New applications of ultrasonography: interventional ultrasound

Reactive X (where X = O, N, S, C, Cl, Br, and I) species nanomedicine

Reactive oxygen, nitrogen, sulfur, carbonyl, chlorine, bromine, and iodine species (RXS, where X = O, N, S, C, Cl, Br, and I) have important roles in various normal physiological processes and act as essential regulators of cell metabolism; their inherent biological activities govern cell signaling, immune balance, and tissue homeostasis. However, an imbalance between RXS production and consumption will induce the occurrence and development of various diseases. Due to the considerable progress of nanomedicine, a variety of nanosystems that can regulate RXS has been rationally designed and engineered for restoring RXS balance to halt the pathological processes of different diseases. The invention of radical-regulating nanomaterials creates the possibility of intriguing projects for disease treatment and promotes advances in nanomedicine. In this comprehensive review, we summarize, discuss, and highlight very-recent advances in RXS-based nanomedicine for versatile disease treatments. This review particularly focuses on the types and pathological effects of these reactive species and explores the biological effects of RXS-based nanomaterials, accompanied by a discussion and the outlook of the challenges faced and future clinical translations of RXS nanomedicines.

Ultrasound-guided injections of the equine head and neck: review and expert opinion

Ultrasound-guided injections can be used for a wide variety of conditions in the horse, including both diagnostic and therapeutic applications. Benefits of ultrasound guidance include more accurate deposition of injectate compared with blind approaches. Improved identification of vital structures, including nerves and blood vessels, allows their avoidance and thus reduces procedure-associated complications. Validation of such ultrasound-guided techniques has shown that they can be easily learnt by inexperienced veterinarians, assuming a proper knowledge of the sonographic anatomy. In many cases they can be employed in the field with a high level of accuracy, using widely available equipment, and with complete adherence to the sterility principles. Many ultrasound-guided injection techniques of the axial skeleton in the horse have been described in past years, enabling the equine veterinarian to perform more accurate treatments of specific anatomical areas. The goal of this review is to discuss diagnostic and therapeutic ultrasound-guided injection techniques of the skull and cervical spine in the horse, including those for the retrobulbar space, maxillary and inferior alveolar nerves, atlanto-occipital and atlanto-axial junctions, and cervical articular process joints, as well as the 1st cervical nerve, the C2 and C3 nerve plexus, and the 6th, 7th, and 8th cervical nerve roots.

Challenges Facing Percutaneous Ablation in the Treatment of Hepatocellular Carcinoma: Extension of Ablation Criteria

As an emerging minimally invasive treatment method, percutaneous ablation is more and more widely used in the treatment of liver tumors. It has been recommended by guidelines for diagnosis and treatment of hepatocellular carcinoma (HCC) as a curative treatment alongside surgical resection and liver transplantation. In recent years, with the continuous advancement and innovation of percutaneous ablation technologies, their clinical efficacy and safety have been significantly improved, which has led to the expanded application of percutaneous ablation in the treatment of HCC—more and more patients who were previously considered unsuitable for ablation therapies are now being treated with percutaneous ablation. Obviously, percutaneous ablation can reduce the risk of treatment changes from curative strategies to palliative strategies. Based on clinical practice experience, this review enumerates the advantages and disadvantages of different ablative modalities and summarizes the existing combinations of ablation techniques, thus will help clinicians choose the most appropriate ablative modality for each patient and will provide scientific guidance for improving prognosis and making evidence-based treatment decisions. In addition, we point out the challenges and future prospects of the ablation therapies, thereby providing direction for future research.

Three-dimensional interventional photoacoustic imaging for biopsy needle guidance with a linear array transducer

Needle placement is important for many clinical interventions, such as tissue biopsy, regional anesthesia and drug delivery. It is essential to visualize the spatial position of the needle and the target tissue during the interventions using appropriate imaging techniques. Based on the contrast of optical absorption, photoacoustic imaging is well suited for the guidance of interventional procedures. However, conventional photoacoustic imaging typically provides two-dimensional (2D) slices of the region of interest and could only visualize the needle and the target when they are within the imaging plane of the probe at the same time. This requires great alignment skill and effort. To ease this problem, we developed a 3D interventional photoacoustic imaging technique by fast scanning a linear array ultrasound probe and stitching acquired image slices. in vivo sentinel lymph node biopsy experiment shows that the technique could precisely locate a needle and a sentinel lymph node in a tissue volume while a perfusion experiment demonstrates that the technique could visualize the 3D distribution of injected methylene blue dye underneath the skin at high temporal and spatial resolution. The proposed technique provides a practical way for photoacoustic image-guided interventions.

