Instrument Guidance Research Articles

MR imaging-guided laser ablation of osteoid osteomas with the use of optical instrument guidance at 0.23 T

MR imaging-guided laser ablation of osteoid osteomas with the use of optical instrument guidance at 0.23 T

MR imaging-guided laser ablation of osteoid osteomas with use of optical instrument guidance at 0.23 T.

The purpose of this study was to determine the feasibility and features of low-field MR imaging in performing interstitial laser ablation of osteoid osteomas. Between September 2001 and April 2002, five consecutive patients with clinical and imaging findings suggesting osteoid osteoma and referred for removal of osteoid osteoma were treated with interstitial laser treatment. A low-field open-configuration MRI scanner (0.23 T, Outlook Proview, Philips Medical Systems, Finland) with optical instrument guidance hardware and software was used. Laser device used was of ND-Yag type (Fibertom medilas, Dornier Medizin Technik, Germany). A bare laser fiber (Dornier Medizin Technik, Germany) with a diameter of 400 microm was used. Completely balanced steady-state (CBASS; true fast imaging with steady precession) imaging was used for lesion localization, instrument guidance, and thermal monitoring. A 14-G (Cook Medical, USA) bone biopsy drill was used for initial approach. Laser treatment was conducted through the biopsy canal. All the lesions were successfully localized, targeted, and treated under MRI guidance. All the patients were symptom free 3 weeks and 3 months after the treatment. There was one recurrence reported during follow-up (6 months). The MRI-guided percutaneous interstitial laser ablation of osteoid osteomas seems to be a feasible treatment mode.

Surgical instrument guidance system

Surgical instrument guidance system

Percutaneous MR-guided discography in a low-field system using optical instrument tracking: a feasibility study.

To evaluate the feasibility of MRI-guided discography with optical tracking. 12 consecutive patients who had a clinical suspicion of lumbar discogenic pain and/or suggestive finding of disc degeneration in imaging studies (MRI, CT, plain radiography) underwent MRI-guided discography in order to determine possible pain provocation during puncture and contrast injection. An 0.23 T open configuration MRI device with interventional tools (Outlook Proview, Philips Medical Systems, MR Technologies, Finland) was used in procedural imaging and instrument guidance. An optical guidance tool was attached to the MRI compatible needle (Chiba-type MReye, Cook, Bloomington, IN). After initial disc puncture, 1-2 mL of gadolinium contrast (Magnevist, 469 mg/mL, Schering AG, Germany) saline mixture (1:8) was injected into the disc. Immediately after injection, sagittal FE T1 weighted images were obtained to verify the final position of the needle and formation of the MRI discogram. On nine patients, additional noncontrast sagittal fast spin echo (FSE) T1, FSE T2, and axial 3D T1 gradient echo imaging was performed before and after contrast media injection to obtain MRI discograms. Overall, 35 disc punctures were initialized and 34 MRI discograms were obtained. In all punctures, a positive or negative pain response was obtained. The average time for performing a procedure for three discs was 1 hour 25 minutes (minimum 45 minutes, maximum 2 hours, 15 minutes), and the average number of imaging sequences used for a puncturing one disc was 12. On one disc, the puncture failed and a discogram was not acquired. There was one complication (disc collapse) reported during follow-up. Our results show that MRI guidance in performing discography is accurate and relatively safe. It is a technically comparable method to CT-guidance or fluoroscopy.

The minimally invasive, endoscopic approach to sinus surgery.

When anatomic abnormalities of the nose and sinuses contribute to sinusitis, and when medical therapy has failed, these anatomic or structural abnormalities can be surgically corrected. Examples of anatomic problems include nasal polyps, nasal septal deviations, and blockage of the osteomeatal complex--the "crossroads" of the sinuses. Endoscopic techniques allow sinus specialists to diagnose and treat these problems more easily than in the past, allowing them to be more proactive in the management of anatomic nasal abnormalities. In this article we review the minimally invasive, endoscopic approach to sinus surgery and discuss recent advances in sinus surgery. Specifically, we discuss the utility of powered instrumentation and image guidance in endoscopic sinus surgery.

