Proposal for a standardized protocol for 18F-DOPA-PET (PET/CT) in congenital hyperinsulinism

Comparison of organ and effective dose estimations from different Monte Carlo simulation-based software methods in infant CT and comparison with direct phantom measurements

Purpose

Computational dosimetry software is routinely used to evaluate the organ and effective doses from computed tomography (CT) examinations. Studies have shown a significant variation in dose estimates between software in adult cohorts, and few studies have evaluated software for pediatric dose estimates. This study aims to compare the primary organ and effective doses estimated by four commercially available CT dosimetry software to thermoluminescent dosimeter (TLD) measurements in a 1‐year‐old phantom.

Methods

One hundred fifteen calibrated LiF (Mg, Cu, P)‐TLD 100‐H chips were embedded within an anthropomorphic phantom representing a 1‐year‐old child at positions that matched the approximate location of organs within an infant. The phantom was scanned under three protocols, each with whole‐body coverage. The mean absorbed doses from 25 radiosensitive organs and skeletal tissues were determined from the TLD readings. Effective doses for each of the protocols were subsequently calculated using ICRP 103 formalism. Dose estimates by the four Monte Carlo–based dose calculation systems were determined and compared to the directly measured doses.

Results

Most organ doses determined by computation dosimetry software aligned to phantom measurements within 20%. Additionally, comparisons between effective doses are calculated using computational and direct measurement methods aligned within 20% across the three protocols. Significant variances were found in bone surface dose estimations among dosimetry methods, likely caused by differences in bone tissue modeling.

Conclusion

All four‐dosimetry software evaluated in this study provide adequate primary organ and effective dose estimations. Users should be aware, however, of the possible estimated uncertainty associated with each of the programs.

18F-6-Fluoro-l-Dopa PET/CT Imaging of Congenital Hyperinsulinism

Congenital hyperinsulinism is characterized by persistent hypoglycemia due to inappropriate excess secretion of insulin resulting in hyperinsulinemic hypoglycemia. The clinical course varies from mild to severe, with a significant risk for brain damage. Imaging plays a valuable role in the care of infants and children with severe hypoglycemia unresponsive to medical therapy. 18F-6-fluoro-l-dopa PET/CT is the method of choice for the detection and localization of a focal lesion of hyperinsulinism. Surgical resection of a focal lesion can lead to a cure with limited pancreatectomy. This article reviews the role of 18F-6-fluoro-l-dopa PET/CT in the management of this vulnerable population.

Persistent Hypoglycemia in Seven-year-old Saudi Child: A Case Report

Hypoglycemia is a frequent problem in infants and children, causing a significant dilemma to reach the correct diagnosis and perform the appropriate management. Congenital hyperinsulinism is the most common cause of hypoglycemic hyperinsulinemia in infants and is due to beta-cell hyperplasia caused by genetic defects. This is a well-known genetically and clinically heterogeneous condition causing severe hypoglycemia in infants. Insulin-secreting tumors (insulinoma) are rare findings during childhood. In contrast, insulinoma is the most common form of endogenous hypoglycemic hyperinsulinemia in the adult population. Here we present a successful diagnosis and treatment of a nine-year-old Saudi child who presented for the first time with severe episodes of hypoglycemia at age seven. Critical samples at the time of hypoglycemia confirmed the associated hyperinsulinemia state. Initially, the child responded well to anti-insulin medications at small doses, but with time the disease became progressive in severity requiring a high dose of anti-insulin medications, frequent glucagon injections, and hospital admission for intravenous dextrose infusion. After two years of seeking therapy in many hospitals, the final diagnosis was confirmed to be an insulinoma, which was removed surgically, resulting in a complete cure and full recovery. Here we report the first published case of insulinoma in a young child aged < 15 years old in Saudi Arabia, their disease course, final diagnostic steps, and curative therapy. We conclude that hypoglycemia in children is challenging in terms of diagnosis and management. Although insulinoma is very rare in children, it requires significant time and effort by a pediatrician, pediatric endocrinologist, patients, and parents to reach the final diagnosis and carefully preserve the integrity of the neurological state of those children.

