Stereotactic

Amorphous stereotactic polymers can crystallise, in which condition neighbouring chains are parallel. Because of the unavoidable chain entanglement in the amorphous state, only modest alignment of amorphous polymer chains is usually feasible, and moreover complete crystallisation is impossible under most circumstances, and thus many polymers are semi-crystalline. It is this feature, semicrystallinity, which distinguished polymers most sharply from other kinds of materials. Crystallisation can be from solution or from the melt, to form spherulites, or alternatively (as in a rubber or in high-strength fibres) it can be induced by mechanical means. This last is another crucial difference between polymers and other materials. Unit cells in crystals are much smaller than polymer chain lengths, which leads to a unique structural feature which is further discussed below. 

Radiation therapy is the treatment of choice for most patients with brain metastases. Most patients receive whole-brain radiation because the majority of brain metastases are multifocal. Another method known as stereotactic radiosurgery provides intense focal radiation, typically using a linear accelerator or gamma knife, in patients who cannot tolerate surgery or have lesions that are surgically inaccessible (e.g., in the brain stem). 

In another series of experiments, rats trained to discriminate LSD (96 pg/kg i.p.) from saline were implanted stereotactically with cannulae aimed at the DRN (59). The ability of the peripherally elicited LSD cue to generalize to LSD injected directly into the DRN was then evaluated over a wide range of doses (2-60 jtg/kg). The results are shown in Fig. 2. Interestingly, the dose of LSD injected via the cannulae required to produce DS control was extremely high,... 

Lederman G, Arbit E, Odaimi M, Wertheim S, Lombardi E. Recurrent glioblastoma multiforme potential benefits using fractionated stereotactic radiotherapy and concurrent taxol. Stereotact Fund Neurosurg 1997 69(1—4 Pt 2) 162-174. 

Lederman G, Arbit E, Odaimi M, Lombardi E, Wrzolek M, Wronski M. Fractionated stereotactic radiosurgery and concurrent taxol in recurrent glioblastoma multiforme a preliminary report. Int J Radiat Oncol Biol Phys 1998 40(3) 661-666. 

Clarification of the role of radiation dose escalation particularly using innovative techniques such as intensity modulated radiation therapy (IMRT) and either single dose or fractionated stereotactic radiation. 

Kelly P, Daumas-Duport C, Kispert D, Imaging-based stereotactic biopsies in untreated intracranial glioneoplasm. J Neurosurgery 1987 66 865-875. 

Vandewalle, V., van der Linden, C., Groenewegen, H.J., and Cae-maert, J. (1999) Stereotactic treatment of Gilles de la Tourette syndrome by high frequency stimulation of thalamus. Lancet 353 724. 

Particles emitted from radioactive isotopes are generally too low in energy to provide the penetration required for conventional treatments of tumors with external radiation beams. Most external beam radiation therapies are performed with high-energy x-rays or electrons produced with compact linear accelerators with accelerating potentials between about 4 and 20 MeV. One notable exception is certain devices designed for stereotactical radiosurgery or radiation therapy of superficial tumors that use cobalt-60 y-rays. The... 

Improvements in the physical selectivity, from orthovoltage x-ray to cobalt-60 and high-energy linear accelerators, combined with more powerful diagnostic tools and radiation delivery methods have continuously improved the results of photon therapy (3-D or inverse planning, conformal- and intensity-modulated radiation therapy, and stereotactic methods). The safety and the reliability of photon therapy are well established. 

When making this comparison, one must remain aware of the modern developments in photon therapy such as conformal therapy (3DCRT), IMRT, tomotherapy, gamma knife, stereotactic x-ray techniques, iodine-125 (and palladium-103) seeds and plaques, etc. 

Current neurosurgical techniques involve stereotactic surgery and permit a high degree of accuracy with fewer side effects. Thus, these procedures are... 

Ballantine HT, Bouckoms AJ, Thomas EK, et al Treatment of psychiatric illness by stereotactic cingulotomy. Biol Psychiatry 22 807-819, 1987 Ballenger JC Medication discontinuation in panic disorder. J Chn Psychiatry 53 (suppl) 26-31, 1992... 

Bouckoms Al The role of stereotactic cingulotomy in the treatment of intractable de-pression, in Refractory Depression (Advances in Neuropsychiatry and Psychopharmacology Series, Vol 2. Edited by Amsterdam JD. New York, Raven, 1991, pp 233-242... 

Technical permissibility (the availability of proper stereotactic, imaging, electrophysiological, and other apparatus necessary to carry out the surgical treatment) (249)... 

Korzenev AV, Shoustin VA, Anichkov AD, et al. Differential approach to psychosurgery of obsessive disorders. Stereotact Funct Neurosurg 1997 68 226-230. 

Levy, R., Leiphart, J., Dills, C. Analgesic action of acute and chronic intraspinally administered opiate and a2-adrenergic agonists in chronic neuropathic pain, Stereotact. Funct. Neurosurg. 1994, 62, 279-289. 

Kalapurakal JA, Silverman CL, Akhtar N, Laske DW, Braitman LE, Boyko OB, Thomas PR. Intracranial meningiomas factors that influence the development of cerebral edema after stereotactic radiosurgery and radiation therapy. Radiology 1997 204(2) 461-5. 

Whaley, D.H., D.L. Adamczyk, and E.A. Jensen. 2003. Sonographically guided needle localization after stereotactic breast biopsy. Am J Roentgenol 180 352. 

Miles J. Intrathecal treatment for spasticity. Stereotact Funct Neurosurg. 2001 76 246-248. 

The transduction of neurons of the brain and spinal cord by rAAV has also been remarkably efficient in a number of rodent and non-human primate models (Kaplitt et al., 1994 Peel et al., 1997 During et al., 1998 Klein et al., 1998). Stereotactic injection of rAAV into the substantia nigra or striatum has been used to deliver potentially therapeutic genes in animal models of Parkinson Disease (Kaplitt et al., 1994 During et al., 1998 Klein et al., 1998). These studies have shown efficient transgene expression with functional correction in both rodent and primate models. While the transduction of localized areas of the brain or spinal cord appears to be readily practical, the delivery of rAAV to wider regions of the brain, that may be needed for patients with some metabolic disorders, remains challenging. 

Kandel E.I. Functional and stereotactic neurosurgery, Plenum Medical Book Co, NY, London, 1989. 

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