Radiation Exposure and Safety Considerations in Interventional Radiology: Comparison of a Twin Robotic X-ray System to a Conventional Angiography System.

Background/Objectives: To evaluate radiation exposure in standard interventional radiology procedures using a twin robotic X-ray system compared to a state-of-the-art conventional angiography system. Methods: Standard interventional radiology procedures (port implantation, SIRT, and pelvic angiography) were simulated using an anthropomorphic Alderson RANDO phantom (Alderson Research Laboratories Inc. Stamford, CT, USA) on an above-the-table twin robotic X-ray scanner (Multitom Rax, Siemens Healthineers, Forchheim, Germany) and a conventional below-the-table angiography system (Artis Zeego, Siemens Healthineers, Forchheim, Germany). The phantom's radiation exposure (representing the potential patient on the procedure table) was measured with thermoluminescent dosimeters. Height-dependent dose curves were generated for examiners and radiation technologists in representative positions using a RaySafe X2 system (RaySafe, Billdal, Sweden). Results: For all scenarios, the device-specific dose distribution differs depending on the imaging chain, with specific advantages and disadvantages. Radiation exposure for the patient is significantly increased when using the Multitom Rax for pelvic angiography compared to the Artis Zeego, which is evident in the dose progression through the phantom's body as well as in the organ-related radiation exposure. In line with these findings, there is an increased radiation exposure for the performing proceduralist, especially at eye level, which can be significantly minimized by using protective equipment (p < 0.001). Conclusions: In this study, the state-of-the-art conventional below-the-table angiography system is associated with lower radiation dose exposures for both the patient and the interventional radiology physician compared to an above-the-table twin robotic X-ray system for pelvic angiographies. However, in other clinical scenarios (port implantation or SIRT), both devices are suitable options with acceptable radiation exposure.

Prospective comparison of positron emission tomography (PET)/magnetic resonance and PET/computed tomography dosimetry in hepatic malignant neoplastic disease after 90Y radioembolization treatment.

Background: 90Y radioembolization is an established treatment modality for hepatic malignancies. Successful radioembolization requires optimal dose delivery to tumors while minimizing dosages to parenchyma. Post-treatment positron emission tomography (PET)/computed tomography (CT) dosimetry is the established benchmark, whereas PET/magnetic resonance (MR) is an emerging modality. The goal of this study was to assess the intermodality agreement between PET/MR and PET/CT 90Y dosimetry. Methods: In this single-institution study, 18 patients (20 treatment sessions) with a primary or metastatic hepatic malignancy underwent both PET/MR and PET/CT after 90Y radioembolization. Patients were randomized to undergo one modality first, followed by the other. The region of interest was delineated using MR images and tumor and liver dosimetry was calculated. Intermodality agreement was assessed using the Bland-Altman method. A generalized linear model was used to assess the effect of baseline variables on intermodality dose differences. Results: PET/MR underestimated tumor and liver absorbed doses when compared to PET/CT by -3.7% (P=0.042) and -5.8% (P=0.029), respectively. A coverage probability plot demonstrated that 80% and 90% of tumor dose measurements fell within intermodality differences of 11% and 18%, respectively. PET/MR underestimated tumor dose at both low (<1 GBq) and high (>3 GBq) injected activity levels (P<0.001) by -22.3 [standard deviation (SD) =13.5] and -24.3 (SD =18.7), respectively. Conclusions: Although PET/MR significantly underestimated the absorbed dose when compared to PET/CT, the intermodality agreement was high and the degree of underestimation was better than previously reported. Intermodality differences were more pronounced at low and high injected doses. Additional studies are required to assess the clinical implications of these findings.

Prediction of Mortality and Hepatic Encephalopathy after Transjugular Intrahepatic Portosystemic Shunt Placement: Baseline and Longitudinal Body Composition Measurement.

