Estimated effective dose of CT-guided percutaneous cryoablation of liver tumors

Assessment of Local Tumor Progression After Image-Guided Thermal Ablation for Renal Cell Carcinoma

Focal enhancement typically suggests local tumor progression (LTP) after renal cell carcinoma is percutaneously ablated. However, evaluating findings that are false positive or negative of LTP is less familiar to radiologists who have little experience with renal ablation. Various imaging features are encountered during and after thermal ablation. Ablation procedures and previous follow-up imaging should be reviewed before determining if there is LTP. Previous studies have focused on detecting the presence or absence of focal enhancement within the ablation zone. Therefore, various diagnostic pitfalls can be experienced using computed tomography or magnetic resonance imaging examinations. This review aimed to assess how to read images during or after ablation procedures, recognize imaging features of LTP and determine factors that influence LTP.

Differential Imaging of Liver Tumors before and after Microwave Ablation with Electrode Displacement Elastography

Liver cancer is a leading cause of cancer-related deaths; however, primary treatment options such as surgical resection and liver transplant may not be viable for many patients. Minimally invasive image-guided microwave ablation (MWA) provides a locally effective treatment option for these patients with an impact comparable to that of surgery for both cancer-specific and overall survival. MWA efficacy is correlated with accurate image guidance; however, conventional modalities such as B-mode ultrasound and computed tomography have limitations. Alternatively, ultrasound elastography has been used to demarcate post-ablation zones, yet has limitations for pre-ablation visualization because of variability in strain contrast between cancer types. This study attempted to characterize both pre-ablation tumors and post-ablation zones using electrode displacement elastography (EDE) for 13 patients with hepatocellular carcinoma or liver metastasis. Typically, MWA ablation margins of 0.5-1.0 cm are desired, which are strongly correlated with treatment efficacy. Our results revealed an average estimated ablation margin inner quartile range of 0.54-1.21 cm with a median value of 0.84 cm. These treatment margins lie within or above the targeted ablative margin, indicating the potential to use EDE for differentiating index tumors and ablated zones during clinical ablations. We also obtained a high correlation between corresponding segmented cross-sectional areas from contrast-enhanced computed tomography, the current clinical gold standard, when compared with EDE strain images, with r2 values of 0.97 and 0.98 for pre- and post-ablation regions.

Feasibility and safety of fine positioning needle-mediated breathing control in CT-guided percutaneous puncture of small lung/liver nodules adjacent to diaphragm

To assess the efficacy, safety, and feasibility of a separate inserted positioning fine needle-mediated breathing-control technique applied to computed tomography (CT)-guided percutaneous puncture for biopsy or microwave ablation (MWA) of small lung/liver nodules near diaphragm. Total 46 patients with pulmonary/liver small nodules (≤ 3 cm in size) near diaphragm(nodule within 1 cm distance to the diaphragm)were undergone percutaneous biopsy ( n = 15) or MWA (n = 31) under the guidance of CT, and a separate positioning fine needle-mediated breathing-control technique was applied for the precise punctures. CT plain scan was performed to monitor the complications after the procedure. The patient baseline data, operation details, successful rate, major complications as well as radiation dose during the procedure were recorded and analyzed. With the assistance of a fine positioning needle insertion for controlling the breathing, the puncture success rate for biopsy or MWA reached 91.30% (42/46). For biopsy, the mean nodule diameter, nodule distance to the diaphragm, puncture time and radiation dose during CT scan were 2.27 cm ± 0.74, 0.61 cm ± 0.24, 18.67 min ± 6.23, 28.84 mSv ± 6.99, respectively; For MWA, the mean nodule diameter, nodule distance to the diaphragm, puncture time and CT radiation dose were 2.35 cm ± 0.64, 0.69 cm ± 0.23, 38.71 min ± 13.65, 33.02 mSv ± 8.77, respectively. Totally, there were three and four cases found minimal puncture-related hemoptysis and pneumothorax needed no additional treatments, respectively. We recently developed and verified a feasible, safe and highly effective puncture technique with reasonable radiation dose for CT-guided biopsy or MWA for small nodules abutting diaphragm, therefore worthy of extensive application to similar clinical situations.

