Investigation of flow dynamics of primary coolant in a delay tank of a swimming pool-type nuclear reactor using radiotracer technique.

Radiotracer investigations were carried out for tracing primary coolant in a delay tank of a swimming pool type nuclear reactor. The delay tank was designed to provide a certain delay or residence time to the primary coolant so that the short-lived radioisotopes such as (nitrogen-16 and oxygen-19) decay to a safer level before exiting from the delay tank. However, soon after commissioning of the reactor, the radiation levels at the exit of the reactor core and delay tank, in the working area were found to be higher than the permissible levels. Therefore, the main objectives of the investigations were to measure breakthrough and residence times and, to investigate flow dynamics of the coolant within the tank. Residence time distributions (RTDs) of the coolant were measured in the delay tank using technetium-99m as sodium pertechnatate as a radiotracer. The breakthrough time (BTT) and mean residence time (MRT) were determined from the measured RTD and the same were found to be inadequate to allow the decay of short-lived radioisotopes to the permissible levels. Axial dispersion model with two parallel flow streams was used to simulate the measured RTD curves. Results of the model simulation indicated bypassing of the coolant. Based on the results of the radiotracer investigations, necessary modifications were carried out in the design of the tank. After implementing the modifications, the radiotracer experiments were repeated and, the BTT and the MRT were found to increase sufficient enough to allow decay of the produced radioisotopes and thus to reduce the radiation levels at the exit of the delay tank and in the working area to the safer and permissible levels.

Onyx embolization of anterior condylar confluence dural arteriovenous fistula.

The anterior condylar confluence (ACC) is a small complex venous structure located medial to the jugular vein and adjacent to the hypoglossal canal. To our knowledge, this is the first report of transvenous Onyx embolization for ACC dural arteriovenous fistula (DAVF). Three patients with ACC DAVF were treated using the Onyx liquid embolic agent with or without detachable coils. Complete angiographic obliteration of the fistulas was achieved in all cases without permanent lower cranial neuropathy. This report suggests that the controlled penetration of Onyx is advantageous in order to obliterate ACC DAVFs with a small amount of embolic material.

Disappearance of a small intracranial aneurysm as a result of vessel straightening and in-stent stenosis following use of an Enterprise vascular reconstruction device.

In-stent stenosis after stent-assisted coil embolization is a rare but well-known complication. A 32-year-old woman with an unruptured wide-necked left internal carotid artery (ICA) terminus aneurysm and an ipsilateral very small anterior choroidal artery aneurysm underwent stent-assisted coil embolization for the ICA terminus aneurysm. The 4-month follow-up angiography revealed diffuse in-stent stenosis and disappearance of the untreated anterior choroidal artery aneurysm, retaining the patency of the anterior choroidal artery. To our knowledge, this is the first report to demonstrate the course of in-stent stenosis and disappearance of an untreated small intracranial aneurysm as a result. We report this unique case and discuss the interesting mechanism underlying this phenomenon, and also provide a review of the relevant literature.

Successful treatment of extensive cerebral venous sinus thrombosis using a combined approach with Penumbra aspiration system and Solitaire FR retrieval device.

We present a young woman with rapidly progressive neurologic decline in the setting of malignant cerebral edema due to extensive superior sagittal sinus thrombosis and cortical venous thrombosis despite intravenous heparin administration. Complete revascularization of the occluded sinus was achieved using suction thrombectomy with the 5 max Penumbra catheter in combination with the Solitaire FR clot retrieval device. The successful endovascular treatment halted the progression of her cerebral edema, and the patient eventually had an excellent recovery after prolonged intensive medical therapy. To our knowledge, this is the first reported case describing such a combined mechanical approach for cerebral venous sinus thrombosis. The clot retrieval properties of the Solitaire device combined with direct aspiration via the newest generation Penumbra catheters may allow more rapid, safe and efficient revascularization than all previously reported endovascular treatments for this potentially devastating condition.

Successful treatment of extensive cerebral venous sinus thrombosis using a combined approach with Penumbra aspiration system and Solitaire FR retrieval device.

We present a young woman with rapidly progressive neurologic decline in the setting of malignant cerebral edema due to extensive superior sagittal sinus thrombosis and cortical venous thrombosis despite intravenous heparin administration. Complete revascularization of the occluded sinus was achieved using suction thrombectomy with the 5 max Penumbra catheter in combination with the Solitaire FR clot retrieval device. The successful endovascular treatment halted the progression of her cerebral edema, and the patient eventually had an excellent recovery after prolonged intensive medical therapy. To our knowledge, this is the first reported case describing such a combined mechanical approach for cerebral venous sinus thrombosis. The clot retrieval properties of the Solitaire device combined with direct aspiration via the newest generation Penumbra catheters may allow more rapid, safe and efficient revascularization than all previously reported endovascular treatments for this potentially devastating condition.

Onyx embolization of anterior condylar confluence dural arteriovenous fistula.

The anterior condylar confluence (ACC) is a small complex venous structure located medial to the jugular vein and adjacent to the hypoglossal canal. To our knowledge, this is the first report of transvenous Onyx embolization for ACC dural arteriovenous fistula (DAVF). Three patients with ACC DAVF were treated using the Onyx liquid embolic agent with or without detachable coils. Complete angiographic obliteration of the fistulas was achieved in all cases without permanent lower cranial neuropathy. This report suggests that the controlled penetration of Onyx is advantageous in order to obliterate ACC DAVFs with a small amount of embolic material.