PURPOSE: To investigate effects of baseline and early longitudinal body composition changes on mortality and hepatic encephalopathy (HE) after transjugular intrahepatic portosystemic shunt (TIPS). MATERIALS AND METHODS: This is a case-control study with analysis of a TIPS registry (1995-2020) including data from patients with cirrhosis with computed tomography (CT) scans obtained within 1 month before and 3 months after TIPS. Core muscle area (CMA), macroscopic subcutaneous adipose tissue (mSAT), macroscopic visceral adipose tissue (mVAT) area, and muscle adiposity index (MAI) on CT were obtained. Multipredictor Cox proportional hazards models were used to assess the effect of body composition variables on mortality or HE. RESULTS: In total, 280 patients (158 men; median age, 57.0 years; median Model for End-stage Liver Disease-sodium [MELD-Na] score, 14.0) were included. Thirty-four patients had post-TIPS imaging. Median baseline CMA was 68.3 cm2 (interquartile range, 57.7-83.5 cm2). Patients with higher baseline CMA had decreased risks of mortality (hazard ratio [HR]: 0.82; P = .04) and HE (HR: 0.82; P = .009). It improved prediction of mortality over MELD-Na and post-TIPS right atrial pressure alone (confidence interval = 0.729). An increase in CMA (HR: 0.60; P = .043) and mSAT (HR: 0.86; P = .022) or decrease in MAI (HR: 1.50; P = .049) from before to after TIPS was associated with a decreased risk of mortality. An increase in mSAT was associated with an increased risk of HE (HR: 1.11; P = .04). CONCLUSIONS: CMA on CT scan 1 month before TIPS placement predicts mortality and HE in patients with cirrhosis. Changes in body composition on CT measured 3 months after TIPS placement independently predict mortality and HE.

Noninvasive and invasive imaging of lower-extremity acute and chronic venous thrombotic disease.

The spectrum of venous thromboembolic (VTE) disease encompasses both acute deep venous thrombosis (DVT) and chronic postthrombotic changes (CPC). A large percentage of acute DVT patients experience recurrent VTE despite adequate anticoagulation, and may progress to CPC. Further, the role of iliocaval venous obstruction (ICVO) in lower-extremity VTE has been increasingly recognized in recent years. Imaging continues to play an important role in both acute and chronic venous disease. Venous duplex ultrasound remains the gold standard for diagnosing acute VTE. However, imaging of CPC is more complex and may involve computed tomography, magnetic resonance, contrast-enhanced ultrasound, or intravascular ultrasound. In this narrative review, we aim to discuss the full spectrum of venous disease imaging for both acute and chronic venous thrombotic disease.

Semiautomatic Cone-Beam Computed Tomography Virtual Hepatic Volumetry for Intra-Arterial Therapies.

PURPOSE: To evaluate a software simulating the perfused liver volume from virtual selected embolization points on proximal enhanced cone-beam computed tomography (CT) liver angiography data set using selective cone-beam CT as a reference standard. MATERIALS AND METHODS: Seventy-eight selective/proximal cone-beam CT couples in 46 patients referred for intra-arterial liver treatment at 2 recruiting centers were retrospectively included. A reference selective volume (RSV) was calculated from the selective cone-beam CT by manual segmentation and was used as a reference standard. The virtual perfusion volume (VPV) was then obtained using Liver ASSIST Virtual Parenchyma software on proximal cone-beam CT angiography using the same injection point as for selective cone-beam CT. RSV and VPV were then compared as absolute, relative, and signed volumetric errors (ABSErr, RVErr, and SVErr, respectively), whereas their spatial correspondence was assessed using the Dice similarity coefficient. RESULTS: The software was technically successful in automatically computing VPV in 74 of 78 (94.8%) cases. In the 74 analyzed couples, the median RSV was not significantly different from the median VPV (394 mL [196-640 mL] and 391 mL [192-620 mL], respectively; P = .435). The median ABSErr, RVErr, SVErr, and Dice similarity coefficient were 40.9 mL (19.9-97.7 mL), 12.8% (5%-22%), 9.9 mL (-49.0 to 40.4 mL), and 80% (76%-84%), respectively. No significant ABSErr, RVErr, SVErr, and Dice similarity coefficient differences were found between the 2 centers (P = .574, P = .612, P = .416, and P = .674, respectively). CONCLUSIONS: Perfusion hepatic volumes simulated on proximal enhanced cone-beam CT using the virtual parenchyma software are numerically and spatially similar to those manually obtained on selective cone-beam CT.

