult patients with HH and more than 70 % of patients with a final diagnosis of insulinoma. If (18)F-FDOPA PET/CT is indicated, we strongly recommend combining CD premedication with early acquisition centred over the pancreas.

Focal congenital hyperinsulinism managed by medical treatment: a diagnostic algorithm based on molecular genetic screening

OBJECTIVE

Congenital hyperinsulinism (CHI) requires rapid diagnosis and treatment to avoid irreversible neurological sequelae due to hypoglycaemia. Aetiological diagnosis is instrumental in directing the appropriate therapy. Current diagnostic algorithms provide a complete set of diagnostic tools including (i) biochemical assays, (ii) genetic facility and (iii) state-of-the-art imaging. They consider the response to a therapeutic diazoxide trial an early, crucial step before proceeding (or not) to specific genetic testing and eventually imaging, aimed at distinguishing diffuse vs focal CHI. However, interpretation of the diazoxide test is not trivial and can vary between research groups, which may lead to inappropriate decisions. Objective of this report is proposing a new algorithm in which early genetic screening, rather than diazoxide trial, dictates subsequent clinical decisions.

PATIENTS, METHODS AND RESULTS

Two CHI patients weaned from parenteral glucose infusion and glucagon after starting diazoxide. No hypoglycaemia was registered during a 72-h continuous glucose monitoring (CGMS), or hypoglycaemic episodes were present for no longer than 3% of 72-h. Normoglycaemia was obtained by low-medium dose diazoxide combined with frequent carbohydrate feeds for several years. We identified monoallelic, paternally inherited mutations in KATP channel genes, and (18) F-DOPA PET-CT revealed a focal lesion that was surgically resected, resulting in complete remission of hypoglycaemia.

CONCLUSIONS

Although rare, some patients with focal lesions may be responsive to diazoxide. As a consequence, we propose an algorithm that is not based on a 'formal' diazoxide response but on genetic testing, in which patients carrying paternally inherited ABCC8 or KCNJ11 mutations should always be subjected to (18) F-DOPA PET-CT.

Congenital hyperinsulinism

Hyperinsulinism is the most common cause of hypoglycemia in infants. In many cases conservative treatment is not effective and surgical intervention is required. Differentiation between diffuse and focal forms and localization of focal lesions are the most important issues in preoperative management. We present a case of persistent infancy hyperinsulinism. Clinical presentation, conservative treatment modalities, diagnostic possibilities of focal and diffuse forms, and surgical treatment, which led to total recovery, are discussed.

Strengths and limitations of using 18fluorine-fluorodihydroxyphenylalanine PET/CT for congenital hyperinsulinism

¹⁸fluorine-fluorodihydroxyphenylalanine (FDOPA) PET/CT is currently the first-line imaging technique to distinguish between focal and diffuse forms of congenital hyperinsulinism (CHI) and to accurately localize focal forms. However, this technique has a number of limitations, mainly the very small size of focal forms or inversely a very large focal form mimicking a diffuse form, and misinterpretation of physiologic uptake masking hot spots or inversely mimicking focal forms. The other limitation is the limited availability of the radiopharmaceutical. FDOPA PET/CT has no recognized competitor to date among the available morphologic and functional imaging techniques. Other potential approaches using specific tracers for positron emission tomography (PET) are discussed, using radiopharmaceuticals specific for β cell mass or targeting somatostatin receptors. These radiopharmaceuticals can be labeled with gallium-68, a PET emitter readily available in PET centers equipped with 68Ge/68Ga generators.

Congenital hyperinsulinism: Role of fluorine-18L-3, 4 hydroxyphenylalanine positron emission tomography scanning

Congenital hyperinsulinism (CHI) is a rare but complex heterogeneous disorder caused by unregulated secretion of insulin from the β-cells of the pancreas leading to severe hypoglycaemia and neuroglycopaenia. Swift diagnosis and institution of appropriate management is crucial to prevent or minimise adverse neurodevelopmental outcome in children with CHI. Histologically there are two major subtypes of CHI, diffuse and focal disease and the management approach will significantly differ depending on the type of the lesion. Patients with medically unresponsive diffuse disease require a near total pancreatectomy, which then leads on to the development of iatrogenic diabetes mellitus and pancreatic exocrine insufficiency. However patients with focal disease only require a limited pancreatectomy to remove only the focal lesion thus providing complete cure to the patient. Hence the preoperative differentiation of the histological subtypes of CHI becomes paramount in the management of CHI. Fluorine-18L-3, 4-hydroxyphenylalanine positron emission tomography (¹⁸F-DOPA-PET) is now the gold standard for pre-operative differentiation of focal from diffuse disease and localisation of the focal lesion. The aim of this review article is to give a clinical overview of CHI, then review the role of dopamine in β-cell physiology and finally discuss the role of ¹⁸F-DOPA-PET imaging in the management of CHI.