Evaluation of tablet ultrasound for routine abdominal interventional procedures

AIM

The aim of the study was to establish if a novel tablet ultrasound (US) may replace a high-end US machine during routine interventional radiology activities.

MATERIALS AND METHODS

Thirty consecutive patients were evaluated by two operators comparing the performance of the new US tablet system (VISIQ, Philips Healthcare) against a high-end US system (iU22, Philips Healthcare) using a curved probe (C5-2). A structured questionnaire was used to rank on a 4-point scale the ability of each system to locate a target as detected by previous examinations and visualize needles and path during an interventional procedure. Necessity for conversion from the tablet US to the high-end US system was registered; body mass index (BMI) was annotated for each patient.

RESULTS

Agreement between the operators was found for every patient. Mean patient BMI was 25 (range 17-34). Image quality of the tablet US was considered insufficient in 1 case to visualize the target and in another case to visualize the needle. Mean target image quality was superior with the high-end US system, while needle visibility scored higher with the tablet US. Conversion to the high-end system was registered in 40 % of cases: in most cases (66.6 %) the decision was due to the absence of a dedicated needle guide for the tablet US.

CONCLUSIONS

The novel tablet US was found to provide sufficient image quality for the majority of routine interventional procedures. Dedicated accessories and additional experience with this new generation US device may be needed to replace bulky high-end US systems.

Multimodal liver-directed management of neuroendocrine hepatic metastases

A preponderance of patients with neuroendocrine tumors (NETs) will experience hepatic metastases during the course of their disease. Many diagnoses of NETs are made only after the neoplasms have spread from their primary gastroenteropancreatic sites to the liver. This paper reviews current evidence-based treatments for neuroendocrine hepatic metastases, encompassing surgery, hepatic artery embolization (HAE) and chemoembolization (HACE), radioembolization, hepatic artery infusion (HAI), thermal ablation (radiofrequency, microwave, and cryoablation), alcohol ablation, and liver transplantation as therapeutic modalities. Consideration of a multidisciplinary approach to liver-directed therapy is strongly encouraged to limit morbidity and mortality in this patient population.

Percutaneous computed tomography fluoroscopy–guided conformal ultrasonic ablation of vertebral tumors in a rabbit tumor model

Object

Radiofrequency ablation (RFA) has proven to be effective for treatment of malignant and benign tumors in numerous anatomical sites outside the spine. The major challenge of using RFA for spinal tumors is difficulty protecting the spinal cord and nerves from damage. However, conforming ultrasound energy to match the exact anatomy of the tumor may provide successful ablation in such sensitive locations. In a rabbit model of vertebral body tumor, the authors have successfully ablated tumors using an acoustic ablator placed percutaneously via computed tomography fluoroscopic (CTF) guidance.

Methods

Using CTF guidance, 12 adult male New Zealand White rabbits were injected with VX2 carcinoma cells in the lowest lumbar vertebral body. At 21 days, a bone biopsy needle was placed into the geographical center of the lesion, down which an acoustic ablator was inserted. Three multisensor thermocouple arrays were placed around the lesion to provide measurement of tissue temperature during ablation, at thermal doses ranging from 100 to 1,000,000 TEM (thermal equivalent minutes at 43°C), and tumor volumes were given a tumoricidal dose of acoustic energy. Animals were monitored for 24 hours and then sacrificed. Pathological specimens were obtained to determine the extent of tumor death and surrounding tissue damage. Measured temperature distributions were used to reconstruct volumetric doses of energy delivered to tumor tissue, and such data were correlated with pathological findings.

Results

All rabbits were successfully implanted with VX2 cells, leading to a grossly apparent spinal and paraspinal tissue mass. The CTF guidance provided accurate placement of the acoustic ablator in all tumors, as corroborated through gross and microscopic histology. Significant tumor death was noted in all specimens without collateral damage to nearby nerve tissue. Tissue destruction just beyond the margin of the tumor was noted in some but not all specimens. No neurological deficits occurred in response to ablation. Reconstruction of measured temperature data allowed accurate assessment of volumetric dose delivered to tissues.

