Evaluation of potential tissue heating during percutaneous drill-assisted bone sampling in an in vivo porcine study.

BACKGROUND: Minimally invasive, battery-powered drilling systems have become the preferred tool for obtaining representative samples from bone lesions. However, the heat generated during battery-powered bone drilling for bone biopsies has not yet been sufficiently investigated. Thermal necrosis can occur if the bone temperature exceeds a critical threshold for a certain period of time. PURPOSE: To investigate heat production as a function of femur temperature during and after battery-powered percutaneous bone drilling in a porcine in vivo model. METHODS: We performed 16 femur drillings in 13 domestic pigs with an average age of 22 weeks and an average body temperature of 39.7 °C, using a battery-powered drilling system and an intraosseous temperature monitoring device. The standardized duration of the drilling procedure was 20 s. The bone core specimens obtained were embedded in 4% formalin, stained with haematoxylin and eosin (H&E) and sent for pathological analysis of tissue quality and signs of thermal damage. RESULTS: No significant changes in the pigs' local temperature were observed after bone drilling with a battery-powered drill device. Across all measurements, the median change in temperature between the initial measurement and the temperature measured after drilling (at 20 s) was 0.1 °C. Histological examination of the bone core specimens revealed no signs of mechanical or thermal damage. CONCLUSION: Overall, this preliminary study shows that battery-powered, drill-assisted harvesting of bone core specimens does not appear to cause mechanical or thermal damage.

Reliability of NI-RADS criteria in the interpretation of contrast-enhanced magnetic resonance imaging considering the potential role of diffusion-weighted imaging.

OBJECTIVES: To assess inter- and intrareader agreement of the Neck Imaging Reporting and Data System (NI-RADS) used in contrast-enhanced magnetic resonance imaging (MRI) including analysis of diffusion-weighted imaging (DWI), which is currently not part of the NI-RADS criteria. METHODS: This retrospective study included anonymized surveillance contrast-enhanced MRI datasets of 104 patients treated for different head and neck cancers. Three radiologists experienced in head and neck imaging reported findings for the primary site and the neck using NI-RADS criteria in a first step and evaluated DWI sequences for the primary site in a second step. Thirty randomly selected imaging datasets were again presented to the readers. Kappa statistics and observed agreement (Ao) were calculated. RESULTS: Interreader agreement across all MRI datasets was moderate (κFleiss = 0.53) for NI-RADS categories assigned to the primary site, substantial for NI-RADS categories of the neck (κFleiss = 0.67), and almost perfect for DWI of the primary site (κFleiss = 0.83). Interreader agreement for the primary site was particularly low in cases of cancer recurrence (κFleiss = 0.35) and when categories 2a, 2b, and 3 were combined (κFleiss = 0.30). Intrareader agreement was considerably lower for NI-RADS categories of the primary site (range Ao = 53.3-70.0%) than for NI-RADS categories of the neck (range Ao = 83.3-90.0%) and DWI of the primary site (range Ao = 93.3-100.0%). CONCLUSION: Interreader agreement of NI-RADS for reporting contrast-enhanced MRI findings is acceptable for the neck but limited for the primary site. Here, DWI has the potential to serve as a reliable additional criterion. KEY POINTS: • NI-RADS was originally designed for contrast-enhanced computed tomography with or without positron emission tomography but can also be used for contrast-enhanced magnetic resonance imaging alone. • Overall interreader agreement was acceptable for NI-RADS categories assigned to the neck but should be improved for the primary site, where it was inferior to DWI; similar tendencies were found for intrareader agreement. • DWI is currently no criterion of NI-RADS, but has shown potential to improve its reliability, especially for categories 2a, 2b, and 3 of the primary site.

CT-based quantification of short-term tissue shrinkage following hepatic microwave ablation in an in vivo porcine liver model.

