Hepatic metastases: interstitial laser photocoagulation with real-time US monitoring and dynamic CT evaluation of treatment

Hepatocellular Carcinoma: Long-term Results of Combined Treatment with Laser Thermal Ablation and Transcatheter Arterial Chemoembolization

PURPOSE

To determine the potential long-term effectiveness of laser thermal ablation (LTA) followed by transcatheter arterial chemoembolization (TACE) in the percutaneous ablation of large hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Thirty large HCCs 3.5-9.6 cm in diameter (mean diameter, 5.2 cm) and 15 small HCCs 0.8-3.0 cm (mean diameter, 1.9 cm) were treated with ultrasonographically guided LTA with TACE and with LTA alone, respectively, in 30 patients: 19 with a solitary large HCC, and 11 with one to three additional synchronous small HCCS: A 1.064-microm neodymium yttrium-aluminium-garnet (Nd-YAG) laser at a power of 5.0 W was coupled with one to four quartz optic fibers that were advanced through 21-gauge needles. Segmental TACE was performed 30-90 days after LTA. All lesions were evaluated for change in size at computed tomography (CT), alpha-fetoprotein (AFP) levels, recurrence rates, and cumulative survival rates.

RESULTS

No major complications occurred in 127 LTA sessions. CT showed complete tumor necrosis in 27 (90%) of 30 large HCCS: Twenty-eight patients were followed up for 6-41 months (mean, 17.1 months). In 25 patients, all lesions appeared stable or smaller at CT. AFP levels decreased to the normal range in all patients with high pretreatment values. The 1-, 2-, and 3-year local recurrence rate was 7% in large HCCS: Complete tumor necrosis was achieved in all 15 (100%) small HCCs; none of them recurred locally. The 1-, 2-, and 3-year cumulative survival rates were 92%, 68%, and 40%, respectively.

CONCLUSION

LTA followed by TACE is an effective palliative therapy in treating large HCCS:

Radiofrequency liver ablation: experimental comparative study of water-cooled versus expandable systems

OBJECTIVE

We evaluate the uniformity and reproducibility of thermal lesion ablation and quantify the volume of tissue destruction and hemorrhage induced with two different commercially available radiofrequency ablation devices.

MATERIALS AND METHODS

A four-array anchor expandable needle electrode and a triple-cluster cooled-tip needle electrode were used to induce lesions in three explanted calf livers and in vivo in eight swine livers. The sizes of the radiofrequency-induced lesions were macroscopically evaluated by measuring two perpendicular dimensions immediately after the experiment. Bleeding was evaluated by weighing gauze swabs used to dry the hemorrhage caused by electrode insertions.

RESULTS

In explanted liver, the mean diameter of the radiofrequency-induced lesion was 5.3 +/- 0.7 cm for the cooled-tip needle and 3.7 +/- 0.4 cm for the expandable needle (p = 0.042), which correspond to approximate volumes of 65.35 +/- 26.22 cm(3) and 26.67 +/- 9.59 cm(3), respectively (p < 0.002). In vivo, the mean diameter was 3.7 +/- 0.4 cm for the cooled-tip needle and 3 +/- 0.4 cm for the expandable needle (p < 0.0001), which correspond to approximate volumes of 24.18 +/- 7.56 cm(3) and 11.16 +/- 3.65 cm(3), respectively (p < 0.0001). Blood loss attained a median value of 3.5 g for the cooled-tip needle and 2.6 g for the expandable needle; this difference was not statistically significant (p = 0.06).

CONCLUSION

The cooled-tip needle induced significantly larger lesions than the expandable needle, but the lesions produced by the expandable needle are more reproducible, uniform, and spheric. The larger size of the lesions produced by the cooled-tip needle may be attributed to the higher maximum power used by the generator and the higher energy deposition, which is due to the cooling of the needle electrode.

Thyroid tissue: US-guided percutaneous interstitial laser ablation-a feasibility study

PURPOSE

To evaluate percutaneous interstitial laser photocoagulation (ILP) as a palliative treatment of recurrent thyroid carcinoma untreatable with surgery or radioiodine administration.

MATERIALS AND METHODS

By using 18 resected thyroid glands, the volume and histologic pattern of ILP-induced thyroid damage were assessed. In vivo treatment feasibility was evaluated by using a low-energy laser in two volunteers before thyroidectomy for huge autonomously functioning nodules. With ultrasonographic (US) monitoring, a 21-gauge spinal needle was inserted into the thyroid nodules. A 300-microm quartz fiberoptic guide was inserted through the needle lumen, and the fiber tip was placed in direct contact with the tissue. Laser irradiation was performed with a 1.064-nm Nd:YAG laser in surgically resected glands, which were treated with 2, 3, 5, or 7 W.

RESULTS

Tissue ablation was well-defined histologically, and its area was related to laser irradiation parameters (range, 0-26 mm). No correlation was found between US images and the actual extent of laser-induced lesions. Large colloid or fluid collections did not permit regular heat diffusion within the tissue. In vivo low-energy ILP was performed without technical difficulties or complications.

CONCLUSION

ILP induces well-defined tissue ablation correlated with energy parameters in thyroid glands devoid of cystic areas. ILP could be a therapeutic tool for highly selected problems in thyroid tumor treatment.

Hepatocellular carcinoma treated with percutaneous radio-frequency ablation: usefulness of power Doppler US with a microbubble contrast agent in evaluating therapeutic response-preliminary results

PURPOSE

To evaluate the usefulness of power Doppler ultrasonography (US) with a microbubble contrast agent in assessing the therapeutic response of hepatocellular carcinomas (HCCs) treated with percutaneous radio-frequency (RF) ablation.

MATERIALS AND METHODS

Forty patients with 45 nodular HCC lesions 1.0-3.8 cm in diameter underwent power Doppler US before and after intravenous injection of a microbubble contrast agent. The same procedures were repeated after US-guided percutaneous RF ablation. The results of these studies were compared with those of three-phase helical computed tomography (CT) performed immediately after RF ablation.

RESULTS

Before RF ablation, nonenhanced power Doppler US demonstrated flow signals within tumor in 33 of 45 HCCs. After contrast agent administration, flow signals increased or newly appeared in all cases. After RF ablation, none of the ablated tumors showed intratumoral flow signals at nonenhanced power Doppler US, whereas six showed marginal intratumoral flow signals at contrast agent-enhanced power Doppler US. These six tumors were found to have small enhancing foci, suggestive of viable tumor, in corresponding areas at immediate follow-up CT. Additional RF ablation or transcatheter arterial chemoembolization was performed in these tumors.