Congenital hyperinsulinism: diagnostic and management challenges in a developing country - case report

Management of congenital hyperinsulinemia of infancy (CHI) is challenging. A 4-month-old female infant with persistent hypoglycemia and elevated insulin levels was diagnosed with CHI. Gallium-68 DOTANOC positron emission tomography/computed tomography (PET/CT) scan (⁶⁸Ga-labeled [1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid]-1-NaI3-octreotide) demonstrated focal disease in the body of the pancreas. Genetic studies indicated paternal inheritance, making focal disease likely. She was started on diazoxide therapy with partial improvement in blood glucose levels. Due to a suboptimal response to diazoxide and the likelihood of focal disease amenable to surgery, a laparoscopic subtotal pancreatectomy with preservation of the head of the pancreas was performed. The biopsy demonstrated diffuse hyperplastic pancreatic islet cells on immunohistochemistry, indicative of diffuse rather than focal disease. Paternal inheritance is a recognized indicator of focal disease. Gallium-68 DOTANOC PET/CT scan is the only available imaging modality in South India as ¹⁸F-L-dihydroxyphenylalanine (DOPA) PET/CT scan is not available at present. A laparoscopic approach reduces the postoperative recovery time and morbidity in such patients. The absence of ¹⁸F-L-DOPA PET/CT scan and the limited supply of diazoxide makes the management of this complex condition more challenging in developing countries.

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.

Clinical practice guidelines for congenital hyperinsulinism

Congenital hyperinsulinism is a rare condition, and following recent advances in diagnosis and treatment, it was considered necessary to formulate evidence-based clinical practice guidelines reflecting the most recent progress, to guide the practice of neonatologists, pediatric endocrinologists, general pediatricians, and pediatric surgeons. These guidelines cover a range of aspects, including general features of congenital hyperinsulinism, diagnostic criteria and tools for diagnosis, first- and second-line medical treatment, criteria for and details of surgical treatment, and future perspectives. These guidelines were generated as a collaborative effort between The Japanese Society for Pediatric Endocrinology and The Japanese Society of Pediatric Surgeons, and followed the official procedures of guideline generation to identify important clinical questions, perform a systematic literature review (April 2016), assess the evidence level of each paper, formulate the guidelines, and obtain public comments.

PET/CT in paediatric malignancies - An update

¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a well-established imaging modality in adult oncological practice. Its role in childhood malignancies needs to be discussed as paediatric malignancies differ from adults in tumor subtypes and they have different tumor biology and FDG uptake patterns. This is also compounded by smaller body mass, dosimetric restrictions, and physiological factors that can affect the FDG uptake. It calls for careful planning of the PET study, preparing the child, the parents, and expertise of nuclear physicians in reporting pediatric positron emission tomography/computed tomography (PET/CT) studies. In a broad perspective, FDG-PET/CT has been used in staging, assessment of therapy response, identifying metastases and as a follow-up tool in a wide variety of pediatric malignancies. This review outlines the role of PET/CT in childhood malignancies other than hematological malignancies such as lymphoma and leukemia.

Hyperinsulinemic Hypoglycemia in Infancy: Current Concepts in Diagnosis and Management

PURPOSE

Molecular basis of various forms of hyperinsulinemic hypoglycemia, involving defects in key genes regulating insulin secretion, are being increasingly reported. However, the management of medically unresponsive hyperinsulinism still remains a challenge as current facilities for genetic diagnosis and appropriate imaging are limited only to very few centers in the world. We aim to provide an overview of spectrum of clinical presentation, diagnosis and management of hyperinsulinism.

METHODS

We searched the Cochrane library, MEDLINE and EMBASE databases, and reference lists of identified studies.

CONCLUSION

Analysis of blood samples, collected at the time of hypoglycemic episodes, for intermediary metabolites and hormones is critical for diagnosis and treatment. Increased awareness among clinicians about infants at-risk of hypoglycemia, and recent advances in genetic diagnosis have made remarkable contribution to the diagnosis and management of hyperinsulinism. Newer drugs like lanreotide a long acting somatostatin analogue and sirolimus (mammalian target of rapamycin (mTOR) inhibitor) appears promising as patients with diffuse disease can be treated successfully without subtotal pancreatectomy, minimizing the long-term sequelae of diabetes and pancreatic insufficiency. Newer insights in understanding the molecular and histological basis and improvements in imaging and surgical techniques will modify the approach to patients with congenital hyperinsulinism.

