Comparing and predicting the costs and outcomes of patients with major and minor stroke using the Boston Acute Stroke Imaging Scale neuroimaging classification system

BACKGROUND AND PURPOSE

A neuroimaging-based ischemic stroke classification system that predicts costs and outcomes would be useful for clinical prognostication and hospital resource planning. The Boston Acute Stroke Imaging Scale (BASIS), a neuroimaging-based ischemic stroke classification system, was tested to determine whether it was able to predict the costs and clinical outcomes of patients with stroke at an urban academic medical center.

MATERIALS AND METHODS

Patients with ischemic stroke who presented in the emergency department in 2000 (230 patients) and 2005 (250 patients) were classified by using BASIS as having either a major or minor stroke. Compared outcomes included death, length of hospitalization, discharge disposition, use of imaging and intensive care unit (ICU) resources, and total in-hospital cost. Continuous variables were compared by univariate analysis by using the Student t test or the Satterthwaite test adjusted for unequal variances. Categoric variables were tested with the chi(2) test. Multiple regression analyses related total hospital cost (dependent variable) to stroke severity (major versus minor), sex, age, presence of comorbidities, and death during hospitalization. Logistic regression analysis was applied to identify the significant predictive variables indicating a greater likelihood of discharge home.

RESULTS

In both years, individuals with strokes classified as major had a significantly longer length of stay, spent more days in the ICU, and had a higher cost of hospitalization than patients with minor strokes (all outcomes, P < .0001). All deaths (8 in 2000, 26 in 2005) occurred in patients with major stroke. Whereas 73% of patients with minor stroke were discharged home, only 12.2% of patients with major stroke were discharged home (P < .0001); 61% of patients with major stroke were discharged to a rehabilitation or skilled nursing facility. Patients with major stroke cost 4.4 times and 3.0 times that of patients with minor stroke in 2000 and 2005, respectively. Making up less than one third of all patients, patients with major stroke accounted for 60% of the total in-hospital cost of acute stroke care.

CONCLUSIONS

BASIS, a neuroimaging-based stroke classification system, is highly effective at predicting in-hospital resource use, acute-hospitalization cost, and outcome. Predictive ability was maintained across the years studied.

Comparison of excretory phase, helical computed tomography with intravenous urography in patients with painless haematuria

AIM

To compare excretory phase, helical computed tomography (CT) with intravenous (IV) urography for evaluation of the urinary tract in patients with painless haematuria.

MATERIALS AND METHODS

Ninety-one out-patients had IV urography followed by helical CT limited to the urinary tract. Both IV urograms and CT images were evaluated for abnormalities of the urinary tract in a blinded, prospective manner. The clinical significance of abnormalities was scored subjectively and receiver operator characteristic curve analysis was performed.

RESULTS

In 69 of 91 patients (76%), no cause of haematuria was identified. In 22 of 91 patients (24%), the cause of haematuria was identified as follows: transitional cell cancer of the bladder (n=15), urinary tract stones (n=3), cystitis (n=2), haemorrhagic pyelitis (n=1) and benign ureteral stricture (n=1). With IV urography, there were 15 true-positive, seven false-negative and three false-positive interpretations. With CT, there were 18 true-positive, four false-negative and two false-positive interpretations. There was no significant difference between IV and CT urography for the significance of the positive interpretations (n=0.47).

CONCLUSION

Excretory phase CT urography was comparable with IV urography for evaluation of the urinary tract in patients with painless haematuria. However, the study population did not include any upper tract cancers.

A cost--utility analysis of treatment options for inguinal hernia in 1,513,008 adult patients

BACKGROUND

The controversial issue of the cost-effectiveness of laparoscopic inguinal hernia repair is examined, employing a decision analytic method.

MATERIALS AND METHODS

The NSAS, NHDS (National Center for Health Statistics), HCUP-NIS (Agency for Healthcare Research and Quality) databases and 51 randomized controlled trials were analyzed. The study group constituted of a total of 1,513,008 hernia repairs. Projection of the clinical, economic, and quality-of-life outcomes expected from the different treatment options was done by using a Markov Monte Carlo decision model. Two logistic regression models were used to predict the probability of hospital admission after an ambulatory procedure and the probability of death after inguinal hernia repair. Four treatment strategies were modeled: (1) laparoscopic repair (LR), (2) open mesh (OM), (3) open non-mesh (ONM), and (4) expectant management. Costs were expressed in US dollars and effectiveness in quality-adjusted life years (QALYs). The main outcome measures were the average and the incremental cost-effectiveness (ICER) ratios.

RESULTS

Compared to the expectant management, the incremental cost per QALY gained was 605 dollars (4086 dollars, 9.04 QALYs) for LR, 697 dollars (4290 dollars, 8.975 QALYs) for OM, and 1711 dollars (6200 dollars, 8.546 QALYs) for ONM. In sensitivity analysis the two major components that affect the cost-effectiveness ratio of the different types of repair were the ambulatory facility cost and the recurrence rate. At a LR ambulatory facility cost of 5526 dollars the ICER of LR compared to OM surpasses the threshold of 50,000 dollars/QALY.

CONCLUSIONS

On the basis of our assumptions this mathematical model shows that from a societal perspective laparoscopic approach can be a cost-effective treatment option for inguinal hernia repair.

Colorectal cancer screening issues: a role for CT colonography?

Colorectal cancer is the third most common cancer in the United States and will cause 56,700 deaths in 2001, despite the availability of screening tests capable of detecting the disease at earlier stages and reducing mortality. This article reviews the natural history of colorectal cancer, common risk factors and prevention strategies, and the strengths, limitations, and cost effectiveness of available screening tests. Although reminders to undergo colorectal cancer screening have become commonplace in the popular media, compliance with screening guidelines remains poor. Although still an unproven technology for widespread screening, computed tomographic (CT) colonography has several attractive characteristics for a screening test. For example, CT scanners are widely available, in contrast to limited numbers of gastroenterologists and radiologists' declining skill and interest in barium enema examinations. Also, patients may be less reluctant to undergo CT colonography than screening colonoscopy. Development of virtual bowel cleansing could further increase compliance and thereby reduce mortality from colorectal cancer. Other articles in this Feature Section discuss technical details of CT colonography and its methodologic challenges.

Percutaneous radio-frequency ablation of hepatic metastases from colorectal cancer: long-term results in 117 patients

PURPOSE

To describe the results of an ongoing radio-frequency (RF) ablation study in patients with hepatic metastases from colorectal carcinoma.

MATERIALS AND METHODS

In 117 patients, 179 metachronous colorectal carcinoma hepatic metastases (0.9-9.6 cm in diameter) were treated with RF ablation by using 17-gauge internally cooled electrodes. Computed tomographic follow-up was performed every 4-6 months. Recurrent tumors were retreated when feasible. Time to new metastases and death for each patient and time to local recurrence for individual lesions were modeled with Kaplan-Meier analysis. Modeling determined the effect of number of metastases on the time to new metastases and death and effect of tumor size on local recurrence.

RESULTS

Estimated median survival was 36 months (95% CI; 28, 52 months). Estimated 1, 2, and 3-year survival rates were 93%, 69%, and 46%, respectively. Survival was not significantly related to number of metastases treated. In 77 (66%) of 117 patients, new metastases were observed at follow-up. Estimated median time until new metastases was 12 months (95% CI; 10, 18 months). Percentages of patients with no new metastases after initial treatment at 1 and 2 years were 49% and 35%, respectively. Time to new metastases was not significantly related to number of metastases. Seventy (39%) of 179 lesions developed local recurrence after treatment. Of these, 54 were observed by 6 months and 67 by 1 year. No local recurrence was observed after 18 months. Frequency and time to local recurrence were related to lesion size (P < or =.001).