Interventional MRA using actively visualized catheters, TrueFISP, and real-time image fusion.

An integrated system for performing interventional magnetic resonance angiography (MRA) with actively visualized instruments and real-time image fusion was implemented on a 1.5 T scanner. True fast imaging with steady precession (TrueFISP) imaging provided high acquisition speed paired with high signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for the simultaneous visualization of active instruments and arterial morphology. The system enabled simultaneous image reconstruction and image postprocessing of multiple receiver channels, with subsequent image fusion display in real time. Optional interleaved image acquisition in two planes provided additional important information for biplanar instrument guidance. Various vascular interventions, including selective catheterization and subsequent selective MRA of the abdominal aorta, renal arteries, superior mesenteric artery (SMA), hepatic artery, and aortic arch, were performed on 10 pigs under MR guidance. In terms of instrument contrast, image acquisition, reconstruction, and fusion speed, the setup represents a powerful platform for performing interventional MRA procedures.

Technology improvements for image-guided and minimally invasive spine procedures.

This paper reports on technology developments aimed at improving the state of the art for image-guided minimally invasive spine procedures. Back pain is a major health problem with serious economic consequences. Minimally invasive procedures to treat back pain are rapidly growing in popularity due to improvements in technique and the substantially reduced trauma to the patient versus open spinal surgery. Image guidance is an enabling technology for minimally invasive procedures, but technical problems remain that may limit the wider applicability of these techniques. The paper begins with a discussion of low back pain and the potential shortcomings of open back surgery. The advantages of minimally invasive procedures are enumerated, followed by a list of technical problems that must be overcome to enable the more widespread dissemination of these techniques. The technical problems include improved intraoperative imaging, fusion of images from multiple modalities, the visualization of oblique paths, percutaneous spine tracking, mechanical instrument guidance, and software architectures for technology integration. Technical developments to address some of these problems are discussed next. The discussion includes intraoperative computerized tomography (CT) imaging, magnetic resonance imaging (MRI)/CT image registration, three-dimensional (3-D) visualization, optical localization, and robotics for percutaneous instrument placement. Finally, the paper concludes by presenting several representative clinical applications: biopsy, vertebroplasty, nerve and facet blocks, and shunt placement. The program presented here is a first step to developing the physician-assist systems of the future, which will incorporate visualization, tracking, and robotics to enable the precision placement and manipulation of instruments with minimal trauma to the patient.

Image-guided robotic delivery system for precise placement of therapeutic agents

The effectiveness of conventional solid tumor treatment is limited by the systemic toxicity and lack of specificity of chemotherapeutic agents. Present treatment modalities are frequently insufficient to eliminate competent cancer cells without exceeding the limits of toxicity to normal tissue. The coming generation of cancer therapeutics depends on the precise targeting and sustained release of antitumor agents to overcome these limitations. We are developing an image-guided, robotic system for precise intratumoral placement of anticancer drugs and sustained release devices to advance this new treatment paradigm. The robotic system will use intraoperatively obtained computed tomographic (CT) images from a mobile CT scanner for guidance. The concept is to track patient anatomy and localize instruments using currently available optical tracking technology. Tracking will also be used to register patient anatomy with the images. The physician can then use the registered image to select an appropriate tumor target and entry location and to plan the instrument path. This path will then be transmitted to the robot, which orients and drives the instrument to the desired target under physician control. Achievement of the target is confirmed via intraoperative CT. This system will provide instrument guidance that is precise, direct, and controllable. Error due to poor target visualization and hand unsteadiness should be reduced greatly. The basic components of the system (robot, mobile CT, tracking) have been demonstrated in our laboratory, and the integration of the components is in progress. In future work, we plan to fuse preoperative PET imaging with intraoperative CT to allow functional as well as anatomic image guidance.

Intraoperative magnetic resonance imaging with the magnetom open scanner: concepts, neurosurgical indications, and procedures: a preliminary report.

