Value of Contrast Enhanced Intraoperative Ultrasound Compared to Preoperative CEUS, CT and MRT in the Treatment of Colorectal Liver Metastases.

1. Introduction: The surgical resection of colorectal liver metastases is the only curative therapy for those patients (1). Because a major part of those patients become diagnosed in a technical irresectable stadium, most patients primary get a chemotherapy to reach a secondary resection (2). Especially for this group of patients an effective preoperative staging is necessary to know the exact number and location of the liver metastases. Standard imaging is abdominal CT with a contrast medium, lately it is also possible to create a 3D analysis based on vasculatory territories out of the 2D data (3) (4). Alternatively MRI imaging can be used as well, but because of its defiency in the imaging of vascular anatomy it is only partly suited for the surgical planning and resection. By now the contrast enhanced sonography has been further developed and can be used for dignity evaluation of leasions. Depending on the examiner it can provide very useful informations (5). Because of the intraoperative ultrasound is the most sensitive and specific diagnosic procedure (6), the intraoperative use of contrast medium ultrasound seems to suggest itself. As the necessary ultrasonic probes weren't avaiable until now, only a few experiences have been made yet (7).

Aim of the study is to compare the value of all described methods considering the detection rate of colorectal metastases, including the by now available intraoperative cm-ultrasound. From the comparison of all modern methods (64-line doublehelix CT, 3D virtual operation planning, 3 tesla Primovist-MRI, pre- and intraoperative contrast enhanced sonography) we aim to get a reliable recommendation for the preoperative necessary staging.

1. Background: state of research/ scientific arguementation/ leading question In the last 20 years, the surgery of colorectal liver metastases has developed a lot (8,9,10,11). In centers even complex surgeries can be done with a mortality of 0,1% and with a morbidity of 15%. Today, neither the number, nor the localisation of metastases or an extrahepatic tumour growth is decisive for a resection, but the fact, if there is a possibilty for a complete tumor excision (12). Especially because of the further developement of neoadjuvant (13) and adjuvant (14) chemotherapeutics on the one hand and the technical developement (portal embolisation (15), two-time resection (16), virtual operation planning (4), navigated surgery (17)) on the other hand enlarged the number of patients becoming resectable secondarily.

The demand on preoperative imaging increased with the technical and therapeutical developements. In surgical and technical prospect the abdomen CT imaging is still standard in surgery planning, because besides the tumor imaging, the good vascular anatomy imaging enables a surgical strategy (5). Today, 2D CT data can be used to create a 3D imaging of the liver and its vascularisation to plan a virtual surgery beneffiting especially the most complex surgeries (18). Because of the distinct better resolution of a lesion, MRI imaging of the liver has a high significance in literature and allows radiologists a higher quality of their diagnosis (19), but does not obligatory ease the surgery planning for the surgeon (20). A comparing study in a surgeons point of view could show a equal validity of both modalities (21). Interestingly, the mentionend studies showed that the detection of metastases in altered liver tissue (fatty degeneration/ status post chemotherapy) is reduced. In these difficult cases the CE-sonography gives the decisive informations (22). The practical disadvantage is the dependence on the examiner.

Intraoperative sonography is the gold standard procedure during the operation, additional leasions can be detected which may change the resection strategy (6). Even if there are only a few experiences with intraoperative ultrasonic probes that are able to do contrast enhancment, we assume an advantage of the use of contrast medium sonography (23) in the operation room. The yet published data is not enough for a ensured evidence.