A training model head of plaster of Paris for stereotactic localization.
ABSTRACT A head model for experiencing stereotactic localization will supply familiarity with stereotactic instruments and self confidence for attempters of stereotaxy before real experience.
Plaster of Paris was molded as a model head in a plastic ball. Then, it was partly chipped at its superior half, and metal pieces were inserted into those chipped surfaces. Later, the stereotactic frame was applied, and axial computed tomographic scanning was obtained. The metal pieces seen on scans were selected as targets, and their coordinates were calculated using the software of the stereotactic equipment. Lastly, the stereotactic needle was introduced with these coordinates for investigation of targeting.
The model of plaster of Paris head was very suitable for rigid frame fixation. The metal pieces in the model head were clearly observed on computed tomographic scans. The stereotactic biopsy needle introduced with the perviously calculated coordinates was always successful in true targeting.
This easily performed model head supplied us with familiarity with our stereotactic apparatus and convinced us for further attempts. This kind of model and more complicated ones may help for stereotaxy training in neurosurgery.
Article: Biomodel-guided stereotaxy.[show abstract] [hide abstract]
ABSTRACT: To simplify the practice of stereotactic surgery by using an original method, apparatus, and solid anatomic replica for trajectory planning and to validate the method and apparatus in a laboratory and clinical trial. The patient is marked with fiducials and scanned by using computed tomography or magnetic resonance imaging. The three-dimensional data are converted to a format acceptable to stereolithography. Stereolithography uses a laser to polymerize photosensitive resin into a solid plastic model (biomodel). Stereolithography can replicate blood vessels, soft tissue, tumor, and bone accurately (<0.8 mm). A stereotactic apparatus is referenced to fiducials replicated in the biomodel. The trajectory for the intervention is determined and saved. The apparatus is attached to the patient fiducials, and the intervention is replicated. Three types of apparatus (template, Brown-Roberts-Wells frame, and D'Urso frame) were tested on phantoms and patients requiring the excision/biopsy of tumors. The localization errors determined from the phantom studies were template, 0.82 mm; Brown-Roberts-Wells frame, 1.17 mm; and D'Urso frame, 0.89 mm. The surgeons reported that clinical use of the template and D'Urso frame was accurate and ergonomic. The Brown-Roberts-Wells frame was more difficult to use and somewhat inaccurate. Biomodel-guided stereotaxy has significant advantages. It is performed quickly; it is based on simple, intuitive methodology; it enhances visualization of anatomy and trajectory planning; it enhances patient understanding; it uses inexpensive equipment; it does not require rigid head fixation; and it has greater versatility than known techniques. Disadvantages are biomodel cost and a manufacturing time of 12 to 24 hours.Neurosurgery 05/1999; 44(5):1084-93; discussion 1093-4. · 2.53 Impact Factor
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ABSTRACT: The use of image-guided systems (IGS) for brain biopsy has increased in neurosurgical practice. We sought to evaluate the accuracy of a plastic, disposable burr hole mounted guide for stereotactic biopsy using an IGS and compare the results of different targeting methods with those of frame based localization. MRIs were performed on a skull model with mounted fiducials with a stereotactic frame in place and data was loaded onto the Stealth IGS. The model was placed in a Mayfield head holder and fixed to the OR table. Registration of imaging to physical space was carried out. Using three different targeting methods on the Stealth IGS, the distance between the target and the predicted position of the target, the offset error, was measured in three dimensions and confirmed by 2 observers. A sum of squares for the 3 offset errors in all planes was used to calculate the summed vector error. The same MRI dataset used with the Cosman-Roberts-Wells (CRW) stereotactic frame for comparison. The summed vector error was calculated in the same manner to compare the accuracy of targeting with these guides to the frame-based CRW system. For frameless stereotaxy using the "Straight- guide 4 2D" targeting method the mean error was 2.58 +/- 0.51 mm (n=12). The vector error was 5.23 +/- 0.54 (n=4). For the registration set and target using the "Offset- guide 4 2D" targeting method the mean error was 1.66 +/- 0.36 mm (n=12). The vector error was 3.32 +/- 0.72 (n=4). The best localization was obtained with the "probe's eye" planning and targeting. The mean error was 0.33 +/- 0.16 mm (n=12). The vector error was 1.0 +/- 0.28 (n=4). We found a statistical difference between the different techniques (P<0.001) (Kruskal-Wallis One Way Analysis of Variance on Ranks). An all pairwise multiple comparison procedure (Holm-Sidak method) found an overall significance level = 0.05. For the frame-based CRW the mean error from the target was 1.03 +/- 0.19 mm (n=18) and the mean target localization error vector was 2.23 +/- 0.14 (n=6). We found a statistically significant difference between NDT guide "Probes Eye" vs. the MR-CRW (P=0.003, Mann-Whitney Rank Sum Test). These results indicate that using MR imaging, surgical planning software and the skull mounted Navigus-DT with the probe's eye view option for targeting, localization accuracy appears to fall within acceptable ranges compared with frame-based methods which have been the standards for stereotactic brain biopsy and functional neurosurgery. Furthermore, there may be considerable differences in accuracy between different targeting methods.Journal of Neuro-Oncology 01/2006; 76(1):65-70. · 3.12 Impact Factor
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ABSTRACT: Stereotactic procedures have been prevalent in neurosurgical practice for a prolonged time period. With the advent of new custom-made frames designed for morphologic and functional neurosurgical procedures, its extended use in the pediatric population is becoming increasingly popular. However, there is still a need for sophistication in design and instrumentation. We describe a novel method of a plaster of Paris mould for stereotactic frame fixation, which can be a useful adjunct during frame fixation. It primarily accounts for a remarkable variation in skull shapes and sizes seen in the pediatric population undergoing stereotaxy besides many other advantages.Pediatric Neurosurgery 01/2005; 41(5):229-32. · 0.42 Impact Factor