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

Deformable motion compensation in interventional cone-beam CT with a context-aware learned autofocus metric

PURPOSE

Interventional Cone-Beam CT (CBCT) offers 3D visualization of soft-tissue and vascular anatomy, enabling 3D guidance of abdominal interventions. However, its long acquisition time makes CBCT susceptible to patient motion. Image-based autofocus offers a suitable platform for compensation of deformable motion in CBCT, but it relies on handcrafted motion metrics based on first-order image properties and that lack awareness of the underlying anatomy. This work proposes a data-driven approach to motion quantification via a learned, context-aware, deformable metric,VI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ , that quantifies the amount of motion degradation as well as the realism of the structural anatomical content in the image.

METHODS

The proposedVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ was modeled as a deep convolutional neural network (CNN) trained to recreate a reference-based structural similarity metric-visual information fidelity (VIF). The deep CNN acted on motion-corrupted images, providing an estimation of the spatial VIF map that would be obtained against a motion-free reference, capturing motion distortion, and anatomic plausibility. The deep CNN featured a multi-branch architecture with a high-resolution branch for estimation of voxel-wise VIF on a small volume of interest. A second contextual, low-resolution branch provided features associated to anatomical context for disentanglement of motion effects and anatomical appearance. The deep CNN was trained on paired motion-free and motion-corrupted data obtained with a high-fidelity forward projection model for a protocol involving 120 kV and 9.90 mGy. The performance ofVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ was evaluated via metrics of correlation with ground truth VIF ${\bm{VIF}}$ and with the underlying deformable motion field in simulated data with deformable motion fields with amplitude ranging from 5 to 20 mm and frequency from 2.4 up to 4 cycles/scan. Robustness to variation in tissue contrast and noise levels was assessed in simulation studies with varying beam energy (90-120 kV) and dose (1.19-39.59 mGy). Further validation was obtained on experimental studies with a deformable phantom. Final validation was obtained via integration ofVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ on an autofocus compensation framework, applied to motion compensation on experimental datasets and evaluated via metric of spatial resolution on soft-tissue boundaries and sharpness of contrast-enhanced vascularity.

RESULTS

The magnitude and spatial map ofVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ showed consistent and high correlation levels with the ground truth in both simulation and real data, yielding average normalized cross correlation (NCC) values of 0.95 and 0.88, respectively. Similarly,VI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ achieved good correlation values with the underlying motion field, with average NCC of 0.90. In experimental phantom studies,VI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ properly reflects the change in motion amplitudes and frequencies: voxel-wise averaging of the localVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ across the full reconstructed volume yielded an average value of 0.69 for the case with mild motion (2 mm, 12 cycles/scan) and 0.29 for the case with severe motion (12 mm, 6 cycles/scan). Autofocus motion compensation usingVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ resulted in noticeable mitigation of motion artifacts and improved spatial resolution of soft tissue and high-contrast structures, resulting in reduction of edge spread function width of 8.78% and 9.20%, respectively. Motion compensation also increased the conspicuity of contrast-enhanced vascularity, reflected in an increase of 9.64% in vessel sharpness.

CONCLUSION

The proposedVI F D L ${\bm{VI}}{{\bm{F}}}_{DL}$ , featuring a novel context-aware architecture, demonstrated its capacity as a reference-free surrogate of structural similarity to quantify motion-induced degradation of image quality and anatomical plausibility of image content. The validation studies showed robust performance across motion patterns, x-ray techniques, and anatomical instances. The proposed anatomy- and context-aware metric poses a powerful alternative to conventional motion estimation metrics, and a step forward for application of deep autofocus motion compensation for guidance in clinical interventional procedures.

Angiography with cone-beam CT versus contrast-enhanced MRI for living donor transplant imaging: Is MRI enough?

