Evaluation of the thermal sensitivity of porcine liver in CT-guided cryoablation: an initial study.

PURPOSE: To evaluate computed tomography (CT)-based thermometry in cryoablation, the thermal sensitivity of an ex-vivo porcine liver was determined in an initial study design. METHODS: The CT-guided cryoablation was performed in three porcine liver samples over a period of 10 min. Fiber optic temperature probes were positioned parallel to the shaft of the cryoprobe in an axial slice orientation. During ablation, temperature measurements were performed simultaneously with CT imaging at 5 s intervals. On the CT images, the average CT number was calculated for a region of interest of 3 × 3 pixels just below the tip of each temperature probe. A linear regression analysis was performed using eleven data sets to determine the dependence of the CT number on the temperature. RESULTS: With decreasing temperature, an increasing hypodense area around the tip of the cryoprobe was observed on the CT images and decreasing values of the CT number were determined. Starting at a temperature of - 40°C a linear relation between the CT number and the temperature was determined and a thermal sensitivity of 0.95 HU/°C (R2  = 0.73) was obtained. The thermal sensitivity was used to calculate color-coded temperature maps. The calculated temperature distribution corresponds quantitatively to the increasing hypodense area. CONCLUSIONS: A noninvasive CT-based temperature determination during cryoablation in a normal ex vivo porcine liver is feasible. A thermal sensitivity of 0.95 HU/°C was determined by linear regression analysis. A color-coded map of the temperature distribution was presented.

Dual-Energy Computed Tomography-Based Display of Bone Marrow Edema in Incidental Vertebral Compression Fractures: Diagnostic Accuracy and Characterization in Oncological Patients Undergoing Routine Staging Computed Tomography.

PURPOSE: The aim of this study was to evaluate the diagnostic performance of virtual noncalcium (VNCa) dual-energy computed tomography (DECT) reconstructions enabling visualization of bone marrow edema for characterization of incidental thoracolumbar compression fractures in routine thoracoabdominal staging computed tomography (CT). MATERIALS AND METHODS: We retrospectively analyzed 51 oncological patients without suspected fracture or indicative complaints presenting at least 1 thoracolumbar compression fracture on routine thoracoabdominal staging DECT who had been examined between October 2015 and June 2017 using third-generation dual-source CT, had a previous CT within 3 months before, and also had undergone additional magnetic resonance imaging within 14 days, which served as the standard of reference. Three independent and blinded radiologists initially evaluated all vertebrae on conventional grayscale DECT series; after at least 8 weeks, observers reevaluated all cases using grayscale and color-coded VNCa DECT images. The age of each fracture was determined as either acute, chronic, or inconclusive. Specificity, sensitivity, and intraobserver and interobserver agreements were calculated taking into account clustering. RESULTS: A total of 98 vertebral compression fractures were detected in 51 patients (20 women, 31 men; median of 1 fracture per patient). The reference standard defined 45 as acute and 53 as chronic. For identification of only acute fractures (cutoff 1), the combination of grayscale and VNCa image series showed a higher sensitivity (91% vs 47%; P < 0.001) but equal specificity (both 100%) compared with analysis of grayscale images alone. When defining a positive finding as a fracture considered either acute or inconclusive (cutoff 2), combined analysis of grayscale and VNCa images showed similar sensitivity (96% vs 93%; P = 0.28) but significantly higher specificity (96% vs 75%; P < 0.001) compared with evaluation of grayscale images alone. Area under the curve analysis for detection of vertebral compression fractures showed superior results for reading of grayscale and VNCa image series (0.98) compared with analysis of grayscale images alone (0.89; P < 0.001). CONCLUSION: Dual-energy CT-derived color-coded VNCa reconstructions substantially improve the characterization of incidental thoracolumbar compression fractures seen on routine thoracoabdominal staging DECT by allowing for visualization of bone marrow edema.

Microwave ablation of pancreatic tumors.

