Laparoscopic US-guided RFA is utilized in anterior tumors and tumors located within 1 cm of the bowel, as described by Sterrett et al. [3]. The laparoscopic technique permits the manipulation of organs assuring that the RFA treatment is directed only toward the intended target decreasing the risk of thermal injury to the surrounding tumor free tissue. This allows for a reduction in the number of post-procedural complications resulting from thermal injury [3, 7].

First, with the patient placed on their unaffected side, small port incisions are made to allow full abdominal insufflation. Since, US imaging lacks the ability to detect heat; we recommend the placement of peripheral temperature monitors to help aid in ablation success. If temperature monitors are not utilized end goals can be monitored by pre-set impedance or temperature goals of the RFA probes depending on the system used and by direct visualization. Gas bubbles created during the ablation cycle can interfere with the US signal thus making US an unreliable way of monitoring the treatment. Three to four fiberoptic temperature probes (LumaSense, Santa Clara, CA) are placed at the peripheral and deep margins, 5 mm from boundary between the tumor and normal renal parenchyma (Fig. 16.6). Temperature probe placement is visualized under US guidance and can be aided using 5-Fr coaxial guide needle encompassed in a radiopaque sheath (Huey, Cook Vascular, Inc., Vandergrift, PA, USA) [7, 29]. Next, the RFA probe is directed toward the target tissue under US-guidance. After all temperature probes have reached the treatment goal of 60 °C, or the impedance/temperature goal has been met the RFA probe is removed, again under US guidance [3, 29].

The advantage of the laparoscopic RFA approach is the “intent to treat” described by Hui et al. and Castle et al. Percutaneous RFA can be performed by surgeons and interventionists in contrast to laparoscopic treatments which are solely performed by surgeons. The single session success rate for percutaneous approach was found to be 87% (95% CI, 82–91%) compared to 94% (95% CI, 92–96%) in the laparoscopic approach. This difference suggests that surgeons may have a more aggressive approach compared to that of interventionists [30].

As compared to laparoscopic RFA, the percutaneous ablation technique is best utilized for posteriorly located tumors [7]. Major delivery mechanisms include CT, MRI, cone-beam CT, and image fusion modalities; CT-guided RFA is preferred by most providers [31].

CT-RFA is best utilized for posterior tumors. The patient is first placed in either the prone or lateral decubitus position. The lateral decubitus position allows for the deflation of the dependent lung decreasing movement of the kidney secondary to respiration [31]. This decreases the likelihood of pleural space injury and pneumothorax when treating upper pole masses [2, 7]. The prone position is used most often for CT-RFA of SRM. This position increases the separation between the costal margin and iliac crest allowing for a larger insertion window. However, this also increases the length of the kidney in proximity to the lung hence limiting its use for upper pole lesions [2]. CT-RFA is best performed under general anesthesia allowing manipulation of respiratory movements during probe placement [1, 7, 19].

CT-RFA is widely available decreasing the cost of the procedure [31]. CT-RFA procedures can be done at outpatient centers lowering the cost of hospital stay and resultant complications. Compared to the laparoscopic approach CT-RFA has fewer complications since laparoscopic insertion and insufflation is avoided [7]. Disadvantages include gantry-size limited access to the patient, exposure to ionizing radiation, and lack of treatment endpoint via real-time temperature monitoring [19, 31].

MR-RFA was first described by Anzai et al., in 1995 for the treatment of brain tumors [32]. In 2003, Gervais and Mayo-Smith et al. reported successful MR-RFA for renal tumors [32]. In recent literature Lewin et al. provides expertise on renal MR-RFA procedures, first introduced in 1998 [2, 7]. There are several advantages of MRI-RFA compared to CT guided treatment; most notably the lack of patient radiation exposure [2, 33]. MRI allows for increased spatial resolution and amplification of soft-tissue elements [2]. The use of MRI allows ablation of difficult-to-access lesions with trajectory limits in close vicinity to vital structures especially tumors treated near the diaphragm. These tumors are not readily accessible by CT guidance due to triangulation limits or by US due to air-artifact resulting in the increased incidence of pneumothorax [2]. More than one ablation confirmation is not possible in CT-guided RFA since contrast is needed to visualize residual tumor cells, which takes time to clear. Once contrast is injected subsequent ablation success cannot be confirmed due to the obstruction of the lingering original contrast material. As many as four ablation sessions have been reported for successful CT-RFA treatment. In contrast, MR allows for the immediate detection of post-ablation residual tumor by the presence of T2-weighted MR isointense or hyperintense signals. If residual tumor is observed, the provider can perform further ablation cycles within the same session. This eliminates the need of additional visits which would require further patient repositioning and exposure to contrast media [2, 33, 34]. It has been reported that 92–100% of MR-ablations can be achieved successfully in one session [34].

Real-time monitoring can also be achieved via MR fluoroscopy using rapid gradient echo sequences. Real-time monitoring more readily allows for the identification of a therapeutic end-point and the manipulation of the thermal ablation zone during the procedure. However, the interface of the MRI scanner presents a challenge for continuous imaging. This can be overcome by the use of intermittent MR scanning between ablations [2]. Disadvantages of MR-RFA include limited gantry size, procedure length, machine availability, equipment cost, and the need for MRI compatible sensors (as discussed earlier) [1, 31].

This system utilizes a large rotating C-arm and digital fluoroscopy. Manipulation of the C-arm under fluoroscopy creates a 3D model of the target allowing for precise ablation (Fig. 16.7). The trajectory is then projected onto the patient allowing for further guidance for placement of the needle along the trajectory. Once the needle is placed, further imaging is obtained via rotational angiography within seconds. This confirms needle placement and allows for further manipulation of the trajectory [1] (Fig. 16.8). A study, performed by Cheng et al., compared patient radiation exposure during cone-beam CT procedures versus conventional CT techniques in RFA ablation. Patients who underwent cone-beam ablations sustained a lower radiation dose compared to the conventional technique (P < 0.5), while having comparable treatment success [35]. This system is limited by respiratory movement since the point in the respiratory cycle where the images are obtained must be identical to that of needle placement. This can be overcome by having the patient hold end expiration or utilizing general anesthesia [1].