Asian Conference on Tumor Ablation guidelines for renal cell carcinoma

Thermal ablation has been established as an alternative treatment for renal cell carcinoma (RCC) in patients who are poor candidates for surgery. However, while American and European guidelines have been established for American and European patients, respectively, no ablation guidelines for Asian patients with RCCs have been established many years after the Asian Conference on Tumor Ablation (ACTA) had been held. Given that Western guidelines are difficult to apply to Asian patients due to differences in body habitus, economic status, and insurance systems, the current review sought to establish the first version of the ACTA guidelines for treating a RCC with thermal ablation.

Percutaneous Adrenal Radiofrequency Ablation: A Short Review for Endocrinologists

Image-guided radiofrequency ablation (RFA) has been accepted as a minimally invasive treatment for adrenal tumors in patients who are unable to undergo adrenalectomy. Accordingly, this treatment has become more readily available for treating functioning or non-functioning adrenal masses. Thus, endocrinologists need a better understanding of percutaneous RFA of adrenal tumors. The purpose of this review is to briefly describe the basic mechanism of RFA, indications and contraindications, patient preparation prior to RFA, type of complications, how to avoid complications, RFA procedures, and treatment outcomes.

Percutaneous cryoablation for renal cell carcinoma using ultrasound-guided targeting and computed tomography-guided ice-ball monitoring: radiation dose and short-term outcomes

BACKGROUND

Usefulness of ultrasound (US)-guided mass targeting and computed tomography (CT)-guided ice-ball monitoring in percutaneous cryoablation (PCA) for renal cell carcinoma (RCC) is still uncertain.

PURPOSE

To assess radiation dose and short-term outcomes of PCA for RCC using US-guided targeting and CT-guided ice-ball monitoring.

MATERIAL AND METHODS

Thirty-nine consecutive patients who underwent PCA for biopsy-proven RCC were included. Mass targeting was performed with US and ice-ball was monitored with CT guidance. Effective radiation dose of CT during PCA was recorded. Follow-up was conducted with contrast-enhanced CT or magnetic resonance imaging (MRI) (mean follow-up time = 10.1 ± 7.0 months). Local tumor progression was defined by the presence of focal enhancing areas at the ablation zone (CT, ≥ 20 HU; MRI, presence of focal enhancement on subtraction contrast-enhanced image). Technical success, major complication rate (e.g. Clavien-Dindo classification ≥ 3), and one-year local tumor progression-free survival (PFS) rate were analyzed.

RESULTS

Mean effective radiation dose in association with PCA was 12.1 ± 4.5 mSv (range = 7.0-25.2 mSv). Technical success was achieved in 100%. Local tumor progression occurred in a single patient (2.6%, 1/39), and one-year local tumor PFS rate was 95.7%. No major complication was found.

CONCLUSION

PCA using US-guided targeting and CT-guided ice-ball monitoring may allow acceptable local tumor control for RCC, as a radiation-reducing strategy.

Protection from injury of organs adjacent to a renal tumor during percutaneous cryoablation

Renal cryoablation has become accepted as treatment for small renal tumors as an alternative to surgery. However, parallel with the increase in the use of this therapy, there also has been increases in the number of reports of complications related to renal cryoablation. One potential complication is injury to important non-renal structures adjacent to the ablated renal tumor, such as the colon, duodenum, ureter, psoas muscle and so on. To prevent injury of adjacent organs, separating organs from the tumor is desirable. Over the past 15 years, several techniques have been developed to protect against injury of organs adjacent to renal tumors that are targets of cryoablation. The most commonly used technique for this purpose has been hydrodissection. Others include dissection with gas, balloon dissection and probe traction. To avoid injury of a ureter running near the renal tumor, pyeloperfusion is known to be useful. The rate of cases necessitating avoidance of organ injury by using these techniques is relatively high. In some cases, more than two techniques are combined. In the present review, we provided an overview of techniques currently available to protect against organ injuries, and discussed the advantages and disadvantages of each technique.