The value of radiologic interventions and (18)F-DOPA PET in diagnosing and localizing focal congenital hyperinsulinism: systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis aimed to quantify the diagnostic performance of pancreatic venous sampling (PVS), selective pancreatic arterial calcium stimulation with hepatic venous sampling (ASVS), and (18)F-DOPA positron emission tomography (PET) in diagnosing and localizing focal congenital hyperinsulinism (CHI).

PROCEDURES

This systematic review and meta-analysis was conducted according to the PRISMA statement. PubMed, EMBASE, SCOPUS and Web of Science electronic databases were systematically searched from their inception to November 1, 2011. Using predefined inclusion and exclusion criteria, two blinded reviewers selected articles. Critical appraisal ranked the retrieved articles according to relevance and validity by means of the QUADAS-2 criteria. Pooled data of homogeneous study results estimated the sensitivity, specificity, likelihood ratios and diagnostic odds ratio (DOR).

RESULTS

(18)F-DOPA PET was superior in distinguishing focal from diffuse CHI (summary DOR, 73.2) compared to PVS (summary DOR, 23.5) and ASVS (summary DOR, 4.3). Furthermore, it localized focal CHI in the pancreas more accurately than PVS and ASVS (pooled accuracy, 0.82 vs. 0.76, and 0.64, respectively). Important limitations comprised the inclusion of studies with small sample sizes, high probability of bias and heterogeneity among their results. Studies with small sample sizes and high probability of bias tended to overestimate the diagnostic accuracy.

CONCLUSIONS

This systematic review and meta-analysis found evidence for the superiority of (18)F-DOPA PET in diagnosing and localizing focal CHI in patients requiring surgery for this disease.

Diagnostic role of 18F-dihydroxyphenylalanine positron emission tomography in patients with congenital hyperinsulinism: a meta-analysis

OBJECTIVES

Studies have reported the applications of F-dihydroxyphenylalanine (F-DOPA) PET in patients with congenital hyperinsulinism (CHI). The aim of this study was to systematically review and perform a meta-analysis of published data on the diagnostic role of F-DOPA PET in patients with CHI.

MATERIALS AND METHODS

A comprehensive computer literature search of studies on F-DOPA PET or PET/computed tomography (CT) in patients with CHI was conducted. The pooled sensitivity and specificity of F-DOPA PET or PET/CT in patients with CHI were calculated. The area under the receiver-operating characteristic curve was calculated to measure the accuracy of F-DOPA PET or PET/CT in patients with CHI.

RESULTS

Ten studies comprising 181 patients with CHI were included in this meta-analysis. The pooled sensitivity of F-DOPA PET and PET/CT in detecting CHI was 88% on a per-patient-based analysis. The pooled specificity of F-DOPA PET and PET/CT in demonstrating CHI was 79%. The area under the receiver-operating characteristic curve was 0.92 on a per-patient-based analysis.

CONCLUSION

In patients with CHI, F-DOPA PET or PET/CT demonstrated high sensitivity and specificity. F-DOPA PET and PET/CT are accurate methods for the diagnosis of CHI. Nevertheless, possible sources of false-positive and false-negative results should be kept in mind.

