Prospective comparison of biphasic contrast-enhanced CT, volume perfusion CT, and 3 Tesla MRI with diffusion-weighted imaging for insulinoma detection

Improved Localization of Insulinomas Using 68Ga-NODAGA-Exendin-4 PET/CT

Precise anatomic localization of insulinomas is crucial for surgical treatment. Current routine noninvasive imaging techniques, including CT, MRI, and 68Ga-DOTA-somatostatin analog (DOTA-SSA) PET/CT, have limited sensitivity. Endoscopic ultrasound is highly sensitive but invasive. In this prospective multicenter study, we compared the diagnostic accuracy of 68Ga-NODAGA-exendin-4 (exendin) PET/CT with all routine imaging procedures for the localization of insulinomas. Methods: Sixty-nine adults with biochemically proven adult endogenous hyperinsulinemic hypoglycemia underwent exendin PET/CT and current routine imaging. Images were evaluated in a clinical reading and in an expert reading. Image quality was determined by quantitative analysis. Results: Based on clinical readings, the accuracy of exendin PET/CT (94.4%; 95% CI, 84.6%-98.8%) was greater than that of DOTA-SSA PET/CT (64.8%; 95% CI, 50.6%-77.3%), contrast-enhanced CT/contrast-enhanced diffusion-weighted imaging-MRI (83.3%; 95% CI, 70.7%-92.1%), and endoscopic ultrasound (82.8%; 95% CI, 64.1%-94.1%). In 13% of patients, a correct diagnosis was only reached after exendin PET/CT. Interobserver agreement between readings was higher for exendin PET/CT than for DOTA-SSA PET/CT and contrast-enhanced CT/contrast-enhanced diffusion-weighted imaging-MRI (Cohen κ, 1.0 vs. 0.5 and 0.55). Exendin PET/CT provided a higher insulinoma-to-background ratio (15.3 ± 6.7 vs. 5.2 ± 3.0) and contrast-to-noise ratio (22.6 ± 11.1 vs. 5.1 ± 3.7) than did DOTA-SSA PET/CT. Conclusion: This study demonstrates the superiority of exendin PET/CT in a unique prospective comparison to all current routine imaging modalities for preoperative localization of benign insulinomas, providing the level of evidence needed for clinical implementation.

Insulinoma detection and surgery planning: a comparative study of 5.0T MRI versus 3.0T MRI and MDCT

PURPOSE

To compare the ability among 5.0T MRI, 3.0T MRI and MDCT in identifying insulinomas and determining the tumor-to-duct relationship.

METHODS

A consecutive series of patients highly suspected of insulinomas were enrolled between October 2021 and February 2024, who underwent 5.0T MRI preoperatively, as well as 3.0T MRI or MDCT. The subjective and objective image quality, lesion-to-pancreas contrast, clarity of main pancreatic duct (MPD) and tumor-to-duct relationship at 5.0T, 3.0T MRI and MDCT were evaluated by three observers. The correlation between tumor-duct distance and clinically relevant postoperative pancreatic fistula (CR-POPF) risk was analyzed.

RESULTS

Forty patients (14 men; mean age, 46.4 ± 16.5 years) with insulinomas were included in this study. 21 of them underwent both 5.0T and 3.0T MRI; and 38 of them underwent 5.0T MRI and MDCT. The intra- and inter-observer agreement of 5.0T MRI were good to excellent. 5.0T showed significantly higher subjective and objective image quality on T1WI and DWI compared to 3.0T (p < 0.05). Lesion-to-pancreas contrast was superior across all sequences at 5.0T compared to 3.0T(p < 0.05). A head-to-head comparison of patients who received both 5.0T and 3.0T MRI demonstrated that tumor detection was superior with 5.0T MRI (5.0T: 100%; 3.0 T: 92.0%, p < 0.05). Feasibility of tumor-to-duct relationship assessment was superior at 5.0T, compared to 3.0T and MDCT (93.2%, 64.0% and 52.3%, respectively, p < 0.05). Tumor-duct distance could predict CR-POPF after enucleation surgery (areas under the ROC curve 0.79, p = 0.01).

CONCLUSION

5.0T MRI exhibits certain superiority in detecting insulinomas and assessing tumor-to-duct relationship compared to 3.0T MRI and MDCT.

Sporadic gastrinoma with refractory benign esophageal stricture: A case report

BACKGROUND

Gastrinoma is characterized by an excessive release of gastrin, leading to hypersecretion of gastric acid, subsequently resulting in recurrent peptic ulcers, chronic diarrhea, and even esophageal strictures. This case report aims to improve awareness and facilitate early diagnosis and treatment of gastrinoma by presenting a rare case of gastrinoma with refractory benign esophageal stricture (RBES). Additionally, it highlights the persistent challenges that gastroenterologists encounter in managing RBES.

CASE SUMMARY

This case demonstrates a patient with gastrinoma who developed RBES and complete esophageal obstruction despite management with maximal acid suppressive therapy, multiple endoscopic bougie dilations and endoscopic incisional therapy (EIT).

CONCLUSION

It is essential to diagnose gastrinoma as early as possible, as inadequately controlled acid secretion over an extended period increases the risk of developing severe esophageal strictures. In patients with esophageal strictures causing complete luminal obstruction, blind reopening EIT presents challenges and carries a high risk of perforation.

