Assessment of ablative margin by unenhanced magnetic resonance imaging after radiofrequency ablation for hepatocellular carcinoma

Purpose

The aim of this study was to evaluate the feasibility of magnetic resonance imaging (MRI) without a contrast agent to visualize the ablative margin after radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC), compared with enhanced CT.

Methods

Twenty-five HCCs in 19 patients were treated by RFA. T1-weighted MRI was performed before and after RFA, and the signal intensities of the tumors and surrounding liver tissues were measured. Treatment efficacy was assessed based on three grades: margin (+), a continuous high-intensity rim around the index tumor; margin zero, a partially discontinuous high-intensity rim; margin (−), the tumor extends beyond the high-intensity rim.

Results

Twelve (86%) of fourteen low-intensity tumors on the pre-MRI were visualized as low-intensity tumors on post-MRI, and the ablative margins were visualized as high-intensity rims. Two (67%) of three high-intensity tumors on pre-MRI were visualized as higher-intensity tumors in the high-intensity ablative margin. Because the signal intensities of tumors and surrounding tissues in 14 tumors that were low- or high-intensity tumors on pre-MRI increased to the same extent, the tumors and ablative margin could be distinguished on post images. In 6 (75%) of the 8 iso-intensity tumors on pre-MRI, the ablative margin and tumor could also not be discriminated on post-MRI. The overall agreement between MRI and CT for the ablative margin was good (κ coefficient = 0.716, p = 0.00002).

Conclusion

In 82% of low- or high-intensity tumors on pre-MRI, post-MRI without a contrast agent enabled visualization of the ablative margin as a high-intensity rim, and it was possible to evaluate the ablative margin earlier and easier than with enhanced CT.     

Assessment of ablative margin by MRI with ferucarbotran in radiofrequency ablation for liver cancer: comparison with enhanced CT

Objectives

Our aim was to determine whether ablated liver parenchyma surrounding a tumour can be assessed by MRI with ferucarbotran administered prior to radiofrequency ablation (RFA) compared with enhanced CT.

Methods

55 hepatocellular carcinomas (HCCs) in 42 patients and 5 metastatic liver cancers in 3 patients were treated by RFA after ferucarbotran administration. We then performed T₂* weighted MRI after 1 week and enhanced CT after 1 month. T₂* weighted MRI demonstrated the ablated parenchyma as a low-intensity rim around the high intensity of the ablated tumour in these cases. The assessment was allocated to one of three grades: margin (+), high-intensity area with continuous low-intensity rim; margin zero, high-intensity area with discontinuous low-intensity rim; and margin (−), high-intensity area extending beyond the low-intensity rim.

Results

Margin (+), margin zero and margin (−) were found in 17, 35 and 5 nodules, respectively. All 17 nodules with margin (+) and 13 of those with margin zero were assessed as having sufficient abalative margins on CT. The remaining 22 nodules with margin zero had insufficient margins on CT. The overall agreement between MRI and CT for the diagnosis of the ablative margin was moderate (κ=0.507, p<0.001). No local recurrence was found in 15 HCC nodules with margin (+), whereas local recurrence was found in 4 (11.8%) out of 34 HCC nodules with margin zero.