The purpose of this study is to compare the subjective and objective quality and confidence between conventional angiography with cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI) for the preoperative evaluation of potential donors for living donor liver transplant. Seventeen patients undergoing preoperative donor evaluation for living donor liver transplantation that underwent angiography with CBCT and contrast-enhanced MRI for evaluation of hepatic vascular anatomy were included in the study. Four attending radiologists interpreted anonymized, randomized angiography with CBCT images and MRIs, rating the diagnostic quality and confidence of their interpretation (on a 3-point scale) for each element, as well as clinically relevant measurements. Overall, the readers rated the quality of angiography with CBCT to be higher than that of MRI (median [interquartile range] = 3 (2, 3) vs. 2 (1-3), p < 0.001) across all patients. Readers of angiography with CBCT had more confidence in their interpretations as an average of all elements evaluated than the MRI readers (3 (3) vs. 3 (2, 3), p < 0.001). When the same reader interpreted both MRI and CBCT, the right hepatic artery diameter (3.8 mm ± 0.72 mm vs. 4.5 mm ± 1.2 mm, p < 0.005) and proper hepatic artery diameter (4.43 mm ± 0.98 mm vs. 5.4 mm ± 1.05 mm, p < 0.003) were significantly different between MRI and CBCT. There was poor interrater reliability for determining segment IV arterial supply for both modalities (κ < 0.2). Angiography with CBCT provides higher subjective diagnostic quality and greater radiologist confidence than MRI. The difference in measurements between CBCT and MRI when the same reader reads both studies suggests CBCT adds additional information over MRI evaluation alone.

Cone-beam computed tomography-assisted percutaneous gastrostomy tube insertion in children with challenging anatomy

BACKGROUND

Percutaneous radiological gastrostomy tube insertion is a common procedure in children. An approach using ultrasound and fluoroscopy may not be feasible in patients with challenging anatomy; therefore, advanced techniques or other imaging modalities may be required.

OBJECTIVE

To describe our experience using cone-beam computed tomography (CT)-assisted percutaneous gastrostomy insertion in pediatric patients with challenging anatomy.

MATERIALS AND METHODS

A retrospective review was performed in children who underwent cone-beam CT-assisted percutaneous radiologic gastrostomy between January 2015 and July 2019. Indications, technique, outcomes, complications, and radiation dose (reference-point air kerma, air kerma area product) were assessed through chart and imaging review. Descriptive statistics only were used.

RESULTS

Twenty-seven procedures were attempted in 26 patients. Reasons for utilizing cone-beam CT guidance were high-positioned stomach (n = 10), interposing bowel loops and liver (n = 19), omphalocele (n = 1), severe scoliosis (n = 1), and ventriculoperitoneal shunt (n = 1). Technical success was 85% (23/27). Mean procedure time was 96 min (range 50-131 min). No safe access route into the stomach was encountered in four patients; three were referred for surgical gastrostomy and one had a successful re-attempt. Radiation dose data was obtained from 19 procedures (17 successful) with a total dose in successful procedures ranging from 8.1 to 63.6 mGy (average 26.2 mGy, median 24.9 mGy). The number of cone-beam CT acquisitions per procedure ranged from 1 to 4. Major complication frequency was 11% (3/27) (bleeding, peritonitis, and aspiration pneumonia); minor complication frequency was 3.7% (1/27).

CONCLUSION

This study shows that cone-beam CT guidance can be useful for assisting percutaneous radiologic gastrostomy in children with challenging anatomy.

Reference-free learning-based similarity metric for motion compensation in cone-beam CT