Clinical and genetic evaluation of patients with KATP channel mutations from the German registry for congenital hyperinsulinism

Congenital hyperinsulinism (CHI) causes hypoglycemia due to irregular insulin secretion. In infants, a rapid diagnosis and appropriate management to avoid severe hypoglycemia is mandatory. CHI is a heterogeneous condition at the clinical and genetic level, and disease-causing genes have been identified in about half of the patients. The majority of mutations have been identified in the ABCC8 and KCNJ11 genes encoding subunits of the KATP channel responsible for two distinct histological forms. The diffuse form is caused by autosomal recessive or dominant inherited mutations, whereas the focal form is caused by a paternally transmitted recessive mutation and a second somatic event. We report on an unselected cohort of 136 unrelated patients from the German CHI registry. Mutations in either the ABCC8 or KCNJ11 gene were identified in 61 of these patients (45%). In total, 64 different mutations including 38 novel ones were detected in this cohort. We observed biparental (recessive) inheritance in 34% of mutation-positive patients, dominant inheritance in 11% and paternal transmission of a mutation associated with a focal CHI type in 38%. In addition, we observed inheritance patterns that do not exactly follow the classical recessive or dominant mode, further adding to the genetic complexity of this disease.

Occurrence of giant focal forms of congenital hyperinsulinism with incorrect visualization by (18) F DOPA-PET/CT scanning

CONTEXT

Congenital hyperinsulinism (CHI) is a rare disease characterized by severe hypoglycaemic episodes due to pathologically increased insulin secretion from the pancreatic beta cells. When untreated, CHI might result in irreversible brain damage and death. Currently, two major subtypes of CHI are known: a focal form, associated with local distribution of affected beta cells and a nonfocal form, affecting every single beta cell. The identification of focal forms is important, as the patients can be cured by limited surgery. (18) F DOPA-PET/CT is an established non-invasive approach to differentiate focal from nonfocal CHI.

OBJECTIVE

The purpose of this study was to identify possible limitations of (18) F DOPA-PET/CT scan in patients with focal forms nonfocal CHI.

DESIGN

A retrospective chart review of 32 patients (from 2008 through 2013) who underwent (18) F DOPA-PET/CT and partial pancreatectomy for focal CHI at the reference centres in Berlin, Germany and London, UK.

RESULTS

In most cases (n = 29, 90·7%), (18) F DOPA-PET/CT was sufficient to localize the complete focal lesion. However, in some patients (n = 3, 9·3%), (18) F DOPA-PET/CT wrongly visualized only a small portion of the focal lesion. In this group of patients, a so-called 'giant focus' was detected in histopathological analysis during the surgery.

CONCLUSIONS

Our data show that in most patients with focal CHI (18) F DOPA-PET/CT correctly predicts the size and anatomical localisation of the lesion. However, in those patients with a 'giant focal' lesion (18) F DOPA-PET/CT is unreliable for correct identification of 'giant focus' cases.

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.

Normal biodistribution pattern and physiologic variants of 18F-DOPA PET imaging

Dihydroxyphenylalanine (DOPA) is a neutral amino acid that resembles natural l-dopa (dopamine precursor). It enters the catecholamine metabolic pathway of endogenous l-DOPA in the brain and peripheral tissues. It is amenable to labeling with fluorine-18 (¹⁸F) for PET imaging and was originally used in patients with Parkinson’s disease to assess the integrity of the striatal dopaminergic system. The recent introduction and use of hybrid PET/CT scanners has contributed significantly to the management of a series of other pathologies including neuroendocrine tumors, brain tumors, and pancreatic cell hyperplasia. These pathologic entities present an increased activity of l-DOPA decarboxylase and therefore demonstrate high uptake of ¹⁸F-DOPA. Despite these potentially promising applications in several clinical fields, the role of ¹⁸F-DOPA has not been elucidated completely yet because of associated difficulties in synthesis and availability. Unfortunately, the available literature does not provide recommendations for procedures or administered activity, acquisition timing, and premedication with carbidopa. The aim of this paper is to outline the physiological biodistribution and normal variants, including possible pitfalls that may lead to misinterpretations of the scans in various clinical settings.

Insulinoma: only in adults?-case reports and literature review

Insulinomas first presenting as refractory seizure disorders are well documented in adulthood but rarely found in children. Only a few cases of childhood insulinoma have been reported so far. We report on two adolescents with hyperinsulinaemic hypoglycaemia, initially misdiagnosed as epilepsy and migraine accompagnée, and compare those to other cases published. Localization of insulinoma was challenging and, in one patient, angiography with selective arterial calcium stimulation and hepatic venous sampling in addition to CT and MRI was necessary. In these patients, long-term recovery was achieved by laparoscopic distal pancreatic resection in one and by conventional enucleation in the pancreatic head in the second patient. In contrast to adults, macrosomy and a decrease in school performance were the main symptoms and, during fasting, impaired cognitive function occurred after a relatively short period and at a higher glucose threshold or lower insulin/glucose ratio, respectively. Neuroglycopenic signs may be attributed to behaviour abnormalities or seizure disorders but in children and adolescents may already be caused by insulinoma. In these cases, timely diagnosis as well as tumour resection ensure long-term cure.

