Assessment of renal cell carcinoma after cryoablation using contrast-enhanced gray-scale ultrasound

Contrast-enhanced ultrasound (CEUS): an excellent tool in the follow-up of small renal masses treated with cryoablation

Strict imaging follow-up is mandatory after cryoablation of small renal masses (SRMs). Although it uses ionizing radiation and nephrotoxic iodinated contrast, computed tomography (CT) is still the gold standard test. Contrast-enhanced ultrasound (CEUS) is a novel technique that informs in real time about renal perfusion avoiding radiation and nephrotoxicity. The objective of this study is to compare outcomes between CEUS and CT in the follow-up of SRMs treated with cryoablation, as well as to assess degree of agreement between them. This is a prospective observational study (May 2012 to December 2013) comparing CEUS and CT in 16 patients with SRMs cryoablated. The on-going protocol of the study includes a CT and CEUS 3 months after treatment and then every 6 months during 5 years. Local relapse was defined as the presence of contrast enhancement in the mass. All the CEUS were performed by a single experienced observer (E.S.). Degree of agreement was measured with kappa index. CEUS detected contrast enhancement in three patients (3/16, 18.8%) and CT in two patients (2/16, 12.5%). Degree of agreement between CEUS and CT, according to Landis-Koch classification, was 0.76 (CI 0.33-1.19; p = 0.0165), which is excellent and higher than expected by random. Sensitivity of the test is 93.75% (15/16). Median time of follow-up after cryoablation is 22 months (15.5-36.5). CEUS has an excellent agreement with CT and a high sensitivity in the follow-up of SRMs treated with cryosurgery, demonstrating its usefulness. Due to these encouraging results, it could become a reference test in the near future for monitoring SRMs after ablative treatment.

Contrast-Enhanced Subharmonic and Harmonic Ultrasound of Renal Masses Undergoing Percutaneous Cryoablation

RATIONALE AND OBJECTIVES

The objective of this study was to evaluate and compare contrast-enhanced subharmonic and harmonic ultrasound as tools for characterizing solid renal masses and monitoring their response to cryoablation therapy.

MATERIALS AND METHODS

Sixteen patients undergoing percutaneous ablation of a renal mass provided informed consent to undergo ultrasound examinations the morning before and approximately 4 months after cryoablation. Ultrasound contrast parameters during pretreatment imaging were compared to biopsy results obtained during ablation (n = 13). Posttreatment changes were evaluated by a radiologist and compared to contrast-enhanced magnetic resonance imaging (MRI)/computed tomography (CT) follow-up.

RESULTS

All masses initially showed heterogeneous enhancement with both subharmonic and harmonic ultrasound. Early contrast washout in the mass relative to the cortex was observed in 6 of 9 malignant and 0 of 4 benign lesions in subharmonic mode and 8 of 9 malignant and 1 of 4 benign lesions in harmonic imaging. In cases where the lesion was adequately visualized at follow-up (n = 12), subharmonic and harmonic ultrasound showed accuracies of 83% and 75%, respectively, in predicting treatment outcome. Although harmonic imaging showed less overall error, no significant differences (P > .29) in ablation cavity volumes were observed between MRI/CT and either contrast-imaging mode.

CONCLUSIONS

Subharmonic and harmonic contrast-enhanced ultrasound may be a safe and accurate imaging alternative for characterizing renal masses and evaluating their response to cryoablation therapy. Although subharmonic imaging was more accurate in detecting effective cryoablation, harmonic imaging was superior in quantifying ablation cavity volumes.

Improved outcome of percutaneous radiofrequency ablation in renal cell carcinoma: a retrospective study of intraoperative contrast-enhanced ultrasonography in 73 patients

OBJECTIVES

To evaluate the impact of contrast-enhanced ultrasonography (CEUS) during percutaneous radiofrequency ablation (PRFA) procedure in renal cell carcinoma (RCC).

