John M. Brock

Hepatic ablation with use of radio-frequency electrocautery in the animal model.

The potential of percutaneous radio-frequency (RF) electrocautery hepatic ablation was evaluated in the animal model. RF hepatic ablation was performed under ultrasound (US) guidance in the liver of 10 swine with use of a specifically designed needle. The needle was placed through the liver capsule, and ablation was performed after isolating the liver at laparotomy. Animals were killed immediately (n = 4), at 1 week (n = 1), 2 weeks (n = 3), or at 5 weeks (n = 2). The US findings were correlated with the pathologic results in the animal livers. RF hepatic ablation was successfully performed in the animal model without complications. Lesions in the animal livers were typically 1 x 2 cm, which initially appeared highly echogenic on US scans. These images corresponded to an area of hepatic necrosis. The lesions became less echogenic shortly after initial treatment but could still be visualized with US at 5 weeks. At histologic study at 5 weeks, the treated livers showed central debris, a larger area of necrotic liver, and a zone of granulation tissue surrounded by a fibrotic capsule. No complications were encountered. RF hepatic ablation shows future promise in treatment of hepatic neoplasms.

Percutaneous ultrasound-guided radiofrequency electrocautery ablation of prostate tissue in dogs

RATIONALE AND OBJECTIVES We investigated the feasibility of percutaneous radiofrequency (RF) electrocautery in ablation of prostate tissue in dogs. METHODS We used six dogs in whom a specially designed needle was placed percutaneously into the prostate. RF electrocautery was applied to the needle and treatment was monitored with ultrasound. Animals were sacrificed and gross examination of the prostate and surrounding tissues was performed. Histopathologic examinations of the prostate were also performed. RESULTS The treatment zone appeared as an elliptical echogenic focus on ultrasound that increased in size with the application of current. Gross and histopathologic correlation demonstrated that the treatment area included a central area of char with a surrounding area of coagulation. There were no deleterious effects to surrounding tissues. CONCLUSION Our results demonstrate the feasibility of percutaneous ultrasound-guided RF electrocautery ablation of canine prostate tissue.

Hepatic ablation using bipolar radiofrequency electrocautery.

RATIONALE AND OBJECTIVES Percutaneous methods have been used to treat primary and secondary hepatic neoplasms. In the current study, we evaluated the potential of bipolar radiofrequency (RF) electrocautery to increase in vitro liver tissue destruction when compared with monopolar RF electrocautery. METHODS Two needles (electrodes) were placed into fresh bovine liver tissue for use with bipolar electrocautery. Needle tip exposure was kept constant at 3 cm while other parameters, including treatment time, power (wattage), interneedle distance, and needle tip temperature, were changed. Pathologic and histologic correlation was performed, and tissue necrosis was weighed in grams for individual parameters. RESULTS There was a minimal threshold of approximately 45 degrees C where tissue coagulation occurred. Tissue coagulation increased the longer treatment went on. Increasing temperature, wattage, or both increased tissue coagulation such that necrosis was too rapid and char formation occurred, which prevented further coagulation. For all wattages and temperatures, there was increasing tissue necrosis with increasing needle separation, until a point at which further needle separation produced less tissue necrosis. Optimizing parameters allowed tissue coagulation of greater than 30 g. CONCLUSION Bipolar RF electrocautery shows promise for increasing the tissue coagulation in fresh bovine liver compared with the previously described monopolar technique.

Appearance of Solid Organ Injury with Contrast-Enhanced Sonography in Blunt Abdominal Trauma: Preliminary Experience

OBJECTIVE The purpose of this study was to compare the detection rate of injury and characterize imaging findings of contrast-enhanced sonography and non-contrast-enhanced sonography in the setting of confirmed solid organ injury. SUBJECTS AND METHODS This prospective study involved identifying hepatic, splenic, and renal injuries on contrast-enhanced CT. After injury identification, both non-contrast-enhanced sonography and contrast-enhanced sonography were performed to identify the possible injury and to analyze the appearance of the injury. The sonographic appearance of hepatic, splenic, and renal injuries was then analyzed, and the conspicuity of the injuries was graded on a scale from 0 (nonvisualization) to 3 (high visualization). RESULTS Non-contrast-enhanced sonography revealed 11 (50%) of 22 injuries, whereas contrast-enhanced sonography depicted 20 (91%) of 22 injuries. The average grade for conspicuity of injuries was increased from 0.67 to 2.33 for spleen injuries and from 1.0 to 2.2 for liver injuries comparing non-contrast-enhanced with contrast-enhanced sonography, respectively, on a scale from 0, being nonvisualization, to 3, being high visualization. The splenic injuries appeared hypoechoic with occasional areas of normal enhancing splenic tissue within the laceration with contrast-enhanced sonography. Different patterns were observed in liver injuries including a central hypoechoic region. In some liver injuries there was a surrounding hyperechoic region. CONCLUSION Contrast-enhanced sonography greatly enhances visualization of liver and spleen injuries compared with non-contrast-enhanced sonography. Solid organ injuries usually appeared hypoechoic on contrast-enhanced sonography, but often a hyperechoic region surrounding the injury also was identified with liver injuries.

