Characteristics of laparoscopic microwave ablation with renal tissue: Experimentalin vivostudy using a porcine model

The safety and efficacy of laparoscopic microwave ablation-assisted partial nephrectomy: a new avenue for the treatment of cystic renal tumors

PURPOSE

Clinically, the management of cystic renal masses is tricky. The study aims to evaluate the safety and efficacy of laparoscopic microwave ablation-assisted partial nephrectomy (LMAPN) for cystic renal tumors.

METHODS AND MATERIALS

Between November 2017 and January 2022, LMAPN was performed on 43 patients (29 men and 14 women; age range: 22-80 years; median age 54 years) with Bosniak category III (n = 15) or IV (n = 28) cystic renal tumors (size range: 1.2-5.0 cm; mean size 2.8 cm). The median follow-up period was 26 months (range: 7-56 months). Baseline and perioperative data, pathological features, renal function, postoperative complications and oncologic outcomes were collected and evaluated.

RESULTS

Forty-three cystic renal tumors were successfully managed by LMAPN. The mean operating time was 79 min (range: 40-130 min). The mean time of renal pedicle clamping was 19 min (range: 12-25 min). Mean intraoperative blood loss was 28.4 mL (range: 10-80 mL). The mean postoperative hospitalization duration was 4 days (range: 2-6 days). Negative surgical margins were diagnosed in all cases. During the follow-up, no patient appeared with distant metastasis, wound or peritoneal cavity implantation. No major but minor complications of Clavien-Dindo grade I were encountered after the operation. The 1-, 3- and 4-year overall survival rate was 100%, 96.6% and 88.5%, respectively.

CONCLUSION

This is the first study focusing on LMAPN for cystic renal tumors, demonstrating its favorable feasibility, safety and disease control. Long-term follow-up is necessary to draw conclusions on the preference and advantages of the new therapeutic approach.

Comparison of the Ablation and Hyperechoic Zones in Different Tissues Using Microwave and Radio Frequency Ablation

OBJECTIVES

The aim of this study was to compare the differences between the ablation region and hyperechoic zones in microwave and radio frequency ablation of different tissues.

METHODS

Microwave and radio frequency ablation were performed on fresh porcine muscle and liver with different power levels for 90 seconds. These 2 ablation methods were then performed on rabbit liver in vivo using 20 W for 60 seconds. The volumes of the ablation and hyperechoic zones were compared following different ablation methods.

RESULTS

The ablation zones were significantly greater than the hyperechoic zones (P < .05) with the same power and duration when using 2 ablation methods. The differences of the ablation and hyperechoic zones between muscle and liver tissues were significantly different (P < .05). The difference values of the ablation and hyperechoic zones were also significantly different (P < .05) using 2 ablation methods.

CONCLUSIONS

The hyperechoic zone may have underestimated the extent of ablation using a specified ablation time. In the same tissue, the hyperechoic zone could more accurately estimate the ablation zones using microwave ablation.

In vivo percutaneous microwave ablation in kidneys: Correlation with ex vivo data and ablation work

PURPOSE

To compare diameters of in vivo microwave ablation (MWA) performed in swine kidneys with ex vivo diameters, and to correlate with ablation work (AW), a new metric reflecting total energy delivered.

MATERIAL AND METHODS

Eighteen in vivo MWA were performed in 6 swine kidneys successively using one or two antennas (MicroThermX^®). Ablation consisted in delivering power (45-120W) for 5-15minutes. Ex vivo diameters were provided by the vendors and obtained on bovine liver tissue. AW was defined as the sum of (power)*(time)*(number of antennas) for all phases of an ablation (in kJoules). Kidneys were removed laparoscopically immediately after ablation. After sacrifice, ablations zones were evaluated macroscopically, and maximum diameters of the zones were recorded. Wilcoxon sum rank test and Pearson's correlation were used for comparisons.

RESULTS

For a single antenna (n=12), the in vivo diameters ranged from 12 to 35mm, and 15-49mm for 2 antennas (n=6). The in vivo diameters remained shorter than ex vivo diameters by 8.6%±30.1 on 1 antenna and 11.7%±26.5 on 2 antennas (P=0.31 and 0.44, respectively). AW ranged from 13.5 to 108kJ. Diameters increased linearly with AW both with 1 and 2 antennas, but only moderate correlations were observed (r=0.43 [95% confidence interval: -0.19; 0.81], P=0.16; and 0.57 [-0.44; 0.95], P=0.24, respectively).

CONCLUSION

Although diameters after in vivo renal MWA increased linearly with AW, the moderate correlation and wide standard deviations observed may justify a careful imaging monitoring during treatment delivery and settings adaptation, if needed, for optimal ablation.

Comprehensive method to predict and quantify scald burns from beverage spills

A comprehensive study was performed to quantify the risk of burns from hot beverage spills. The study was comprised of three parts. First, experiments were carried out to measure the cooling rates of beverages in a room-temperature environment by natural convection and thermal radiation. The experiments accounted for different beverage volumes, initial temperatures, cooling period between the time of service and the spill, the material which comprised the cup, the presence or absence of a cap and the presence or absence of an insulating corrugated paper sleeve. Among this list, the parameters which most influenced the temperature variation was the presence or absence of a cover or cap, the volume of the beverage and the duration of the cooling period. The second step was a series of experiments that provided temperatures at the surface of skin or skin surrogate after a spill. The experiments incorporated a single layer of cotton clothing and the exposure duration was 30 s. The outcomes of the experiments were used as input to a numerical model which calculated the temperature distribution and burn depth within tissue. Last was the implementation of the numerical model and a catalogue of burn predictions for various beverage volumes, beverage service temperatures, and durations between beverage service and spill. It is hoped that this catalogue can be used by both beverage industries and consumers to reduce the threat of burn injuries. It can also be used by treating medical professionals who can quickly estimate burn depths following a spill incident.