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At least 253 records · Page 14Linked to original sources
PubMed2000

Practical aspects for optimal registration (matching) on the lateral skull base with an optical frameless computer-aided pointer system.

HYPOTHESIS: Paired-point matching and surface matching are highly accurate when used on the lateral skull base with an optical computer-aided surgery system. BACKGROUND: Computer-aided surgery on the lateral skull base can be done with a pointer system or with the microscope. An optical pointer system that uses anatomic landmarks and surface points has been developed in Bern, Switzerland. METHODS: Axial computed tomography of a cadaver skull was performed. The images were processed on a computer workstation. An infrared camera was used. A reference base mounted on the head and a needle pointer, both equipped with light-emitting diodes, were used. Different anatomic landmarks were determined on the computer image of the skull and were compared with the actual anatomic markers taken on the bone or on the skin simulation material, and the target error was defined. In a second step, additional surface points on different regions of the skull were taken, and the inaccuracy from the target was redetermined. RESULTS: The authors found a mean average error in accuracy from the target with paired-point matching alone in the best series of 0.79 mm. Under skin simulation, they found a deterioration with paired-point matching alone but an improvement in accuracy with surface matching. CONCLUSION: For this navigation system, it is recommended that the following five anatomic points be selected for matching of the lateral skull base: the tip of the mastoid, the mastoid foramen, the umbo, the frontozygomatic suture, and the anterior nasal spine. For additional accuracy in clinical situations, surface matching is recommended.

Microscopy↗
PubMed2001

Anatomical basis of lumboscopy.

Lumboscopy provides an approach to the retroperitoneum for the majority of upper urinary tract operations. The technique involves a knowledge of specific anatomical landmarks that differ from those in classical open surgery, because of the inferior approach to the renal pedicle with the kidney initially mobilized in a ventral and cranial position. An anatomical study was conducted on five cadavers, using images from surgical operations, in order to describe the vascular elements of the retroperitoneal spaces as they are approached during lumboscopy, as well as to define specific anatomical landmarks. Identification of psoas major is crucial as it is then possible to locate the renal pedicle opposite and the area of the great vessels medially. During dissection of the renal pedicle the renal vein and its branches are the first elements to be approached. On the left side the distal portion of the renal vein can be confused with a reno-hemi-azygo-lumbar trunk, due to the initial ventral mobilization of the kidney stretching it. Because of the inferior view of the renal pedicle the reno-hemi-azygo-lumbar trunk can obscure part of the renal artery and may be confused with the renal vein. On the right side initial identification of the inferior vena cava on the medial aspect of psoas major facilitates identification of the gonadal, renal and suprarenal veins all located in the same plane.

Cadaver↗
PubMed2002

A logical and stepwise operative approach to radical neck dissection.

A thorough understanding of the anatomy of the neck is essential to avoid injury to vital structures when performing radical neck dissection. The complicated anatomical relations of the various nerves, vessels, and muscles within the confined area of the neck can often be daunting. We outline strategic anatomical landmarks and their relationships to important nerves, arteries, veins, and lymphatics to simplify the complicated and formidable anatomy of the neck. We also delineate key maneuvers that, when combined with the anatomical landmarks, offer a stepwise and logical approach to performing radical neck dissection that confers improved safety.

Humans↗
PubMedDate not supplied

Ultrasound imaging of the thoracic epidural space.

BACKGROUND AND OBJECTIVES: In thoracic epidural anesthesia, the "loss of resistance" technique is the standard technique for the identification of the epidural space (EDS), the feedback to the operator is often solely tactile. Our aim was to establish ultrasonography for the prepuncture demonstration of the anatomic structures surrounding the thoracic EDS and to evaluate its precision and imaging quality. METHODS: We examined 20 volunteers. In each participant, the extradural space and the neighboring anatomic landmarks in the intervertebral space Th 5-6 were identified using 2 imaging techniques: magnetic resonance imaging (MRI) and ultrasonography. We compared corresponding images regarding distance measurements and the visibility of anatomic landmarks. RESULTS: The capacity of ultrasound imaging (US) to depict the thoracic EDS was limited. Due to the better overview, MR images were easier to interpret. However, US proved to be of better value than MRI in the depiction of the dura mater. All important landmarks for the puncture of the thoracic EDS could be identified with both techniques. The overall correlation was satisfactory. US depicted the different structures of the thoracic EDS with an acceptable precision (confidence interval, 4.6 to 8.7 mm). CONCLUSIONS: US showed good correlation with MRI, which is a standard imaging technique for the depiction of the spine. We anticipate that prepuncture ultrasonography may facilitate thoracic epidural anesthesia by needle placement.