BACKGROUND: Microwave ablation (MWA) is a minimally invasive treatment option for solid tumors and belongs to the local ablative therapeutic techniques, based on thermal tissue coagulation. So far there are mainly ex vivo studies that describe tissue shrinkage during MWA. PURPOSE: To characterize short-term volume changes of the ablated zone following hepatic MWA in an in vivo porcine liver model using contrast-enhanced computer tomography (CECT). MATERIAL AND METHODS: We performed multiple hepatic MWA with constant energy parameters in healthy, narcotized and laparotomized domestic pigs. The volumes of the ablated areas were calculated from venous phase CT scans, immediately after the ablation and in short-term courses of up to 2 h after MWA. RESULTS: In total, 19 thermally ablated areas in 10 porcine livers could be analyzed (n = 6 with two volume measurements during the measurement period and n = 13 with three measurements). Both groups showed a statistically significant but heterogeneous volume reduction of up to 12% (median 6%) of the ablated zones in CECT scans during the measurement period (P < 0.001 [n = 13] and P = 0.042 [n = 6]). However, the dimension and dynamics of volume changes were heterogenous both absolutely and relatively. CONCLUSION: We observed a significant short-term volume reduction of ablated liver tissue in vivo. This volume shrinkage must be considered in clinical practice for technically successful tumor treatment by MWA and therefore it should be further investigated in in vivo studies.

Comparison of different 4D CT-Perfusion algorithms to visualize lesions after microwave ablation in an in vivo porcine model.

Background: Accurate lesion visualization after microwave ablation (MWA) remains a challenge. Computed tomography perfusion (CTP) has been proposed to improve visualization, but it was shown that different perfusion-models delivered different results on the same data set.Purpose: Comparison of different perfusion algorithms and identification of the algorithm enables for the best imaging of lesion after hepatic MWA.Materials and methods: 10 MWA with consecutive CTP were performed in healthy pigs. Parameter-maps were generated using a single-input-dual-compartment-model with Patlak's algorithm (PM), a dual-input-maximum-slope-model (DIMS), a dual-input-one-compartment-model (DIOC), a single-(SIDC) and dual-input-deconvolution-model (DIDC). Parameter-maps for hepatic arterial (AF) and portal venous blood flow (PF), mean transit time, hepatic blood volume (HBV) and capillary permeability were compared regarding the values of the normal liver tissue (NLT), lesion, contrast- and signal-to-noise ratios (SNR, CNR) and inter- and intrarater-reliability using the intraclass correlation coefficient, Bland-Altman plots and linear regression.Results: Perfusion values differed between algorithms with especially large fluctuations for the DIOC. A reliable differentiation of lesion margin appears feasible with parameter-maps of PF and HBV for most algorithms, except for the DIOC due to large fluctuations in PF. All algorithms allowed for a demarcation of the central necrotic zone based on hepatic AF and HBV. The DIDC showed the highest CNR and the best inter- and intrarater reliability.Conclusion: The DIDC appears to be the most feasible model to visualize margins and necrosis zones after microwave ablation, but due to high computational demand, a single input deconvolution algorithm might be preferable in clinical practice.

Periradicular infiltration of the lumbar spine: is iterative reconstruction software necessary to establish ultra-low-dose protocols? A quantitative and qualitative approach.

PURPOSE: Computed tomography (CT)-guided periradicular infiltration therapy has emerged as an effective treatment option for patients with low back pain. Concern about radiation exposure requires approaches allowing significant dose reduction. The purpose of this study is to evaluate the need for iterative reconstruction software in CT-guided periradicular infiltration therapy with an ultra-low-dose protocol. MATERIALS AND METHODS: One hundred patients underwent CT-guided periradicular infiltration therapy of the lumbar spine using an ultra-low-dose protocol with adaptive iterative dose reduction 3D (AIDR 3D) for image reconstruction. In addition, images were reconstructed with filtered back-projection (FBP). Four experienced raters evaluated both reconstruction types for conspicuity of anatomical and instrumental features important for ensuring safe patient treatment. Image noise was measured as a quantitative marker of image quality. RESULTS: Interrater agreement was good for both AIDR 3D (Kendall's W = 0.83) and FBP (0.78) reconstructions. Readers assigned the same scores for all features and both reconstruction algorithms in 81.3% of cases. Image noise was significantly lower (average SD of 60.07 vs. 99.54, p < 0.05) for AIDR 3D-reconstructed images. CONCLUSION: Although it significantly lowers image noise, iterative reconstruction software is not mandatory to achieve adequate image quality with an ultra-low-dose CT protocol for guiding periradicular infiltration therapy of the lumbar spine.