Intraoperative magnetic resonance imaging (MRI) is now available with the General Electric MRI system for dedicated intraoperative use. Alternatively, non-dedicated MRI systems require fewer specific adaptations of instrumentation and surgical techniques. In this report, clinical experiences with such a system are presented. All patients were surgically treated in a "twin operating theater," consisting of a conventional operating theater with complete neuronavigation equipment (StealthStation and MKM), which allowed surgery with magnetically incompatible instruments, conventional instrumentation and operating microscope, and a radiofrequency-shielded operating room designed for use with an intraoperative MRI scanner (Magnetom Open; Siemens AG, Erlangen, Germany). The Magnetom Open is a 0.2-T MRI scanner with a resistive magnet and specific adaptations that are necessary to integrate the scanner into the surgical environment. The operating theaters lie close together, and patients can be intraoperatively transported from one room to the other. This retrospective analysis includes 55 patients with cerebral lesions, all of whom were surgically treated between March 1996 and September 1997. Thirty-one patients with supratentorial tumors were surgically treated (with navigational guidance) in the conventional operating room, with intraoperative MRI for resection control. For 5 of these 31 patients, intraoperative resection control revealed significant tumor remnants, which led to further tumor resection guided by the information provided by intraoperative MRI. Intraoperative MRI resection control was performed in 18 transsphenoidal operations. In cases with suspected tumor remnants, the surgeon reexplored the sellar region; additional tumor tissue was removed in three of five cases. Follow-up scans were obtained for all patients 1 week and 2 to 3 months after surgery. For 14 of the 18 patients, the images obtained intraoperatively were comparable to those obtained after 2 to 3 months. Intraoperative MRI was also used for six patients undergoing temporal lobe resections for treatment of pharmacoresistant seizures. For these patients, the extent of neocortical and mesial resection was tailored to fit the preoperative findings of morphological and electrophysiological alterations, as well as intraoperative electrocorticographic findings. Intraoperative MRI with the Magnetom Open provides considerable additional information to optimize resection during surgical treatment of supratentorial tumors, pituitary adenomas, and epilepsy. The twin operating theater is a true alternative to a dedicated MRI system. Additional efforts are necessary to improve patient transportation time and instrument guidance within the scanner.

Experience with a new multifunctional articulated instrument holder in minimally invasive navigated neurosurgery.

A new multifunctional articulated instrument holder for use in minimally invasive navigated neurosurgery is presented. The instrument holder is secured to the Mayfield clamp, yielding permanent fixation and guidance of instruments. Thus, surgical conditions with the advantages of both conventional and frameless stereotaxic neurosurgery are created without sacrificing the relevant advantages of both methods. Accuracy testing of the instrument holder in combination with the neuronavigation system EasyGuide Neuro demonstrated an error of 0.0 to 2.4 (mean 1.6) mm. In clinical testing, the device has been used for guided catheter insertions, pointer fixation for continuous intraoperative guidance and trajectory planning, navigated endoscopic procedures, and navigated intracerebral biopsies in totally 53 patients.

Active instrumental guidance in interventional MR tomography: introduction to a new concept

An active MR-based guidance system for visualisation of invasive instruments is described. The principle of MR tracking is based on the integration of a miniaturised coil into the tip of the instrument itself. A phantom experiment was designed to demonstrate the localising accuracy of this technique. In addition, biocompatibility and warming effects were evaluated. Preliminary intravascular applications that were performed in animal experiments under MR guidance included embolisation, vascular occlusion as well as transjugular intrahepatic punctures. Percutaneous biopsies, cholecystostomies and laparoscopic applications were also evaluated with MR tracking. Phantom experiments confirmed an excellent localisation accuracy of MR tracking compared top conventional radiography. At a field strength of 0.5 T, the temperature increase remained below 2 degrees C. Results of phantom experiments revealed a potential of significant heating dependent on the sequence parameters employed. MR tracking allowed a robust, simultaneously biplanar visualisation of the instrument tips in real time. Based on MR "road map" images, various intravascular and percutaneous interventions were successfully performed in vivo under MR guidance. MR tracking is a flexible concept permitting monitoring in the guidance of instruments in an MR environment. Various preliminary in vitro and in vivo experiments demonstrate safety, localisation accuracy and feasibility of this biplanar localisation technique in real time.