Narrative review of portal vein thrombosis in cirrhosis: pathophysiology, diagnosis, and management from an interventional radiology perspective.

Objective: This paper examines the incidence, clinical presentation, and pathophysiology of portal vein thrombosis (PVT) in cirrhosis. Additionally, we have reviewed the literature regarding the current status of medical and interventional radiology management of PVT and have proposed a novel algorithm for the management given different clinical scenarios. Lastly two representative cases displaying endovascular treatment options are provided. Background: Portal vein thrombus in the setting of cirrhosis is an increasingly recognized clinical issue with debate on its pathophysiology, natural course, and optimal treatment. Approximately one-third of patients are asymptomatic, and detection of the thrombus is an incidental finding on imaging performed for other reasons. In 30% to 50% of patients, PVT resolves spontaneously. However, there is increased post-transplant mortality in patients with completely occlusive PVT, therefore effective early revascularization strategies are needed for patients with complete PVT who are expected to undergo liver transplant. Additionally, no consensus has been reached regarding PVT treatment in terms of timing and type of interventions as well as type and duration of anticoagulation. Methods: Computerized literature search as well as discussion with experts in the field. Conclusions: Management of PVT is complex, as many variables affect which treatments can be used. Anticoagulation appears to be the optimal first-line treatment in patients with acute PVT but without bleeding varices or mesenteric ischemia. Minimally invasive treatments include various methods of mechanical thrombectomy, chemical thrombolysis, and transjugular intrahepatic portosystemic shunt (TIPS) placement with or without variceal embolization. Definitive recommendations are difficult due to lack of high quality data and continued research is needed to evaluate the efficacy of different anticoagulants as well as the timing and use of various minimally invasive therapies in specific circumstances.

Advanced ultrasound techniques in arterial diseases.

Ultrasound (US) remains a valuable modality for the assessment of vascular diseases, with conventional sonographic techniques such as grayscale and Doppler US used extensively to assess carotid atherosclerosis and abdominal aortic aneurysms. However, conventional US techniques are inherently limited by factors such as operator dependency and limited field of view. There is an increasing interest in the use of advanced sonographic techniques such as contrast-enhanced US (CEUS) and 3-dimensional (3D) US to mitigate some of these limitations. Clinical applications of advanced sonographic techniques include surveillance of abdominal aortic aneurysm, post-endovascular aortic repair, and carotid atherosclerotic plaques. Recently published studies have demonstrated that CEUS and 3D US are superior to conventional US and comparable to computed tomography for certain vascular applications. Further research is required to fully validate the application of advanced sonographic techniques in evaluating various atherosclerotic diseases.

Hepatic Encephalopathy After TIPS Placement: Predictive Factors, Prevention Strategies, and Management.

Hepatic encephalopathy (HE) is a challenging complication after transjugular intrahepatic portosystemic shunt (TIPS) placement. Despite recent advances, much is still uncertain regarding risk factors, preventative measures, and the management of HE after TIPS placement. Appropriate patient selection and pre-procedural risk stratification remain areas of focus. In this manuscript, we discuss the current state of research related to HE after TIPS placement, including information regarding risk stratification, complication prevention, and treatment options.

Advanced portal venous access techniques for transjugular intrahepatic portosystemic shunt placement.