Novel vascular sealing device for closure of percutaneous vascular access sites

To investigate the hemostatic capabilities of a novel vascular sealing device consisting of a balloon catheter and procoagulant, vascular sheaths were placed percutaneously in the femoral arteries of dogs. The sealing device was evaluated using the balloon catheter alone in six femoral arteries and with the addition of a procoagulant, in 21 femoral arteries. The balloon catheter alone was successfully deployed in six of six femoral arteries achieving immediate hemostasis. In a second study in which the procoagulant was delivered following balloon placement, the sealing device was successfully deployed and hemostasis was achieved in 20 of 21 attempts (95%) despite removal of the balloon catheter. In a subset of fully anticoagulated animals, hemostasis was achieved in the sealing device-treated arteries at 6.5+/-3.4 minutes, but in none of the controls (P < 0.001). This novel vascular sealing device successfully achieves rapid hemostasis in normal and anticoagulated dogs following percutaneous vascular procedures.

Evaluation of Short-term and Long-term Complications after Emergent Internal Iliac Artery Embolization in Patients with Pelvic Trauma

PURPOSE To assess the incidence of long- and short-term complications following internal iliac artery (IIA) embolization after blunt pelvic trauma. MATERIALS AND METHODS One hundred trauma patients with pelvic fractures underwent pelvic angiography from 1994 through 2006. Sixty-seven patients underwent IIA embolization. These patients were retrospectively identified for medical record review. Short- and long-term complications were defined as those occurring at less than or greater than 30 days, respectively. Complications and outcomes were assessed through chart review and, when possible, a standardized questionnaire. Patients who underwent IIA embolization were compared with matched control patients with blunt pelvic trauma who did not undergo pelvic arteriography. Individuals were matched by age, sex, year of admission, and injury scores. RESULTS There were no significant differences in skin necrosis, sloughing, pelvic perineal infection, or nerve injury between embolized and nonembolized patients within 30 days. There was no significant difference in claudication, skin ulceration, or regional pain at a mean of 18.4 months follow-up. In the long term, buttock, thigh, and perineal paresthesia occur at a significantly higher rate in embolized patients. Skin sloughing in the embolized patient group is an important but rare complication. CONCLUSIONS IIA embolization is an important means of controlling pelvic arterial hemorrhage. There is no significant increase in the risk of most evaluated long- and short-term complications in trauma patients who underwent IIA embolization versus those who did not. However, IIA embolization is associated with a marginally significantly increased rate of buttock, thigh, or perineal paresthesia.

Functional, dynamic, and anatomic MR urography: feasibility and preliminary findings.

RATIONALE AND OBJECTIVES The authors assessed the feasibility of using magnetic resonance (MR) urography to acquire functional, dynamic, and anatomic information in human subjects with normal and hydronephrotic kidneys. MATERIALS AND METHODS In subjects known to have or suspected of having hydronephrosis, split renal filtration fractions were measured with a customized magnetization-prepared, inversion-prepared gradient-recalled echo sequence to determine the T1 of flowing blood in the inferior vena cava and aorta before and after contrast medium administration and in the renal veins and arteries after contrast medium administration. Multiple timed sets of coronal fast spoiled gradient-echo 70 degrees flip-angle images were acquired before and after contrast medium administration to derive MR renograms from changes in the signal intensity of the cortex and medulla. Precontrast T2-weighted images were obtained with a three-dimensional fast spoiled gradient-echo maximum intensity projection pulse sequence, and postcontrast T1 maximum intensity projection images were also obtained to depict the renal anatomy. RESULTS Split filtration fraction differentiated normal from hydronephrotic kidneys. MR renograms depicted vascular, tubular, and ductal phases and differentiated between normal and hydronephrotic kidneys (P < .05, n = 20). Contrast medium dose correlated with the peak of the cortical signal intensity curves on the renogram (r = 0.7, P < .0005; n = 20). The sensitivities for the visual determination of hydronephrosis and unilateral delayed excretion of contrast material were both 100%, and the specificities were 64% and 85%, respectively. CONCLUSION The preliminary findings show promise for the use of MR urography in the comprehensive assessment of renal function, dynamics, and anatomy.

