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1) Understand and compare treatment alternatives for small renal masses. 2) Recognize imaging features of small renal masses that impact treatment alternatives. 3) Understand the risks and benefits of image guided renal mass ablation.

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To assess the utility of apparent diffusion coefficient (ADC) in predicting and evaluating the response of the radiofrequency ablated renal cell carcinoma.

30 patients with 41 pathological confirmed renal cell carcinomas underwent MRI at 1.5T including diffusion weighted images before and after radiofrequency ablation. The ADC values of the tumor at b= 0, 100 and 600 s/mm2 were noted by drawing multiple regions of interest. Imaging features, histologic subtypes and Fuhrman grade of the tumor was also recorded. The participants were divided into 2 groups: complete treatment group (n=38) and residual disease group (n=3) based on follow up imaging and clinical notes. The variables were statistically analyzed.

Of 41 RCCs, 23.3% were papillary, 57% were clear cell and 3% chromophobe types. The mean pre-treatment tumor ADC value in the complete treatment group was 1.779 s/mm2 and pre-treatment ADC value of residual disease group was 1.609 s/mm2 (p=0.512). Given the substantial overlap, it was not possible to use the pre-ablation ADC value as a predictor of residual disease. Fuhrman grade showed significant correlation (p=0.005) with the post RF ablation response with 100% response rate in Fuhrman grade 1. For grade 2 this rate was 83.3% and for grade 3, it was 0%. There was no significant difference between ADC value of pre- and post radiofrequency ablated renal cell carcinoma. Though mean ADC values for the group before and after ablation did not differ, some cases showed increase in ADC and others showed decrease. The range in changes was -0.350 to 1.560.

ADC values in individual cases may increase or decrease after ablation limiting use of this marker in evaluating for viable tumor. Pre-ablation ADC did not predict outcome of ablation. Further studies are required to establish a cut of ADC value to distinguish complete responders from residual disease.

ADC values in renal tumors do not appear useful in predicting outcome or in assessing residual tumor after ablation.

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1) Understand the different approaches and techniques of thorough renal mass cryoablation that produces very low recurrence rates, even for larger central tumors. 2) Understand the appropriate settings to utilize protective techniques (i.e., hydrodissection, balloon interposition, ureteral stent, etc..) for adjacent calyces, bowel and ureter to avoid complications. 3) Identify major imaging follow-up criteria for ablation success and any early failures. 4) Describe the overall cost-efficacy trade-offs for cryo vs. heat-based renal ablations vs. partial nephrectomy, in relation to tumor location, complications and recurrence rates.

Cryoablation of smaller renal cancers (i.e., T1a, or <4 cm) is an out-patient treatment that is safe, effective and flexibility for nearly any renal location. Major cryoablation benefits include its excellent visualization of ablation zone extent, low procedure pain and flexible protection of tumor ablation sites near calyces, bowel and ureter. CT-guidance is the cryoablation guidance modality of choice due to circumferential visualization of low density ice and ready availability. US-guidance can augment renal cryoablation, especially for smaller visible masses and/or placement of interstitial metallic markers during biopsy for selected cases requiring better eventual CT localization. MR-guidance has little clinical benefit or cost-efficacy. For safety, cases will be considered for avoidance of direct calyceal puncture, selection of hydrodissection or balloon interposition for bowel protection, and protection of the uretero-pelvic junction by stent placement. Imaging outcomes of complications and their avoidance will be shown. For optimal efficacy, tumor size in relation to number and size of cryoprobes emphasize the "1-2 Rule" of at least 1 cryoprobe per cm of tumor diameter and no further than 1 cm from tumor margin, as well as cryoprobe spacing of <2cm. Thorough extent of visible cryoablation margins beyond all apparent tumor margins produces very low local recurrence rates for tumors in nearly any renal location, resulting in excellent cost-efficacy by minimizing the need for re-treatments.

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A statistical model was investigated to quantify the extent of damage within the kidney parenchyma based on tissue position with respect to the iceball surface as visualized on images during the MRI-guided cryoablation procedure.

A retrospective study of 20 patients cases was performed in order to statistically correlate the lack of perfusion seen on periprocedural contrast enhanced T1 post-treatment images with the iceball signal deficit seen on MRI-guided cryoblation monitoring images. Manual land-mark based registration and manual segmentation were performed on the data sets prior to analysis. In order to reduce variability in the segmentations, repeated segmentation trials to submitted to a truth-estimation scheme. Automated measurements of the distance between the iceball surface and the perfusion deficit edge were made and logistic regression model was fit to these measurements using original MATLAB scripts. The Kolmogorov-Smirnov test was applied to the Pearson residuals of the logistic regression model to assess goodness-of-fit of the model to the data. Measurements were restricted to renal parenchyma, where reliable registration could be applied.