Conclusion

Administration of ferucarbotran before RFA enables the ablative margin to be visualised as a low-intensity rim, and also enables the evaluation of the ablative margin to be made earlier and more easily than with enhanced CT.Radiofrequency ablation (RFA) has become a widely used treatment for hepatocellular carcinoma (HCC) [1], with some studies reporting significant long-term survival results [2,3]. One of the most difficult and troublesome issues in RFA is the lack of a reliable method for confirming that complete necrosis has been achieved in the treated lesion. CT and MRI are commonly used to evaluate the therapeutic response in the ablated tumours. The imaging hallmark of successful treatment is a lack of enhancement in the index tumour on CT or MRI [4,5]. However, previous pathological examination has demonstrated the presence of microsatellite nodules around the original tumour [6,7]. Therefore, it is necessary to ablate liver parenchyma surrounding the original tumour, as well as the tumour itself, and the ablation zone of the surrounding normal tissue needs to be recognised. In fact, several studies [8-10] have reported that the local recurrence rate in nodules with sufficient ablative margin is lower than that in those without sufficient ablative margin. The ablative margin is conventionally assessed by comparing enhanced CT images before and after RFA for HCC tumours.Mori et al [11] reported a new method of evaluating the ablative margin using ferucarbotran (Resovist; Bayer Schering Pharma, Berlin, Germany), and demonstrated that the ablative margin is easily assessed by MRI. Ferucarbotran is a clinically approved superparamagnetic iron oxide (SPIO) that is liver specific on MRI. It is composed of SPIO microparticles (γ-Fe₂O₃) coated with carboxydextran. After intravenous administration, ferucarbotran is phagocytosed by Kupffer cells and equally distributed throughout the entire liver [12]. Kupffer cells are much more dominant in hepatic parenchyma than in cancer tissue. Therefore, the signal intensity from cancer in T₂* weighted sequences becomes relatively high compared with that from hepatic parenchyma. Ferucarbotran in ablated hepatic parenchyma would remain after ablation, showing low intensity around high-intensity cancer on post-ablational MR images.The aim of this study was to determine the usefulness of ablative margin assessment by enhanced MRI using ferucarbotran administered before RFA in patients with liver cancer in comparison with post-ablation enhanced CT images after 1 month.     

Treatment response assessment of radiofrequency ablation for hepatocellular carcinoma: usefulness of virtual CT sonography with magnetic navigation

Purpose

Virtual CT sonography using magnetic navigation provides cross sectional images of CT volume data corresponding to the angle of the transducer in the magnetic field in real-time. The purpose of this study was to clarify the value of this virtual CT sonography for treatment response of radiofrequency ablation for hepatocellular carcinoma.

Patients and methods

Sixty-one patients with 88 HCCs measuring 0.5–1.3 cm (mean ± SD, 1.0 ± 0.3 cm) were treated by radiofrequency ablation. For early treatment response, dynamic CT was performed 1–5 days (median, 2 days). We compared early treatment response between axial CT images and multi-angle CT images using virtual CT sonography.

Results

Residual tumor stains on axial CT images and multi-angle CT images were detected in 11.4% (10/88) and 13.6% (12/88) after the first session of RFA, respectively (P = 0.65). Two patients were diagnosed as showing hyperemia enhancement after the initial radiofrequency ablation on axial CT images and showed local tumor progression shortly because of unnoticed residual tumors. Only virtual CT sonography with magnetic navigation retrospectively showed the residual tumor as circular enhancement. In safety margin analysis, 10 patients were excluded because of residual tumors. The safety margin more than 5 mm by virtual CT sonographic images and transverse CT images were determined in 71.8% (56/78) and 82.1% (64/78), respectively (P = 0.13). The safety margin should be overestimated on axial CT images in 8 nodules.

Conclusion

Virtual CT sonography with magnetic navigation was useful in evaluating the treatment response of radiofrequency ablation therapy for hepatocellular carcinoma.     

Microwave ablation assisted by a real-time virtual navigation system for hepatocellular carcinoma undetectable by conventional ultrasonography

Objectives

To evaluate the efficiency and feasibility of microwave (MW) ablation assisted by a real-time virtual navigation system for hepatocellular carcinoma (HCC) undetectable by conventional ultrasonography.

Methods

18 patients with 18 HCC nodules (undetectable on conventional US but detectable by intravenous contrast-enhanced CT or MRI) were enrolled in this study. Before MW ablation, US images and MRI or CT images were synchronized using the internal markers at the best timing of the inspiration. Thereafter, MW ablation was performed under real-time virtual navigation system guidance. Therapeutic efficacy was assessed by the result of contrast-enhanced imagings after the treatment.

Results

The target HCC nodules could be detected with fusion images in all patients. The time required for image fusion was 8–30 min (mean, 13.3 ± 5.7 min). 17 nodules were successfully ablated according to the contrast enhanced imagings 1 month after ablation. The technique effectiveness rate was 94.44% (17/18). The follow-up time was 3–12 months (median, 6 months) in our study. No severe complications occurred. No local recurrence was observed in any patients.

Conclusions

MW ablation assisted by a real-time virtual navigation system is a feasible and efficient treatment of patients with HCC undetectable by conventional ultrasonography.     

Findings of multidetector row computed tomography of HCCs treated by HIFU ablation

Purpose

We evaluated the efficacy of high-intensity focused ultrasound (HIFU) ablation for hepatocellular carcinoma (HCC), and a long-term study by follow-up multidetector-row computed tomography (CT) was conducted to evaluate the changes occurring in the treatment area following the HIFU ablation.