Insulinoma Presenting as Seizures: Challenges of Managing a Rare Disease in a Resource-challenged Setting

Insulinomas are functioning pancreatic neuroendocrine tumors (NETs). They secrete insulin, and hence, present with hypoglycemia. We report a case of insulinoma in a 16-year-old girl presenting as seizures. She was initially managed at a private clinic and later commenced on carbamazepine when convulsion persisted. Convulsions were generalized, associated with dizziness and altered sensorium, often preceded by hunger and physical exertion, but relieved by the intake of carbonated drinks and fruit juice. She was referred to the neurology clinic when seizures persisted, despite the use of anticonvulsant. She was later referred to the endocrine clinic on suspicion of insulinoma when her random blood glucose (BG) was found to be low during an episode of convulsion. She was moderately obese but other examination findings were normal. She had a 72-hour prolonged fast, which was terminated when hypoglycemia (BG = 2.2 mmol/L) ensued after 12 hours, with elevated serum insulin and C-peptide. Abdominal magnetic resonance imaging scan showed a pancreatic tumor suggestive of insulinoma. She subsequently had distal pancreatectomy performed with complete resolution of symptoms. Unusual presentation of insulinoma may delay diagnosis, resulting in wastage of resources with increased morbidities and mortality.

Theranostic in GLP-1R molecular imaging: challenges and emerging opportunities

Theranostic in nuclear medicine combines diagnostic imaging and internal irradiation therapy using different therapeutic nuclear probes for visual diagnosis and precise treatment. GLP-1R is a popular receptor target in endocrine diseases, non-alcoholic steatohepatitis, tumors, and other areas. Likewise, it has also made breakthroughs in the development of molecular imaging. It was recognized that GLP-1R imaging originated from the study of insulinoma and afterwards was expanded in application including islet transplantation, pancreatic β-cell mass measurement, and ATP-dependent potassium channel-related endocrine diseases. Fortunately, GLP-1R molecular imaging has been involved in ischemic cardiomyocytes and neurodegenerative diseases. These signs illustrate the power of GLP-1R molecular imaging in the development of medicine. However, it is still limited to imaging diagnosis research in the current molecular imaging environment. The lack of molecular-targeted therapeutics related report hinders its radiology theranostic. In this article, the current research status, challenges, and emerging opportunities for GLP-1R molecular imaging are discussed in order to open a new path for theranostics and to promote the evolution of molecular medicine.

Pancreatic CT perfusion: quantitative meta-analysis of disease discrimination, protocol development, and effect of CT parameters

BACKGROUND

This study provides a quantitative meta-analysis of pancreatic CT perfusion studies, investigating choice of study parameters, ability for quantitative discrimination of pancreatic diseases, and influence of acquisition and reconstruction parameters on reported results.

METHODS

Based on a PubMed search with key terms 'pancreas' or 'pancreatic,' 'dynamic' or 'perfusion,' and 'computed tomography' or 'CT,' 491 articles published between 1982 and 2020 were screened for inclusion in the study. Inclusion criteria were: reported original data, human subjects, five or more datasets, measurements of pancreas or pancreatic pathologies, and reported quantitative perfusion parameters. Study parameters and reported quantitative measurements were extracted, and heterogeneity of study parameters and trends over time are analyzed. Pooled data were tested with weighted ANOVA and ANCOVA models for differences in perfusion results between normal pancreas, pancreatitis, PDAC (pancreatic ductal adenocarcinoma), and non-PDAC (e.g., neuroendocrine tumors, insulinomas) and based on study parameters.

RESULTS

Reported acquisition parameters were heterogeneous, except for contrast agent amount and injection rate. Tube potential and slice thickness decreased, whereas tube current time product and scan coverage increased over time. Blood flow and blood volume showed significant differences between pathologies (both p < 0.001), unlike permeability (p = 0.11). Study parameters showed a significant effect on reported quantitative measurements (p < 0.05).

CONCLUSIONS

Significant differences in perfusion measurements between pathologies could be shown for pooled data despite observed heterogeneity in study parameters. Statistical analysis indicates most influential parameters for future optimization and standardization of acquisition protocols.

CRITICAL RELEVANCE STATEMENT

Quantitative CT perfusion enables differentiation of pancreatic pathologies despite the heterogeneity of study parameters in current clinical practice.

Occult insulinoma with treatment refractory, severe hypoglycaemia in multiple endocrine neoplasia type 1 syndrome; difficulties faced during diagnosis, localization and management; a case report

BACKGROUND

Multiple endocrine neoplasia type 1 (MEN 1) syndrome is a rare, complex genetic disorder characterized by increased predisposition to tumorigenesis in multiple endocrine and non-endocrine tissues. Diagnosis and management of MEN 1 syndrome is challenging due to its vast heterogeneity in clinical presentation.