CONCLUSION

The results of power Doppler US with a microbubble contrast agent in HCCs treated with RF ablation correlated well with those of contrast-enhanced CT. Preliminary data suggest that contrast-enhanced power Doppler US can be a promising noninvasive technique for assessing therapeutic response.

Radiofrequency thermal ablation of hepatocellular carcinomas

Although surgical resection remains the best option as potentially curative therapy for hepatocellular carcinoma, radiofrequency thermal ablation has begun to receive much attention as an effective minimally invasive technique for the local control of unresectable malignant hepatic tumors. Most recent radiofrequency devices equipped with a powerful generator and larger needle electrode permit larger thermal lesions, up to 5 cm in diameter, with a single ablation. In this article, the author reviews the technical developments and early clinical results obtained with radiofrequency ablation techniques.

Microwave coagulation therapy for multiple hepatic metastases from colorectal carcinoma

BACKGROUND

Compared with other treatments, microwave coagulation is a relatively less invasive treatment for various kinds of solid tumors. Although its effectiveness in primary hepatocellular carcinoma has been shown, its effectiveness in the treatment of hepatic metastases from colorectal carcinoma has been unclear. The aim of this study was to evaluate its effectiveness in the treatment of multiple hepatic metastases from colorectal carcinoma by comparing this technique with that of hepatic resection.

METHODS

Thirty patients with multiple metastatic colorectal tumors in the liver who were potentially amenable to hepatic resection were randomly assigned to treatment with microwave coagulation (14 patients) or hepatectomy (16 patients). Tumors in the microwave group were coagulated after laparotomy at an output of 60-100 W for 2-20 minutes under the guide of ultrasonography, whereas tumors in the hepatectomy group were treated with lobectomy, segmentectomy, subsegmentectomy, and/or wedge resection.

RESULTS

One-, 2-, and 3-year survival rates and mean survival times were 71%, 57%, 14%, and 27 months, respectively, in the microwave group, whereas they were 69%, 56%, 23%, and 25 months, respectively, in the hepatectomy group. The difference between these two groups was statistically not significant (P = 0.83). On the other hand, the amount of intraoperative blood loss in the microwave group (360 +/- 230 mL) was smaller than that in the hepatectomy group (910 +/- 490 mL, P < 0.05). Blood transfusion was necessary for 6 patients in the hepatectomy group, but it was not necessary in the microwave group.

CONCLUSIONS

Microwave coagulation therapy is suggested to be equally effective as hepatic resection in the treatment of multiple (two to nine) hepatic metastases from colorectal carcinoma, whereas its surgical invasiveness is less than that of hepatic resection.

Histopathological features of liver damage induced by laser ablation in rabbits

BACKGROUND AND OBJECTIVE

Possible mechanisms that promote or interfere with the effects of laser ablation of the liver have not been clarified. The aim of this study was to define the chronological alterations in the normal rabbit liver at early stages after laser ablation.

STUDY DESIGN/MATERIALS AND METHODS

Rabbit livers were ablated with a laser via an optical fiber and then analyzed histopathologically by immunostaining for heat shock protein 70 (HSP70) and by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) method.

RESULTS

The lesions increased in size progressively over the 24 h that followed ablation and the area of the lesion coincided with the area that had been heated above 43 degrees C. TUNEL-positive hepatocytes were surrounded, at some distance, by HSP70-positive hepatocytes were surrounded, at some distance, by HSP70-positive hepatocytes at 6 h, and such cells were in contact with each other at 24 h.

CONCLUSIONS

Injury to hepatocytes induced by laser ablation increases for 24 h and dying cells express nuclear HSP70, with subsequent fragmentation of DNA.

Comparison of 810 nm and 1064 nm wavelengths for interstitial laser photocoagulation in rabbit brain

BACKGROUND AND OBJECTIVE

This laboratory animal study is a comparison of Nd:YAG 1064 nm and diode 810 nm laser wavelengths in brain interstitial laser photocoagulation (ILP). Specific goals were to identify potential complications and physical characteristics of the thermal damage at both wavelengths prior to undertaking a clinical trial in humans.

STUDY DESIGN/MATERIALS AND METHODS

A total of 41 ILP illuminations were performed in vivo in the brains of 33 anesthetized rabbits using plane-cut fiber tips implanted directly or through catheters, and diffusing fiber tips. Delivered powers ranged from 1.1 to 4.2 W. Exposures ranged from 300 to 900 s. Survival ranged from 0 to 48 h. Experiments were performed in animals with and without VX-2 brain tumors.

RESULTS

Thermal damage from 1.1 W at 810 nm was similar to that from 1.6 W at 1064 nm, but more pronounced. With plane-cut fiber tips, there was a greater propensity for severe physical effects (smoke, charring, bubbling, surface damage) at 810 nm than at 1064 nm, yet hemorrhage, thrombosis and vapor dissemination were observed at both wavelengths, in both normal brain and tumor.

CONCLUSIONS

For ILP in brain, 1064 nm may be better suited than 810 nm, although both are questionable with plane-cut-fiber tips. Compactness and portability may be the only valid reasons for using laser diodes operating around 810 nm. At 1064 nm, the power delivered from plane-cut fiber tips should be less than 1.5 W, necessitating long exposures, or else an open catheter should be used. Fiber tips with distributed emission may be preferred, provided structural integrity can be maintained.

Nd: YAG interstitial laser thermotherapy in the treatment of breast cancer

BACKGROUND AND OBJECTIVE

"Minimal treatment strategy" is desirable in certain breast cancer patients. The main objective of the present study is to examine the use of interstitial laser thermotherapy (laserthermia) for this purpose.

STUDY DESIGN/MATERIALS AND METHODS

Thirty-five patients with primary breast cancer were treated with laserthermia using the Nd:YAG (1,064 nm) pulse-wave laser. In 28 patients, laserthermia was performed before radical resection, and in seven patients it was the only invasive treatment.

RESULTS

One gaseous rupture of tumor occurred at 3 Watts. The diameter of single focus of laser-induced damage after 1-2 Watts was less than 1 cm, and after 2.5-6 Watts it reached 1.5-2.5 cm. Of seven patients treated without surgery, local tumor control was achieved in five, and in three stage I-III patients disease-free survival followed for 19-60 months. After laserthermia plus surgery, 3-year disease-free survival was 27% in premenopausal and 92% in menopausal patients.

CONCLUSIONS

It seems that laser destruction of relatively small primary breast cancer is possible. Provisionally, laserthermia should not be used in premenopausal patients.