Integrating genetic and imaging investigations into the clinical management of congenital hyperinsulinism

Congenital Hyperinsulinism (CHI) is a rare but important cause of hypoglycaemia in infancy. CHI is a heterogeneous disease, but has a strong genetic basis; a number of genetic causes have been identified with CHI in about a third of individuals, chiefly in the genes that code for the ATP sensitive K(+) channels (KATP ) in the pancreatic β-cells. Rapid KATP channel gene testing is a critical early step in the diagnostic algorithm of CHI, with paternal heterozygosity correlating with the occurrence of focal lesions. Imaging investigations to diagnose and localize solitary pancreatic foci have evolved over the last decade with (18)F-DOPA PET-CT scanning as the current diagnostic tool of choice. Although clinical management of CHI has improved significantly with the application of genetic screening and imaging investigations, much remains to be uncovered. This includes a better understanding of the molecular mechanisms for dysregulated insulin release in those patients without known genetic mutations, and the development of biomarkers that could characterize CHI, including long-term prognosis and targeted treatment planning, i.e. 'personalised medicine'. From the perspective of pancreatic imaging, it would be important to achieve greater specificity of diagnosis not only for focal lesions but also for diffuse and atypical forms of the disease.

18F-fluorodihydroxyphenylalanine vs other radiopharmaceuticals for imaging neuroendocrine tumours according to their type

6-Fluoro-(¹⁸F)-L-3,4-dihydroxyphenylalanine (FDOPA) is an amino acid analogue for positron emission tomography (PET) imaging which has been registered since 2006 in several European Union (EU) countries and by several pharmaceutical firms. Neuroendocrine tumour (NET) imaging is part of its registered indications. NET functional imaging is a very competitive niche, competitors of FDOPA being two well-established radiopharmaceuticals for scintigraphy, ¹²³I-metaiodobenzylguanidine (MIBG) and ¹¹¹In-pentetreotide, and even more radiopharmaceuticals for PET, including fluorodeoxyglucose (FDG) and somatostatin analogues. Nevertheless, there is no universal single photon emission computed tomography (SPECT) or PET tracer for NET imaging, at least for the moment. FDOPA, as the other PET tracers, is superior in diagnostic performance in a limited number of precise NET types which are currently medullary thyroid cancer, catecholamine-producing tumours with a low aggressiveness and well-differentiated carcinoid tumours of the midgut, and in cases of congenital hyperinsulinism. This article reports on diagnostic performance and impact on management of FDOPA according to the NET type, emphasising the results of comparative studies with other radiopharmaceuticals. By pooling the results of the published studies with a defined standard of truth, patient-based sensitivity to detect recurrent medullary thyroid cancer was 70 % [95 % confidence interval (CI) 62.1–77.6] for FDOPA vs 44 % (95 % CI 35–53.4) for FDG; patient-based sensitivity to detect phaeochromocytoma/paraganglioma was 94 % (95 % CI 91.4–97.1) for FDOPA vs 69 % (95 % CI 60.2–77.1) for ¹²³I-MIBG; and patient-based sensitivity to detect midgut NET was 89 % (95 % CI 80.3–95.3) for FDOPA vs 80 % (95 % CI 69.2–88.4) for somatostatin receptor scintigraphy with a larger gap in lesion-based sensitivity (97 vs 49 %). Previously unpublished FDOPA results from our team are reported in some rare NET, such as small cell prostate cancer, or in emerging indications, such as metastatic NET of unknown primary (CUP-NET) or adrenocorticotropic hormone (ACTH) ectopic production. An evidence-based strategy in NET functional imaging is as yet affected by a low number of comparative studies. Then the suggested diagnostic trees, being a consequence of the analysis of present data, could be modified, for some indications, by a wider experience mainly involving face-to-face studies comparing FDOPA and ⁶⁸Ga-labelled peptides.

Accuracy of PET/CT Scan in the diagnosis of the focal form of congenital hyperinsulinism

PURPOSE

The purpose of the study was to determine the sensitivity of the (18)fluoro-dihydroxyphenylalanine positron emission tomography/computed tomography scan (18F-PET/CT) in the diagnosis of focal congenital hyperinsulinism (HI).

METHODS

A retrospective review of children with HI who underwent a preoperative 18F-PET/CT scan was performed.

