Image-Guided Percutaneous Cryoablation of Renal Tumors

Dynamic path planning for percutaneous procedures in the abdomen during free breathing

PURPOSE

Percutaneous procedures are increasingly used for the treatment of tumors in abdominal structures. Most of the time, these procedures are planned based on static preoperative images and do not take into account any motions, while breathing control is not always applicable. In this paper, we present a method to automatically adjust the planned path in real time according to the breathing.

METHODS

First, an estimation of the organs motions during breathing is performed during an observation phase. Then we propose an approach named Real Time Intelligent Trajectory (RTIT) that consists in finding the most appropriate moments to push the needle along the initially planned path, based on the motions and the distance to surrounding organs. We also propose a second approach called Real Time Straight Trajectory (RTST) that examines sixteen scenarios of needle insertion at constant speed, starting at eight different moments of the breathing cycle with two different speeds.

RESULTS

We evaluated our methods on six 3D models of abdominal structures built using image datasets and a real-time simulation of breathing movements. We measured the deviation from the initial path, the target positioning error, and the distance of the actual path to risky structures. The path proposed by RTIT approach is compared to the best path proposed by RTST.

CONCLUSIONS

We show that the RTIT approach is relevant and adapted to breathing movements. The modification of the path remains minimal while collisions with obstacles are avoided. This study on simulations constitutes a first step towards intelligent robotic insertion under real-time image guidance.

[Ablative therapy in urology: Good practice and perspective]

INTRODUCTION

To expose the main point of discussion from present ablative therapies' guidelines and propose global perspectives.

MATERIALS AND METHODS

A review of the scientific literature was performed in Medline database (http://www.ncbi.nlm.nih.gov) and Embase (http://www.embase.com/) using different associations of keywords "ablative therapy" ; "prostate cancer"; "kidney cancer"; "guidelines"; "hybrid operating room". Publications obtained were selected based on methodology, language and relevance.

RESULTS

Present guidelines on ablative therapies in urology are, considering authors and organs, either particularly prudent (EAU guidelines for prostate and kidney) or relatively optimistic (CIRSE guidelines). This discrepancy is related to a low level of proof. So, a new approach is mandatory: more homogeneous in methodology, and especially more open to a new organization sparing economic efficiency. The objective will be to get multifunctional and multidisciplinaries platforms, in facts and in minds. It will induce, in the future, a deep reflection about training and boundaries' specialties.

CONCLUSION

Ablative therapies represent a crucial stake for urology and a clear example of medicosurgical evolution in future, based on new technologies (energy, robotic, imaging). A serious and deep reflection is necessary to prepare it and be deeply involved in.

Pneumodissection for skin protection in image-guided cryoablation of superficial musculoskeletal tumours

PURPOSE

Pneumodissection is described as a simple method for preventing skin injury during cryoablation of superficial musculoskeletal tumours.

METHODS

Superficial tumour cryoablations performed from 2009 to 2015 were retrospectively reviewed. Pneumodissection was performed in 13 patients when the shortest tumour-skin distance was less than 25 mm. Indications were pain palliation (n = 9) and local tumour control (n = 4). Patients, target tumours, technical characteristics and complications up to 60 days post ablation were reviewed. The ice ball-skin distances with and without pneumodissection were compared by a paired t-test and further assessed for association with covariates using ANCOVA.

RESULTS

Technical success for ablation was 12 of 13. The mean shortest tumour-skin distance was 15.0 mm (3.2-24.5 mm). The mean thickness of pneumodissection was 9.6 mm (5.2-16.6 mm) resulting in mean elevation of skin of 3.4 mm (1.2-5.3 mm). Mean shortest ice ball-skin distance after pneumodissection was 10.5 mm (4.2-19.7 mm). No infection or systemic air embolism was noted. No intraprocedural frostbite was observed.

CONCLUSION

Pneumodissection is feasible, effective and safe in protecting the skin during image-guided cryoablation of superficial tumours.

KEY POINTS

• Frostbite during image-guided cryoablation of superficial tumours is commonly under-reported. • Frostbites are painful and may introduce infection into the superficial ablation zone. • Warm compress, saline and CO ₂ have shortcomings in protecting the skin. • Pneumodissection is free, readily available, easy to use and safe and effective.

Interventional oncology: pictorial review of post-ablation imaging of liver and renal tumors

Percutaneous image-guided ablation is now commonly performed in many institutions for the treatment of hepatocellular carcinoma, liver metastases, and renal cell carcinoma in select patients. Accurate interpretation of post-ablation imaging is of supreme importance because treatment algorithms for these diseases rely heavily on imaging to guide management decisions. The purpose of this pictorial essay is to provide abdominal imagers with a review of the indications for percutaneous ablation in the abdomen, a basic overview of ablation modalities in clinical use today, the expected post-ablation imaging findings in the liver and kidney, and potential complications of hepatic and renal ablation procedures.