Purpose. Patient motion artifacts present a prevalent challenge to image quality in interventional cone-beam CT (CBCT). We propose a novel reference-free similarity metric (DL-VIF) that leverages the capability of deep convolutional neural networks (CNN) to learn features associated with motion artifacts within realistic anatomical features. DL-VIF aims to address shortcomings of conventional metrics of motion-induced image quality degradation that favor characteristics associated with motion-free images, such as sharpness or piecewise constancy, but lack any awareness of the underlying anatomy, potentially promoting images depicting unrealistic image content. DL-VIF was integrated in an autofocus motion compensation framework to test its performance for motion estimation in interventional CBCT.Methods. DL-VIF is a reference-free surrogate for the previously reported visual image fidelity (VIF) metric, computed against a motion-free reference, generated using a CNN trained using simulated motion-corrupted and motion-free CBCT data. Relatively shallow (2-ResBlock) and deep (3-Resblock) CNN architectures were trained and tested to assess sensitivity to motion artifacts and generalizability to unseen anatomy and motion patterns. DL-VIF was integrated into an autofocus framework for rigid motion compensation in head/brain CBCT and assessed in simulation and cadaver studies in comparison to a conventional gradient entropy metric.Results. The 2-ResBlock architecture better reflected motion severity and extrapolated to unseen data, whereas 3-ResBlock was found more susceptible to overfitting, limiting its generalizability to unseen scenarios. DL-VIF outperformed gradient entropy in simulation studies yielding average multi-resolution structural similarity index (SSIM) improvement over uncompensated image of 0.068 and 0.034, respectively, referenced to motion-free images. DL-VIF was also more robust in motion compensation, evidenced by reduced variance in SSIM for various motion patterns (σDL-VIF = 0.008 versusσgradient entropy = 0.019). Similarly, in cadaver studies, DL-VIF demonstrated superior motion compensation compared to gradient entropy (an average SSIM improvement of 0.043 (5%) versus little improvement and even degradation in SSIM, respectively) and visually improved image quality even in severely motion-corrupted images.Conclusion: The studies demonstrated the feasibility of building reference-free similarity metrics for quantification of motion-induced image quality degradation and distortion of anatomical structures in CBCT. DL-VIF provides a reliable surrogate for motion severity, penalizes unrealistic distortions, and presents a valuable new objective function for autofocus motion compensation in CBCT.

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.

Portal Vein Embolization Using N-Butyl Cyanoacrylate-Glue: What Impact Does a Central Vascular Plug Have?

Purpose

To examine if the addition of a central vascular plug (CVP) to portal vein embolization (PVE) with N-butyl cyanoacrylate-glue (NBCA) increases future liver remnant (FLR) growth.

Material and Methods

This is a single-center retrospective study of 115 consecutive patients with colorectal liver metastases undergoing PVE in 2013–2019. All patients were embolized with NBCA as the main embolic agent. In 2017–2019 NBCA was combined with a CVP in the central part of the right portal vein. Growth of the FLR and standardized FLR (sFLR) including degree of hypertrophy (DH) and kinetic growth rate (KGR) were analyzed, as well as procedure data such as use of cone-beam CT (CBCT), dose area product (DAP), fluoroscopy time and contrast dose.

Results

A total of 40 patients (35%) underwent PVE with a combination of CVP and NBCA. The DH was higher in these patients after 4 weeks, mean 13.6% (SD 7.8) vs. 10.5% (SD 6.4; p = 0.022), verified in multivariate analysis (coefficient 4.1, p = 0.015). A CVP did not significantly increase the resection rate (90% vs 82%, p = 0.4). Cone beam CT was used in 65 patients (57%). Use of CBCT did not affect FLR growth, and fluoroscopy time and contrast doses were not different in patients having a CBCT or not. Slightly lower DAP (median 3375 vs. 4499 cGy*cm²; p = 0.09) was seen in procedures where CBCT was used.

Conclusion

A CVP in addition to NBCA embolization was associated with increased growth of the FLR compared to NBCA alone.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00270-021-03014-w.

Use of Virtual Target Fluoroscopic Display of Three-Dimensional CO2 Wedged Hepatic Vein Portography for TIPS Placement

PURPOSE

To describe and evaluate an image fusion technique for the portal vein puncture guidance during TIPS procedure: a three-dimensional (3D) virtual target fluoroscopic display obtained with an automated 3D carbon dioxide wedged hepatic vein portography (3D CO₂-WHVP).

MATERIALS AND METHODS

All the 37 TIPS creations performed in our institution between 3/2017 and 12/2018 were retrospectively reviewed. Seventeen procedures were guided using the 3D CO₂-WHVP technique (group 1) and were compared with the other 20 procedures performed under conventional 2D fluoroscopic guidance (group 2). Image acquisition for the 3D CO₂-WHVP consisted of combining a CBCT acquisition and an automatic CO₂ injection. Once located on the multiplanar reformatted images of the CBCT acquisition, the portal bifurcation was manually segmented to create a virtual target that was overlaid onto live fluoroscopy allowing a real-time 3D guidance during portal vein puncture.

