Microwave Ablation of the Lung in a Porcine Model: Vessel Diameter Predicts Pulmonary Artery Occlusion.

PURPOSE: To determine the size of pulmonary artery (PA) at risk for occlusion during percutaneous microwave ablation and to assess the effect of vessel diameter, number, and patency, on ablation zone volume. MATERIALS AND METHODS: Computed tomography (CT) fluoroscopy-guided percutaneous microwave ablations were performed in 8 pigs under general anesthesia. All ablations were performed at 65 W for 5 min with a single 17-gauge antenna positioned in the central third of the lungs. A CT pulmonary angiogram was performed immediately after the ablations. The maximum diameter, number and patency of PA branches within each ablation zone were recorded. Ablation volumes were measured at gross dissection and with CT. Student's t test was used to compare ablation zone volumes among groups. RESULTS: Twenty-one pulmonary ablations were performed. Six of the ablation zones (29%) contained at least 1 occluded PA branch. The mean diameter of the occluded PA branches in the ablation zones (2.4 mm; range, 2.0-2.8 mm) was significantly smaller than non-occluded PA branches (3.7 mm; range: 2.1-6.9 mm; p = 0.009). No PA branches ≥3 mm in size were occluded. There was no significant difference in volume of gross ablation zones that contained occluded versus non-occluded PAs (p = 0.42), one versus multiple PAs (p = 0.71), or PAs <3 mm versus ≥3 mm in diameter (p = 0.44). CONCLUSIONS: PAs ≥3 mm in size have a low risk for iatrogenic occlusion during percutaneous microwave ablation. The presence of multiple adjacent PA branches, an occluded PA branch, and a vessel diameter ≥3 mm within the ablation zone had no observed effect on ablation zone volume.

Safety and Efficacy of Percutaneous Microwave Hepatic Ablation Near the Heart.

PURPOSE: To evaluate safety and efficacy of percutaneous hepatic microwave (MW) ablation performed near the heart. MATERIALS AND METHODS: This study reviewed 118 consecutive peripheral (ablation zone margins within 5 mm of liver capsule) percutaneous MW hepatic ablations performed between June 2010 and August 2015. Ablation zones of 27 tumors (22.8%) extended to ≤ 5 mm from myocardium, and these ablations comprised the study group; the remaining ablations formed the control group. The study cohort included 14 men and 10 women (mean age, 59 y) with 16 hepatocellular carcinomas, 9 metastases, and 2 hemangiomas. Periprocedural imaging was used to evaluate tumor size and distance from the heart, ablation zone size, and complications. Mean tumor size and distance to myocardium were 2.6 cm ± 1.7 and 1.1 cm ± 1.1, respectively. The electronic medical record was used to retrospectively assess local tumor progression (LTP) and electrocardiogram and hemodynamic alterations during and after ablation. Statistical analysis was performed with Fisher exact test and t test. RESULTS: Median follow-up was 13.6 months (range, 1.2-38.7 months). No arrhythmias occurred during or after ablation in the follow-up period (0/27). There was no difference between groups in frequency of alterations in periprocedural blood pressure (25.9% vs 29.6%, p=0.81) or heart rate (18.5% vs 24.2%, P = .61) or rate of LTP (12.0% vs 10.8%, P = 1.0). CONCLUSIONS: Percutaneous MW ablation near the heart may be safe and effective, without increased risk of cardiac complications and with similar rates of LTP, compared with a control group of peripheral liver ablations.

Pulmonary Microwave Ablation Near the Heart: Antenna Positioning Can Mitigate Cardiac Complications in a Porcine Model.