Adult↗
PubMed1999

[Endoscopic axillary lymph node excision--results of a pilot study].

OBJECTIVE: Assessment of axillary nodal status with reduced shoulder-arm-morbidity remains a major challenge for primary surgery of breast cancer patients. In a pilot study endoscopic axillary lymph node dissection was evaluated. MATERIAL AND METHODS: In 30 breast cancer patients axillary lymphadenectomy was performed after liposuction using an endoscopic approach. During a learning phase of 15 cases an open revision was routinely carried out. Later complete endoscopic lymph node dissection was performed. The exposition of anatomical landmarks, the number of resected lymph nodes, postoperative lymphorrhea, histopathological signs of traumatisation were assessed as well as intra and postoperative complications. RESULTS: In any case we found excellent exposure of anatomical landmarks. Following a learning curve of 15 cases the average number of resected lymph nodes was equal to the average number of lymph nodes resected with conventional techniques (18.2 vs. 18.4, median 17 vs 18). Minimal intraoperative complications were observed. Postoperative lymphorrhea and seroma rate were not remarkably reduced in comparison with open procedures. CONCLUSIONS: Our study demonstrates, that endoscopic lymph node dissection may be performed with a low complication rate and with identical accuracy as achieved by open techniques.

Axilla↗
PubMed2003

Electromagnetic field-based image-guided spine surgery part two: results of a cadaveric study evaluating thoracic pedicle screw placement.

STUDY DESIGN: Human cadaveric. OBJECTIVES: Compare the accuracy of electromagnetic field (EMF)-based image-guided thoracic pedicle screw insertion to conventional techniques using anatomic landmarks and fluoroscopy. BACKGROUND: Image-guided surgical systems that aid in spinal instrumentation seek to minimize radiation exposure and improve accuracy. EMF image guidance was developed as an alternative to optical tracking to eliminate potential line of sight issues. MATERIALS AND METHODS: Four fresh-frozen human cadavers were randomly allocated into two groups. Pedicle screws were inserted from T1 to T12 using anatomic landmarks and fluoroscopy in group 1 and image guidance in group 2. Insertion and fluoroscopy time were recorded. Anatomic dissections were performed to assess screw placement. RESULTS: Image guidance placed 92% of thoracic pedicle screws safely, and conventional fluoroscopy placed 90% safely. The average degree of perforation was 2.4 mm with conventional fluoroscopy and 1.7 mm with image guidance (P = 0.055). Fluoroscopic time per screw was 5.9 seconds for conventional fluoroscopy and 3.6 seconds for image guidance (P = 0.045). Insertion time per screw was 4.35 minutes for conventional fluoroscopy and 2.98 minutes for image guidance (P = 0.007). However, when set-up time and image capture time were taken into account, the total insertion time per screw was not significantly different between the two groups. CONCLUSIONS: Our study has shown that EMF image-guided thoracic pedicle screw placement results in a similar incidence of safely placed screws as does conventional fluoroscopy. When set-up time and image-capture time were factored in for image guidance, the average time to insert a pedicle screw was equal for both techniques. The use of EMF image guidance significantly reduced fluoroscopic time and thus radiation exposure per screw compared with conventional fluoroscopic techniques.

Analysis of Variance↗
PubMed1993

Auditory brainstem implant: I. Issues in surgical implantation.