RESULTS

Between 1/2008 and 2/2012 we performed 105 consecutive 18F-PET/CT scans on infants with HI. Fifty-three patients had focal HI. Of those fifty-three patients, eight had a preoperative 18F-PET/CT scan read as "diffuse disease". The sensitivity of the study in the diagnosis of focal HI was 85%. The location of the eight missed focal lesions was: head (3), body (2), and tail (3). The 18F-PET/CT of the missed head lesions showed homogeneous tracer uptake (n =2) or heterogeneous uptake throughout the pancreas (n=1). The 18F-PET/CT of the 2 missed body lesions and 1 missed tail lesion showed heterogeneous uptake throughout the pancreas. The 18F-PET/CT of the other 2 missed tail lesions showed lesions adjacent to and obscured by the signal of the upper renal pole, identified retrospectively by closer observation. Fifty-two of the 105 patients had diffuse HI. Two of them had 18F-PET/CT studies read as "focal disease". Therefore, the specificity of the study was 96%. Of the forty-seven 18F-PET/CT studies read as "focal disease", forty-five had true focal HI. Therefore, the positive predictive value of the study in the diagnosis of focal HI was 96%.

CONCLUSION

The sensitivity and specificity of 18 F-PET/CT can be affected by certain anatomic features of the pancreas, by the location of the lesion, and by the reader's experience.

Diagnostic performance of fluorine-18-dihydroxyphenylalanine positron emission tomography in diagnosing and localizing the focal form of congenital hyperinsulinism: a meta-analysis

INTRODUCTION

We performed a meta-analysis on published data on the diagnostic performance of fluorine-18 dihydroxyphenylalanine ((18)F-DOPA) positron emission tomography (PET) in diagnosing and localizing focal congenital hyperinsulinism (CHI).

MATERIALS AND METHODS

A comprehensive computer literature search of studies published up to 31 January 2012 regarding (18)F-DOPA PET or PET/CT in patients with CHI was performed. Pooled sensitivity and specificity, area under the ROC curve and diagnostic odds ratio (DOR) of (18)F-DOPA PET or PET/CT in diagnosing focal CHI were calculated. The localization accuracy of focal CHI was also estimated. Seven studies comprising 195 CHI patients were included.

RESULTS

The pooled sensitivity and specificity of (18)F-DOPA PET or PET/CT in differentiating between focal and diffuse CHI were 89% (95% confidence interval [CI]:81-95%) and 98% (95% CI:89-100%), respectively. The DOR was 74.5 (95% CI:18-307). The area under the ROC curve was 0.95. The pooled accuracy of these functional imaging methods in localizing focal CHI was 80% (95% CI:71-88%).

DISCUSSION

In CHI patients, (18)F-DOPA PET or PET/CT demonstrated high sensitivity and specificity in differentiating between focal and diffuse CHI. (18)F-DOPA PET or PET/CT are accurate methods of localizing focal CHI. Nevertheless, possible sources of false-negative results for focal CHI should be kept in mind.

PET/CT in Neuroendocrine Tumors: Evaluation of Receptor Status and Metabolism

In-111 Octreoscan is considered the gold standard for imaging of neuroendocrine tumors (NET). However, in the absence of morphologic imaging correlation, the exact localisation of the tumor is often difficult. Also the sensitivity of PET imaging is more than Gamma camera (SPECT) imaging. Ga-68 labelled somatostatin analogs (SMS-R) are interesting radiopharmaceuticals for PET receptor imaging of NET. Some other radiopharmaceuticals e.g. F-18 DOPA can also be used to assess metabolism and functional status of NET. The importance of these radiopharmaceuticals, especially SMS-R increases in the absence of any specific biochemical marker or clinical parameter for follow-up of patients after therapy (eg peptide receptor radionuclide therapy, surgery, chemoembolisation, etc). New criteria based on molecular, metabolic and morphologic imaging needs to be developed for correct assessment of response to therapy for these slow-growing, solid tumors.

Diagnostic accuracy of [¹⁸F]-fluoro-L-dihydroxyphenylalanine positron emission tomography scan for persistent congenital hyperinsulinism in Japan

OBJECTIVE

We aimed to elucidate the accuracy and limitations of [(18)F]-fluoro-L-dihydroxyphenylalanine ([(18) F]DOPA) positron emission tomography (PET) for Japanese patients with congenital hyperinsulinism. Although [(18)F]DOPA PET is reported to be useful for precisely localizing the focal form of congenital hyperinsulinism, previous reports are mostly from European and North American centres.

PATIENTS

Seventeen Japanese infants with congenital hyperinsulinism.

MEASUREMENTS

[(18)F]DOPA PET studies were carried out, and the results were assessed by simple inspection or by a quantitative measurement termed the 'Pancreas Percentage', which expresses the uptake of the head, body or tail of the pancreas as a percentage of the total maximum standardized uptake value of the whole pancreas. The results were compared with those of other studies, including genetic analysis and histology.