INTRODUCTION: Transjugular intrahepatic portosystemic shunt (TIPS) placement is a well-established but technically challenging procedure for the management of sequelae of end-stage liver disease. Performed essentially blindly, traditional fluoroscopically guided TIPS placement requires multiple needle passes and prolonged radiation exposure to achieve successful portal venous access, thus increasing procedure time and the risk of periprocedural complications. Several advanced image-guided portal access techniques, including intracardiac echocardiography (ICE)-guided access, cone-beam CT (CBCT)-guided access and wire-targeting access techniques, can serve as alternatives to traditional CO2 portography-based TIPS creation. METHODS: A literature search was performed on the electronic databases including MEDLINE and Embase, from 2000 to the present to identify all relevant studies. The reference list also included studies identified manually, and studies referenced for other purposes. FINDINGS: The main benefit of these advanced access techniques is that they allow the operator to avoid essentially blind portal punctures, and the ability to visualise the target, thus reducing the number of required needle passes. Research has shown that ICE-guided access can decrease the radiation exposure, procedure time and complication rate in patients undergoing TIPS placement. This technique is particularly useful in patients with challenging portal venous anatomy. However, ICE-guided access requires additional equipment and possibly a second operator. Other studies have shown that CBCT-guided access, when compared with traditional fluoroscopy-guided access, provides superior visualisation of the anatomy with similar amount of radiation exposure and procedure time. The wire-targeting technique, on the other hand, appears to offer reductions in procedure time and radiation exposure by enabling real-time guidance. However, this technique necessitates percutaneous injury to the liver parenchyma in order to place the target wire. CONCLUSION: Advanced portal access techniques have certain advantages over the traditional fluoroscopically guided TIPS access. To date, few studies have compared these advanced guided access options, and further research is required.

Single-Center Comparison of Overall Survival and Toxicities in Patients with Infiltrative Hepatocellular Carcinoma Treated with Yttrium-90 Radioembolization or Drug-Eluting Embolic Transarterial Chemoembolization.

PURPOSE: To compare overall survival and toxicities after yttrium-90 (90Y) radioembolization and chemoembolization with drug-eluting embolics (DEE) in patients with infiltrative hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Retrospective review of 50 patients with infiltrative HCC without main portal vein invasion who were treated with 90Y radioembolization (n = 26) or DEE chemoembolization (n = 24) between March 2007 and August 2012 was completed. Infiltrative tumors were defined by cross-sectional imaging as masses that lacked well-demarcated boundaries, and treatment allocations were made by a multidisciplinary tumor board. Median age was 63 years; median tumor diameter was 9.0 cm; and there were no significant differences between groups in performance status, severity of liver disease, or HCC stage. Toxicities were graded by Common Terminology Criteria for Adverse Events v4.03. Overall survival from treatment was assessed by Kaplan-Meier analysis, with analysis of potential predictors of survival with log-rank test. RESULTS: There was no difference in the average number of procedures performed in each treatment group (DEE, 1.5 ± 1.1; 90Y, 1.6 ± 0.5; P = .97), and technical success was achieved in all cases. Abdominal pain (73% vs 33%; P = .004) and fever (38% vs 8%; P = .01) were more frequent after DEE chemoembolization. There was no significant difference in median overall survival between treatment groups after treatment (DEE, 9.9 months; 90Y, 8.1 months; P = .11). CONCLUSIONS: 90Y radioembolization and DEE chemoembolization provided similar overall survival in the treatment of infiltrative HCC without main portal vein invasion. Abdominal pain and fever were more frequent after DEE chemoembolization.

Pulmonary thromboendarterectomy in the setting of a mediastinal venous malformation with a congenitally absent left subclavian vein.

Venous malformations have static venous lakes that predispose to spontaneous venous thrombosis within the malformation due to its low-flow static state. Thrombi of varying sizes can then embolize continually into the pulmonary arterial circulation, and occlude and narrow elastic pulmonary arteries causing chronic thromboembolic pulmonary hypertension (CTEPH). Pulmonary thromboendarterectomy (PTE) is potentially curative in CTEPH, but has not been previously reported in the setting of mediastinal and chest wall venous malformations. We report the case of a 21-year-old female with such a large malformation treated successfully with PTE. The patient underwent complete endovascular reconstruction of her subclavian vein system from the axillary vein to the innominate vein stump with covered stent grafts to exclude the malformations from causing recurrent pulmonary emboli. This was followed by embolization of the malformation to allow for the surgical approach. The series of events in this case serves as a novel approach in managing such rare patients.