CONCLUSION

RF ablation is an effective method to treat hepatic metastases from colorectal carcinoma.

Pancreatic cancer: cost-effectiveness of imaging technologies for assessing resectability

PURPOSE

To evaluate the cost-effectiveness of imaging strategies for the assessment of resectability in patients with pancreatic cancer.

MATERIALS AND METHODS

A decision model was developed to calculate costs and benefits (survival) accruing to hypothetical cohorts of patients with known or suspected pancreatic cancer. Results are presented as cost per life-year gained under various scenarios and assumptions of diagnostic test characteristics, surgical mortality, disease characteristics, and costs.

RESULTS

With best estimates for all data inputs, the strategy of computed tomography (CT) followed by laparoscopy and laparoscopic ultrasonography (US) had an incremental cost-effectiveness ratio of $87,502 per life-year gained, compared with best supportive care. This strategy was significantly more cost-effective than CT followed by magnetic resonance (MR) imaging and was significantly less expensive than other imaging strategies while providing a statistically and clinically insignificant difference in life-year gains. A strategy involving no imaging (immediate surgery) was more expensive but less effective than all imaging strategies. A hypothetical perfect test with cost equal to that of CT followed by MR had an incremental cost-effectiveness ratio of $64,401 per life-year gained, compared to best supportive care.

CONCLUSION

Most available imaging tests for assessing resectability of pancreatic cancer do not differ in effectiveness, but a strategy of CT, laparoscopy, and laparoscopic US would consistently result in significantly lower costs than other imaging tests under a wide range of scenarios.

Potential influence of acute CT on inpatient costs in patients with ischemic stroke

RATIONALE AND OBJECTIVES

Patients presenting with ischemic brain symptoms have widely variable outcomes dependent to some degree on the pathologic basis of their stroke syndrome. The purpose of this study was to determine the cost implications of the emergency use of a computed tomographic (CT) protocol comprising unenhanced CT, head and neck CT angiography, and whole-brain CT perfusion.

MATERIALS AND METHODS

By using a retrospective patient database from a tertiary care facility and publicly available cost data, the authors derived the potential savings from the use of CT angiography. CT perfusion, or both at hospital arrival by means of a cost model. The cost of the CT angiography-CT perfusion protocol was determined from Medicare reimbursement rates and compared with that of traditional imaging protocols. Cost savings were estimated as a decrease in the length of stay for most stroke patients, whereas the most benign (lacunar) strokes were assumed to be managed in a non-acute setting. Misdiagnosis cost (erroneously not admitting a patient with nonlacunar stroke) was calculated as the cost of a severe complication. Sensitivity testing included varying the percentage of misdiagnosed patients and admitting patients with lacunar stroke.

RESULTS

The nationwide net savings that would result from the adoption of the CT angiography-CT perfusion protocol are in the $1.2 billion range (-$154 million to $2.1 billion) when patients with lacunar strokes are treated nonacutely and $1.8 billion when those patients are admitted for acute care.

CONCLUSION

The results demonstrate the potential effect of implementing a CT angiography-CT perfusion protocol. In particular, prompt CT angiography-CT perfusion imaging could have an effect on the cost of acute care in the treatment of stroke.

Endovascular versus open surgical elective repair of infrarenal abdominal aortic aneurysm: predictors of patient discharge destination

PURPOSE

To evaluate patient discharge destination after elective endovascular or open surgical repair of infrarenal abdominal aortic aneurysm and to determine predictors for discharge to home or to a rehabilitation center.

MATERIALS AND METHODS

All patients electively treated for infrarenal abdominal aortic aneurysm with endovascular repair (n = 182) or open surgery (n = 274) between January 1997 and September 1999 were included. From the hospital database, information on discharge destination, patient characteristics, complications, and length of stay was retrieved. Multiple logistic regression analysis was performed to determine predictors for discharge to home or to a rehabilitation center.

RESULTS

Patient characteristics did not differ significantly between the treatment groups, with the exception of age (mean age, 75.1 vs 72.9 years in the endovascular and open surgical group, respectively; P =.005). Patient discharge destinations differed significantly between the treatment groups (P =.001). After endovascular procedures, 156 (85.7%) of 182 patients went home and 19 (10.4%) of 182 patients went to a rehabilitation center. After open surgery, 187 (68.2%) of 274 patients went home and 64 (23.4%) of 274 patients went to a rehabilitation center. The odds ratio of discharge to a rehabilitation center, instead of home, following endovascular procedures versus open surgery was 0.23 (95% CI: 0.13, 0.43).

CONCLUSION

Following elective repair of infrarenal abdominal aortic aneurysm, significantly more patients went home after an endovascular procedure than after open surgery. Procedure type was a significant predictor of discharge destination.

CT colonography with teleradiology: effect of lossy wavelet compression on polyp detection--initial observations

PURPOSE

To assess the consequences of lossy compression on the diagnostic accuracy of CT colonography for detecting colonic polyps.

MATERIALS AND METHODS

Helical CT images of cleansed colonic segments were evaluated. Source images were compressed to 1:1, 10:1, and 20:1 ratios with lossy wavelet compression. Two independent readers blinded to corresponding colonoscopic results analyzed 144 randomly ordered colonic segments in multiplanar and volume-rendered endoscopic views. Sensitivity, specificity, and receiver operating characteristic curves were generated for each compression ratio on the basis of expressed confidence in lesion presence. Similar analyses were performed to assess distention and bowel preparation adequacy and evaluation time required.

RESULTS

Results based on video colonoscopy-confirmed lesions revealed 100% (four of four) sensitivity for lesions larger than 10 mm for compression ratios 1:1, 10:1, and 20:1 for both readers; sensitivities for all lesions smaller than 10 mm were 50%-78%, 38%-67%, and 38%-67% for respective ratios for both readers. Differences in diagnostic performance for each reader across ratios were not significant (P =.30-.99, McNemar test). The time required to evaluate and assess bowel preparation and distention adequacy did not change significantly across ratios.

CONCLUSION

On the basis of the patient sample, lossy compression of transverse source images to at least a 20:1 ratio did not adversely affect diagnostic performance or evaluation time for CT colonography.

Hospital costs for elective endovascular and surgical repairs of infrarenal abdominal aortic aneurysms

PURPOSE

To determine and compare the average in-hospital costs of elective open surgical and endovascular repairs of infrarenal abdominal aortic aneurysms.

MATERIALS AND METHODS

Total actual cost data for patients undergoing elective endovascular (n = 181) or open surgical (n = 273) repair of abdominal aortic aneurysms between 1997 and 1999 were retrieved. The mean total hospital cost (including stent-graft costs and excluding attending physician fees) and mean postoperative length of stay were calculated for each treatment group. Costs were expressed in 1999 U.S. dollars.

RESULTS

Endovascular repair yielded a shorter postoperative length of stay than did open surgery (mean stay, 3.4 vs 8.0 days; P <.001) and a lower proportion of patients who were admitted to the intensive care unit for 1 full day or longer (2.8% vs 36.3%; P <.001). The mean total hospital cost was significantly higher for endovascular repair than for open surgery ($20,716 vs $18,484; P <.001).

CONCLUSION

Hospital costs were higher for endovascular repair than for open surgical repair. However, endovascular repair was associated with a decreased length of stay and fewer intensive care unit admissions. The increased mean hospital cost for endovascular repair was smaller than one would expect, considering the higher costs of endovascular grafts, as compared with those for surgical grafts (approximately $6,400 according to literature data).

Percutaneous tumor ablation: increased necrosis with combined radio-frequency ablation and intratumoral doxorubicin injection in a rat breast tumor model

PURPOSE

To determine whether a combination of intratumoral doxorubicin injection and radio-frequency (RF) ablation increases tumor destruction compared with RF ablation alone in an animal tumor model.