Materials and methods

HIFU ablation was carried out in 14 patients with small HCCs (≤3 lesions, ≤3 cm in diameter). The HIFU system (Chongqing Haifu Tech) was used under ultrasound guidance. The evaluations were performed by follow-up CT at 1 week, 1, 3, 6 and 12 months after the HIFU ablation.

Results

HIFU ablation was carried out successfully in 11 of the 14 patients. At 1 week after the HIFU, a peripheral rim enhancement was found in all cases (100%). This finding was persistent in 6 of the 11 cases (54.5%) at 1 month, and in 1 of the 11 (9%) cases at 3 months after HIFU ablation. In all cases, the rim enhancement disappeared by 6 or 12 months after the HIFU ablation. At the 12 months follow-up, a decrease in the diameter of the ablated lesions was found. The enhancement around the treated area was found to be persistent at the 12 months follow-up in the one case of recurrence of the treated site in which the safety margin was not sufficiently wide. During the follow-up period, there were 2 cases with residual of HCC tumors. We performed radiofrequency ablation (RFA) for these residual tumors after the HIFU ablation.

Conclusion

To ascertain the cause of the peripheral enhancement on follow-up CT images after the HIFU ablation, in particular, to determine whether it might be caused by residual tumor or recurrence at the treated site, careful follow-up is important, especially in cases where the safety margin of the ablated area was not sufficiently wide.     

Use of fusion imaging combining contrast-enhanced ultrasonography with a perflubutane-based contrast agent and contrast-enhanced computed tomography for the evaluation of percutaneous radiofrequency ablation of hypervascular hepatocellular carcinoma

Objective

We evaluated the efficacy of fusion imaging, which fuses contrast-enhanced ultrasonography images with arterial-phase, contrast-enhanced CT images as a reference on a single screen in real time, for the evaluation of the effectiveness of radiofrequency ablation for treatment of hypervascular hepatocellular carcinoma.

Materials and methods

Eighty hepatocellular carcinoma lesions with a maximum diameter of between 1 and 3 cm that were scheduled for treatment with radiofrequency ablation were enrolled in this prospective study. After bolus injection of perflubutane-based contrast agent, fusion imaging combining contrast-enhanced ultrasonography images and arterial-phase, contrast-enhanced CT images was performed one day after radiofrequency ablation. We used two functions, which were subsets of the fusion imaging, to confirm the location of the hepatocellular carcinoma lesions in the ablated areas and to evaluate the presence or absence of an adequate safety margin. Contrast-enhanced CT was performed one month after the ablation. Two blinded observers reviewed the images obtained using both modalities to evaluate the effect of ablation.

Results

When the one-month contrast-enhanced CT images were used as the reference standard, the sensitivity, specificity, and accuracy of the one-day fusion imaging for the diagnosis of adequate ablation were 97%, 83%, and 96%, respectively; the kappa value for the agreement between the findings obtained using the two modalities was 0.75.

Conclusion

Fusion imaging combining contrast-enhanced ultrasonography images and arterial-phase, contrast-enhanced CT images as a reference appears to be a useful method for the early evaluation of the efficacy of radiofrequency ablation for the treatment of hypervascular hepatocellular carcinoma.     

How to manage the patients with unsatisfactory results after ethanol ablation for thyroid nodules: role of radiofrequency ablation

Purpose

Although ethanol ablation (EA) is effective in the treatment of cystic thyroid nodules, it is less effective in nodules with solid component. Therefore refractory cases with solid component require another treatment modality such as radiofrequency ablation (RFA), which is effective in both solid and cystic thyroid nodules. We prospectively evaluated the efficacy of additional RFA and factors related to volume reduction in patients showing unsatisfactory results after a single session of EA.

Materials and methods

Of 94 patients with predominantly cystic thyroid nodules who underwent EA, 20 patients underwent additional RFA because of incompletely resolved clinical problems (symptomatic score reduction <50%) and presence of residual solid component at 1-month follow-up on ultrasonography. Improvement of clinical symptoms and nodule volume reduction were evaluated 6 month later. We evaluated factors related to nodule volume reduction after EA and RFA.