Interstitial laser photocoagulation under ultrasound guidance of liver tumors: results in 104 treated patients

OBJECTIVE

To evaluate the efficacy and complications of interstitial laser photocoagulation (ILP) under ultrasound (US) guidance as a technique for focal ablation of liver tumors in patients with normal and impaired hepatic function.

PATIENTS AND METHODS

A total of 104 patients, 77 with 85 nodules of hepatocellular carcinoma on cirrhosis (29 in Child-Pugh A class, 43 in B e 5 in C class) and 27 patients with hepatic metastases (25 from colon, two from lung carcinoma) underwent ILP under US guidance. Depending on tumor size up to four needles were inserted in the tumor and multiple laser illuminations were performed in one or multiple sessions. Necrosis of the nodules was evaluated with triphasic contrast-enhanced CT.

RESULTS

Ninety-four patients underwent a single ILP session and nine patients two sessions. CT showed complete necrosis in 70 out of 85 HCC nodules in 65 treated patients and in 24 out of 31 patients with metastases. Three Child C class patients dropped out the control of efficacy by CT because of severe liver failure associated in one case with transient paralytic ileum. One of these patients died 2 months after treatment. Two patients with metastasis dropped the completion of the treatment because of complication occurred after the ILP session (one paralytic ileum, one gastric haemorrage).

CONCLUSIONS

ILP under US guidance is effective in inducing complete necrosis in small and large liver tumors. Nevertheless, ILP can cause severe derangement of liver function in patients with advanced cirrhosis.

Survival after percutaneous, image-guided, thermal ablation of hepatic metastases from colorectal cancer

PURPOSE

One-year, two-year, three-year, and four-year survival rates and median survival time for patients with inoperable liver metastases from colorectal cancer is 32, 10, and 3 percent and 7.4 to 11 months, respectively. Systemic chemotherapy produces a modest improvement to 48, 21, and 3 percent and 12 months, respectively. Regional chemotherapy produces a further improvement to 64, 25, and 5 percent and 15 to 17 months, respectively. For those with operable disease, hepatic resection survival rates are 90, 62, 48, and 40 percent, respectively, and survival time is 33 months. Thermal ablation is effective in producing necrosis in liver metastases. We report the impact on survival in 69 patients treated from 1993 to 1997, with follow-up to 1998.

METHODS

Sixty-nine patients, 50 male, mean age 60 (range, 33-87) years were treated. Liver resection was not feasible because of disease extent in the liver, extrahepatic disease or concurrent medical conditions. The average number of liver metastases was 2.9 (range, 1-16), the mean maximal diameter was 3.9 (range, 1-8) cm, and the mean initial total liver tumor volume was 47 (range, 1-371) ml. Eighteen (26 percent) had undergone previous hepatic resection. Sixty-two of 67 (93 percent) received chemotherapy at some stage. Twenty (29 percent) had extrahepatic disease.

RESULTS

One-year, two-year, three-year, and four-year survival rates and median survival time from liver metastasis diagnosis was 90, 60, 34, and 22 percent and 27 months, respectively. Forty of 69 (58 percent) developed new liver metastases, and 23 of 69 (33 percent) developed new extrahepatic disease. Of a subgroup of 24 patients with less than four metastases, <5 cm diameter, treated after January 1995, the median survival time was 33 months from first thermal ablation vs. 15 months for the remainder (P = 0.0004). Major morbidity occurred in 3.2 percent, minor morbidity occurred in 12 percent, and there was one periprocedural death.

CONCLUSIONS

Thermal ablation therapy improves survival in patients with inoperable but limited liver metastases. This is an improvement on the natural history of the disease and published chemotherapy results. Recent and ongoing technical refinements, not reflected in these results, are expected to further improve survival.

Local recurrence after laparoscopic radiofrequency thermal ablation of hepatic tumors

BACKGROUND

Since we first described laparoscopic radiofrequency ablation (LRFA) of liver tumors, several reports have documented technical and safety aspects of this procedure. Little is known, however, about the long-term follow-up of such patients.

METHODS

From January 1996 to February 1999, we performed LRFA on 250 liver tumors in 66 patients. Triphasic spiral computed tomographic scanning was obtained preoperatively and at 1 week, and every 3 months postoperatively. Lesion diameter was measured in the x- and y-axes and the volume estimated; 181 lesions in 43 patients for whom computed tomographic scans available were included in the study. The tumor types were as follows: 64 metastatic adenocarcinomas, 79 neuroendocrine metastases, 27 other metastases, and 11 primary liver tumors.

RESULTS

One week postoperatively, the ablated zone was larger than the original tumor in 178 of 181 lesions, which suggests ablation of the tumor and a margin of normal liver tissue. A progressive decline in lesion size was seen in 156 (88%) of 178 lesions, followed for at least 3 months (mean, 13.9 months; range, 4.9-37.8 months), which suggests resorption of the ablated tissue. Fourteen definite local treatment failures were apparent by increase in size and change in computed tomographic scan appearance, and eight lesions were scored as failures because of multifocal recurrence that encroached on ablated foci (22 total recurrences). Predictors of failure include lack of increased lesion size at 1 week (2 of 3 such lesions failed), adenocarcinoma or sarcoma (18 of 22 failures; P < .05), larger tumors (failures, M = 18 cm3 vs. successes, M = 7 cm3; P < .005) and vascular invasion on laparoscopic ultrasonography. By size criteria, 17 of 22 failures were apparent by 6 months. Energy delivered per gram of tissue was not significantly different (P = .45).

CONCLUSIONS

LRFA has a 12% local failure rate, with larger adenocarcinomas and sarcomas at greatest risk. Failures occur early in follow-up, with most occurring by 6 months. LRFA seems to be a safe and effective treatment technique for patients with primary and metastatic liver malignancies.

Monitoring response to treatment in liver tumours

New imaging techniques offer better ways of measuring response to treatment and remain central to the formal assessment of response in clinical trials and routine clinical practice. Increasing tumour size is consistently associated with progressive disease. However, there is evidence that the designation 'partial response', as determined by conventional imaging techniques, may not always accurately reflect the degree of treatment-induced tumour necrosis. Thus, responses classified as partial on imaging grounds have, in some cases, been shown to be complete pathological responses after surgical resection, implying that residual tumour and necrotic/fibrotic tumour remnants cannot always be accurately distinguished by imaging. In this situation, serological tumour markers such as alphafetoprotein may be useful in measuring the true degree of response. While radiological imaging is likely to remain the main method of assessing response in phase II trials of drugs for the treatment of liver cancer, it may in some instances be useful to apply additional parameters such as alphafetoprotein level.