CASE PRESENTATION

A 23-year-old female, previously diagnosed with Polycystic Ovarian Syndrome (PCOS) and pituitary microprolactinoma presented with drowsiness,confusion and profuse sweating developing over a period of one day. It was preceded by fluctuating, hallucinatory behavior for two weeks duration. There was recent increase in appetite with significant weight gain. There was no fever, seizures or symptoms suggestive of meningism. Her Body mass index(BMI) was 32 kg/m2.She had signs of hyperandrogenism. Multiple cutaneous collagenomas were noted on anterior chest and abdominal wall. Her Glasgow Coma Scale was 9/15. Pupils were sluggishly reactive to light. Tendon reflexes were exaggerated with up going planter reflexes. Moderate hepatomegaly was present. Rest of the clinical examination was normal. Laboratory evaluation confirmed endogenous hyperinsulinaemic hypoglycaemia suggestive of an insulinoma. Hypercalcemia with elevated parathyroid hormone level suggested a parathyroid adenoma. Presence of insulinoma, primary hyperparathyroidism and pituitary microadenoma, in 3rd decade of life with characteristic cutaneous tumours was suggestive of a clinical diagnosis of MEN 1 syndrome. Recurrent, severe hypoglycaemia complicated with hypoglycaemic encephalopathy refractory to continuous, parenteral glucose supplementation and optimal pharmacotherapy complicated the clinical course. Insulinoma was localized with selective arterial calcium stimulation test. Distal pancreatectomy and four gland parathyroidectomy was performed leading to resolution of symptoms.

CONCLUSIONS

Renal calculi or characteristic cutaneous lesions might be the only forewarning clinical manifestations of an undiagnosed MEN 1 syndrome impending a life-threatening presentation. Comprehensive management of MEN 1 syndrome requires multi-disciplinary approach with advanced imaging modalities, advanced surgical procedures and long-term follow up due to its heterogeneous presentation and the varying severity depending on the disease phenotype.

Glucagon-like Peptide-1 Receptor as Emerging Target: Will It Make It to the Clinic?

The glucagon-like peptide-1 receptor (GLP-1R) is an emerging target due to its high expression in benign insulinomas as well as in islet cell hypertrophia/hyperplasia (nesidioblastosis) and pancreatic β-cells. In 2008, occult insulinomas were localized for the first time in men using the metabolically stable radiolabeled glucagon-like peptide-1 (GLP-1) agonist [Lys40(Ahx-DTPA-111In)NH2]-exendin-4 (111In-DTPA-exendin-4). Afterward, several radiopharmaceuticals for GLP-1R PET/CT imaging were synthesized and evaluated, for example, [Nle14,Lys40(Ahx-DOTA-68Ga)NH2]-exendin-4 (68Ga-DOTA-exendin-4), [Cys40(MAL-NOTA-68Ga)NH2]-exendin-4 (68Ga-NOTA-exendin-4), and [Lys40(NODAGA-68Ga)NH2]-exendin-4 (68Ga-NODAGA-exendin-4). Several prospective comparison studies provided evidence that GLP-1R PET/CT is significantly more sensitive than contrast-enhanced MRI (ceMRI), contrast-enhanced CT (ceCT), GLP-1R SPECT/CT, somatostatin receptor PET/CT, and SPECT/CT in the detection of benign insulinomas, and insulinomas in the context of multiple endocrine neoplasia type 1. As a result, the European Neuroendocrine Tumor Society guidelines recommend GLP-1R imaging or selective intraarterial calcium stimulation and venous sampling (ASVS) in patients for whom there is a clinical suspicion of having an insulinoma but who have a negative ceMRI/ceCT or negative endoscopic ultrasound. Furthermore, there is growing evidence that GLP-1R PET/CT can visualize and localize adult nesidioblastosis. This is clinically relevant as the distinction between focal and diffuse nesidioblastosis is critical in directing a therapeutic strategy in these patients. Prospective studies have proven the clinical relevance of GLP-1R imaging as it is often the only imaging modality able to localize the insulinoma or nesidioblastosis. It is therefore likely that this noninvasive imaging modality will replace the invasive localization of insulinomas using ASVS. More experimental indications for GLP-1R imaging include the diagnosis of an insulinoma/nesidioblastosis in patients with postprandial hypoglycemia after bariatric bypass surgery and monitoring β-cells in patients with brittle type 1 diabetes after islet-cell transplantation. We believe that these indications and possibly future indications will bring GLP-1R imaging to the clinic.

Investigating difficult to detect pancreatic lesions: Characterization of benign pancreatic islet cell tumors using multiparametric pancreatic 3-T MRI

Introduction

Pancreatic islet-cell tumors (PICT) often present with atypical signal-characteristics and are often missed on preoperative imaging. The aim of this study is to provide a multiparametric PICT characterization and investigate factors impeding PICT detection.

Material and methods

This is a detailed MRI analysis of a prospective, monocenter study, including 49 consecutive patients (37 female, 12 male; median age 50) with symptoms due to endogenous hyperinsulinemic hypoglycemia (EHH) and mostly negative prior-imaging. All patients received a 3-T MRI and a ⁶⁸Ga-DOTA-exendin-4-PET/CT. Pooled accuracy, sensitivity, specificity and inter-reader agreement were calculated. Reference-standard was histopathology and ⁶⁸Ga-DOTA-Exendin-4-PET/CT in one patient who refused surgery. For PICT analyses, 34 patients with 49 PICTs (48 histologically proven; one ⁶⁸Ga-DOTA-exendin-4-PET/CT positive) were assessed. Dynamic contrast-enhanced (DCE) Magnetic Resonance Images (MRI) with Golden-Angle-Radial-Sparse-Parallel (GRASP) reconstruction, enabling imaging at high spatial and temporal resolution, was used to assess enhancement-patterns of PICTs. Tumor-to-background (T2B) ratio for each sequence and the employed quantitative threshold for conspicuity of PICTs were analyzed in regard to prediction of true-positive PICTs.