MATERIALS AND METHODS

R3230 mammary adenocarcinoma 1.2-1.5-cm- diameter nodules (n = 110) were implanted subcutaneously in 84 female Fischer rats. For initial experiments (n = 46), tumors were treated with (a) conventional, monopolar RF (250 mA +/- 25 [SD] at 70 degrees C +/- 1 for 5 minutes) ablation alone; (b) direct intratumoral doxorubicin injection (volume, 250 microL; total dose, 0.5 mg) alone; (c) combined therapy (doxorubicin injection immediately followed by RF ablation); (d) RF ablation and injection of 250 microL of distilled water; or (e) no treatment. In subsequent experiments, amount of doxorubicin (0.02-2.50 mg; n = 40 additional tumors) and timing of doxorubicin administration (2 days before to 2 days after RF ablation; n = 24 more tumors) were varied. Pathologic examination, including staining for mitochondrial enzyme activity and perfusion, was performed, and the resultant tumor destruction from each treatment was evaluated.

RESULTS

Coagulation diameter was 6.7 mm +/- 0.6 for tumors treated with RF ablation alone and 6.9 mm +/- 0.7 for those treated with RF ablation and water (P =.52), while intratumoral doxorubicin injection alone produced only 2.0-3.0 mm of coagulation (P <.001). Increased coagulation was observed only with combined doxorubicin injection and RF therapy (P <.001). Coagulation was dependent on concentration and timing of doxorubicin administration, with greatest coagulation (11.5 mm +/- 1.1) observed for doxorubicin administered within 30 minutes of RF ablation.

CONCLUSION

Adjuvant intratumoral doxorubicin injection increases coagulation in solid tumors compared with RF ablation alone. Increased tumor destruction is also seen when doxorubicin is administered after RF ablation, which suggests that RF ablation may sensitize tumors to chemotherapy. Such combination therapies may, therefore, offer improved methods for ablating solid tumors.

Inpatient costs of routine endovascular repair of abdominal aortic aneurysm

RATIONALE AND OBJECTIVES

The purpose of this study was to determine the inpatient cost of routine (ie, without emergent conversion to open repair during the hospital stay) endovascular stent-graft placement in a consecutive series of patients undergoing elective endovascular repair of abdominal aortic aneurysm (AAA) at a single institution.

MATERIALS AND METHODS

Inpatient hospital costs of 91 patients who underwent initial elective endovascular repair of AAA were analyzed retrospectively. All patients had participated in clinical trials at the authors' institution during the previous 6 years. Financial data were derived from the hospital's cost-accounting system; additional procedural data were collected from a departmental database and with chart review. Stent-graft and professional costs were excluded.

RESULTS

The mean total cost for endovascular repair was $11,842 (standard deviation [SD], $5,127), mean procedure time was 149 minutes (SD, 79 minutes), and mean length of stay was 3.5 days (SD, 2.3 days). Total cost depended on stent-graft type (means, $12,428 [bifurcated] vs $9,622 [tube]; P = .0002) and strongly correlated with procedure time and length of hospital stay (r = 0.78 and 0.66, respectively; P < .0001). Ninety-six percent of total costs for all patients were attributable to the following departments: operating theater (31%), radiology (31%), nursing (22%), and anesthesia (12%).

CONCLUSION

Overall costs are greater with bifurcated than with tube stent-grafts. Total procedure-related costs are divided relatively equally between the operating theater, the radiology department, and the combination of the nursing and anesthesia departments.

Percutaneous radio-frequency ablation of liver metastases from breast cancer: initial experience in 24 patients

PURPOSE

To evaluate the authors' initial experience in a consecutive series of 24 patients with breast cancer liver metastases treated with radio-frequency (RF) ablation.

MATERIALS AND METHODS

Twenty-four consecutive patients with 64 metastases measuring 1.0--6.6 cm in diameter (mean, 1.9 cm) underwent ultrasonography-guided percutaneous RF ablation with 18-gauge, internally cooled electrodes. Treatment was performed with the patient under conscious sedation and analgesia or general anesthesia. A single lesion was treated in 16 patients, and multiple lesions were treated in eight patients. Follow-up with serial computed tomography ranged from 4 to 44 months (mean, 10 months; median, 19 months).

RESULTS

Complete necrosis was achieved in 59 (92%) of 64 lesions. Among the 59 lesions, complete necrosis required a single treatment session in 58 lesions (92%) and two treatment sessions in one lesion (2%). In 14 (58%) of 24 patients, new metastases developed during follow-up. Ten (71%) of these 14 patients developed new liver metastases. Currently, 10 (63%) of 16 patients whose lesions were initially confined to the liver are free of disease. One patient died of progressive brain metastases. No major complications occurred. Two minor complications were observed.

CONCLUSION

On the basis of preliminary study results, percutaneous RF ablation appears to be a simple, safe, and effective treatment for focal liver metastases in selected patients with breast cancer.

Radio-frequency thermal ablation with NaCl solution injection: effect of electrical conductivity on tissue heating and coagulation-phantom and porcine liver study

PURPOSE

To characterize the effects of NaCl concentration on tissue electrical conductivity, radio-frequency (RF) deposition, and heating in phantoms and optimize adjunctive NaCl solution injection for RF ablation in an in vivo model.

MATERIALS AND METHODS

RF was applied for 12-15 minutes with internally cooled electrodes. For phantom experiments (n = 51), the NaCl concentration in standardized 5% agar was varied (0%-25.0%). A nonlinear simplex optimization strategy was then used in normal porcine liver (n = 44) to determine optimal pre-RF NaCl solution injection parameters (concentration, 0%-38.5%; volume, 0-25 mL). NaCl concentration and tissue conductivity were correlated with RF energy deposition, tissue heating, and induced coagulation.

RESULTS

NaCl concentration had significant but nonlinear effects on electrical conductivity, RF deposition, and heating of agar phantoms (P<.01). Progressively greater heating was observed to 5.0% NaCl, with reduced temperatures at higher concentrations. For in vivo liver, NaCl solution volume and concentration significantly influenced both tissue heating and coagulation (P<.001). Maximum heating 20 mm from the electrode (102.9 degrees C +/- 4.3 [SD]) and coagulation (7.1 cm +/- 1.1) occurred with injection of 6 mL of 38.5% (saturated) NaCl solution.

CONCLUSION

Injection of NaCl solution before RF ablation can increase energy deposition, tissue heating, and induced coagulation, which will likely benefit clinical RF ablation. In normal well-perfused liver, maximum coagulation (7.0 cm) occurs with injection of small volumes of saturated NaCl solution.

Cost-effectiveness of colorectal cancer screening

PURPOSE

To determine the most cost-effective colorectal cancer screening strategy costing less than $100,000 per life-year saved and to determine how available strategies compare with each other.

MATERIALS AND METHODS

Standardized methods were used to calculate incremental cost-effectiveness ratios (ICERs) from published estimates of cost and effectiveness of colorectal cancer screening strategies, and the direction and magnitude of any effect on the ratio from parameter estimate adjustments based on literature values were estimated.

RESULTS

Strategies in which double-contrast barium enema examination was performed emerged as optimal from all studies included. In average-risk individuals, screening with double-contrast barium enema examination every 3 years, or every 5 years with annual fecal occult blood testing, had an ICER of less than $55,600 per life-year saved. However, double-contrast barium enema examination screening every 3 years plus annual fecal occult blood testing had an ICER of more than $100,000 per life-year saved. Colonoscopic screening had an ICER of more than $100,000 per life-year saved, was dominated by other screening strategies, and offered less benefit than did double-contrast barium enema examination screening.