Tomographic Microtherapy

Minimally invasive techniques using endoscopes for image-guided therapy are now common in the field of surgery. Fast real-time radiologie imaging should be integrated into the procedure for increased safety in access and guidance techniques for endoscopes and instruments. The transparency of computed tomography (CT) guidance, magnetic resonance imaging, and electron beam tomography scan techniques allows precise guidance of instruments and endoscopes while permitting their diameter to be minimized. This guarantees safe and transparent access into the body, especially in high-risk areas such as the spine and brain. Combining both technologies has the potential to reduce complications and offers significant advantages in microinvasive operative procedures such as biopsies; local tumor therapy with lasers, radio frequency, or drugs; and percutaneous diskectomies or implants. CT is the golden standard for microtherapeutic procedures because of its precise tip discrimination.

Tomographic microtherapy.

Minimally invasive techniques using endoscopes for image-guided therapy are now common in the field of surgery. Fast real-time radiologic imaging should be integrated into the procedure for increased safety in access and guidance techniques for endoscopes and instruments. The transparency of computed tomography (CT) guidance, magnetic resonance imaging, and electron beam tomography scan techniques allows precise guidance of instruments and endoscopes while permitting their diameter to be minimized. This guarantees safe and transparent access into the body, especially in high-risk areas such as the spine and brain. Combining both technologies has the potential to reduce complications and offers significant advantages in microinvasive operative procedures such as biopsies; local tumor therapy with lasers, radio frequency, or drugs; and percutaneous diskectomies or implants. CT is the golden standard for microtherapeutic procedures because of its precise tip discrimination.

Interventional CT and MRI combined with microendoscopy for low back pain therapy

SummaryAcute and chronic back pain is the second most significant medical problem world-wide. Microinvasive CT-guided treatments of the spine are routine in our department. For this study, newly-developed procedures in an open 0.064 T and 0.2 T magnetic resonance imaging (MRI) scanner were compared with interventional CT. 340 patients who underwent microtherapeutic treatment took part in the study: 80 had percutaneous laser nucleotomies (PLNT), 100 had facet joint and 100 periradicular therapies (PRT); another 60 patients had ilio-sacral joint infiltrations. For PLNT a Neodymium YAG laser was used; for scar tissue treatment a Holmium YAG laser was used; for the other treatments, local anesthesia and cortisone, and 1.0 cm3 50–96% ethanol (used for denervation in treatment of chronic facet joint pain) were instilled. 100 endoscopic treatments with systems 0.29–1.8 mm in diameter were undertaken: 20 on the facet joints, 80 inside the foramen intervertebrae, before and inside the disc after laser nucleotomy. Before treatment, 340 patients had a pain score of 70–100 on a visual analogue scale (VAS). The average pain score before therapy was 86%, after treatment it decreased to 7% (6 month follow-up). Neurologic deficits improved in 87% of cases after endoscopic discectomy (73% at follow-up). In MRI open access allows near real-time guidance of instruments. But the last 3.5 mm at the tip of the instruments is not easy to define. Interventional MRI is a routine technique in low risk areas, as in facet and ilio-sacral joints. CT-guidance is now the standard technique. In the future, endoscopes, drugs, lasers, RF-probes, cryosticks and mechanical instruments will be guided inside tomographic scanners for routine spinal work.

Technology and principles of tomographic image-guided interventions and surgery.

Image guidance of instruments can be performed by fluoroscopy, ultrasound imaging, computed tomography (CT), magnetic resonance imaging (MRI), and by stereotactic navigation. During the last year, there has been significant progress in MRI instrument guidance in the field of interventional radiology. Our first 168 clinical cases of MRI-guided interventional procedures, e.g., aspiration biopsy of neoplasms and tomographic microtherapy with local interstitial chemo-ablation, confirm the feasibility of MRI guidance. An expansion of MRI guidance during surgical endoscopic procedures is currently under evaluation and the initial results of this development are presented. Tomographic-guided surgery and the implementation of MRI or CT scanning within the environment of an operating room (OR) entail specific technological requirements and OR design considerations. Fast sequences, interventional protocols, in-room monitor, as well as MR-compatible probes, cannulae, catheters, instruments, endoscopes, and auxiliary equipment that are necessary for this combined surgical image-guided approach are described.

