R Hammerstingl

PURPOSE: To evaluate magnetic resonance (MR) imaging-guided laser-induced thermotherapy (LITT) of liver metastases. MATERIALS AND METHODS: In a phase II study, 20 patients with 33 metastases from colorectal carcinoma (75%) or other primary tumors (25%) underwent LITT. MR thermometry performed with fast low-angle shot sequences was used to monitor therapy on-line, and dynamic and static contrast material-enhanced MR images enabled estimation of the degree of resultant necrosis. Follow-up studies were performed 3 months after thermotherapy. RESULTS: The thermosequences enabled accurate on-line monitoring in 85% of lesions. In 69% of lesions 20 mm in diameter or smaller, contrast-enhanced MR images depicted substantial necrosis, with a local tumor control rate of 69% after 6 months and 44% after 12 months. Among lesions larger than 20 mm, necrosis was frequently incomplete, with a local control rate of only 41% after 6 months and 27% after 12 months. CONCLUSION: MR imaging-guided LITT of liver metastases is a safe and promising therapy for liver metastases.

PURPOSE: To assess AMI-25- versus gadolinium-enhanced magnetic resonance (MR) imaging in the differential diagnosis of liver tumors. MATERIALS AND METHODS: Twenty-nine patients with liver tumors underwent unenhanced, AMI-25-enhanced (15 micromol/kg), and gadolinium-enhanced(0.1 mmol/kg) imaging within 2 weeks. RESULTS: A significant (P< .05) difference in percentage signal intensity loss (PSIL) was seen in benign tumors on AMI-25-enhanced proton-density-weighted images (nine focal nodular hyperplasia [FNH], 41%; one adenoma, 32.4%) versus malignant tumors. Gadolinium-enhanced T1-weighted gradient-echo images showed strong enhancement in benign lesions (seven FNH, 147.5%; one adenoma, 91.3%) and moderate enhancement in malignant tumors (eight hepatocellular carcinomas, 116.2%, 11 metastases, 39.7%). Receiver operating characteristic analysis revealed a threshold PSIL of 10% on AMI-25-enhanced images as the most essential criteria to distinguish benign from malignant lesions (sensitivity, 88%; specificity. 89%). Interobserver analysis for two observers revealed specificity of 93% for AMI-25-enhanced imaging versus 81.5% for gadolinium-enhanced MR imaging. CONCLUSION: AMI-25 decreased the SI of benign tumors and helped differentiate benign from malignant tumors.

OBJECTIVE: Our objective was to evaluate the accuracy of contrast-enhanced transrectal MR imaging in staging rectal adenoma and carcinoma by correlating with histopathologic findings. SUBJECTS AND METHODS: Thirty-five patients underwent transrectal MR imaging on a 1.5-T superconducting unit using unenhanced T1-weighted and T2-weighted spin-echo and turbo spin-echo sequences, a dynamic gadopentetate dimeglumine-enhanced turbo fast low-angle shot sequence, and enhanced T1-weighted spin-echo sequences. For all patients, histopathologic correlation was available from biopsy (n = 15) or surgical resection (n = 20). Two radiologists unaware of each other's interpretations of the scans interpreted each case from which we evaluated qualitative and quantitative data. RESULTS: Rectal adenomas (n = 15) were identified when imaging revealed an intact muscularis mucosae, a homogeneous internal structure, and high contrast enhancement of the lesion. Carcinomas staged as T1 by TNM criteria (n = 6) were best revealed by dynamic turbo fast low-angle shot sequences, in which an intact muscularis propria could be seen. Visualization of enhancing tumor tissue in the muscularis propria indicated T2 carcinoma (n = 5). All T3 (n = 5) and T4 (n = 4) carcinomas were correctly staged with dynamic and static MR imaging. The stage revealed by MR imaging correlated well with histologic staging results in 89% (observer 1) and 86% (observer 2) of interpretations. However, when interpreting MR imaging, observers tended to overstage and never understaged. CONCLUSION: Transrectal surface-coil MR imaging provided reliable information in staging patients before surgery and in evaluating rectal adenoma and carcinoma.

RATIONALE AND OBJECTIVES: The authors assess the efficacy of static and dynamic magnetic resonance (MR) imaging using the superparamagnetic iron oxide SHU-555A (Resovist) versus standard dose of gadolinium (Gd)-DTPA in patients with focal liver lesions. METHODS: Magnetic resonance imaging was performed in 30 patients suffering from histopathologically verified malignant (n = 22) and benign (n = 8) liver lesions. T2-weighted conventional and fat-suppressed as well as T1-weighted sequences were used before, during, and after fast intravenous administration of Resovist (1 mL/minute) at three doses of 4, 8, and 16 mumol/kg body weight. One week before the Resovist-enhanced MR imaging study 20 patients underwent Gd-DTPA-enhanced MR imaging. RESULTS: Detection rate was improved for metastatic lesions revealing 36 lesions unenhanced versus 53 focal lesions using Resovist-enhanced MR imaging. Gadolinium-DTPA-enhanced scans showed no additional lesion versus unenhanced and Resovist-enhanced MR imaging. Static and dynamic imaging demonstrated no measurable percentage signal intensity loss (PSIL) using Resovist-enhanced MR imaging versus a percentage enhancement of 79.7% in Gd-DTPA enhanced scans. In the dynamic T2-weighted sequences, hepatocellular carcinoma nodules (n = 4) showed a rapid decrease in signal intensity starting at 44 seconds. Postinfusion of Resovist followed by a low, constant increase in signal intensity. Gadolinium-DTPA enhanced scans showed a percentage enhancement of 73.4 focal nodular hyperplasia (FNH) and hemangioma revealed a strong and early dose-dependent PSIL 44 to 60 seconds postinfusion with a prolonged signal loss for the FNH in the late study. Statistical evaluation revealed a statistically significant superiority of Resovist-enhanced MR imaging concerning the detection and delineation of focal liver lesions compared with unenhanced and Gd-DTPA enhanced scans (P < 0.05). CONCLUSIONS: The fast infusion of the new superparamagnetic contrast agent Resovist shows advantages for dynamic and static MR imaging of focal liver lesions.

PURPOSE: Demonstration of techniques and clinical value of imaging diagnostics for screening, detection, interventional follow-up and therapy control of hepatocellular carcinoma (HCC). Diagnostic techniques for screening, detection and differential diagnosis of HCC are presented using color-coded duplex sonography (US), computer tomography (CT) and contrast-enhanced magnetic resonance techniques like MRI, MR angiography and MR cholangiopancreaticography (MRCP). Therapy control with imaging was performed for surgical methods like resection and liver transplantation as for well as transarterial chemoembolization (TACE), radiofrequency ablation (RF) and laser-induced thermotherapy (LITT). In screening, HCC color-coded duplex sonography reveals a sensitivity from 45 to 92 % and a specificity from 78 to 90 % when liver cirrhosis is present. The diagnostic results of CT were further improved with the newly developed techniques of multislice CT. The highest diagnostic accuracy can currently be achieved using contrast-enhanced MRI with a sensitivity from 82 to 96 %. TACE presents a palliative therapy concept; MR-guided LITT and radiofrequency ablation are used as thermoablative methods for local therapy and the therapy control is based on the above imaging techniques. Contrast-enhanced MRI proves to be the superior imaging technique for the early diagnosis, differential diagnosis and follow-up of hepatocellular carcinoma.