Stereolithographic (SL) biomodeling is a new technology that allows three-dimensional (3D) imaging data to be used in the manufacture of accurate solid plastic replicas of anatomical structures. The authors describe their experience with a patient series in which this relatively new visualization method was used in surgery for cerebral aneurysms. Using the rapid prototyping technology of stereolithography, 13 solid anatomical biomodels of cerebral aneurysms with parent and surrounding vessels were manufactured based on 3D computerized tomography scans (three cases) or 3D rotational angiography (10 cases). The biomodels were used for diagnosis, operative planning, surgical simulation, instruction for less experienced neurosurgeons, and patient education. The correspondence between the biomodel and the intraoperative findings was verified in every case by comparison with the intraoperative video. The utility of the biomodels was judged by three experienced and two less experienced neurosurgeons specializing in microsurgery. A prospective comparison of SL biomodels with intraoperative findings proved that the biomodels replicated the anatomical structures precisely. Even the first models, which were rather rough, corresponded to the intraoperative findings. Advances in imaging resolution and postprocessing methods helped overcome the initial limitations of the image threshold. The major advantage of this technology is that the surgeon can closely study complex cerebrovascular anatomy from any perspective by using a haptic, "real reality" biomodel, which can be held, allowing simulation of intraoperative situations and anticipation of surgical challenges. One drawback of SL biomodeling is the time it takes for the model to be manufactured and delivered. Another is that the synthetic resin of the biomodel is too rigid to use in dissecting exercises. Further development and refinement of the method is necessary before the model can demonstrate a mural thrombus or calcification or the relationship of the aneurysm to nonvascular structures. This series of 3D SL biomodels demonstrates the feasibility and clinical utility of this new visualization medium for cerebrovascular surgery. This medium, which elicits the intuitive imagination of the surgeon, can be effectively added to conventional imaging techniques. Overcoming the present limitations posed by material properties, visualization of intramural particularities, and representation of the relationship of the lesion to parenchymal and skeletal structures are the focus in an ongoing trial.
Simultaneous 3-dimensional printing is the most promising rapid prototyping technique to produce biomodels that meet the high demands of neurovascular surgery.
(1) Aims: To test a newly designed helical-wire hook electrode implanted in the bladder wall to induce contraction and promote voiding. (2) Methods: In three minipigs with a created lesion of the sacral spinal cord, four electrodes were implanted in the bladder wall, ventral to the trigone. Stimulation tests were conducted initially in conscious pigs, and later after general anesthesia. (3) Results: Electrical stimulation in the conscious animals on postoperative days 4 and 7 at 40 Hz was limited to 10 mA, because of abdominal, leg, and anal contractions with animal discomfort; bladder contractions were not induced. Electrical stimulation on postoperative days 9 and 28 at 60 mA under anesthesia induced sustained vesical wall contractions with bladder pressure variations, but without voiding. Simultaneous abdominal contractions occurred, with strong leg and anal contractions. Subsequent stimulation with a single set of electrodes or at 20 Hz induced less vesical pressure response. At autopsy, the electrodes had not migrated, and extraction forces were high, at 7.9 ± 0.9 Newtons (n = 12). (4) Conclusions: Our 28-day study has confirmed the utility of the new electrode design, preventing migration from the bladder wall and making it suitable for long-term electrode implants.
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