RESULTS

By simple inspection, when a single focal uptake was obtained, the localization and histology were correct in all cases that underwent pancreatectomy. However, the overall results were consistent with the molecular diagnosis and histology in only 7/17 and 6/12 patients, respectively. The inaccuracy of PET studies by inspection was because of elevated background uptake that mimicked a diffuse or multifocal appearance. The accuracy improved substantially using the Pancreas Percentage; it was consistent with the molecular diagnosis and histology in 10/17 and 9/12 patients, respectively.

CONCLUSIONS

In contrast to the results of previous reports, [(18)F]DOPA PET appears to be less efficient for diagnosing Japanese patients with congenital hyperinsulinism. However, the diagnostic accuracy is substantially improved when this technique is combined with the Pancreas Percentage.

Tailored imaging of islet cell tumors of the pancreas amidst increasing options

Pancreatic islet cell tumors are neuroendocrine tumors, which can produce hormones and can arise as part of multiple endocrine neoplasia type 1 or von-Hippel-Lindau-disease, two genetically well-defined hereditary cancer syndromes. Currently, technical innovation improves conventional and specific molecular imaging techniques. To organize the heterogeneous results described for the imaging of these tumors, we distinguished three indications (1) imaging of a patient with hormone hypersecretion, (2) search for a pancreatic primary in case of proven neuroendocrine cancer of unknown primary, and (3) screening of asymptomatic mutation carriers. We searched for publications on imaging of islet cell tumors between 1995 and January 2010 and defined a Level of Evidence (LOE) for the applicability of each technique. For each technique, data were analyzed in a Forest plot and arranged per imaging indication and tumor subtype. LOEs are weak for all imaging techniques. Analyses indicate a prominent role for endoscopic ultrasound for all three indications.

Role of 18F-DOPA PET/CT imaging in congenital hyperinsulinism

Congenital hyperinsulinism is a leading cause of severe hypoglycaemia in the newborn period. There are two (diffuse and focal) histological subtypes of congenital hyperinsulinism. The diffuse form affects the entire pancreas and if medically unresponsive will require a near total (95%-98%) pancreatectomy. The focal form affects only a small region of the pancreas (with the rest of the pancreas being normal in endocrine and exocrine function) and only requires a limited pancreatectomy. This limited section of the focal lesion has the potential for curing the patient. Thus the pre-operative differentiation of these two subgroups is extremely important. Recent advances in Fluorine-18-L-dihydroxyphenylalanine positron emission tomography ((18)F-DOPA PET/CT) have radically changed the clinical approach to patient with congenital hyperinsulinism. In most patients this novel imaging technique is able to offer precise pre-operative localisation of the focal lesion, thus guiding the extent of surgical resection.

Radionuclide probes for molecular imaging of pancreatic beta-cells

Islet transplantation is a promising treatment option for patients with type 1 diabetes (T1D); however, the fate of the graft over time remains difficult to follow, due to the lack of available tools capable of monitoring graft rejection and inflammation prior to islet graft loss. Due to the challenges imposed by the location of the pancreas and the sparsely dispersed beta-cell population within the pancreas, currently, the clinical verification of beta-cell abnormalities can only be obtained indirectly via metabolic studies, which typically is not possible until after a significant deterioration in islet function has already occurred. The development of non-invasive imaging methods for the assessment of the pancreatic beta-cells, however, offers the potential for the early detection of beta-cell dysfunction prior to the clinical onset of T1D and type 2 diabetes (T2D). Ideal islet imaging agents would have an acceptable residence time in the human body, be capable of providing high-resolution images with minimal uptake in surrounding tissues (e.g., the liver), would not be toxic to islets, and would not require pre-treatment of islets prior to transplantation. A variety of currently available imaging techniques, including magnetic resonance imaging (MRI), bioluminescence imaging (BLI), and nuclear imaging have been tested for the study of beta-cell diseases. In this article, we summarize the recent advances made in nuclear imaging techniques for non-invasive imaging of pancreatic beta-cells. The use of radioactive probes for islet imaging is also discussed.