RESULTS

Primary success was 100% in group1 and 95% in group2. Median intervention length, fluoroscopy time and dose area product (DAP) were, respectively, 124 min [IQR 94-137], 40 min [IQR 26-52] and 12140 cGy.cm² [IQR 10147-18495] in group 1 and 146 min [IQR 118-199], 40 min [IQR 36-60] and 13290 cGy.cm² [IQR 10138-19538] in group 2. No technical parameter was significantly different between the two groups. Intraprocedural complication rate was 0% in group 1 and 20% in group 2 (p = 0.05).

CONCLUSION

Three-dimensional virtual target fluoroscopic display using a CBCT-acquired CO₂ wedged portography is an effective and safe technique to ease intrahepatic puncture of the portal vein during TIPS procedures.

Cone-Beam CT-Assisted Ablation of Renal Tumors: Preliminary Results

INTRODUCTION

Renal ablation is a recognized treatment modality for small renal masses. Cone-beam CT (CBCT) has been recently used in interventional oncology as a promising new guidance device, but this technology still needs to be validated for renal ablations. We aimed to assess the technical success of CBCT applications in renal ablative treatments.

MATERIALS AND METHODS

Between March 2016 and June 2018, 14 patients (mean age 69, range 54-83, 7F, 7M) underwent 21 renal ablations for histologically proven renal cell carcinoma (RCC). All treatments were performed with ultrasound (US) and CBCT guidance under general anesthesia in a dedicated angiography room setting. CBCT was mainly used to assess needle placement and to exclude complications at the end of the procedure. In two small lesions (< 1 cm), pre-acquired CBCT was co-registered with real-time US to obtain a US-CBCT fusion image guidance for tumor ablation.

RESULTS

Whether used alone or in combination with other imaging modalities, CBCT was proven to be technically successful in all 21 procedures to guide or assist tumor ablation. A primary technical efficacy of thermal ablation was achieved in 19/21 ablations (90.1%) at 1 month. Mean procedure duration was 100.2 min (range 160-64). Mean length of hospital stay was 2 days (range 1-10 days). All patients are still under active surveillance for a mean follow-up of 14.5 months (range 4-26 months).

CONCLUSIONS

CBCT for renal ablation guidance is a viable tool. Larger series are needed to compare it to MDCT.

Management of Biliary Strictures: State-of-the-Art Review

Biliary strictures can be broadly classified as benign or malignant. Benign biliary strictures are most commonly iatrogenic in nature and are a consequence of hepatobiliary surgery. Cholangiocarcinoma and adenocarcinoma of the pancreas are the most common causes of malignant biliary obstruction. This article reviews state-of-the-art minimally invasive techniques used to manage these strictures. In addition, the roles of (a) recently introduced biodegradable biliary stents in the management of benign biliary strictures and (b) intraprocedural imaging and navigation tools, such as cone-beam CT, in percutaneous reconstruction of the biliary-enteric anastomosis are discussed.

Single injection dual phase CBCT technique ameliorates results of trans-arterial chemoembolization for hepatocellular cancer

Cone-beam CT (CBCT) application to the field of trans-arterial chemoembolization has been recently the focus of several researches. This imaging modality is performed with a rotation of the C-arm around the patient, without needs of patient repositioning. Datasets are immediately processed, obtaining volumetric CT-like images with the possibility of post-processing and reconstruction of images. Dual phase CBCT recently introduced in clinical practice consists in a first arterial acquisition followed by a delayed acquisition corresponding to a venous phase. The introduction of this feature has overcome the limit of single-phase acquisitions, allowing lesions characterization. Moreover these recent advantages have several intra-procedural implications. Detailed technical and acquisition parameters will be widely exposed in this review with particular attention to: catheter positioning, acquisition delay, injection parameters, patient positioning and contrast dilution. Comparison with standard of practice second line imaging [multidetector computer tomography (MDCT) and MDCT/arteriography] demonstrate the capability of detecting occult nodules providing some clinical implications thus potentially identifying a sub set of patients with aggressive disease behaviour. Other intra-procedural advantages of dual phase CBCT usage consist in a better tumor feeder visualization, reduction of proper DSA and fluoroscopic time, suggestion the presence of an extrahepatic parasitic feeder thus resulting in a more accurate treatment. Finally, the volumetrical intraprocedural evaluation of accumulation of embolic agent has proved to be correlate with treatment response if compared with MRI.