OBJECTIVES: To evaluate the clinical performance of percutaneous microwave ablation (MWA) for treatment of locally-advanced-pancreatic-cancer (LAPC). MATERIAL AND METHODS: Twenty-two MWA sessions (August 2015-March 2017) in 20 patients with primary pancreatic cancer (13 men, 7 women, mean-age: 59.9 ± 8.6 years, range: 46-73 years), who had given informed consent, were retrospectively evaluated. All procedures were performed percutaneously under CT-guidance using the same high-frequency (2.45-GHz) MWA device. Tumor location and diameter, ablation diameter and volume, roundness, duration, technical success and efficacy, output energy, complications, and local tumor progression defined as a tumor focus connected to the edge of a previously technically efficient ablation zone were collected. RESULTS: Seventeen pancreatic malignant tumors (77.3%) were located in the pancreatic head and five (22.7%) in the pancreatic tail. Initial Mean Tumor Diameter was 30 ± 6 mm. Technical success and efficacy were idem (100%). No major complications occurred. Two patients (9.1%) showed minor complications of severe local pain related to MWA. Post-ablation diameter was on average 34.4 ± 5.8 mm. Mean ablation volume was 7.8 ± 3.8 cm³. The mean transverse roundness index was 0.74 ± 0.14. Mean ablation time was 2.6 ± 0.96 min. The mean applied energy per treatment was 9627 ± 3953 J. Local tumor progression was documented in one case (10%) of the 10/22 available three-month follow-up imaging studies. CONCLUSION: High-frequency (2.45 GHz) microwave ablation (MWA) for treatment of unresectable and non-metastatic locally-advanced-pancreatic-cancer (LAPC) shows promising results regarding feasibility and safety of percutaneous approach after short-term follow-up and should be further evaluated.

Transarterial chemoembolization in pancreatic adenocarcinoma with liver metastases: MR-based tumor response evaluation, apparent diffusion coefficient (ADC) patterns, and survival rates.

PURPOSE: To retrospectively investigate the effectiveness of triple drug combination transarterial chemoembolization (TACE) on local tumor response and survival in patients with liver metastases from pancreatic cancer. Also, this study will evaluate the variances in response regarding the number of metastases, assess the correlation between tumor response and the changes in the apparent diffusion coefficients (ADC) in diffusion weighted (DW) MRI. MATERIALS AND METHODS: One hundred and twelve patients (58 men and 54 women; mean age 57) with malignant liver metastases from pancreatic adenocarcinoma underwent at least one session of TACE with a chemotherapeutic combination of mitomycin C, cisplatin, and gemcitabine. A size-based evaluation of tumor response (response evaluation criteria in solid tumors (RECIST)) was conducted, along with ADC values, and survival indices as related to treatment pattern. RESULTS: Four weeks following the end of the treatment, 78.26% of patients showed stable disease and 11.59% showed partial response. The median survival time was 19 months and for the stable disease group, 26 months. Low pretreatment ADC values showed no significant correlation to poor response to treatment (r = 0.347,p = 0.146). CONCLUSION: The triple drug TACE technique showed improvements in median survival times in patients with hepatic metastases from pancreatic carcinoma and helped control disease progression, whereas the number of hepatic lesions was not a statistically significant factor in patients' response to TACE. The data suggest that pre-treatment ADC values in DW-MRI have no statistical correlation with tumor response.

Microwave Ablation (MWA): Basics, Technique and Results in Primary and Metastatic Liver Neoplasms - Review Article.