Value of combined 6-[18F]fluorodihydroxyphenylalanine PET/CT for imaging of neuroendocrine tumours

BACKGROUND

Accurate knowledge of tumour presence and location is essential to treat neuroendocrine tumours (NETs). Standard imaging has been hampered by low sensitivity and lack of spatial resolution. This study assessed prospectively the diagnostic value and impact of combined 6-[18F]fluorodihydroxyphenylalanine positron emission tomography-computed tomography (18F-DOPA-PET/CT) in the management of NET.

METHODS

18F-DOPA-PET/CT findings in 61 patients with suspected NET were compared with a composite reference standard including somatostatin receptor scintigraphy (SRS), magnetic resonance imaging, computed tomography, histological examination and clinical follow-up. The impact on clinical management was estimated by calculating the proportion of patients whose treatment changed as a result of 18F-DOPA-PET/CT findings.

RESULTS

18F-DOPA-PET/CT correctly identified 32 of 36 patients with NET. The sensitivity and specificity of 18F-DOPA-PET/CT for the detection of NET were 91 and 96 per cent respectively. Sensitivity using SRS was significantly lower (59 per cent), whereas the specificity was similar (86 per cent). In 16 (26 per cent) of the 61 patients the management was altered as a result of new findings on 18F-DOPA-PET/CT.

CONCLUSION

18F-DOPA-PET/CT yields a high sensitivity and specificity in the detection of NET. The clinical impact was highly relevant as changes in therapy were observed in more than a quarter of the patients.

Fluorine-18 DOPA-PET and PET/CT Imaging in Congenital Hyperinsulinism

Congenital hyperinsulinism is the principle cause of hypoglycemia during infancy but successful treatment is difficult and persistent hypoglycemia carries the risk of neurologic damage. Focal and diffuse abnormalities are the common forms of hyperinsulinism. Identification and localization of focal hyperinsulinism can be cured by partial pancreatectomy. It has been shown that affected pancreatic areas utilize LDOPA in a higher rate than normal pancreatic tissue and, thus, labeling L-DOPA with fluorine-18 (FDOPA) allows functional mapping of hyperinsulinism using PET. This article presents a fundamental overview of the genetics background, pathology, management, and the role of FDOPA-PET imaging in hyperinsulinism.

PET/CT in Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are a rare group of neoplasms that originate from pluripotent stem cells or differentiated neuroendocrine cells, mostly localized in the bronchus, lungs, or gastroenteropancreatic tract. This issue reviews the results achieved with PET. The potential applications of the most commonly used receptor or metabolic positron-emitter radiopharmaceuticals in the field of NET to stage or restage disease, to detect unknown primary tumor, and to assess and monitor therapy response to different kind of treatments are analyzed.

Evaluation of [18F]fluoro-L-DOPA positron emission tomography-computed tomography for surgery in focal congenital hyperinsulinism

CONTEXT

In congenital hyperinsulinism (CHI), the identification and precise localization of a focal lesion is essential for successful surgery.

OBJECTIVE

Our objective was to evaluate the predictive value and accuracy of integrated [18F]fluoro-L-DOPA ([18F]FDOPA) positron emission tomography (PET)-computed tomography (CT) for the surgical therapy of CHI.

DESIGN

This was an observational study.

SETTING

The study was performed in the Department of Pediatric Surgery at a university hospital.

PATIENTS

From February 2005 to September 2007, 10 children with the clinical signs of CHI and an increased radiotracer uptake in a circumscribed area of the pancreas in the [18F]FDOPA PET-CT were evaluated.

INTERVENTIONS

Guided by the [18F]FDOPA PET-CT report, all children underwent partial pancreatic resection, in two cases twice.

MAIN OUTCOME MEASURES

Correlation of the anatomical findings at surgery with the report of the [18F]FDOPA PET-CT, and the results of surgery and clinical outcome were determined.

RESULTS

In nine children the intraoperative situation corresponded exactly to the description of the [18F]FDOPA PET-CT. A limited resection of the pancreas was curative in eight cases at the first surgery, in one case at the second intervention. We observed no diabetes mellitus or exocrine insufficiency in the follow up so far. In one child, hypoglycemia persisted even after two partial resections of the pancreatic head. Histological analysis finally revealed an atypical intermediate form of CHI.

CONCLUSIONS

The integrated [18F]FDOPA PET-CT is accurate to localize the lesion in focal CHI and is a valuable tool to guide the surgeon in limited pancreatic resection.