Integral role of interventional radiology in the development of a pediatric liver transplantation program.

The aim of this study was to examine the role of interventional radiology (IR) in the pretransplant evaluation of potential living-related liver transplantation (LRLT) donors and in the post-transplant management of pediatric liver transplant recipients. Medical records and procedural reports were reviewed of 12 potential donors and five recipients for left lateral segment liver transplants. Procedures performed by the IR Division, clinical indications, and complications were tabulated. Retrospective calculation of radiation exposure to the skin and gonads of the donors and recipients were made. Three-dimensional ultrasound (3D US) was used in all 12 potential donors to screen for the donor with the most appropriately sized left lateral segment. The four optimal donor candidates underwent contrast angiography in order to measure the diameter and screen for variant arterial supply to the left lateral segment. Pretransplantation, one recipient underwent mesenteric angiography with indirect portography to confirm thrombosis of the portal vein and to prove patency of the splenomesenteric venous confluence. Three children underwent LRLT and two children received split livers from cadaveric donors. Thirty-two IR procedures were performed after transplantation (Tx) in the four transplant survivors (one child died following Tx). These IR procedures included: ultrasound-guided percutaneous liver biopsy to evaluate the pathologic cause of liver dysfunction (seven); placement of nasal jejunal feeding tubes (three) or a peripherally inserted central catheter (four) for nutritional and pharmacologic support; large-volume diagnostic and therapeutic paracentesis (two) and thoracentesis (one); percutaneous catheter drainage of symptomatic large pleural effusions (two), large-volume chylous ascites (one) (with later drain removal [one]), and a large biloma (one); percutaneous biliary drain placement (three), biliary drain replacement (two), and balloon cholangioplasty (four) to relieve obstructive jaundice from biliary enteric anatomic strictures; and mesenteric arteriography (one) for suspected thrombosis of the hepatic artery. No complications occurred. Mean skin and gonadal radiation doses were 193 mGy and 27 mGy, respectively, for donors, and 164 mGy and 60 mGy, respectively, for recipients. Even in a program such as this, with a limited series of pediatric liver Txs, it is apparent that IR plays an integral role in optimizing the clinical outcome and use of resources. Specific benefits included: selection of optimal donors; accurate mapping of the donor and occasionally recipient hepatic vasculature; and, most importantly, providing relatively safe minimally invasive procedures for nutritional support and diagnosis and management of untoward events after Tx. When possible, ultrasound guidance should be used to avoid excessive cumulative fluoroscopic exposure to recipients.

Fatal paradoxic embolism occurring during IVC filter insertion in a patient with chronic pulmonary thromboembolic disease.

A patient diagnosed with chronic thromboembolic disease experienced a fatal intraprocedural paradoxic embolism during inferior vena cava (IVC) filter insertion. The frequency of patent intra-atrial shunts in patients with chronic thromboembolic disease is surprisingly high, occurring in approximately 29.5% of patients with chronic thromboembolic disease. Prevention of embolic events during venous interventions in such cases requires that the operator recognize that central shunts may be present and strictly adhere to meticulous technique during IVC filter insertion.

A self-oscillating detuning-insensitive class-E transmitter for implantable microsystems.

This paper describes a low-cost, self-oscillating, detuning-in-sensitive, class-E driver for transcutaneous power and data transmission to implantable microsystems. A voltage feedback scheme using a fast comparator for zero-crossing detection and a CMOS start-up circuit were used to stabilize the class-E operation for various transmitter coil inductance values. This technique solves the common problem of mismatch between the switching frequency of the driving device and the resonant frequency of the load network, which can cause excessive power loss and damage to the active device. Data is transmitted by AM modulation of the carrier through switching the power supply between two levels. The transmitter uses a 9-V supply, consumes 212 mA, operates at 3.9 MHz, and has an efficiency of 71%. The efficiency is stable (< 2% change) against 13% variations in the inductance value of a pancake shaped transmitter coil. Index Terms-Biomedical microsystems, class-E transmitter, implantable electronics, inductive powering, transcutaneous links.

Value of three-dimensional US for optimizing guidance for ablating focal liver tumors.