Results

Evaluation of 49 patients revealed a pooled lesion-based accuracy, sensitivity and specificity of 70.3%, 72.9% and 62.5%, respectively. Mean PICT size was 12.9±5.3mm for detected, 9.0±2.9mm for undetected PICTs (p-value 0.0112). In-phase T1w detected the most PICT (67.3%). Depending on the sequence, PICTs were isointense and poorly visible in 29–68%. Only 2/41(4.9%) PICTs showed typical signal-characteristics across T1w, T2w, DWI and ceT1w combined. 66.6% of PICTs enhanced simultaneously to the parenchyma, 17.8% early and 15.6% late. Predictor screening analysis showed number of sequences detecting a PICT, lesion size and in-phase T1w T2B ratio had the highest contribution for detecting a true-positive PICT.

Conclusion

The majority of PICTs enhance simultaneously to surrounding parenchyma, present with atypical signal-characteristics and thus are poorly visible. In non-enhancing PICTs, radiologists should search for small lesions most likely conspicuous on unenhanced T1w or DWI.

The appearance of canine insulinoma on dual phase computed tomographic angiography

OBJECTIVES

To further evaluate the appearance of insulinoma in dogs on dual-phase CT angiography, given the disparity of findings in recent publications. To establish whether CT angiographic localisation of insulinoma correlates with surgical findings.

MATERIALS AND METHODS

Single centre study of dogs with a final diagnosis of insulinoma which underwent abdominal CT angiography. Scans were retrospectively re-evaluated for specific features by two board-certified veterinary radiologists. These findings were also subsequently compared to surgical and histopathological reports to determine the accuracy of lesion localisation on CT.

RESULTS

Thirty-five cases were included in final analysis, with pancreatic nodules identified in 33. Twenty-one were confirmed as insulinoma with histopathology. Jack Russell Terriers were over-represented. Twenty of 21 cases with confirmed insulinoma and 27 of 33 overall showed hyperattenuation in the arterial phase. The mean size of pancreatic insulinoma on CT was 15.1 mm, and 18.2% were larger than 20 mm. Eighteen of 21 confirmed and eight of 12 suspected insulinomas caused a deformation of the pancreatic shape, with two only identified as a result of this feature as these lesions were isoattenuating throughout the study. Pancreatic insulinoma location at surgery matched that described on the CT images in 17 of 19 cases where location was described in the surgical report.

CLINICAL SIGNIFICANCE

In contrast to recent publications, this study suggests hyperattenuation of insulinomas in the arterial phase is a predominant feature, and that hypoattenuation or isoattenuation are much less common. CT angiography is accurate in prediction of lesion location before surgery in most cases.

Value of multi-detector computed tomography during intra-arterial infusion of contrast medium for locating insulinomas

Objective

This study aimed to evaluate the accuracy of multi-detector computed tomography (CT) during intra-arterial infusion of contrast medium (MDCT-IA) for locating insulinomas.

Methods

This retrospective study included patients with insulinomas who underwent surgery at the Chinese PLA General Hospital in 2013 to 2014. The patients’ case notes and investigation results were reviewed. Preoperative tumor localization was carried out by MDCT-IA and noninvasive methods including MDCT, magnetic resonance imaging (MRI), and contrast-enhanced ultrasound (CEUS). Insulinoma localization using these methods was compared with the histologically confirmed location following surgical excision.

Results

Twelve insulinomas were identified in 12 patients, all of which were treated surgically. All patients received MDCT-IA (100%), 11 patients also underwent MRI (91.7%), seven underwent CT (58.3%), and all 12 underwent CEUS (100%). Tumor localization was determined successfully in 12/12 patients by MDCT-IA (100%), in 9/11 by MRI (81.8%), 4/7 by CT (57.1%), and 7/12 by CEUS (58.3%). Overall, MDCT-IA correctly localized 100% of the lesions.

Conclusions

MDCT-IA can be used to determine the preoperative localization of insulinomas.

Diagnosis value preoperative localization of insulinoma by diffusion-weighted imaging: A pilot study

Insulinoma is the most common functional neuroendocrine tumor that originates from the islet of beta cells. Insulinoma is usually an isolated benign tumor and small in size (<2 cm). Due to the small size of the lesion, it often leads to difficulty in clinical preoperative localization diagnosis. However, we have unexpectedly discovered that the diffusion-weighted-imaging (DWI) adds great value in the preoperative localization diagnosis of insulinoma in non-invasive examination technique.We verified using operative pathology data and retrospectively analyzed the clinical and imageology findings of 5 cases who reported to have an insulinoma. All the 5 cases underwent DWI examination, among non-contrast enhanced magnetic resonance imaging (MRI) in 1 case, contrast-enhanced MRI in 4 cases.Five cases of DWI showed a nodular high signal <1.3 cm with pancreatic tail in 3 cases, pancreatic neck, and pancreatic head in 1 case each, respectively. Non-contrast enhanced MRI showed suspicious abnormal signals in the tail of the pancreas were detected in 1 case. MRI enhanced scans presented 2 cases with abnormal enhancement in the arterial phase and 2 cases without abnormal enhancement in arterial phase. Also, 3 cases showed mild persistence enhanced in the portal venous phase and delayed phase. However, 1 case remained normal in the portal venous phase and the delay period.DWI examination has high clinical value in the localization diagnosis of insulinoma and thus it can be used as a routine examination for preoperative localization diagnosis.

