COMPARISON OF B-MODE, TISSUE HARMONIC IMAGING AND CONTRAST ENHANCED LOW MECHANICAL INDEX ULTRASOUND IN PANCREATIC LESIONS

Problemstellung: The aim of the study was to evaluate the diagnostic sensitivity, specificity and imaging quality of conventional B-mode US, tissue enhanced imaging (TEI) and contrast enhanced low MI Real Time Ultrasound (Cn-Ti) plus SonoVue® (Bracco) for the evaluation of pancreatic lesions.

Methoden: In a prospective study, 35 patients with known pancreatic lesions underwent an US examination of the pancreas in B-mode, TEI and contrast enhanced US. Contrast enhanced CTs or histological examinations were obtained from all patients as diagnostic references. The US examinations were performed using the Esaote Technos MPX (Italy). The whole examination was blinded regarding the patients' data. The analysis was then done by way of filming on digital video. Two independent radiologists evaluated the imaging material in terms of imaging quality, lesion type, lesion size and vascular infiltration. The portal vein, the superior mesenteric vein, the superior mesenteric artery, and the splenic vein were evaluated for vascular infiltration.

Ergebnisse: In 35 patients a total of 40 pancreatic lesions (23 adeno-carcinomas, 1 carcinoid, 1 kystadenoma, 3 lymphomas, 2 metastases of other carcinomas, 6 cysts, 3 cases of acute pancreatitis, 1 chronic pancreatitis) were diagnosed by CT. A histological correlation was performed in 26 lesions (17 adeno-carcinomas, 3 lymphomas, 2 metastases, 1 carcinoid, 2 acute pancreatitises and 1 chronic pancreatitis). All other lesions were classified by a CT follow-up examination.

Regarding the differentiation between a benign or malignant process, the comparison between B-mode, TEI and contrast enhanced low MI Real Time US and the diagnostic reference showed sensitivities of 75.8% vs. 80.7% vs. 90.3% respectively, and specificities of 85% vs. 90% vs. 95% respectively. The evaluation of vascular infiltration showed a significantly better sensitivity for contrast enhanced examination than for B-mode and TEI examination (88.1% vs. 45.2% vs. 61.9% respectively; Cn-Ti vs. TEI p=0.042, Cn-Ti vs. B-Mode: p<0.001). Consequently contrast enhanced US is significantly better in terms of the correct diagnosis of operability than the other modalities.

Imaging quality of TEI significantly exceeds the imaging quality of Cn-Ti (p=0.046).

Schlussfolgerungen: Contrast enhanced US is significantly better than B-mode or tissue enhanced imaging in the preoperative staging of pancreatic lesions regarding vascular infiltration. There is no benefit in the differentiation between lesion types. Contrast enhanced US has to be combined with other imaging modalities like TEI because of the significantly worse image quality of Cn-Ti imaging on its own.