Complications and management of microwave coagulation therapy for primary and metastatic liver tumors

Treatment of a huge biloma complicating curative radiofrequency ablation of hepatocellular carcinoma: a case report

Development of a huge intrahepatic biloma after radiofrequency ablation (RFA) is a rare complication. We report a patient with hepatocellular carcinoma (HCC) who had been treated by RFA and was complicated by a huge biloma. The biloma was cured by percutaneous catheter drainage and endoscopic retrograde cholangiopancreatography. A plastic stent was placed from the duodenal ampulla to the common bile duct to lower the pressure. The catheter and the stent were removed within 1 month after the biloma had disappeared. There was no recurrence of the biloma and HCC lesions with a follow-up time of 2 years. The present case is one of the best reported outcomes after development of a huge biloma.

Microwave ablation combined with transcatheter arterial chemoembolization is effective for treating unresectable hepatoblastoma in infants and children

The present study is to evaluate the feasibility and efficacy of microwave ablation (MWA) combined with transcatheter arterial chemoembolization (TACE) in the treatment for unresectable hepatoblastoma in infants and children. A total of 17 patients with PRETEXT stage III and IV hepatoblastoma that was unresectable by conventional resection were included in the present study. The patients were treated with TACE, MWA, and chemotherapy. All cases were diagnosed by computed tomography (CT) and liver tumor biopsy before TACE procedure. All patients received 2 courses of TACE and 1 to 2 times of MWA. Finally, several cycles of chemotherapy were arranged. Among the 17 patients, 14 were alive and had normal alpha-fetoprotein (AFP) levels. The other 3 patients died from tumor progression. The follow-up periods ranged from 10 to 68 months. Complete ablation was achieved in the 14 patients (14/17, 82.35%). Most patients were well tolerated during the whole course except for 1 patient with pneumonedema after TACE and another 1 with biloma after MWA. No marked chemotherapeutic agent-induced toxicity occurred. After chemotherapy or TACE, transient blood indicators and symptoms were observed as follows: myelosuppression, abnormal liver function, gross hematuria, fever, and abdominal pain. Transient symptoms after MWA were fever, abdominal pain, and massive gross hematuria. The present study demonstrates that MWA combined with TACE is a safe and effective method for treating unresectable hepatoblastoma in infants and children with controllable side effects.

Stereotactically navigated percutaneous microwave ablation (MWA) compared to conventional MWA: a matched pair analysis

PURPOSE

To compare CT-navigated stereotactic microwave ablation (SMWA) to non-navigated conventional MWA (CMWA) for percutaneous ablation of liver malignancies.

METHODS

A matched pair analysis of 36 patients who underwent MWA of primary or secondary liver malignancies (10 hepatocellular carcinoma and 8 metastases) was conducted. A total of 18 patients undergoing SMWA were included in this prospective study. Patients were matched in terms of tumor size, liver segment and entity to retrospective CMWA procedures. The endpoints were procedure time, accuracy of needle placement, technical success rate, complication rate and dose-length product (DLP).

RESULTS

The procedure durations were 23.9 min (SD 3.7) for CMWA and 21.8 min (SD 16.3) for SMWA (p = 0.22). The procedural accuracy for SMWA and CMWA was identical for both groups (3.7 mm). The total DLP was significantly lower for SMWA than for CMWA (2115 mGy cm (SD 276) vs. 3109 mGy cm (SD 1137), respectively; p < 0.01). Complete ablation without residual tumor was observed in 94% (17 of 18) of SMWA and in 83% (15 of 18) of CMWA patients (p = 0.31). No complications occurred.

CONCLUSIONS

SMWA is highly accurate and reduces the radiation dose without increasing the procedure time.

Robot-assisted microwave thermoablation of liver tumors: a single-center experience

PURPOSE

To evaluate and compare the needle placement accuracy, patient dose, procedural time, complication rate and ablation success of microwave thermoablation using a novel robotic guidance approach and a manual approach.

METHODS

We performed a retrospective single-center evaluation of 64 microwave thermoablations of liver tumors in 46 patients (10 female, 36 male, mean age 66 years) between June 2014 and February 2015. Thirty ablations were carried out with manual guidance, while 34 ablations were performed using robotic guidance. A 6-week follow-up (ultrasound, computed tomography and MRI) was performed on all patients.

RESULTS

The total procedure time and dose-length product were significantly reduced under robotic guidance (18.3 vs. 21.7 min, [Formula: see text]; 2216 vs. 2881 mGy[Formula: see text]cm, [Formula: see text]). The position of the percutaneous needle was more accurate using robotic guidance (needle deviation 1.6 vs. 3.3 mm, [Formula: see text]). There was no significant difference between both groups regarding the complication rate and the ablation success.

CONCLUSION

Robotic assistance for liver tumor ablation reduces patient dose and allows for fast positioning of the microwave applicator with high accuracy. The complication rate and ablation success of percutaneous microwave thermoablation of malignant liver tumors using either CT fluoroscopy or robotic guidance for needle positioning showed no significant differences in the 6-week follow-up.

Needle track seeding after percutaneous microwave ablation of malignant liver tumors under ultrasound guidance: analysis of 14-year experience with 1462 patients at a single center

OBJECTIVE

To determine the incidence and risk factors associated with needle tract seeding after percutaneous microwave ablation (MWA) of liver cancer under ultrasound guidance.

MATERIALS AND METHODS

Over a 14-year period, a total of 1462 patients with 2530 malignant nodules were treated by MWA. The influence of age, sex, Child-pugh classification, tumor size, tumor position, previous biopsy, insertion number and antenna type on the risk of neoplastic seeding was assessed. The survival of seeding patients after the MWA was analyzed.

RESULTS

Eleven patients with 12 nodules (0.47% per tumor, 0.75% per patient) were identified with needle tract seeding with an interval time of 6-37 (median 10) months after MWA. The mean size of the seeding nodule was 2.3 ± 0.7 cm (from 1.3 to 3.9 cm). Only previous biopsy was significantly associated with neoplastic seeding (P=0.02). All the seeding lesions were successfully treated by resection, MWA, radiation or high intensity focus ultrasound. The median survival period of the 11 patients after the MWA was 36.0 months. The cumulative survival rates of the 11 patients after the MWA at 1-, 2-, 3-, 4- and 5-year were 90.9%, 72.7%, 62.3%, 31.2% and 15.6%, respectively.

CONCLUSION

The results showed that the neoplastic seeding was a low risk complication of percutaneous MWA of liver cancer and was considered acceptable in general.