PURPOSE: To determine if three-dimensional ultrasound (3D US), by nature of its ability to simultaneously evaluate structures in three orthogonal planes and to study relationships of devices to tumor(s) and surrounding anatomic structures from any desired orientation, adds significant additional information to real-time 2D US used for placement of devices for ablation of focal liver tumors. MATERIALS AND METHODS: Sixteen patients underwent focal ablation of 23 liver tumors during two intraoperative cryoablation (CA) procedures, three intraoperative radiofrequency ablation (RFA) procedures, 11 percutaneous ethanol injections (PEI) procedures, and six percutaneous RFA procedures. After satisfactory placement of the ablative device(s) with 2D US guidance, 3D US was used to reevaluate adequacy to device position. Information added by 3D US and resultant alterations in device deployment were tabulated. RESULTS: 3D US added information in 20 of 22 (91%) procedures and caused the operator to readjust the number or position of ablative devices in 10 of 22 (45%) of procedures. Specifically, 3D US improved visualization and confident localization of devices in 13 of 22 (59%) procedures, detected unacceptable device placement in 10 of 22 (45%), and determined that 2D US had incorrectly predicted device orientation to a tumor in three of 22 (14%). CONCLUSIONS: Compared to conventional 2D US, 3D US provides additional relationship information for improved placement and optimal distribution of ablative agents for treatment of focal liver malignancy.

Pulmonary embolism from pulse-spray pharmacomechanical thrombolysis of clotted hemodialysis grafts: urokinase versus heparinized saline.

PURPOSE: To compare the frequency and extent of pulmonary embolism (PE) occurring during pulse-spray pharmacomechanical thrombolysis (PSPMT) of clotted hemodialysis grafts with use of either urokinase (UK) or heparinized saline (HS). Postintervention primary patency and complication rates were compared for each method of thrombolysis. METHODS AND MATERIALS: Twenty-seven patients were enrolled in this prospective, randomized, double-blind study evaluating PE with two PSPMT agents. The doses of heparin were similar between groups. The only variable was that one group of patients received UK and the other received HS. In two cases, the venous anastomosis could not be crossed. Eleven patients were treated with UK and 14 with HS. Nuclear medicine perfusion lung scans were performed before treatment and after graft declotting procedures. Lung perfusion was quantified to 10% of a pulmonary segment (0 = normal perfusion, 1 = segmental perfusion defect), with nine segments counted for each lung. RESULTS: Baseline nuclear medicine perfusion lung scan results were abnormal (> or = 20% segmental perfusion defect) in 19 patients (70.4%). New PE (one or more pulmonary segments) occurred in two patients treated with UK (18.2%) and nine patients treated with HS (64.3%; P = .04). All cases of PE were asymptomatic. Quantitative global pulmonary perfusion analyses revealed that treatment with UK improved flow to 0.2 +/- 2.0 pulmonary segments, whereas treatment with HS decreased perfusion to 1.0 +/- 1.7 segments (P = .16, NS). Although postintervention primary patency rates were similar according to life-table analysis (P = .76, NS), complication rates were higher with use of HS (n = 4, 28.6%) than with use of UK (n = 2, 18.2%) (P = .6, NS). CONCLUSIONS: All PE were asymptomatic during PSPMT, but treatment with UK reduced the rate of PE and tended to result in smaller defects in lung scan results. Most patients undergoing hemodialysis have abnormal baseline perfusion scan results, but PSPMT with UK improved many of them. The postintervention primary patency rates were similar between groups, but complications were more frequent after treatment with HS.

Early rethrombosis of clotted hemodialysis grafts: graft salvage achieved with an aggressive approach.

OBJECTIVE: The purpose of this study was to assess the efficacy of repeated pulsed spray pharmacomechanical thrombolysis for salvage of early rethrombosis of hemodialysis grafts and to identify factors that predict successful outcome. MATERIALS AND METHODS: Thirty-four patients with initial successful thrombolysis were referred for repeated thrombolysis because of early rethrombosis. Repeated thrombolysis occurred within 1 month of initial thrombolysis. Technical success and patency rates were calculated. Causes of graft thrombosis and procedural modifications were analyzed. RESULTS: The 39 rethrombosed grafts were successfully treated using pharmacomechanical thrombolysis, and patients underwent subsequent hemodialysis. The underlying flow-limiting stenoses were treated with balloon angioplasty using a larger balloon (41%), a same-size angioplasty balloon (18%), stent placement (15%), or increased anticoagulation (5%). A new stenosis location was discovered in 18%. Mean primary patency was 80.9 days (2.6 months) and secondary patency was 235.4 days (7.8 months). With life table analysis, 1-, 3-, 6-, and 12-month primary patency rates were 72%, 31%, 23%, and 15%, and secondary patency rates were 77%, 62%, 51%, and 31%, respectively. Graft patency rates in our study were compared with our institutional historic graft patency rates, with no significant difference noted (p = 0.76). No major procedural complications occurred. CONCLUSION: Adequate technical success and patency rates for pharmacomechanical thrombolysis occur even for hemodialysis grafts that rethrombose within 1 month. After thrombolysis, aggressive search for and treatment of additional stenoses are warranted.