Ultra-low-dose periradicular infiltration of the lumbar spine: spot scanning and its potential for further dose reduction by replacing helical planning CT.

PURPOSE: Computed tomography (CT)-guided periradicular infiltration has become an accepted procedure for treating radiculopathy-associated low back pain. The purpose of this study is to compare spot scanning and segmental helical planning CT in terms of dose reduction. MATERIALS AND METHODS: Eighty-five patients underwent CT-guided single-site lumbar periradicular therapy. Prior imaging was not available for planning. Sixty-three patients were examined with a new dedicated spot scanning technique (group I), and twenty-two patients underwent conventional segmental planning CT examinations with helical image acquisition serving as controls (group II). Examinations were reviewed retrospectively for dose-length product (DLP) and number of acquisitions required for intervention. Pain reduction accomplished with the intervention was recorded for quality assurance. RESULTS: Median DLP was 0.80 mGy cm for spot scanning versus 6.50 mGy cm for segmental planning CT. Thus, the contribution of the planning scan to the total interventional dose decreased from 73 to 25%. As a result, the total interventional dose was reduced significantly from a median DLP of 8.90 mGy cm to 3.20 mGy cm (-64%). Acquisitions required during the intervention had a median DLP of 2.40 mGy cm for group I and 2.35 mGy cm for group II, showing no significant difference. Median pain reduction in both groups was two points on the numeric rating scale. CONCLUSION: Dedicated spot scanning for planning reduced the total median effective dose of the intervention by more than 64% without increasing the number of images required during the interventional procedure. Significant pain reduction was achieved with both approaches. Spot scanning is recommended for dose reduction.

Hepatopulmonary shunting after surgical, interventional and systemic therapy in patients with liver malignancies scheduled for radioembolization.

BACKGROUND: Hepatopulmonary shunts (HPS) lead to radiation exposure of the lungs in patients undergoing radioembolization (RE) of malignant liver tumors. PURPOSE: To retrospectively analyze how HPS is affected by prior systemic or local therapy of the liver. MATERIAL AND METHODS: The percentage HPS was calculated from SPECT/CT scans obtained after technetium-99 m macroaggregated albumin administration into hepatic arteries in 316 patients evaluated for RE. RESULTS: Patients with partial liver resection (n = 80) did not differ in HPS from the remaining patient population (n = 236) (HPS (median [range]) = 10.2 [2.1-48.3]resection% vs. 8.9 [2.3-32.9]no resection%; P = 0.527). In patients undergoing sequential RE, HPS was significantly higher in the liver lobe treated second (n = 10; HPS = 6.4 [2.1-10.2]firstlobe/session% vs. 12.0 [2.0-24.6]second lobe/session%; P = 0.019). (Chemo-)embolization (n = 19; HPS = 11.0 [2.8-48.3]%) or transcutaneous ablation (n = 63; HPS = 8.8 [3.0-32.9]%) had no effect on HPS compared to patients without prior interventions (no (chemo-)embolization: n = 297; HPS = 9.3 [2.1-47.3]%; P = 0.489; no ablation: n = 253; HPS = 9.5 [2.1-48.3]%; P = 0.382). Pretreatment with sorafenib (HPS = 9.5 [2.3-35.9]yes% vs. 10.2 [2.8-42.0]no%; P = 0.777) orbevacizumab (HPS = 10.7 [2.1-30.6]yes% vs. 9.0 [3.9-23.3]no%; P = 0.870) had no effect on HPS. CONCLUSION: Sequential RE results in an increase in the HPS in the contralateral liver lobe at the time of the second RE session. Other investigated therapy do not affect HPS.

Anatomic variants of arteries often coil-occluded prior to hepatic radioembolization.

