Biomedical subjects
Publications and source records attributed to Filip Banovac.
We report the unusual case of successful endovascular exclusion of a thoracic aortic aneurysm with subsequent thoracic aortic aneurysm reduction, and development of an interval, acute type III endoleak after cardioversion 5 years after stent graft deployment.
PURPOSE: Emerging interventional radiology assistance systems that incorporate electromagnetic navigation (EMN) can help the operator guide a needle or other instrument toward a target along preplanned oblique trajectories while avoiding critical structures. A proof-of-concept study was conducted to assess the use of EMN, and EMN was compared with the standard computed tomographic (CT) fluoroscopy guidance technique. MATERIALS AND METHODS: A total of 14 needle passes, seven each with EMN and CT fluoroscopy guidance, were performed into an artificially created liver lesion of a single swine. The accuracy of needle placement for each pass was verified with a confirmatory CT scan. The total radiation dose and time of procedure was compared between the EMN and conventional CT fluoroscopy methods. RESULTS: All needle passes were successful, and all passes conducted with EMN were completed with a single insertion, whereas multiple passes (mean, 2.9) with needle repositioning were required with CT fluoroscopic guidance. Statistically significant reduction in procedure time and overall radiation dose for EMN punctures was shown. Accuracy of needle placement was statistically equivalent for the two methods. CONCLUSIONS: This proof-of-concept study shows that EMN guidance has equivalent accuracy of needle placement to conventional CT fluoroscopy-guided methods in swine. EMN is also associated with favorable radiation-dose and time-of-procedure profiles for biopsy of liver lesions. Clinical studies are needed to evaluate the safety and efficacy of this technology in the biopsy of lesions in anatomically challenging locations that require steep angles of needle insertion.
PURPOSE: To determine the indications and technical aspects of procedures in patients undergoing repeat uterine artery embolization (UAE). MATERIALS AND METHODS: At a single center, 24 patients underwent repeat embolization for recurrent or persistent symptoms. The magnetic resonance (MR) imaging findings before repeat embolization were compared with those of earlier studies. The extent of tumor infarction after the first procedure was determined, and the status of existing or new tumors before the second procedure was assessed. The angiographic studies from the initial and repeat embolization studies were reviewed and summarized. These findings were assessed with the use of summary statistics. RESULTS: Twenty-four patients underwent repeat embolization 6-66 months after the initial embolization. The most common symptom at representation was pressure and/or bulk symptoms (n=15), followed by recurrent heavy bleeding (n=12) and pelvic pain or cramping (n=7). MR imaging studies before repeat embolization revealed incomplete infarction of tumors present before the first embolization in 22 of 24 patients. New tumors were identified in 12 patients, two of whom had new tumors only. During repeat embolization, nine patients (37%) required ovarian artery embolization to occlude ovarian supply to the uterus. Among 21 women with clinical follow-up after the second embolization, 19 (90%) had symptom control. CONCLUSIONS: Repeat embolization prompted by recurrent uterine leiomyomas usually occurs in the setting of regrowth of incompletely infarcted tumors. Although ovarian embolization was often needed, on the basis of this limited experience, symptoms appear to respond well to repeat embolization.
Electromagnetic tracking has great potential for assisting physicians in precision placement of instruments during minimally invasive interventions in the abdomen, since electromagnetic tracking is not limited by the line-of-sight restrictions of optical tracking. A new generation of electromagnetic tracking has recently become available, with sensors small enough to be included in the tips of instruments. To fully exploit the potential of this technology, our research group has been developing a computer aided, image-guided system that uses electromagnetic tracking for visualization of the internal anatomy during abdominal interventions. As registration is a critical component in developing an accurate image-guided system, we present three registration techniques: 1) enhanced paired-point registration (time-stamp match registration and dynamic registration); 2) orientation-based registration; and 3) needle shape-based registration. Respiration compensation is another important issue, particularly in the abdomen, where respiratory motion can make precise targeting difficult. To address this problem, we propose reference tracking and affine transformation methods. Finally, we present our prototype navigation system, which integrates the registration, segmentation, path-planning and navigation functions to provide real-time image guidance in the clinical environment. The methods presented here have been tested with a respiratory phantom specially designed by our group and in swine animal studies under approved protocols. Based on these tests, we conclude that our system can provide quick and accurate localization of tracked instruments in abdominal interventions, and that it offers a user-friendly display for the physician.