Most patients with neurofibromatosis type 2 (NF2) are totally deaf after removal of their bilateral acoustic neuromas. Twenty-five patients with neurofibromatosis type 2 have been implanted with a brainstem electrode during surgery to remove an acoustic neuroma. The electrode is positioned in the lateral recess of the fourth ventricle, adjacent to the cochlear nuclei. The present electrode consists of three platinum plates mounted on a Dacron mesh backing, a design that has been demonstrated to be biocompatible and positionally stable in an animal model. Correct electrode placement depends on accurate identification of anatomic landmarks from the translabyrinthine surgical approach and also on intrasurgical electrophysiologic monitoring. Some tumors and their removal can result in significant distortion of the brainstem and surrounding structures. Even in the absence of identifiable anatomic landmarks, electrode location can be adjusted during surgical placement to find the location that maximizes the auditory evoked response and minimizes activation of other monitored cranial nerves. Stimulation of the electrodes produces auditory sensations in most patients, with results similar to those of single-channel cochlear implants. A coordinated multidisciplinary team is essential for successful application of an auditory brainstem implant.

Brain Stem↗
PubMed2000

Characterizing and reporting pelvic floor defects: the revised New York classification system.

The authors have devised a conceptual model and reporting system for characterizing, grading and staging pelvic floor defects. The system is user friendly and simple to learn and apply. It is based on commonly known anatomic landmarks and can be performed without memorizing or referring to a separate characterization and reporting plan. Completing the accompanying forms is self-explanatory and provides the information needed for proper comprehension and recording of anatomic defects. The model and reporting format have been used at our institutions for 5 years by medical students, residents, fellows and attendings. It has several advantages over the Pelvic Organ Prolapse Quantitation (POPQ) system: (1) it uses known anatomic landmarks rather than alphabetic labels; (2) it grades lateral wall defects which the POPQ system omits; (3) it recognizes and reports isolated defects or tears which present as bulges in the vaginal walls without downward linear descent (prolapse); (4) it uses a one-page reporting form and a one-page checklist and vaginal profile; (5) it can be done easily in both the supine and the standing positions; (6) it requires simple instruments and a disposable measuring tape available in most office settings; (7) it includes urethral hypermobility in its reporting scheme; (8) it includes cervical length, perineal descent and other measurements in its reporting scheme; and (9) it is similar enough to the POPQ system that easy conversion to, and integration with, the POPQ reporting form and vaginal profile is possible. Prospective trials testing the validity of this system and comparing it with the POPQ system for validity, reliability, reproducibility, test-retest analysis, and interobserver and intraobserver variance are warranted.

Female↗
PubMed1985

Stereo radiography of lumbar spine motion.

The technique of Biplanar Radiography for the computer analysis of orthogonal radiographs of the human spine enables the calculation of three-dimensional coordinates for anatomical landmarks on the vertebrae. Three-dimensional intervertebral movements are deduced from the changes in the relative orientations of the vertebrae as a subject moves from one position to another. The three-dimensional coordinates of the anatomical landmarks on the vertebrae were found to have an RMS error of less than 1 mm. The RMS errors for translational movements were less than 2 mm and for rotations were less than 1.5 degrees. This study of normal subjects has defined the ranges of voluntary flexion and extension, axial rotation, and lateral bending in the lumbar spines of young males. The range of flexion plus extension at each lumbar intervertebral joint is approximately 14 degrees with the L4/5 level being slightly more mobile than the others. There are approximately 2 degrees of axial rotation at each joint with L3/4 and L4/5 being slightly more mobile. Lateral bending of approximately 10 degrees occurs at the upper three levels while there is significantly less movement of 6 degrees and 3 degrees at L4/5 and L5/S1 respectively. In flexion and extension accompanying axial rotation of 2 degrees or more and lateral bending of 3 degrees or more occurred rarely and any larger accompanying rotation at an intervertebral joint should be considered abnormal. During twisting and side bending axial rotation to the right is accompanied by lateral bending to the left and vice versa at the three upper levels. At L5/S1 axial rotation and lateral bending generally accompany each other in the same direction while L4/5 is a transitional level. During lateral bending there is also generally extension at the upper levels and flexion at L5/S1. The measurement in vivo of the accompanying rotations in the other planes has demonstrated that there is no simple mechanical coupling of the rotations. Finally, this study has provided a base line of normal movements to which the movements seen in pathological conditions can be compared.

Adult↗
PubMed2003

Endoscopic surgical anatomy of the paediatric third ventricle studied using virtual neuroendoscopy based on 3-D ultrasonography.