Radiation Dose and Risk Estimates of CT-Guided Percutaneous Liver Ablations and Factors Associated with Dose Reduction

PURPOSE

To determine the radiation dose associated with CT-guided percutaneous liver ablations and identify potential risk factors that result in higher radiation doses.

MATERIALS AND METHODS

Between June 2011 and June 2015, 245 consecutive patients underwent 304 CT-guided liver ablation treatments. Patient demographics, tumor characteristics and procedural parameters were identified and analyzed. The peak skin dose and effective dose were assessed for each procedure. Excess relative risk related to radiation effects was calculated. A logistic regression model was prepared by means of stepwise logistic regression to identify variables predictive of increased radiation exposure.

RESULTS

Tumor ablations were performed with microwave (n = 220), radiofrequency (n = 74) or irreversible electroporation (IRE) (n = 10). The mean peak skin dose for ablations was 239.2 ± 136.4 mGy, and the mean effective dose was 36.6 ± 22.3 mSv. Of the patient and procedural parameters that were analyzed, increasing weight, use of intravenous contrast and/or hydrodissection during the procedure, together with treatment of multiple lesions in the same sitting were all associated with higher radiation exposure. The mean increase in the absolute risk of fatal malignancy from a single procedure was 0.18% (range 0.02-0.9%). No deterministic skin changes were identified in the patient cohort.

CONCLUSION

The overall risk of stochastic and deterministic effects from radiation associated with CT-guided ablations is low compared with other inherent procedural complications. This study identifies several factors that are associated with higher radiation dose in percutaneous liver ablation procedures.

Comparison of General Anesthesia and Conscious Sedation during Computed Tomography–Guided Radiofrequency Ablation of T1a Renal Cell Carcinoma

Purpose

Percutaneous radiofrequency ablation is so painful that this treatment requires pain control such as conscious sedation or general anesthesia. It is still unclear which type of anesthesia is better for treatment outcomes of renal cell carcinoma. This study aimed to compare general anesthesia and conscious sedation in treating patients with renal cell carcinoma with radiofrequency ablation.

Methods

Between 2010 and 2015, 51 patients with biopsy-proven renal cell carcinomas (<4 cm) were treated with computed tomography–guided radiofrequency ablation. General anesthesia was performed in 41 and conscious sedation was performed in 10 patients. Tumour size, local tumour progression, metastasis, major complication, effective dose, glomerular filtration rate difference, and recurrence-free survival rate were compared between these groups.

Results

The mean tumour size was 2.1 cm in both groups ( P = .673). Local tumour progression occurred in 0% (0 of 41) of the general anesthesia group, but in 40% (4 of 10) of the conscious sedation group ( P = .001). Metastases in these groups occurred in 2.4% (1 of 41) of the general anesthesia group and 20% (2 of 10) of the conscious sedation group ( P = .094). No major complications developed in either group after the first radiofrequency ablation session. The mean effective doses in these groups were 21.7 mSv and 21.2 mSv, respectively ( P = .868). The mean glomerular filtration rate differences in the general anesthesia and conscious sedation groups were −13.5 mL/min/1.73 m2 and −19.1 mL/min/1.73 m2, respectively ( P = .575). Three-year recurrence-free survival rates in these groups were 97.6% and 60.0%, respectively ( P = .001).

Conclusions

General anesthesia may provide better intermediate outcomes than conscious sedation in treating small renal cell carcinomas with radiofrequency ablation.

Low-dose CT protocols for guiding radiofrequency ablation for the treatment of small renal cell carcinomas

OBJECTIVE

Computed tomography (CT)-guided radiofrequency ablation (RFA) results in a high radiation dose. This study aimed to assess low-dose CT protocols for guiding RFA and oncologic outcomes for the treatment of small renal cell carcinoma (RCC).

MATERIALS AND METHODS

Between December 2011 and December 2014, CT-guided RFA was performed in 31 patients with 31 biopsy-proven RCCs (median, 2.1 cm). RFA included planning, targeting, monitoring and survey phases. The dose length product (DLP), CT dose index volume (CTDIvol), effective dose, number of scans, scan range, tube current and exposure time of RFA phases were compared. The 3-year recurrence-free survival rate was recorded. Nonparametric or parametric repeated-measures ANOVA with Dunn's or Tukey-Kramer multiple comparisons and Kaplan-Meier analysis were used for statistical analysis.

