Info

Figure 1 RF ablation monitored with US. (A) An exophytic renal tumor (arrows) was targeted under US guidance. The dotted line is the biopsy guide, indicating the predicted path for the RF probe. (B) When monitored by US, gas bubbles form around the probe, obscuring the area with ''dirty shadowing.'' The bubbles do resolve over time, but complicate subsequent targeting, making the sequence of probe positioning very important. Abbreviations: RF, radiofrequency; US, ultrasound.

Figure 2 Cryoablation monitored with ultrasound US and CT. (A) A new hypoechoic renal tumor (arrow) was identified in a transplant kidney. (B) The tumor was targeted and ablated under US guidance. The leading edge of the ice ball is identified as a hyperechoic interface with dense posterior acoustic shadowing. (C) In a different patient, the ice ball is identified on CT as a zone of low attenuation (0 Hounsfield units). It is easy to distinguish the line of demarcation between the ice ball and unaffected tissues (arrows). Abbreviations: CT, computed tomography; US, ultrasound.

Figure 2 Cryoablation monitored with ultrasound US and CT. (A) A new hypoechoic renal tumor (arrow) was identified in a transplant kidney. (B) The tumor was targeted and ablated under US guidance. The leading edge of the ice ball is identified as a hyperechoic interface with dense posterior acoustic shadowing. (C) In a different patient, the ice ball is identified on CT as a zone of low attenuation (0 Hounsfield units). It is easy to distinguish the line of demarcation between the ice ball and unaffected tissues (arrows). Abbreviations: CT, computed tomography; US, ultrasound.

the ablation size associated with a particular applicator is important to ensuring complete ablation and avoiding inadvertent damage to surrounding structures.

Assessing response to ablation should be performed soon after the procedure itself. At Wisconsin, most tumor ablations are performed with the patient on the CT scanner. Targeting is usually performed with US guidance, and the ablation is monitored with a combination of US and CT fluoroscopy as necessary. Performing the ablation on the CT scanner allows a diagnostic contrast-enhanced CT to be performed while the patient is still under general anesthesia. US contrast agents have been used in hepatic tumor ablations to evaluate response to treatment, but the role of these materials in the treatment of RCC has not yet been evaluated (42). If the tumor is not completely ablated, additional ablations are performed in the same setting to ensure adequate treatment of the entire tumor. Note that a "tumor ghost'' is usually identified on immediate postablation imaging regardless of the ablation modality utilized (Fig. 3). In the case of cryoablation, the tumor becomes revascular-ized, and appears hypervascular immediately after the final thaw due to preservation

Figure 3 ''Tumor ghost'' after RF ablation of a RCC. (A) An exophytic RCC (arrow) was identified incidentally on a CT scan performed for other reasons. The tumor was subsequently targeted and ablated with RF, using a combination of US and CT guidance. (B) A diagnostic contrast enhanced CT performed immediately after the ablation shows the ''tumor ghost.'' The tumor often does decrease in size, likely secondary to dessication, but will not resolve. More importantly, there is no residual enhancement of the tumor itself, and the lack of adjacent renal enhancement shows there is an adequate margin. Abbreviations: CT, computed tomography; RCC, renal cell carcinoma; RF, radiofrequency; US, ultrasound.

Figure 3 ''Tumor ghost'' after RF ablation of a RCC. (A) An exophytic RCC (arrow) was identified incidentally on a CT scan performed for other reasons. The tumor was subsequently targeted and ablated with RF, using a combination of US and CT guidance. (B) A diagnostic contrast enhanced CT performed immediately after the ablation shows the ''tumor ghost.'' The tumor often does decrease in size, likely secondary to dessication, but will not resolve. More importantly, there is no residual enhancement of the tumor itself, and the lack of adjacent renal enhancement shows there is an adequate margin. Abbreviations: CT, computed tomography; RCC, renal cell carcinoma; RF, radiofrequency; US, ultrasound.

of the blood vessel walls. Tumor vessels thrombose approximately 48 to 72 hours postablation and the tumor then slowly resorbs over the course of 12 to 18 months (Fig. 4). The heat-based ablations cause immediate vascular thrombosis within the tumor, and these vessels never revascularize. Therefore, any residual tumor enhancement should be considered evidence of incomplete ablation (43). Because vessels

Figure 4 Tumor regression after ablation. (A) A contrast-enhanced T1-weighted image obtained one month after ablation of an RCC identifies the tumor and shows some subtle smooth peripheral enhancement (arrow). This kind of enhancement is often seen in the immediate postablation period and is not necessarily concerning. (B) Follow-up imaging six months later shows that the peripheral enhancement has resolved and the tumor mass has almost entirely resorbed (arrow), indicating complete ablation. Abbreviation: RCC, renal cell carcinoma.

do not have access to the tumor after treatment, tumors treated with heat-based modalities are slow to resorb, sometimes taking more than 24 months to completely resorb. Thus, the first several CT scans obtained after ablation with heat-based modalities should be primarily focused on evaluating for residual tumor enhancement.

5 Secrets to Lasting Longer In The Bedroom

5 Secrets to Lasting Longer In The Bedroom

How to increase your staying power to extend your pleasure-and hers. There are many techniques, exercises and even devices, aids, and drugs to help you last longer in the bedroom. However, in most cases, the main reason most guys don't last long is due to what's going on in their minds, not their bodies.

Get My Free Ebook


Post a comment