Results

RFA after a single session of EA was effective in reducing mean symptom score from 4.8 to 1.1 (p < 0.001), mean cosmetic score from 3.5 to 1.4 (p < 0.001) and mean nodule volume from 11.3 to 0.9 mL (p < 0.001). The only independent factor related to volume reduction after EA was the presence of a solid component (p < 0.001), and EA was less effective in nodules when solid component >20% (p = 0.001). We identified no factors related to volume reduction after RFA.

Conclusion

RFA is effective in treatment of benign predominantly cystic thyroid nodules in patients whose clinical problems were incompletely resolved after EA.     

Assessment of liver tumor response by high-field (3T) MRI after radiofrequency ablation: Short- and mid-term evolution of diffusion parameters within the ablation zone

Purpose

To compare the apparent diffusion coefficient (ADC) values of malignant liver lesions on diffusion-weighted MRI (DWI) before and after successful radiofrequency ablation (RF ablation).

Materials and methods

Thirty-two patients with 43 malignant liver lesions (23/20: metastases/hepatocellular carcinomas (HCC)) underwent liver MRI (3.0 T) before (<1 month) and after RF ablation (at 1, 3 and 6 months) using T2-, gadolinium-enhanced T1- and DWI-weighted MR sequences. Jointly, two radiologists prospectively measured ADCs for each lesion by means of two different regions of interest (ROIs), first including the whole lesion and secondly the area with the visibly most restricted diffusion (MRDA) on ADC map. Changes of ADCs were evaluated with ANOVA and Dunnett tests.

Results

Thirty-one patients were successfully treated, while one patient was excluded due to focal recurrence. In metastases (n = 22), the ADC in the whole lesion and in MRDA showed an up-and-down evolution. In HCC (n = 20), the evolution of ADC was more complex, but with significantly higher values (p = 0.013) at 1 and 6 months after RF ablation.

Conclusion

The ADC values of malignant liver lesions successfully treated by RF ablation show a predictable evolution and may help radiologists to monitor tumor response after treatment.     

Fusion of multislice computed tomography and electroanatomical mapping data for 3D navigation of left and right atrial catheter ablation

Purpose

To assess whether fusion of multislice computed tomography (CT) images with electroanatomical (EA)-mapping data using a new image integration module (CartoMerge™) is feasible and accurate to navigate ablation catheters in right and left atrial catheter ablation.

Material and methods

Twenty-four patients were examined with ECG-gated cardiac multislice CT (64 mm × 0.6 mm, 0.33 s) 1 day before left atrial (LA) (15 patients) radiofrequency or right atrial cavotricuspid isthmus ablation (9 patients). CT data were fused with the non-fluoroscopic EA-mapping data by using dedicated software (CartoMerge™) and the value of CT was analysed.

Results

In 23/24 (96%) patients, CT images could be fused with the EA-map. The alignment error was 2.16 ± 0.35 mm. In 15/15 (100%) patients, CT added relevant anatomical information regarding the course of the esophagus or the pulmonary veins before LA-ablation. CT added useful information in only 3/8 (37.5%) of patients undergoing right atrial cavotricuspid isthmus ablation.

Conclusion

3D-navigation of RF-ablation catheters in the atria assisted by image fusion of multislice CT with EA-mapping data is feasible and accurate. CT added relevant anatomical information about the left atrium and the pulmonary veins before LA-ablation, CT also provided information about the course of the esophagus which might help to avoid thermal injury. CT image fusion might be of minor value before right atrial cavotricuspid isthmus catheter ablation.     

Clinical value of CT/MR-US fusion imaging for radiofrequency ablation of hepatic nodules

Objective

The aim of this study was to determine the registration error of an ultrasound (US) fusion imaging system during an ex vivo study and its clinical value for percutaneous radiofrequency ablation (pRFA) during an in vivo study.

Materials and methods

An ex vivo study was performed using 4 bovine livers and 66 sonographically invisible lead pellets. Real-time CT-US fusion imaging was applied to assist the targeting of pellets with needles in each liver; the 4 sessions were performed by either an experienced radiologist (R1, 3 sessions) or an inexperienced resident (R2, 1 session). The distance between the pellet target and needle was measured. An in vivo study was retrospectively performed with 51 nodules (42 HCCs and 9 metastases; mean diameter, 16 mm) of 37 patients. Fusion imaging was used to create a sufficient safety margin (>5 mm) during pRFA in 24 nodules (group 1), accurately target 21 nodules obscured in the US images (group 2) and precisely identify 6 nodules surrounded by similar looking nodules (group 3). Image fusion was achieved using MR and CT images in 16 and 21 patients, respectively. The reablation rate, 1-year local recurrence rate and complications were assessed.

