Saline-Enhanced Hepatic Radiofrequency Ablation Using a Perfused-Cooled Electrode: Comparison of Dual Probe Bipolar Mode with Monopolar and Single Probe Bipolar Modes

OBJECTIVE: To determine whether saline-enhanced dual probe bipolar radiofrequency ablation (RFA) using perfused-cooled electrodes shows better in-vitro efficiency than monopolar or single probe bipolar RFA in creating larger coagulation necrosis. MATERIALS AND METHODS: RF was applied to excised bovine livers in both bipolar and monopolar modes using a 200W generator (CC-3; Radionics) and the perfused-cooled electrodes for 10 mins. After placing single or double perfused-cooled electrodes in the explanted liver, 30 ablation zones were created at three different regimens: group A; saline-enhanced monopolar RFA, group B; saline-enhanced single probe bipolar RFA, and group C; saline-enhanced dual probe bipolar RFA. During RFA, we measured the tissue temperature at 15 mm from the electrode. The dimensions of the ablation zones and changes in the impedance currents and liver temperature during RFA were then compared between the groups. RESULTS: The mean current values were higher for monopolar mode (group A) than for the bipolar modes (groups B and C) : 1550+/-25 mA in group A, 764+/-189 mA in group B and 819+/-98 mA in group C (p 0.05). The temperature at 15 mm from the electrode was higher in group C than in the other groups: 70+/-18 degrees C in group A, 59+/-23 degrees C in group B and 96+/-16 degrees C in group C (p < 0.05). CONCLUSION: Saline-enhanced bipolar RFA using dual perfused-cooled electrodes increases the dimension of the ablation zone more efficiently than monopolar RFA or single probe bipolar RFA.

Optimization of Wet Radiofrequency Ablation Using a Perfused-Cooled Electrode: A Comparative Study in Ex Vivo Bovine Livers

OBJECTIVE: To determine the optimized protocol for wet monopolar radiofrequency ablation (RFA) using a perfused-cooled electrode to induce coagulation necrosis in the ex vivo bovine liver. MATER AND METHODS: Radiofrequency was applied to excised bovine livers in a monopolar mode using a 200W generator with an internally cooled electrode (groups A and B) or a perfused-cooled electrode (groups C, D, E, and F) at maximum power (150-200 W) for 10 minutes. A total of 60 ablation zones were created with six different regimens: group A - dry RFA using intra-electrode cooling; group B - dry RFA using intra-electrode cooling and a pulsing algorithm; group C - wet RFA using only interstitial hypertonic saline (HS) infusion; group D - wet RFA using interstitial HS infusion and a pulsing algorithm; group E - wet RFA using interstitial HS infusion and intra-electrode cooling; and group F - wet RFA using interstitial HS infusion, intra-electrode cooling and a pulsing algorithm. In groups C, D, E, and F, RFA was performed with the infusion of 6% HS through the perfused cooled electrode at a rate of 2 mL/minute. During RFA, we measured the tissue temperature at a distance of 15 mm from the electrode. The dimensions of the ablation zones and the changes in impedance, currents, and liver temperature during RFA were compared between these six groups. RESULTS: During RFA, the mean tissue impedances in groups A (243+/-88 omega) and C (252.5+/-108 omega) were significantly higher than those in groups B (85+/-18.7 omega), D (108.2+/-85 omega), E (70.0+/-16.3 omega), and F (66.5+/-7 omega) (p < 0.05). The mean currents in groups E and F were significantly higher than those in groups B and D, which were significantly higher than those in groups A and C (p < 0.05) : 520+/-425 mA in group A, 1163+/-34 mA in group B, 652.5+/-418 mA in group C, 842.5+/-773 mA in group D, 1665+/-295 mA in group E, and 1830+/-109 mA in group F. The mean volumes of the ablation regions in groups E and F were significantly larger than those in the other groups (p < 0.05) : 17.7+/-5.6 cm3 in group A, 34.5+/-3.0 cm3 in group B, 20.2+/-15.6 cm3 in group C, 36.1+/-19.5 cm3 in group D, 68.1+/-12.4 cm3 in group E, and 79.5+/-31 cm3 in group F. The final tissue temperatures at a distance of 15 mm from the electrode were higher in groups E and F than those in groups A, C, and D (p < 0.05) : 50+/-7.5 degreesC in group A, 66+/-13.6 degreesC in group B, 60+/-13.4 degreesC in group C, 61+/-12.7 degreesC in group D, 78+/-14.2 degreesC in group E, and 79+/-12.0 degreesC in group F. CONCLUSION: Wet monopolar RFA, using intra-electrode cooling and interstitial saline infusion, showed better performance in creating a large ablation zone than either dry RFA or wet RFA without intra-electrode cooling.

Radiologic Assessment of Spinal CSF Leakage in Spontaneous Intracranial Hypotension

PURPOSE: To assess the usefulness of imaging modalities in the detection of spinal CSF leakage in spontaneous intracranial hypotension. MATERIALS AND METHODS: Fifteen patients who complained of postural headache without any preceding cause showed typical brain MR findings of intracranial hypotension, including radiologically confirmed CSF leakage. All fifteen underwent brain MRI and radionuclide cisternography. CT myelography was performed in eight patients and spinal MRI in six. Medical records, imaging findings and the incidence of spinal CSF leakage during each modality were retrospectively reviewed. RESULTS: CSF leakage was most common at the cervicothoracic junction, where in seven of 15 cases it was seen on radionuclide cisternography as increased focal paraspinal activity. Leakage was noted at the mid-thoracic level in three patients, at the upper thoracic level in two, and at the cervical and lumbar levels in the remaining two. In two patients multiple CSF leaks were noted, and in all, early radioactive accumulation in the bladder was visualized. CT myelography revealed extrathecal and paraspinal contrast leakage in three of eight patients, and among those who underwent spinal MRI, dural enhancement was observed at the site of CSF leakage in all six, abnormal CSF signal in the neural foramen in one, and epidural CSF collection in one. CONCLUSION: Radionuclide cisternography is a useful method for the detection of CSF leakage in spontaneous intracranial hypotension. CT myelography and spinal MRI help determine the precise location of leakage.

Detectability of the Mediastinal Lines: Comparison of Conventional Film-Screen Radiography and DigitalRadiography

PURPOSE: Using dynamic range compression (DRC) processing, this study compared the detectability ofmediastinal lines by conventional film screen rediography (FS) and by storage phosphor digital radiography(DR). MATERIALS AND METHODS: We selected 200 normal consecutive chest radiographs (100 FS, 100 DR) ; dynamic rangecompression was applied to DR processing and moving grids were used in both systems. Seven mediastinal lines (leftfaraspinal, right paraspinal, azygoesophageal, left para-aortic, posterior junctional, anterior junctional andright paratracheal) were scored from 0 point to 3 point(0:not visible, 1:suspiciously visible, 2:visible, but notclear, 3: clearly visible) according to visibility and sharpness, as agreed by a radiologist and a resident. Thedifferences between the two modalities were compared and analyzed by chi-square test. RESULTS: Among the 1400mediastinal lines analyzed, 419 lines by DR(59.9%) and 232 lines by FS(33.1%) were scored more than 2 points. Inall mediastinal lines except the left para-aortic, DR was more detectable and clearer than FS, with statisticalsignificance(P<.01). CONCLUSION: DR processed with DRC visualizes mediastinal lines more frequently and clearlythan conventional FS, and is therefore thought to be useful for the evaluation of mediastinal diseases.