RESULTS

The median total DLP, CTDIvol and effective dose of CT-guided RFA procedures per session were 1238.8 mGy (range 517.4-3391.7 mGy), 259.7 mGy (10.7-67.9 mGy) and 18.6 mSv (7.8-50.9 mSv), respectively. The median DLP, CTDIvol, effective dose, number of scans, tube current and exposure time during the targeting phase were higher than those during the other phases (p < 0.001). The scan range in the targeting phase was the same as that in the monitoring phase (p > 0.05) but smaller than those in the planning and survey phases (p < 0.001). The 3-year recurrence-free survival rate was 96.7%.

CONCLUSIONS

Low-dose CT protocols for guiding RFA may reduce radiation dose without compromising oncologic outcomes. Reducing the number of scans during the targeting phase contributes to dose reduction.

Ultrasound-guided genitourinary interventions: principles and techniques

Ultrasound (US) is often used to guide various interventional procedures in the genitourinary (GU) tract because it can provide real-time imaging without any radiation hazard. Moreover, US can clearly visualize the pathway of an aspiration or biopsy needle to ensure the safety of the intervention. US guidance also helps clinicians to access lesions via the transabdominal, transhepatic, transvaginal, transrectal, and transperineal routes. Hence, US-guided procedures are useful for radiologists who wish to perform GU interventions. However, US-guided procedures and interventions are difficult for beginners because they involve a steep initial learning curve. The purpose of this review is to describe the basic principles and techniques of US-guided GU interventions.

CT-Guided Radiofrequency Ablation of T1a Renal Cell Carcinoma in Korea: Mid-Term Outcomes

Objective

To evaluate the mid-term outcomes of percutaneous radiofrequency ablation (RFA) treatment in patients with small (< 4 cm) renal cell carcinoma (RCC) in Korea.

Materials and Methods

Between 2010 and 2015, 51 patients (40 men and 11 women; median age, 57 years) with biopsyproven 51 RCC were treated using CT-guided RFA. All patients were clinically staged T1aN0M0 prior to RFA. The median tumor size and follow-up period were 2.1 cm (range, 1.0–3.9 cm) and 26 months (4–60 months), respectively. Local tumor progression, distant metastasis, primary and secondary effectiveness rates, and major complication rates were recorded. Estimated glomerular filtration rates (GFRs) between pre-RFA and last follow-up were compared using paired t tests. The 2-year recurrence-free survival rate was calculated using Kaplan-Meier survival analysis.

Results

Of the 51 patients, 2 (3.9%) experienced local tumor progression, and 1 (2.0%) had lymph node metastasis after the first RFA session. Primary and secondary effectiveness rates were 96.1% (49/51) and 100% (1/1), respectively. Only 1 patient experienced a major complication (uretero-pelvic stricture) after the second RFA session for treating a local tumor progression, and the major complication rate was 1.9% (1/52). The median pre-RFA and last follow-up GFRs were 87.1 mL/ min/1.73 m² (14.2–142.7 mL/min/1.73 m²) and 72.0 mL/min/1.73 m² (7.2–112.6 mL/min/1.73 m²), respectively (p < 0.0001). The 2-year recurrence-free survival rate was 96.0%.

Conclusion

CT-guided RFA is a safe and effective treatment in Korean patients with T1a RCC because of excellent mid-term outcomes.

Practical dose reduction tips for abdominal interventional procedures using CT-guidance

Reducing the radiation dose should be an endeavor not only for diagnostic CT exams but also for interventional procedures using CT-guidance. Given that interventional procedures vary in scope and complexity, there is greater variability in radiation doses delivered during CT procedures. The goal in an interventional procedure is simply to advance the interventional instruments into the target lesions, and as such diagnostic level doses are not required and only narrow scan range scans need to be acquired. Adherence to the principles outlined in this article will allow such procedures to be performed with reduced radiation doses.