Adjunctive 3D US for achieving portal vein access during transjugular intrahepatic portosystemic shunt procedures.

PURPOSE: To evaluate the usefulness of information provided by three-dimensional ultrasound (3D US) and to determine whether 3D US decreased the number of passes required to obtain portal vein (PV) access during creation of transjugular intrahepatic portosystemic shunts (TIPS). MATERIALS AND METHODS: Intermittent 3D US volume acquisitions were obtained during creation of TIPS in 20 patients. Useful information provided by 3D US was tabulated. The number of passes required to achieve PV access was recorded and results were compared retrospectively to 25 patients who underwent TIPS without 3D US. RESULTS: 3D US documented that the operator's opinion of which hepatic vein had been selected was incorrect in nine patients (45%), detected unfavorable PV anatomy that required modification of equipment or technique in seven patients (35%), permitted estimation of the trajectory required to access the targeted PV in all patients (100%), assisted in selecting the optimal point along the hepatic vein for origination of the needle pass in 11 patients (55%), allowed avoidance of a large hepatocellular carcinoma in one patient (5%), and confirmed that access into the main PV was intrahepatic in four patients (20%). The mean number of needle passes decreased from 10.4 in the historic control group to 4.6 in the 3D US group (P = .0001). CONCLUSION: 3D US provided imaging information that detected technical errors and altered anatomy, and provided positional and directional information to significantly improve needle pass efficiency.

Adjunctive 3D US for achieving portal vein access during transjugular intrahepatic portosystemic shunt procedures.

PURPOSE: To evaluate the usefulness of information provided by three-dimensional ultrasound (3D US) and to determine whether 3D US decreased the number of passes required to obtain portal vein (PV) access during creation of transjugular intrahepatic portosystemic shunts (TIPS). MATERIALS AND METHODS: Intermittent 3D US volume acquisitions were obtained during creation of TIPS in 20 patients. Useful information provided by 3D US was tabulated. The number of passes required to achieve PV access was recorded and results were compared retrospectively to 25 patients who underwent TIPS without 3D US. RESULTS: 3D US documented that the operator's opinion of which hepatic vein had been selected was incorrect in nine patients (45%), detected unfavorable PV anatomy that required modification of equipment or technique in seven patients (35%), permitted estimation of the trajectory required to access the targeted PV in all patients (100%), assisted in selecting the optimal point along the hepatic vein for origination of the needle pass in 11 patients (55%), allowed avoidance of a large hepatocellular carcinoma in one patient (5%), and confirmed that access into the main PV was intrahepatic in four patients (20%). The mean number of needle passes decreased from 10.4 in the historic control group to 4.6 in the 3D US group (P = .0001). CONCLUSION: 3D US provided imaging information that detected technical errors and altered anatomy, and provided positional and directional information to significantly improve needle pass efficiency.

Importance of Doppler analysis of transmitted atrial waveforms prior to placement of central venous access catheters.

PURPOSE: To assess the sensitivity of Doppler flow analysis of the axillary and internal jugular veins to screen for clinically occult thoracic central veno-occlusive disease and predict successful placement of central access catheters. MATERIALS AND METHODS: Sixty-seven patients underwent both duplex sonographic evaluation of the axillary and internal jugular veins and contrast venography prior to placement of a central venous catheter. Duplex evaluation included visual evidence of veno-occlusive disease as well as the presence or absence of normal transmitted polyphasic atrial waves and respiratory variation of flow. Diagnostically adequate venograms were available for comparison with the duplex sonograms in 168 access routes (access site plus downstream conduit veins). The contrast venograms and sonograms were compared by using retrospective blinded interpretation. Outcome of attempted catheter placement was tabulated. RESULTS: Directed sonographic imaging of the axillary and internal jugular vein allowed detection of access route veno-occlusive disease with a sensitivity of only 33.3%. Alternatively, when Doppler flow analysis found atrial waveforms that were not polyphasic, central conduit occlusive disease was detected with a sensitivity of 79.6%. Monophasic atrial waveforms were associated with a 25% failure rate of catheterization due to central vein occlusive disease, whereas polyphasic atrial waveforms were correlated with a 100% success rate for catheter placement. CONCLUSION: In asymptomatic patients, sonographic imaging alone misses most instances of central veno-occlusive disease. However, Doppler flow analysis of transmitted atrial waveforms substantially improved the sensitivity. A normal polyphasic atrial waveform virtually excludes the possibility of a more central venous occlusion or stenosis greater than 80% and ensures an adequate route for central venous catheterization.