Partial response of hepatocellular carcinoma to percutaneous microwave ablation: risk factors and preventive measures

AIM: To investigate the risk factors and preventive measures for partial response of hepatocellular carcinoma to percutaneous microwave ablation.

METHODS: The clinical data for 465 patients with hepatocellular carcinoma (796 tumor nodules) who underwent percutaneous microwave ablation from October 2004 to June 2010 were retrospectively analyzed. The risk factors and preventive measures for partial response to percutaneous microwave ablation were summarized.

RESULTS: Partial response occurred in 48 patients (69 tumor nodules), and the overall partial response rate was 9.15% (69/754). Of these 48 patients, 45 (64 tumor nodules) underwent percutaneous microwave ablation again and achieved complete ablation in 93.94% (62/64) of tumor nodules; 1 (2 tumor nodules) received percutaneous ethanol injection and achieved successful ablation; and 2 received palliative surgery. The incidence of partial response was positively correlated with large tumor diameter, tumor location (at the hepatic hilum or near the diaphragm or hepatic capsule), multiple tumors, and ill-defined margins on ultrasound(all P < 0.01), and complete ablation was negatively correlated with previous treatment by TACE (3.60% vs 12.39%, P < 0.01). Multivariate analysis showed that tumor size, number of nodules, tumor location, and previous treatment by TACE were independent risk factors for partial response of hepatocellular carcinoma to percutaneous microwave ablation.

CONCLUSION: Large tumor size, multiple tumors, subcapsular lesion, and previous treatment by TACE are often associated with partial response of hepatocellular carcinoma to percutaneous microwave ablation. Percutaneous microwave ablation is an effective and safe method for treatment of partial response of hepatocellular carcinoma.

Biloma formation after radiofrequency ablation of hepatocellular carcinoma: incidence, imaging features, and clinical significance

OBJECTIVE

The objective of our study was to evaluate the frequency, morphologic patterns, temporal changes, and clinical significance of biloma after radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Between April 1999 and May 2008, 2,630 patients with HCC underwent a total of 3,284 sessions of RFA at our institution. We retrospectively reviewed all CT scans obtained before and after RFA in all patients. The frequency, morphologic patterns, temporal changes, and clinical course of biloma were studied at the thermal ablation zone after RFA.

RESULTS

A total of 109 bilomas (3.3%, 109/3,284) developed after RFA in 104 patients in our series. The bilomas developed from 0 to 526 days (mean, 64 days) after RFA, and the mean follow-up period was 469 days (range, 0-2,703 days). The most common morphologic type of biloma was a crescent shape (42.2%). The mean size of the bilomas at initial presentation was 3.8 cm (range, 1.7-11 cm), and the mean size of the bilomas on the last follow-up CT scan was 2.8 cm (range, 0-6.3 cm). Fifty-three (48.6%) of the 109 bilomas resolved during follow-up at a mean interval of 286 days. In one patient, the biloma was considered a major complication because percutaneous drainage was required to manage the biloma with infection (0.9%, 1/109). No patient died of a biloma.

CONCLUSION

The development of a biloma after percutaneous RFA in patients with HCC was not rare. However, in most cases they were a minor complication of no clinical significance.

Liver ablation techniques: a review

BACKGROUND

Ablation techniques for unresectable liver carcinomas have evolved immensely since their introduction. Results of studies involving these techniques are restricted to reports of patient case series, which are often not presented in a standardised manner. This review aims to summarise the major studies in ablation technologies and present them in a way that may make comparison between the major modalities easier.

METHODS

All major databases (Medline, Cochrane, Embase and Pubmed) were searched for studies using microwave, radiofrequency or cryoablation to treat unresectable liver tumours. Only studies with at least 30 patients and 3-year follow-up were included. Complication, recurrence and survival rates of all studies are summarised and presented.

RESULTS AND CONCLUSION

It is difficult to compare ablation modalities, as probe design and energy sources have evolved rapidly over the last decade. Ablation offers an invaluable palliative option and in some cases it may offer rates of cure approaching that of surgical resection with lower morbidity and mortality. Perhaps the time has come, therefore, for prospective large-scale randomised control trials to take place comparing ablation modalities to each other and surgical resection.

Efficacy and safety of microwave ablation for primary and secondary liver malignancies: a systematic review

This article reviews the therapeutic efficacy and complications of microwave ablation (MWA) in the treatment of primary and secondary liver malignancies. A PubMed search using keywords 'microwave', 'liver', 'malignancy', 'cancer' and 'tumour' was performed to identify articles related to MWA of liver malignancies published in English from 1975 to February 2008. MWA is an effective treatment options for both primary and secondary liver malignancies with survivals comparable with those of liver resections. Local recurrences can be managed with further ablation. Small tumour size, well-differentiated tumour and a reduced number of lesions are factors associated with good prognosis. Temporary occlusion of the portal venous and hepatic arterial flow may increase the size of ablation but the safety aspect requires further validation. MWA is a minimally invasive technique that has broadened the therapeutic option for patients with conventionally unresectable liver tumours with promising survival data. Future advances in the applicator design and treatment monitoring may further improve its efficacy and widen the indications.

Comparison of therapeutic effects between radiofrequency ablation and percutaneous microwave coagulation therapy for small hepatocellular carcinomas

BACKGROUND

Although thermal ablation therapies have gained fairly wide acceptance as an effective treatment for small hepatocellular carcinoma (HCC), there have been only a few clinical studies comparing the response to radiofrequency ablation (RFA) and percutaneous microwave coagulation therapy (PMCT). We evaluated the therapeutic efficacy and safety of these two procedures for the treatment of small HCC measuring < or = 2 cm in diameter.

METHODS

Thirty-four patients who had 37 nodules were treated by RFA and were compared with 49 patients (56 nodules) who underwent PMCT. Treatment was repeated until complete tumor necrosis was confirmed by contrast computed tomography (CT) scanning. The therapeutic efficacy and complications were retrospectively compared between the two procedures.

RESULTS

(i) There were significantly fewer treatment sessions (P < 0.001) in the RFA group than in the PMCT group, but the necrotic area was significantly larger (P < 0.001) in the former group. (ii) The local recurrence rate was significantly lower (P = 0.031) after RFA than after PMCT, although the ectopic recurrence rate showed no significant difference. (iii) The cumulative survival rate was significantly higher (P = 0.018) after RFA than after PMCT. (iv) The incidence of pain and fever after treatment was significantly higher in the PMCT group. Bile duct injury, pleural effusion, and ascites were also significantly more common in the PMCT group.