BACKGROUND: Prior to radioembolization (RE) treatment of malignant liver lesions, many interventionalists occlude the right gastric artery (RGA), the cystic artery (CA), and the gastroduodenal artery (GDA) to prevent radioactive microspheres from entering non-target vessels. PURPOSE: To systematically analyze anatomic variants of arteries that are important to know for the interventional radiologist performing RE of the liver. MATERIAL AND METHODS: The computed tomography (CT) angiographies and conventional angiographies of 166 patients evaluated for RE were retrospectively analyzed for the presence of anatomic variants of the RGA, GDA, and CA. RESULTS: The RGA was found to arise from the left hepatic artery in 42% of cases, from the proper hepatic artery in 40%, from the GDA in 10%, from the right hepatic artery in 4%, and from the common hepatic artery in 3% of cases. The GDA originated in the common hepatic artery in 97% of cases, in the left hepatic artery in 2%, and in the celiac trunk in 1% of cases. The CA arose from the right hepatic artery in 96% of cases and from the GDA in 2% of cases; in 2% of our study population, the gallbladder was supplied by small branches from the liver parenchyma. CONCLUSION: Variant anatomy of the RGA is common, while it is quite rare for the GDA and CA. Knowledge of the variations of liver supplying arteries helps the interventionalist to embolize necessary vessels prior to RE.

Deep-Learning-Based Diagnosis of Bedside Chest X-ray in Intensive Care and Emergency Medicine.

OBJECTIVES: Validation of deep learning models should separately consider bedside chest radiographs (CXRs) as they are the most challenging to interpret, while at the same time the resulting diagnoses are important for managing critically ill patients. Therefore, we aimed to develop and evaluate deep learning models for the identification of clinically relevant abnormalities in bedside CXRs, using reference standards established by computed tomography (CT) and multiple radiologists. MATERIALS AND METHODS: In this retrospective study, a dataset consisting of 18,361 bedside CXRs of patients treated at a level 1 medical center between January 2009 and March 2019 was used. All included CXRs occurred within 24 hours before or after a chest CT. A deep learning algorithm was developed to identify 8 findings on bedside CXRs (cardiac congestion, pleural effusion, air-space opacification, pneumothorax, central venous catheter, thoracic drain, gastric tube, and tracheal tube/cannula). For the training dataset, 17,275 combined labels were extracted from the CXR and CT reports by a deep learning natural language processing (NLP) tool. In case of a disagreement between CXR and CT, human-in-the-loop annotations were used. The test dataset consisted of 583 images, evaluated by 4 radiologists. Performance was assessed by area under the receiver operating characteristic curve analysis, sensitivity, specificity, and positive predictive value. RESULTS: Areas under the receiver operating characteristic curve for cardiac congestion, pleural effusion, air-space opacification, pneumothorax, central venous catheter, thoracic drain, gastric tube, and tracheal tube/cannula were 0.90 (95% confidence interval [CI], 0.87-0.93; 3 radiologists on the receiver operating characteristic [ROC] curve), 0.95 (95% CI, 0.93-0.96; 3 radiologists on the ROC curve), 0.85 (95% CI, 0.82-0.89; 1 radiologist on the ROC curve), 0.92 (95% CI, 0.89-0.95; 1 radiologist on the ROC curve), 0.99 (95% CI, 0.98-0.99), 0.99 (95% CI, 0.98-0.99), 0.98 (95% CI, 0.97-0.99), and 0.99 (95% CI, 0.98-1.00), respectively. CONCLUSIONS: A deep learning model used specifically for bedside CXRs showed similar performance to expert radiologists. It could therefore be used to detect clinically relevant findings during after-hours and help emergency and intensive care physicians to focus on patient care.

Improving CT accuracy in the diagnosis of COVID-19 in a hospital setting.