INTRODUCTION: Endoscopic treatment for occlusive hydrocephalus requires knowledge of individual ventricular and vascular anatomies of the ventricular system. METHODS: We studied the feasibility of virtual neuroendoscopy (VNE) based on 3-D ultrasonography (3-D US) for the identification of parenchymal and vascular anatomical landmarks of the third ventricle and its impact on the surgical planning of endoscopic third ventriculostomy (ETV) in paediatric patients. 3-D US was performed through the anterior fontanel in four infants with hydrocephalus. RESULTS: Virtual neuroendoscopy revealed the size of the foramen of Monro, anatomical landmarks of the floor of the third ventricle crucial for correct fenestration during ETV, but not the premesencephalic cistern. The basilar bifurcation was identified in relation to the floor of the third ventricle by VNE (power-Doppler ultrasonography) and confirmed intraoperatively after ETV. CONCLUSION: 3-D US-based VNE reveals detailed anatomical information on the ventricular system including the foramen of Monro and the floor of the third ventricle. Within the premesencephalic cistern vascular anatomy can be visualized, but not non-vascular structures.

Cerebral Aqueduct↗
PubMed1987

Surgical accessibility of the cochlear nuclear complex in man: surgical landmarks.

Patients deafened by bilateral acoustic tumors or by transections of both cochlear nerves are excluded as candidates for cochlear implantation. These patients require more proximal stimulation of the auditory pathway. One potential area for such stimulation is the cochlear nuclear complex (CNC) in the lateral recess of the fourth ventricle. If animal studies establish the safety and efficacy of such stimulation, electrical stimulation of the human cochlear nuclear complex may become an accepted treatment modality for this select group of patients. Such implantation requires that the surgeon accurately locate the cochlear nuclear complex without destruction of vital surrounding neural and vascular structures. With ten fresh human brains, oriented for a translabyrinthine approach, we determined key anatomical landmarks to the exposed surface of the CNC on both sides of each brain. Using a combination of anatomical landmarks--including the flocculus, eighth nerve root, choroid plexus, and taenia--we located the cochlear nuclear complex (without disruption of surrounding neural or vascular structures) and marked it with colloidal carbon. Access to the CNC was obtained in all 20 specimens, and histologic sections confirmed the carbon marker in the CNC in 19 of 20 specimens.

Cochlea↗
PubMed2003

Electromagnetic field-based image-guided spine surgery part one: results of a cadaveric study evaluating lumbar pedicle screw placement.

STUDY DESIGN: Human cadaveric. OBJECTIVES: Compare the accuracy of electromagnetic field (EMF)-based image-guided lumbar pedicle screw insertion to conventional techniques using anatomic landmarks, and fluoroscopy. BACKGROUND: Image-guided surgical systems that aid in spinal instrumentation seek to minimize radiation exposure and improve accuracy. EMF tracking-based image-guidance was developed in the hopes of eliminating line-of-sight restrictions seen with other systems. MATERIALS AND METHODS: Sixteen fresh-frozen human cadavers were randomly allocated into three groups. Pedicle screws were inserted from L1 to L5 using only anatomic landmarks in group 1, fluoroscopy in group 2, and image-guidance in group 3. Insertion and total fluoroscopic time were recorded. Anatomic dissections were performed to assess screw placement. RESULTS: Accuracy was 83%, 78%, and 95% for groups 1, 2, and 3, respectively. However, image-guided pedicle screw placement resulted in a 5% critical perforation rate whereas anatomic and fluoroscopic placement resulted in a 15% and 22% critical perforation rate, respectively. The average degree of perforation was 1.5 mm with image guidance, and 3.8 mm with fluoroscopic guidance (P < 0.05). Fluoroscopy time and insertion time per screw were not improved using image guidance. CONCLUSIONS: Our study has shown that when EMF tracking was used for image-guided lumbar pedicle screw placement, accuracy was improved and the incidence and degree of cortical perforations that may place neurovascular structures at risk was also reduced. Current system requirements for set-up and image acquisition, however, do add time to the procedure, and when factored in, do not yet result in a decrease in the use of fluoroscopy or screw insertion time.

Analysis of Variance↗
PubMed2000

Ultrasonography of the femoral vessels in the groin: implications for vascular access.