CONCLUSIONS

RFA is more useful than PMCT for the treatment of small HCC because it is minimally invasive and achieves a low local recurrence rate, high survival rate, and extensive necrosis after only a few treatment sessions.

Simultaneous microwave ablation using multiple antennas in explanted bovine livers: relationship between ablative zone and antenna

PURPOSE

Our purpose was to determine the optimal antenna spacing to achieve large ablative zones without indentations when microwave ablation is performed with simultaneous activation of two or three antennas.

MATERIALS AND METHODS

Microwave ablation was performed with single-antenna activation and simultaneous activation of two or three antennas with a spacing of 1.5, 2.0, 2.5, or 3.0 cm in explanted bovine livers. Microwave energy was applied for 10 min with a power of 45 W. The shapes and sizes of the ablative zones created were recorded and compared.

RESULTS

The shape of the ablative zone was ellipsoid in the axial plane (along the antenna axis) and spherical in the transverse plane (perpendicular to the antenna axis) in single-antenna ablation. The ablative zones were spherical or ellipsoid in both the axial and transverse planes in two-and three-antenna ablation with an antenna spacing of 2.0 cm or less. Indentations were observed between the ablative zones created by the antennas when the spacing was 2.5 cm or more, reducing the minimum transverse diameter. When two-or three-antenna ablation was performed with a spacing of 2.0 cm or less, the axial and minimum transverse diameters were significantly larger than in single-antenna ablation. The largest volume (almost two or three times the single-activation volume) was achieved in two-or three-antenna ablation with an antenna spacing of 2.0 cm.

CONCLUSION

We found that simultaneous microwave ablation using multiple microwave antennas creates large ablative zones without indentations when multiple antennas are activated with an antenna spacing of 2.0 cm or less.

Inoperable colorectal liver metastases: a declining entity?

BACKGROUND

Untreated colorectal liver metastases (CLMs) have a dismal prognosis. Surgery remains the gold standard of treatment, but many patients will have inoperable disease at presentation. Until recently, the outlook for such patients was bleak. The purpose of this review was to report on available options in the treatment CLMs, which would be considered unresectable by conventional evaluation.

METHODS

Inclusion criteria were articles published in English-language journals reporting on either retrospective or prospective cohorts of patients undergoing treatment for conventionally inoperable CLM. Main outcome measures were survival, resectability rates, morbidity and mortality following treatment of the patients' disease.

RESULTS

Improved chemotherapy regimes and other innovative treatments have opened up new options for such patients and may even render conventionally inoperable disease resectable. The aim of treatment should be down-staging of metastases to achieve resectability, however, other treatments such as ablation may be also be used (either alone or in conjunction with resection).

CONCLUSION

A nihilistic attitude to the patient with seemingly inoperable liver metastases should be discouraged. Discussion of such patients at multi-disciplinary meetings is essential in order to plan and monitor treatments.

Prognostic factors and recurrence of small hepatocellular carcinoma after hepatic resection or microwave ablation: a retrospective study

PURPOSE

This study aims to analyze the long-term therapeutic results of small HCC less than 5 cm in diameter after microwave ablation (MA) or hepatic resection (HR) and choose factors that could predict metastasis and recurrence of small HCC.

MATERIALS AND METHODS

The metastasis and recurrence of 194 patients with one HCC less than 5 cm in diameter who underwent curative HR or MA between January 1995 and December 2004 were reviewed retrospectively; immunohistochemistry was used to analyze the expressions of VEGF, bFGF, and c-Met in HCC tissues. Posttreatment prognostic factors were evaluated by multivariate analysis using Cox's proportional hazards model. The variables included the expressions of these three proteins in HCC tissues, the clinical and pathologic characteristics of the patients.

RESULTS

The retrospective study showed that 1-, 3-, and 5-year disease-free survival rates of patients with single HCC of diameter <5 cm were 71.3, 57.0 and 32.5%, respectively. Furthermore, 1-, 3-, and 5-year disease-free survival rates of the patients in MA group and resection group were 72.8, 54.0 and 33.0%; 68.5, 60.0, and 25.6%, respectively. There was no significant difference in disease-free survival rates between these two groups. The result of multivariate analysis showed that differentiation degree of HCC and the expressions of VEGF and c-Met in HCC tissues could be as the independent prognostic factors affecting metastasis and recurrence in patients with small HCC, whereas the methods of therapy had no impact on prognosis.

CONCLUSIONS

The metastasis and recurrence rate after MA is similar to that after HR, and the methods of therapy do not affect the prognosis of small HCC. The metastasis and recurrence of patients with small HCC will differ depending on tumor differentiation, expressions of VEGF and c-Met in HCC tissues.

Microwave ablation of hepatocellular carcinoma

OBJECTIVE

This article reviews the basic principles, equipment, current therapeutic status and future trends of microwave ablation (MWA) in the treatment of hepatocellular carcinoma (HCC).

METHODS

All articles published in English on MWA or MWA as a treatment for HCC were identified with a PubMed search from the 1990s through June 2007. Papers were reviewed on the technical advances of MWA equipment and the clinical applications of MWA including indications, techniques, therapeutic outcomes, complications and combination therapies.

RESULTS

MWA has several advantages, including high thermal efficiency, higher capability of coagulating blood vessels, faster ablation time, and an improved convention profile. MWA can induce large ablation volumes and yield good local tumor control, especially for small HCC. Larger HCC can also be completely ablated by using more effective antenna or simultaneous application of multiple antennae. Long-term survival comparable to that of surgery was obtained for tumors measuring 4 cm or less. Associated complications appear to be low.

CONCLUSIONS

MWA is a promising minimally invasive technique for the treatment of HCC. Future advances are warranted to improve the therapeutic efficacy.

Liver cancer: increased microwave delivery to ablation zone with cooled-shaft antenna--experimental and clinical studies

PURPOSE

To prospectively investigate whether the ablation zone induced with microwaves could be increased by delivering greater energy with a cooled-shaft antenna.

MATERIALS AND METHODS

All studies were animal care and ethics committee approved. Written informed consent was obtained from all patients. Microwave ablation was performed by using a cooled-shaft antenna in 48 ex vivo and 12 in vivo experiments with porcine livers. The coagulation diameters achieved in different microwave ablation parameter groups (60-90 W for 5-25 minutes) were compared. Ninety patients (78 men, 12 women; mean age, 53 years; age range, 20-82 years) with 133 0.8-8.0-cm (mean, 2.7 cm +/- 1.5 [standard deviation]) primary or metastatic liver cancers were treated with the same microwave ablation technique. Complete ablation (CA) and local tumor progression (LTP) rates were determined. Generalized estimating equations were used to compare differences in tumor size, ablation zone diameter, and CA and LTP rates between different patient subgroups.