OBJECTIVE: This study aimed to improve the accuracy of CT for detection of COVID-19-associated pneumonia and to identify patient subgroups who might benefit most from CT imaging. METHODS: A total of 269 patients who underwent CT for suspected COVID-19 were included in this retrospective analysis. COVID-19 was confirmed by reverse-transcription-polymerase-chain-reaction. Basic demographics (age and sex) and initial vital parameters (O2-saturation, respiratory rate, and body temperature) were recorded. Generalized mixed models were used to calculate the accuracy of vital parameters for detection of COVID-19 and to evaluate the diagnostic accuracy of CT. A clinical score based on vital parameters, age, and sex was established to estimate the pretest probability of COVID-19 and used to define low, intermediate, and high risk groups. A p-value of <0.05 was considered statistically significant. RESULTS: The sole use of vital parameters for the prediction of COVID-19 was inferior to CT. After correction for confounders, such as age and sex, CT showed a sensitivity of 0.86, specificity of 0.78, and positive predictive value of 0.36. In the subgroup analysis based on pretest probability, positive predictive value and sensitivity increased to 0.53 and 0.89 in the high-risk group, while specificity was reduced to 0.68. In the low-risk group, sensitivity and positive predictive value decreased to 0.76 and 0.33 with a specificity of 0.83. The negative predictive value remained high (0.94 and 0.97) in both groups. CONCLUSIONS: The accuracy of CT for the detection of COVID-19 might be increased by selecting patients with a high-pretest probability of COVID-19.

Comparing different deep learning architectures for classification of chest radiographs.

Chest radiographs are among the most frequently acquired images in radiology and are often the subject of computer vision research. However, most of the models used to classify chest radiographs are derived from openly available deep neural networks, trained on large image datasets. These datasets differ from chest radiographs in that they are mostly color images and have substantially more labels. Therefore, very deep convolutional neural networks (CNN) designed for ImageNet and often representing more complex relationships, might not be required for the comparably simpler task of classifying medical image data. Sixteen different architectures of CNN were compared regarding the classification performance on two openly available datasets, the CheXpert and COVID-19 Image Data Collection. Areas under the receiver operating characteristics curves (AUROC) between 0.83 and 0.89 could be achieved on the CheXpert dataset. On the COVID-19 Image Data Collection, all models showed an excellent ability to detect COVID-19 and non-COVID pneumonia with AUROC values between 0.983 and 0.998. It could be observed, that more shallow networks may achieve results comparable to their deeper and more complex counterparts with shorter training times, enabling classification performances on medical image data close to the state-of-the-art methods even when using limited hardware.

Subregion Radiomics Analysis to Display Necrosis After Hepatic Microwave Ablation-A Proof of Concept Study.

OBJECTIVES: The aim of this study was to improve the visualization of coagulation necrosis after computed tomography (CT)-guided microwave ablation (MWA) in routine postablational imaging. MATERIALS AND METHODS: Ten MWAs were performed in 8 pigs under CT guidance. After each ablation, we obtained contrast-enhanced CT scans in venous phase. Ablations were then resected as a whole, and histologic slices were obtained orthogonally through the ablation center. Subsequently, a vital stain was applied to the sections for visualization of coagulation necrosis. Computed tomography images were reformatted to match the histologic slices. Afterwards, quantitative imaging features were extracted from the subregions of all images, and binary classifiers were used to predict the presence of coagulation necrosis for each subregion. From this, heatmaps could be created, which visually represented the extent of necrosis in each CT image. Two independent observers evaluated the extent of coagulative necrosis between the heat maps and histological sections. RESULTS: We applied 4 different classifiers, including a generalized linear mixed model (GLMM), a stochastic gradient boosting classifier, a random forest classifier, and a k-nearest neighbor classifier, out of which the GLMM showed the best performance to display coagulation necrosis. The GLMM resulted in an area under the curve of 0.84 and a Jaccard index of 0.6 between the generated heat map and the histologic reference standard as well as a good interobserver agreement with a Jaccard index of 0.9. CONCLUSIONS: Subregion radiomics analysis may improve visualization of coagulation necrosis after hepatic MWA in an in vivo porcine model.

Exploring Patterns of Dynamic Size Changes of Lesions after Hepatic Microwave Ablation in an In Vivo Porcine Model.

