Transjugular intrahepatic portosystemic shunt placement: portal vein puncture guided by 3D/2D image registration of contrast-enhanced multi-detector computed tomography and fluoroscopy

Transjugular intrahepatic portosystemic shunt (TIPS) is a highly effective standard procedure to reduce the portosystemic pressure gradient in patients suffering from complications of portal hypertension such as ascites and variceal bleeding [1‐7]. The most challenging and a time-consuming steps during the TIPS procedures are the catheterization of the appropriate hepatic vein and the puncture of the portal vein under fluoroscopic guidance. Technical complications during TIPS procedures are associated with off-target punctures causing injury of the liver arteries and the biliary tract or perforation of the liver capsule potentially leading to arterioportal or biliary-portal fistulas, subcapsular hematoma or life-threatening intraperitoneal hemorrhage [1, 8, 9]. Moreover, a suboptimal position of the TIPS stent is associated with an increased risk for shunt dysfunction [10]. Thus, the interventionalist has to estimate the optimal needle path on pre-interventional acquired three-dimensional (3D) contrast-enhanced (CE) multi-detector computed tomography (MDCT) or magnetic resonance imaging (MRI) [11, 12]. Several guidance techniques have been reported to facilitate the portal vein puncture aiming to reduce puncture times and peri-procedural complications, which are usually affected by the experience of the interventionalist [11, 13]. Blind fluoroscopic puncture can be augmented with direct or indirect 2D visualization of the portal vein by wedged portography or transsplenic/transarterial mesenteric portography [14, 15]. The portal vein puncture can also be effectively guided by ultrasound [16]. However, an experienced sonographeur has to be involved in addition to the operator placing the TIPS. More recently, several 3D guidance techniques for TIPS placement have been reported [12, 17‐24]. Rouabah et al. described a guidance technique based on a 3D volume rendering of the portal vein generated from a contrast-enhanced MDCT Angiography (MDCTA) of the portal trunk acquired shortly before the TIPS, which was superimposed on the fluoroscopic images [19]. Tacher et al. and Luo et al. acquired an unenhanced native CACT (C-Arm Computed Tomography) during the TIPS procedure and co-registered this with a previously acquired CE-MDCT to visualize the portal vein on fluoroscopy [20, 23]. In another study, Luo et al. introduced a guidance technique relying on intra-procedural acquisition of a CE-CACT with contrast injection in the superior mesenteric artery to obtain an indirect portomesentericography serving as an overlay [24]. Comparable to this technique are the CE-CACT-assisted guidance techniques published by Chivot et al. and Ketelsen et al. [12, 22]. Chivot et al. used an indirect wedge portography during CACT acquisition [22] and Ketelsen et al. administered the contrast media via an intravenous access and acquired the CACT in portal venous phase [12]. Another group reported on the co-registration of CE-MDCT with an unenhanced CACT and the CE-CACT with intravenous contrast injection for portal vein puncture guidance [21]. All of these techniques aim to visualize the portal vein during the intervention with a varying complexity in displaying the portalvenous anatomy and most of them need to acquire additional 3D datasets (CACT, CE-CACT or MDCTA) causing additional radiation exposure. Using the vessel information of both the hepatic and the portal veins of a CE-MDCT acquired during standard TIPS work-up might improve the portal vein puncture guidance during the intervention through a fluoroscopic registration approach. Furthermore, this might have the potential to offer a 3D guiding opportunity without the need to acquire a new (CE-) CACT or MDCTA. Therefore, the purpose of our study was to investigate the procedural characteristics, the technical success and the puncture-related complications of TIPS placement using a 3D/2D image registration of hepatic and portal veins segmented on a previously acquired CE-MDCT with two fluoroscopic images for guidance of the portal vein puncture focused on low-experienced interventionalists.

All 27 patients (59 ± 9 years, 18 men, 9 women) underwent successful TIPS placement using 3D/2D image registration of pre-procedural CE-MDCT vessel information with intra-procedural fluoroscopy for puncture guidance. The causes of portal hypertension were Budd-Chiari syndrome (3/27) and cirrhosis due to ethyltoxic liver disease (11/27), non-ethyltoxic steatohepatitis (3/27), hepatitis B (1/27), hepatitis C (2/27), hemochromatosis (1/27), re-cirrhosis after orthotopic liver transplantation (2/27) and cryptogenic cirrhosis (4/27). The indications for TIPS were recurrent or refractory variceal or gastrointestinal bleeding (6/27) and refractory ascites or hydrothorax (21/27). Additional procedures were performed in 10 patients with placement of a second stent graft to extend the previously placed stent graft in two patients and variceal embolization in eight patients. Technical success was achieved in all patients with the significant reduction of the PSG (15 ± 3 mmHg to 4 ± 3 mmHg; p < 0.0001). No clinical significant complication occurred and no patient died because of TIPS placement. Data are summarized in Table 1. The procedural characteristics included a mean HVCT of 14 ± 11 min, a PT of 14 ± 6 min and an OPT of 64 ± 29 min. A FT of 21 ± 12 min was recorded. The median number of DSA series was 4 with a range from 3 to 6. The mean overall DAP was 107.48 ± 93.84 Gy cm². For details refer to Table 2.