Results

In the ex vivo study, the mean target–needle distances were 2.7 mm ± 1.9 mm (R1) and 3.1 ± 3.3 mm (R2) (p > 0.05). In the in vivo study, the reablation rates in groups 1–3 were 13%, 19% and 0%, respectively. At 1 year, the local recurrence rate was 11.8% (6/51). In our assessment of complications, one bile duct injury was observed.

Conclusion

US fusion imaging system has an acceptable registration error and can be an efficacious tool for overcoming the major limitations of US-guided pRFA.     

Role of baseline nodule density and changes in density and nodule features in the discrimination between benign and malignant solid indeterminate pulmonary nodules

Purpose

To retrospectively evaluate whether baseline nodule density or changes in density or nodule features could be used to discriminate between benign and malignant solid indeterminate nodules.

Materials and methods

Solid indeterminate nodules between 50 and 500 mm³ (4.6–9.8 mm) were assessed at 3 and 12 months after baseline lung cancer screening (NELSON study). Nodules were classified based on morphology (spherical or non-spherical), shape (round, polygonal or irregular) and margin (smooth, lobulated, spiculated or irregular). The mean CT density of the nodule was automatically generated in Hounsfield units (HU) by the Lungcare^© software.

Results

From April 2004 to July 2006, 7310 participants underwent baseline screening. In 312 participants 372 solid purely intra-parenchymal nodules were found. Of them, 16 (4%) were malignant. Benign nodules were 82.8 mm³ (5.4 mm) and malignant nodules 274.5 mm³ (8.1 mm) (p = 0.000). Baseline CT density for benign nodules was 42.7 HU and for malignant nodules −2.2 HU (p = ns). The median change in density for benign nodules was −0.1 HU and for malignant nodules 12.8 HU (p < 0.05). Compared to benign nodules, malignant nodules were more often non-spherical, irregular, lobulated or spiculated at baseline, 3-month and 1-year follow-up (p < 0.0001). In the majority of the benign and malignant nodules there was no change in morphology, shape and margin during 1 year of follow-up (p = ns).

Conclusion

Baseline nodule density and changes in nodule features cannot be used to discriminate between benign and malignant solid indeterminate pulmonary nodules, but an increase in density is suggestive for malignancy and requires a shorter follow-up or a biopsy.     

Limited value of shape, margin and CT density in the discrimination between benign and malignant screen detected solid pulmonary nodules of the NELSON trial

Purpose

To evaluate prospectively the value of size, shape, margin and density in discriminating between benign and malignant CT screen detected solid non-calcified pulmonary nodules.

Material and methods

This study was institutional review board approved. For this study 405 participants of the NELSON lung cancer screening trial with 469 indeterminate or potentially malignant solid pulmonary nodules (>50 mm³) were selected. The nodules were classified based on size, shape (round, polygonal, irregular) and margin (smooth, lobulated, spiculated). Mean nodule density and nodule volume were automatically generated by software. Analyses were performed by univariate and multivariate logistic regression. Results were presented as likelihood ratios (LR) with 95% confidence intervals (CI). Receiver operating characteristic analysis was performed for mean density as predictor for lung cancer.

Results

Of the 469 nodules, 387 (83%) were between 50 and 500 mm³, 82 (17%) >500 mm³, 59 (13%) malignant, 410 (87%) benign. The median size of the nodules was 103 mm³ (range 50–5486 mm³). In multivariate analysis lobulated nodules had LR of 11 compared to smooth; spiculated nodules a LR of 7 compared to smooth; irregular nodules a LR of 6 compared to round and polygonal; volume a LR of 3. The mean nodule CT density did not predict the presence of lung cancer (AUC 0.37, 95% CI 0.32–0.43).

Conclusion

In solid non-calcified nodules larger than 50 mm³, size and to a lesser extent a lobulated or spiculated margin and irregular shape increased the likelihood that a nodule was malignant. Nodule density had no discriminative power.     