Conclusions

Using a rabbit intravertebral tumor model, the authors have successfully delivered tumoricidal doses of acoustic energy via a therapeutic ultrasound ablation probe placed percutaneously with CTF guidance. The authors have thus established the first technical and preclinical feasibility study of controlled ultrasound ablation of spinal tumors in vivo.

Autoregressive moving average modeling for spectral parameter estimation from a multigradient echo chemical shift acquisition

The authors investigated the performance of the iterative Steiglitz-McBride (SM) algorithm on an autoregressive moving average (ARMA) model of signals from a fast, sparsely sampled, multiecho, chemical shift imaging (CSI) acquisition using simulation, phantom, ex vivo, and in vivo experiments with a focus on its potential usage in magnetic resonance (MR)-guided interventions. The ARMA signal model facilitated a rapid calculation of the chemical shift, apparent spin-spin relaxation time (T2*), and complex amplitudes of a multipeak system from a limited number of echoes (< or equal 16). Numerical simulations of one- and two-peak systems were used to assess the accuracy and uncertainty in the calculated spectral parameters as a function of acquisition and tissue parameters. The measured uncertainties from simulation were compared to the theoretical Cramer-Rao lower bound (CRLB) for the acquisition. Measurements made in phantoms were used to validate the T2* estimates and to validate uncertainty estimates made from the CRLB. We demonstrated application to real-time MR-guided interventions ex vivo by using the technique to monitor a percutaneous ethanol injection into a bovine liver and in vivo to monitor a laser-induced thermal therapy treatment in a canine brain. Simulation results showed that the chemical shift and amplitude uncertainties reached their respective CRLB at a signal-to-noise ratio (SNR) > or =5 for echo train lengths (ETLs) > or =4 using a fixed echo spacing of 3.3 ms. T2* estimates from the signal model possessed higher uncertainties but reached the CRLB at larger SNRs and/or ETLs. Highly accurate estimates for the chemical shift (<0.01 ppm) and amplitude (<1.0%) were obtained with > or =4 echoes and for T2*(<1.0%) with > or =7 echoes. We conclude that, over a reasonable range of SNR, the SM algorithm is a robust estimator of spectral parameters from fast CSI acquisitions that acquire < or =16 echoes for one- and two-peak systems. Preliminary ex vivo and in vivo experiments corroborated the results from simulation experiments and further indicate the potential of this technique for MR-guided interventional procedures with high spatiotemporal resolution approximately 1.6 x 1.6 x 4 mm3 in < or =5 s.

Ultrasound monitoring of temperature change in liver tissue during laser thermotherapy: 10 degrees C intervals

In thermal tissue ablation, it is very important to control the increase in the temperature for having an efficient ablation therapy. We conducted this study to determine the efficacy of measuring pixel shift of ultrasound B-mode images as a function of change in tissue temperature. By fixing some micro thermocouples in liver tissues, temperature at different points was monitored invasively in vitro during laser-induced thermotherapy. According to our results optimum power and exposure time were determined for ultrasound temperature monitoring. Simultaneously, noninvasive temperature monitoring was performed with ultrasound B-mode images. These images were saved on computer from 25 degrees C to 95 degrees C with 10 degrees C steps. The speed of sound changes with each 10 degrees C temperature change that produce virtual shifts in the scatter positions. Using an image processing method, the pixel shift due to 10 degrees C temperature change was extracted by motion detection. The cubic regression function between the mean pixel shifts on ultrasound B-mode images caused by the change in speed of sound which in turn was a function of the mean change in temperature was evaluated. When temperature increased, pixel shift occurs in ultrasound images. The maximum pixel shift was observed between 60 to 70 degrees C. After 70 degrees C, the local pixel shift due to change in the speed of sound in liver tissue had an irregular decreasing. Pearson correlation coefficient between invasive and non-invasive measurements for 10 degrees C temperature changes was 0.93 and the non-linear function was suitable for monitoring of temperature. Monitoring of changes in temperature based on pixel shifts observed in ultrasound B-mode images in interstitial laser thermotherapy of liver seems a good modality.

