Simultaneous RF application to a cluster of three closely spaced internally cooled electrodes enables a larger volume of coagulation in ex vivo liver, in vivo tissues, and hepatic colorectal metastases than previously reported.

In a retrospective study of adrenal masses evaluated with computed tomography (CT), lesion x-ray attenuation was compared with size and radiologists' interpretations in discriminating benign lesions from malignant ones. Unenhanced CT attenuation coefficient and size were analyzed electronically in 55 patients with 66 adrenal masses. There were 38 nonhyperfunctioning adenomas in 33 patients and 28 malignant masses in 22 patients. Primary extraadrenal malignancies were present in 45 of the 55 patients. Three blinded readers characterized the adrenal masses using a seven-point scale of certainty. Results were subjected to receiver operating characteristic (ROC) analysis. The mean CT attenuation coefficient for benign adrenal masses was -2.2 HU +/- 16.0 and was significantly different from the mean for malignant lesions (28.9 HU +/- 10.6). The area under the ROC curve for CT attenuation coefficients (0.91 +/- 0.04) was significantly larger than that for lesion size (0.84 +/- 0.05) or best observer interpretation (0.84 +/- 0.05). A threshold CT attenuation value of 0 HU had a sensitivity-to-specificity ratio of 47%:100% for characterizing benign adrenal masses, whereas a threshold attenuation of 10 HU had a ratio of 79%:96%.

The coagulation necrosis achieved for a standardized RF application correlates with relative tissue perfusion. Pharmacologic reduction of blood flow during thermally mediated percutaneous ablation may induce greater coagulation necrosis.

No abstract

Superparamagnetic iron oxide (AMI-25), a reticuloendothelial cell-specific contrast agent for magnetic resonance (MR) imaging, was evaluated for its ability to permit detection of splenic metastases in 18 patients. Superparamagnetic iron oxide, at a dose of 30 mumol of iron per kilogram, decreased the signal intensity of spleen from 19.5 +/- 4.8 to 3.1 +/- 2.2 (spin-echo sequence, repetition time msec/echo time msec = 1,500/42; P less than .05), without changing the signal intensity of tumor. As a result, the tumor-spleen contrast-to-noise ratio increased from 0.2 (tumor isointense relative to spleen) to 18.0 (tumor hyperintense relative to spleen). As a consequence of increased contrast, splenic tumors were detected in four of 18 patients (45 individual lesions; P less than .05), whereas nonenhanced MR imaging permitted detection of splenic lesions in only two of 18 patients (four individual lesions). Maximum tumor-spleen contrast was achieved within 60 minutes after intravenous administration. These initial clinical results indicate that MR imaging with superparamagnetic iron oxide may offer improved accuracy in the diagnosis of splenic tumors.