CONCLUSION

Double-contrast barium enema examination can be a cost-effective component of colorectal cancer screening, but further modeling efforts are necessary.

Radiofrequency tissue ablation: physical principles and techniques for increasing coagulation necrosis

Radiofrequency tumor ablation has been demonstrated as a reliable method for creating thermally-induced coagulation necrosis using either a percutaneous approach with image-guidance or direct surgical placement of thin electrodes into tissues to be treated. Early clinical trials with this technology have studied the treatment of hepatic, cerebral, and bony malignancies. The extent of coagulation necrosis induced with conventional monopolar radiofrequency electrodes is dependent on overall energy deposition, the duration of radiofrequency application, and radiofrequency electrode tip length and gauge. This article will discuss these technical considerations with the goal of defining optimal parameters for radiofrequency ablation. Strategies to further increase induced coagulation necrosis including: multiprobe and bipolar arrays, and internally-cooled radiofrequency electrodes, with or without pulsed-radiofrequency or cluster technique will be presented. The development and laboratory results for many of these radiofrequency techniques and potential biophysical limitations to radiofrequency induced coagulation, such as perfusion mediated tissue cooling (vascular flow) will likewise be discussed.

Injection of allogeneic bone marrow cells into the portal vein of swine in utero

The ability to safely manipulate the immune system of the developing fetus carries the hope of effective treatment strategies for certain congenital disorders that can be diagnosed during gestation. One possible intervention is the induction of specific transplantation tolerance to an adult donor who could provide tissue after birth without the need for immunosuppression. Although the introduction of allogeneic stem cells to a developing immune system has been shown to result in hematopoietic chimerism, donor-specific transplantation tolerance has not been demonstrated in a large animal model. In previous reports of in utero stem-cell transplantation, the cells were injected into the fetus by an intraperitoneal route. We sought to improve upon this technique of cell transplantation by developing a method for the safe delivery of allogeneic stem cells directly into the hepatic circulation of fetal swine. In the second phase of our study, we determined if adult allogeneic bone marrow cells delivered to the fetus by this intravascular route could result in result in hematopoietic chimerism and donor-specific transplantation tolerance. A method of successful intravascular injection was designed in which a laparotomy was performed on a sow at midgestation (50-55 days) to administer 1 cc of inoculum into the portal vein of each fetus using transuterine ultrasound guidance and a 25-gauge spinal needle. In one sow, 10 piglets were injected with saline to test safety, and 8 piglets were born. For transplantation of stem cells to the fetuses, donor bone marrow was harvested from a genetically defined miniature swine. In one sow the marrow was injected without T-cell depletion resulting in abortion. In the third sow, the marrow was depleted of T-cells to less than 0.01% using magnetic beads conjugated to anti-CD3 monoclonal antibodies. No chimerism was detected in these offspring. Only in the fourth sow where the T-cell depletion was reduced to about 1% of the cells in the inoculum did one animal demonstrate chimerism. This piglet showed reproducible blood chimerism (0.95% donor cells) detected by flow cytometry measurement of monoclonal antibodies to the donor MHC. In addition, this animal demonstrated hyporesponsiveness to donor lymphocytes in an MLR assay while reacting strongly to third-party stimulator cells. A split-thickness skin graft from the donor was accepted, and a third-party graft was rapidly rejected.

Percutaneous tumor ablation: increased coagulation by combining radio-frequency ablation and ethanol instillation in a rat breast tumor model

PURPOSE

To determine if percutaneously applied radio frequency (RF) combined with percutaneous ethanol instillation (PEI) can increase the extent of ablation in rat breast tumors.

MATERIALS AND METHODS

R3230 mammary adenocarcinoma was implanted bilaterally in the mammary fat pads of 18 female rats. The tumor nodules measured 1. 2-1.5 cm. Eight tumors each were treated with (a) conventional, monopolar RF (96 mA +/- 28; 70 degrees C for 5 minutes); (b) PEI (250 microL of ethanol infused over 1 minute); (c) combined therapy of PEI immediately followed by RF ablation; or (d) combined therapy of RF ablation immediately followed by PEI. Four tumors were not treated and served as controls. Histopathologic examination included staining for mitochondrial enzyme activity. Resultant coagulation necrosis was compared between treatment groups.

RESULTS

Coagulation necrosis was observed only within treated tumors. Tumors treated with RF alone had 6.7 mm +/- 0.6 of coagulation surrounding the electrode, and those treated with PEI alone had 6.4 mm +/- 0.6 of coagulation around the instillation needle (not significant). Significantly increased coagulation of 10.1 mm +/- 0.9 (P: <.001) was observed with the combined therapy of PEI followed by RF. RF followed by PEI did not increase coagulation (6.4 mm +/- 0.8 around the needle; not significant).

CONCLUSION

PEI followed by RF ablation therapy increases the extent of induced coagulation necrosis in rat breast tumors, as compared with either therapy alone.

Tumor ablation with radio-frequency energy

Tumor ablation by using radio-frequency energy has begun to receive increased attention as an effective minimally invasive approach for the treatment of patients with a variety of primary and secondary malignant neoplasms. To date, these techniques have been used to treat tumors located in the brain, musculoskeletal system, thyroid and parathyroid glands, pancreas, kidney, lung, and breast; however, liver tumor ablation has received the greatest attention and has been the subject of a large number of published reports. In this article, the authors review the technical developments and early laboratory results obtained with radio-frequency ablation techniques, describe some of the early clinical applications of these techniques, and conclude with a discussion of challenges and opportunities for the future.

Cost-effectiveness of functional imaging tests in the diagnosis of Alzheimer disease

PURPOSE

To evaluate the cost-effectiveness of functional neuroimaging in the work-up of patients at specialized Alzheimer disease clinics.

MATERIALS AND METHODS

A decision model was used to calculate costs and benefits (in quality-adjusted life-years [QALYs]) that accrued to hypothetical cohorts of patients at presentation to an Alzheimer disease center. Sensitivity analysis was performed to examine the effects of diagnostic test characteristics, therapeutic efficacy, disease severity, and costs on cost-effectiveness.

RESULTS

The incremental cost-effectiveness ratio of dynamic susceptibility contrast material-enhanced magnetic resonance (MR) imaging was $479,500 per QALY (compared with the usual diagnostic work-up), while visual or quantitative single photon emission computed tomography (SPECT) was dominated (higher costs, lower effectiveness) by the usual diagnostic work-up. These results depend critically on the sensitivity and specificity of the standard diagnostic work-up, the effectiveness of drug treatment, and the disease severity. Varying these parameters resulted in estimates of incremental cost-effectiveness for dynamic susceptibility contrast-enhanced MR imaging of $24,680 to $8.6 million per QALY. SPECT either was dominated by the usual diagnostic work-up or had cost-effectiveness ratios of $180,200 to $6 million per QALY.

CONCLUSION

The addition of functional neuroimaging to the usual diagnostic regimen at Alzheimer disease clinics is not cost-effective given the effectiveness of currently available therapies.

Treatment of intrahepatic malignancy with radiofrequency ablation: radiologic-pathologic correlation

BACKGROUND

Radiofrequency (RF)-induced tissue coagulation represents a new approach for the thermal destruction of tumors within the liver. The purpose of the current study was to 1) assess technique safety; 2) determine the extent and evolution of induced cellular damage; and 3) correlate the observed pathologic effects with radiologic studies.

METHODS

Twenty-three tumors measuring </= 8 cm (19 colorectal metastases and 4 hepatomas) in 22 patients were treated with RF (range, 500-1550 milliamperes) using internally cooled electrodes. All treated tumors were resected to allow pathologic analysis. Eleven tumors were treated intraoperatively under ultrasonographic guidance and excised immediately. Twelve tumors were treated percutaneously using ultrasound or computed tomography (CT) guidance and subsequently were excised 3-7 days after ablation. Contrast-enhanced CT (n = 12) and magnetic resonance imaging (MRI) (n = 2) were performed after ablation of all percutaneously treated patients.