Ultrasound-guided interventional radiology in critical care

Ultrasound-guided intervention is becoming an increasingly popular and valuable tool in the critical care setting. In general, image-guided procedures can expedite wait times and increase the accuracy, safety, and efficacy of many procedures commonly performed within intensive care units. In the intensive care unit setting, ultrasound has particular advantages over other imaging modalities such as computed tomography and fluoroscopy, including real-time visualization, portability permitting bedside procedures, and reduced exposure to nephrotoxic contrast agents. We review the technical and procedural aspects of a number of ultrasound-guided interventions appropriate for critical care patients. These include central venous catheter deployment, thoracentesis, paracentesis, and drainage of a wide variety of abscesses, and percutaneous nephrostomy, percutaneous cholecystectomy, and inferior vena cava filter placement. Although we believe ultrasound is significantly underutilized in critical care today, we anticipate that with the improvement of ultrasound technology and the innovation of new ultrasound-guided procedures, the role of ultrasound in the intensive care unit will continue to expand, with bedside ultrasound-guided interventions increasingly becoming the norm.

Percutaneous CT-guided radiofrequency ablation of pulmonary malignant tumors: preliminary report

OBJECTIVE

Radiofrequency ablation (RFA) is frequently used for hepatic malignant tumors, but few reports discuss its use for lung tumors. We report our pilot clinical study with RFA for the treatment of pulmonary malignant tumors.

PATIENTS AND METHODS

Five patients with histologically-proven malignant primary and three metastatic lung tumors underwent a total of 11 RFA procedures. RFA was performed in two patients as palliative therapy to shrink the tumors and in six as radical therapy. All RFA was performed by the percutaneous CT-guided approach.

RESULTS

Three tumors were completely ablated by one procedure. Contrast CT revealed cyst cavity formation or scar formation at these three tumors. Gd contrast-enhanced MRI revealed cystic lesions with ringlike enhancement or scar formation. Partial ablation after the first procedure was noted in six tumors including the two palliative cases. RF ablation was well tolerated in all patients. Intraprocedural complications included six cases of pneumothorax (one patient required chest tube placement), six cases of pleural effusion (two patients required chest tube placement), one case of pneumonia (improved immediately with antibiotics), three cases of bloody sputum (mild), and six cases of chest pain (all cases after the procedure).

CONCLUSIONS

This pilot clinical study demonstrates that CT-guided RFA is a relatively safe and effective treatment option for malignant lung tumors. Additional trials are needed to determine the safety, efficacy, and optimal indications of RFA.

Remote thermometry to avoid complications in radiofrequency ablation

Percutaneous image-guided radiofrequency ablation (RFA) of tumors has the potential risk for thermal damage to nearby normal collateral tissues. Thus, the goal of creating a sufficient area of tumor necrosis must be weighed against the risk for injury to collateral tissues. In this study, remote thermistors were used to monitor temperatures near collateral structures during tumor RFA. Four unique cases are described. When temperature-sensitive structures are near the target lesion, remote thermometry could further increase the safety of this evolving minimally invasive procedure.

Percutaneous ultrasound-guided radiofrequency heat ablation for treatment of hyperthyroidism in cats

OBJECTIVE

To determine efficacy and safety of percutaneous radiofrequency heat ablation for treatment of hyperthyroidism in cats.

DESIGN

Prospective study.

ANIMALS

9 cats.

PROCEDURE

Hyperthyroidism was diagnosed via clinical signs and high serum total (TT4) and free thyroxine (fT4) concentrations. One or 2 hyperfunctional cervical thyroid nodules were detected by use of scintigraphy and ultrasonography. If cats had 1 abnormal thyroid lobe, heat ablation was performed on that lobe; if cats had 2 abnormal lobes, heat ablation was applied to the larger lobe. Overall, heat ablation was performed 14 times in the 9 cats. Clinical signs and serum TT4, fT4, and calcium concentrations were monitored daily for 2 days after the procedure, weekly for the first month, and then monthly. Laryngeal function was evaluated and cervical ultrasonography and thyroid scintigraphy were also performed. Monitoring continued for as long as 9 months after heat ablation if a cat became euthyroid or until an owner chose an alternative treatment because of recurrence of hyperthyroidism.

RESULTS

Serum TT4 and fT4 concentrations transiently decreased after all 14 heat ablation procedures (< or = reference range after 10 of 14 treatments) within 2 days after the procedure. Cats were euthyroid for 0 to 18 months (mean, 4 months). Hyperthyroidism recurred in all cats. Adverse effects included transient Horner's syndrome (2 cats) and laryngeal paralysis without clinical signs (1 cat).