¹⁸F-DOPA PET/computed tomography imaging

18F-DOPA is a radiopharmaceutical with interesting clinical applications and promising performances in the evaluation of the integrity of dopaminergic pathways, brain tumors, NETs (especially MTCs, paragangliomas, and pheochromocytomas), and congenital hyperinsulinism. 18F-DOPA traces a very specific metabolic pathway and has a very precise biodistribution pattern. As for any radiopharmaceutical, the knowledge of the normal distribution of 18F-DOPA, its physiologic variants, and its possible pitfalls is essential for the correct interpretation of PET scans. Moreover, it is important to be aware of the potential false-positive and false-negative episodes that can occur in the various clinical settings.

Hyperinsulinaemic hypoglycaemia:genetic mechanisms, diagnosis and management

Hyperinsulinaemic hypoglycaemia (HH) is characterized by unregulated insulin secretion from pancreatic β-cells. Untreated hypoglycaemia in infants can lead to seizures, developmental delay, and subsequent permanent brain injury. Early identification and meticulous managementof these patients is vital to prevent neurological insult. Mutations in eight different genes (ABCC8, KCNJ11, GLUD1, CGK, HADH, SLC16A1, HNF4A and UCP2) have been identified to date in patients with congenital forms of hyperinsulinism (CHI). The most severe forms of CHI are due to mutations in ABCC8 and KCJN11, which encode the two components of pancreatic β-cell ATP-sensitive potassium channel. Recent advancement in understanding the genetic aetiology, histological characterisation into focal and diffuse variety combined with improved imaging (such as fluorine 18 L-3, 4-dihydroxyphenylalanine positron emission tomography 18F-DOPA-PET scanning) and laparoscopic surgical techniques have greatly improved management. In adults, HH can be due to an insulinoma, pancreatogenous hypoglycaemic syndrome, post gastric-bypass surgery for morbid obesity as well as to mutations in insulin receptor gene. This review provides an overview of the molecular basis of CHI and outlines the clinical presentation, diagnostic criteria, and management of these patients.

The contribution of rapid KATP channel gene mutation analysis to the clinical management of children with congenital hyperinsulinism

OBJECTIVE

In children with congenital hyperinsulinism (CHI), K(ATP) channel genes (ABCC8 and KCNJ11) can be screened rapidly for potential pathogenic mutations. We aimed to assess the contribution of rapid genetic testing to the clinical management of CHI.

DESIGN

Follow-up observational study at two CHI referral hospitals.

METHODS

Clinical outcomes such as subtotal pancreatectomy, (18)F-Dopa positron emission tomography-computed tomography (PET-CT) scanning, stability on medical treatment and remission were assessed in a cohort of 101 children with CHI.

RESULTS

In total, 32 (32%) children had pathogenic mutations in K(ATP) channel genes (27 in ABCC8 and five in KCNJ11), of which 11 (34%) were novel. In those negative at initial screening, other mutations (GLUD1, GCK, and HNF4A) were identified in three children. Those with homozygous/compound heterozygous ABCC8/KCNJ11 mutations were more likely to require a subtotal pancreatectomy CHI (7/10, 70%). Those with paternal heterozygous mutations were investigated with (18)F-Dopa PET-CT scanning and 7/13 (54%) had a focal lesionectomy, whereas four (31%) required subtotal pancreatectomy for diffuse CHI. Those with maternal heterozygous mutations were most likely to achieve remission (5/5, 100%). In 66 with no identified mutation, 43 (65%) achieved remission, 22 (33%) were stable on medical treatment and only one child required a subtotal pancreatectomy.

CONCLUSIONS

Rapid genetic analysis is important in the management pathway of CHI; it provides aetiological confirmation of the diagnosis, indicates the likely need for a subtotal pancreatectomy and identifies those who require (18)F-Dopa PET-CT scanning. In the absence of a mutation, reassurance of a favourable outcome can be given early in the course of CHI.

Visualization of the focus in congenital hyperinsulinism by intraoperative sonography

In surgery for focal congenital hyperinsulinism (CHI), the identification and complete resection of the focus without collateral damage is of utmost importance. In a pilot study we applied intra-abdominal high-frequency sonography during surgery for focal CHI in 2 infants. The focus could be identified, its relation to the pancreatic and common bile duct could be shown, and the typical octopus-like tentacles could be demonstrated. In one case the resection was successful; in the other it was not. These preliminary results suggest that intraoperative sonography could be a valuable tool in the surgical therapy of focal CHI and warrants further evaluation in a clinical study.