Purpose To determine how close to the heart pulmonary microwave ablation can be performed without causing cardiac tissue injury or significant arrhythmia. Materials and Methods The study was performed with approval from the institutional animal care and use committee. Computed tomographic fluoroscopically guided microwave ablation of the lung was performed in 12 swine. Antennas were randomized to either parallel (180° ± 20°) or perpendicular (90° ± 20°) orientation relative to the heart surface and to distances of 0-10 mm from the heart. Ablations were performed at 65 W for 5 minutes or until a significant arrhythmia (asystole, heart block, bradycardia, supraventricular or ventricular tachycardia) developed. Heart tissue was evaluated with vital staining and histologic examination. Data were analyzed with mixed effects logistic regression, receiver operating characteristic curves, and the Fisher exact test. Results Thirty-four pulmonary microwave ablations were performed with the antenna a median distance of 4 mm from the heart in both perpendicular (n = 17) and parallel (n = 17) orientation. Significant arrhythmias developed during six (18%) ablations. Cardiac tissue injury occurred with 17 ablations (50%). Risk of arrhythmia and tissue injury decreased with increasing antenna distance from the heart with both antenna orientations. No cardiac complication occurred with a distance of greater than or equal to 4.4 mm from the heart. The ablation zone extended to the pleural surface adjacent to the heart in 71% of parallel and 17% of perpendicular ablations performed 5-10 mm from the heart. Conclusion Microwave lung ablations performed more than or equal to 5 mm from the heart were associated with a low risk of cardiac complications. © RSNA, 2016.

Percutaneous biopsy in the abdomen and pelvis: a step-by-step approach.

Percutaneous abdominal biopsies provide referring physicians with valuable diagnostic and prognostic information that guides patient care. All biopsy procedures follow a similar process that begins with the preprocedure evaluation of the patient and ends with the postprocedure management of the patient. In this review, a step-by-step approach to both routine and challenging abdominal biopsies is covered with an emphasis on the differences in biopsy devices and imaging guidance modalities. Adjunctive techniques that may facilitate accessing a lesion in a difficult location or reduce procedure risk are described. An understanding of these concepts will help maintain the favorable safety profile and high diagnostic yield associated with percutaneous biopsies.

Unreported vertebral body compression fractures at abdominal multidetector CT.

PURPOSE: To retrospectively assess the prevalence and clinical outcomes of unreported vertebral compression fractures at abdominal computed tomography (CT). MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval; the need for informed consent was waived for this retrospective analysis. A total of 2041 consecutive adult patients (1640 women, 401 men; age range, 19-94 years) underwent both abdominal multidetector CT and dual-energy x-ray absorptiometry (DXA) within 6 months of each other between 2000 and 2007, before sagittal CT reconstructions were obtained routinely. Transverse (axial) and retrospective sagittal multidetector CT reconstructions were reviewed for the presence of moderate or severe vertebral body compression fractures of the lower thoracic and lumbar spine by using the Genant visual semiquantitative method. Twenty-six patients were excluded for evidence of pathologic fracture or for technical factors limiting compression fracture detection. Electronic medical records were reviewed for patients with moderate or severe compression fractures to determine whether the fracture was reported at prospective CT interpretation, was known previously, or was diagnosed subsequently. Correlation was made with central DXA T scores. Statistical analysis was performed with the Student t test and Fisher exact test. RESULTS: At least one moderate or severe vertebral body compression fracture was identified retrospectively at CT in 97 patients (mean age, 70.8 years). Fractures involved one level in 67 and multiple levels in 30 patients, for a total of 141 fractures. In 81 (84%) patients, prospective CT diagnosis was not made. Patients in whom fractures were reported prospectively were significantly older and were more likely to have a severe compression fracture (P < .05). In 52 (64%) patients with an unreported fracture, the vertebral compression fracture was not known clinically. In 18 patients, subsequent diagnosis of a compression fracture was determined by means of another imaging study (median interval, 7 months). At DXA, 39 (48%) of 81 patients with unreported vertebral body compression fractures had a nonosteoporotic T score (greater than -2.5). CONCLUSION: Most clinically important vertebral body compression fractures in nontrauma patients at risk for low bone mineral density may go unreported at abdominal multidetector CT if sagittal reconstructions are not routinely evaluated.