Thermal Ablation of Renal Tumors: Indications, Techniques and Results

BACKGROUND

About 15,000 persons receive the diagnosis of kidney cancer in Germany every year. Surgical resection is the standard treatment for locally confined tumors, but minimally invasive thermoablative techniques are increasingly being used as well.

METHODS

This article is based on publications retrieved by a selective literature search in PubMed regarding the thermoablative techniques now used in clinical practice, with particular attention to radiofrequency ablation (RFA) and cryoablation (CA).

RESULTS

RFA and CA are suitable for patients who cannot undergo surgery because of comorbid illnesses or who have contralateral recurrences or a hereditary precancerous condition. The primary technical success rate of these procedures ranges from 88% to 100%. More than 95% of tumors under 3 cm in diameter can be completely ablated. Reported complication rates range from 1% to 7%. New data on long-term outcomes reveal metastasis-free survival rates of 88% to 99% five years after ablation. A major advantage of these procedures is that thermoablation does not impair renal function to any relevant extent and is thus a good option for patients with limited renal function or a single kidney.

CONCLUSION

The thermoablative techniques are an important addition to the armamentarium of effective treatments for locally confined renal tumors. The guidelines of the American and European urological societies now list thermoablation with RFA or CA as an option for the treatment of small renal tumors with curative intent. Thermoablation of renal tumors has not yet been studied in randomized controlled trials; these will be needed so that the efficacy of tumor control, survival rates, complication rates, and quality of life after treatment can be reliably evaluated to provide definitive confirmation of the value of interstitial techniques.

An overview of image-guided percutaneous ablation of renal tumors

Although nephron-sparing surgery remains the gold standard treatment for small renal tumors, minimally invasive image-guided percutaneous ablation is becoming a viable alternative to operative resection. Percutaneous radiofrequency ablation (RFA) and cryoablation show high technical success rates, a relatively low incidence of residual or recurrent tumor, and competitive rates of patient survival. In this review, an overview of the current status of image-guided percutaneous ablation of renal tumors is presented, with a focus on procedure indications and patient selection, technical aspects of ablation procedures, and treatment outcomes and patient follow-up.

Potent induction of tumor immunity by combining tumor cryoablation with anti-CTLA-4 therapy

Thermal ablation to destroy tumor tissue may help activate tumor-specific T cells by elevating the presentation of tumor antigens to the immune system. However, the antitumor activity of these T cells may be restrained by their expression of the inhibitory T-cell coreceptor CTLA-4, the target of the recently U.S. Food and Drug Administration-approved antibody drug ipilumimab. By relieving this restraint, CTLA-4-blocking antibodies such as ipilumimab can promote tumor rejection, but the full scope of their most suitable applications has yet to be fully determined. In this study, we offer a preclinical proof-of-concept in the TRAMP C2 mouse model of prostate cancer that CTLA-4 blockade cooperates with cryoablation of a primary tumor to prevent the outgrowth of secondary tumors seeded by challenge at a distant site. Although growth of secondary tumors was unaffected by cryoablation alone, the combination treatment was sufficient to slow growth or trigger rejection. In addition, secondary tumors were highly infiltrated by CD4(+) T cells and CD8(+) T cells, and there was a significant increase in the ratio of intratumoral T effector cells to CD4(+)FoxP3(+) T regulatory cells, compared with monotherapy. These findings documented for the first time an effect of this immunotherapeutic intervention on the intratumoral accumulation and systemic expansion of CD8(+) T cells specific for the TRAMP C2-specific antigen SPAS-1. Although cryoablation is currently used to treat a targeted tumor nodule, our results suggest that combination therapy with CTLA-4 blockade will augment antitumor immunity and rejection of tumor metastases in this setting.

US findings after irreversible electroporation ablation: radiologic-pathologic correlation

PURPOSE

To characterize ultrasonographic (US) findings after irreversible electroporation (IRE) to determine the utility of these findings in the accurate assessment of ablation margins.

MATERIALS AND METHODS

The institutional animal care and use committee approved the study. IRE ablation (n = 58) was performed in vivo in 16 pig livers by using two 18-gauge electroporation electrodes with 2-cm tip exposure, 1.5- or 2.0-cm interelectrode spacing, and an electroporation generator. Energy deposition was applied at 2250-3000 V (pulse length, 50-100 μsec; pulse repetition, 50-100). Ablations were performed under US guidance. Images were obtained during ablation and at defined intervals from 1 minute to 2 hours after the procedure. Zones of ablation were determined at gross and histopathologic examination of samples obtained from animals sacrificed 2-3 hours after IRE. Dimensions of the histologic necrosis zone and US findings were compared and subjected to statistical analysis, including a Student t test and multiple linear regression.