Radiation dose optimization for CT-guided interventional procedures in the abdomen and pelvis

Radiation dose to patients can be high for some CT-guided interventional procedures in the abdomen and pelvis, especially tumor ablations. Strategies for radiation dose reduction include choosing an alternative guidance modality that does not use radiation whenever feasible, restricting the cranio-caudal length of interventional scans to the interventional target, and refinement of technical skills in order to minimize the number of scans acquired for interventional guidance. Dose optimization for these procedures is best achieved by lowering the tube current relative to the prior diagnostic scan, choosing dose efficient scanning modes, and using intermittent-mode, narrowly collimated CT fluoroscopy for interventional guidance.

Sonographically guided transhepatic core biopsies of right renal and adrenal masses: safety and short-term follow-up

OBJECTIVES

The purpose of this study was to retrospectively evaluate the accuracy and safety of sonographically guided transhepatic biopsies of right upper renal and adrenal masses.

METHODS

Ten sonographically guided transhepatic biopsies were performed in 10 patients with 6 right upper renal masses and 4 right adrenal masses that were invisible or inaccessible via an extrahepatic route. The control population comprised 19 sonographically guided extrahepatic biopsies that were performed in 19 patients with 18 right upper renal masses and 1 right adrenal mass. Transhepatic and extrahepatic biopsies were compared with respect to the diagnostic and complication rates. The mass sizes, biopsy distances, numbers and lengths of cores, and biopsy durations were also compared.

RESULTS

The diagnostic rates of transhepatic and extrahepatic biopsies were 90% (9 of 10) and 89% (17 of 19), respectively (P > .999). The complication rates of transhepatic and extrahepatic biopsies were 10% (1 of 10) and 21% (4 of 19; P > .999). None of these biopsies resulted in major complications. The mean mass sizes, biopsy distances, and numbers of cores ± SD for transhepatic and extrahepatic biopsies were 33.0 ± 14.3 and 46.9 ± 18.5 mm, 100.5 ± 17.9 and 76.5 ± 9.9 mm, and 2.7 ± 0.9 and 4.0 ± 0.7, respectively (P = .046, .038, and .001). However, the core lengths and biopsy durations were not significantly different between these biopsies (P = .91 and .077).

CONCLUSIONS

Sonographically guided transhepatic core biopsies appear to be feasible and safe procedures for the histologic diagnosis of right upper renal and adrenal masses that are either invisible or inaccessible via an extrahepatic route.

Percutaneous radiofrequency ablation of renal cell carcinomas in patients with von Hippel Lindau disease: indications, techniques, complications, and outcomes

Renal cell carcinoma (RCC) in patients with von Hippel Lindau (VHL) disease tends to be multifocal, bilateral, and recur or develop new tumors after removal. These characteristics make treating hereditary RCCs difficult for urologists or radiologists compared to treating a sporadic RCC. Radiofrequency ablation (RFA) is a minimally-invasive treatment for small hereditary RCCs associated with a low complication rate and a minimal decrease in renal function. No RFA guidelines have been established about what to treat and when and how to ablate RCCs in patients with VHL disease. Besides, reports on complications and treatment outcomes in this patient group are rare. The purpose of this review is to discuss the indications, techniques, complications, and outcomes of RFA in treating RCC in patients with VHL disease.

Thermal ablation in renal cell carcinoma: what affects renal function?

Because of its minimally invasive nature, thermal ablation is increasingly performed in patients with renal cell carcinoma (RCC) who are poor surgical candidates. Thermal ablation has been associated with excellent outcomes, and thus has been regarded as a viable alternative to nephron-sparing surgery. Many papers report minimal to no reduction in renal function after ablation therapies. However, in order to achieve good local control, normal renal tissue must be sacrificed, subsequently leading to reduced renal function. The amount of normal renal tissue to be ablated depends on the size, location, and number of RCCs, as well as the type of thermal ablation applied. However, there are few reports about what reduces renal function following thermal ablation therapies. The purpose of this review was to discuss factors that affect reduction in renal function and to assess the relationship between local tumour control and renal function.