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Biomedical subjects

S W Schatz

Publications and source records attributed to S W Schatz.

12 recordsLinked to original sources
PubMed1997

Comparison of 810 nm and 1064 nm wavelengths for interstitial laser photocoagulation in rabbit brain.

BACKGROUND AND OBJECTIVE: This laboratory animal study is a comparison of Nd:YAG 1064 nm and diode 810 nm laser wavelengths in brain interstitial laser photocoagulation (ILP). Specific goals were to identify potential complications and physical characteristics of the thermal damage at both wavelengths prior to undertaking a clinical trial in humans. STUDY DESIGN/MATERIALS AND METHODS: A total of 41 ILP illuminations were performed in vivo in the brains of 33 anesthetized rabbits using plane-cut fiber tips implanted directly or through catheters, and diffusing fiber tips. Delivered powers ranged from 1.1 to 4.2 W. Exposures ranged from 300 to 900 s. Survival ranged from 0 to 48 h. Experiments were performed in animals with and without VX-2 brain tumors. RESULTS: Thermal damage from 1.1 W at 810 nm was similar to that from 1.6 W at 1064 nm, but more pronounced. With plane-cut fiber tips, there was a greater propensity for severe physical effects (smoke, charring, bubbling, surface damage) at 810 nm than at 1064 nm, yet hemorrhage, thrombosis and vapor dissemination were observed at both wavelengths, in both normal brain and tumor. CONCLUSIONS: For ILP in brain, 1064 nm may be better suited than 810 nm, although both are questionable with plane-cut-fiber tips. Compactness and portability may be the only valid reasons for using laser diodes operating around 810 nm. At 1064 nm, the power delivered from plane-cut fiber tips should be less than 1.5 W, necessitating long exposures, or else an open catheter should be used. Fiber tips with distributed emission may be preferred, provided structural integrity can be maintained.

Animals↗
PubMed1996

The sensitivity of normal brain and intracranially implanted VX2 tumour to interstitial photodynamic therapy.

The applicability and limitations of a photodynamic threshold model, used to describe quantitatively the in vivo response of tissues to photodynamic therapy, are currently being investigated in a variety of normal and malignant tumour tissues. The model states that tissue necrosis occurs when the number of photons absorbed by the photosensitiser per unit tissue volume exceeds a threshold. New Zealand White rabbits were sensitised with porphyrin-based photosensitisers. Normal brain or intracranially implanted VX2 tumours were illuminated via an optical fibre placed into the tissue at craniotomy. The light fluence distribution in the tissue was measured by multiple interstitial optical fibre detectors. The tissue concentration of the photosensitiser was determined post mortem by absorption spectroscopy. The derived photodynamic threshold values for normal brain are significantly lower than for VX2 tumour for all photosensitisers examined. Neuronal damage is evident beyond the zone of frank necrosis. For Photofrin the threshold decreases with time delay between photosensitiser administration and light treatment. No significant difference in threshold is found between Photofrin and haematoporphyrin derivative. The threshold in normal brain (grey matter) is lowest for sensitisation by 5 delta-aminolaevulinic acid. The results confirm the very high sensitivity of normal brain to porphyrin photodynamic therapy and show the importance of in situ light fluence monitoring during photodynamic irradiation.

Aminolevulinic Acid↗
PubMed1995

Gustatory facial sweating subsequent to upper thoracic sympathectomy.

Gustatory facial sweating has been described as a consequence of upper thoracic sympathectomy. Patients may also develop compensatory hyperhidrosis, sensory deficits, nipple hypersensitivity, and Horner's syndrome. In this article, we have reviewed three patients with reflex sympathetic dystrophy who developed gustatory facial sweating subsequent to endoscopic T2 and T3 ganglionectomy. This article also discusses the possible mechanisms of gustatory facial sweating.

Adult↗
PubMed1995

Preliminary experience with percutaneous laser disc decompression in the treatment of sciatica.

OBJECTIVE: To examine the usefulness of percutaneous laser decompression of a herniated lumbar intervertebral disc. DESIGN: A case series. SETTING: A university-affiliated hospital. PATIENTS: Sixteen patients with clinical and radiologic evidence of herniated lumbar intervertebral discs. INTERVENTIONS: Percutaneous introduction of a fine optical fibre into a herniated lumbar disc and delivery of short pulses of laser energy. MAIN OUTCOME MEASURE: The relief of intractable leg pain. RESULTS: Nine of 14 patients with intractable leg pain experienced total relief after percutaneous laser disc decompression. Four patients required subsequent microsurgical discectomy, and one required a decompressive laminectomy. Of the two patients who had back pain as their major complaint, one required microsurgical discectomy after laser disc decompression. CONCLUSIONS: Percutaneous laser disc decompression can relieve sciatica caused by a herniated intervertebral disc. The technique requires limited use of health resources. Preliminary results suggest that an early return to work can be expected in patients successfully relieved of their leg pain.