Microwave ablation (MWA) is a type of minimally invasive cancer therapy that uses heat to induce necrosis in solid tumours. Inter- and post-ablational size changes can influence the accuracy of control imaging, posing a risk of incomplete ablation. The present study aims to explore post-ablation 3D size dynamics in vivo using computed tomography (CT). Ten MWA datasets obtained in nine healthy pigs were used. Lesions were subdivided along the z-axis with an additional planar subdivision into eight subsections. The volume of the subsections was analysed over different time points, subsequently colour-coded and three-dimensionally visualized. A locally weighted polynomial regression model (LOESS) was applied to describe overall size changes, and Student's t-tests were used to assess statistical significance of size changes. The 3D analysis showed heterogeneous volume changes with multiple small changes at the lesion margins over all time points. The changes were pronounced at the upper and lower lesion edges and characterized by initially eccentric, opposite swelling, followed by shrinkage. In the middle parts of the lesion, we observed less dimensional variations over the different time points. LOESS revealed a hyperbolic pattern for the volumetric changes with an initially significant volume increase of 11.6% (111.6% of the original volume) over the first 32 minutes, followed by a continuous decrease to 96% of the original volume (p < 0.05).

Instant Outcome Evaluation of Microwave Ablation With Subtraction CT in an In Vivo Porcine Model.

OBJECTIVES: The aim of this study was to investigate whether the accuracy of multislice contrast-enhanced computed tomography (MS-CECT) may be improved by performing additional subtraction CT. MATERIALS AND METHODS: Thirty-five microwave ablations were performed under CT guidance in 12 healthy and anesthetized pigs. Preablation and postablation MS-CECT scans were obtained in arterial and venous contrast phases. These scans were reconstructed and subtracted from each other. Lesion size was measured in a region of interest drawn around the ablation area. Computed tomography measurements were compared with standardized macroscopic images of explanted liver tissue, obtained immediately after ablation. Paired correlation and Bland-Altman analyses were performed for assessing agreement between modalities and ratings. RESULTS: The correlation between lesion size measured in CT and histology was very strong for subtracted images (r = 0.91; 95% confidence interval [CI], 0.8-0.96) and strong for standard MS-CECT images (r = 0.85; 95% CI, 0.68-0.93). Interrater agreement for all measurements was excellent (intraclass correlation coefficient, 0.99; 95% CI, 0.98-0.99 for subtraction and intraclass correlation coefficient, 0.99; 95% CI, 0.98-1.00 for MS-CECT). All differences were statistically significant (P < 0.05). CONCLUSIONS: Subtraction CT was superior to nonsubtracted MS-CECT in measurement of liver lesion size after microwave ablation in a porcine model, achieving a very strong correlation with pathologic measurement and a significantly lower overestimation of lesion size compared with MS-CECT.

Improved Visualization of the Necrotic Zone after Microwave Ablation Using Computed Tomography Volume Perfusion in an In Vivo Porcine Model.

After hepatic microwave ablation, the differentiation between fully necrotic and persistent vital tissue through contrast enhanced CT remains a clinical challenge. Therefore, there is a need to evaluate new imaging modalities, such as CT perfusion (CTP) to improve the visualization of coagulation necrosis. MWA and CTP were prospectively performed in five healthy pigs. After the procedure, the pigs were euthanized, and the livers explanted. Orthogonal histological slices of the ablations were stained with a vital stain, digitalized and the necrotic core was segmented. CTP maps were calculated using a dual-input deconvolution algorithm. The segmented necrotic zones were overlaid on the DICOM images to calculate the accuracy of depiction by CECT/CTP compared to the histological reference standard. A receiver operating characteristic analysis was performed to determine the agreement/true positive rate and disagreement/false discovery rate between CECT/CTP and histology. Standard CECT showed a true positive rate of 81% and a false discovery rate of 52% for display of the coagulation necrosis. Using CTP, delineation of the coagulation necrosis could be improved significantly through the display of hepatic blood volume and hepatic arterial blood flow (p < 0.001). The ratios of true positive rate/false discovery rate were 89%/25% and 90%/50% respectively. Other parameter maps showed an inferior performance compared to CECT.

Multipolar RFA of the liver: Influence of intrahepatic vessels on ablation zones and appropriateness of CECT in detecting ablation dimensions - Results of an in-vivo porcine liver model.

