Tae Wook Kang

Diffusion-weighted imaging of the prostate at 3 T for differentiation of malignant and benign tissue in transition and peripheral zones: Preliminary results

Objective: To evaluate prospectively the use of apparent diffusion coefficients (ADCs) for the differentiation of malignant and benign tissue in the transition (TZ) and peripheral (PZ) zones of the prostate diffusion-weighted imaging (DWI) at 3 T magnetic resonance imaging (MRI) using a phased-array coil. Methods: The DWI at 3-T MRI was performed on a total of 35 patients before radical prostatectomy. A single-shot echo-planar imaging DWI technique with b = 0 and b = 1000 s/mm2 was used. The ADC values were measured in both benign and malignant tissues in the PZ and TZ using regions of interest. Differences between PZ and TZ ADC values were estimated using a paired Student t test. Presumed ADC cutoff values in the PZ and TZ for the diagnosis of cancer were assessed by receiver operating characteristic analysis. Results: The ADC values of malignant tissues were significantly lower than those of benign tissues in the PZ and TZ (P < 0.001; 1.32 ± 0.24 × 10−3 mm2/s vs 1.97 ± 0.25 × 10−3 mm2/s, and 1.37 ± 0.29 × 10−3 mm2/s vs 1.79 ± 0.19 × 10−3 mm2/s, respectively). For tumor diagnosis, cutoff values of 1.67 × 10−3 mm2/s (PZ) and 1.61 × 10−3 mm2/s (TZ) resulted in sensitivities and specificities of 94% and 91% and 90% and 84%, respectively. Conclusions: The DWI of the prostate at 3T MRI using a phased-array coil was useful for the differentiation of malignant and benign tissues in the TZ and PZ.

Percutaneous Radiofrequency Ablation for the Hepatocellular Carcinoma Abutting the Diaphragm: Assessment of Safety and Therapeutic Efficacy

Objective To assess the safety and therapeutic efficacy of a percutaneous radiofrequency (RF) ablation for the hepatocellular carcinoma (HCC) abutting the diaphragm. Materials and Methods We retrospectively assessed 80 patients who underwent a percutaneous RF ablation for a single nodular (< 4 cm) HCC over the last four years. Each patient underwent an ultrasound-guided RF ablation using internally cooled electrodes for the first-line treatment. We divided patients into two subgroups based on whether the index tumor was abutting (less than 5 mm) the diaphragm or not: group A (abutting; n = 31) versus group B (non-abutting; n = 49). We compared the two subgroups for complications and therapeutic efficacy using image and the review of medical records. The statistical assessment included an independent t-test, Fishers exact test, and chi-square test. Results The assessment of the diaphragmatic swelling at CT immediately following the procedure was more severe in group A than group B (mean thickness change:1.44 vs. 0.46 mm, p = 0.00). Further, right shoulder pain was more common in group A than B (p = 0.01). Although minor complications (hemothorax 1 case, pleural effusion 1 case) were noted only in group A, no major thoracic complication occurred in either group. The technical success rate was lower in group A than group B (84% vs. 98%, p = 0.03). As well, the primary and secondary technique effectiveness rates in group A and group B were 90% versus 98% (p = 0.29) and 79% versus 91% (p = 0.25), respectively. The local tumor progression rate was higher in group A than in group B (29% vs. 6%, p = 0.02). Conclusion We found that the percutaneous RF ablation for the HCC abutting the diaphragm is a safe procedure without major complications. However, it is less effective with regard to technical success and local tumor control.