Using 20 patient cases and over 600 data points, the perfusion loss likelihood of renal parenchyma within the iceball was described by a unique logistic regression curve, where the parameters are alpha = -0.45 and beta = 0.79. From this curve, it was determined that tissue is 50% likely to lose perfusion at 0.57mm within the iceball, while perfusion loss is 95% likely at 4.28 mm within the iceball edge. The Kolmogorov-Smirnov test for goodness-of-fit confirmed that the logistic regression model reported here describes the observed data appropriately.

Through a retrospective study of 20 patient cases, the relationship between likelihood of perfusion loss in renal parenchyma and distance within iceball was statistically quantified. From the statistical model, the margin for 95% perfusion loss likelihood was found to be 4.28mm within the iceball, which agrees the clinically accepted 3-5mm margin that is estimated during the procedure.

The statistical model presented here could serve effectively as a quantitative approach to assessing treatment progress during the MRI-guided cryoablation procedure, rather than relying on visual estimation.

1) Explain the expanding role of renal mass biopsy. 2) Explain why biopsy is necessary before all renal tumor ablations. 3) Demonstrate biopsy techniques.

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The historical incidence of complete post-ablation syndrome in patients undergoing radiofrequency ablation (RFA) of renal tumors was 29.4% with both flu-like symptoms (malaise, myalgia and nausea) and low grade fever. This study aims: (1) to evaluate the incidence of post-ablation syndrome in the patients undergoing image-guided CRYO of their renal tumors (2) to determine its impact on the quality of life in the 10 days post-renal CRYO and compare it to the post-RFA historical data.

Thirty eight patients (age 24-83 years) underwent image guided CRYO for 40 renal tumors. A telephone survey using a standardized questionnaire was conducted on days 1, 3, 5, 7 and 10 following post-CRYO. The patients' demographic details, temperature, degree of flu-like symptoms (malaise, myalgia, nausea/ vomiting), severity of pain and percentage of relief with oral analgesics, interference with general activity and with work were documented prospectively. The symptoms and interference of lifestyles were graded on a 0-10 Numeric Intensity Scale.

Post-CRYO, 6 patients (15.8%) developed low-grade fever (range 37.2-38.5ºC), 24 (63.2%) had flu-like symptoms, and 14 (36.8%) had no symptoms. The low grade fever did not exhibit any peak but the flu-like symptoms peaked on day-3 and resolved spontaneously in most patients by day-10. Six patients (15.8%) developed the full post ablation syndrome which was lower in incidence and the symptoms were less severe when compared to the post-RFA historical data (Figure 1). Post-CRYO patients with symptoms experienced pain and interference with general and work activities, peaking on day-3 in contrast to post RFA where symptoms peaked on day-1 and completely resolved by day-10.

Post-CRYO the incidence of complete post-ablation syndrome was 16% of patients with less severe symptoms compared to post-RFA. However, two third (63.2%) of the patients experienced at least one of the components of the syndrome. These symptoms were self-limiting with most symptoms peaking at day-3 and majority of the patients resumed their baseline pre-procedural levels of activity within 10 days following CRYO.

Post renal-CRYO, the incidence of complete post-ablation syndrome is lower and less severe than post-RFA and this information is useful when obtaining consent from patients during the consultation.

1) Appreciate the strengths and limitations of percutaneous ablation in treating renal tumors measuring larger than 4cm.

In the 6 edition of TNM of Union internationale contre le cancer (UICC) in 2002 the differentiation between T1a and T1b renal cell cancers (RCC) was introduced. The discrimination between T1a and T1b using a threshold of 4 cm is not justified by differences in survival, it is based on the upcoming local therapeutic options for small RCCs.
In the last years techniques for local therapies for RCCs improved and multiple studies for larger RCCs beyond 4 cm in diameter were published. Especially studies concerning partial nephrectomy (PN) and thermal ablation (e.g. radiofrequency ablation (RFA) and cyoablation) are available.

Psutka et. al. could show that after RFA of T1a and T1b RCCs, disease-free survival and recurrence free survival of T1b cancers in reduced, but overall survival is not significantly different. Takaki et. al. compared RFA versus PN in T1b RCCs. Cumulative RCC-related survival and disease-free survival was not significantly different. But there was a significant difference in overall survival, probably because RFA patients were older, had a worse American Society of Anesthesiologists (ASA) score and more single kidney interventions.

Because the sensitivity of RCC-cells to radiation is debatable, not many study data for conventional radiation of RCCs is available. Newer radiation techniques like Stereotactic body radiation therapy (SBRT) and Cyberknife could increase the amount of radiation into the tumor and reducing the applied radiation to normal tissues. Onother technique is to place afterloading catheters into the tumor under CT-guidance and perform a brachytherapy of the tumor to achieve local tumor control.

Combination of different therapies could additionally increase the therapeutic options in the individual patient and should be discussed

http://media.rsna.org/media/abstract/2014/13012542/VSIO11-16 sec.pdf