Simplified treatment planning for interstitial laser thermotherapy by disregarding light transport: a numerical study

BACKGROUND AND OBJECTIVE

The objective was to investigate the effect of light transport on the temperature distribution and the coagulated volume under conditions relevant to interstitial laser thermotherapy (ILT) of tumors in the human liver.

STUDY DESIGN/MATERIALS AND METHODS

Temperature distributions and coagulated volumes produced with a diffusing laser fiber or a conductive heat source, at equal output power, were numerically calculated for tissue with different optical penetration depths. Four irradiation times (5, 10, 20, and 30 min) were studied. A three-dimensional finite-element model was used to calculate the temperature distribution during heating with four conductive heat sources (no light emission). Results were compared with measured temperature distributions during laser irradiation in a gel phantom with known optical properties.

RESULTS

Numerical calculations showed that the influence of light transport on the coagulated volume was negligible in tissue with optical penetration depths below 3-4 mm at all studied irradiation times. The phantom experiment indicated good agreement with the calculated temperature distribution, both with a single diffusing laser fiber and with four fibers.

CONCLUSION

Light transport influences coagulated volumes only slightly under conditions presented in this work, which is relevant to ILT of tumors in the human liver.

Current treatment for colorectal cancer metastatic to the liver

Surgery is currently the only available treatment option which offers the potential for cure for patients with liver metastases from colorectal cancer. Of those who undergo a potentially curative operation for their primary tumour but subsequently recur, almost 80% will develop evidence of metastatic disease within the liver. Greater experience and improvements in technique in liver surgery, with an increasingly aggressive surgical approach to metastatic colorectal cancer to the liver, has resulted in prolonged disease-free survival with 5-year rates varying from 21% to 48%. In order to increase these numbers further and to treat patients not eligible for surgical therapy, new treatment modalities and strategies have been developed. This review presents an update of the current treatment for colorectal disease metastatic to the liver.

Near-infrared optical properties of ex vivo human uterus determined by the Monte Carlo inversion technique

The optical properties, absorption (mua) and reduced scattering coefficient (mu's), of ex vivo human myometrium and leiomyoma (fibroid) have been determined by the Monte Carlo inversion technique over the wavelength range 600-1000 nm. This region is currently of interest for new, minimal-access, surgical laser procedures such as photodynamic therapy (PDT) for abnormalities of the uterus, and interstitial laser photocoagulation (ILP) for the thermal ablation of fibroids. In the region 630-675 nm (corresponding to PDT), the optical coefficients of myometrium are mua = 0.041+/-0.012 mm(-1) and mu's = 1.37+/-0.19 mm(-1). For the wavelength range 800-1000 nm (associated with infrared lasers for ILP), the optical coefficients of fibroid were found to be mua = 0.020+/-0.003 mm(-1) and mu's = 0.56+/-0.03 mm(-1). Overall, the optical properties of fibroid were found to be lower than myometrium, and this was attributed to the differences in both anatomy and vascularity. The results show that PDT for ablation of the uterine endometrium is most unlikely to affect any tissues beyond the myometrium, and that the region around 800 nm is the most effective for ablation of fibroids using ILP as the penetration depth of light is greatest at this wavelength.

Effective treatment of liver metastases with photodynamic therapy, using the second-generation photosensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC), in a rat model

The only curative treatment for patients with liver metastases to date is surgery, but few patients are suitable candidates for hepatic resection. The majority of patients will have to rely on other treatment modalities for palliation. Photodynamic therapy (PDT) could be a selective, minimally invasive treatment for patients with liver metastases. We studied PDT in an implanted colon carcinoma in the liver of Wag/Rij rats, using the photosensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC). mTHPC tissue kinetics were studied using ex vivo extractions and in vivo fluorescence measurements. Both methods showed that mTHPC kinetics were different for liver and tumour tissue. After initial high levels at 4 h after administration (0.1 and 0.3 mg kg(-1)) mTHPC in liver tissue decreased rapidly in time. In tumour tissue no decrease in photosensitizer levels occurred, with mTHPC remaining high up to 48 h after administration. Both concentration data and fluorescence data showed an increase in tumour to liver ratios of up to 6.3 and 5.0 respectively. Illumination with 652 nm (15 J) resulted in extensive damage to tumour tissue, with necrosis of up to 13 mm in diameter. Damage to normal liver tissue was mild and transient as serum aspartate aminotransferase and alanine aminotransferase levels normalized within a week after PDT treatment. Long-term effects of mTHPC-PDT were studied on day 28 after treatment. Regardless of drug dose and drug-light interval, PDT with mTHPC resulted in complete tumour remission in 27 out of 31 treated animals (87%), with only four animals in which tumour regrowth was observed. Non-responding tumours proved to be significantly larger (P < 0.001) in size before PDT treatment. This study demonstrates that mTHPC is retained in an intrahepatic tumour and that mTHPC-PDT is capable of inducing complete tumour remission of liver tumours.

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.

Interstitial laser hyperthermia, a new method in the management of fibroadenoma of the breast: A pilot study

BACKGROUND AND OBJECTIVE

This study attempts to evaluate the effect of interstitial laser hyperthermia in breast fibroadenomas as an outpatient procedure.

STUDY DESIGN/MATERIALS AND METHODS

In an uncontrolled prospective study, 27 patients younger than 35 years were subjected to laser phototherapy of their breast fibroadenomas. Under real-time ultrasound monitoring, Nd:YAG laser (1,064 nm wavelength) was used at 2 W for 300 sec (600 J) in a continuous wave mode to produce interstitial hyperthermia. Follow-ups were done at 2, 4, and 8 weeks. Subsequently, excision biopsy of residual lumps was performed.

RESULTS

There was significant decrease in clinical and sonographic sizes (P < 0.001). Follow-up ultrasound showed a progressive change of hyperechoic texture, from a heterogeneous to a nearly homogeneous one. There were minimal scars (2-3 mm) and no keloid or abscess formation.

CONCLUSION

Interstitial laser hyperthermia is a safe, precise, and minimally invasive outpatient procedure for in situ destruction of breast fibroadenomas.