Recent Advances in Tumor Ablation for Hepatocellular Carcinoma

Image-guided tumor ablation for early stage hepatocellular carcinoma (HCC) is an accepted non-surgical treatment that provides excellent local tumor control and favorable survival benefit. This review summarizes the recent advances in tumor ablation for HCC. Diagnostic imaging and molecular biology of HCC has recently undergone marked improvements. Second-generation ultrasonography (US) contrast agents, new computed tomography (CT) techniques, and liver-specific contrast agents for magnetic resonance imaging (MRI) have enabled the early detection of smaller and inconspicuous HCC lesions. Various imaging-guidance tools that incorporate imaging-fusion between real-time US and CT/MRI, that are now common for percutaneous tumor ablation, have increased operator confidence in the accurate targeting of technically difficult tumors. In addition to radiofrequency ablation (RFA), various therapeutic modalities including microwave ablation, irreversible electroporation, and high-intensity focused ultrasound ablation have attracted attention as alternative energy sources for effective locoregional treatment of HCC. In addition, combined treatment with RFA and chemoembolization or molecular agents may be able to overcome the limitation of advanced or large tumors. Finally, understanding of the biological mechanisms and advances in therapy associated with tumor ablation will be important for successful tumor control. All these advances in tumor ablation for HCC will result in significant improvement in the prognosis of HCC patients. In this review, we primarily focus on recent advances in molecular tumor biology, diagnosis, imaging-guidance tools, and therapeutic modalities, and refer to the current status and future perspectives for tumor ablation for HCC.

Small Hepatocellular Carcinoma: Radiofrequency Ablation versus Nonanatomic Resection—Propensity Score Analyses of Long-term Outcomes

PURPOSE To compare radiofrequency (RF) ablation with nonanatomic resection (NAR) as first-line treatment in patients with a single Barcelona Clinic Liver Cancer (BCLC) stage 0 or A hepatocellular carcinoma (HCC) and to evaluate the long-term outcomes of both therapies. MATERIALS AND METHODS This retrospective study was approved by the institutional review board. The requirement for informed consent was waived. Data were reviewed from 580 patients with HCCs measuring 3 cm or smaller (BCLC stage 0 or A) who underwent ultrasonographically (US) guided percutaneous RF ablation (n = 438) or NAR (n = 142) as a first-line treatment. Local tumor progression, intrahepatic distant recurrence, disease-free survival, and overall survival rates were analyzed by using propensity score matching to compare therapeutic efficacy. In addition, major complications and length of postoperative hospital stay were compared. RESULTS Before propensity score matching (n = 580), the 5-year cumulative rates of local tumor progression for RF ablation and NAR (20.9% vs 12.7%, respectively; P = .093) and overall survival rates (85.5% vs 90.9%, respectively; P = .194) were comparable, while the 5-year cumulative intrahepatic distant recurrence rates (62.7% vs 36.6%, respectively; P < .001) and disease-free survival rates (31.7% vs 61.1%, respectively; P < .001) in the NAR group were significantly better than those in the RF ablation group. After matching (n = 198), there were no significant differences in therapeutic outcomes between the RF ablation and NAR groups, including 5-year cumulative intrahepatic distant recurrence (47.0% vs 40.2%, respectively; P = .240) and disease-free survival rates (48.9% vs 54.4%, respectively; P = .201). RF ablation was superior to NAR for major complication rates and length of postoperative hospital stay (P < .001). CONCLUSION In patients with one BCLC stage 0 or A (≤ 3 cm) HCC who received RF ablation or NAR as first-line treatment, there were no significant differences in long-term therapeutic outcomes; however, RF ablation was associated with fewer major complications and a shorter hospital stay after treatment.

Morphological and functional MRI, MRS, perfusion and diffusion changes after radiosurgery of brain metastasis

Radiosurgery is a noninvasive procedure where spatially accurate and highly conformal doses of radiation are targeted at brain lesions with an ablative intent. Recently, radiosurgery has been established as an effective technique for local treatment of brain metastasis. After radiosurgery, magnetic resonance (MR) imaging plays an important role in the assessment of the therapeutic response and of any complications. The therapeutic approach depends on the imaging findings obtained after radiosurgery, which have a role in the decision making to perform additional invasive modalities (repeat resection, biopsy) to obtain a definite diagnosis and to improve the survival of patients. Conventional MR imaging findings are mainly based on morphological alterations of tumors. However, there are variable imaging findings of radiation-induced changes including radiation necrosis in the brain. Radiologists are sometimes confused by radiation-induced injuries, including radiation necrosis, that are seen on conventional MR imaging. The pattern of abnormal enhancement on follow-up conventional MR imaging closely mimics that of a recurrent brain metastasis. So, classifying newly developed abnormal enhancing lesions in follow-up of treated brain metastasis with correct diagnosis is one of the key goals in neuro-oncologic imaging. To overcome limitations of the use of morphology-based conventional MR imaging, several physiological-based functional MR imaging methods have been used, namely diffusion-weighted imaging, perfusion MR imaging, and proton MR spectroscopy, for the detection of hemodynamic, metabolic, and cellular alterations. These imaging modalities provide additional information to allow clinicians to make proper decisions regarding patient treatment.