Diagnosis and Management of Complications from Percutaneous Biliary Tract Interventions

Complications related to percutaneous biliary tract interventions (PBTIs) can range from access site discomfort to life-threatening vascular complications. These complications are relatively uncommon, and most of them are self-limiting. However, major complications for which an increased level of patient care and/or a prolonged hospital stay are required and that may lead to death-albeit rarely-can occur. Some of the most common complications related to PBTI include pain, infection, bile leakage, and catheter blockage. These conditions can be easily recognized by using the patient's clinical history and laboratory examination results. However, the more uncommon complications, such as life-threatening hemobilia, acute pancreatitis, and catheter and stent fractures, may have nonspecific clinical manifestations, and the underlying pathologic condition may be found only when it is being sought specifically. It is important that diagnostic and interventional radiologists be aware of the wide spectrum of PBTI-related complications, as early recognition and treatment may prevent catastrophic situations. In addition, knowledge of the different treatment options is essential for guidance in interventional radiology procedures such as transarterial control of hemobilia, imaging-guided direct percutaneous embolization of pseudoaneurysms, and percutaneous treatment of catheter- and stent-related complications such as fractures. The authors review a wide spectrum of complications associated with PBTI and the percutaneous management of these conditions. They also highlight valuable lessons learned from morbidity and mortality rounds at a high-volume tertiary care center. ^©RSNA, 2017.

[Percutaneous renal ablation: Pre-, per-, post-interventional evaluation modalities and adapted management]

OBJECTIVES

Ablative treatment (AT) rise is foreseen, validation of steps to insure good proceedings is needed. By looking over the process of the patient, this study evaluates the requirements and choices needed in every step of the management.

METHODS

We searched MEDLINE^®, Embase^®, using (MeSH) words and we looked for all the studies. Investigators graded the strength of evidence in terms of methodology, language and relevance.

RESULTS

Explanations of AT proposal rather than partial nephrectomy or surveillance have to be discussed in a consultation shared by urologist and interventional radiologist. Per-procedure choices depend on predictable ballistic difficulties. High volume, proximity of the hilum or of a risky organ are in favor of general anesthesia, cryotherapy and computed tomography/magnetic resonance imaging (CT/MRI). Percutaneous approach should be privileged, as it seems as effective as the laparoscopic approach. Early and delayed complications have to be treated both by urologist and radiologist. Surveillance by CT/MRI insure of the lack of contrast-enhanced in the treated area. Patients and tumors criteria, in case of incomplete treatment or recurrence, are the key of the appropriate treatment: surgery, second session of AT, surveillance.

CONCLUSION

AT treatments require patient's comprehension, excellent coordination of the partnership between urologist and radiologist and relevant choices during intervention.

Portal Venous Interventions: State of the Art

In recent decades, there have been numerous advances in the management of liver cancer, cirrhosis, and diabetes mellitus. Although these diseases are wide ranging in their clinical manifestations, each can potentially be treated by exploiting the blood flow dynamics within the portal venous system, and in some cases, adding cellular therapies. To aid in the management of these disease states, minimally invasive transcatheter portal venous interventions have been developed to improve the safety of major hepatic resection, to reduce the untoward effects of sequelae from end-stage liver disease, and to minimize the requirement of exogenously administered insulin for patients with diabetes mellitus. This state of the art review therefore provides an overview of the most recent data and strategies for utilization of preoperative portal vein embolization, transjugular intrahepatic portosystemic shunt placement, balloon retrograde transvenous obliteration, and islet cell transplantation.

Usefulness of intra-procedural cone-beam computed tomography in modified balloon-occluded retrograde transvenous obliteration of gastric varices

AIM: To evaluate whether intra-procedural cone-beam computed tomography (CBCT) performed during modified balloon-occluded retrograde transvenous obliteration (mBRTO) can accurately determine technical success of complete variceal obliteration.