Disappearance of a small intracranial aneurysm as a result of vessel straightening and in-stent stenosis following use of an Enterprise vascular reconstruction device.

In-stent stenosis after stent-assisted coil embolization is a rare but well-known complication. A 32-year-old woman with an unruptured wide-necked left internal carotid artery (ICA) terminus aneurysm and an ipsilateral very small anterior choroidal artery aneurysm underwent stent-assisted coil embolization for the ICA terminus aneurysm. The 4-month follow-up angiography revealed diffuse in-stent stenosis and disappearance of the untreated anterior choroidal artery aneurysm, retaining the patency of the anterior choroidal artery. To our knowledge, this is the first report to demonstrate the course of in-stent stenosis and disappearance of an untreated small intracranial aneurysm as a result. We report this unique case and discuss the interesting mechanism underlying this phenomenon, and also provide a review of the relevant literature.

Trans-radial embolization of epistaxis in patients with end-stage liver disease.

INTRODUCTION: Endovascular treatment of epistaxis in patients with bleeding disorders is challenging due to the intrinsic risk of hemorrhagic complication related to the arterial access. We describe the use of trans-radial approach for the endovascular embolization of epistaxis due to end-stage liver disease and resultant severe coagulopathy. METHODS: Two patients waiting for liver transplant continued to have epistaxis despite the aggressive correction of the coagulopathy and nose packing. After performing the Allen's test, trans-radial embolization of the epistaxis was performed in both patients. RESULTS: The complete cessation of epistaxis was achieved after the trans-radial embolization of bilateral maxillary arteries with particles. The radial access sites were manually compressed for 1 h, followed by a compression dressing for 12 h. The cessation of the epistaxis helped the subsequent treatment of correcting the coagulopathy. There was no complication related to the arterial puncture. CONCLUSION: Trans-radial embolization for epistaxis was a safe and effective method for the patient with end-stage liver disease and resultant severe coagulopathy.

Neuroimaging in pediatric epilepsy: a multimodality approach.

Pediatric patients with intractable epilepsy represent a challenging clinical population. However, recent advances in neuroimaging with a multimodality imaging approach that combines fluorine 18 fluorodeoxyglucose positron emission tomography, magnetoencephalography, diffusion tensor imaging, and magnetic source imaging with conventional magnetic resonance imaging continue to improve diagnosis and treatment in affected patients. These advances are increasing the understanding of the underlying disease process and improving the ability to noninvasively detect epileptogenic foci that in the past went undetected and whose accurate localization is crucial for a good outcome following surgical resection.

Acute renal failure after uterine artery embolization.

Renal failure is a potential complication of any endovascular procedure using iodinated contrast, including uterine artery embolization (UAE). In this report we present a case of acute renal failure (ARF) following UAE performed as a treatment for uterine fibroids. The likely causes of ARF in this patient are explored and the possible etiologies of renal failure in patients undergoing UAE are reviewed.

Rapid cognitive decline following lumbar puncture in a patient with a dural arteriovenous fistula.

BACKGROUND: Dural arteriovenous fistulas (DAVFs) are frequently accompanied with raised intracranial pressure and clinical findings suggestive of pseudotumor cerebri. However, unlike pseudotumor cerebri, the clinical response to lumbar cerebrospinal fluid (CSF) removal can vary from beneficial to acute clinical deterioration leading to death. The criteria for the safe use of lumbar puncture (LP) in patients with a DAVF are not well established. METHODS: A 61-year-old man presented with visual difficulty. Magnetic resonance imaging (MRI) and angiography revealed a left transverse sinus DAVF. He underwent multiple embolizations of arterial feeders over 3 years. He was then noted to have cognitive deficits in short term memory, listening, and concentrating. Over several days after an LP he became increasingly lethargic but arousable. Within hours after a repeat LP there was a rapid deterioration in the patient's level of consciousness and he became unarousable. RESULTS: A brain MRI revealed extensive dilated cortical veins and left temporal lobe venous ischemia without tonsillar herniation. A cerebral angiogram showed an extensive left transverse sinus DAVF with an occluded lateral transverse sinus and increased retrograde venous drainage. Embolization of the arterial feeders in combination with trans-venous coil embolization of the left transverse sinus reversed the patient's neurologic decline. He was discharged neurologically intact except for his chronic visual acuity problems. CONCLUSION: We speculate that when a DAVF manifests retrograde venous flow sufficient to cause cognitive deficits, lumbar CSF drainage must be undertaken with extreme caution.

Infrapopliteal angioplasty.

Endovascular therapy for infrapopliteal vascular disease is gaining acceptance as there is growing evidence demonstrating its safety and effectiveness. It is most commonly used to treat patients with chronic critical limb ischemia (CLI) for limb salvage and wound healing. Its use to treat lifestyle altering claudication remains controversial. For the treatment of CLI, limb salvage rates with infrapopliteal percutaneous transluminal angioplasty (PTA) are high enough that these techniques are offering an alternative to bypass surgery. Current patency rates from infrapopliteal PTA can be improved further by proper patient selection, ensuring straight-line flow to the foot in at least one tibial vessel, and close patient surveillance for early reintervention. Possible future advances including the use of drug-eluting stents, cutting balloons, and aggressive antiplatelet regimens are being tested to improve clinical outcomes following endovascular interventions on the tibial arteries.