METHODS

From January 2008 to July 2010, 73 patients with sporadic unilateral RCC were enrolled to our study (57 men and 16 women, age range: 37-78 years, mean age 57.9 years). The diameter of the tumor was 1.7-5.8, 3.4 cm on average. The patients were divided into two groups depending on the intraoperative ultrasonography type: CEUS group and conventional ultrasound group. Patients in CEUS group received CEUS before insertion of the electrode, and the second CEUS was performed right after the initial ablation to dynamically evaluate the images. If there was highly suspicious residue, additional ablation and repeated CEUS were applied. Patients in the conventional ultrasound group received PRFA guided by gray-scale ultrasound. All of these patients received contrast-enhanced computed tomography (CT) examination 7 days after the procedure (patients in CEUS group received CEUS conducted with each CT scan), with subsequent CT and CEUS assessment at 3, 6, and every 6 months thereafter.

RESULTS

The mean follow-up period was 22 months (range: 12-42 months). All tumors were biopsied before RFA. The local tumor control rate was 94.6% (35/37) in the CEUS group and 86.1% (31/36) in the conventional ultrasound group (P < 0.05); the cancer-specific survival rate and the overall survival rate were 100%. The post-RFA (12 months) mean GFR levels were 84.7 ± 27.5 mL/min/1.73 m(2) (P > 0.05, compared with pre-GFR: 86.4 ± 26.2 mL/min/1.73 m(2)) in the CEUS group and 81.9 ± 22.8 mL/min/1.73 m(2) (P > 0.05, compared with pre-GFR: 83.5 ± 23.7 mL/min/1.73 m(2)) in the conventional ultrasound group.

CONCLUSION

Intraoperative CEUS can "real-time" monitor the ablated area during PRFA procedure. This technique can help to achieve a higher success rate compared with conventional ultrasound. No impact of intraoperative CEUS has been found on GFR level.

Ultrasound imaging and contrast agents: A safe alternative to MRI?

Microbubble contrast media are used to enhance ultrasound images. Because ultrasound is a real-time investigation, contrast-enhanced ultrasound offers possibilities for perfusion imaging. This review is conducted to evaluate the safety of contrast-enhanced ultrasound and its possible role in medical imaging. The safety of diagnostic ultrasound is still an important field of research. The wanted and unwanted effects of ultrasound and microbubble contrast media as well as the effects of ultrasound on these microbubbles are described. Furthermore, some of the possible applications and indications of contrast-enhanced ultrasound will be discussed. The shared advantages of MRI and ultrasound are the use of non-ionizing radiation and non-nephrotoxic contrast media. From this review it can be concluded that, for certain indications, contrast enhanced ultrasound could be a safe alternative to MRI and a valuable addition to medical imaging.

Follow-up after percutaneous radiofrequency ablation of renal cell carcinoma: contrast-enhanced sonography versus contrast-enhanced CT or MRI

OBJECTIVE

The purpose of this study was to assess, with contrast-enhanced CT or MRI as the reference imaging technique, the diagnostic performance of low-mechanical-index contrast-enhanced sonography in detecting local tumor progression after percutaneous radiofrequency ablation of renal tumors.

MATERIALS AND METHODS

Twenty-nine patients with 30 renal tumors (18 men, 11 women; mean age, 73 years; range, 53-83 years) underwent percutaneous radiofrequency ablation at a single center between March 1998 and January 2007. The imaging follow-up schedule was both contrast-enhanced sonography and CT or MRI 4 months after completion of treatment and every 4 months for the first year. Thereafter, the follow-up schedule was contrast-enhanced sonography every 4 months with CT or MRI every 8 months. The chi-square test with Yates correction was used to evaluate positive and negative predictive values and accuracy.

RESULTS

One patient was scheduled to undergo surgical resection, and another patient was lost to follow-up. Twenty-seven patients with 28 renal tumors participated in follow-up. The concordance between contrast-enhanced sonographic and CT or MRI findings was 100% for 27 of 28 tumors (96.4%) that had a hypervascular pattern before treatment. In the case of the tumor that was hypovascular at imaging performed before percutaneous radiofrequency ablation, local tumor progression was missed at contrast-enhanced sonography. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of contrast-enhanced sonography were 96.6%, 100%, 100%, 95.8%, and 98.1%.

CONCLUSION

Contrast-enhanced sonography is an effective alternative to CT and MRI in the follow-up of renal tumors managed with percutaneous radiofrequency ablation.