RESULTS

In the ex vivo livers, in vivo livers, and liver cancers, one application of microwave energy with 80 W for 25 minutes produced mean coagulation diameters of 5.6 x 7.4 cm, 3.5 x 5.9 cm, and 3.6 x 5.0 cm, respectively. Skin burn was not observed. CA rates in small (<or=3.0-cm), intermediate (3.1-5.0-cm), and large (5.1-8.0-cm) liver cancers were 94% (81 of 86), 91% (31 of 34), and 92% (12 of 13), respectively. During a mean follow-up period of 17.4 months, LTP occurred in seven (5%) treated cancers. There was a significant difference in LTP rate between the cirrhosis and no-cirrhosis groups (P = .03). Four patients had major complications.

CONCLUSION

Delivery of greater microwave energy with cooled-shaft antennas yielded large ablation zones in ex vivo and in vivo livers and in liver cancers. Effective local tumor control was achieved during one microwave ablation session.

Outcome after hepatic resection versus combined resection and microwave ablation for multiple bilobar colorectal metastases to the liver

BACKGROUND

We investigated the efficacy of microwave ablation plus hepatectomy for multiple bilobar colorectal metastases to the liver. No consensus exists concerning local ablation plus hepatic resection for treating multiple bilobar colorectal liver metastases, partly because of a lack of long-term comparative survival data.

METHODS

Clinicopathologic data were analyzed retrospectively for 53 consecutive patients with 5 or more bilobar liver metastases from colorectal cancer who underwent hepatectomy with or without microwave ablation. Outcome measures were recurrence rate, recurrence pattern, and survival.

RESULTS

Combined resection/ablation was performed more frequently in patients with more liver metastases (P = .03). No significant differences were found for overall, disease-free, or hepatic recurrence-free survival between 16 patients with resection/ablation and 37 patients with resection (P = .43, .54, and .86, respectively). Multivariate analysis selected prehepatectomy carcinoembryonic antigen concentration in serum as an independent prognosticator for survival (P = .02), but not resection/ablation versus resection. In patients with combined resection/ablation, recurrence occurred near the resection or ablation line in only 2 patient (22%), whereas multiple neoplasms (>/=4) was the most common liver recurrence pattern (78%).

CONCLUSIONS

Microwave ablation plus hepatic resection expanded indications for operation to treat multiple bilobar liver metastases, with survival similar to that in less-involved hepatic resection patients.

Percutaneous microwave and radiofrequency ablation for hepatocellular carcinoma: a retrospective comparative study

BACKGROUND

Percutaneous microwave ablation and radiofrequency ablation are two commonly used modalities for the treatment of hepatocellular carcinoma; however, comparisons of them have not been documented adequately.

METHODS

Of 102 patients with biopsy-proved hepatocellular carcinoma, 49 (98 nodules) were treated percutaneously with microwave ablation and 53 (72 nodules) with radiofrequency ablation. The local tumor control, complications related to treatment, and long-term results of the two modalities were compared retrospectively.

RESULTS

The complete ablation rates were 94.9% (93/98) using microwave ablation vs 93.1% (67/72) using radiofrequency ablation (P = 0.75), and no significant differences were found either in the ablation of tumors of 3.0 cm or less (P = 1.00) or in those of more than 3.0 cm (P = 1.00) between the two modalities. The local recurrence rates were 11.8% (11/93) using microwave ablation vs 20.9% (14/67) using radiofrequency ablation (P = 0.12), and there were no significant differences between the two modalities either in tumors of 3.0 cm or less (P = 0.36) or in those of more than 3.0 cm (P = 0.82). The rates of major complications associated with microwave ablation and radiofrequency ablation were 8.2% (4/49) vs 5.7% (3/53; P = 0.71). The disease-free survival rates in the microwave ablation group were 45.9%, 26.9%, 26.9%, and 13.4% at 1, 2, 3, and 4 years, respectively, and those in the radiofrequency ablation group were 37.2%, 20.7%, and 15.5% at 1, 2 and 3 years, respectively (P = 0.53). The 1-, 2-, 3-, and 4-year cumulative survival rates for patients who underwent microwave ablation were 81.6%, 61.2%, 50.5%, and 36.8%, respectively, and for patients who underwent radiofrequency ablation the rates were 71.7%, 47.2%, 37.6%, and 24.2%, respectively (P = 0.12).

CONCLUSIONS

Percutaneous microwave ablation and radiofrequency ablation are both effective methods in treating hepatocellular carcinomas. The local tumor control, complications related to treatment, and long-term survivals were equivalent for the two modalities.

Biloma following repeated transcatheter arterial embolization and complicated by intrahepatic duct stones: A case report

Biloma is an encapsulated bile collection outside the biliary tree due to a bile leak. It is occasionally found following traumatic liver injury or iatrogenic injury to the biliary tract, induced either during an endoscopic or surgical procedure. It is a rare complication of transcatheter arterial embolization (TAE). Although biloma can be shrunk by appropriate aspiration or drainage in majority of cases, we report a case of intrahepatic biloma following repeated TAE for hepatocellular carcinoma (HCC) and complicated by infection and intrahepatic stones. This particular constellation of problems has not been reported before and the intrahepatic stones need to be removed by percutaneous procedure.

Multiple applicator approaches for radiofrequency and microwave ablation

Treatment of tumours greater than 2 cm by radiofrequency (RF) or microwave ablation typically use multiple sequential applications, since most currently available ablation devices are limited to use of a single applicator at a time. A major focus of current ablation research is on methodologies that allow increasing the coagulation zone to more rapidly treat large tumours. The ability to use multiple applicators simultaneously would satisfy this need. It would significantly reduce treatment time and may lead to a reduction in local tumour progression, especially in perivascular locations. Several methods have been suggested that potentially allow simultaneous use of multiple applicators, both with radiofrequency (RF) and microwave (MW) ablation. This review compares the different methods of multiple applicator use, investigating advantages and disadvantages of each modality.

Acute respiratory distress syndrome is a serious complication of microwave coagulation therapy for liver tumors

BACKGROUND

Acute respiratory distress syndrome (ARDS), also known as noncardiogenic pulmonary edema, is a severe complication in cirrhotic patients undergoing microwave coagulation therapy (MCT) for liver tumor. In this study, cirrhotic patients with ARDS after MCT were compared with others without ARDS.

METHODS

Four patients with ARDS after open MCT and 17 other patients without ARDS were compared in terms of preoperative status, intraoperative findings, and postoperative management.