MRI-guided radiofrequency thermal ablation of implanted VX2 liver tumors in a rabbit model: demonstration of feasibility at 0.2 T

Successful radiofrequency (RF) thermal ablation was performed on VX2 tumors implanted in 23 rabbit livers under magnetic resonance (MR) guidance using a C-arm-shaped low-field 0.2 T system. RF application and immediate postprocedure MRI of all animals was performed [T2-weighted, turbo short tau inversion recovery (STIR), T1-weighted before and after gadopentetate dimeglumine administration). Follow-up MRI with a superparamagnetic iron oxide (SPIO) contrast medium was performed in nine rabbits at 2 weeks and in four rabbits at 1 month post RF ablation. All livers were harvested for pathologic examination. T2-weighted and turbo-STIR images demonstrated the highest tumor-to-RF-thermal lesion contrast-to-noise ratios (CNRs; means 4.5 and 3.8, respectively) on postprocedure images; this was redemonstrated at 2- and 4-week follow-up imaging. T2-weighted imaging never overestimated pathologic lesion size by more than 2 mm, and the radiologic-pathologic correlation coefficient was not less than 0.90. In conclusion, MRI-guided RF thermal ablation in implanted liver tumor is feasible using a C-arm-shaped low-field 0.2 T system. The thermal lesion size can be most accurately monitored with T2-weighted and turbo-STIR images.

Long-term effects of interstitial laser coagulation in porcine liver with portal inflow occlusion: central versus peripheral lesions

PURPOSE

Interstitial laser coagulation (ILC) is an attractive modality for local destruction of unresectable hepatic metastases. Portal inflow occlusion considerably increases its destructive capacity, resulting in lesions 5 cm in diameter; however, effects on adjoining major intrahepatic structures are unknown. Therefore, the purpose of this study was to assess the effects of ILC with portal inflow occlusion on the central portion of the liver as compared to the peripheral portions.

MATERIALS AND METHODS

ILC was performed in pigs with portal inflow occlusion. Each animal received a single laser application with Nd:YAG light guided simultaneously through four interstitial fibers with 5 W per fiber during 6 minutes. Location of treatment was randomized to either central (n = 8) or peripheral (n = 8). Follow-up was for 1, 2, or 3 months with evaluation of liver functions and weight, as well as macroscopic and microscopic assessment of coagulated lesions and surrounding parenchyma.

RESULTS

There was no treatment-related morbidity or mortality. No obstructive cholestasis or bile leakage was found. At every moment of evaluation, coagulated volumes in the central group were smaller than in the peripheral lesions (P = .03). Large vessels contiguous to the lesions in the central group were always intact and indications of portal hypertension or thrombosis of hepatic veins were not found. There were no significant differences between the two groups (liver functions [P > or = .15] and weight [P = .69]).

CONCLUSION

ILC with portal inflow occlusion is a safe technique in the vicinity of vital structures in the liver of healthy pigs. These results justify studies to the feasibility and complication rate of portal inflow occlusion in patients with hepatic malignancies.

Radiofrequency thermal ablation of liver tumors

Chemotherapy and radiation therapy are ineffective against primary and secondary malignant hepatic tumors. Surgical resection has been considered the only potentially curative option, but few patients with hepatic tumors are candidates for surgery. Recent results suggest that radiofrequency thermal ablation may be an effective, minimally invasive technique for treating malignant hepatic tumors. Sonography is the primary technique for guiding percutaneous ablative procedures. We review the current research and clinical experience with radiofrequency thermal ablation for treating malignant hepatic tumors.

CT-monitored percutaneous cryoablation in a pig liver model: pilot study

PURPOSE

To determine the safety and feasibility of percutaneous cryoablation with computed tomographic (CT) guidance in a pig liver model.

MATERIALS AND METHODS

Nine angiographic balloons (mean diameter, 9 mm) were placed in the livers of seven domestic pigs (mean weight, 30.0 kg +/- 14.0 [SD]) as tumor-mimicking lesions. By using ultrasonographic and CT guidance, two 2.4- or 3.0-mm cryoprobes were placed flanking the balloon, and a 15-20-minute freezing process was performed. Hemostasis was achieved by placing absorbable cellulose fabric down the probe tract. After 24-96 hours, animals were sacrificed, and their livers were removed and were sectioned axially at 5-mm intervals for comparison with CT images.

RESULTS

All animals survived the procedure without complication. No serious hemorrhage was found in any case. Ice balls were readily visualized at CT because they appeared as areas of decreased attenuation (1.0 HU +/- 20.7) when compared with areas of normal liver (48.2 HU +/- 6.3, P < .05). The mean ablative margin was 1.7 cm, and only one of nine cases, the one with probe failure, had a positive margin. Beam-hardening artifact from the metal probes was present but did not interfere with the procedure. Ice-ball size and shape corresponded closely to the area of necrosis determined at histopathologic analysis.

CONCLUSION

CT-monitored percutaneous cryoablation is feasible and safe in this pig liver model.

Accuracy of MR phase mapping for temperature monitoring during interstitial laser coagulation (ILC) in the liver at rest and simulated respiration

The chemical shift or proton-resonance frequency (phase mapping) can be used to measure temperature changes. As a subtraction technique, it requires scans at exactly the same location, making it prone to respiration-induced artifacts. The accuracy of magnetic resonance (MR) phase mapping for temperature monitoring of interstitial laser coagulation (ILC) was therefore investigated in two ex vivo models with simulated respiration. MR temperatures were calibrated to interstitially measured temperature. Gradual cooling of a homogenous medium (gel) was monitored for four starting temperatures (room temperature, 40 degrees C, 50 degrees C, and 60 degrees C) during 30 min. Temperature increases were measured during ILC in ex vivo porcine liver with Nd:YAG for 6 min with 5 Watt. Experiments were performed at rest and with simulated respiratory motion (both n = 5). In liver, accuracy did not decrease with respiration simulation (P = 0.32), whereas a significant decline was found in the gel model (P = 0.002). In all experiments a small drift over time was observed between temperature determined with MR and thermoprobes. Correction for temperature-independent phase-shift at a reference location did not enhance agreement. Temperatures could be determined correctly by MR in the moving liver within a range of +/-3.5 degrees C after 6 min of laser application (95% confidence interval), justifying further pre-clinical studies.

Ultrasound-guided percutaneous treatment of hepatocellular carcinoma by radiofrequency hyperthermia with a 'cooled-tip needle'. A preliminary clinical experience

OBJECTIVE

Radiofrequency hyperthermia using the newly-developed 'cooled-tip' needle has recently been proposed as a therapeutic modality for hepatocellular carcinoma (HCC). Herein we report our preliminary results on feasibility and effectiveness of the thermal ablation of mono- or pauci-focal hepatocellular carcinoma with the cooled-tip needle.