3D computer-assisted ENT biopsies of the Iceman

The University of Innsbruck possesses a unique prehistoric, completely conserved 5300-year-old human cadaver. We report our experiences during which ENT specialists collected samples from various cavities inside the Iceman. Guidance of biopsy instruments was accomplished with computer-assisted navigation based on Interventional Video Tomography. This technology allows surgical guidance by interlinking currently available imaging modalities with live endoscopic video. The system operates without patient fixation and is practically free of external contact. Apart from sterility, special precautionary measures were necessary to avoid contamination with heavy metals or microorganisms. Visual inspection of the samples of mucosa from the nose, maxillary sinus and larynx revealed the typical patterns of a human cadaver without overt pathology.

Clinical Introduction of an Adjustable Rigid Instrument Holder for Frameless Stereotactic Interventions

Interactive image guidance is now in routine use for open neurosurgical procedures and has demonstrated patient benefits. However, freehand interactive guidance is not an appropriate replacement for the traditional frame-based stereotactic procedures of biopsy, electrode placement, and functional lesioning. These point-based procedures require precise target localization and direct instrument guidance to avoid collateral brain injury. To perform true frameless stereotactic procedures requires a guide that is also adjustable for positioning, lockable, and adaptable to multiple instruments. We describe such a device, which is employed for the guidance of biopsy needles, shunts, electrodes, and endoscopes during neuronavigation. The method of frameless stereotactic biopsy retrieval with an infrared-based neuronavigation system is described, clinical results are given, and further areas of application discussed.

Clinical introduction of an adjustable rigid instrument holder for frameless stereotactic interventions

Interactive image guidance is now in routine use for open neurosurgical procedures and has demonstrated patient benefits. However, freehand interactive guidance is not an appropriate replacement for the traditional frame-based stereotactic procedures of biopsy, electrode placement, and functional lesioning. These point-based procedures require precise target localization and direct instrument guidance to avoid collateral brain injury. To perform true frameless stereotactic procedures requires a guide that is also adjustable for positioning, lockable, and adaptable to multiple instruments. We describe such a device, which is employed for the guidance of biopsy needles, shunts, electrodes, and endoscopes during neuronavigation. The method of frameless stereotactic biopsy retrieval with an infrared-based neuronavigation system is described, clinical results are given, and further areas of application discussed.

Equipment configuration and procedures: preferences for interventional microtherapy.

Magnetic resonance imaging (MRI), computed tomography, and electron beam tomography scanners are built for radiologic diagnosis. With increasing frequency they are being used in the field of interventional Microtherapy to permit transparent visualization of the therapeutic field. Each of these scanners can be combined with endoscopy, fluoroscopy/digital subtraction angiography, and ultrasound units for hybrid imaging techniques as well as with therapeutic systems like lasers or radiofrequency. MRI affords 3D localization without x-ray exposure. Open access and keyhole imaging allow nearly real time guidance of instruments. Minimally invasive techniques using endoscopes and hybrid tomographic guidance result in improved tip tracking of microinstruments and reduced complications. This safer access into the body will lead to interdisciplinary cooperation with the potential for large cost reductions. This report summarizes our experience regarding which of the hybrid imaging suites is best suited for procedures including among others drug instillations, prosthesis (stent) implantation, or microoperations (endoscopic diskectomy/sequestrectomy), and physiological measurements simultaneously.

Minimally invasive treatment of spinal diseases

SummaryTreatments of spinal diseases can be performed safely under CT and MRI guidance. Both techniques allow full transparency of all structures in the body. In combination with micro endoscopy small endoscopes with a diameter less than 1 mm can be used to visualize the operative field in the foramen intervertebrale or in the spinal canal. Small arteries and vessels under 0.01 mm can be seen and protected. Facet joint treatment, periradicular therapy are less invasive methods with a wide indication for spinal diseases. In cases with free fragments we have developed a new technique for percutaneous seques-trectomy. The combination of CT scanning, fluoroscopy MRI and micro endoscopy for guidance of nucleotomes, lasers and micro instruments offers a safe and effective treatment of small free fragments and scar tissue in the spinal canal and the foramen.