CONCLUSIONS AND CLINICAL RELEVANCE

Percutaneous heat ablation as a treatment for hyperthyroidism in cats is effective transiently but not permanently.

Tumor debulking by radiofrequency ablation in hypertrophic pulmonary osteoarthropathy associated with pulmonary carcinoma

A 73-year-old male with stage IV lung adenocarcinoma presented with leg swelling and clubbing of the fingers on both hands upon physical examination, and bone scintigrams demonstrated marked accumulation of 99mTc-MDP in the long bones adjacent to the patellae. A diagnosis of hypertrophic pulmonary osteoarthropathy associated with primary lung cancer was made. Radiofrequency ablation (RFA) was utilized for cytoreduction, because the patient refused chemotherapy. One-month follow-up CT scans revealed low density of the ablated area associated with ablation necrosis. Cytoreduction by RFA rapidly alleviated the arthralgia and swelling, but not the clubbing of fingers. Follow-up bone scintigrams demonstrated a reduction in patellar uptake after RFA.

Laparoscopic in situ ablation of liver cancer with cryotherapy and radiofrequency ablation

BACKGROUND

In situ ablation has potential for the treatment of patients with liver cancer either as a single-modality treatment or in combination with liver resection.

METHODS

Laparoscopy and intraoperative ultrasonography was used to target cryotherapy and radiofrequency ablation. Thirty-eight patients with 146 liver lesions were treated between January 1995 and December 2000 using cryotherapy alone (nine patients), combined cryotherapy and radiofrequency (eight), radiofrequency alone (15) and in situ ablation with liver resection (six). Cancers treated were metastases from colorectal tumours (n = 25), hepatocellular carcinoma (n = 5), and neuro endocrine (n = 5), melanoma (n = 2) and renal cell (n = 1) metastases. Complications and survival after in situ ablation were compared with age- and disease-matched controls treated with systemic chemotherapy.

RESULTS

The mean age was 61.6 years. At mean follow-up of 26.6 (range 3-62, median 26) months, 22 patients were alive. Survival was increased following in situ ablation compared with that in controls (P < 0.001). Local recurrence at the ablation site was noted in 12 of 44 lesions following cryotherapy and in 20 of 102 lesions after radiofrequency ablation, and new disease in the liver was found in six of 17 and six of 29 patients respectively. The complication rate was higher with cryotherapy than with radiofrequency ablation (four of 17 versus one of 29). Intraoperative ultrasonography identified 14 new hepatic lesions (10 per cent) not seen on preoperative imaging.

CONCLUSION

Laparoscopic in situ ablation should include ultrasonography to stage the disease. In situ ablation appears to have a survival benefit and should be considered for the treatment of liver cancer in appropriate patients.

MR temperature measurement in liver tissue at 0.23 T with a steady-state free precession sequence

MRI can be used for monitoring temperature during a thermocoagulation treatment of tumors. The aim of this study was to demonstrate the suitability of a 3D steady-state free precession sequence (3D Fast Imaging with Steady-State Precession, 3D TrueFISP) for MR temperature measurement at 0.23 T, and to compare it to the spin-echo (SE) and spoiled 3D gradient-echo (3D GRE) sequences. The optimal flip angle for the TrueFISP sequence was calculated for the best temperature sensitivity in the image signal from liver tissue, and verified from the images acquired during the thermocoagulation of excised pig liver. Factors influencing the accuracy of the measured temperatures are discussed. The TrueFISP results are compared to the calculated values of optimized SE and 3D GRE sequences. The accuracy of TrueFISP in the liver at 0.23 T, in imaging conditions used during thermocoagulation procedures, is estimated to be +/-3.3 degrees C for a voxel of 2.5 x 2.5 x 6 mm(3) and acquisition time of 18 s. For the SE and GRE sequences, with similar resolution and somewhat longer imaging time, the uncertainty in the temperature is estimated to be larger by a factor of 2 and 1.2, respectively.

