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Clinical problem Colorectal metastases are the most common malignant liver lesions. Imaging of the liver in patients with colorectal carcinoma is performed for early detection of liver metastases (CRLM) at the time of initial tumor diagnosis, for monitoring and follow-up in order to exclude or diagnose metachronous metastases. Standard radiological methods Radiological imaging includes primarily multislice computed tomography (CT) and magnetic resonance imaging (MRI), which play an important role regarding therapeutic management and assessment of prognosis. Performance, achievements Contrast-enhanced CT is broadly available and allows for rapid image acquisition including the possibility for complete tumor staging. MRI, on the other hand, is characterized by very good soft tissue contrast and has-especially with the use of diffusion-weighted imaging and administration of liver-specific contrast agents-the highest sensitivity for detection of metastases smaller than 1 cm. Practical recommendations The choice of imaging in daily routine is often dependent on availability and clinical question. Frequently, e.g. for assessment of resectability (extent of metastases, anatomic relation of lesions to critical structures), both modalities may be implemented in combination.

To assess the accuracy and applicability of an electromagnetic navigation system (EMNS) for CT-guided microwave ablation (MWA) of hepatic tumors in comparison with conventional CT-guidance.34 patients (m = 20/f = 14, mean age 34 y) with 34 liver tumors (primary = 22, metastases = 14, mean size 20 mm) referred for CT-guided MWA were included in this IRB-approved study. Interventions were performed prospectively using an EMNS in 17 patients (navigation group), and results were compared to a matched historic cohort of 17 patients using conventional CT-guidance (control group, t-test, p 0.05 deemed significant). Primary outcome measurement: accuracy of antenna placement (deviation). Secondary outcome measurements: setup time, number of control scans, duration and radiation exposure for antenna placement.Ablations were performed using a single or a double-angulated approach. Application of the EMNS was feasible in 14 cases (82%). Mean total deviation of the antenna feed point in the navigation and control group was 2.4 mm (range 0.2-4.8 mm) and 3.9 mm (range 0.4-7.8 mm), p 0.05. Mean setup time for the EMNS was 6.75 ± 3.9 min (range 3-12 min). Mean number of control scans in the navigation and control group was 3 ± 0.9 (range 1-4) and 6 ± 1.3 (range 4-8), p 0.0001; mean time for antenna placement was 9 ± 7.3 min (range 1.4-25.9 min) and 11.45 ± 6.1 min (range 3.9-27.4 min), p = 0.3164. Radiation exposure was significantly less in the navigation group.Our experience in a limited number of patients suggests that EMNS enables intuitive CT-guided MWA of liver tumors with higher accuracy when compared to ablations performed without navigation and with fewer control scans needed.

Colorectal metastases are the most common malignant liver lesions. Imaging of the liver in patients with colorectal carcinoma is performed for early detection of liver metastases (CRLM) at the time of initial tumor diagnosis, for monitoring and follow-up in order to exclude or diagnose metachronous metastases.Radiological imaging includes primarily multislice computed tomography (CT) and magnetic resonance imaging (MRI), which play an important role regarding therapeutic management and assessment of prognosis.Contrast-enhanced CT is broadly available and allows for rapid image acquisition including the possibility for complete tumor staging. MRI, on the other hand, is characterized by very good soft tissue contrast and has-especially with the use of diffusion-weighted imaging and administration of liver-specific contrast agents-the highest sensitivity for detection of metastases smaller than 1 cm.The choice of imaging in daily routine is often dependent on availability and clinical question. Frequently, e.g. for assessment of resectability (extent of metastases, anatomic relation of lesions to critical structures), both modalities may be implemented in combination.