MATERIALS AND METHODS

We treated 15 cirrhotic patients (mean age 68.8 years; 12 males; 14 HCV-positive; 13 in Child's Class A and 2 in Class B) with 20 hepatocellular carcinoma nodules (mean diameter 28.1 mm; range 10-43 mm; nine lesions with diameter greater than 3 cm). None of the patients had portal thrombosis and/or extrahepatic spread. We used a radiofrequency generator (100 W of power) connected to a 18 g perfusion electrode needle with an exposed tip of 2-3 cm. The circuit was closed through a dispersive electrode positioned under the patient's thighs. A peristaltic pump infused a chilled (2-5 degrees C) saline solution to guarantee the continuous cooling of the needle tip. The needle was placed into target lesions under US guidance. The interventional procedure was carried out in general anesthesia without intubation. Dynamic helical CT was carried out 15-20 days after thermal ablation to assess therapeutic efficacy.

RESULTS

In all, 38 areas of coagulation necrosis (at 1000-1200 mA for 10-15 min) were generated in 24 sessions in the 20 hepatocellular carcinoma nodules (mean 1.9 lesions per nodule and 1.2 sessions per nodule). Complete necrosis as assessed at dynamic CT (lack of enhancement during the arteriographic phase) was achieved in 75% of cases in a single session; after a second RF session success rate was 90% (18 out of 20 nodules). A self-limited pleurisy along with a 5-fold increase in transaminases occurred in one patient; a 3-fold elevation of transaminases was encountered in three other patients. During the follow-up (median 15 months) five patients had recurrent hepatocellular carcinoma with a 1-year disease free interval of 64%. Of the three recorded deaths, two were due to intrahepatic tumor diffusion.

CONCLUSIONS

In our experience radiofrequency hyperthermia with the cooled-tip needle afforded an effective and safe percutaneous ablative method for HCC in cirrhosis and shortened treatment time.

Does resection of small liver metastases from colorectal cancer improve survival of patients?

Because the size of metastases greatly affects their detection, we retrospectively investigated the influence of the size of liver metastases on survival after hepatic surgery. The subject group study consisted of 77 patients who underwent liver surgery for metastases from colorectal cancer. The survival rate after hepatic surgery was analysed using multivariate Cox's proportional hazards model with the following variables: (1) size of dominant metastases (Small: < 3 cm; Medium: > or = 3 cm and < 6 cm; Large: > or = 6 cm); (2) synchronous versus metachronous resection; (3) solitary versus multiple metastases. The size of dominant metastases (p = 0.035) and synchronous versus metachronous resection (p = 0.0009) were independently associated with survival after liver resection. No association was found, however, for solitary versus multiple metastases. The survival of the Large group was much poorer than that of the Small group (p = 0.0168) and that of the Medium group (p = 0.0205), with statistically significant differences. No statistically significant difference was seen between the Small and the Medium groups (p = 0.7963). This study showed that long-term survival following resection of metastases was much poorer when metastases were 6 cm or greater in diameter. With regard to metastases less than 6 cm in diameter, resection of the smallest of these (less than 3 cm) did not appear to improve survival.

Interstitial laser coagulation for hepatic tumours

BACKGROUND

The potential role of interstitial laser coagulation (ILC) for patients with irresectable hepatic tumours is currently being investigated. Since its introduction in 1983 it has evolved into an innovative minimally invasive technique.

METHODS

On the basis of a Medline literature search and the authors' experience, the principles, current state and prospects of ILC for hepatic tumours are reviewed.

RESULTS

Animal studies and early clinical studies have shown the safety and feasibility of ILC. The site of interest can be approached at laparoscopy or percutaneously and treatment is easily repeatable. Recent advances include the use of fibres with a cylindrical diffusing light-emitting tip, the length of which is adaptable to tumour diameter, water-cooled fibre systems, simultaneous multiple fibre application, and hepatic inflow occlusion during laser treatment. ILC allows complete destruction of tumours up to 5 cm in diameter. Currently a limitation is the lack of reliable real-time monitoring of laser-induced effects but progress in magnetic resonance imaging techniques should allow accurate temperature measurements to be obtained rapidly during treatment. However, the actual benefit of ILC in terms of patient survival remains to be investigated.

CONCLUSION

In terms of tools and experience, ILC has now been developed sufficiently to study its effect on survival of patients with irresectable hepatic tumours.

Percutaneous microwave coagulation therapy for solitary metastatic liver tumors from colorectal cancer: a pilot clinical study

OBJECTIVE

Percutaneous microwave coagulation therapy (PMCT) was performed for metachronous small solitary liver tumors measuring < or = 3.0 cm in diameter that had metastasized from colorectal cancer. PMCT was used for local control of the lesions, and the efficacy of this treatment was assessed.

METHODS

In 15 patients, a microwave electrode (specially designed for this purpose, 25 cm long and 2.0 mm thick) was inserted percutaneously into the tumor area under ultrasonic guidance. Microwaves at 80 watts were used to irradiate the tumor and the surrounding area.

RESULTS

Thirteen of the 15 metastatic tumors were radically ablated by 3-10 applications of microwave irradiation. Although the follow-up period was short (9-37 months), 10 patients survived. No recurrence has been detected in the treated area (except two foci where PMCT was insufficient), and no serious side effects or complications were encountered during or after the PMCT. In four of the five nonsurviving patients, death was due to metastases to the bone, brain, lung, or other areas of the liver despite complete local tumor control by PMCT.

CONCLUSION

PMCT is a safe and effective treatment for metachronous small liver tumors that have metastasized from colorectal cancer.

Automatic ultrasound determination of thermal coagulation front during laser tissue heating

Thermal therapies using laser, microwaves, radio frequency radiation, and high intensity focused ultrasound have shown great promise for minimally invasive treatment of benign and malignant lesions. To treat tissue effectively and safely, techniques that could monitor the advancement of coagulation front during treatment are highly desirable. This paper presents a noninvasive ultrasound technique for automatically determining the propagation of coagulation damage front during laser tissue heating. The basic assumption underlying this technique is that when coagulation is taking place in a tissue, owing to thermally induced structure changes in tissue, the waveform of echo signal scattered from that treated region should be changing accordingly. We first track echoes scattered from many small tissue regions during heating using a cross-correlation echo-tracking technique. We then use the waveform-change information to determine the position of coagulation front via an automatic calculation procedure. To test our technique, we carried out 35 experiments in which we irradiated fresh canine liver samples with a Nd:YAG laser (1064-nm wavelength) at various light fluence (62 to 167 W/cm(2)) and exposure time (20 to 350 s). A 13-mm diameter 10-MHz broadband single-element spherical focused ultrasound transducer was used to detect the thermal coagulation front. The root mean square difference between ultrasonically and visually determined coagulation depths was 0.77 mm. This good agreement between visually inspected and ultrasonically determined coagulation depths shows the potential of our technique for monitoring coagulative tissue damage during thermal therapy.