Radio-frequency ablation for symptom control in a patient with metastatic pancreatic insulinoma

Malignant insulinomas are very rare endocrine tumours with a variable clinical course. We describe a 51-year-old man who had two large insulinomas resected from the body of the pancreas and 19 years later, having again become symptomatic, was found to have hepatic metastases. Medical treatment with diazoxide and octreotide failed to control his symptoms, but repeated hepatic embolization effected both symptomatic and biochemical improvements for a further 5 years. When symptoms recurred but further embolization failed to control his symptoms the hepatic metastases were treated by outpatient percutaneous radio-frequency ablation. He remains symptom-free 18 months later and levels of insulin and pro-insulin have nearly normalized. The survival, with liver metastases, for 27 years in a man with a malignant insulinoma has not been described previously. Malignant insulinoma may follow a rather indolent course and symptoms respond well to locally destructive therapies. Hepatic embolization is less traumatic than hepatic lobe resection and radio-frequency ablation offers an alternative if vascular access to the tumour is no longer possible.

Alternative techniques for the treatment of colon carcinoma metastases in the liver: current status in The Netherlands

BACKGROUND

Review of current treatment modalities for liver metastases resulting from colorectal cancer.

METHODS

Literature review.

RESULTS

An increasing number of techniques are available for the treatment of colorectal liver metastases. When it is not possible to use the current gold standard, radical surgical resection, many patients can be treated with alternative techniques. Chemotherapy in its present form must be considered as purely palliative, perhaps with the exclusion of isolated liver perfusion: however, this therapy should still be considered as experimental. Most other possible treatments focus on local destruction of the metastases. This can be achieved using either immuno-guided techniques (tumor antibodies which carry a local active agent), direct local application of a toxic agent (injection) or thermo therapy, which has been applied in patients on a large scale. Thermo therapy involves either localized heating, by means or laser photocoagulation or radiofrequency or microwave ablation, or localized freezing using cryo probes.

CONCLUSIONS

Local destruction of liver metastases, especially by means of thermo therapy, is feasible and safe. Currently, cryotherapy is most frequently used in patients. New treatment modalities, such as radiofrequency ablation, arc very promising but their true clinical value should be determined in a randomized clinical trial.

Percutaneous tumor ablation with radiofrequency

BACKGROUND

Radiofrequency thermal ablation (RFA) is a new minimally invasive treatment for localized cancer. Minimally invasive surgical options require less resources, time, recovery, and cost, and often offer reduced morbidity and mortality, compared with more invasive methods. To be useful, image-guided, minimally invasive, local treatments will have to meet those expectations without sacrificing efficacy.

METHODS

Image-guided, local cancer treatment relies on the assumption that local disease control may improve survival. Recent developments in ablative techniques are being applied to patients with inoperable, small, or solitary liver tumors, recurrent metachronous hereditary renal cell carcinoma, and neoplasms in the bone, lung, breast, and adrenal gland.

RESULTS

Recent refinements in ablation technology enable large tumor volumes to be treated with image-guided needle placement, either percutaneously, laparoscopically, or with open surgery. Local disease control potentially could result in improved survival, or enhanced operability.

CONCLUSIONS

Consensus indications in oncology are ill-defined, despite widespread proliferation of the technology. A brief review is presented of the current status of image-guided tumor ablation therapy. More rigorous scientific review, long-term follow-up, and randomized prospective trials are needed to help define the role of RFA in oncology.

Non-surgical treatment of hepatocellular carcinoma

Primary hepatocellular cancer is a disease with a poor prognosis for which there is little consensus on treatment and a paucity of comparative trials. The coexistence of cancer with cirrhosis complicates treatment, and also confers a high risk for the development of further tumours. Surgery, either by hepatic resection or orthotopic liver transplantation, is only a feasible option in a minority of patients. This article surveys the non-surgical approaches to the treatment of hepatocellular cancers-local ablation techniques, arterial embolization with and without chemotherapy, conventional chemotherapy and hormonal modulation, and targeted and external irradiation.