RESULTS

Tumors treated intraoperatively did not demonstrate definitive coagulative necrosis. However, pathologic abnormalities suggestive of tissue injury were observed with hematoxylin and eosin staining, and absent cytosolic and mitochondrial enzyme activity suggested irreversible cellular damage. In contrast, specimens removed > 3 days after ablation showed definite, contiguous coagulative necrosis without intervening areas of viable tumor. CT and MRI scans demonstrated circumscribed hypodense, nonenhancing regions surrounding the electrode tract as early as 15 minutes after ablation. These corresponded within 2 mm to measurements of coagulation at pathology.

CONCLUSIONS

RF ablation is a minimally invasive and safe approach to the treatment of tumors in the liver. Tumors treated with RF energy do not immediately demonstrate coagulative necrosis, but do show evidence of irreversible cellular damage. The extent of tumor necrosis correlates closely with findings at contrast-enhanced imaging.

Treatment of intrahepatic malignancy with radiofrequency ablation: radiologic-pathologic correlation

BACKGROUND

Radiofrequency (RF)-induced tissue coagulation represents a new approach for the thermal destruction of tumors within the liver. The purpose of the current study was to 1) assess technique safety; 2) determine the extent and evolution of induced cellular damage; and 3) correlate the observed pathologic effects with radiologic studies.

METHODS

Twenty-three tumors measuring </= 8 cm (19 colorectal metastases and 4 hepatomas) in 22 patients were treated with RF (range, 500-1550 milliamperes) using internally cooled electrodes. All treated tumors were resected to allow pathologic analysis. Eleven tumors were treated intraoperatively under ultrasonographic guidance and excised immediately. Twelve tumors were treated percutaneously using ultrasound or computed tomography (CT) guidance and subsequently were excised 3-7 days after ablation. Contrast-enhanced CT (n = 12) and magnetic resonance imaging (MRI) (n = 2) were performed after ablation of all percutaneously treated patients.

RESULTS

Tumors treated intraoperatively did not demonstrate definitive coagulative necrosis. However, pathologic abnormalities suggestive of tissue injury were observed with hematoxylin and eosin staining, and absent cytosolic and mitochondrial enzyme activity suggested irreversible cellular damage. In contrast, specimens removed > 3 days after ablation showed definite, contiguous coagulative necrosis without intervening areas of viable tumor. CT and MRI scans demonstrated circumscribed hypodense, nonenhancing regions surrounding the electrode tract as early as 15 minutes after ablation. These corresponded within 2 mm to measurements of coagulation at pathology.

CONCLUSIONS

RF ablation is a minimally invasive and safe approach to the treatment of tumors in the liver. Tumors treated with RF energy do not immediately demonstrate coagulative necrosis, but do show evidence of irreversible cellular damage. The extent of tumor necrosis correlates closely with findings at contrast-enhanced imaging.

Variables affecting proper system grounding for radiofrequency ablation in an animal model

PURPOSE

The authors sought to determine which factors contribute to excessive thermal deposition and burns at the grounding pad site after high-current percutaneous, image-guided radiofrequency (RF) ablation.

MATERIALS AND METHODS

Radiofrequency (1,000-2,000 mA) was applied for 10 minutes with use of an internally-cooled electrode placed into in vivo pig livers (n = 88). In separate experiments, the number of pads (1, 2, or 4), orientation of pads (horizontal, vertical, or diagonal), and distance between the pads and the electrode (10-50 cm) of mesh or foil grounding pads (12.5 x 8 cm; 100 cm2) were varied. Thermistors measured skin surface temperatures during ablation. Pathologic analysis of skin changes was performed.

RESULTS

Temperature elevations at the grounding pad were observed for every trial, with a temperature elevation > or =12 degrees C (as high as 45 degrees C) observed in 60 of 88 trials (68.2%). Temperatures at the grounding site pad were dependent on all variables studied, including the grounding pad surface area, the amount of current deposited in the liver, the orientation of the pad, and the pad's distance from the electrode. Second-degree burns were seen with temperatures exceeding 47 degrees C and third-degree burns were observed when a temperature > or = 52 degrees C was noted. For a given set of RF parameters, reduced heating was observed for trials in which foil grounding pads were used (P < .001). Grounding pad burns did not occur at 2,000 mA (maximum generator output) when four foil pads were placed horizontally > or = 25 cm from the electrode.

CONCLUSIONS

High-current RF ablation can induce severe burns at the grounding pad site if inadequate precautions are taken. To minimize the risk of burns, multiple large-surface-area foil pads should be placed on well-prepared skin and oriented with the longest surface edge facing the RF electrode.

Helical CT protocols for the abdomen and pelvis: a survey

OBJECTIVE

We surveyed members of the Society of Computed Body Tomography/Magnetic Resonance to evaluate current techniques used for helical CT in the abdomen and pelvis.

MATERIALS AND METHODS

The survey was distributed to 70 members (36 institutions) of the Society of Computed Body Tomography/Magnetic Resonance. The survey included general questions related to abdominal and pelvic helical CT and also asked the members to write a protocol for 12 hypothetical requisitions.

RESULTS

Thirty-two members (46%) responded, representing 28 institutions (78%). The number of protocols for helical CT of the abdomen and pelvis at each institution ranges from 2 to 35 (median, 11). IV contrast material is administered for 90% (median) of abdominal and pelvic CT examinations. Nonionic contrast material is used for 68% (median) of these examinations. IV contrast material is used by 100% of institutions for tumor staging protocols except for one institution that does not use IV contrast material for lymphoma staging. Fifty percent of the institutions obtain two- or three-phases of liver images for breast cancer staging. For all protocols, the average collimation and reconstruction interval is 7 mm except for renal (5 mm) and adrenal (4 mm) protocols. Rectal contrast material is administered most commonly for colon cancer staging (39% of institutions).

CONCLUSION

There is a wide range in the number of protocols used for helical CT in the abdomen and pelvis among the responding institutions. Most protocols include use of nonionic IV contrast material injected at a rate of 3 ml/sec and a collimation of 7 mm.

Representing both first- and second-order uncertainties by Monte Carlo simulation for groups of patients

Actual implementation of probabilistic sensitivity analysis may lead to misleading or improper conclusions when it is applied to groups of patients rather than individual patients. The practice of combining first- and second-order simulations when modeling the outcome for a group of more than one patient yields an erroneous marginal distribution whenever the parameter values are randomly sampled for each patient while the results are presented as simulated means for the group of patients. This practice results in underrepresenting the second-order uncertainty. It may also distort the shape (especially the symmetry or extent of the tails) in the simulated distribution. As a result, it may lead to premature or incorrect conclusions of superiority. It may also result in inappropriate estimates of the value of further research to inform parameter values.

Screening for colorectal cancer

Colorectal cancer is the third most commonly diagnosed cancer and the second leading cause of cancer deaths in the United States. Fortunately, both the incidence and mortality associated with the disease have declined during the past 2 decades. This is likely due, at least in part, to improved efforts at screening and more aggressive removal of adenomatous polyps. However, colorectal cancer screening is still generally underutilized. This article reviews the current status and future outlook for colorectal cancer screening, including a discussion of risk factors for the disease, its anatomic distribution, proposed mechanisms of development from adenomatous polyps, rationale for screening, and screening options. Published literature concerning the cost-effectiveness of colorectal cancer screening is also summarized. The article concludes with a discussion of the emerging consensus regarding the importance of and approaches to screening.