A theoretical comparison of energy sources--microwave, ultrasound and laser--for interstitial thermal therapy

A number of heating sources are available for minimally invasive thermal therapy of tumours. The purpose of this work was to compare, theoretically, the heating characteristics of interstitial microwave, laser and ultrasound sources in three tissue sites: breast, brain and liver. Using a numerical method, the heating patterns, temperature profiles and expected volumes of thermal damage were calculated during standard treatment times with the condition that tissue temperatures were not permitted to rise above 100 degrees C (to ensure tissue vaporization did not occur). Ideal spherical and cylindrical applicators (200 microm and 800 microm radii respectively) were modelled for each energy source to demonstrate the relative importance of geometry and energy attenuation in determining heating and thermal damage profiles. The theoretical model included the effects of the collapse of perfusion due to heating. Heating patterns were less dependent on the energy source when small spherical applicators were modelled than for larger cylindrical applicators due to the very rapid geometrical decrease in energy with distance for the spherical applicators. For larger cylindrical applicators, the energy source was of greater importance. In this case, the energy source with the lowest attenuation coefficient was predicted to produce the largest volume of thermally coagulated tissue, in each tissue site.

High-dose mitomycin C in isolated hyperthermic liver perfusion for unresectable liver metastases

In order to reduce systemic side effects and increase intrahepatic mitomycin C (MMC) concentrations, isolated hyperthermic liver perfusion (IHLP) has been performed using MMC. This article describes the pharmacokinetics of MMC in IHLP and presents our clinical experience with its use in six patients suffering from unresectable liver metastases. Primary tumors consisted of colorectal carcinomas in three cases, breast cancer in two, and a choroidal melanoma in one. Dosages of MMC varied between 0.5 and 1.0 mg MMC/kg body weight. MMC was added as a bolus directly into the extracorporeal circuit. Intrahepatic temperature was elevated to 40.0-41.0 degrees C by hyperthermic perfusion. MMC concentrations were measured in peripheral blood (preperfusion, then at 5, 30, and 55 min during perfusion, and finally at 5 and 60 min and 6 and 24 h after perfusion) and in recirculating perfusate (5, 30, and 55 min). While markedly elevated MMC concentrations (maximum 6290 ng/mL) were found in the liver perfusate, systemic concentrations remained low (maximum 45 ng/mL), indicating no considerable leakage. MMC concentrations in the perfusate constantly decreased during perfusion. After rinsing with 1500 mL saline, a mean concentration of 52.5+/-33 ng MMC/mL was measured in the washout from 5 patients. In 1 patient with a colorectal carcinoma, MMC concentrations in the perfusion medium were 10-fold and in the plasma 2-fold higher than in the other patients. This high MMC concentration caused severe intrahepatic vascular damage and finally led to the patient's death. In conclusion, IHLP and intrahepatic perfusion with MMC resulted in a high response of hepatic tumors. Systemic exposure of MMC can be reduced effectively by isolated perfusion. However, hepatic toxicity of MMC must be considered.

Ultrasound imaging of thermal therapy in in vitro liver

The objective of this work was to image liver tissue heated to temperatures below the vaporization threshold as a function of time, to test the feasibility of real-time ultrasound monitoring to control lesion size during minimally invasive thermal therapy (MITT). Two experiments were devised. In one experiment, a thermal gradient was established in a rectangular volume of tissue to correlate changes in ultrasound image echogenicity (B-mode image brightness) with tissue temperature. In the other, a thermal lesion was produced in a rectangular volume of tissue by an interstitial microwave antenna, and the progression of the lesion was monitored by ultrasound. In both experiments, the echogenicity of the tissue increased slightly for tissue temperatures up to 40 degrees C, but became lower than that of unheated tissue for temperatures above 40 degrees C. In the second experiment, images of the lesion were compared with a photograph of the lesion taken after the experiment was complete. The final lesion was composed of two concentric regions--an inner region of heavily coagulated tissue and an outer region of less-damaged tissue. These two damaged regions indicated that increased ultrasound attenuation was largely responsible for the decreased echogenicity observed in the ultrasound images, and the increase in echogenicity of tissue heated to temperatures up to 40 degrees C is thought to be due to decreased ultrasound attenuation at these temperatures.

Sonographically guided microwave coagulation treatment of liver cancer: an experimental and clinical study

OBJECTIVE

Percutaneous microwave coagulation was performed with a modified system in animal experiments and in a clinical study to evaluate this technique as a treatment option for liver cancer.

SUBJECTS AND METHODS

As an in vitro study, a microwave electrode was inserted 5-6 cm into separated egg white, homogenate of pig liver, and pig liver, with different power outputs and different lengths of inner conductors. In the animal experiment, the sonographically guided coagulation was performed percutaneously nine times and at laparotomy 43 times on 17 adult dogs. The thermal needles were placed parallel to and 5 mm, 8-12 mm, and 15 mm from the electrode. Clinically, 41 patients with hepatocellular carcinoma and 10 patients with hepatic metastases were treated with a 60-W microwave emission for 240-300 sec.

RESULTS

Microwave coagulation using the modified system at 60 W for 300 sec produced a necrosis volume of 3.7 x 2.6 x 2.6 cm. The coagulated volume was elliptic when the exposed inner conductor of the electrode was 27 mm. The temperature at the periphery was 62.0 +/- 5.8 degrees C. During a mean follow-up period of 23 months, in 41 patients with hepatocellular carcinoma, 79% (46/58) of lesions became smaller, and the intratumoral blood flow disappeared in 89% (47/53). All tumors showed decreased density on unenhanced CT, and 84% (32/38) of tumors showed no enhancement on contrast-enhanced CT. In 21 patients with an elevated alpha-fetoprotein level, the level decreased in all 21 and was normalized in 17. A second biopsy on 19 patients showed complete destruction of tumor in 18. In 10 patients with hepatic metastases, the mean follow-up period was 13 months. Shrinkage of lesions occurred in 84% (21/25), and the blood flow inside the tumor disappeared in 75% (12/16) of lesions. Seventy-three percent (8/11) of the nodules showed no enhancement. A second biopsy on six patients showed complete necrosis in five.

CONCLUSION

Sonographically guided microwave coagulation performed with this modified system was an effective and safe treatment for liver cancer.

