Ravi N. Srinivasa

Improved quantitative 90Y bremsstrahlung SPECT/CT reconstruction with Monte Carlo scatter modeling

Purpose: In 90Y microsphere radioembolization (RE), accurate post‐therapy imaging‐based dosimetry is important for establishing absorbed dose versus outcome relationships for developing future treatment planning strategies. Additionally, accurately assessing microsphere distributions is important because of concerns for unexpected activity deposition outside the liver. Quantitative 90Y imaging by either SPECT or PET is challenging. In 90Y SPECT model based methods are necessary for scatter correction because energy window‐based methods are not feasible with the continuous bremsstrahlung energy spectrum. The objective of this work was to implement and evaluate a scatter estimation method for accurate 90Y bremsstrahlung SPECT/CT imaging. Methods: Since a fully Monte Carlo (MC) approach to 90Y SPECT reconstruction is computationally very demanding, in the present study the scatter estimate generated by a MC simulator was combined with an analytical projector in the 3D OS‐EM reconstruction model. A single window (105 to 195‐keV) was used for both the acquisition and the projector modeling. A liver/lung torso phantom with intrahepatic lesions and low‐uptake extrahepatic objects was imaged to evaluate SPECT/CT reconstruction without and with scatter correction. Clinical application was demonstrated by applying the reconstruction approach to five patients treated with RE to determine lesion and normal liver activity concentrations using a (liver) relative calibration. Results: There was convergence of the scatter estimate after just two updates, greatly reducing computational requirements. In the phantom study, compared with reconstruction without scatter correction, with MC scatter modeling there was substantial improvement in activity recovery in intrahepatic lesions (from > 55% to > 86%), normal liver (from 113% to 104%), and lungs (from 227% to 104%) with only a small degradation in noise (13% vs. 17%). Similarly, with scatter modeling contrast improved substantially both visually and in terms of a detectability index, which was especially relevant for the low uptake extrahepatic objects. The trends observed for the phantom were also seen in the patient studies where lesion activity concentrations and lesion‐to‐liver concentration ratios were lower for SPECT without scatter correction compared with reconstruction with just two MC scatter updates: in eleven lesions the mean uptake was 4.9 vs. 7.1 MBq/mL (P = 0.0547), the mean normal liver uptake was 1.6 vs. 1.5 MBq/mL (P = 0.056) and the mean lesion‐to‐liver uptake ratio was 2.7 vs. 4.3 (P = 0.0402) for reconstruction without and with scatter correction respectively. Conclusions: Quantitative accuracy of 90Y bremsstrahlung imaging can be substantially improved with MC scatter modeling without significant degradation in image noise or intensive computational requirements.

Treatment of Chylous Ascites in a Child after Wilms Tumor Resection with Intranodal Injection of N-Butyl Cyanoacrylate Glue

Chylous ascites is the accumulation of chyle in the peritoneal cavity. Diagnosis is established by cytochemical analysis of the fluid and staining with Sudan III. Here we report a case of chylous ascites treated by percutaneous intranodal embolization of the disrupted lymphatic vessels with the use of n-butyl cyanoacrylate (NBCA). Institutional review board approval is not required at our institution for a brief report such as this. A 3-year-old boy presented with right-sided abdominal pain and a palpable mass. Initial imaging showed a 10-cm right renal mass with tumor thrombus extending from the right renal vein into the atrium (Fig 1). Pathologic examination confirmed the diagnosis of a Wilms tumor. Repeat imaging after 12 weeks of chemotherapy showed reduction in the size of the right renal mass and tumor thrombus. Subsequently, surgical resection was performed of the right kidney, ureter, and inferior vena cava (IVC). An exploratory laparotomy was performed on postoperative day 6 for questionable intraperitoneal hemorrhage. Three liters of milky-colored ascites was evacuated from the peritoneal cavity. Two small lymphatic vessels in the retroperitoneum were suture-ligated, and a large Vicryl mesh and layer of EVICEL Fibrin Sealant (Human) (Ethicon, Cincinnati, Ohio) was placed over the retroperitoneal dissection plane. Drains were inserted in the right and left abdomen. During the next 3 days, an average of 2,600 mL/d of milky fluid continued to drain. The interventional radiology service was consulted for possible embolization. Three days after the exploratory laparotomy, the patient was brought to the angiographic suite. Under general