Hepatocellular carcinoma: radio-frequency ablation of medium and large lesions

PURPOSE

To study local therapeutic efficacy, side effects, and complications of radio-frequency (RF) ablation in the treatment of medium and large hepatocellular carcinoma (HCC) lesions in patients with cirrhosis or chronic hepatitis.

MATERIALS AND METHODS

One-hundred fourteen patients who were under conscious sedation or general anesthesia had 126 HCCs greater than 3.0 cm in diameter treated with RF by using an internally cooled electrode. Eighty tumors were medium (3.1-5.0 cm), and 46 were large (5.1-9.5 cm). The mean diameter for all tumors was 5.4 cm. At imaging, 75 tumors were considered noninfiltrating, and 51 were considered infiltrating.

RESULTS

Complete necrosis was attained in 60 lesions (47.6%), nearly complete (90%-99%) necrosis in 40 lesions (31.7%), and partial (50%-89%) necrosis in the remaining 26 lesions (20.6%). Medium and/or noninfiltrating tumors were treated successfully significantly more often than large and/or infiltrating tumors. Two major complications (death, hemorrhage requiring laparotomy) and five minor complications (self-limited hemorrhage, persistent pain) were observed. The single death was due to a break in sterile technique rather than to the RF procedure itself.

CONCLUSION

RF ablation appears to be an effective, safe, and relatively simple procedure for the treatment of medium and large HCCs.

Radio-frequency-induced coagulation necrosis in rabbits: immediate detection at US with a synthetic microsphere contrast agent

PURPOSE

To determine whether a synthetic ultrasonographic (US) contrast agent can be used to differentiate coagulation necrosis from untreated tumor immediately after radio-frequency ablative therapy.

MATERIALS AND METHODS

VX2 (adenocarcinoma) tumors (0.8-1.5-cm diameter) were implanted into 12 rabbits. Gray-scale and color Doppler US were performed with or without intravenous injection of a US contrast agent composed of poly-lactide-co-glycolic acid polymeric (PLGA) microspheres (2-micron diameter) filled with perfluorocarbon gas. Radio frequency was applied to each nodule for 6 minutes at 127 mA +/- 33 (mean +/- SD) (tip temperature, 92 degrees C +/- 2). Repeat US with a second dose of the contrast agent was performed immediately after ablation. In four animals, a third dose was administered 30-120 minutes after ablation. Radiologic-histopathologic correlation was performed and included in vivo staining and studies of mitochondrial function.

RESULTS

Intense contrast agent enhancement was seen throughout the tumor prior to ablation. At gray-scale US, ablation produced hyperechoic foci, which were within 1 mm of the foci identified at histopathologic examination in seven of 12 animals (58%). After the administration of contrast material, foci devoid of previously visualized enhancement, which measured 7.3-15.0 mm, were identified. These were within 1 mm of the size of the foci identified at histopathologic examination in 11 of 12 animals (92%, P < .01). In two animals, enhancement depicted viable tumor, which appeared hyperechoic, on nonenhanced images. On delayed images, hyperechoic areas decreased in size, whereas the nonenhanced region remained unchanged.

CONCLUSION

A PLGA microspherical US contrast agent enabled the immediate detection of coagulation necrosis as a region devoid of contrast enhancement after radio-frequency ablation in rabbit hepatic tumors. Therefore, this agent could provide real-time guidance during complex ablative procedures and may provide an efficient technique for postprocedural assessment.

EUS-guided radiofrequency ablation in the pancreas: results in a porcine model

BACKGROUND

Our aim in this study was to investigate the feasibility and safety of performing radiofrequency (RF) ablation in the pancreas with endoscopic ultrasound (EUS).

METHODS

RF was applied to normal pancreatic tissue in 13 anesthetized Yorkshire pigs with specially modified 19-gauge needle electrodes (1.0 to 1.5 cm tip). The pancreas was localized with EUS and punctured through a transgastric approach. RF current (285 +/- 120 mA) was delivered for 6 minutes. Diagnostic imaging (EUS and CT) and serum amylase and lipase levels were obtained at baseline, immediately after ablation, and 1 to 14 days after the procedure. Pigs were killed immediately (n = 5), 1 to 2 days after ablation (n = 2), and 2 weeks after the procedure (n = 6). Pathologic examination was performed.

RESULTS

Sixteen ablations were performed. During ablation, round hyperechoic foci (diameter to 1.0 cm) gradually surrounded the tip of the electrode. Immediately after the procedure CT demonstrated 1 cm hypodense foci that did not enhance with iodinated contrast. In pigs killed immediately and 1 to 2 days after ablation, pathologic examination showed discrete, well-demarcated spherical foci of coagulation necrosis measuring 8 to 12 mm in diameter surrounded by a 1 to 2 mm rim of hemorrhage. Radiologic-pathologic correlation was within 2 mm. In 4 of 6 (67%) pigs killed on day 14, retraction of the coagulated focus was observed. A 1 to 3 mm fibrotic capsule surrounded the coagulated tissue in the remaining 2 pigs. One pig had mild hyperlipasemia, a focal zone of pancreatitis (<1 cm), and later a pancreatic fluid collection. Biochemical parameters were normal in the remaining pigs. Other complications included three gastric and one intestinal burn caused by improper electrode placement.

CONCLUSIONS

EUS-guided RF ablation can be used safely to produce discrete zones of coagulation necrosis in the porcine pancreas. Potential clinical uses of this technology include management of small neuroendocrine tumors and possibly palliation of unresectable pancreatic adenocarcinoma.

Percutaneous radiofrequency tissue ablation: optimization of pulsed-radiofrequency technique to increase coagulation necrosis

PURPOSE

To develop a computerized algorithm for pulsed, high-current percutaneous radiofrequency (RF) ablation, which maximally increases the extent of induced coagulation necrosis.

MATERIALS AND METHODS

An automated, programmable algorithm for pulsed-RF deposition was designed to permit high-current deposition by periodically reducing current for 5-30 seconds during RF application. Two strategies for pulsed-RF deposition were evaluated: (i) constant peak current (900-1,800 mA) of variable duration and (ii) variable peak current (1,200-2,000 mA) for a specified minimum duration. The extent of induced coagulation was compared to results obtained with continuous (lower current) RF application. Trials were performed in ex vivo calf liver (n = 115) and in vivo porcine liver (n = 30) and muscle (n = 18) with use of 2-4-cm tip, internally cooled electrodes.

RESULTS

For 3-cm electrodes in ex vivo liver, applying pulsed-RF with constant peak current for 12 minutes produced 3.5 cm +/- 0.2 of necrosis. Greater necrosis was produced with use of the variable current strategy, in which 4.5 cm +/- 0.2 of coagulation was achieved with use of an initial current > or =1,500 mA (minimum peak-RF duration of 10 sec, with 15 sec of reduced current to 100 mA between peaks; P < .01). This variable peak current algorithm also produced 3.7 cm +/- 0.6 of necrosis in in vivo liver, and 6.5 cm +/- 0.9 in in vivo muscle. Without pulsing, a maximum of 750 mA, 1,100 mA, and 1,500 mA could be applied in ex vivo liver, in vivo liver, and in vivo muscle, respectively, which resulted in 2.9 cm +/- 0.2, 2.4 cm +/- 0.2, and 5.1 cm +/- 0.4 of coagulation (P < .05, all comparisons).

CONCLUSIONS

A variable peak current algorithm for pulsed-RF deposition can increase coagulation necrosis diameter over other ablation strategies. This innovation may ultimately enable the percutaneous treatment of larger tumors.

Radio-frequency ablation of hepatic metastases: postprocedural assessment with a US microbubble contrast agent--early experience

PURPOSE

To evaluate contrast agent-enhanced ultrasonography (US) in the detection of untreated tumor after radio-frequency (RF) ablation of hepatic metastases.