Radiofrequency Ablation for Hepatocellular Carcinoma Abutting the Diaphragm: Comparison of Effects of Thermal Protection and Therapeutic Efficacy

OBJECTIVE This study was designed to assess the effect of artificial ascites on thermal protection of the diaphragm and the therapeutic efficacy of this technique during percutaneous radiofrequency ablation for hepatocellular carcinoma abutting the diaphragm. MATERIALS AND METHODS A total of 44 patients with a single nodular hepatocellular carcinoma (< 4 cm; mean, 2.2 cm) that abutted the diaphragm were treated with ultrasound-guided percutaneous radiofrequency ablation as first-line treatment. The patients were divided into two groups: a group who received artificial ascites (n = 20) and a control group (n = 24). We compared the two groups in an assessment for change in diaphragmatic thickness, right shoulder pain, and transient lung injury as indicators of thermal injury to the diaphragm. We evaluated therapeutic efficacy with follow-up CT. RESULTS Swelling of diaphragm at immediate follow-up CT was more severe in the control group (mean change in thickness, 0.56 mm versus 1.55 mm; p = 0.01). Right shoulder pain (n = 1 versus n = 7) and transient lung injury (n = 0 versus n = 6) occurred statistically significantly more often in the control group than the artificial ascites group, but pleural effusion did not (n = 13 versus n = 1). The technical success rate was higher in the artificial ascites group (100% versus 79%, p = 0.06). There was no significant difference in effectiveness rate of the primary technique (100% versus 92%, p = 0.49) or rate of local tumor progression (20% versus 30%, p = 0.47). CONCLUSION The use of artificial ascites for percutaneous radiofrequency ablation of hepatocellular carcinoma abutting the diaphragm had a significant effect on thermal protection of the diaphragm but not on therapeutic efficacy.

Perivascular versus Nonperivascular Small HCC Treated with Percutaneous RF Ablation: Retrospective Comparison of Long-term Therapeutic Outcomes

PURPOSE To compare the long-term therapeutic outcomes of radiofrequency (RF) ablation for small perivascular hepatocellular carcinoma (HCC) and nonperivascular HCC. MATERIALS AND METHODS This retrospective study was approved by the institutional review board. Between December 2004 and April 2008, 241 patients (175 men and 66 women; age range, 32-82 years) with a single early-stage HCC that was 3 cm or smaller in the greatest dimension underwent ultrasonography-guided percutaneous RF ablation as a first-line treatment. The patients were divided into two groups according to the presence or absence of contacting hepatic vessels that were 3 mm or larger in axial diameter: a group with perivascular HCC (n = 58) and a group with nonperivascular HCC (n = 183). Cumulative local tumor progression, disease-free and long-term survival rates, and prognostic factors were assessed by using Cox proportional hazard models with Bonferroni correction. RESULTS The overall median follow-up period was 58 months (range, 13-92 months). The cumulative local tumor progression rates were 10%, 16%, and 26% at 1, 3, and 5 years, respectively, in the perivascular group, and 6.7%, 15.5%, and 20.5% in the nonperivascular group; the differences were not significant (P = .323). The corresponding disease-free survival rates were 79%, 41%, and 29% in the perivascular group and 71.3%, 38.7%, and 26.0% in the nonperivascular group, with no significant difference (P = .689). The corresponding overall survival rates were 100%, 94%, and 82% in the perivascular group and 100%, 88.4%, and 73.9% in the nonperivascular group, also without significant difference (P = .267). There was no significant prognostic factor for local tumor progression, whereas extrahepatic and intrahepatic distant recurrences were significant prognostic factors for overall survival in multivariable analysis. CONCLUSION The long-term therapeutic outcomes of RF ablation as first-line treatment for small perivascular HCC were similar to those for nonperivascular HCC.