Prospective Comparison of Reduced Field-of-View (rFOV) and Full FOV (fFOV) Diffusion-Weighted Imaging (DWI) in the Assessment of Insulinoma: Image Quality and Lesion Detection

RATIONALE AND OBJECTIVES

To prospectively compare the image quality (IQ) and lesion detection performance of reduced field-of-view (rFOV) and full FOV (fFOV) diffusion-weighted imaging (DWI) sequences in detecting insulinomas.

MATERIALS AND METHODS

From October 2017 to September 2018, 67 patients with suspected insulinomas were prospectively enrolled and underwent imaging with both types of DWI sequences. The slice thickness (4 mm) and slice gaps (1 mm) were the same for the two DWI sequences, and the TR/TE was 2235/56 ms for the rFOV sequence and 1892/63 ms for the fFOV sequence. Three radiologists independently assessed the imaging quality (IQ) subjectively with a 5-point scale and objectively with signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements. The IQ scores, CNR, SNR, lesion detection rates, and ADC values were compared. Receiver operating characteristic curves were generated, and the area under the curve (AUC) was used to compare the diagnostic performance.

RESULTS

Fifty patients were tumor positive, with 65 tumors (size: 1.31 ± 0.77 cm, range: 0.6-5.8 cm). The IQ score, SNR, and CNR were significantly higher for rFOV DWI than for fFOV DWI (IQ: 3.64 ± 0.487 vs 3.310 ± 0.577, SNR: 22.520 ± 8.690 vs 10.284 ± 3.321, CNR: 3.454 ± 2.642 vs 1.327 ± 2.801, and all p < 0.05). For lesions less than 1.5 cm (n = 55), the lesion detection rates of the rFOV were statistically improved compared to those of the fFOV (90.7% vs. 75.9%, p = 0.039). The sensitivity of lesion detection was significantly improved with the rFOV-DWI sequences compared to that with the fFOV-DWI sequences (0.924 vs. 0.773, p = 0.013). The ADC values of the two DWI sequences were consistent for insulinomas and normal parenchyma.

CONCLUSION

Considering the improvements in overall IQ and lesion detection and the consistency of ADC measurements, we suggest that rFOV DWI is a reliable auxiliary alternative to fFOV DWI for clinical practice in the detection of pancreatic insulinomas.

Pitfalls in the Detection of Insulinomas With Glucagon-Like Peptide-1 Receptor Imaging

PURPOSE

Physiological pancreaticoduodenal uptake of radiolabeled exendin-4 in Brunner glands of the proximal duodenum is the most common pitfall for false interpretation of glucagon-like peptide-1 receptor (GLP-1R) imaging. The aim of this study was to analyze the pancreaticoduodenal uptake in GLP-1R PET/CT and SPECT/CT images and to identify additional potential reading pitfalls in patients with suspected insulinoma.

METHODS

A post hoc analysis of a prospective study, including 52 consecutive patients, was performed. All patients underwent 1 Ga-exendin-4 PET/CT and 2 In-exendin-4 SPECT/CT scans (4 and 72 hours postinjection) in a randomized crossover order. Three board-certified nuclear medicine physicians read all scans independently. They were unaware of other results. Reference standard was surgery with histopathological confirmation of an insulinoma/nesidioblastosis and normalization of blood glucose levels after surgery.

RESULTS

There were no false-positive readings. However, there were a number of false-negative PET/CT and SPECT/CT readings, respectively: (1) due to false interpretation of uptake in the pancreaticoduodenal region (falsely interpreted as physiological uptake in Brunner glands instead of an insulinoma in 0.6% vs 9.0%), (2) due to ectopic insulinoma (0% vs 2.6%), (3) due to small insulinoma (1.9% vs 5.1%), (4) due to insulinoma overlap with kidneys (1.9% vs 4.5%), and (5) due to nesidioblastosis (0.6% and 1.9%). Pitfalls were identified in all GLP-1R PET/CT and SPECT/CT scans.

CONCLUSIONS

Peripancreatic uptake, small size of an insulinoma, insulinoma overlap with kidneys, and presence of nesidioblastosis are potential pitfalls in GLP-1R imaging, which can lead to false reading results.