RESULTS

The preoperative Child-Pugh score and intraoperative amount of irradiation showed no significant differences were observed. The postoperative cumulative water balance until the third day was 1,692 +/- 1,315 mL for the ARDS group and 165 +/- 1,524 mL for the non-ARDS group (P = .079), and by the fourth day the respective values were 1,992 +/- 1,585 mL and 66 +/- 1,685 mL, showing a significant difference (P = .049). The postoperative cumulative sodium administration until the third day was 510 +/- 132 mEq for the ARDS group and 362 +/- 122 mEq for the non-ARDS group with a significant difference (P = .044), and by the fourth day the respective values were 642 +/- 141 mEq and 477 +/- 160 mEq (P = .073). Of the 17 patients in the non-ARDS group, 6 were given aldosterone antagonist until the fourth postoperative day, but it was not administered to any of the patients in the ARDS group.

CONCLUSIONS

The water balance and sodium administration have to be closely monitored to prevent cirrhotic patients undergoing MCT from developing ARDS. Aldosterone antagonist appears to be useful for the prevention of ARDS.

Percutaneous ablation therapy for hepatocellular carcinoma: current practice and future perspectives

Worldwide, hepatocellular carcinoma (HCC) is a common, refractory, malignant tumor. Surgical resection is feasible in only a few patients, because of limited hepatic reserve and multifocality of tumors at diagnosis. Percutaneous ablation therapies, including injection of ethanol (PEI) or acetic acid (PAI), radiofrequency ablation (RFA), and microwave coagulation therapy (MCT), have been the major treatments for unresectable HCC in the past decade. PEI is well established for small (<3 cm) HCC, and PAI is equally as effective as PEI, but with fewer treatment sessions. RFA has recently been suggested to have excellent tumor-ablating ability because it produces a fixed and predictable tumor necrosis zone. Although RFA is also effective for medium-sized HCC, the overall complication rate may be higher than previously assumed. MCT is similar to RFA in its clinical application and potential adverse effects. A combination approach using percutaneous ablation therapy and transcatheter arterial embolization was shown to be effective for large HCC. Other approaches, such as injection of hot saline or yttrium-90 microspheres, cryoablation, or interstitial laser photocoagulation, are less often used nowadays. Multimodal, image-guided, tailored therapy, rather than a fixed treatment algorithm, might be more practical for unresectable HCC. In conclusion, although longterm survival is possible in selected patients with HCC, the overall prognosis remains suboptimal, especially in patients with unfavorable tumor characteristics. While newer anti-tumor therapies with improved efficacy are needed, information about a more rational approach to the use of existing therapeutic options may help to enhance treatment strategies for HCC.

Endoscopic perductal electrolytic ablation of the pancreas: experimental studies of morbidity and mortality

BACKGROUND

Palliation of pancreatic cancer remains the only option for the majority of patients. Palliative techniques such as surgical bypass and endoscopic retrograde cholangiopancreatography (ERCP) with stenting are not ideal. The 'ideal' palliative technique would combine the efficacy of surgery with the minimal complications of an endoscopic procedure. Endoscopically delivered perductal electrolytic ablation of pancreatic lesions has the potential to meet these criteria.

METHODS

Fifteen pigs were used. The pancreatic duct was cannulated with an electrolysis catheter. Animals were randomised to either: controls, treatment 2-week survivor or treatment 8-week survivor. An electrolytic dose was administered to the treatment animals. Post-operatively, serum amylase and leucocyte count were assessed. Pancreata were histologically examined to detect evidence of acute pancreatitis.

RESULTS

Electrolysis was well tolerated. There was no difference in post-operative hyperamylasaemia and leucocyte count between the groups. Histological examination showed inflammation at the ablation site at 2 weeks, by 8 weeks this was replaced by scarring.

CONCLUSION

The results of this study suggest that endoscopic perductal electrolytic ablation of the pancreas is feasible and safe. Biochemical and histological findings indicate self-limiting localised inflammation of the pancreas. This technique may have a role in the palliation of pancreatic cancer and warrants further investigation.

Elastographic imaging of thermal lesions in liver in-vivo using diaphragmatic stimuli

Radiofrequency or microwave ablations are interstitial focal ablative therapies that can be used in a percutaneous fashion for treating tumors in the liver, kidney, and prostate. These modalities provide in situ destruction of tumors. We present a method for in-vivo elastographic visualization of the ablated regions in the liver during and after thermal therapy. In-vivo elastographic imaging uses compressions of the liver due to movement of the diaphragm during the respiratory cycle. Elastography of the liver and other abdominal organs has not been attempted previously due to the difficulty in providing controlled compressions. Gating of the data acquisition to the respiratory waveform would provide access to data where the compression increments are similar in both magnitude and direction, thereby enabling reproducible imaging of the thermal lesion or tumor. Comparison of elastograms with gross-pathology of ablated tissue illustrates the correspondence between elastographic image features and pathology. Ultrasound is routinely used to guide the rf ablation procedure, so the same imaging system could be used for elastographic imaging. Since the technique utilizes physiological motion of the diaphragm due to respiration, it may also be employed in the visualization of cancerous tumors in the liver.

Electrolytic liver ablation is not associated with evidence of a systemic inflammatory response syndrome

Background

Local ablation has been proposed for treatment of liver tumours. Cryoshock, a variant of the systemic inflammatory response syndrome (SIRS), is a potentially fatal complication of cryoablation caused by systemic release of necrotic breakdown products from ablated liver. The proinflammatory cytokines tissue necrosis factor (TNF) α and interleukin (IL) 1 are important mediators of this response. This study assessed the risk of SIRS complicating electrolytic liver ablation by measuring circulating levels of inflammatory cytokines, other inflammatory markers and clinical markers of organ function.

Methods

Electrolytic liver ablation was performed in 16 pigs and four pigs served as controls. Platelet count, and serum levels of urea, creatinine, liver enzymes, C-reactive protein (CRP), TNF-α and IL-1β were measured before treatment and for 72 h after the procedure.

Results

There were significant dose-related increases in CRP and alanine aminotransferase levels with liver electrolysis. There was no significant derangement in renal function or platelet count following ablation. A rise in serum TNF-α and IL-1β levels was not associated with liver electrolysis.

Conclusion

There was no evidence of organ failure or significantly raised levels of proinflammatory cytokines as a result of liver electrolysis, suggesting that this is a safe procedure for liver ablation.