MR monitoring of tumour thermal therapy

Thermal therapy of tumour including hyperthermia and thermal ablation by heat or cold delivery requires on line monitoring. Due to its temperature sensitivity, Magnetic Resonance Imaging (MRI) allows thermal mapping at the time of the treatment. The different techniques of MR temperature monitoring based on water proton resonance frequency (PRF), longitudinal relaxation time T1, diffusion coefficient and MR Spectroscopic Imaging (MRSI) are reviewed and debated. The PRF method appears the most widely used and the most efficient at high magnetic field in spite of important drawbacks. The T1 method is the easiest method of visualisation of qualitative temperature distribution and quantitative measurement seems possible in the tissue surrounding the tumour up to a temperature of 45-65 degrees C. Despite its high temperature sensitivity, application of the diffusion method in vivo is restricted due to its high motion sensitivity. The recent MRSI technique seems very promising provided acquisition times can be reduced. Results from the literature indicate that MR temperature monitoring in vivo can be achieved in vivo with a precision of about 3 degrees C in 13 s for a voxel of 16 mm3 (1.5 x 1.5 x 7 mm) in 1.5 T scanners.

Cost-effectiveness of percutaneous radiofrequency ablation for malignant hepatic neoplasms

PURPOSE

Percutaneous radiofrequency (RF) ablation is a promising technique for the treatment of hepatic malignancies. However, its cost-effectiveness has not been established. The purpose of this study is to determine the cost-effectiveness of RF ablation compared to palliative care in the treatment of hepatocellular cancer and colorectal liver metastases. This study also seeks to evaluate the effects of transition from traditional to newly implemented prospective outpatient reimbursement mechanisms on RF ablation cost-effectiveness.

MATERIALS AND METHODS

The marginal direct costs of a percutaneous RF ablation treatment strategy were compared to palliative care over a range of survival benefits with use of a cost-effectiveness model built from the perspective of the payer. Variables used in the model, including complication rates and procedure efficacy, were obtained from the literature and the authors' experience with 46 consecutive patients.

RESULTS

The cost-effectiveness of a standardized percutaneous RF ablation treatment strategy compared to palliative care was $20,424, $11,407, $5,034, and $3,492, respectively, per life-year (LY) gained when marginal median survival conferred by RF ablation is 6 months, 1 year, 3 years, and 5 years. The RF ablation treatment strategy would be required to generate 6.14, 2.26, and 1.10 months of marginal median survival benefit to achieve strict ($20,000/LY gained), moderate ($50,000/LY gained), and generous ($100,000/LY gained) cost-effectiveness thresholds. Cost-effectiveness was sensitive to the number of lifetime treatments, hours of observation time, frequency of follow-up evaluations, cost of abdominal computed tomography, and decision to perform RF ablation as an inpatient or outpatient.

CONCLUSION

Percutaneous RF ablation is a cost-effective treatment strategy compared to palliative care and has likely already achieved the survival benefit required to meet even a strict cost-effectiveness criterion. Dependence on reimbursement mechanism highlights the importance of concordance between policy and RF ablation technology. The results of this study allow flexible application of cost-effectiveness data despite current uncertainties in treatment and survival data and heterogeneity in treatment populations.

Percutaneous ultrasonographically guided radiofrequency heat ablation for treatment of primary hyperparathyroidism in dogs

OBJECTIVE

To evaluate the efficacy and safety of ultrasonographically guided radiofrequency heat ablation of parathyroid masses in dogs with primary hyperparathyroidism.

DESIGN

Clinical trial.

ANIMALS

11 dogs.

PROCEDURE

In all dogs, either 1 or 2 parathyroid masses were evident ultrasonographically. Dogs were anesthetized, and a 20-gauge over-the-needle catheter was directed into the parathyroid mass via ultrasonographic guidance. Radiofrequency heat was applied to the stylet of the catheter until there was sonographically apparent change to the entire parenchyma of the mass. Serum total and ionized calcium and parathyroid hormone concentrations were monitored daily for 5 days after the ablation procedure and again at 1, 2, and 3-month intervals, if possible. Dogs were monitored for adverse effects.

RESULTS

One treatment was required in 6 dogs, 2 treatments were required in 2 dogs, and treatment was unsuccessful in 3 dogs. Serum total and ionized calcium concentrations were within reference ranges within 2 days of the last procedure in all 8 successfully treated dogs. Serum parathyroid hormone concentration was decreased 24 hours after treatment in all 8 dogs. Hypocalcemia developed in 5 of the 8 successfully treated dogs, all of which required treatment. One dog had a transient voice change. Other adverse effects were not reported.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasonographically guided radiofrequency heat ablation of parathyroid masses is a safe and effective alternative to surgery in dogs with primary hyperparathyroidism.