Essentials of Insulinoma Localization with Selective Arterial Calcium Stimulation and Hepatic Venous Sampling

Insulinomas are the most common functional pancreatic neuroendocrine tumor. Most insulinomas can be localized non-invasively with cross-sectional and nuclear imaging. Selective arterial calcium stimulation and hepatic venous sampling is an effective and safe minimally-invasive procedure for insulinoma localization that may be utilized when non-invasive techniques are inconclusive. The procedure’s technical success and proper interpretation of its results is dependent on the interventional radiologist’s knowledge of normal and variant pancreatic arterial perfusion. Accurate pre-operative localization aids in successful surgical resection. Technical and anatomic considerations of insulinoma localization with selective arterial calcium stimulation and hepatic venous sampling are reviewed.

Innovative imaging of insulinoma: the end of sampling? A review

Receptors for the incretin glucagon-like peptide-1 (GLP-1R) have been found overexpressed in selected types of human tumors and may, therefore, play an increasingly important role in endocrine gastrointestinal tumor management. In particular, virtually all benign insulinomas express GLP-1R in high density. Targeting GLP-1R with indium-111, technetium-99m or gallium-68-labeled exendin-4 offers a new approach that permits the successful localization of small benign insulinomas. It is likely that this new non-invasive technique has the potential to replace the invasive localization of insulinomas by selective arterial stimulation and venous sampling. In contrast to benign insulinomas, malignant insulin-secreting neuroendocrine tumors express GLP-1R in only one-third of the cases, while they more often express the somatostatin subtype 2 receptors. Importantly, one of the two receptors appears to be always overexpressed. In special cases of endogenous hyperinsulinemic hypoglycemia (EHH), that is, in the context of MEN-1 or adult nesidioblastosis GLP-1R imaging is useful whereas in postprandial hypoglycemia in the context of bariatric surgery, GLP-1R imaging is probably not helpful. This review focuses on the potential use of GLP-1R imaging in the differential diagnosis of EHH.

Detection of insulinoma: one-stop pancreatic perfusion CT with calculated mean temporal images can replace the combination of bi-phasic plus perfusion scan

OBJECTIVE

To evaluate the feasibility of one-stop pancreatic perfusion CT with mean temporal (MT) imaging replacing the combination of a bi-phasic scan plus a perfusion scan to detect insulinoma.

MATERIAL AND METHODS

Forty-five patients with suspected insulinoma, who underwent both biphasic and perfusion CT, were enrolled in this retrospective study. MT datasets including images for different delineation purposes were generated by averaging 3 dynamic datasets from perfusion CT, which are MTA for arterial, MTPV for portal vein and MTO for lesions. Two readers assessed the image quality and diagnostic performance separately for biphasic and MT datasets. Radiation doses were also assessed. Paired t tests, Wilcoxon signed-rank tests and McNemar's tests were applied for comparison.

RESULTS

Compared with bi-phasic CT images, image noise, SNR and CNR of the MTA and MTPV datasets were all non-inferior (noise and CNR of the portal vein, p = 0.565 and p = 0.227, respectively) or superior (p ≤ 0.001). The subjective image quality was better in the MTA and MTPV images (p < 0.001 to p = 0.004). The sensitivity and NPV of MT images were also better (95% vs 75% and 75% vs 37.5% for reader 1; 97.5% vs 72.5% and 85.7% vs 35.3% for reader 2). Omitting the bi-phasic scan resulted in a dose reduction of 25% ± 4%.

CONCLUSION

MT imaging can allow pancreatic perfusion CT to be used alone without the need for an additional bi-phasic CT in the detection of insulinoma.

KEY POINTS

• Mean temporal images reconstructed from perfusion CT with an averaging technique reproduce usual bi-phasic images (arterial and portal phases). • The image quality of mean temporal images is non-inferior or superior to native bi-phasic CT. The sensitivity and NPV for the diagnosis of insulinoma are better for mean temporal images than for traditional bi-phasic CT. • Mean temporal imaging can allow pancreatic perfusion CT to be used alone without the need for an additional bi-phasic CT in the detection of insulinoma. Radiation dose saving is important.

Targeted Optical Imaging of the Glucagonlike Peptide 1 Receptor Using Exendin-4-IRDye 800CW

The treatment of choice for insulinomas and focal lesions in congenital hyperinsulinism (CHI) is surgery. However, intraoperative detection can be challenging. This challenge could be overcome with intraoperative fluorescence imaging, which provides real-time lesion detection with a high spatial resolution. Here, a novel method for targeted near-infrared (NIR) fluorescence imaging of glucagonlike peptide 1 receptor (GLP-1R)–positive lesions, using the GLP-1 agonist exendin-4 labeled with IRDye 800CW, was examined in vitro and in vivo. Methods: A competitive binding assay was performed using Chinese hamster lung (CHL) cells transfected with GLP-1R. Tracer biodistribution was determined in BALB/c nude mice bearing subcutaneous CHL-GLP-1R xenografts. In vivo NIR fluorescence imaging of CHL-GLP-1R xenografts was performed. Localization of the tracer in the pancreatic islets of BALB/c nude mice was examined using fluorescence microscopy. Laparoscopic imaging was performed to detect the fluorescent signal of the tracer in the pancreas of mini pigs. Results: Exendin-4-IRDye 800CW binds GLP-1R with a half-maximal inhibitory concentration of 3.96 nM. The tracer accumulates in CHL-GLP-1R xenografts. Subcutaneous CHL-GLP-1R xenografts were visualized using in vivo NIR fluorescence imaging. The tracer accumulates specifically in the pancreatic islets of mice, and a clear fluorescent signal was detected in the pancreas of mini pigs. Conclusion: These data provide the first in vivo evidence of the feasibility of targeted fluorescence imaging of GLP-1R–positive lesions. Intraoperative lesion delineation using exendin-4-IRDye 800CW could benefit open as well as laparoscopic surgical procedures for removal of insulinomas and focal lesions in CHI.