Three-dimensional gray scale ultrasonographic imaging of the celiac axis: preliminary report.

The vessels of the celiac axis were evaluated in 16 healthy volunteers with three-dimensional gray scale ultrasonography. Sonographic volume data sets were obtained from both sagittal and transverse planes. The visualization of specific branches of the celiac artery (hepatic, splenic, left gastric, gastroduodenal, left hepatic, right hepatic, right gastric) was evaluated, and each vessel was placed in one of four categories on the basis of the appearance of the specific vessel and image clarity (not seen, poorly seen, adequately seen, well seen). Each vessel was evaluated on an initial two-dimensional scan and on a second scan using the entire volume to optimize and follow the designated vessel using rotating, referencing, and scrolling display capabilities. The ability to manipulate an entire volume improved visualization of the selected vessels as noted by an improved score. The proportion of vessels in the "not seen" and "poorly seen" categories decreased from the initial scan (62.5%) to the scan utilizing the entire volume (36%). Alternatively, the percentage of vessels in the "adequately seen" to "well seen" categories improved from 37.50% on the initial examination to 64% on the scans using the entire volume to depict vascular anatomy. The optimal plane to image each vessel depended on the course of a specific vessel. For optimal imaging of all the selected vessels, both sagittal and transverse volume acquisitions and both sagittal and transverse planes were needed. Three-dimensional imaging provided a new imaging plane (coronal) that was useful in following and identifying vessels, especially those vessels coursing in a right to left direction. Vascular variants were identified by this technique in two of 16 subjects. Vascular imaging was improved with three-dimensional ultrasonography, and this imaging method may provide additional assistance in decision making when evaluating abdominal vessels.

IVC filter tilt and asymmetry: comparison of the over-the-wire stainless-steel and titanium Greenfield IVC filters.

PURPOSE: A comparison of tilting, caval coverage, asymmetry, and insertion problems with the over-the-wire stainless-steel and titanium versions of the Greenfield filter. MATERIALS AND METHODS: The study compared 104 stainless-steel and 141 titanium Greenfield inferior vena cava (IVC) filter insertions. The angle the sheath and deployed filter made relative to the cava, as well as filter strut distribution, were determined from spot films. The proportionate caval coverage was computed from the cavogram (anteroposterior projection). Mean filter tilts, subgrouped by insertion site, and caval coverage were compared with the Student t test, whereas strut patterns were analyzed with a contingency table. RESULTS: The filter caval and sheath caval angles correlated. The filter caval angles varied with insertion site, but were lowest with a right jugular approach. Caval coverage was identical with both designs. The stainless-steel version resulted in a more uniform distribution of struts in comparison with the titanium version. The incidence of insertion problems was not significantly different between the filter types. CONCLUSIONS: While IVC filter tilting was not improved with the newer design, the pattern of struts was more uniformly symmetric with the stainless-steel device. The right jugular insertion site was associated with the lowest filter caval angles and the most symmetric pattern of struts.

Transrectal prostate ultrasonography: variability of interpretation.

PURPOSE: The current study was designed to compare the interpretation of the individual performing transrectal ultrasound examination (operator) with experienced individuals who interpreted the examination with and without the availability of clinical data. Inter-observer and intra-observer variability was compared to determine the reproducibility and reliability of the study. MATERIALS AND METHODS: All patients undergoing radical prostatectomy for treatment of localized carcinoma of the prostate underwent a transrectal ultrasound examination before the procedure. The sonogram was interpreted by the operator and reviewers. The radical prostatectomy specimen was examined pathologically and the staging as determined by ultrasound was compared with the pathological findings. RESULTS: Ultrasound operator accuracy for extracapsular extension and seminal vesicle invasion was 0.70 and 0.74, respectively, compared with the accuracy of the reviewers, which ranged from 0.59 to 0.75 and 0.44 to 0.74 for extracapsular extension and seminal vesicle invasion, respectively. In general, blinded reviews were less accurate than unblinded reviews but this was only statistically significant for 2 reviewers. CONCLUSIONS: Although for most reviewers the addition of clinical data did not improve the accuracy of the interpretation, an advantage was noted for the operator, that is, the individual performing the examination. In general, the technical quality of the examination was related to the accuracy of the readings.