Doppler signals observed during high temperature thermal ablation are the result of boiling

A clinical study of thermal monitoring techniques of ultrasound-guided microwave ablation for hepatocellular carcinoma in high-risk locations

To confirm the safety and effectiveness of the minimally invasive thermal monitor technique on percutaneous ultrasound-guided microwave ablation (MWA) for hepatocellular carcinoma (HCC) in high-risk locations, a total of 189 patients with 226 HCC nodules in high-risk locations were treated with MWA. The real-time temperature of the tissue between the lesion margin and the vital structures was monitored by inserting a 21G thermal monitoring needle. The major indexes of technical success, technique effectiveness, local tumour progression and complications were observed during the follow-up period. Technical success was acquired in all patients. Technique effectiveness was achieved with one session in 119 lesions based on contrast-enhanced ultrasound (CEUS) 3-5 days after treatment. An additional 95 lesions achieved technique effectiveness at the second session. Within the follow-up period of 6-58 months (median 38 months), the 1-, 2-, 3-, and 4-year local tumour progression rate was 11.1%, 18.1%, 19.1%, and 19.9%, respectively. There were no major complications in all the patients except for the common side effects. These results indicate that the thermal monitor technique can be applied to prevent major complications in vulnerable structures and allow percutaneous MWA to achieve satisfactory technique effectiveness in the treatment of HCC in high-risk locations.

Dependence of ultrasound echo decorrelation on local tissue temperature during ex vivo radiofrequency ablation

This study investigates echo decorrelation imaging, an ultrasound method for thermal ablation monitoring. The effect of tissue temperature on the mapped echo decorrelation parameter was assessed in radiofrequency ablation experiments performed on ex vivo bovine liver tissue. Echo decorrelation maps were compared with corresponding tissue temperatures simulated using the finite element method. For both echo decorrelation imaging and integrated backscatter imaging, the mapped tissue parameters correlated significantly but weakly with local tissue temperature. Receiver operating characteristic (ROC) curves were used to assess the ability of echo decorrelation and integrated backscatter to predict tissue temperature greater than 40, 60, and 80 °C. Significantly higher area under the ROC curve (AUROC) values were obtained for prediction of tissue temperatures greater than 40, 60, and 80 °C using echo decorrelation imaging (AUROC = 0.871, 0.948 and 0.966) compared to integrated backscatter imaging (AUROC = 0.865, 0.877 and 0.832).

Analysis of tissue changes, measurement system effects, and motion artifacts in echo decorrelation imaging

Echo decorrelation imaging, a method for mapping ablation-induced ultrasound echo changes, is analyzed. Local echo decorrelation is shown to approximate the decoherence spectrum of tissue reflectivity. Effects of the ultrasound measurement system, echo signal windowing, electronic noise, and tissue motion on echo decorrelation images are determined theoretically, leading to a method for reduction of motion and noise artifacts. Theoretical analysis is validated by simulations and experiments. Simulated decoherence of the scattering medium was recovered with root-mean-square error less than 10% with accuracy dependent on the correlation window size. Motion-induced decorrelation measured in an ex vivo pubovisceral muscle model showed similar trends to theoretical motion-induced decorrelation for a 2.1 MHz curvilinear array with decorrelation approaching unity for 3-4 mm elevational displacement or 1-1.6 mm range displacement. For in vivo imaging of porcine liver by a 7 MHz linear array, theoretical decorrelation computed using image-based motion estimates correlated significantly with measured decorrelation (r = 0.931, N = 10). Echo decorrelation artifacts incurred during in vivo radiofrequency ablation in the same porcine liver were effectively compensated based on the theoretical echo decorrelation model and measured pre-treatment decorrelation. These results demonstrate the potential of echo decorrelation imaging for quantification of heat-induced changes to the scattering tissue medium during thermal ablation.

Radiofrequency ablation and breast cancer: a review

BACKGROUND

Radiofrequency ablation (RFA) use in breast cancer is a developing area of research. There have been a number of published studies over the last decade, which explores the feasibility of minimally invasive techniques in breast cancer treatment. In this review, we will discuss the most recent data on radiofrequency ablation and examine the current methods, outcomes, complications, and limitations of RFA in breast cancer therapy.

METHODS

Pub Med search for English Language articles on RFA in breast cancer.

RESULTS

More than 25 studies were reviewed and we searched for number of tumors, average size, electrode used, if they successfully ablated the tumor, when the tumor was then resected and if the patients experienced any complication from the ablation.

CONCLUSIONS

Radiofrequency ablation is an emerging minimally invasive therapy in small, localized breast cancer. Currently, no clinical trials have been published to directly compare RFA to the current standard of surgical resection. Ultimately, RFA will need clinical trials to evaluate oncologic outcomes involving long interval follow-up to determine survival, local control and disease progression before it becomes a reasonable alternative to surgical resection.

Radiofrequency ablation after breast lumpectomy added to extend intraoperative margins in the treatment of breast cancer (ABLATE): a single-institution experience

BACKGROUND

Breast-conserving surgery is often preferred to treat early-stage breast cancer. This method aims to minimize repeat excision and local recurrence rates. The ABLATE Registry expands this to multiple centers with a total accrual goal of 250. This video illustrates an intraoperative radiofrequency ablation (RFA) technique.

METHODS

Sixteen women with a mean age of 65 years underwent RFA after lumpectomy. The RFA probe was deployed 1 cm circumferentially in the cavity and maintained at 100°C for 15 min. The ablation zone was monitored with color-flow ultrasound. Patients returned 2 weeks later to complete the Subjective Cosmetic Scale and the European Organisation for Research and Treatment of Cancer Body Image Scale.

RESULTS

At a mean follow-up of 3.9 months, there were no local recurrences. Two-week cosmesis scores were excellent (n = 9) or good (n = 5).

CONCLUSIONS

Our initial experience is encouraging. Continued national accrual will permit evaluation of reduction in repeat excision and local recurrence rate, as well as potentially reduce requirements for adjuvant radiation.

Feasibility of percutaneous excision followed by ablation for local control in breast cancer

PURPOSE

Percutaneous ablation of breast cancer has shown promise as a treatment alternative to open lumpectomy. We hypothesized that percutaneous removal of breast cancer followed by percutaneous ablation to sterilize and widen the margins would not only provide fresh naive tissue for tumor marker and research investigation, but also better achieve negative margins after ablation.

METHODS

Patients diagnosed by percutaneous biopsy (ultrasound or stereotactic-guided) with breast cancer ≤1.5 cm, >1 cm from the skin, and ≤1 cm residual disease and no multicentric disease by magnetic resonance imaging were accrued to this institutional review board-approved study. Patients were randomized to laser versus radiofrequency ablation. The ultrasound-guided ablation was performed in the operating room and followed by immediate excision, whole-mount pathology with proliferating cell nuclear antigen staining, and reconstruction.

RESULTS

Twenty-one patients were enrolled onto the study. Fifteen patients received radiofrequency ablation, and all showed 100% ablation and negative margins. Magnetic resonance imaging was helpful in excluding multicentric disease but less so in predicting presence or absence of residual disease. Seven of these patients showed no residual tumor and eight showed residual dead tumor (0.5 ± 0.7 cm, range 0.1-2.5 cm) at the biopsy site with clear margins. The laser arm (3 patients) pathology demonstrated unpredictability of the ablation zone and residual live tumor.

CONCLUSIONS

This pilot study demonstrates the feasibility of a novel approach to minimally invasive therapy: percutaneous excision and effective cytoreduction, followed by radiofrequency ablation of margins for the treatment of breast cancer. Laser treatment requires further improvement.