Electromagnetic tracking systems have the potential to track instruments inside the body because they are not limited by the line of sight constraints that characterize optical tracking systems. To integrate an electromagnetic tracking device into a surgical navigation system, accurate registration is required. We present a two-stage registration mechanism designed to be more accurate than the widely used global fiducial-based registration method. The first stage uses a hybrid Iterative Closest Point (ICP) registration method and the Simulated Annealing (SA) optimization algorithm, to increase the initial registration accuracy. The second stage exploits multiple implanted tracking needles that are used to calculate the affine transform based on the initial transform information, and thereby to compensate for the deformation in real time. Phantom and swine studies have demonstrated the utility of this technique.
PURPOSE: To assess the feasibility of the use of preprocedural imaging for guide wire, catheter, and needle navigation with electromagnetic tracking in phantom and animal models. MATERIALS AND METHODS: An image-guided intervention software system was developed based on open-source software components. Catheters, needles, and guide wires were constructed with small position and orientation sensors in the tips. A tetrahedral-shaped weak electromagnetic field generator was placed in proximity to an abdominal vascular phantom or three pigs on the angiography table. Preprocedural computed tomographic (CT) images of the phantom or pig were loaded into custom-developed tracking, registration, navigation, and rendering software. Devices were manipulated within the phantom or pig with guidance from the previously acquired CT scan and simultaneous real-time angiography. Navigation within positron emission tomography (PET) and magnetic resonance (MR) volumetric datasets was also performed. External and endovascular fiducials were used for registration in the phantom, and registration error and tracking error were estimated. RESULTS: The CT scan position of the devices within phantoms and pigs was accurately determined during angiography and biopsy procedures, with manageable error for some applications. Preprocedural CT depicted the anatomy in the region of the devices with real-time position updating and minimal registration error and tracking error (<5 mm). PET can also be used with this system to guide percutaneous biopsies to the most metabolically active region of a tumor. CONCLUSIONS: Previously acquired CT, MR, or PET data can be accurately codisplayed during procedures with reconstructed imaging based on the position and orientation of catheters, guide wires, or needles. Multimodality interventions are feasible by allowing the real-time updated display of previously acquired functional or morphologic imaging during angiography, biopsy, and ablation.
Radiofrequency ablation of primary and metastatic liver tumors is becoming a potential alternative to surgical resection. We propose a novel system that uses real-time electromagnetic position sensing of the needle tip to help with precision guidance into a liver tumor. The purpose of this study was to evaluate this technology in phantom and animal models. Using an electromagnetic navigation device, instrumented 18 g needles were advanced into radioopaque tumor targets in a respiratory liver phantom. The phantom featured a moving liver target that simulated cranio-caudal liver motion due to respiration. Skin-to-target path planning and real-time needle guidance were provided by a custom-designed software interface based on pre-operative 1 mm CT data slices. Needle probes were advanced using only the electromagnetic navigation device and software display. No conventional real-time imaging was used to assist in advancing the needle to the target. Two experienced operators (interventional radiologists) and two inexperienced ones (residents) used the system. The same protocol was then also used in two anesthetized 45 kg Yorkshire swine where radioopaque agar nodules were injected into the liver to serve as targets. A total of 76 tumor targeting attempts were performed in the liver phantom, and 32 attempts were done in the swine. The average time for path planning was 30 s in the phantom, and 63 s in the swine. The median time for the actual needle puncture to reach the desired target was 33 s in the phantom, and 42 s in the swine. The average registration error between the CT coordinate system and electromagnetic coordinate system was 1.4 mm (SD 0.3 mm) in the phantom, and 1.9 mm (SD 0.4 mm) in the swine. The median distance from the final needle tip position to the center of the tumor was 6.4 mm (SD 3.3 mm, n=76) in the phantom, and 8.3 mm (SD 3.7 mm, n=32) in the swine. There was no statistical difference in the planning time, procedure time, or accuracy of needle placement between experienced and inexperienced operators. The novel electromagnetic navigation system allows probe delivery into hepatic tumors of a physiologic phantom and live anesthetized swine. The system allows less experienced operators to perform equally well as experienced radiologists in terms of procedure time and accuracy of needle probe delivery.