Imaging findings of liver resection using a bipolar radiofrequency electrosurgical device--initial observations

Objective

To assess contrast-enhanced US (CEUS), computed tomography (CT) and magnetic resonance (MR) imaging findings and serial changes of the treated area at follow-up in patients who underwent liver resection using a bipolar radiofrequency electrosurgical device.

Methods

Imaging findings of 27 patients with resected hepatocellular carcinomas (HCCs) (n = 24) and metastases (n = 3) (mean size: 2.6 cm), were retrospectively evaluated. Two readers assessed: the (a) presence, (b) thickness, (c) shape and (d) echogenicity (CEUS)/attenuation (CT)/signal intensity (MR imaging) at coagulated site and the (e) presence of residual tumor of the bipolar radiofrequency electrosurgical device resection margin.

Results

Follow-up was performed with either CT (n = 20) or MR imaging (n = 7) and repeated in 16 patients with CT (n = 7), MR imaging (n = 4), or both techniques (n = 5). Four patients also had a single CEUS examination. At first imaging follow-up a peripheral halo was depicted at resection site (100%). A fluid collection within the surgical area was found in 67% of patients. During the following imaging examinations a progressive involution of both findings was observed, respectively, in 81% and 62% of patients. Viable tissue was detected in three patients (11%).

Conclusions

After liver resection with bipolar radiofrequency electrosurgical device successfully ablated tumor is demonstrated at imaging by an unenhancing partial linear peripheral halo, in most cases, surrounding a fluid collection reducing in size during follow-up.     

Comparison of imaging characteristics between hepatic benign regenerative nodules and hepatocellular carcinomas associated with Budd-Chiari syndrome by contrast enhanced ultrasound

Purpose

To compare different imaging characteristics between hepatic benign regenerative nodules and hepatocellular carcinomas (HCCs) associated with Budd–Chiari syndrome (BCS) by contrast enhanced ultrasound (CEUS).

Materials and methods

A total of 32 chronic BCS patients (mean age, 42 years; age range, 18–59 years) with hepatic nodules who underwent CEUS were retrospectively studied. All patients had no the history of viral hepatitis. There were 23 patients with benign regenerative nodules (22 ± 9 mm; range, 8–42 mm) and 9 patients with HCCs (63 ± 21 mm; range, 26–90 mm). Lesion characteristics, including number, size, vascularization on color Doppler flow imaging, echogenicity, peripheral hypoechoic rim, and enhancement patterns in arterial, portal, and late phases on CEUS, were analyzed.

Results

There were significant differences in number and size of the lesions between two groups. No significant differences were observed in vascularity, echogenicity, and peripheral hypoechoic rim. Overall, there were significant differences in enhancement patterns in arterial, portal, and late phases between them on CEUS. Of 23 patients with benign regenerative nodules, 16 (70%) were center-to-periphery hyperenhanced and 7 patients (30%) were homogeneously hyperenhanced in arterial phase; the majority were homogeneously hyperenhanced in portal and late phases. Of 9 patients with HCCs, 8 (89%) were heterogeneously hyperenhanced in arterial phase and most of them were hypoenhanced in portal and late phases.

Conclusion

CEUS imaging characteristics of benign regenerative nodules radically differ from that of HCCs in BCS patients.     

Comparative survival analysis in patients with pulmonary metastases from nasopharyngeal carcinoma treated with radiofrequency ablation

Purpose

The aim of this retrospective study was to evaluate technical efficacy and the impact of CT-guided pulmonary radiofrequency ablation (RFA) on survival in patients with pulmonary metastases from nasopharyngeal carcinoma (NPC).

Materials and methods

Between 2000 and 2009, 480 patients were pathologically or clinically confirmed pulmonary metastases from NPC. And ten included patients of them had a total of 23 pulmonary metastases treated with percutaneous RFA under the real-time CT fluoroscopy. Safety, local tumor progression, and survival were evaluated in our institutions. Matched-pair survival was compared using Kaplan–Meier analysis.