Feasibility study on using an infrared thermometer for evaluation and administration of cryosurgery

Successful performance of cryosurgery relies heavily on a quick, efficient, safe and economic imaging way to monitor the surgical advancement and then to evaluate the curative effect. However, there is currently a lack of such an imaging modality. As for the commonly adopted imaging devices such as X-CT, MRI and PET, in addition their high cost and complexity in operation, they often induce additional scathe to the patients due to their potential radiation effects. Besides, in cryosurgery, the most important parameter - temperature - can not be directly detected by these methods. Considering the above factors, infrared thermography (IRT), a rather useful yet often neglected functional imaging technique in clinics, is proposed in this paper as an efficient tool for the quick evaluation and administration of a cryosurgical treatment of tumors. Based on skin surface temperature mapping, the degree of damage to the target tissue site caused by different freezing/heating protocols, as well as the states of blood circulation and metabolic heat generation within the treated region can possibly be identified. Further, through recording the temperature variation feature at the skin surface before and after cryosurgery, IRT would help to quickly evaluate the curative effect, which is very beneficial for later treatment planning. By detecting the surface infrared image and analyzing its digital values, the patient's invisible focus and abnormal physiological states, e.g. inflammations or pneumothorax, often accompanied by cryosurgical output yet difficult to determine via conventional imaging, could also possibly be diagnosed. To test the above concepts, both typical animal and clinical experiments were performed to demonstrate the feasibility and advantages of IRT-guided cryosurgery. This study may help push forward a novel, low-cost and non-contact way for an efficient performance of cryosurgery.

Contrast-enhanced ultrasonography in the follow-up of cryoablation of renal tumours: a feasibility study

OBJECTIVE

To determine whether evaluating perfusion patterns with contrast-enhanced ultrasonography using contrast-pulse sequence imaging (CPS; a new imaging method that enables selective visualization of perfusion) is possible at different times after cryoablation of renal tumours, and to describe the characteristics of CPS in a small group of patients.

PATIENTS AND METHODS

The efficacy of renal cryoablation is mainly judged using imaging. Seven randomly selected patients, each at a different time after laparoscopically assisted cryoablation of a renal tumour, were investigated with CPS and a microbubble-contrast agent. The perfusion characteristics in the lesions were scored by two investigators and described, and the lesions were measured.

RESULTS

In the seven patients treated with cryoablation for small renal tumours, eight CPS studies were performed. Five lesions showed no enhancement and one lesion, investigated 18 months after treatment was not recognized. In one patient, no enhancement was seen after 1 month but 7 months later, there were minimal contrast signals inside the treated area. The lesions could be measured with a mean standard deviation of 1.1 mm and a mean difference between the two investigators of 0.7 mm.

CONCLUSION

Our first experiences with CPS imaging for the follow-up of renal cryoablation show that this technique can be used to characterize perfusion defects at different times after cryoablation.

Contemporary imaging modalities for the surveillance of patients with renal cell carcinoma

In recent years, there have been multiple advances in imaging technologies that have improved the surveillance for recurrence of neoplasms. Multidetector row CT and dynamic contrast enhanced MRI now provide excellent anatomic detail and are beginning to show functional detail as the rapid capture of images following contrast administration improves. Positron emission tomography is emerging as a useful tool in evaluating patients with suspected metastatic disease to the abdomen and bone, particularly when combined with CT. The role of ultrasound in the surveillance of renal cell carcinoma is yet unclear, but its role may be expanding with use of newly developed contrast drugs. Herein we review the relevance of these modalities to the follow-up of patients with renal cell carcinoma.

Imaging Associated with Percutaneous and Intraoperative Management of Renal Tumors

As new minimally invasive treatment options for small renal tumors such as laparoscopic partial nephrectomy (LPN), radiofrequency ablation (RFA), and cryoablation(CA) have been developed, the reliance upon imaging technologies, both intraoperatively and postoperatively, has expanded greatly. CT, MRI, and ultrasonography (US)have proven themselves extremely useful in this regard, but their utility requires a thorough understanding of each modality's limitations, proper intraoperative use, and expected postoperative findings. This article discusses intraoperative use of US for LPN,RFA, and CA. The expected postoperative MRI and CT findings after CA and RFA also are covered, highlighting the different radiographic evolutionary patterns encountered after use of these technologies. Because the success of these new treatments for small re-nal tumors (especially RFA and CA) depends not only on the technology itself but also on the advantages and limitations of the associated radiographic techniques, urologists of the 21st century must be facile at interpreting and manipulating these imaging modalities to appropriately care for their renal tumor patients.