The emergent role of focal liver ablation techniques in the treatment of primary and secondary liver tumours

Only 20% of patients with primary or secondary liver tumours are suitable for resection because of extrahepatic disease or the anatomical distribution of their disease. These patients could be treated by ablation of the tumour, thus preserving functioning liver. This study presents a detailed review of established and experimental ablation procedures. The relative merits of each technique will be discussed and clinical data regarding the efficacy of the techniques evaluated. A literature search from 1966 to 2003 was undertaken using Medline, Pubmed and Web of Science databases. Keywords were Hepatocellular carcinoma, liver metastases, percutaneous ethanol injection, cryotherapy, microwave coagulation therapy, radiofrequency ablation, interstitial laser photocoagulation, focused high-intensity ultrasound, hot saline injection, electrolysis and acetic acid injection. Ablative techniques offer a promising therapeutic modality to treat unresectable tumours. Large-scale randomised controlled trials are required before widespread acceptance of these techniques can occur.

Cholangitis and Liver Abscess after Percutaneous Ablation Therapy for Liver Tumors: Incidence and Risk Factors

PURPOSE

To determine the risk factors of cholangitis and liver abscess occurring after percutaneous ablation therapy for liver tumors.

MATERIALS AND METHODS

Between October 1995 and September 2002, 358 patients with 455 liver tumors underwent a total of 683 ablation procedures, such as percutaneous ethanol injection (PEI), percutaneous microwave coagulation (PMC), and radiofrequency (RF) ablation therapy. With a retrospective review of medical records, the rates and outcomes of cholangitis and/or liver abscess occurring after ablation therapy were evaluated. The relationship between cholangitis and/or liver abscess and multiple variables (age, disease, Child-Pugh class, size of nodules, multiplicity of nodules, history of transcatheter arterial embolization, presence of bilioenteric anastomosis, and lack of prophylactic antibiotics administration) were statistically analyzed.

RESULTS

Cholangitis and/or liver abscess occurred in 10 sessions (1.5%) in 10 patients: six sessions after PEI, three sessions after PMC, and one session after RF ablation. Both cholangitis and liver abscess were noted in seven sessions, cholangitis was noted in two, and liver abscess was noted in one. Six patients recovered, but two developed recurrent cholangitis and liver abscess, one developed lung abscess complicated with liver abscess, and one died of septic shock associated with cholangitis. On stepwise regression analysis, bilioenteric anastomosis was the sole significant predictor of cholangitis and/or liver abscess formation (P <.001; odds ratio = 36.4; 95% CI = 9.67-136.9).

CONCLUSION

Bilioenteric anastomosis strongly correlated with the development of cholangitis and/or liver abscess after percutaneous ablation therapy. Close posttreatment attention should be paid to this subgroup of patients.

Thermal ablative therapy for malignant liver tumors: a critical appraisal

The management of primary and secondary malignant liver tumors poses a great challenge to clinicians. Although surgical resection is the gold-standard treatment, most patients have unresectable malignant liver tumors. Over the past decade, various modalities of loco-regional therapy have gained much interest. Among them, thermal ablative therapy, including cryotherapy, microwave coagulation, interstitial laser therapy, and radiofrequency ablation (RFA), have been proven to be safe and effective. Despite the effective tumor eradication achieved within cryotherapy, the underlying freeze/thaw mechanism has resulted in serious complications that include bleeding from liver cracking and the 'cryoshock' phenomenon. Thermal ablation using microwave and laser therapy for malignant liver tumors is curative and is associated with minimal complications. However, this treatment modality is effective only for tumors <3 cm diameter. Radiofrequency ablation seems to be the most promising form of thermal ablative therapy in terms of a lower complication rate and a larger volume of ablation. However, its use is restricted by the difficulty encountered when using imaging studies to monitor the areas of ablation during and after the procedure. Moreover, the techniques of RFA need to be refined in order to achieve the same oncological radicality of malignant liver tumors as achieved by surgical resection. As each of the loco-regional therapies has its own advantages and limitations, a multidisciplinary approach using a combination of therapies will be the future trend for the management of malignant liver tumors.

Hepatic microwave ablation with multiple antennae results in synergistically larger zones of coagulation necrosis

BACKGROUND

Microwave ablation is a promising treatment for unresectable liver tumors. Unlike radiofrequency ablation, microwave ablation may be performed with multiple simultaneously active antennae.

METHODS

Microwave ablation was performed in an in vivo porcine liver model by using a single antenna (n = 11) or three antennae in a triangular array, activated either sequentially (n = 11) or simultaneously (n = 13). Lesions were measured and assigned a qualitative shape score.

RESULTS

Single-antenna microwave lesions had a mean volume of 7.4 +/- 3.9 cm(3), compared with 14.6 +/- 5.2 cm(3) and 43.1 +/- 4.3 cm(3) for sequential and simultaneous multiple-probe ablations, respectively (P <.001; analysis of variance). Simultaneous lesions were rounder than sequential ablations and were more effective near blood vessels. Simultaneous lesions created with probe separation of < or =1.7 cm were round and confluent, whereas clefts were present with distances >1.7 cm (P <.001).

CONCLUSIONS

Microwave ablation has several theoretical advantages over currently available radiofrequency devices. Simultaneous three-probe microwave ablation lesions were three times larger than sequential lesions and nearly six times greater in volume than single-probe lesions. Additionally, simultaneous multiple-probe ablation results in qualitatively better lesions, with more uniform coagulation and better performance near blood vessels. Simultaneous multiple-probe ablation may decrease inadequate treatment of large tumors and decrease recurrence rates after tumor ablation.

Effects of intraaterial chemoembolization combined with percutaneous microwave coagulation on hepatocellular carcinoma: a clinical and experimental study

AIM: To evaluate the role of microwave coagulation for liver cancer after occlusion of hepatic artery in animal experiment and clinical study.

METHODS: Total 24 suitable hepatic lobes of ten dogs were separated into two groups. Microwave coagulation alone (control group) or after hepatic artery occlusion (experiment group) was performed respectively. The power of irradiation was 50 W and the duration was 300 and 400 seconds. Clinically, 25 patients with hepatocellular carcinoma (30 nodules) were treated with PMCT after TACE. The TACE was performed 1-3 times and PMCT 1-2 times totally in every patients.

RESULTS: In animal experiment, the coagulated area was elliptic in control group and was elliptic or round in experimental group. The volume of coagulated tissue in experimental group was 3.8 times bigger than that in control. Clinically, all the lesions in contrast-enhanced CT showed slight enhancement or no enhancement after treatment. Intratumoral blood flow decreased significantly in 6 patients and disappeared in 20 patients. In 19 patients with elevated a-fetoprotein, the level decreased in all patients and was normalized in 14. There were no significant side- effects.