RESULTS

Within 20-50 pulse repetitions of IRE energy, the ablation zone appeared as a hypoechoic area with well-demarcated margins. During the next 8-15 minutes, this zone decreased in size from 3.4 cm ± 0.5 to 2.5 cm ± 0.4 and became progressively more isoechoic. Subsequently, a peripheral hyperechoic rim measuring 2-7 mm (mean, 4 mm ± 1) surrounding the isoechoic zone developed 25-90 minutes (mean, 41 minutes ± 19) after IRE. The final length of the treatment zone, including the rim, increased to 3.3 cm ± 0.6. The final dimensions of the outer margin of this rim provided greatest accuracy (1.7 mm ± 0.2) and tightest correlation (r(2) = 0.89) with gross pathologic findings. Histologic examination demonstrated widened sinusoidal spaces that progressively filled with spatially distributed hemorrhagic infiltrate on a bed of hepatocytes with pyknotic nuclei throughout the treatment zone.

CONCLUSION

US findings in the acute period after IRE are dynamic and evolve. The ablation zone can be best predicted by measuring the external hyperechoic rim that forms 90-120 minutes after ablation. This rim is possibly attributable to evolving hemorrhagic infiltration via widened sinusoids.

Percutaneous ablation in the kidney

Percutaneous ablation in the kidney is now performed as a standard therapeutic nephron-sparing option in patients who are poor candidates for resection. Its increasing use has been largely prompted by the rising incidental detection of renal cell carcinomas with cross-sectional imaging and the need to preserve renal function in patients with comorbid conditions, multiple renal cell carcinomas, and/or heritable renal cancer syndromes. Clinical studies to date indicate that radiofrequency ablation and cryoablation are effective therapies with acceptable short- to intermediate-term outcomes and with a low risk in the appropriate setting, with attention to pre-, peri-, and postprocedural detail. The results following percutaneous radiofrequency ablation and cryoablation in the treatment of renal cell carcinoma are reviewed in this article, including those of several larger scale studies of ablation of T1a tumors. Clinical and technical considerations unique to ablation in the kidney are presented, and potential complications are discussed.

Percutaneous cryoablation of renal tumors: patient selection, technique, and postprocedural imaging

Percutaneous cryoablation of renal tumors requires a number of important steps for success and relies heavily on imaging for treatment planning, intraprocedural guidance and monitoring, detection of untreated tumor, and surveillance for disease progression. Imaging-guided percutaneous cryoablation has several advantages over laparoscopic cryoablation. In particular, computed tomography (CT) and magnetic resonance (MR) imaging allow global evaluation of the ablation zone and an accurate depiction of the treatment margin. Ultrasonography allows real-time guidance of probe placement but cannot help depict ice ball formation as accurately as CT or MR imaging. Multiphasic CT or MR imaging should be performed at structured intervals following ablation. Treated tumors are expected to decrease in size over time, and lesion growth and internal or nodular enhancement are suspicious for tumor recurrence or progression. Complications include probe site pain, hematoma, incomplete ablation, and recurrent tumor. Current limitations of percutaneous cryoablation include the inability to control hemorrhage without intraarterial access and a lack of long-term follow-up data. Nevertheless, percutaneous cryoablation is an effective choice for minimally invasive nephron-sparing treatment of renal tumors.

A simple technique for interventional tool placement combining fluoroscopy with interventional computed tomography on a C-arm system

BACKGROUND

Flat-panel cone-beam computed tomography (FP-CBCT) has recently been introduced as a clinical feature in neuroangiography radiographic C-arm systems.

OBJECTIVE

To introduce a method of positioning a surgical tool such as a needle or ablation probe within a target specified by intraoperative FP-CBCT scanning.

METHODS

Two human cadaver and 2 porcine cadaver heads were injected with a mixture of silicone and contrast agent to simulate a contrast-enhanced tumor. Preoperative imaging was performed using a standard 1.5-T magnetic resonance imaging scanner. Intraoperative imaging was used to define the needle trajectory on a GE Innova 4100 flat panel-based neuroangiography C-arm system.

RESULTS

Using a combination of FP-CBCT and fluoroscopy, a needle was successfully positioned within each of the simulated contrast-enhanced tumors, as verified by subsequent FP-CBCT scans.

CONCLUSIONS

This proof-of-concept study demonstrates the potential utility of combining FP-CBCT scanning with fluoroscopy to position surgical tools when stereotactic devices and image-guided surgery systems are not available. However, further work is required to fully characterize the precision and accuracy of the method in a variety of realistic surgical sites.