Three-Dimensional Printing Facilitates Successful Endovascular Closure of a Type II Abernethy Malformation Using an Amplatzer Atrial Septal Occluder Device

Type II Abernethy malformations, characterized by side-to-side portosystemic shunting with preserved intrahepatic portal venous system, have been treated with shunt closure surgically and endovascularly. Three-dimensional printing has been used to develop highly accurate patient-specific representations for surgical and endovascular planning and intervention. This innovation describes 3-dimensional printing to successfully close a flush-oriented type II Abernethy malformation with discrepant dimensions on computed tomography, conventional venography, and intravascular ultrasound, using a 12-mm Amplatzer atrial septal occluder device.

Transsplenic endovascular recanalization and stenting of a completely occluded portal vein with jejunal variceal embolization in a pediatric liver transplant recipient

Portal vein thrombosis occurs in 1.4% of pediatric liver transplant candidates and 3.7% of liver transplant recipients. While portal vein recanalization without and with portal vein stenting has been described in adult transplant candidates and recipients, it has never been described in the pediatric transplant population. This report presents a pediatric liver transplant recipient with portal hypertension secondary to portal vein thrombosis successfully managed with transsplenic access and subsequent portal vein recanalization and stenting.

Treatment of Venous Malformations: The Data, Where We Are, and How It Is Done

Venous malformations are the most common type of congenital vascular malformation. The diagnosis and management of venous malformations may be challenging, as venous malformations may be located anywhere in the body and range from small and superficial to large and extensive lesions. There are many treatment options for venous malformations including systemic targeted drugs, open surgery, sclerotherapy, cryoablation, and laser photocoagulation. This article reviews the natural history, clinical evaluation, imaging diagnosis, and treatment modalities of venous malformations.

Endovascular Iliocaval Reconstruction for Chronic Iliocaval Thrombosis: The Data, Where We Are, and How It is Done

Iliocaval thrombosis, or thrombosis of the inferior vena cava and iliac veins, is associated with significant morbidity in the form of limb-threatening compromise from phlegmasia cerulean dolens, development of post-thrombotic syndrome, and death secondary to pulmonary embolism. Endovascular iliocaval reconstruction is an effective treatment for iliocaval thrombosis with high levels of technical success, favorable clinical outcomes and stent patency rates, and few complications. It is often able to relieve the debilitating symptoms experienced by affected patients and is a viable option for patients who fail conservative management. This article presents an approach to endovascular iliocaval stent reconstruction in patients suffering from chronic iliocaval thrombosis that takes into consideration background, patient selection and indications, timing of intervention, procedural steps, technical considerations, postprocedural care, and outcomes, along with providing schematic illustrations that serve to outline iliocaval stent reconstruction and management of chronic venous occlusions.

Laser Ablation Facilitates Closure of Chronic Enterocutaneous Fistulae

This report describes the use of laser ablation for treatment of chronic enterocutaneous fistulae (ECFs) after failure of conservative therapy. Three patients underwent laser ablation for treatment of 8 ECFs. Mean duration of fistula patency was 28 months with mean fistula output of 134 mL/day. The initial technical success was 100% with no major or minor complications. Three ECFs required repeat treatment. At mean follow-up of 53 days, 7 of the fistulae were occluded. One fistula showed a markedly reduced output of 10 mL/day.

Transjugular Intrahepatic Portosystemic Shunt Reduction Using the GORE VIATORR Controlled Expansion Endoprosthesis: Hemodynamics of Reducing an Established 10-mm TIPS to 8-mm in Diameter