Interstitial laser photocoagulation of normal lung parenchyma in rats

BACKGROUND

Management of peripheral lung tumours may be risky in patients with poor lung function or in the elderly. A new possibility is interstitial laser photocoagulation (ILP) in which tumours are gently coagulated using thin laser fibres placed percutaneously under radiological guidance. This could have a useful palliative role in selected patients, but to be safe the effects on normal lung parenchyma must first be understood. This paper describes the creation and healing of ILP lesions in the normal rat lung.

METHODS

ILP was performed using single laser fibres placed percutaneously in the left lung of normal rats under general anaesthetic with radiological guidance (laser power 1-3 W at 805 nm, treatment time 250-1000 s). The lesion size and healing were studied in rats killed at times from three days to six months after treatment, the bursting pressure was measured, and any complications noted.

RESULTS

Zones of necrosis up to 12 mm in diameter were produced, the size depending on the laser power and treatment time. Histological examination showed typical thermal effects with complete healing with fibrosis by two months. The effect was very localised with remarkably little effect on the structure and function of the rest of the lung. Adverse effects in the lung parenchyma only occurred if the ILP lesion involved the hilar vessels or the oesophagus, causing pulmonary congestion and perforation, respectively. Pneumothorax was seen in 6% of cases.

CONCLUSIONS

ILP with a single fibre can produce a localised zone of necrosis in normal lung parenchyma which heals safely and which has little effect on the rest of the lung. Further study of this technique using multiple fibres in a larger animal model is warranted to see if it is feasible and safe to produce a large enough volume of necrosis to be of value in the treatment of small peripheral lung tumours in patients who are unsuitable for surgery or palliative radiotherapy.

Comparison between interstitial laser thermotherapy and excision of an adenocarcinoma transplanted into rat liver

The aim of this study was to compare interstitial laser thermotherapy with excision of a liver tumour. A dimethylhydrazine-induced adenocarcinoma was transplanted (implanted if not stated otherwise) into the left lateral lobe of the rat liver, and treatment was performed 8 days later. In the main experiment, rats were treated with resection of the tumour-bearing lobe or underwent interstitial laser thermotherapy, which was performed at a steady-state temperature of 46 degrees C for 30 min, 3 mm from the tumour margin. The incidence and extent of intraperitoneal spread was smaller after laser thermotherapy than after resection of the tumour-bearing lobe, with no difference in local control. Metastatic spread after resection of the median liver lobe was similar to that observed after sham procedures for thermotherapy or resection, suggesting that the advantage of thermotherapy was not due to a difference in surgical trauma. Additional studies showed that laser thermotherapy reduced intraperitoneal spread when treatment was suboptimal or in a tumour inoculation model and suggested that immunological mechanisms might be involved. It is concluded that interstitial laser thermotherapy reduces spread of liver tumour compared with resection.

New applications of ultrasonography: interventional ultrasound

Since 1975-80, worldwide but mostly in Europe and Japan, sonography has become the imaging technique of choice for guiding percutaneous interventional procedures for diagnostic or therapeutic purposes. In the last 10 years, the most important advances in interventional ultrasound have occurred in therapeutic applications, fostering and facilitating the development of the so-called minimally-invasive techniques. Among all these new applications for the treatment of fluid collections, inflammatory diseases, benign and malignant tumors, the most recent dramatic advances have occurred in primary and secondary liver malignancies, which will be the focus of this review. The rationale for the local treatment of primary and secondary liver cancers differs according to the success of conventional treatments (e.g. surgery and chemotherapy) and to the survival rates of such conditions, depending on clinical stage, patient age, associated diseases, and so on. Ultrasound-guided percutaneous therapies for liver cancer can be divided into: (1) direct intratumoral injection of chemical agents, such as ethanol, hot saline and acetic acid; and (2) thermally-mediated techniques, such as radiofrequency ablation, interstitial laser photocoagulation, microwave therapy or cryotherapy. Through different mechanisms of action, all these methods induce cell death by coagulative necrosis. The clinical efficacy of some of these techniques has been clearly established, like percutaneous ethanol injection in the treatment of hepatocellular carcinoma. In contrast, experience with the other techniques is much more preliminary, mostly due to the limited availability of sufficient clinical trials and to the fascinating speed of technological development. We review the state-of-the-art of the two most promising techniques, namely radiofrequency ablation and interstitial laser photocoagulation, and the present preliminary clinical data in the treatment of hepatocellular carcinomas and liver metastases. Radiofrequency energy is delivered to the tumors by means of electrode-needles (14-17 G) electrically insulated along all but the distal portion of the shaft and percutaneously introduced into the targets under ultrasound guidance. In the short history of this method, several technologies have been tested and used, but 'multiple-hook' and 'internal-cooling' electrodes are currently the leading choices, providing large necrosis volumes (up to 5 cm in diameter for a single 12-min application with an array of three internal-cooling electrodes) in short sessions, under local or general anesthesia. Radiofrequency ablation has proved its usefulness in the treatment of hepatocellular carcinomas, achieving complete necrosis in over 85-90% of cases in lesions smaller than 5 cm in diameter and in single sessions, with a low rate (< 10%) of local recurrences. In the treatment of liver metastases, whose very poor responsiveness to percutaneous ethanol injection and other 'chemical' therapies is extensively reported in the literature, radiofrequency ablation has 65-75% reported complete efficacy in the control of local tumor growth in lesions not exceeding 4 cm. Such great efficacy has been so far coupled with very low rates of major side-effects (< 2%), most of them requiring no surgical repair. Interstitial laser photocoagulation induces thermally-mediated coagulation through thin optic (Nd:YAG) fibers percutaneously inserted into the target under ultrasound guidance. Multiple fibers (beam splitters) are usually required to achieve a sufficiently wide necrosis volume. The reported success rate (complete necrosis and local control of tumor growth) ranges 45-75%) of the lesions, mostly liver metastates from colorectal carcinoma. An equally low rate of complications is reported for interstitial laser photocoagulation as for radiofrequency ablation, that is no more than 2-3% of cases. (ABSTRACT TRUNCATED)

Interventional radiology with laser in bone and joint

Laser energy is able to ablate, coagulate, and vaporize tissues. Its transmissibility in thin optical fibers makes it an ideal tool for use in percutaneous procedures. This article describes two applications in interventional musculoskeletal radiology. In percutaneous laser disc decompression the laser source is used to vaporize a small portion of the nucleus pulposus. In interstitial laser photocoagulation of osteoid osteoma the laser energy is used to coagulate and destroy the tumor by direct heating.