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

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.

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

PURPOSE

To evaluate the diagnostic performance of biphasic contrast-enhanced CT (CECT), volume perfusion CT (VPCT) and 3 Tesla MRI with diffusion-weighted imaging (DWI), in patients with clinically suspected insulinomas.

MATERIALS AND METHODS

This prospective study was approved by the institutional review board. Sixty-four patients with clinically suspected insulinomas underwent biphasic CECT, VPCT, and 3T MR with DWI. Two radiologists independently determined the presence/absence of tumor using a 5-scale confidence level. Conspicuity of the lesion and clarity of tumor-to-pancreatic duct distance were graded. Receiver operating characteristic analysis was performed to compare diagnostic performance.

RESULTS

Forty-seven patients were tumor positive, with 51 tumors. The differences between the areas under the curve values for tumor detection were as follows: 0.715 (CECT), 0.903 (VPCT), 0.832 (MRI without DWI) and 0.955 (MRI with DWI) for reader 1, and 0.738 (CECT), 0.895 (VPCT), 0.841 (MRI without DWI), and 0.956 (MRI with DWI) for reader 2. MRI with DWI and VPCT were significantly more accurate than CECT for insulinoma detection (P = 0.01 and 0.02 for reader 1, and P = 0.01 and 0.03 for reader 2). Lesion conspicuity was better on MRI compared with VPCT (P = 0.01), and both were better than CECT (both P < 0.01). Tumor-to-pancreatic duct distance was better appreciated on MRI, compared with CECT and VPCT (both P < 0.01). The weighted k values indicate good to excellent agreement between observers for determining tumor presence/absence (k = 0.64-0.84).

CONCLUSION

The 3T MRI with DWI and VPCT are significantly more accurate than CECT for insulinoma detection. MRI demonstrates higher tumor conspicuity and is superior in depicting the tumor-to-duct distance.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1648-1655.

Isoattenuating insulinomas at biphasic contrast-enhanced CT: frequency, clinicopathologic features and perfusion characteristics

OBJECTIVES

We aimed to determine the frequency of isoattenuating insulinomas, to investigate their clinicopathological features and to assess their regional pancreatic perfusion characteristics.

METHODS

Institutional review board approval was obtained, and patient informed consent was waived. From July 2010 to June 2014, 170 patients (66 male, 104 female) with endogenous hyperinsulinemic hypoglycemia underwent biphasic contrast-enhanced CT before surgery, and 129 of those patients also received preoperative whole-pancreas CT perfusion. A total of 181 tumours were proved histopathologically after surgery. Enhancement pattern and regional pancreatic perfusion characteristics were analyzed. Clinical features, tumour size and pathological grading were investigated.

RESULTS

The frequency of isoattenuating tumours was 24.9 %. Tumour size and WHO grading was not significantly different between isoattenuating and hyperattenuating tumours. Tumour-free regions had identical blood flow (BF) regardless of their location (p = 0.35). Isoattenuating tumour-harbouring regions had lower BF compared with hyperattenuating tumour-harbouring regions; both showed higher BF compared with tumour-free neighbourhood regions (all p < 0.01). For patients with isoattenuating tumours, the overall hospital stay was longer (p < 0.01).

CONCLUSIONS

A substantial subset of insulinomas were isoattenuating on biphasic CT. CT perfusion showed higher BF in tumour-harbouring regions compared to tumour-free regions, providing a clue for tumour regionalization.

KEY POINTS

• About a quarter of all insulinomas were isoattenuating on biphasic contrast-enhanced CT. • CT perfusion finds tumour-harbouring regions have higher blood-flow compared to tumour-free regions. • CT perfusion provides important information for tumour regionalization, for isoattenuating tumours.

Imaging in multiple endocrine neoplasia type 1: recent studies show enhanced sensitivities but increased controversies

In multiple endocrine neoplasia type 1 (MEN1) patients, a number of recent studies compare the ability of different, new imaging modalities to existing modalities to localize the important neuroendocrine tumors (NETs) that contribute to their decreased life expectancy (pancreatic NETs [pNETs] and thymic carcinoids). These included the use of ⁶⁸Ga-DOTATOC-PET/CT, endoscopic ultrasound and MRI. The current paper analyzes these results in light of current guidelines and controversies involved in the treatment/management of MEN1 patients. Particular attention is paid to results in these studies with thymic carcinoids and nonfunctional pNETs/gastrinomas, which recent studies show are particularly important in determining long-term survival. These studies show a number of promising imaging results but also raise a number of controversies, which will need to be addressed both in their use initially and for serial studies in these patients.

Laparoscopic resection of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are a rare heterogeneous group of endocrine neoplasms. Surgery remains the best curative option for this type of tumor. Over the past two decades, with the development of laparoscopic pancreatic surgery, an increasingly larger number of PNET resections are being performed by these minimally-invasive techniques. In this review article, the various laparoscopic surgical options for the excision of PNETs are discussed. In addition, a summary of the literature describing the outcome of these treatment modalities is presented.

Preoperative assessment of the pancreas in multiple endocrine neoplasia type 1

BACKGROUND

Many serologic and radiographic modalities are used for monitoring multiple endocrine neoplasia type 1 (MEN 1) patients for pancreaticoduodenal neuroendocrine tumors (PNETs). We compared serum markers and imaging studies obtained preoperatively with the gross pathology and immunohistochemical findings and correlated preoperative testing with postoperative outcome.

METHODS

From 2000 to 2008, 52 MEN 1 patients [32 (62%) female; median age = 43 years, range 19-74 years] underwent 56 pancreatic operations [49 (88%) distal pancreatectomies] for suspected PNETs. Preoperative serum markers [human pancreatic polypeptide (HPP), gastrin, and glucagon] and imaging [CT, (111)In pentetreotide scintigraphy, and endoscopic ultrasound (EUS)] were compared to the pathologic findings. Postoperative serum markers and survival were followed.

RESULTS

Human pancreatic polypeptide had the highest agreement between an elevated serum level and positive tumor immunostaining (83% vs. 50% agreement for gastrin vs. 67% agreement for glucagon). Preoperative CT had 81% sensitivity and positive predictive value (PPV) of 97% for PNETs. (111)In pentetreotide scintigraphy had 84% sensitivity and PPV of 96%. Preoperative endoscopic ultrasonography (EUS) had 100% sensitivity and PPV, with close correlation (r (s) = 0.93) between the largest lesion seen on EUS and pathology. Median follow-up was 4.3 years (range = 0.1-10.9 years). Overall survival was 89% at 5-year follow-up.

CONCLUSIONS

Our study substantiates EUS as providing the highest preoperative sensitivity and PPV in assessing the presence of PNETs in MEN 1 patients. CT and octreotide scintigraphy can yield both false-positive and false-negative results. HPP, gastrin, and glucagon were the most commonly measured tumor markers in our series but did not always correlate with immunostaining. With an aggressive surgical approach, satisfactory rates of biochemical improvement and long-term survival were observed.