The femoral artery and vein are commonly used for access to the circulation. Accidental puncture of one vessel whilst attempting to cannulate the other is a common complication. Identification of relevant surface anatomical landmarks and ultrasonography of both groins was performed on 50 consecutive adult patients admitted to the intensive care unit. In most patients there was overlap of the artery over the vein far closer to the inguinal ligament than conventional anatomical texts would indicate. The frequency and degree of overlap increased as the vessels descended distally towards the knee. Surface anatomical landmarks were not useful in predicting the underlying anatomy. The side-by-side relationship of artery and vein is commonest close to the inguinal ligament. Therefore, to avoid damage to the neighbouring vessel, percutaneous access should be undertaken just below the inguinal ligament.

Catheterization, Peripheral↗
PubMed2000

Quantitative human in vivo evaluation of high resolution MRI for vessel wall morphometry after percutaneous transluminal angioplasty.

Visualization of the vessel wall after transluminal angioplasty is important to monitor the restenosis progress. Intravascular ultrasound proved its capabilities as an invasive procedure in many studies. The aim of this study was to evaluate the feasibility of high-resolution MRI as a non-invasive tool for follow-up after PTA. High-resolution magnetic resonance images (pixel size: 0.49 * 0.49 mm(2)) were acquired on a 1.0 T clinical scanner. Morphometry was conducted after conversion of DICOM images into TIFF format using ScionImage on a PC. In-vitro studies using a polyvinylchloride tube were evaluated by two independent investigators. Goldstandard was a caliper rule and direct radiography. Five patients were monitored before and 24 h, six weeks, three months and six months after PTA. In vivo measurements promised a good concordance for both investigators for area as well as for diameter measurements. Area measurements showed correlations up to r = 0.86 (p < 0.001) whereas the correlations of diameters were slightly inferior (r between 0.58 and 0.84; p < 0.005). Relocation of the same slice position in the follow up studies could be guaranteed using anatomic landmarks in the images. As a non-invasive tool to assess restenosis after PTA high-resolution MRI promises to be a reproducible technique. It is easy to identify the same vascular region in different studies due to neighboring anatomic landmarks. Progression of disease as well as success of pharmacologic treatment to prevent restenosis may be monitored.

Aged↗
PubMed1990

Intraoperative determination of the extent of corpus callosotomy for epilepsy: two simple techniques.

There is increasing interest in staged corpus callosotomy for intractable generalized epilepsy. At the first procedure, a portion (usually the anterior two-thirds) of the corpus callosum is sectioned. If seizures persist, completion of callosotomy or alternative treatment approaches can be considered. It is obviously important to ascertain that the desired extent of callosotomy was in fact accomplished at the time of initial operation. Our experience and the published literature indicate that the surgeon's impression at operation can be erroneous. We describe a technique of determining extent of corpus callosotomy during the procedure. The magnetic resonance imaging (MRI) scan in the midsagittal plane is used to select the desired extent of callosotomy. That point on the corpus callosum is characterized using simple planar geometry in relation to three anatomic landmarks in that same plane: the glabella, the inion, and the bregma (midline intersection of the coronal suture). The same point along the corpus callosum can then be located on a lateral skull x-ray using these same three anatomic landmarks. At surgery, an intraoperative lateral skull x-ray is obtained with a marking clip, thereby verifying the actual extent of callosotomy. We have verified the reliability of this scheme in 5 callosotomy procedures and have used this technique for intraoperative localization of midline and parasagittal targets in another 7 cases (3 tumors, 2 aneurysms, and 2 placements of interhemispheric subdural grids). In addition, we reviewed corpus callosum topography on 25 randomly selected MRI scans.(ABSTRACT TRUNCATED AT 250 WORDS)

Corpus Callosum↗
PubMed2005

Comparison of magnetic tracking and optical tracking by simultaneous use of two independent frameless stereotactic systems.