Adult↗
PubMed1993

Comparison of magnetic resonance images and the histopathological findings of lesions induced by interstitial laser photocoagulation in the brain.

Interest has developed in using magnetic resonance (MR) imaging to monitor the volume of tissue destroyed by interstitial laser photocoagulation (ILP). In these experiments, ILP was induced in the normal brains of 9 anesthetized cats by delivering 1.5 W of continuous-wave Nd:YAG laser energy (1,064 nm) from a single 400-microns core optical fiber for 1,000 s. The irradiations were monitored using proton spin-echo MR imaging during and immediately after ILP and at postirradiation survival times of 2, 5, and 14 days. At 2 days postirradiation, the necrotic thermal lesion consisted of a central cavity surrounded by 2 concentric zones of coagulative necrosis, one dense and the other dispersed. The lesion shrank and the zonal appearance became less obvious over the 14 day survival period. An enhancing halo on contrast-enhanced T1-weighted images acquired immediately postirradiation best approximated the total lesion diameter at 2 days. These images also indicated that the volume of tissue destroyed during ILP corresponded better to the necrotic volume determined at 2 days than at 5 days and 14 days postirradiation. T2-weighted images acquired during and immediately after ILP consistently underestimated the total lesion diameter at 2 days.

Animals↗
PubMed1992

Magnetic resonance imaging of interstitial laser photocoagulation in brain.

Magnetic resonance (MR) imaging can be used to monitor the development of thermal lesions induced in tissue using interstitial laser photocoagulation (ILP). A potential application for ILP is the treatment of surgically inaccessible brain tumors. For the successful clinical application of MR-monitored ILP, it is necessary to relate MR images of ILP lesions to the actual induced lesions. In this preliminary study we performed ILP in the normal brains of anesthetized cats by delivering interstitially 1.0, 1.5, and 2.0 W of continuous-wave Nd:YAG laser energy (1,064 nm) for 1,000 s via a plane-cut 400 microns core optical fiber. At 48 h post-irradiation the lesions consisted of four sharply demarcated concentric zones of thermal damage. Lesion diameter increased linearly with delivered power. T2-weighted proton spin-echo images acquired during ILP showed a region of complete or near signal loss that underestimated the actual lesion at 48 h. Gadolinium-enhanced T1-weighted spin-echo images acquired immediately post-irradiation showed the actual lesion precisely.

Animals↗
PubMed1992

Transaxillary endoscopic laser sympathectomy.

The authors describe a technique of achieving sympathetic denervation of the upper limbs in a 20-year-old woman with hyperhidrosis. A thoracoscope was inserted through a short incision in the axilla. A fibreoptic wave guide was passed through the thoracoscope to allow photocoagulation of the second thoracic sympathetic ganglion by Nd:YAG laser irradiation. The procedure was well tolerated and subsequent scar formation was unobtrusive.

Adult↗
PubMed1977

A modification of the Guiot-Gillingham stereotaxic frame to allow of angular insertion.

A method of modification of the Guior-Gillingham Stereotaxic frame is described, which will allow of angular insertion of a leucotome or electrode. In our experience, this has prevented the complication of radiation damage and hemianopia and it also permits greater flexibility in the operative approach to structures at or near the midline.

Stereotaxic Techniques↗
PubMed1977

Experience with early anterior operation in acute injuries of the cervical spine.

Of 101 patients with acute injury to the cervical spine below the level of the axis, 74 were selected for anterior operation to ensure stability and comfort and to decompress the neural elements when indicated. Forty-six of the patients underwent a Cloward fusion at the level of the injury. Twenty-eight were treated by bar graft fusion. The indications for these procedures and the techniques involved are outlined. A successful operative result was achieved primarily in 65 of the 74 patients and eventually in 73 patients. The management mortality for patients treated by anterior operation was 2-7 per cent. The advantages of these procedures are the achievement of comfort, the facilitation of early rehabilitation, the maintenance of bony alignment and the preservation and maximal recovery of neurological function.

Adolescent↗