Predictors of Successful Downstaging of Hepatocellular Carcinoma Outside Milan Criteria.

BACKGROUND: Patients with hepatocellular carcinoma (HCC) outside Milan criteria (MC) may be candidates for liver transplantation (LT) after successful downstaging. Factors that predict successful downstaging are unclear. We aimed to identify the predictors of successful downstaging of HCC in patients outside MC. METHODS: We performed a retrospective cohort study on consecutive patients with HCC outside MC who received downstaging with locoregional therapy. Clinical and laboratory variables, tumor characteristics including total tumor volume (TTV) and up-to-7 criteria were recorded. We performed univariate and multivariate logistic regression analyses to identify variables associated with successful downstaging. RESULTS: Of 675 patients with HCC, 90 patients outside MC received downstaging. Fifty-three (59%) patients were successfully downstaged, 37 (41%) failed downstaging. University of California at San Francisco criteria, α-fetoprotein, up-to-7 criteria, TTV, and platelet count were predictors of successful downstaging on univariate analysis. Total tumor volume was an independent predictor of successful downstaging on multivariate logistic regression (P = 0.04, area under receiver operating characteristic curve 0.89 (95% confidence interval, 0.82-0.96). Fifty-two (76%) of 68 patients with TTV less than 200 cm were successfully downstaged, whereas only 1 (4.5%) of 22 patients with TTV greater than 200 cm were successfully downstaged. Forty-five (50%) patients underwent LT. Kaplan-Meier survival rates at 1 and 5 years post-LT were 95.3% and 79.4%, respectively. Patients who were successfully downstaged had better survival than patients who failed downstaging (P < 0.01). CONCLUSIONS: Total tumor volume is a good predictor of successful downstaging of HCC. Patients with TTV less than 200 cm may be considered good candidates for downstaging. Further studies with larger cohort of patients are needed to validate this approach in patients with HCC outside Milan.

Penetration of Celect inferior vena cava filters: retrospective review of CT scans in 265 patients.

OBJECTIVE: The purpose of this study is to retrospectively evaluate the prevalence and extent of Celect inferior vena cava (IVC) filter penetration. MATERIALS AND METHODS: All patients with Celect filters who underwent CT between 2007 and 2012 were assessed for penetration and related complications. RESULTS: Of the 690 patients with Celect filters placed at our institution, 265 underwent CT for various reasons. The mean (SD) interval between filter placement and last CT was 167.8±264.8 days (median, 56 days; range, 0-1592 days). Penetration of primary leg was observed in 39% (95% CI, 29-51%) of patients within 30 days and 80% (95% CI, 70-87%) of patients within 90 days after placement. The mean number of penetrated legs per patient was 1.8 at 30 days and 2.1 at 90 days after placement. Penetration into adjacent organs occurred in 35 of 265 (13.2%) filters (in 45 IVC filter limbs); penetration into two structures occurred with 10 filters. The sites involved were the duodenum (n=22), aorta (n=9), psoas muscle (n=4), vertebral body (n=3), pancreas (n=2), adrenal gland (n=1), liver (n=1), right kidney (n=1), lymph node (n=1), and diaphragm (n=1). One patient presented with abdominal pain related to penetration. CONCLUSION: This study confirms a high penetration rate for Celect IVC filters and shows that CT can characterize the extent of leg penetration. Most cases of penetration were asymptomatic, but the likelihood of penetration increased over time.

Nonvascular and portal vein applications of cone-beam computed tomography: current status.