CONCLUSION: PMCT after TACE can significantly enlarge the necrosis volume of microwave coagulation, and promote the efficacy of treatment for hepatocellular carcinoma.

Interstitial ablative techniques for hepatic tumours

BACKGROUND

Most patients with liver tumours are not suitable for surgery but interstitial ablative techniques may control disease progression and improve survival rates.

METHODS

A review was undertaken using Medline of all reported studies of cryoablation, radiofrequency ablation, microwave ablation, interstitial laser photocoagulation, high-intensity focused ultrasound and ethanol ablation of primary liver tumours and hepatic metastases.

RESULTS

Although there are no randomized clinical trials, cryoablation, thermal ablation and ethanol ablation have all been shown to be associated with improved palliation in patients with primary and secondary liver cancer. The techniques can be undertaken safely with minimal morbidity and mortality.

CONCLUSION

Although surgical resection remains the first line of treatment for selected patients with primary and secondary liver malignancies, interstitial ablative techniques are promising therapies for patients not suitable for hepatic resection or as an adjunct to liver surgery.

The histological features of microwave coagulation therapy: an assessment of a new applicator design

Microwave ablation of tumours within the liver may become an adjunct or alternative to resection in patients with primary or secondary cancers. This technique combines the benefits of a large, localized coagulative effect with a single insertion of the applicator, in a significantly shorter time than comparable treatments. A new range of microwave applicators were developed and tested in animal models and both ex-vivo and in-vivo specimens of human liver at resection. At laparotomy, the applicator tip was inserted into normal liver parenchyma and tumours, with each specimen subjected to irradiation for 180 s or more and at varying power outputs. On sectioning an area of spherical blanching was observed around the applicator cavity. Microscopically a zone of coagulative necrosis was seen adjacent to the site of probe insertion. Damage to blood vessels and bile ducts occurred distal to the probe cavity suggesting the passage of heated fluid, a finding that was diminished by temporary occlusion of the hepatic vasculature (a Pringle manoeuvre). Ultra-structural damage was confirmed within the burn zone and selected liver enzymes were shown to be functioning beyond this region. We suggest this indicates the surrounding liver parenchyma is functioning normally and therefore the volume of microwave-induced damage is controllable. We are confident that the new applicator design will allow the effective treatment of larger tumours in a safe and controlled manner with a single application of energy.

Minimally invasive image-guided therapies for hepatocellular carcinoma

Minimally invasive therapies are gaining increasing attention as an alternative to standard surgical therapies in the treatment of primary hepatocellular carcinoma. These include therapies administered transcatheterally (arterial embolization, intraarterial chemoinfusion, and combination chemoembolization) and percutaneously (chemical ablation with ethanol or acetic acid, and thermal ablation with radiofrequency, microwave, or laser energies). Benefits over surgical resection include the anticipated reduction in morbidity and mortality, low cost, suitability for real time image guidance, the ability to perform ablative procedures on outpatients, and the potential application in a wider spectrum of patients, including nonsurgical candidates. This review examines reported clinical success, potential complications, current limitations, and future directions of development of chemoembolization, ethanol and acetic acid instillation, and radiofrequency, microwave, and laser thermal ablation.

Malignant liver tumors treated with MR imaging-guided laser-induced thermotherapy: experience with complications in 899 patients (2,520 lesions)

PURPOSE

To evaluate the complications from laser-induced thermotherapy (LITT) of malignant liver tumors and demonstrate that LITT is safe as an outpatient procedure.

MATERIALS AND METHODS

During 8 years, 899 patients with malignant liver tumors were treated with magnetic resonance (MR) imaging-guided LITT. A total of 2,132 LITT procedures were performed to treat 2,520 lesions. To account for the technical evolution of LITT during this time and the change from performing the procedure on an inpatient basis to performing it on an outpatient basis, patients were assigned to four groups. Overall complication rates and major and minor complications in the inpatient versus outpatient groups were evaluated. Multidimensional contingency table analysis with the chi(2) test was performed.

RESULTS

On the basis of a total of 2,132 LITT procedures performed, complications were divided into major and minor categories and detected at clinical or imaging studies. Major complications included three deaths (0.1%) within 30 days after LITT, pleural effusion requiring thoracentesis in 16 (0.8%) cases, hepatic abscess requiring drainage in 15 (0.7%) cases, bile duct injury in four (0.2%) cases, segmental infarction in three (0.1%) cases, and hemorrhage requiring transfusion in one (0.05%) case. Minor complications included postprocedural fever in 710 (33.3%), pleural effusion not requiring thoracentesis in 155 (7.3%), subcapsular hematoma in 69 (3.2%), subcutaneous hematoma in 24 (1.1%), pneumothorax in seven (0.3%), and hemorrhage in two (0.1%) cases. Outpatient management did not significantly affect pleural effusion (P =.96) or subcapsular hematoma (P =.33) rate.

CONCLUSION

MR imaging-guided LITT with local anesthesia is safe and yields an acceptably low rate of major complications.

Thermal ablation therapy for hepatocellular carcinoma

Thermal ablation strategies, including the use of radiofrequency, microwaves, lasers, and high-intensity focused ultrasound, are gaining increasing attention as an alternative to standard surgical therapies in the treatment of primary hepatocellular carcinoma. Benefits over surgical resection include the anticipated reduction in morbidity and mortality, low cost, suitability for real-time imaging guidance, ability to perform ablative procedures on an outpatient basis, and the potential application in a wider spectrum of patients-including those who are not surgical candidates. In this review, the authors examine the reported clinical success of each of these four therapies, potential complications, current limitations, and future directions of development.

Locoregional therapies for hepatocellular carcinoma: a critical review from the surgeon's perspective

OBJECTIVE

This article reviews the current results of various locoregional therapies for hepatocellular carcinoma (HCC), with special reference to the implications for surgeons.

SUMMARY BACKGROUND DATA

Resection or transplantation is the treatment of choice for HCC, but most patients are not suitable candidates. The past decade has witnessed the development of a variety of locoregional therapies for HCC. Surgeons are faced with the challenge of adopting these therapies in the management of patients with resectable or unresectable HCC.

METHODS

A review of relevant English-language articles was undertaken based on a Medline search from January 1990 to August 2001.