Comparing the study groups of the interventionalists with limited level of experience in TIPS placement of less than 3 years using 3D/2D registered 3D-VM (61 ± 9 years, 14 men, 8 women) or classical fluoroscopic guidance (53 ± 9 years, 21 men, 9 women), only the patient’s age was significant higher in the current study group than in the previously published cohort (p = 0.0030). Sex, BMI, primary disease, MELD score, indiciation, clinical significant complication and the amount of additional procedures were not statistically different (p_sex = 0.7665, p_BMI= 0.5651, p_MELD = 0.8892, p_{primary disease} = 1, p_indication = 0.7411, p_{clinical significant complication} = 1, p_{additional stent} = 0.4996, p_{variceal embolization} = 0.0789). Technical success was achieved in all patients with the significant reduction of the PSG under 3D/2D registered 3D-VM (27/27; 16 ± 4 mmHg to 4 ± 3 mmHg; p = 0.0419) and in 29/30 patients under classical fluoroscopic guidance (15 ± 5 mmHg to 6 ± 3 mmHg; p = 0.0026). The success rate was not statistically different between interventionalists with 3D/2D registered 3D-VM and classical fluoroscopic guidance (p_{success rate} = 1). HVCT, OPT and FT were shorter in the 3D/2D registered 3D-VM group performed by an interventionalist with less than three years of TIPS experience (12 ± 7 min vs.28 ± 18 min, p_HVCT = 0.0022; 53 ± 13 min vs. 85 ± 27 min, p_OPT = 0.0097; 16 ± 7 min vs. 27 ± 12 min; p_FT = 0.0009). However, the PT between these interventionalists was not significantly different (13 ± 6 min versus 19 ± 15 min; p_PT = 0.2905); for details refer to Table 3.

3D/2D image registration combining CE-MDCT vessel information with real-time fluoroscopy for guidance of the portal vein puncture is feasible and safe. Our 3D/2D image registration technique superimposes 3D information of the hepatic and portal veins as a 3D-VM on real-time fluoroscopy during the intervention. Therefore, 3D/2D image registered 3D-VM facilitates catheterization of the appropriate hepatic vein followed by successful 3D-guided puncture the portal vein, the most challenging step of TIPS procedures.

The demographics of our study population and the indications for TIPS placement are comparable to the recent literature on 3D-guided TIPS procedures [12, 19‐22] except for the studies by Luo et al., who included younger patients with refractory bleeding [23, 24]. In our study, the TIPS placement under guidance of the 3D/2D image registered 3D-VM was successfully performed in all cases with a significant reduction of the PSG. Moreover, no clinical significant complication occurred. This reflects the good safety profile of our approach and is in line with recent reports on guidance techniques for TIPS placement [12, 19‐21, 23, 24].

Reviewing the procedural characteristics, the overall mean PT of 14 ± 6 min and OPT of 64 ± 29 min in our study are short compared to the described studies on image-guided TIPS placement with PTs ranging from 14 min to 32 min [12, 19, 21, 22] and OPTs ranging from 40 min to 115 min (s. Table 2) [20‐22]. Most of the other studies on guidance techniques did not include additional procedures like variceal embolization or second stent graft placements potentially prolonging the OPT of our study (s. Table 1) [19‐22]. A major reason for the longer OPTs in the previous studies without performing additional procedures might be the time needed for the acquisition of the additional CACT and the quite complex post-processing/reconstruction of the image fusion algorithms used in these studies. For example, Luo et al. performed an additional arterial puncture and catheterization of the superior mesenteric artery for the acquisition of a CE-CACT during an indirect portography [24]. Rouabah et al. needed a relatively long post-processing time for a complex 3D-reconstruction of the portal trunk from an additionally acquired MDCTA [19]. Of note, the MDCTA in the study by Rouabah et al. was additionally acquired for the purpose of portal vein segmentation and overlay. Both studies reported on an average of 15 min for “3D-overlay-readiness” [19, 24], which obviously prolonged their TIPS procedure. In our study, the generation of the centerlines within the hepatic vein and the portal vein on the portalvenous CE-MCDT, the acquisition of two fluoroscopic images in perpendicular views and the superimposition of the 3D-VM on the fluoroscopy takes approximately 3-5 min. The overall mean and median DAP in our study were 107.48 Gy cm² and 61.14 Gy cm². This is clearly less than the most recent reference DAP of 446.00 Gy cm² for TIPS procedures in the U.S. [31]. In detail, the DAP in our study is 30-80% lower than the mean DAPs reported in five studies using registration-guided TIPS procedures that range from 144.2 to 563.00 Gy cm² [12, 19‐24]  (s. Table 2). The difference between our median DAP of 61.14 Gy cm² to the lowest DAP for CACT-assisted TIPS procedures of 90.75 Gy cm² reported by Tacher et al. might best be explained with the additional radiation exposure of the CACT reported to range from 18.00 to 63.90 Gy cm² [12, 21, 23]. Moreover, Tacher et al. reported on CACT acquisition with the patient’s arms placed next to the body [20]. This technique might be associated with additional radiation exposure and might be counterproductive for the accuracy of the co-registration with a CE-MDCT, which is typically acquired with the patients’s arms up.

