An evaluation of the Physical Properties of Current Microcatheters and Guidewires. The Development of the "Catheter-glide Approach" in Response to Weaknesses of Current Materials

[Fundamental Study of Inflation Pressure Resistance in an Angiographical Tube]

This study was designed to clarify the relation between the pressure resistance of an angiographical tube and the amount of contrast medium injected under a connected microcatheter used for interventional radiology (IVR). We investigated the injection pressure and the expansion rate at the center of the tube during contrast enhancement by setting the power injector to 1200 PSI pressure, with 2.0 ml/s injection speed, 10 ml injection volume, 5.0 s injection time, and 0 s rise time for tubes with different pressure resistance performance (low or high). Then we examined the amount of contrast medium material discharged from the microcatheter. The low-pressure resistant tube (less than 140 PSI) injection pressure exceeded the pressure performance. The expansion rate increased to 49%, presenting a risk of rupture. The injection pressure of the high-pressure resistant tube (less than 1200 PSI) was within the pressure-resistance performance. The expansion rate increased to 38%. However, when the contrast medium discharge amount contributing to the image was measured within the injection time under the condition of 10 ml injection for 5.0 s, the former was 2.3 ml and the latter was 4.2 ml. The entire amount was not discharged during the injection period. It became apparent that it is discharged in drips after some time. Results show that the tube expansion caused retention of the contrast medium inside, which decreases the actual amount of the injected contrast medium. From the results, we infer the possibility of preventing reduction of the injected contrast medium amount attributable to expansion.

A stable and real-time nonlinear elastic approach to simulating guidewire and catheter insertions based on Cosserat rod

Interventional Radiology procedures (e.g., angioplasty, embolization, stent graft placement) provide minimally invasive therapy to treat a wide range of conditions. These procedures involve the use of flexible tipped guidewires to advance diagnostic or therapeutic catheters into a patient's vascular or visceral anatomy. This paper presents a real-time physically based hybrid modeling approach to simulating guidewire insertions. The long, slender body of the guidewire shaft is simulated using nonlinear elastic Cosserat rods, and the shorter flexible tip composed of a straight, curved, or angled design is modeled using a more efficient generalized bending model. Therefore, the proposed approach efficiently computes intrinsic dynamic behaviors of guidewire interactions within vascular structures. The efficacy of the proposed method is demonstrated using detailed numerical simulations inside 3-D blood vessel structures derived from preprocedural volumetric data. A validation study compares positions of four physical guidewires deployed within a vascular phantom, with the co-ordinates of the corresponding simulated guidewires within a virtual model of the phantom. An optimization algorithm is also implemented to further improve the accuracy of the simulation. The presented simulation model is suitable for interactive virtual reality-based training and for treatment planning.

Modeling Friction, Intrinsic Curvature, and Rotation of Guide Wires for Simulation of Minimally Invasive Vascular Interventions

Obtaining the expertise to perform minimally invasive vascular interventions requires thorough training. In this paper, an algorithm for simulating minimally invasive vascular interventions for training purposes is presented and evaluated. The algorithm enables the simulation of completely straight guide wires as well as intrinsically curved ones based on applied translations and rotations. Friction between the guide wire and the vasculature is incorporated in the model. Quantitative validation is performed by comparing the simulated guide-wire position with the actual position as assessed by 3-D rotational X-ray imaging in physical experiments on a variety of vascular phantoms that truthfully represent human anatomy. The results show that for proper settings of the model's parameters, accurate simulations of guide-wire motion can be obtained, with an average precision of the guide-wire position of around 1.0 mm.

Ectatic and Occlusive Diseases of the Venous Drainage System of Cerebral Arteriovenous Malformations (AVMs) - with Emphasis on Spectacular Shrinking Neurological Deficits after Embolization

During reviewing cases with AVM, the author noticed that stenotic and occlusive changes of the draining veins are commonly seen in high flow cerebral AVMs. However, little attention has been paid to these venous diseases until ectatic veins, generated in the upstream of the venous system, cause mass effect to the surrounding structures, or redistribution and shunting toward regional veins became insufficient after they are markedly overloaded or occluded. Cases with such venous abnormality are clinically important because of the possibility of dramatic improvement of neurological deficits after embolization of AVMs. Following presenting treatment results of 177 AVM case, the author is going to present five cases with abnormality in the Galenic venous system and two cases with abnormality in cortical veins associating with high flow cerebral AVMs. Consideration will be made on symptomatology and pathophysiologic mechanism of venous abnormalities associating with high flow cerebral AVMs.