The predictive value of preoperative fluorine-18-L-3,4-dihydroxyphenylalanine positron emission tomography-computed tomography scans in children with congenital hyperinsulinism of infancy

BACKGROUND/PURPOSE

In congenital hyperinsulinism (CHI) of infancy, the use of preoperative fluorine-18-L-3,4-dihydroxyphenylalanine-positron emission tomography-computed tomography ((18)F-DOPA-PET-CT) scan has recently been reported. The aim of this study was to evaluate the accuracy of this technique in discriminating between diffuse and focal CHI and the anatomical localization of focal lesions.

METHODS

Between 2006 and 2010, (18)F-DOPA-PET scan was performed in 19 children with CHI (median age, 2 months; range, 1-12 months) who were not responding to medical therapy and underwent laparoscopic or open surgery. The findings of (18)F-DOPA-PET scan were correlated with histology.

RESULTS

In 5 children, (18)F-DOPA-PET scan showed diffuse pancreatic uptake, confirmed at histology and supporting the genetic suspicion of diffuse disease. In 14 children, (18)F-DOPA-PET scan indicated focal pancreatic uptake, which corresponded to histology. However, in 5 patients (36%), (18)F-DOPA-PET scan was inaccurate in defining the location of the lesion (n = 3), size of the lesion (n = 1), or both location and size (n = 1), leading to an inaccurate pancreatic resection.

CONCLUSIONS

Fluorine-18-L-3,4-dihydroxyphenylalanine-positron emission tomography-computed tomography scan discriminates between diffuse and focal forms of CHI. In focal forms, (18)F-DOPA-PET scan is useful in 2/3 of patients in defining the site and dimension of the focal lesion. Intraoperative histologic confirmation of complete focal lesion resection is needed.

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.

Advances in the diagnosis and management of hyperinsulinemic hypoglycemia

Hyperinsulinemic hypoglycemia (HH) is a consequence of unregulated insulin secretion by pancreatic beta-cells and is a major cause of hypoglycemic brain injury and mental retardation. Congenital HH is caused by mutations in genes involved in regulation of insulin secretion, seven of which have been identified (ABCC8, KCNJ11, GLUD1, CGK, HADH, SLC16A1 and HNF4A). Severe forms of congenital HH are caused by mutations in ABCC8 and KCNJ11, which encode the two components of the pancreatic beta-cell ATP-sensitive potassium channel. Mutations in HNF4A, GLUD1, CGK, and HADH lead to transient or persistent HH, whereas mutations in SLC16A1 cause exercise-induced HH. Rapid genetic analysis combined with an understanding of the histological features (focal or diffuse disease) of congenital HH and the introduction of (18)F-L-3,4-dihydroxyphenylalanine PET-CT to guide laparoscopic surgery have totally transformed the clinical approach to this complex disease. Adult-onset HH is mostly caused by an insulinoma; however, it has also been reported to present as postprandial HH in patients with noninsulinoma pancreatogenous hypoglycemia syndrome, in those who have undergone gastric-bypass surgery for morbid obesity, and in those with mutations in the insulin-receptor gene.

Advances in molecular imaging of pancreatic beta cells

The development of non-invasive imaging methods for early diagnosis of beta cell associated metabolic diseases, including type 1 and type 2 diabetes (T1D and T2D), has recently drawn interest from the molecular imaging community and clinical investigators. Due to the challenges imposed by the location of the pancreas, the sparsely dispersed beta cell population within the pancreas, and the poor understanding of the pathogenesis of the diseases, clinical diagnosis of beta cell abnormalities is still limited. Current diagnostic methods are invasive, often inaccurate, and usually performed post-onset of the disease. Advances in imaging techniques for probing beta cell mass and function are needed to address this critical health care problem. A variety of imaging techniques have been tested for the assessment of pancreatic beta cell islets. Here we discuss current advances in magnetic resonance imaging (MRI), bioluminescence imaging (BLI), and nuclear imaging for the study of beta cell diseases. Spurred by early successes in nuclear imaging techniques for beta cells, especially positron emission tomography (PET), the need for beta cell specific ligands has expanded. Progress for obtaining such ligands is presented. We report our preliminary efforts of developing such a peptidic ligand for PET imaging of pancreatic beta cells.