C-arm cone-beam computed tomography (CBCT) is a relatively new imaging technology that uses a conical-shaped radiation beam and a 2-dimensional flat-panel detector to produce 3-dimensional volumetric datasets with excellent spatial resolution. Recently, this technology has been implemented in angiographic units across the country. This imaging modality is particularly useful when both images of "CT-like" quality and real-time fluoroscopic imaging are required for pretreatment planning and intraprocedural guidance. In this article, we describe the use of cone-beam CT technology in various nonvascular and portal venous interventions, including percutaneous vertebroplasty or kyphoplasty, transjugular intrahepatic portosystemic shunt, percutaneous needle biopsy and ablation of pulmonary nodules and renal masses, gastrostomy tube insertion, hepatic radiofrequency ablation, and biliary interventions.

Lung dose calculation with SPECT/CT for 9°Yittrium radioembolization of liver cancer.

PURPOSE: To propose a new method to estimate lung mean dose (LMD) using technetium-99m labeled macroaggregated albumin ((99m)Tc-MAA) single photon emission CT (SPECT)/CT for (90)Yttrium radioembolization of liver tumors and to compare the LMD estimated using SPECT/CT with clinical estimates of LMD using planar gamma scintigraphy (PS). METHODS AND MATERIALS: Images of 71 patients who had SPECT/CT and PS images of (99m)Tc-MAA acquired before TheraSphere radioembolization of liver cancer were analyzed retrospectively. LMD was calculated from the PS-based lung shunt assuming a lung mass of 1 kg and 50 Gy per GBq of injected activity shunted to the lung. For the SPECT/CT-based estimate, the LMD was calculated with the activity concentration and lung volume derived from SPECT/CT. The effect of attenuation correction and the patient's breathing on the calculated LMD was studied with the SPECT/CT. With these effects correctly taken into account in a more rigorous fashion, we compared the LMD calculated with SPECT/CT with the LMD calculated with PS. RESULTS: The mean dose to the central region of the lung leads to a more accurate estimate of LMD. Inclusion of the lung region around the diaphragm in the calculation leads to an overestimate of LMD due to the misregistration of the liver activity to the lung from the patient's breathing. LMD calculated based on PS is a poor predictor of the actual LMD. For the subpopulation with large lung shunt, the mean overestimation from the PS method for the lung shunt was 170%. CONCLUSIONS: A new method of calculating the LMD for TheraSphere and SIR-Spheres radioembolization of liver cancer based on (99m)Tc-MAA SPECT/CT is presented. The new method provides a more accurate estimate of radiation risk to the lungs. For patients with a large lung shunt calculated from PS, a recalculation of LMD based on SPECT/CT is recommended.

Comparative analysis of the safety and efficacy of transcatheter arterial chemoembolization and yttrium-90 radioembolization in patients with unresectable hepatocellular carcinoma.

PURPOSE: To compare retrospectively the safety and efficacy of yttrium-90 ((90)Y) radioembolization with the safety and efficacy of chemoembolization in patients with unresectable hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Survival and complication rates were evaluated for patients with HCC who underwent chemoembolization or radioembolization at a single institution between August 2007 and April 2010. Complications were graded according to a standardized grading system for embolization procedures. Survival was determined via the Kaplan-Meier method, and multivariable analysis for factors affecting survival was performed. RESULTS: This study included 73 patients with HCC who underwent index embolization with radioembolization (n = 38; 52.1%) or chemoembolization (n = 35; 47.9%). The two patient populations were similar in terms of demographics, etiology of cirrhosis, functional status, tumor characteristics, Child-Pugh class, previous liver-directed therapy, and number of patients with bilirubin > 2.0 mg/dL. There was no significant difference in survival between the radioembolization (median 8.0 months) and chemoembolization (median 10.3 months) cohorts (P = .33). Postembolization syndrome was significantly more severe in patients who underwent chemoembolization, which led to increased total hospitalization rates in these patients. The rates of other complications and rehospitalization were similar between groups. Increased age, Child-Pugh class B, hepatitis seropositivity, bilobar tumor distribution, tumor vascular invasion, and presence of extrahepatic metastases were associated with reduced patient survival. CONCLUSIONS: Patients treated with radioembolization did not show a survival advantage over patients treated with chemoembolization. However, patients who underwent chemoembolization had significantly higher rates of hospitalization as a result of postembolization syndrome.