Evaluation of vascular and interventional procedures with time-action analysis: a pilot study

PURPOSE

To provide an objective method to measure the efficiency of vascular and interventional procedures.

MATERIALS AND METHODS

The time-action analysis method is defined for peripheral vascular and interventional procedures. A taxonomy of actions is defined, geared specifically toward these procedures. The actions are: start-up/wrap-up, exchange, navigate, image, diagnose, treat, handle material, wait, compress puncture site, and unclassified. The recording method and analysis techniques are described. To show the type of data that can be obtained, the time-action analysis of 30 procedures is presented.

RESULTS

The results provide a detailed picture of the time spent on various actions. Of all actions, the most time is spent on compressing the puncture site (18.5%), whereas the highest frequency of actions are for exchange of catheters, guide wires, and sheaths (20.4 times per procedure). Radiation exposure can be analyzed in detail, which can yield directions for possible reduction. For instance, 5.2%-8.3% of the total radiation exposure occurs during preparation of imaging to adjust the position of the patient table and set the image intensifier diaphragm.

CONCLUSION

Time-action analysis provides an objective measurement method to monitor and evaluate vascular and interventional procedures. Potential applications and limitations of the technique are discussed.

Diagnosis and endovascular treatment of vertebral arteriovenous fistulas in neurofibromatosis type 1

SUMMARY

We present diagnostic problems, strategies, techniques and material selection for endovascular treatment of high flow arteriovenous fistula (AVF) of tortuous and fragile vertebral artery (VA) with neurofibromatosis type 1 (NF1). Diagnosis of NF1 was easy in four of our cases because of neurofibromatosis, skin pigmentation and various skeletal abnormalities. These stigmas of NF1 were lacking in one case, and the only clue to the diagnosis was ovoid bone defects of the skull vault. Diagnosis was made by performing biopsy of scalp neurofibromas incidentally found on CT. In two initial cases, venous varix were packed with coils by transvenous approach after the transarterial embolisation failed to completely cure the fistula. In three recent cases, blood flow through the fistula was markedly reduced as an initial step by placing detachable coils into the distal and proximal stumps of the afferent VA. Then a liquid adhesive was injected under systemic hypotension to completely occlude the fistula. Control angiography revealed that the AVFs were completely occluded in all cases. Longterm angiographical and clinical status have been stable in all cases. Trying to attain complete occlusion of fistulas using detachable balloons is not an appropriate treatment option for high flow fistulas situated on markedly dilated, tortuous and fragile VAs of patients with NF1. Also, trapping of fistulas is not justified because of the numerous potential feeding pedicles, and makes the following procedure difficult.

Embolization of cerebral arteriovenous malformations with cellulose acetate polymer: a clinical, radiological, and histological study

OBJECTIVE

A cellulose acetate polymer (CAP) solution was hypothesized to be useful for the embolization of arteriovenous malformations (AVMs). To investigate this possibility, we analyzed the clinical, radiological, and histological results of patients with AVMs embolized by using a CAP solution.

METHODS

We reviewed the cases of 11 patients with AVMs treated by embolization before surgical resection. We used two types of CAP solutions, CAP-M and CAP-L, which are mixtures of 250 mg of solid CAP and 1800 or 2250 mg of bismuth trioxide dissolved in 5.5 or 7.0 ml of dimethyl sulfoxide, respectively. After the embolization procedure, percent reduction of the nidus volume was measured, and thereafter, the clinical course and computed tomographic scans and/or magnetic resonance imaging scans were evaluated. All patients underwent surgical resection 1 to 51 days after embolization. Resected specimens were stained for light microscopic examination.

RESULTS

Thirty-nine feeding vessels were embolized. The reduction rate of the nidus volume ranged from 20% to nearly 100%. Transient and persistent ischemic deficits occurred in three patients and one patient, respectively, and there were no hemorrhagic complications. All AVMs but one were completely resected by surgery. The embolized AVMs were soft enough to be easily cut and retracted. The histological examinations disclosed no or mild inflammatory reactions within 2 weeks after embolization. The internal elastic lamina was preserved in every case. Recanalization through the cast of the CAP mass was not observed until 51 days after embolization.

CONCLUSION

CAP solution is a safe and useful embolic agent for AVMs.