Purpose The locoregional interventional oncological treatment approach is an accepted modality for liver neoplasms, especially for hepatocellular carcinoma (HCC) and oligonodular liver metastases. Materials and Methods The main aim of ablation therapies like microwave ablation (MWA) is to eradicate all malignant cells in a minimally invasive technique under imaging guidance while preserving the healthy tissue with a sufficient safety margin (at least 5 mm) surrounding the ablated lesion. Results Ablation therapy can be performed via a percutaneous, laparoscopic or intraoperative approach under ultrasound, MRI or CT guidance for adequate localization and monitoring of the ablation process. Conclusion Ablation is the method of choice for oligonodular HCCs ≤ 3 cm. The technical success rate varies from 88 % to 98 % and progression-free survival (PFS) at 3 years from 27 % to 91.7 %. The same criteria apply to the therapy of liver metastases. Key Points · Careful selection of patients proves to be essential for optimum results of MWA. · Interventionists should be familiar with all aspects of complication and rapid assessment of imaging methods in order to evaluate induced damage by thermal ablation. · MWA seems to have some advantages over radiofrequency ablation, like shorter ablation time, less pain, less heat sink effect; however, scientific proof is needed. Citation Format · Vogl TJ, Nour-Eldin A, Hammerstingl RM et al. Microwave Ablation (MWA): Basics, Technique and Results in Primary and Metastatic Liver Neoplasms - Review Article. Fortschr Röntgenstr 2017; 189: 1055 - 1066.

Thermal Ablation of Lung Tumors: Focus on Microwave Ablation.

Background Image-guided thermal ablation can be used for the treatment of medically inoperable primary and metastatic lung cancer. These techniques are based on the heating up or freezing (cryoablation) of a volume of tissue around a percutaneous applicator that induces necrosis of the tumor. Method The English-language literature concerning thermal ablation of the lung was reviewed. Radiofrequency ablation (RFA) is the most widely performed and investigated of these techniques. Microwave ablation (MWA) represents a relatively new alternative that shares the same indications and is conducted in a very similar fashion as RFA. It has been experimentally and clinically shown that MWA produces larger, more spherical ablation zones over shorter periods of time compared to RFA. Seven different MWA systems are available in Europe and the USA with significant differences in the size and shape of the produced ablation zones. Results The types of complications caused by MWA and their rates of occurrence are very similar to those caused by RFA. The local progression rates after MWA of lung malignancies vary between 0 % and 34 % and are similar to those in the RFA literature. Conclusion Despite technical improvements, the current generation of MWA systems has comparable clinical outcomes to those of RFA. Key Points · MWA is a safe technique that should be considered one of the treatment options for medically inoperable lung tumors. · As thermal ablations of lung tumors are becoming more frequent, radiologists should be acquainted with the post-ablation imaging characteristics. · Although MWA has some theoretical advantages over RFA, the clinical outcomes are similar. Citation Format · Vogl TJ, Nour-Eldin NA, Albrecht MH et al. Thermal Ablation of Lung Tumors: Focus on Microwave Ablation. Fortschr Röntgenstr 2017; 189: 828 - 843.

Ultrafast cone-beam computed tomography: a comparative study of imaging protocols during image-guided therapy procedure.

OBJECTIVE: To evaluate two ultrafast cone-beam CT (UF-CBCT) imaging protocols with different acquisition and injection parameters regarding image quality and required contrast media during image-guided hepatic transarterial chemoembolization (TACE). METHODS: In 80 patients (male: 46, female: 34; mean age: 56.8 years; range: 33-83) UF-CBCT was performed during TACE for intraprocedural guidance. Imaging was performed using two ultrafast CBCT acquisition protocols with different acquisition and injection parameters (imaging protocol 1: acquisition time 2.54 s, and contrast 6 mL with 3 s delay; imaging protocol 2: acquisition time 2.72 s, and contrast 7 mL with 6 s delay). Image evaluation was performed with both qualitative and quantitative methods. Contrast injection volume and dose parameters were compared using values from the literature. RESULTS: Imaging protocol 2 provided significantly better (P < 0.05) image quality than protocol 1 at the cost of slightly higher contrast load and patient dose. Imaging protocol 1 provided good contrast perfusion but it mostly failed to delineate the tumors (P < 0.05). On the contrary, imaging protocol 2 showed excellent enhancement of hepatic parenchyma, tumor, and feeding vessels. CONCLUSION: Tumor delineation, visualization of hepatic parenchyma, and feeding vessels are clearly possible using imaging protocol 2 with ultrafast CBCT imaging. A reduction of required contrast volume and patient dose were achieved due to the ultrafast CBCT imaging.