RESULTS

Retrospective studies suggested that transarterial chemoembolization is an effective treatment for inoperable HCC, but its perceived benefit for survival has not been substantiated in randomized trials, presumably because its antitumor effect is offset by its adverse effect on liver function. Nonetheless, it remains a widely used palliative treatment for HCC not amenable to resection or ablative therapies, and it also plays an important role as a treatment of postresection recurrence and as a pretransplant therapy for transplantable HCC. Better patient selection, selective segmental chemoembolization, and treatment repetition tailored to tumor response and patient tolerance may improve its benefit-risk ratio. Transarterial radiotherapy is a less available alternative that produces results similar to those of chemoembolization. Percutaneous ethanol injection has gained wide acceptance as a safe and effective treatment for HCCs 3 cm or smaller. Uncertainty in tumor necrosis limits its potential as a curative treatment, but its repeatability allows treatment of recurrence after ablation or resection of HCC that is crucial to prolongation of survival. Cryotherapy affords a better chance of cure because of predictable necrosis even for HCCs larger than 3 cm, but its use is limited by a high complication rate. There has been recent enthusiasm for heat ablation by microwave, radiofrequency, or laser, which provides predictable necrosis with a low complication rate. Preliminary data indicated that radiofrequency ablation is superior to ethanol injection in the radicality of tumor ablation. The advent of more versatile radiofrequency probes has allowed ablation of HCCs larger than 5 cm. Recent studies have suggested that combined transarterial embolization and heat ablation is a promising strategy for large HCCs. Thus far, no randomized trials comparing various thermoablative therapies have been reported. It is also uncertain whether a percutaneous route, laparoscopy, or open surgery affords the best approach for these therapies. Thermoablative therapies have been combined with resection or used to treat postresection recurrence, and they have also been used as a pretransplant therapy. However, the value of such strategies requires further evaluation.

CONCLUSIONS

Advances in locoregional therapies have led to a major breakthrough in the management of unresectable HCC, but the exact role of the various modalities needs to be defined by randomized studies. Novel thermoablative techniques provide the surgeon with an exciting opportunity to participate actively in the management of unresectable HCC. Locoregional therapies are also useful adjuncts in the management of patients with resectable or transplantable disease. Hence, surgeons must be equipped with the latest knowledge and techniques of ablative therapy to provide the most appropriate treatment for the wide spectrum of patients with HCC.

Electrolysis and other local ablative treatments for non-resectable colorectal liver metastases

The present paper is a review of the current ablative treatment options for the treatment of colorectal liver metastases. Cryotherapy, microwave coagulation therapy, radiofrequency ablation and laser-induced thermotherapy are discussed. Electrolysis, a novel non-thermal ablative treatment, is described. Potential benefits of electrolysis include the apparent ability to safely and effectively treat lesions abutting major hepatic structures and the lack of a systemic inflammatory reaction following electrolytic ablation. Further studies in animals and humans are needed to confirm this potential and to further refine the methods of electrolytic treatment of colorectal liver metastases.

Control of interstitial thermal coagulation: comparative evaluation of microwave and ultrasound applicators

This study presents a comparative evaluation of the control of heating and thermal coagulation with microwave (MW) and ultrasound (US) interstitial applicators. Helical coil MW antennas (17 mm and 25 mm length radiating antennae) were tested using an external implant catheter (2.2 mm o.d.) with water-cooling. US applicators with tubular transducers (2.2 and 2.5 mm o.d., 10 mm length, single-element and 3-element) were utilized with a direct-coupled configuration and internal water-cooling. Measurements of E-field distributions (for MW) and acoustic beam distributions (for US) were used to characterize the applicator energy output. Thermal performance was evaluated through multiple heating trials in vitro (bovine liver) and in vivo (porcine thigh muscle and liver) at varied levels of applied power (20-40 W for microwave, 15-35 W for ultrasound) and heating times (0.5-5 min). Axial temperature distributions in the tissue were recorded during heating, and dimensions of the resulting lesions of thermal coagulation were measured. Both MW and US applicators produced large volumes of tissue coagulation ranging from 8 to 20 cm3 with singular heating times of 5 min. Radial depth of lesions for both MW and US applicators increased with heating duration and power levels, though US produced notably larger lesion diameters (30-42 mm for US vs 18-26 mm for MW, 5 min heating). Characteristic differences between the applicators were observed in axial energy distribution, tissue temperatures, and thermal lesion shapes. MW lesions increased significantly in axial dimensions (beyond the active applicator length) as applied power level and/or heating duration was increased, and lesion shapes were generally not uniform. US provided greater control and uniformity of heating, with energy deposition and axial extent of thermal lesions corresponding to the length of the active transducer(s). The improved ability to control the extent of thermal coagulation demonstrated by the US applicators provides greater potential to target a specific region of tissue.

Axial control of thermal coagulation using a multi-element interstitial ultrasound applicator with internal cooling

A multi-element, direct-coupled ultrasound (US) applicator with internal water cooling was investigated for axial control of interstitial thermal coagulation. A prototype implantable applicator was constructed with a linear array of three tubular PZT ultrasound transducers (each 2.5 mm OD, 10 mm length, 360 degrees emittance). Acoustic beam distributions from each element were measured and found to be collimated within the transducer length. The internally cooled applicator could sustain high levels of applied power to each transducer (0 to 40 W) and maintain acceptable applicator surface temperatures (<100 degrees C). Thermal performance of the applicator was investigated through heating trials in vivo (porcine thigh muscle and liver) and in vitro (bovine liver). The radial depth of thermal lesions produced was dependent on the applied power and sonication time and was controlled independently with power levels to each transducer element. With 18 W per element (applied electrical power) for 3 min, cylindrical thermal lesions were produced with a diameter of ~3 cm and a length ranging from 1.2 cm (with one element) to 3.5 cm (three elements). Higher powers (24 to 30 W) for 3 to 5 min provided increased depths of coagulation (~4 cm diameter lesions). Analysis of axial lesion shapes demonstrated that individual variation of power to each transducer element provided control of axial heating and depth of coagulation (for custom lesion shapes); lesion lengths corresponded to the number of active transducers. This ability to control the heating distribution dynamically along the length of the applicator has potential for improved target localization of thermal coagulation and necrosis in high temperature thermal therapy.

DIGEST: professor seiki matsuno and Dr michiaki unno, chief editors of surgery today (The japanese journal of surgery), have selected from the october-december 1998 issues of the journal for this quarter's digest. A digest of BJS for the same period written by Mr colin johnson, european editor, appears in the japanese journal

Professor Seiki Matsuno and Dr Michiaki Unno, Chief Editors of Surgery Today (The Japanese Journal of Surgery), have selected from the October–December 1998 issues of the journal for this quarter's digest. A digest of BJS for the same period written by Mr Colin Johnson, European Editor, appears in the Japanese journal.