METHODS: From June 2012 to December 2014, 15 patients who received CBCT during mBRTO for treatment of portal hypertensive gastric variceal bleeding were retrospectively evaluated. Three-dimensional (3D) CBCT images were performed and evaluated prior to the end of the procedure, and these were further analyzed and compared to the pre-procedure contrast-enhanced computed tomography to determine the technical success of mBRTO including: Complete occlusion/obliteration of: (1) gastrorenal shunt (GRS); (2) gastric varices; and (3) afferent feeding veins. Post-mBRTO contrast-enhanced CT was used to confirm the accuracy and diagnostic value of CBCT within 2-3 d.

RESULTS: Intra-procedural 3D-CBCT images were 100% accurate in determining the technical success of mBRTO in all 15 cases. CBCT demonstrated complete occlusion/obliteration of GRS, gastric varices, collaterals and afferent feeding veins during mBRTO, which was confirmed with post-mBRTO CT. Two patients showed incomplete obliteration of gastric varices and feeding veins on CBCT, which therefore required additional gelfoam injections to complete the procedure. No patient required additional procedures or other interventions during their follow-up period (684 ± 279 d).

CONCLUSION: CBCT during mBRTO appears to accurately and immediately determine the technical success of mBRTO. This may improve the technical and clinical success/outcome of mBRTO and reduce additional procedure time in the future.

Three-dimensional C-arm CT-guided transjugular intrahepatic portosystemic shunt placement: Feasibility, technical success and procedural time

OBJECTIVES

Establishment of transjugular intrahepatic portosystemic shunts (TIPS) constitutes a standard procedure in patients suffering from portal hypertension. The most difficult step in TIPS placement is blind puncture of the portal vein. This study aimed to evaluate three-dimensional mapping of portal vein branches and targeted puncture of the portal vein.

METHODS

Twelve consecutive patients suffering from refractory ascites by liver cirrhosis were included in this retrospective study to evaluate feasibility, technical success and procedural time of C-arm CT-targeted puncture of the portal vein. As a control, 22 patients receiving TIPS placement with fluoroscopy-guided blind puncture were included to compare procedural time.

RESULTS

Technical success could be obtained in 100 % of the study group (targeted puncture) and in 95.5 % of the control group (blind puncture). Appropriate, three-dimensional C-arm CT-guided mapping of the portal vein branches could be achieved in all patients. The median number of punctures in the C-arm CT-guided study group was 2 ± 1.3 punctures. Procedural time was significantly lower in the study group (14.8 ± 8.2 min) compared to the control group (32.6 ± 22.7 min) (p = 0.02).

CONCLUSIONS

C-arm CT-guided portal vein mapping is technically feasible and a promising tool for TIPS placement resulting in a significant reduction of procedural time.

KEY POINTS

• C-arm CT-mapping of the portal vein for 3D TIPS guidance is feasible. • Targeted punctures of the portal vein by C-arm CT reduce procedural time. • A decreased number of punctures could improve patient safety.

Iatrogenic urinary tract injuries: etiology, diagnosis, and management

Iatrogenic injury to the urinary tract, including the kidneys, ureters, bladder, and urethra, is a potential complication of surgical procedures performed in or around the retroperitoneal abdominal space or pelvis. While both diagnostic and interventional radiologists often play a central and decisive role in the identification and initial management of a variety of iatrogenic injuries, discussions of these injuries are often directed toward specialists such as urologists, obstetricians, gynecologists, and general surgeons whose procedures are most often implicated in iatrogenic urinary tract injuries. Interventional radiologic procedures can also be a source of an iatrogenic urinary tract injury. This review describes the clinical presentation, risk factors, imaging findings, and management of iatrogenic renal vascular and urinary tract injuries, as well as the radiologist's role in the diagnosis, treatment, and cause of these injuries.

C-Arm Cone-Beam Volume CT in Transjugular Intrahepatic Portosystemic Shunt: Initial Clinical Experience

PURPOSE

The purpose of this study was to compare two-dimensional digital subtraction angiography (2D-DSA) with C-arm cone-beam volume computed tomography (CACT) in the evaluation of portal vein entry and shunt course during transjugular intrahepatic portosystemic shunt (TIPS) procedure.