To the Editor, Transjugular intrahepatic portosystemic shunt (TIPS) involves the creation of a shunt between the portal and hepatic veins to treat portal hypertension and its complications, including refractory ascites, hepatic hydrothorax, and variceal bleeding [1]. Complications, however, may result from excessive shunting of portal venous blood to the systemic circulation. 17–46% of patients present with hepatic encephalopathy (HE) following a TIPS [2–4]. Although the majority of patients with TIPS-associated HE may be medically managed, 3–7% of patients develop refractory encephalopathy as a result of this high volume shunting [2, 5–7]. TIPS reduction or occlusion may be effective in decreasing the incidence and severity of hepatic encephalopathy. Complete occlusion of the TIPS returns patients to the baseline risk of variceal bleeding and other portal hypertension complications present prior to TIPS [2, 5]. TIPS reduction has become the preferred method of treatment for excessive portal to systemic shunting of blood that is refractory to first-line medical management. The goal of TIPS reduction is to reduce the volume of shunted blood and divert it back to the intrahepatic portal veins by decreasing the diameter of the existing stent. Ideally, achieving a balance between portal and systemic blood flow to maintain the benefit of TIPS in reducing portal hypertension while concurrently treating the encephalopathy is desired. Numerous TIPS reduction methods using various stents and stent grafts have been previously detailed in the literature [5, 6]. TIPS are commonly reduced to a 6–7 mm residual diameter and usually, but not always, require complicated in vivo or backtable techniques [5, 6]. With the advent of the newly introduced Viatorr Controlled Expansion Endoprosthesis (Gore & Associates, Flagstaff, AZ, USA), there is the potential of a simple single-stent deployment for TIPS reduction leaving a residual TIPS diameter of 8 mm. Two patients with hepatic encephalopathy underwent TIPS reduction using the Viatorr Controlled Expansion Endoprosthesis (Gore) (Fig. 1). Pre and post-reduction pressures and hemodynamics were measured using a pressure transducer and a 6-French ReoCath Retrograde Flow Catheter (Transonic Systems), respectively. Mean increase in portosystemic gradient was 4 mmHg (range 2–6 mmHg) with mean percentage increase of 30.5% (range 18.1–42.8%). Mean reduction in portal vein blood flow was 222.5 mL/min (range 45–400 mL/min) with mean percentage reduction of 16.3% (range 4.6–27.9%). Mean reduction in TIPS blood flow was 187 mL/min (range 87–287 mL/min) with mean percentage reduction of 15.9% (range 12.0–19.7%). No minor or major procedural complications occurred. Mean follow-up was 81 days (range 38–124 days). Both patients showed a 1 grade improvement in HE symptoms using West Haven HE criteria. A 69-year-old male with history of alcoholic cirrhosis and portal hypertension complicated by esophageal varices and ascites had a TIPS placed 1278 days prior to presentation (Fig. 2 and Table 1). Since that time he developed & Ravi N. Srinivasa rnsriniv@med.umich.edu

Epidural Balloon Placement for Protection of the Spinal Canal During Cryoablation of Paraspinal Lesions

Ablation of paraspinal lesions close to the spinal canal and neuroforamina requires protective measures in order to protect the spinal cord and nerve roots. Various methods of protection have been previously described including infusion of saline and CO2. Regardless, neuromonitoring should be adjunctively performed when ablating spinal lesions close to neuronal structures. Balloon protection has been previously described during ablation of renal masses. The benefit of balloon protection in paraspinal mass ablation is it physically displaces the nerve roots as opposed to CO2 or saline which has the potential to insulate but because of its aerosolized or fluid nature may or may not provide definitive continuous protection throughout an ablation. This report details three paraspinal lesions, two of which were successfully ablated with the use of a balloon placed in the epidural space to provide protection to the spinal cord and nerve roots.

Transbiliary intravascular ultrasound-guided diagnostic biopsy of an inaccessible pancreatic head mass

Percutaneous image-guided biopsies of pancreatic malignancies may prove challenging and nondiagnostic due to a variety of anatomic considerations. For patients with complex post-surgical anatomy, such as a Roux-en-Y gastric bypass, diagnosis via endoscopic ultrasound with fine-needle aspiration may not be possible because of an inability to reach the proximal duodenum. This report describes the first diagnostic case of transbiliary intravascular ultrasound-guided biopsy of a pancreatic head mass in a patient with prior Roux-en-Y gastric bypass for which a diagnosis could not be achieved via percutaneous and endoscopic approaches. Transbiliary intravascular ultrasound-guided biopsy resulted in a diagnosis of pancreatic adenocarcinoma, allowing the initiation of chemotherapy.