68Ga-Exendin-4 PET/CT Detects Insulinomas in Patients With Endogenous Hyperinsulinemic Hypoglycemia in MEN-1

CONTEXT

Surgical intervention is advised in patients with multiple endocrine neoplasia type-1 (MEN-1) and nonfunctioning pancreatic neuroendocrine tumors (PanNETs) with a size ≥20 mm. Functioning PanNETs, such as in patients with endogenous hyperinsulinemic hypoglycemia (EHH) due to (one or multiple) insulinomas, should be treated surgically independent of size. Preoperative localization of insulinomas is critical for surgery.

OBJECTIVE

To evaluate the feasibility and sensitivity of 68Ga-DOTA-exendin-4 positron emission tomography (PET)/CT in the detection of clinically relevant lesions in patients with MEN-1 and EHH in combination with MRI.

DESIGN

Post hoc subgroup analysis of a larger prospective imaging study with 52 patients with EHH.

PATIENTS

Six of 52 consecutive patients with EHH and genetically proven MEN-1 mutation were included.

INTERVENTIONS

All patients received one 68Ga-DOTA-exendin-4 PET/CT and one MRI scan within 3 to 4 days. Thereafter, surgery was performed based on all imaging results.

MAIN OUTCOME MEASURES

Lesion-based sensitivity of PET/CT and MRI for detection of clinically relevant lesions was calculated. Readers were unaware of other results. The reference standard was surgery with histology and treatment outcome. True positive (i.e., clinically relevant lesions) was defined as PanNETs ≥20 mm or insulinoma.

RESULTS

In six patients, 37 PanNETs were confirmed by histopathology. Sensitivity (95% CI) in the detection of clinically relevant lesions for combined PET/CT plus MRI, MRI, and PET/CT was 92.3% (64% to 99.8%), 38.5% (13.9% to 68.4%), and 84.6% (54.6% to 98.1%), respectively (P = 0.014 for the comparison of PET/CT plus MRI vs MRI). Postsurgery, EHH resolved in all patients.

CONCLUSION

68Ga-DOTA-exendin-4 PET/CT is feasible in patients with MEN-1 and EHH. The combination with MRI is superior to MRI alone in the detection of insulinomas and may guide the surgical strategy.

Weight-adapted ultra-low-dose pancreatic perfusion CT: radiation dose, image quality, and perfusion parameters

PURPOSE

We evaluate the reliability and feasibility of weight-adapted ultra-low-dose pancreatic perfusion CT.

METHODS

A total of 100 (47 men, 53 women) patients were enrolled prospectively and were assigned to five groups (A, B, C, D, and E) with different combination of tube voltage and tube current according to their body weight. Radiation dose parameters including volume CT dose index (CTDI) and dose-length product (DLP) were recorded. Image quality was evaluated both subjectively and objectively (noise, signal-to-noise ratio, contrast-to-noise ratio). Perfusion parameters including blood flow (BF), blood volume (BV), and permeability (PMB) were measured. The dose, image quality measurements, and perfusion parameters were compared between the five groups using one-way analysis of variance (ANOVA).

RESULTS

Radiation dose reached 8.7 mSv in patients under 50 kg and was 18.9 mSv in patients above 80 kg. The mean subjective image quality score was above 4.45 on a 5-point scale with good agreement between two radiologists. Groups A-D had equivalent performance on objective image quality (P > 0.05), while Group E performed even better (P < 0.05). No significant differences emerged in comparison with perfusion parameters (BF, BV, PMB) of normal pancreas parenchyma between the five groups.

CONCLUSION

Weight-adapted ultra-low-dose pancreatic perfusion CT can effectively reduce radiation dose without prejudice to image quality, and the perfusion parameters of normal parenchyma are accurate and reliable.

Clinical Management of Malignant Insulinoma: a single Institution's experience over three decades

BACKGROUND

Malignant insulinoma is extremely rare and accounts for only 10% of total insulinoma cases. The goal of this study is to retrospectively analyze clinical data from 15 patients with malignant insulinoma treated at Peking Union Medical College Hospital (PUMCH) from 1984 to April 2017.

METHODS

"Malignant insulinoma" was used as the keywords in the PUMCH medical record retrieval system to search and obtain patients' clinical information. We identified subjects diagnosed with malignant insulinoma based on clinical or surgical pathological signs and subsequently analyzed their clinical data.

