A novel perfusion imaging technique of the pancreas: contrast-enhanced harmonic EUS (with video).

BACKGROUND: Contrast-enhanced harmonic-imaging techniques have been unavailable for EUS because of the limited frequency bandwidth and acoustic power output of current echoendoscopes. OBJECTIVE: To investigate the contrast harmonic imaging technique by using a prototype echoendoscope equipped with an adequate broad-band transducer that can detect harmonic signals from the US contrast agents. DESIGN: Identification of optimal settings (study I) and preliminary clinical investigations (study II). SETTING: Bethesda General Hospital Bergedorf. PATIENTS: A total of 104 patients undergoing standard EUS examinations. INTERVENTIONS: Contrast-enhanced harmonic EUS (CEH-EUS) was performed by using a prototype echoendoscope and extended pure harmonic detection mode, a specific mode for contrast harmonic imaging. MAIN OUTCOME MEASUREMENTS: In study I, time-intensity curves for peak signal intensity were calculated after infusion of a contrast agent, SonoVue, and the changes in echo intensity were compared for different mechanical indices and interval times. In study II, intermittent and real-time continuous images of pancreatobiliary and gastroduodenal diseases obtained by CEH-EUS were evaluated in comparison with contrast-enhanced power-Doppler EUS (CED-EUS). RESULTS: In study I, with the optimal mechanical index (0.4), homogeneous parenchymal perfusion images of the pancreas were obtained by intermittent imaging, and finely branching vessels of the pancreas were obtained with real-time continuous imaging. In study II, apparent perfusion and vessel images were observed in pancreatobiliary carcinomas, GI stromal tumors, and lymph-node metastases. CED-EUS failed to depict images of the fine vessels and parenchymal perfusion. LIMITATIONS: The subjective nature of the findings, with a limited number of patients. CONCLUSIONS: CEH-EUS successfully visualized parenchymal perfusion and microvasculature in the pancreas and may play an important role in the differential diagnosis of digestive diseases.

Preliminary study of contrast-enhanced harmonic endosonography with second-generation contrast agents.

PURPOSE: We developed a novel echoendoscope that enables contrast harmonic imaging using ultrasound contrast agents and performed contrast-enhanced harmonic endosonography (EUS) both in vitro and in vivo. METHODS: An experimental convex-array echoendoscope equipped with a wideband transducer and a specific mode for contrast harmonic imaging was used. A Doppler phantom model was employed in in vitro experiments to determine the optimal mechanical indices for contrast harmonic imaging by the echoendoscope. In the in vivo experiments, the echoendoscope was inserted into the stomachs of dogs. The digestive organs were observed after intravenous infusion of a contrast agent, Definity, using contrast-enhanced harmonic EUS. Two patients, one with pancreatic carcinoma and one with a gastrointestinal stromal tumor (GIST), underwent contrast-enhanced harmonic EUS. RESULTS: In vitro experiments revealed that the optimal mechanical indices were 0.35-0.40 for intermittent imaging and 0.30 or less for real-time imaging. In the in vivo experiments, branching vessels and subsequent homogeneous distribution of the signal in the pancreatic tissue were observed. During clinical application, typical vascular patterns were observed in pancreatic carcinoma and a GIST. CONCLUSION: Contrast-enhanced harmonic EUS visualized parenchymal perfusion and the fine vascular structure in digestive organs and should be a useful and powerful method for clinical investigations.

The cholecystokinin2-receptor mediates calcitonin secretion, gene expression, and proliferation in the human medullary thyroid carcinoma cell line, TT.