Focusing on the interventionalist with limited experience in TIPS procedures, our mean PT of 13 min and OPT of 53 min were 30% faster using 3D/2D image registered 3D-VM compared to the reported guidance techniques in the literature (s. Table 2). This finding is underlined by the comparison of the interventionalists with limited experience performing TIPS at our hospital. We found a significant difference with a 55% lower HVCT, 35% lower OPT and 40% lower FT when using 3D/2D image registered 3D-VM. The mean PT of the interventionalist with a level of experience of less than three years using 3D/2D image registered 3D-VM was 30% shorter than the mean PT using classical fluoroscopic guidance, but the difference yielded no statistical significance. Since Marquardt et al. showed a correlation between PT and OPT [11], the short OPT in our study might at least partly be explained by the trend of a shorter PT. Another possible explanation for the short OPT using 3D/2D image registered 3D-VM might be the additional labeling of the hepatic veins, which significantly improves the catheterization time of the appropriate hepatic vein and might also support stent positioning. This might be of additional value, especially in patients with altered anatomy due to liver cirrhosis or after liver surgery or orthotopic transplantation. Of note, after successful catheterization of the right hepatic vein, it is possible to re-evaluate and to re-align a potential 3D-VM off-set using control-elements at the table-side in the angiography suite. Thus, labeling of the hepatic veins offers additional guidance which can save fluoroscopy time and radiation exposure at the beginning of the TIPS procedure when compared to approaches which require successful catheterization of the right hepatic vein prior to CACT acquisition to determine the starting point of the puncture guidance [20‐22].

In comparison to the published image guidance techniques the 3D/2D image registered 3D-VM presented here has additional advantages. By labeling the hepatic veins and the portal vein branches for a 3D-VM this approach differs from recently published image guidance techniques which are mainly focused on the portal vein [12, 19‐22, 24]. Labeling both, entry and target point as well as the distance to each other illustrates the two most important informations for puncture procedure in one real-time image/overlay. The combination of the centerline drawings in the hepatic veins and the portal vein in our 3D-VM might be more robust to changes caused by patient breathing during the procedure or paracentesis following the acquisition of the CE-MDCT. Such changes of the liver position due to paracentesis were the reason why Rouabah et al. performed an additional MDCTA of the portal trunk after patients underwent paracentesis [19]. A common approach to confirm the needle position in the appropriate hepatic vein and to visualize the portal vein branch is a wedged portography. However, this requires an additional DSA run and can be associated with severe subcapsular hematomas as reported by Chivot et al. [9, 22]. The technique to overlay both, hepatic and portal veins, renders wedged portographies or additional CACT, CE-CACT or MDCTA unnecessary. Therefore, it not only shortens the procedure workflow significantly but also reduces the potential for complications. Nevertheless, we performed wedge portographies in our study according to our standard operating procedures.

Overall, our 3D/2D image registered 3D-VM is a unique approach in using a CE-MDCT acquired during routine patient workup and planning of the TIPS placement and two fluoroscopic images in perpendicular views without the need to acquire an additional 3D dataset [12, 19‐24]. The 3D-VM provides robust information about the localization of the hepatic veins in relation to the portal vein branches, thereby displaying entry and target for a successful puncture. Our 3D/2D image registered 3D-VM seems to be beneficial for interventionalists with a low level of TIPS experience compared to classical fluoroscopic guidance and improves patient safety due to expendable wedged portography and reduces fluoroscopy and procedure time. We believe that image guidance techniques are helpful to support the training of interventional radiologists not only for TIPS placement but also for other interventional procedures (e.g., balloon pulmonary angioplasty, transarterial chemoembolization or prostatic artery embolization [29, 32, 33]. In addition, the respective handling- and software-skills are useful to facilitate even more complex image-guided interventions such as fenestrated endovascular aneurysm repair [34].

TIPS placement using the 3D/2D image registered 3D-VM is technically feasible, successful, fast and safe. It allows for an efficient use of pre-procedural CE-MDCT information during the procedure in real-time. 3D/2D image registration of the 3D-VM requires only two fluoroscopic images with minimal radiation exposure. It is a promising tool for guidance of the hepatic vein catherization and the portal vein puncture with the potential to reduce radiation exposure.