Maximizing Parameters for Tissue Ablation by Using an Internally Cooled Electrode

PURPOSE To compare an algorithm of gradually ramped-up power to a full-power-level technique to determine which technical parameters maximized tissue coagulation by using a saline-perfused electrode. MATERIALS AND METHODS Institutional review board approval was not necessary and animal committee approval was unnecessary because an ex vivo bovine liver model was used and the animals were not specifically killed for this study. This four-part experiment utilized multiple ablations of ex vivo bovine liver with a standard radiofrequency (RF) generator and an internally cooled needle. First, 10 RF ablations were performed at 20-60 W for 12 minutes. Second, ablation volumes obtained from an algorithm of eight ablations performed at 50 W were compared with those obtained from an algorithm of eight ablations that were gradually ramped-up to 50 W, until full impedance. Third, volumes obtained from 10 ablations performed at impedance control power levels were compared with those obtained from 10 ablations performed with a gradual ramp-up of power that started at 50 W, terminating at full impedance. Last, the third part was repeated, but with 11 ablations continuing past full impedance for 12 minutes each. RESULTS In the first part, maximum measurements of tissue coagulation seemed to plateau from 40 to 60 W. The second part produced significantly larger measurements of tissue coagulation than did the use of a constant power level of 50 W. The third and final parts produced larger measurements of tissue coagulation than did utilizing full power for 12 minutes. Larger measurements and volumes were obtained from repeat ablations after the generator reached impedance level than were obtained from ablations stopped at maximum impedance. CONCLUSION A gradual ramp-up of power and repeating ablations after power impedance level is reached are the two methods that increased tissue ablation in this ex vivo experiment.

Arabinogalactan-coated superparamagnetic iron oxide: effect of particle size in liver MRI

Objective We evaluated the effect of particle size on MR contrast-enhancing properties of arabinogalactan-coated superparamagnetic iron oxide (AG-SPIO) in tumor-bearing rats. Materials and Methods T2*-weighted gradient-recalled echo MR studies were performed on rats with surgically implanted liver tumors before and after AG-SPIO administration. Contrast-to-noise ratio (CNR) and percent contrast enhancement (PCE) were calculated for animals given small (15.7 ± 9.5 nm; n = 6), medium (49.1 ± 19.7 nm; n = 4), and large (86.9 ± 27.5 nm; n = 4) particles intravenously (10 μmol Fe/kg). Results Postcontrast CNRs were 15.8 ± 6.9, 8.9 ± 4.1, and 10.0 ± 1.8 for small, medium, and large particle groups, respectively. The PCE was −60.0 ± 3.3, −75.5 ± 7.9, and −80.5 ± 1.2%. There was a significant difference in pre-versus postcontrast CNR for all particle sizes (p < 0.001) and in PCE for stnall particles as compared with the two larger sizes (p < 0.001). There was no between-group statistical difference in postcontrast CNR for any particle size. Conclusion Larger AG-SPIO particles slightly improve liver contrast enhancement, but have no significant effect on hepatic lesion detection as assessed by CNR. Index Terms Iron oxide—Contrast media—Liver—Magnetic resonance imaging.

Preclinical evaluation of manganese carbonate particles for magnetic resonance imaging of the liver

RATIONALE AND OBJECTIVES We characterized the physical, biological, and imaging properties of a manganese (Mn) carbonate particle suspension, a contrast agent for hepatic magnetic resonance (MR) imaging. METHODS Mn carbonate suspensions were produced by controlled precipitation and characterized using light microscopy, transmission electron microscopy, and in vitro relaxivity studies. Efficacy of the agent was studied in normal and tumor-bearing rats using T1-weighted MR imaging. RESULTS Following intravenous injection of Mn carbonate particles at doses ranging from 10 to 100 mumol Mn/kg, peak hepatic contrast enhancement of approximately 35% occurred from about 125 min until the termination of the MR imaging studies that varied from 125 to 305 min. Lesion conspicuity was increased because of relative intensity differences between normal liver and tumor. Data also showed that Mn carbonate particles dissolved on delivery to the liver, allowing Mn to interact with intrahepatic macromolecular complexes to provide positive contrast enhancement. CONCLUSION Mn carbonate particles produce significant and sustained hepatic enhancement and should improve detection of small or isointense liver lesions.