RESULTS

Eight males and seven females with a median age at diagnosis of 40 years (38-54 years) were included. Eight patients (53%) had developed metastases at diagnosis, while the others (46.67%) developed metastases during the follow-up visits. The major sites of metastasis were the liver (86.7%), local tissues and blood vessels (33%) and abdominal lymph nodes (13%). All patients displayed neuroglycopenic (100%) and/or autonomic (60%) symptoms, mostly during fasting periods (73.3%), with an average blood glucose level of 1.66 ± 0.51 mmol/L. A total of 93% of the patients had one primary pancreatic lesion, 53% had a lesion in the head of the pancreas, and 47% had a lesion in the tail of the pancreas, with diameters ranging between 0.9 and 6.0 cm. Most liver metastases were multiple lesions. Selective celiac arteriography yielded 100% sensitivity for both primary pancreatic lesions and liver metastases. Most patients received synthetical treatments, including surgery, chemoembolization, and octreotide.

CONCLUSIONS

Malignant insulinomas have a similar diagnostic process to that of benign insulinomas but require far more comprehensive therapies to alleviate hypoglycemic symptoms and extend patients' survival.

Homogenously isoattenuating insulinoma on biphasic contrast-enhanced computed tomography: Little benefits of diffusion-weighted imaging for lesion detection

The aim of the present study was to evaluate the diagnostic benefit of diffusion-weighted imaging (DWI) in the detection of homogenous isoattenuating insulinoma on biphasic contrast-enhanced computed tomography (CT) preoperatively and to determine which magnetic resonance (MR) sequences exhibited the best diagnostic performance. A total of 44 consecutive patients who underwent biphasic contrast-enhanced CT and conventional MR imaging (MRI), including DWI on a 3T scanner, were identified retrospectively. Apparent diffusion coefficient (ADC) values of insulinomas and the surrounding pancreatic parenchyma were compared using a Wilcoxon signed-rank test. Receiver operating characteristic analysis was used to compare the diagnostic accuracy of four randomized image sets [T2-weighted image (WI), axial T1WI, DWI and T2WI + DWI] for each reader. Axial T1-weighted MRI exhibited the highest relative sensitivity for each reader; DWI alone exhibited the lowest relative sensitivity and the lower inter-reader agreement. There was no significant difference in lesion detection between T2WI and T2WI + DWI image sets for each reader. The ADC values of the insulinoma were significantly lower compared with those of the surrounding parenchyma. In conclusion, DWI does not benefit the detection of homogenous isoattenuating insulinoma. Axial T1WI is the optimal pulse sequence. Quantitative assessment of the tumor ADC values may be a useful tool to characterize identified pancreatic neoplasms.

Hypervascular pancreatic "lesions": a pattern-based approach to differentiation

Hypervascular pancreatic lesions/masses can arise due to a variety of causes, both benign and malignant, leading to a wide differential diagnosis. Accurate differentiation of these lesions into appropriate diagnoses can be challenging; however, this is important for directing clinical management. This manuscript provides a multimodality imaging review of hypervascular pancreatic lesion, with emphasis on an imaging-based algorithmic approach for differentiation of these lesions, which may serve as a decision support tool when encountering these uncommon lesions. Additionally, we stratify these lesions into three categories based on malignant potential, to help guide clinical management.

Preoperative imaging and pathologic classification for pancreatic neuroendocrine tumors

The management of patients with pancreatic neuroendocrine tumor (PNET), whether hormonally secretory or not, is multidisciplinary and often multimodal. Surgical treatment plays a central role because complete resection is the only potentially curative treatment. The choice of the therapeutic plan for a PNET requires precise localization of the primary tumor (which may sometimes be multiple in case of genetic predisposition), confirmation of the diagnosis of PNET, a search for metastases (mainly hepatic), and identification of the main histoprognostic factors. This update focuses on the WHO 2017 histological classification and recent innovations in the preoperative assessment of PNET using conventional and isotopic imaging. The aim is to not only allow the mapping of primary and metastatic lesions but also to predict tumor aggressiveness.

The Value of Hybrid Angio-CT in Preoperative Detection and Localization of Insulinomas: A Single-Center Retrospective Study

OBJECTIVE

To investigate the performance of hybrid angio-CT in preoperative detection and localization for insulinomas.

METHODS

Fifty-four postoperative pathology-confirmed patients from April 2015 to March 2017 were retrospectively reviewed; all patients underwent angio-CT with administration of contrast media in SMA, GDA and SA due to negative, inconclusive or controversial findings by several preoperative diagnostic methods including TAUS, CEUS, EUS, ECT, EMRI and DSA. Surgery was used as gold standard for localization of insulinomas; detection sensitivity and localization accuracy of angio-CT were assessed and compared with other preoperative image options.

RESULTS

Fifty-six benign insulinomas (mean diameter, 15.8 mm) in 54 patients (18 men and 36 women) were found according to surgical results; the overall detection sensitivity of TAUS, CEUS, EUS, ECT, EMRI and DSA was 21.4, 78.4, 79.2, 70.0, 79.2 and 72.2%, respectively. The overall localization accuracy was 14.3, 58.8, 68.8, 60.0, 75.0 and 44.4%, respectively. A total of 53 tumors were detected by angio-CT, 51 tumors were accurately located, and the overall detection sensitivity and localization accuracy of angio-CT was 94.4 and 90.7%, which was significantly higher than that of all other preoperative diagnostic methods (p < 0.05). No any serious complications occurred during angio-CT.

CONCLUSION

Our study indicates the great potential value of angio-CT in the preoperative detection and localization of insulinomas; angio-CT can be used as a preferred invasive diagnostic method.