Radiofrequency ablation of very-early-stage hepatocellular carcinoma inconspicuous on fusion imaging with B-mode US: value of fusion imaging with contrast-enhanced US

Background/Aims To determine the value of fusion imaging with contrast-enhanced ultrasonography (CEUS) and computed tomography (CT)/magnetic resonance (MR) images for percutaneous radiofrequency ablation (RFA) of very-early-stage hepatocellular carcinomas (HCCs) that are inconspicuous on fusion imaging with B-mode ultrasound (US) and CT/MR images. Methods This retrospective study was approved by our institutional review board and the requirement for informed consent was waived. Fusion imaging with CEUS using Sonazoid contrast agent and CT/MR imaging was performed on HCCs (<2 cm) that were inconspicuous on fusion imaging with B-mode US. We evaluated the number of cases that became conspicuous on fusion imaging with CEUS. Percutaneous RFA was performed under the guidance of fusion imaging with CEUS. Technical success and major complication rates were assessed. Results In total, 30 patients with 30 HCCs (mean, 1.2 cm; range, 0.6-1.7 cm) were included, among which 25 (83.3%) became conspicuous on fusion imaging with CEUS at the time of the planning US and/or RFA procedure. Of those 25 HCCs, RFA was considered feasible for 23 (92.0%), which were thus treated. The technical success and major complication rates were 91.3% (21/23) and 4.3% (1/23), respectively. Conclusions Fusion imaging with CEUS and CT/MR imaging is highly effective for percutaneous RFA of very-early-stage HCCs inconspicuous on fusion imaging with B-mode US and CT/MR imaging.

Aggressive Intrasegmental Recurrence of Hepatocellular Carcinoma after Radiofrequency Ablation: Risk Factors and Clinical Significance

PURPOSE To evaluate the frequency, risk factors, and clinical significance of aggressive intrasegmental recurrence (AIR) found after radiofrequency (RF) ablation for hepatocellular carcinoma (HCC). MATERIALS AND METHODS Institutional review board approval was obtained for this retrospective study. Between March 2005 and December 2010, 539 patients (414 men, 125 women; mean age, 57.91 years; age range, 30-82 years) underwent ultrasonography-guided percutaneous RF ablation as a first-line treatment for a single HCC classified as Barcelona Clinic Liver Cancer (BCLC) stage 0 or A. AIR of HCC was defined as (a) initial tumor recurrence with disease-free status at least 6 months after initial RF ablation and (b) the simultaneous development of multiple nodular (at least three) or infiltrative tumor recurrence in the treated segment. Patients were stratified into two groups: those with AIR (n = 20) and those without AIR (n = 519) during follow-up. Risk factors for AIR were assessed with logistic regression analysis, and risk factors for long-term overall survival were assessed with time-dependent Cox proportional hazard models. RESULTS In a median follow-up period of 49 months (range, 6-95 months), AIR was observed in 3.7% of the patients (20 of 539 patients), with the frequency increasing to 15% in the subgroup with periportal HCC (11 of 72 patients). AIRs manifested as either multiple nodular type (n = 14, BCLC stage A or B) or diffusely infiltrative type with tumor thrombus formation (n = 6, BCLC stage C). At multivariate analysis, periportal tumor location and younger patient age were significant risk factors for AIR. The presence of AIR during the follow-up period has a significant effect on the overall survival rate (hazard ratio = 5.72, P = .002). CONCLUSION The overall frequency of AIR after RF ablation for HCC was low, with periportal location and patient age showing a significant relationship to the development of AIR. The occurrence of AIR had an adverse effect on overall survival rate.

Fusion imaging-guided percutaneous biopsy of focal hepatic lesions with poor conspicuity on conventional sonography.

The purpose of this study was to evaluate the effectiveness of real‐time fusion imaging (sonography combined with computed tomography or magnetic resonance imaging) for percutaneous sonographically guided biopsy of focal hepatic lesions with poor sonographic conspicuity.