MATERIALS AND METHODS

Twenty patients with solitary colorectal liver metastases underwent percutaneous RF tumor ablation. Pre- and postablation imaging was performed with nonenhanced and enhanced color and power Doppler US and contrast-enhanced helical computed tomography (CT). Initial follow-up CT and US were performed 24 hours after ablation. The findings at US and CT were compared.

RESULTS

Nonenhanced US demonstrated intratumoral signal in 15 of 20 metastases before ablation. This signal increased after contrast agent administration. Contrast-enhanced US performed 24 hours after ablation demonstrated residual foci of enhancement in three tumors, whereas no US signals were seen in any tumor on nonenhanced scans. CT demonstrated small (< 3-mm) persistent foci of residual enhancement in these three tumors and in three additional lesions that were not seen at US (US sensitivity, 50%; specificity, 100%; diagnostic agreement with CT, 85%). All six patients with evidence of residual tumor underwent repeat RF ablation.

CONCLUSION

Contrast-enhanced US may depict residual tumor after RF application and thereby enable additional directed therapy. The potential reduction in treatment sessions and/or ancillary imaging procedures might increase the ease and practicality of percutaneous ablation of focal hepatic metastases.

Small hepatocellular carcinoma: treatment with radio-frequency ablation versus ethanol injection

PURPOSE

To compare the effectiveness of radio-frequency (RF) ablation with that of percutaneous ethanol injection in the treatment of small hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Eighty-six patients with 112 small (< or = 3-cm-diameter) HCCs underwent RF ablation (42 patients with 52 tumors) or percutaneous ethanol injection (44 patients with 60 tumors). Therapeutic efficacy was evaluated with dual-phase spiral computed tomography performed at least 4 months after treatment.

RESULTS

Complete necrosis was achieved in 47 of 52 tumors with RF ablation (90%) and in 48 of 60 tumors with percutaneous ethanol injection (80%). These results were obtained with an average of 1.2 sessions per tumor with RF ablation and 4.8 sessions per tumor with percutaneous ethanol injection. One major complication (hemothorax that required drainage) and four minor complications (intraperitoneal bleeding, hemobilia, pleural effusion, cholecystitis) occurred in patients treated with RF ablation; no complications occurred in patients treated with percutaneous ethanol injection.

CONCLUSION

RF ablation results in a higher rate of complete necrosis and requires fewer treatment sessions than percutaneous ethanol injection. However, the complication rate is higher with RF ablation than with percutaneous ethanol injection. RF ablation is the treatment of choice for most patients with HCC.

Pharmacokinetics, safety, and tolerability of gadoversetamide injection (OptiMARK) in subjects with central nervous system or liver pathology and varying degrees of renal function

The pharmacokinetic parameters, safety, and tolerability of OptiMARK (gadoversetamide injection), a gadolinium-based magnetic resonance imaging (MRI) contrast agent, were evaluated in 163 subjects with either central nervous system (CNS) or liver pathology with and without renal insufficiency, for which a contrast-enhanced MRI was indicated. A multicenter, double-blind, randomized, placebo-controlled, parallel-group design was used in which subjects received 0.1, 0.3, or 0.5 mmol/kg of OptiMARK or placebo intravenously. Samples were analyzed for total gadolinium by inductively coupled plasma/mass spectrometry. Gadolinium pharmacokinetics were affected by renal impairment: area under the curve, half-life, and steady-state distribution volume significantly increased with declining renal function, while total body clearance decreased. In subjects with normal renal function, neither age, gender, nor liver versus CNS pathology altered gadolinium pharmacokinetics. No clinically significant changes from baseline were noted in vital signs, laboratory measures, electrocardiograms, or physical examinations. OptiMARK is safe and well-tolerated following a single intravenous injection in subjects with either liver or CNS pathology despite a prolonged elimination half-life in subjects with renal impairment.

Radio-frequency tissue ablation: effect of pharmacologic modulation of blood flow on coagulation diameter

PURPOSE

To determine whether vasoactive pharmacologic agents can alter radio-frequency (RF)-induced coagulation necrosis by modulating hepatic blood flow.

MATERIALS AND METHODS

RF ablation was performed in normal, in vivo porcine liver with 1.5-cm internally cooled electrodes and a standardized RF application (i.e., 500 mA for 10 minutes). Ablation was performed without (n = 9) and with pharmacologic modulation of blood flow with halothane (n = 7), vasopressin (n = 6), or epinephrine (n = 7). Laser Doppler techniques were used to quantify changes in hepatic blood flow. Remote thermometry was also performed. Blood flow was correlated with both induced coagulation necrosis and tissue temperatures.

RESULTS

Halothane reduced mean blood flow (+/- SD) to 46.1% +/- 8.5 of normal, and vasopressin increased mean blood flow to 132.7% +/- 13.9. Epinephrine caused increased hepatic blood flow centrally (171.1% +/- 31.7) but not peripherally (102.8% +/- 15.4). Mean coagulation diameter was 1.4 cm +/- 0.3 with vasopressin, 2.2 cm +/- 0.4 with normal blood flow, and 3.2 cm +/- 0.1 with halothane (P < .01). After epinephrine infusion, mean coagulation measured 2.3 cm +/- 0.3 peripherally and 1.4 cm +/- 0.5 centrally (P < .01). A linear correlation between coagulation diameter and blood flow was demonstrated (r2 = 0.78). Temperatures 10 and 15 mm from the electrode correlated with both blood flow and coagulation diameter (r2 = 0.65 and 0.60, respectively).

CONCLUSION

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.

Large-volume tissue ablation with radio frequency by using a clustered, internally cooled electrode technique: laboratory and clinical experience in liver metastases

PURPOSE

To evaluate whether coagulation necrosis achievable with radio-frequency (RF) ablation can be increased by using a cluster of closely spaced electrodes.

MATERIALS AND METHODS

RF was applied to ex vivo liver (n = 68), in vivo liver (n = 12), and in vivo muscle (n = 15) by using a cluster array of three separate internally cooled electrodes spaced 0.5 cm apart. The diameter of coagulation necrosis achieved with optimal RF deposition (1,400-2,150 peak mA) for 5-60 minutes of RF application was determined for electrode tip lengths of 1.5-3.0 cm and compared with that obtained by using a single electrode and otherwise similar technique. Ten patients with solitary intrahepatic colorectal metastases were also treated by using cluster electrode RF ablation.

RESULTS

In ex vivo liver, simultaneous RF application to electrode clusters for 15, 30, and 45 minutes produced 4.7 cm +/- 0.1, 6.2 cm +/- 0.1, and 7.0 cm +/- 0.2 of coagulation necrosis, respectively. In in vivo liver and muscle, RF applied to electrode clusters for 12 minutes yielded 3.1 cm +/- 0.2 and 7.6 cm +/- 0.4 of coagulation, respectively. RF application to a single electrode produced maximal coagulation of 2.9 cm in ex vivo liver, 1.8 cm in in vivo liver, and 4.3 cm in muscle (P < .01, all tissues). In colorectal metastases, a single 12-15-minute application of RF to an electrode cluster induced 4.5-7.0 cm of coagulation necrosis.

CONCLUSION

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.

Benign prostatic hyperplasia: US-guided transrectal urethral enlargement with radio frequency--initial results in a canine model

PURPOSE

To enlarge the prostatic urethra with thermal coagulation with transrectal radio-frequency (RF) application in dogs.