Results

A total of 25 ablations were performed to 23 pulmonary metastases in 13 RFA sessions. Pneumothorax requiring chest tube placement developed in 3 of 13 (23.1%) RFA sessions. The median metastatic overall survival was 36.1 months for all the 480 NPC patients with pulmonary metastases. Furthermore, matched-pair analysis demonstrated patients with RFA treatment had a greater metastatic overall survival than patients without RFA treatment (77.1 months vs 32.4 months, log-rank test, p = 0.009). There were no statistically significant differences in the survival probability of patients with RFA treatment (n = 10) and surgical resection of pulmonary metastases (n = 27) (log-rank test, p = 0.75).

Conclusion

CT-guided pulmonary RFA is safe and offers a treatment alternative for local tumor control, providing promising survival in selected patients with pulmonary metastases from NPC.     

Local thermal ablation of renal cell carcinoma

Purpose

With evolving local thermal ablation technology, the clinical application of thermal ablation has been actively investigated in the treatment for renal cell carcinoma. We review the evolution and current status of radiofrequency ablation and microwave ablation for renal cell carcinoma.

Materials and methods

All articles published in English on radiofrequency ablation or microwave ablation as a treatment for renal cell carcinoma were identified with a MEDLINE^® and PubMed^® search from 1990 to 2010.

Results

Local thermal ablation has several advantages, including keeping more normal renal units, relatively simple operation, easy tolerance, fewer complications, a shorter hospitalization and convalescence period. Long-term data has determined radiofrequency ablation is responsible for poor surgical candidates with renal cell carcinoma, however, tumor size, location and shape might affect the efficacy of radiofrequency ablation. Microwave ablation can induce large ablation volumes and yield good local tumor control. Associated complications appear to be low.

Conclusions

Local ablative approaches seem to represent an attractive alternative to extirpative surgery for the treatment of small renal neoplasms in select patients. Potential developments include concepts to improve the accuracy and effectiveness of thermal ablation by improving the guiding, monitoring capabilities and detection capacity of multi-center lesions to provide at least equivalent cancer control to conventional surgery.     

Using low tube voltage (80kVp) quadruple phase liver CT for the detection of hepatocellular carcinoma: two-year experience and comparison with Gd-EOB-DTPA enhanced liver MRI

Purpose

To validate the diagnostic performance of quadruple phase low tube voltage liver CT through the comparison with Gd-EOB-DTPA enhanced liver MRI for the detection of HCC.

Materials and methods

Non-obese patients (38 men, eight women) with 68 HCCs underwent quadruple-phase CT at 16 MDCT (using low tube voltage, 80 kVp; moderately high tube current, 280 mAs) and Gd-EOB-DTPA-enhanced 3 T MRI. Three observers independently and randomly reviewed the CT and MR images on a tumor-by-tumor basis. The diagnostic accuracy of these techniques for detecting HCC was assessed using alternative free-response receiver operating characteristic analysis. Sensitivity and positive predictive values were evaluated. The mean effective doses for the low dose CT were also evaluated.

Results

The areas under the ROC curves were 0.963, 0.959, and 0.941 for low dose CT and 0.981, 0.982, and 0.976 for MRI. Differences in Az of the two techniques for each observer were not statistically significant (P > .05). Differences in sensitivity and positive predictive values between the two techniques for each observer were not also statistically significant: sensitivity (86.8%, 82.4%, 85.3% for CT and 95.6%, 94.1%, 91.2% for MRI) and positive predictive values (92.2%, 90.3%, 89.2% for CT and 92.9%, 92.8%, 92.5% for MRI). Six HCCs (8.8%) in five patients were observed only on hepatobiliary phase of MRI, and all were smaller than 1.5 cm. The mean effective dose for CT was approximately 10.2 mSv.

Conclusions

Quadruple-phase low-dose liver CT (80 kVp, 280 mAs) had relatively good diagnostic performance for detecting HCC in non-obese patients. Because no significant difference was observed between low-dose CT and MRI, the use of low-dose liver CT can be justified based on its reduced radiation effects.     

Central lower attenuating lesion in the ablation zone on immediate follow-up CT after percutaneous radiofrequency ablation for hepatocellular carcinoma: Incidence and clinical significance

Purpose

The purpose of this study was to evaluate the incidence of central lower attenuating (CLA) lesion in the ablation zone seen on immediate follow-up CT images after percutaneous radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC), and the correlation of CLA lesions and local tumor progression (LTP).