MATERIALS AND METHODS

Between May 2010 and November 2011, 21 patients who underwent direct portography in anteroposterior and lateral projections and subsequent CACT before stent placement during TIPS creation were reviewed retrospectively. CACT images were examined for evaluation of the portal vein entry and shunt course in comparison to 2D-DSA images by two experienced interventional radiologists.

RESULTS

CACT was proven to be better than 2D-DSA in identification of the portal vein entry (P < 0.001) and intra- or extrahepatic puncture (P < 0.001). No significant difference was observed in evaluating the shunt course (P = 0.086). The portal vein entry was considered inappropriate in seven (33%) out of 21 patients; among them, four cases were due to extrahepatic puncture, and three cases were due to peripheral puncture of the portal vein which may result in stent kinking.

CONCLUSION

While 2D-DSA remains the standard imaging method to evaluate portal vein entry, shunt course, and portal vein anatomy during TIPS procedure, CACT can effectively identify the portal vein entry and assess shunt course in difficult cases intra-procedurally, hence may reduce the risk of potential life-threatening intra-abdominal hemorrhage and shunt dysfunction.

Impact of Anatomical, Procedural, and Operator Skill Factors on the Success and Duration of Fluoroscopy-Guided Transjugular Intrahepatic Portosystemic Shunt

PURPOSE

To assess the impact of anatomical, procedural, and operator skill factors on the success and duration of fluoroscopy-guided transjugular intrahepatic portoystemic shunt following standard operating procedure (SOP).

MATERIAL AND METHODS

During a 32-month period, 102 patients underwent transjugular intrahepatic portosystemic shunt creation (TIPS) by two interventional radiologists (IR) following our institutional SOP based on fluoroscopy guidance. Both demographic and procedural data were assessed. The duration of the intervention (D(Int)) and of the portal vein puncture (D(Punct)) was analyzed depending on the skill level of the IR as well as the anatomic or procedural factors.

RESULTS

In 99 of the 102 patients, successful TIPS without peri-procedural complications was performed. The mean D(Int) (IR1: 77 min; IR2: 51 min, P < 0.005) and the mean D(Punct) (IR1: 19 min; IR2: 13 min, P < 0.005) were significantly higher in TIPS performed by IR1 (with 2 years of clinical experience performing TIPS, n = 38) than by IR2 (>10 years of clinical experience performing TIPS, n = 61), (P < 0.005 both, Mann-Whitney U test). D Int showed a higher correlation with D(Punct) for IR2 (R(2) = 0.63) than for IR1 (R(2) = 0.13). There was no significant difference in the D(Punct )for both IRs with regard to the success of the wedged portography (P = 0.90), diameter of the portal vein (P = 0.60), central right portal vein length (P = 0.49), or liver function (MELD-Score before the TIPS procedure; P = 0.14).

CONCLUSION

TIPS following SOP is safe, fast, and reliable. The only significant factor for shorter D(Punct) and D(Int) was the clinical experience of the IR. Anatomic variability, successful portography, or liver function did not alter the duration or technical success of TIPS.

Impact of 3D Rotational Angiography on Liver Embolization Procedures: Review of Technique and Applications

In the last years, the interest into interventional applications of C-arm cone-beam CT (CBCT) progressively raised, widening its clinical application from the original field of interventional neuroradiology to the field of peripheral procedures. Liver embolization procedures, due to their complexity and potential treatment-related life-threatening complications, represent one of the main clinical applications of this novel angiographic technique. CBCT has been demonstrated to render procedures safer and technically easier, and to predict outcome as well as to avoid major complications in different treatment scenarios (trans-arterial embolization, trans-arterial chemoembolization, selective internal radiation therapy, percutaneous portal vein embolization). This review summarizes all technical, dosimetric and procedural aspects of CBCT techniques, underlying all its potential clinical advantages in the field of liver embolization procedures. Moreover, the paper provides all the instructions to obtain the best diagnostic performance out of this novel angiographic technique.