MATERIALS AND METHODS

Eight aged dogs underwent RF ablation of periurethral prostatic tissue for 6 minutes. Eighteen-gauge electrodes were placed into the periurethral tissues with a transrectal approach and ultrasound (US) guidance. Prostatic and rectal temperatures were measured during RF application. US, conventional and computed tomographic (CT) retrograde urethrography (RUG), and CT were performed immediately (n = 8) and at 3-96 days (n = 6) after ablation. Histopathologic analysis was performed at sacrifice immediately (n = 2), at 28 days (n = 2), or at 3 months (n = 4) after treatment.

RESULTS

All procedures were successful with no complications and were performed in less than 30 minutes. Rectal mucosal temperature did not exceed 38 degrees C. Immediately after treatment, CT and US demonstrated 1.2-cm foci of altered periurethral tissue that corresponded to solid coagulated tissue at histopathologic analysis. By day 3, CT, RUG, and US demonstrated that these foci had begun to cavitate, resulting in enlargement of the urethra. Complete cavitation was demonstrated by day 28. Minimal reduction in the degree of urethral enlargement was noted by day 60, but narrowing, urethral strictures, or fistulas were not observed at 3 months. At histopathologic analysis, focal cavitary enlargement with at least doubling of the urethral diameter and with normal urothelium was noted in all dogs surviving at least 28 days.

CONCLUSION

Transrectal RF urethral enlargement is feasible and safe in animals and merits investigation for alleviating urethral obstruction due to benign prostatic hyperplasia.

Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature

OBJECTIVE

Unenhanced CT scanning can reliably characterize incidentally detected adrenal masses when observers use density measurements of the adrenal gland. However, controversy exists as to the optimal density threshold required to differentiate benign from malignant lesions. This study attempts to establish a consensus by performing a pooled analysis of data found in the CT literature.

MATERIALS AND METHODS

Ten CT reports were analyzed, from which individual adrenal lesion density measurements were obtained for 495 adrenal lesions (272 benign lesions and 223 malignant lesions). Threshold analysis generated a range of sensitivities and specificities for lesion characterization at different density thresholds.

RESULTS

Sensitivity for characterizing a lesion as benign ranged from 47% at a threshold of 2 H to 88% at a threshold of 20 H. Similarly, specificity varied from 100% at a threshold of 2 H to 84% at a threshold of 20 H.

CONCLUSION

The attempt to be absolutely certain that an adrenal lesion is benign may lead to an unacceptably low sensitivity for lesion characterization. The threshold chosen will depend on the patient population and the cost-benefit approach to patient care.

Asymptomatic hydropneumothorax after therapeutic thoracentesis for malignant pleural effusions

OBJECTIVE

The purpose of this study was to document in a historical cohort the incidence and clinical observations of pneumothorax ex vacuo after therapeutic thoracentesis for malignant pleural effusions in patients with underlying parenchymal lung disease.

MATERIALS AND METHODS

Forty pneumothoraces resulted from 512 therapeutic thoracentesis performed for malignant pleural effusions over a 3-year period. Twenty-nine patients with pneumothoraces underwent catheter placement in the pleural space for treatment. Of these, 12 pneumothoraces resolved and 17 remained unchanged. We reviewed the charts of these 17 patients to document the cause of malignant pleural effusion, presence of underlying malignant parenchymal disease, volume of fluid aspirated, and improvement in symptoms. Clinical outcome was then evaluated, including size of residual pneumothorax, duration of catheter drainage, and reaccumulation of effusion.

RESULTS

No patients' lungs reexpanded despite insertion of large-bore (16- to 35-French) chest tubes. All had pneumothoraces that occupied at least 30% of the hemithorax; all were asymptomatic; all had underlying parenchymal disease and noncompliant lungs. Pleural effusion reaccumulated in all 17 after removal of the chest tube.

CONCLUSION

A subgroup of patients with malignant lung parenchymal disease who undergo therapeutic thoracentesis will develop asymptomatic hydropneumothoraces due to poor lung compliance. These patients do not require further catheter drainage. Pleural effusion will reaccumulate in the residual space over a variable period of time.

Radio-frequency-induced thermoablation: monitoring with T1-weighted and proton-frequency-shift MR imaging in an interventional 0.5-T environment

PURPOSE

To evaluate the feasibility and accuracy of monitoring radio-frequency (RF) ablation with an open-configuration, 0.5-T magnetic resonance (MR) imager.

MATERIALS AND METHODS

Thirty-six in vivo RF ablation experiments were performed in porcine paravertebral muscle (n = 24) and liver (n = 12). A 90 degrees C tip temperature was applied for 3-9 minutes. MR images were acquired after continuous or during intermittent RF application. Temperature changes were monitored as signal intensity and proton-frequency-shift (PFS) alterations in two T1-weighted gradient-echo sequences. An update image was obtained every 2.5 seconds (20/10 [repetition time msec/echo time [TE] msec]) or every 5.0 seconds (40/20). A color-coded subtraction technique enhanced the signal intensity and PFS changes. Macroscopic coagulation size was compared with MR image lesion size.

RESULTS

The RF application mode had no significant effect on coagulation size in muscle or liver (P > .05). Twenty-two of 24 coagulative lesions in muscle and nine of 12 in liver were demonstrated with the PFS technique. Accuracy of lesion size determination depended on TE (TE = 20 msec, r = .95; TE = 10 msec, r = .78 [P < .01]). The T1-weighted technique depicted only six of 24 muscle and three of 12 liver lesion ablations. In the lesions depicted, macroscopic size was significantly underestimated (P < .001).

CONCLUSION

PFS MR monitoring of RF effects in liver and muscle is feasible and accurate. The PFS technique outperformed the T1-weighted technique.

Percutaneous radiofrequency tissue ablation: does perfusion-mediated tissue cooling limit coagulation necrosis?

PURPOSE

To determine, by decreasing hepatic perfusion during radiofrequency (RF) ablation, whether perfusion-mediated tissue cooling can explain the reduced coagulation observed in in vivo studies compared to that seen with RF application in ex vivo tissue.

MATERIALS AND METHODS

RF was applied in vivo with use of cooled-tip electrodes to normal porcine liver without (n = 8) and with balloon occlusion of the portal vein (n = 8), celiac artery (n = 3), or hepatic artery (n = 2), and to ex vivo calf liver (n = 10). In vivo trials of vasopressin (0.3-0.6 U/min) infusion during RF application with (n = 10) and without (n = 2) arterial balloon occlusion were also performed. Intraoperative RF was subsequently performed in seven patients with hepatic colorectal metastases with and without portal inflow occlusion. Remote thermometry was performed in four patients.

RESULTS

RF application (12 minutes) during portal venous occlusion produced larger areas of coagulation necrosis than RF with unaltered blood flow (2.9 cm +/- 0.1 vs 2.4 cm +/- 0.2 diameter; P < .01). With celiac and hepatic artery occlusion, coagulation diameter measured 2.7 cm +/- 0.2 and 2.5 cm +/- 0.1, respectively. Infusion of vasopressin without vascular occlusion reduced coagulation diameter to 1.1 cm. However, different methods of hepatic or celiac arterial balloon occlusion with simultaneous vasopressin infusion produced a mean 3.4 cm +/- 0.2 of necrosis. Coagulation in ex vivo liver was 2.9 cm +/- 0.1 in diameter. Clinical studies demonstrated greater coagulation diameter for metastases treated during portal inflow occlusion (4.0 cm +/- 1.3) than for tumors treated with normal blood flow (2.5 cm +/- 0.8; P < .05). Thermometry documented a 10 degrees C increase compared to baseline at 10 mm and 20 mm from the electrode after 5 minutes of portal inflow occlusion during constant RF application.

CONCLUSIONS

Perfusion-mediated tissue cooling reduces coagulation necrosis achievable with RF ablation. Reduction of blood flow during RF application increases coagulation in both an animal model and human liver metastases.