BACKGROUND: Radiofrequency ablation (RFA) is an important treatment option for hepatic tumors and metastases. Post-ablation recurrence rates are reported up to 36.5 percent and seem to depend on tumor size, intrahepatic localization of tumors and adjacent hepatic vessels. Multipolar RFA has the potential to overcome/reduce these limitations. Experimental and standardized data on achievable lesion sizes, influence of hepatic vessels and non-invasive evaluation of complete ablation is still insufficient. OBJECTIVES: The aim of this study was to evaluate the influence of intrahepatic vessels on shape and size of multipolar RF-ablation zones in healthy porcine liver and to evaluate the appropriateness of immediate post-ablation contrast-enhanced computed tomography (CECT) in detecting RF-ablation dimensions. MATERIAL AND METHODS: We conducted multipolar RFAs in each of the livers of 10 healthy, narcotized and laparotomized domestic pigs by inserting three parallel probes with a constant probe distance and a constant energy supply. In 4 ablations we interrupted hepatic blood flow using Pringle's maneuver. Immediate post-ablation CECT scans were acquired. After euthanasia the livers were sliced perpendicularly to the probes at the probes' active centers. CECT scans were reconstructed equivalently in order to compare RF-lesion size and shape to the macroscopic sections. RESULTS: In total, 19 RF-lesions were analyzed. Every RF-lesion that was ablated during physiological liver perfusion showed an irregular and cloverleaf-like shape (n = 15). Interrupting the hepatic blood flow during RFA led to well-defined, round and homogeneous ablation zones which were 3.8 times larger compared to RF-lesions ablated during continuous hepatic perfusion (n = 4). We found an excellent correlation between immediate post-ablation CECT slices and macroscopic sections when comparing RF-lesion diameters and area, although CECT tended to overestimate ablation dimensions. CONCLUSIONS: The interruption of hepatic blood flow using Pringle's maneuver during multipolar RFA with three applicators significantly reduces heat sink effects of hepatic vessels and generates large and coherent ablation zones. This approach should be considered in each case of ablation planning adjacent to larger hepatic vessels or when ablating larger tumor volumes. Immediate post-ablation CECT has limited value in detecting incomplete RFA periprocedurally.

Hepatopulmonary shunting in patients with primary and secondary liver tumors scheduled for radioembolization.

PURPOSE: In patients undergoing transarterial radioembolization (RE) of malignant liver tumors, hepatopulmonary shunts (HPS) can lead to nontarget irradiation of the lungs. This study aims at analyzing the HPS fraction in relation to liver volume, tumor volume, tumor-to-liver volume ratio, tumor vascularity, type of tumor, and portal vein occlusion. MATERIALS AND METHODS: In the presented retrospective study the percentage HPS fraction was calculated from SPECT/CT after infusion of Tc-99m macroaggregated albumin (Tc-99m MAA) into the proper hepatic artery of 233 patients evaluated for RE. RESULTS: HPS fractions correlate very weakly with liver volume (r=0.303), tumor volume (r=0.345), and tumor-to-liver volume ratio (r=0.340). Tumors with strong contrast enhancement (HPSmedian(range)=11.7%(46.3%); n=73) have significantly larger shunt fractions than tumors with little enhancement (HPS=8.3%(16.4%); n=61; p<0.001). Colorectal cancer metastases (HPS=10.6%(28.6%); n=68) and hepatocellular cancers (HPS=11.7%(39.4%); n=63) have significantly larger HPS fractions than metastases from breast cancer (HPS=7.4%(16.7%); n=40; p=0.012 and p=0.001). Patients with compression (HPS=13.9%(43.7%); n=33) or tumor thrombosis (HPS=15.8% (31.2%); n=33) of a major portal vein branch have significantly higher degrees of shunting than patients with normal portal vein perfusion (HPS=8.1% (47.0%); n=167; both p<0.001). The shunt fraction is largest in patients with HCC and thrombosis or occlusion of a major portal vein branch (HPS=16.6% (31.0%); n=32). CONCLUSION: The degree of hepatopulmonary shunting depends on the type of liver tumor, tumor vascularity, and portal vein perfusion. There is little to no correlation of HPS with liver volume, tumor volume, or tumor-to-liver volume ratio.