Subjects and methods

The study group included 146 patients with 167 ablation zones that had undergone follow-up CT examinations for more than 12 months after percutaneous RFA. CLA lesions corresponding to index tumors and ablative margins (safety margins) were evaluated in the ablation zones seen on immediate follow-up CT including coronal and sagittal multiplanar reformatted (MPR) images with narrow window width settings.

Results

CLA lesions were depicted on 48 of 167 ablation zones (28.7%) on immediate follow-up CT images. Among the 48 ablation zones with CLA lesions, 27 (56.3%, 27/48) had ablative margins on all three of the orthogonal MPR images and they showed no LTP (0%) on follow-up CT examinations. Three of the ablation zones with CLA lesions (6.3%, 3/48) having an ablative margin on one plane only also showed no LTP (0%). LTP was observed in 2 of 18 ablation zones (11.1%) that had CLA lesions without ablative margins on all three planes. In the remaining 119 ablation zones without CLA lesions, 5 (4.2%, 5/119) showed LTP.

Conclusion

CLA lesions in ablation zones were occasionally (28.7%) seen on immediate follow-up CT images after RFA for HCCs. The presence of CLA lesions with ablative margins might be a negative predictor of LTP.     

Imaging Features of Radiofrequency Ablation with Heat-Deployed Liposomal Doxorubicin in Hepatic Tumors

Introduction

The imaging features of unresectable hepatic malignancies in patients who underwent radiofrequency ablation (RFA) in combination with lyso-thermosensitive liposomal doxorubicin (LTLD) were determined.

Materials and Methods

A phase I dose escalation study combining RFA with LTLD was performed with peri- and post- procedural CT and MRI. Imaging features were analyzed and measured in terms of ablative zone size and surrounding penumbra size. The dynamic imaging appearance was described qualitatively immediately following the procedure and at 1-month follow-up. The control group receiving liver RFA without LTLD was compared to the study group in terms of imaging features and post-ablative zone size dynamics at follow-up.

Results

Post-treatment scans of hepatic lesions treated with RFA and LTLD have distinctive imaging characteristics when compared to those treated with RFA alone. The addition of LTLD resulted in a regular or smooth enhancing rim on T1W MRI which often correlated with increased attenuation on CT. The LTLD-treated ablation zones were stable or enlarged at follow-up four weeks later in 69 % of study subjects as opposed to conventional RFA where the ablation zone underwent involution compared to imaging acquired immediately after the procedure.

Conclusion

The imaging features following RFA with LTLD were different from those after standard RFA and can mimic residual or recurrent tumor. Knowledge of the subtle findings between the two groups can help avoid misinterpretation and proper identification of treatment failure in this setting. Increased size of the LTLD-treated ablation zone after RFA suggests the ongoing drug-induced biological effects.

     

Uterine artery embolization (UAE) for diffuse leiomyomatosis of the uterus: clinical and imaging results

Purpose

The aim of the current study was to evaluate the efficacy of uterine artery embolization (UAE) in the management of diffuse uterine leiomyomatosis with mid-term follow-up.

Materials and methods

All patients who underwent UAE between 2008 and 2010 for symptomatic fibroids were analyzed. Among 360 cases, a total of 7 patients with diffuse uterine leiomyomatosis diagnosed based on MRI were included in this retrospective study. Patient ages ranged from 29 to 38 (mean 32.7) years. The median follow-up period was 16 (range; 6–31) months. The embolic agent was non-spherical polyvinyl alcohol particles. All patients underwent follow-up MRI at 3 months after UAE. Uterine volumes were calculated using MRI. Menorrhagia symptom changes were assessed at mid-term follow-up.

Results

There were no technical failures to catheterize the uterine artery and no adverse events requiring therapy after UAE. Contrast-enhanced MRI showed complete necrosis of the leiomyomatous nodules in 5 patients (71%) 3 months after embolization. Two patients (28%) showed mostly leiomyomatous nodules that were necrotized, some of which were still viable. All 7 patients with menorrhagia had improvement of symptoms at the mid-term follow-up. The initial mean uterine volume was 601.30 ± 533.92 cm³ and was decreased to a mean of 278.81 ± 202.70 cm³ at 3 months follow-up, for a mean uterus volume reduction rate of 50.1% (p < 0.05). One patient became pregnant 5 months after UAE treatment.

Conclusion

UAE was a highly effective treatment for diffuse uterine leiomyomatosis with mid-term durability and may be a valuable alternative to hysterectomy.