Improved staging of patients with carcinoid and islet cell tumors with 18F-dihydroxy-phenyl-alanine and 11C-5-hydroxy-tryptophan positron emission tomography

PURPOSE

To evaluate and compare diagnostic sensitivity of positron emission tomography (PET) scanning in carcinoid and islet cell tumor patients with a serotonin and a catecholamine precursor as tracers.

PATIENTS AND METHODS

Carcinoid (n = 24) or pancreatic islet cell tumor (n = 23) patients with at least one lesion on conventional imaging including somatostatin receptor scintigraphy (SRS) and computed tomography (CT) scan underwent (11)C-5-hydroxytryptophan ((11)C-5-HTP) PET and 6-[F-18]fluoro-L-dihydroxy-phenylalanine ((18)F-DOPA) PET. PET findings were compared with a composite reference standard derived from all available imaging along with clinical and cytologic/histologic information.

RESULTS

In carcinoid tumor patients, per-patient analysis showed sensitivities for (11)C-5-HTP PET, (18)F-DOPA PET, SRS, and CT of 100%, 96%, 86%, 96%, respectively, and in islet cell tumors of 100%, 89%, 78%, 87%, respectively. In carcinoid patients, per-lesion analysis revealed sensitivities for (11)C-5-HTP PET, (11)C-5-HTP PET/CT, (18)F-DOPA PET, (18)F-DOPA PET/CT, SRS, SRS/CT, and CT alone of, respectively, 78%, 89%, 87%, 98%, 49%, 73%, and 63% and in islet cell tumors of 67%, 96%, 41%, 80%, 46%, 77%, and 68%, respectively. In all carcinoid patients (18)F-DOPA PET and (11)C-5-HTP PET detected more lesions than SRS (P < .001). (11)C-5-HTP PET was superior to (18)F-DOPA PET in islet cell tumors (P < .0001). In all cases, CT improved the sensitivity of the nuclear scans.

CONCLUSION

(18)F-DOPA PET/CT is the optimal imaging modality for staging in carcinoid patients and (11)C-5-HTP PET/CT in islet cell tumor patients.

6-L-18F-fluorodihydroxyphenylalanine PET in neuroendocrine tumors: basic aspects and emerging clinical applications

In recent years, 6-l-18F-fluorodihydroxyphenylalanine (18F-DOPA) PET has emerged as a new diagnostic tool for the imaging of neuroendocrine tumors. This application is based on the unique property of neuroendocrine tumors to produce and secrete various substances, a process that requires the uptake of metabolic precursors, which leads to the uptake of 18F-DOPA. This nonsystematic review first describes basic aspects of 18F-DOPA imaging, including radiosynthesis, factors involved in tracer uptake, and various aspects of metabolism and imaging. Subsequently, this review provides an overview of current clinical applications in neuroendocrine tumors, including carcinoid tumors, pancreatic islet cell tumors, pheochromocytoma, paraganglioma, medullary thyroid cancer, hyperinsulinism, and various other clinical entities. The application of PET/CT in carcinoid tumors has unsurpassed sensitivity. In medullary thyroid cancer, pheochromocytoma, and hyperinsulinism, results are also excellent and contribute significantly to clinical management. In the remaining conditions, the initial experience with 18F-DOPA PET indicates that it seems to be less valuable, but further study is required.

Neonatal hyperinsulinism: clinicopathologic correlation

Neonatal hyperinsulinism is a life-threatening disease that, when treated by total pancreatectomy, leads to diabetes and pancreatic insufficiency. A more conservative approach is now possible since the separation of the disease into a nonrecurring focal form, which is cured by partial surgery, and a diffuse form, which necessitates total pancreas removal only in cases of medical treatment failure. The pathogenesis of the disease is now divided into K-channel disease (hyperinsulinemic hypoglycemia, familial [HHF] 1 and 2), which can mandate surgery, and other metabolic causes, HHF 3 to 6, which are treated medically in most patients. The diffuse form is inherited as a recessive gene on chromosome 11, whereas most cases of the focal form are caused by a sulfonylurea receptor 1 defect inherited from the father, which is associated with a loss of heterozygosity on the corresponding part of the mother's chromosome 11. The rare bifocal forms result from a maternal loss of heterozygosity specific to each focus. Paternal disomy of chromosome 11 is a rare cause of a condition similar to Beckwith-Wiedemann syndrome. A preoperative PET scan with fluorodihydroxyphenylalanine and perioperative frozen-section confirmation are the types of studies done before surgery when needed. Adult variants of the disease are less well defined at the present time.