Gastrin-induced release of calcitonin from medullary thyroid carcinomas (MTC) is based on the expression of the cholecystokinin(2)-receptor (CCK(2)R) in these tumors. Recently, we have shown that the CCK(2)R is expressed not only in MTC but also in C-cells within the normal thyroid gland. The functions of the CCK(2)R in MTC and C-cells are largely unknown. We therefore explored the effects of gastrin-induced CCK(2)R stimulation in the highly differentiated MTC cell line, TT. CCK(2)R expression in TT-cells is detectable by RT-PCR as well as immunocytochemistry. Stimulation of the CCK(2)R by gastrin induces immediate release of calcitonin from TT-cells. Moreover, quantitative (LightCycler) RT-PCR demonstrates that gastrin stimulates transcription of the calcitonin and chromogranin A genes in TT-cells. TT-cell proliferation, assessed by counting of viable cells and (3)H-thymidine uptake, is markedly increased by gastrin. This effect is inhibited by the CCK(2)R-specific antagonist L-365,260. Our findings suggest physiological functions for the CCK(2)R in calcitonin-secretion and gene expression as well as a pathophysiological role in MTC proliferation. CCK(2)R antagonists might have therapeutic potential in these tumors.

Expression of the cholecystokinin 2-receptor in normal human thyroid gland and medullary thyroid carcinoma.

OBJECTIVE: The cholecystokinin(2)-receptor (CCK(2)R) promotes secretion and cell growth induced by its ligands cholecystokinin (CCK) and gastrin. The receptor has recently been shown to be expressed in human medullary thyroid carcinomas (MTCs). The objective of this study was to analyze CCK(2)R expression in MTC samples of different tumor stages as well as in non-malignant thyroid tissues. DESIGN AND METHODS: Using RT-PCR we investigated 19 MTC samples and TT-cells (a human MTC cell line), as well as samples of normal thyroid. In addition, we performed immunohistochemistry using calcitonin- and CCK(2)R-specific antibodies on MTCs and samples of C-cell hyperplasia. RESULTS: We demonstrate for the first time that CCK(2)R is expressed not only in MTCs but in all samples of normal thyroid tissue. Using immunohistochemistry the receptor could be localized on calcitonin-secreting C-cells. The highest incidence of CCK(2)R expression in MTCs was observed in early-tumor stages, whereas CCK(2)R could not be detected in advanced or metastasized tumors. CONCLUSIONS: The expression of CCK(2)R in C-cells suggests a physiological function for gastrin and/or CCK in the regulation of calcitonin release, presumably related to bone and calcium metabolism. Moreover, these ligands might act as growth factors in MTCs. Efforts in the development of CCK(2)R scintigraphy for the detection of MTC lesions might have to consider a lower incidence of the receptor in advanced tumor stages.

Gastrin releasing peptide-preferring bombesin receptors mediate growth of human renal cell carcinoma.

Bombesin-like peptides typically act as neurotransmitters along the brain-gut axis and as growth factors in various human tissues. The present study demonstrates the expression of gastrin releasing peptide (GRP)-preferring bombesin receptors in human renal cell carcinoma but not in normal kidney tissue. The expression of GRP receptors was characterized at the mRNA level by reverse transcription-PCR, as well as at the protein level by binding of (125)I-[Tyr(4)] bombesin to membranes prepared from tumor tissue (K(d) 0.3 nM) and healthy kidney tissue from the same four patients. GRP receptors were also demonstrated in four human kidney carcinoma cell lines (A-498, CAKI-1, CAKI-2, and ACHN). The effects of bombesin/GRP agonists and/or antagonists on growth were investigated in vitro on CAKI-2 cells, which expressed large amounts of GRP receptors. Cell numbers stimulated by 10% fetal calf serum were significantly stimulated by interleukin-1beta (control) and GRP-7 (10(-7) M), both in the range of 136 to 148%; addition of the GRP receptor antagonist acetyl-GRP(20-27) (10(-6) M) completely reversed this effect. Bombesin alone (10(-6) M) significantly stimulated CAKI-2 cells (129%) cultured with 0.5% fetal calf serum, whereas another antagonist, D-Phe6,Leu13,(CH2NH)Leu14 bombesin(6-14) (1 microM), alone did not inhibit growth, thus excluding an autocrine mechanism. These results indicate for the first time that malignant transformation of human kidney tissue into renal cell carcinoma is accompanied by novel expression of GRP receptors. Bombesin-like peptides might act as mitogens in these carcinomas, and they might be useful as diagnostic or therapeutic tools such as tumor imaging or internal radiotherapy.