BACKGROUND/OBJECTIVES: Heterotopic ossification (HO) is a frequent, irreversible complication after spinal cord injury (SCI). The objective of this article is to explain the etiology of HO; present new advances in prevention, diagnosis, and management of this complication; and provide a suggested algorithm for clinical management. ETIOLOGY: Although still hypothetical, trauma and overexpression of bone morphogenic protein(s) in traumatized soft tissue appear to play important roles as initiating factors of HO. PREVENTION: Preventive use of nonsteroidal antiinflammatory agents (NSAIDs) reduces the incidence of HO by a magnitude of 2 to 3. MANAGEMENT: Early determination of serum creatine phosphokinase may have a diagnostic value in predicting the onset and severity of HO, and an NSAID may be added to etidronate therapy in the initial inflammatory phase of HO formation until C-reactive protein levels return to normal range. Surgery is indicated in a subset of patients, and a regimen that includes radiation therapy may prevent postoperative recurrence. CONCLUSION: Significant progress has been made in the early prevention and management of HO. Further studies are needed to elucidate the etiology.
This article reviews the published efforts to characterize hepatic motion secondary to respiration, with the specific goal of defining the limitations and potential applications of image-guided systems in percutaneous liver interventions (computer assisted interventions). Hepatic motion and deformation due to respiration remain obstacles to applying stereotactic localization techniques to the liver. Respiratory-associated hepatic motion is complex. Nine studies using diagnostic imaging or modeling are reviewed, and their findings are tabulated herein. The significant variations in their findings are discussed, including cranio-caudal translation, anterior-posterior and lateral translation, movement secondary to tissue deformation, and motion with respect to surrounding tissue. Techniques for correcting for hepatic respiratory motion are then described, including gating techniques, modeling approaches, real-time liver tracking, and magnetic tracking technology.
PURPOSE: To determine the imaging outcome after uterine artery embolization (UAE) with use of tris-acryl gelatin microspheres (Embospheres). MATERIALS AND METHODS: A retrospective analysis of magnetic resonance (MR) images was performed comparing studies completed 3-4 months after UAE to those performed before UAE. Twenty-three patients with 61 leiomyomata (as many as three fibroids per patient) were examined. Orthogonal T2, axial T1-weighted fat-saturated, sagittal T2 fast spin-echo, and dynamic T1-weighted sagittal images after Gadolinium injection were analyzed. Two abdominal imaging specialists examined the volume and uterine and leiomyoma perfusion. The Wilcoxon signed-rank test was used for inferences in leiomyoma size difference, infarction, and volume of fibroid tissue perfused. RESULTS: Median volume of all leiomyomata (n = 61) decreased by 52% (P <.001). For dominant fibroids alone (n = 23), a median 52% volume decrease (P <.001) was also noted, whereas the median uterine volume decreased 32%. Median perfused volume of all fibroids decreased from 31 mL to 0 mL, signifying a 100% decrease (P <.001). For dominant fibroids, a 100% median perfused volume decrease from 116 mL to 0 mL was noted (P <.001). Fifty-two of 61 fibroids (85%) and 20 of 23 dominant fibroids (87%) were completely devascularized and two fibroids disappeared. There was no myometrial ischemia identified. CONCLUSIONS: Tris-acryl gelatin microspheres (Embospheres) are an effective embolic agent for UAE, causing infarction and significant decrease in leiomyoma volume.