Radiofrequency thermal ablation of a splenic metastasis

Effective local ablation of large tumors with radiofrequency has been made possible by recent advancements. Tumor ablation with radiofrequency has been described mainly in the liver, but also recently in the kidney, adrenal gland, lung, and breast. A rapidly growing splenic metastasis from renal cell carcinoma was effectively treated percutaneously, with US guidance. Focal splenic disease may not be a common indication for ablation; however, further work is necessary to evaluate the safety and efficacy of this procedure in this setting.

Locoregional management of hepatocellular carcinoma. Surgical and ablation therapies

The selection of an appropriate treatment strategy for patients with HCC depends on careful tumor staging and assessment of the underlying liver disease (Fig. 5). All patients with localized HCC (involvement of one single lobe, no vascular invasion or extrahepatic disease) should be evaluated for the potentially curative therapeutic options of partial hepatectomy or OLT. Candidates for partial hepatectomy must have no liver disease or Child's A cirrhosis, normal portal pressure, and normal serum bilirubin. For patients not meeting these criteria, OLT should be considered if there is a solitary lesion smaller than 5 cm in diameter or fewer than three lesions smaller than 3 cm. Local ablative therapies such as PEI, RFA, and TACE offer palliation for patients for whom surgical approaches are contraindicated. Percutaneous alcohol injection and RFA are minimally invasive and can be used on an outpatient basis, usually for tumor nodules smaller than 3 cm. When these therapies are used for small tumors, the survival rates can be similar to those achieved by partial hepatectomy. Transcatheter [figure: see text] arterial chemoembolization may be used as an interim treatment for patients waiting for OLT. Although TACE is often used for the palliation of large tumors, significant survival benefits have not yet been demonstrated for this indication.

Hemobilia, intrahepatic hematoma and acute thrombosis with cavernomatous transformation of the portal vein after percutaneous thermoablation of a liver metastasis

A 53-year-old-man underwent US-guided percutaneous thermal ablation with a cooled-tip needle of three liver metastases from gastric cancer. Six days later, the patient was re-admitted for melena, scleral jaundice, and anemia. Abdominal US disclosed echogenic material in the gallbladder lumen (hemobilia) and a focal lesion with mixed echotexture in segment III (hepatic hematoma). On day 5 portal cavernomatosis was diagnosed at US and confirmed by color Doppler and a helical CT exam. The case described emphasizes that radio-frequency interstitial hyperthermia may cause not only traumatic injury of the liver parenchyma but also thermally mediated damage of vascular structures.

Locoregional treatments for hepatocellular carcinoma

Improvements in diagnostic techniques have enhanced our understanding of the natural history of hepatocellular carcinoma (HCC). This has facilitated a proper evaluation of the available treatment options for this neoplasm through both phase II studies and randomized controlled trials. Surgical resection and liver transplantation constitute the first two radical options, and when they are contra-indicated, patients may benefit from percutaneous ethanol injection or thermal ablation by radiofrequency current. These options may also achieve a complete response and constitute the last potentially radical therapies for small HCC. In contrast, for large multinodular tumours, the available treatment options have not been shown to improve survival. Arterial embolization with or without associated chemotherapy has been widely used. However, randomized controlled trials have failed to show a survival benefit, emphasizing the need to develop new treatment strategies.

Radiofrequency ablation followed by resection of malignant liver tumors

BACKGROUND

Radiofrequency ablation (RFA) has recently been used to treat liver tumors, but few clinical reports have described the pathological characteristics of radiofrequency ablation in human specimens. This study delineates the gross pathologic and histochemical changes induced by RFA in benign and malignant human liver tissue and confirms the tumor necrosis described in early clinical reports.

METHODS

Ten patients with metastatic tumors of the liver received a single treatment of ultrasound-guided percutaneous RFA to 12 tumors. Hepatic resection was carried out within 6 weeks of RFA. Specimens were stained with standard hematoxylin and eosin stain followed by oxidative stain to determine if there was evidence of viable tumor within the zone of ablation.

RESULTS

Nine of the 12 ablations were resected. Microscopic examination within the zone of ablation showed successful ablation in 8 of the 9 resected ablations.

CONCLUSIONS

Percutaneous RFA creates well-circumscribed areas of tumor necrosis with apparent cell death using an oxidative stain. Further investigation is encouraged to determine the clinical effectiveness of radiofrequency ablation in the complete destruction of liver tumors for palliative or curative intent.