Masami Toyoshima

Radiofrequency Ablation in a Porcine Lung Model: Correlation Between CT and Histopathologic Findings

OBJECTIVE The objective of our study was to investigate the time course changes of the ablated lesion after radiofrequency ablation in the porcine lung and the correlation between CT and histopathologic findings. CONCLUSION Ground-glass attenuation on CT led to overestimation of the size of necrotic lesions. The layered structural findings on CT were consistent with the histopathologic findings. Although CT findings reflect the histopathologic findings, attention should be paid to the dissociation of ablated lesions and high-density areas in clinical interpretation of CT images.

Percutaneous radiofrequency ablation of lung neoplasms: a minimally invasive strategy for inoperable patients1

Treatment of patients with lung neoplasms, who often suffer from additional medical problems with attendant surgical risk, is controversial. No standard treatment exists, so innovative treatments should be developed to manage patients with this clinical presentation. Radiofrequency (RF) ablation therapy has recently attracted attention with other minimally invasive strategies to treat malignant disease. Although satisfactory clinical results have been reported using this method for liver tumors, only a few reports have been published regarding RF ablation therapy for human lung neoplasms, and its clinical benefit has not been established. We carried out a pilot study on the clinical feasibility and safety of RF ablation therapy for lung neoplasms.

Fluorine-18-fluorodeoxyglucose positron emission tomography for assessment of patients with unresectable recurrent or metastatic lung cancers after CT-guided radiofrequency ablation: Preliminary results

ObjectivesWe compared the diagnostic value of fluorine-18-fiuorodeoxyglucose positron emission tomography (FDG-PET) with that of computed tomography (CT) following radiofrequency ablation (RFA) of inoperable recurrent or metastatic cancers in the lung.MethodsTwelve patients (9 males and 3 females; 5 had recurrent lung cancer and the other 7 had metastatic nodules from a variety of primary cancers) were treated by RFA for 17 pulmonary nodules. FDG-PET was performed before and 2 months after RFA, and the mean standardized uptake value (SUV) was calculated. The response evaluation was based on the percent reduction relative to the baseline and the absolute values of SUV on FDG-PET performed at 2 months after RFA. We compared the response evaluations made based on findings of FDG-PET and CT at 2 and ≥6 months (mean 10.2) after RFA.ResultsThe percent reduction in uptake at 2 months was significantly lower in nodules considered progressive (69.6± 18.6%) than nonprogressive disease (38.7 ± 12.5%; p < 0.01) based on CT findings at >6 months after RFA. The absolute SUV at 2 months was significantly higher in nodules considered progressive (2.61 ±0.75) than nonprogressive disease (1.05 ±0.67; p<0.01) based on CT findings at ≥6 months post-RFA.ConclusionAlthough our pilot study comprised few cases of various histopathological types of cancers in the lung, the results suggest that FDG-PET could predict regrowth on subsequent follow-up CT. Regrowth could be diagnosed earlier by FDG-PET than by CT, and nodules with residual uptake and with <60% reduction of uptake relative to baseline on FDG-PET at 2 months after ablation might require additional therapy.

Frequency and Risk Factors of Various Complications After Computed Tomography–Guided Radiofrequency Ablation of Lung Tumors

ObjectiveTo retrospectively determine the frequency and risk factors of various side effects and complications after percutaneous computed tomography–guided radiofrequency (RF) ablation of lung tumors.MethodsWe reviewed and analyzed records of 112 treatment sessions in 57 of our patients (45 men and 12 women) with unresectable lung tumors treated by ablation. Risk factors, including sex, age, tumor diameter, tumor location, history of surgery, presence of pulmonary emphysema, electrode gauge, array diameter, patient position, maximum power output, ablation time, and minimum impedance during ablation, were analyzed using univariate and multivariate analyses.ResultsTotal rates of side effects and minor and major complications occurred in 17%, 50%, and 8% of treatment sessions, respectively. Side effects, including pain during ablation (46% of sessions) and pleural effusion (13% of sessions), occurred with RF ablation. Minor complications, including pneumothorax not requiring chest tube drainage (30% of sessions), subcutaneous emphysema (16% of sessions), and hemoptysis (9% of sessions) also occurred after the procedure. Regarding major complications, three patients developed fever >38.5°C; three patients developed abscesses; two patients developed pneumothorax requiring chest tube insertion; and one patient had air embolism and was discharged without neurologic deficit. Univariate and multivariate analyses suggested that a lesion located ≤1 cm of the chest wall was significantly related to pain (p < 0.01, hazard index 5.76). Risk factors for pneumothorax increased significantly with previous pulmonary surgery (p < 0.05, hazard index 6.1) and presence of emphysema (p <0.01, hazard index 13.6).ConclusionThe total complication rate for all treatment sessions was 58%, and 25% of patients did not have any complications after RF ablation. Although major complications can occur, RF ablation of lung tumors can be considered a safe and minimally invasive procedure.

Radiofrequency Ablated Lesion in the Normal Porcine Lung: Long-Term Follow-Up with MRI and Pathology

PurposeTo evaluate the effectiveness of magnetic resonance imaging (MRI) in reflecting histopathologic changes after radiofrequency ablation (RFA) to the lung and to assess accurately the extent of tissue necrosis for evaluating untreated lesions.MethodsPercutaneous RFA was performed on 72 lung regions in 12 pigs under computed tomographic guidance. After performing MRI, the animals were divided into three experimental phases: in the acute phase, 4 pigs were killed immediately after the procedure; in the subacute phase, 4 pigs were killed at 1 week; and in the chronic phases, 2 pigs were killed at 4 and 8 weeks after the procedure, respectively. MRI–histopathologic correlation was performed.ResultsIn the acute phase, the inner zone showed hypointensity on T2-weighted images and isointensity on T1-weighted images, with a lack of enhancement on contrast-enhanced T1-weighted images, representing early changes in coagulative necrosis on histopathologic examination. The outer zone showed hyperintensity on T2-weighted images and isointensity on T1-weighted images, with ring-like enhancement on contrast-enhanced T1-weighted images. The histopathologic section showed alveolar fluid collections and congestion. In the subacute phase the MR zone pattern was essentially similar to that of the acute phase, but the ablated lesion showed extensive coagulative necrosis with a fibrovascular rim on histopathologic examination. In the chronic phase, there was no change in the zone pattern on MRI. The lesions showed gradual resorption of coagulative necrosis. The area of coagulative necrosis correlated closely with the histopathologic size (p < 0.05).ConclusionsMRI effectively visualized the histopathologic changes after RFA and accurately determined the extent of the necrotic lesion. MRI is potentially a useful modality for evaluating therapeutic efficacy after RFA to the lung.