OBJECTIVE: The goal of this study was to compare the calculated accuracy and the true surgical accuracy of a magnetic and an optical tracking system at surgical registration and during surgery. METHODS: Two Food and Drug Administration-approved, commercially available frameless stereotactic systems were used simultaneously in 70 surgical cases. The Compass Cygnus-PFS system (Compass International, Rochester MN) uses magnetic field referencing and tracking. The StealthStation (Medtronic SNT, Louisville, CO) uses optical referencing and tracking. Registration was performed for each of the systems using adhesive fiducial markers, cranial-implanted markers, anatomic landmarks, or a combination thereof. Preoperative imaging consisted of volumetric computed tomography, magnetic resonance imaging, or both. Calculated accuracy was given by each of the systems as the root mean square after registration. Surgical accuracy was assessed by comparing the anatomic accuracy of each system with a number of recognizable intraoperative anatomic landmarks. RESULTS: Calculated accuracy (root mean square) was 1.4 +/- 0.6 mm using the magnetic system and 1.4 +/- 0.8 mm using the optical tracking system. In the 42 patients with implanted cranial fiducials, the calculated accuracies were 1.0 +/- 0.5 mm (magnetic) and 0.9 +/- 0.4 mm (optical). True surgical accuracy was considered good (3 mm or less) in both systems in 60 of 70 patients. In two patients, neither system was accurate. In eight patients, one of the two systems was considered inaccurate. Of these, the magnetic system was considered inaccurate three times and the optical system five times. CONCLUSION: Magnetic referencing and tracking was found to be comparable with optical tracking both with regard to calculated and true surgical accuracy. Interference from metal objects in the magnetic field was seen rarely.

Humans↗
PubMed2003

Shifting of puncture site in the fossa ovalis during radiofrequency catheter ablation: intracardiac echocardiography-guided transseptal left heart catheterization.

Intracardiac echocardiography (ICE) serves as an adjunct to fluoroscopy for electrophysiological procedures by identifying critical anatomic landmarks and confirming catheter-endocardial contact. In the present study, we investigated the usefulness of ICE for radiofrequency catheter ablation. ICE was utilized to guide transseptal puncture in 19 patients undergoing radiofrequency catheter ablation. The fossa ovalis, which was one critical anatomic landmark, had an average vertical diameter of 18.5 +/- 6.9 mm and an average horizontal diameter of 10.0 +/- 2.4 mm, as measured by ICE and fluoroscopy. Although there was only a small shift of the puncture site in the horizontal direction, the puncture site shifted towards the upper edge of the fossa ovalis for 17 patients (89%). Furthermore, we could verify that the distance between the apex of the tent-shape formed by the pressure of the puncture needle in the fossa ovalis and the left atrial wall opposing it was sufficient to carry out the procedure safely. Confirming the puncture site using ICE is useful in carrying out transseptal left heart catheterization safely.

Atrial Fibrillation↗
PubMed1999

Localization and characterization of intracerebral cavernous angiomas by intra-operative high-resolution colour-duplex-sonography.

The aim of this prospective study was to evaluate the reliability of high-resolution Colour-Duplex-Sonography (= CDS) in intra-operative localization, guiding and characterization of intracerebral cavernous angiomas (= CA). During a time period from 5/93 to 12/96 a total of 26 patients with 21 supratentorial and 5 infratentorial CA (15 of them deep-seated) were examined intra-operatively by CDS. The study focussed on 1. sonographic characterization, 2. localization in relationship to anatomical landmarks, 3. navigation, 4. correlation of sonographic to magnetic resonance imaging (= MRI), intra-arterial angiography (= DSA) and histological results and 5. control of complete resection. All CA appeared sonographically as hyperechoic lesions without flow-signals in Colour-mode. Imaging of anatomical landmarks as cerebral sulci, brain stem, insular cistern, falx, ventricles and vessels could be used for precise localization and successful guiding to 15 deep-seated lesions. The correlation of the size between MRI and CDS was excellent (1.4 mm mean difference, range from 0 to 5 mm). All 4 associated venous anomalies, as verified by pre-operative DSA, could be visualized and identified by CDS. The completeness of exstirpation was controlled sonographically in 14 cases and confirmed by MRI (= 10) and CT (= 4). This study provides the first comprehensive intra-operative characterization of CAs by CDS and correlation to MRI and DSA. Furthermore it demonstrates the reliability of CDS for intra-operative localization and guiding as well as its potential to control the complete exstirpation.

Adolescent↗