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Biomedical subjects

R S Wolfstein

Publications and source records attributed to R S Wolfstein.

At least 19 recordsLinked to original sources
PubMed1990

TRIPAS: a triapplicator system with relocatable 'hot spot' at tissue depth.

Solving the problem of heat focusing and standardization of the clinical application of hyperthermia requires a mathematical prediction model. The model should include the medium constitutive parameter, and be able to predict positioning of the microwave applicators to optimize treatment planning and provide for reproducible treatment set-up. We present a configuration of 3 applicators subtended by an equilateral triangle in order to target and relocate a 'hot spot' for improved treatment of deep tumors. A simple geometric analysis is illustrated. The microwave beam absorption profile, from the three power sources, was obtained from phantom studies depicting the radiative heat pattern for the triapplicator system (TRIPAS). A complex mathematical model was developed to demonstrate interaction of the beams in the medium. It was observed empirically that under coherent propagation in the near field electromagnetic (EM) waves tend to add at the center, while varying the propagation axial focal length caused a relocation of the summing focal points. Mathematical prediction correlated very well with the phantom studies. SAR values above 100 W/kg were achieved at 12.5 cm phantom depth, creating a relocatable 'hot spot' at the concentric foci of the 3 air cooled horn microwave applicators operating at 300 MHz.

Computer Simulation↗
PubMed1986

Microwave hyperthermia as an adjunct to radiation therapy: summary experience of 256 multifraction treatment cases.

Results in 256 cases of malignant disease treated by multifraction combination hyperthermia-radiation therapy under the supervision of one physician are presented. The overall response rate was 94% including a 62% complete response. Complications specifically ascribed to hyperthermia were minor, and most side effects of combined treatment were radiation dose related. Tumor response was somewhat better for chest wall recurrence (72% CR) and for adenocarcinoma in general (64% CR), but no significant dependence on tumor site or type was found. Most patients were treated with low dose external radiation with hyperthermia given by air cooled microwave applicators or intracavitary antennae operating at 915 or 300 MHz, and some by interstitial microwave antennae plus 192 Ir. Results appeared to be independent of the microwave source employed. Response did depend on radiation dose: complete response rate with 4000 rad was 65%, and with 2000 rad was 42%.

Brachytherapy↗
PubMed1980

Clinical and parametric evaluation of three large-field-of-view cameras.

This paper compares the clinical and parametric performance, at 140 keV, of three different large-field cameras in a single institution. The instruments tested were the Ohio Nuclear 410, Picker 4/15, and Searle LFOV. There were differences noted in both qualitative and quantitative measurements of physical performance, but these differences could not be demonstrated in clinical studies.

Image Enhancement↗
PubMed1979

Critical evaluation of 99mTc glucoheptonate as a brain imaging agent.

99mTc glucoheptonate was used as a brain imaging agent in a consecutive series of 859 patients. Sensitivity was 94% in patients with proved CNS tumors. Static imaging of patients with infarction showed a sensitivity of 62%. When the perfusion study was included, this valve increased to 90%. Overall sensitivity was 83%, specificity 99%, and accuracy 95% without inclusion of perfusion results. When these results were included, overall sensitivity was 93%, specificity 99%, and accuracy 98%.

Brain↗
PubMed1979

Early and delayed Tc-99m glucoheptonate brain scintigraphy: are routine early images indicated?

Both early and delayed Tc-99m glucoheptonate brain images were evaluated in 859 patients in order to determine whether the early imaging with this agent is clinically useful. The results suggest that the early brain images are inferior to the delayed ones in detecting CNS lesions. Use of both, however, may help to differentiate skull or scalp abnormalities from true lesions of the brain.

Adult↗
PubMed1976

Transient brain scan abnormalities in renal dialysis patients.

Two patients on chronic renal hemodialysis developed acute neurologic symptoms and unusual brain scan findings, including very prominent cranial sinuses. Symptoms and scan abnormalities reverted to normal within a few days. The possible mechanisms are discussed.

Adolescent↗
PubMed1976

Technetium-99m-glucoheptonate as a brain-scanning agent: critical comparison with pertechnetate.

Delayed 99mTc-glucoheptonate and pertechnetate scans were evaluated in a paired study for their ability to detect brain lesions. Glucoheptonate was found to be superior in eight of 17 cases of brain tumor and in two of ten patients with cerebral infarction. In addition, early (30 min) 99mTc-glucoheptonate brain scans were compared with delayed studies: the former were inferior in 48% of the cases. We conclude that 99mTc-glucoheptonate is a promising agent for delayed brain scanning, offering better lesion detection than pertechnetate.

Adult↗
PubMed1975

Metastatic hemangiopericytoma associated with microangiopathic hemolytic anemia: review and report of a case.

The hemangiopericytoma is an invasive tumor of vascular origin. No matter how benign the course and how circumscribed the mass, it must be considered a lesion with high malignant potential. In the case report here, a hemangiopericytoma of the pancreas with metastasis to the liver was associated with microangiopathic hemolytic anemia in a 78-year old woman. The anemia may have been present before the onset of metastasis. If so, it could have been a major factor in the breakdown of host response and could have initiated the malignant dissemination. Under these circumstances it could be an indicator of metastasis in patients with previously diagnosed tumors. However, there are many cases of metastatic malignancy associated with this anemia in which the opposite situation holds. The anemia is usually of extracorpuscular origin. Apparently intravascular coagula1ion caused by injury from tumor-cell aggregates in small vessels induces erythrocyte fragmentation in fibrin strands. A vicious cycle of cell fragmentation, vascular injury and fibrin strand formation completes the course. Analysis of the findings should be based upon more than a strictly pathologic approach; it should also be related to the new discoveries in cancer research.

Aged↗
PubMed1975

Reliability of gallium brain scanning in the detection and differentiation of central nervous system lesions.

Both 99mTc-pertechnetate and 67Ga-citrate brain scans were performed in 93 patients with cerebral neoplasms and in 70 others with cerebral infarction or hemorrhage. Tumor detection was clearly better with 67Ga(96%) than with 99mTc(85%). Cerebral infarctions consistently either failed to concentrate 67Ga(67%) of revealed a much lower concentration than the 99mTc study (27%). In 6% of the infarction patients, gallium and technetium scans were equivalent.

Arterial Occlusive Diseases↗