Biomedical subjects

S Y To

Publications and source records attributed to S Y To.

6 recordsLinked to original sources

PubMed1992

Monoclonal antibody-coated magnetite particles as contrast agents for MR imaging and laser therapy of human tumors.

Attempts to improve human tumor detection by non-radioactive magnetic resonance techniques have led several investigators to develop antibody-linked paramagnetic contrast agents. Initial studies focused on gadolinium conjugated to monoclonal antibodies. However, very high levels of this contrast agent were needed to significantly reduce proton relaxation times and obtain improved MR images. The use of magnetite (Fe 3O 4) as an MR contrast agent provides a magnetic moment that is approximately one order of magnitude larger than gadolinium. In this study monoclonal antibodies 44 x 14 (specific for squamous cell carcinoma) and 436G10 (specific for melanoma) were obtained from ammonium sulfate precipitation of tumor ascitic fluid. Equal volumes of magnetite solution (1.87 mg Fe/ml) and antibody solution 44 x 14 (5.24 mg protein/ml) and 436G10 (0.64 mg protein/ml) were mixed and sonicated. The 44 x 14-magnetite and 436G10-magnetite solutions were then added to equal volumes of M20 and P3 squamous cell carcinoma cell lines. T1 and T2 values were obtained on a Praxis II NMR spectrometer equipped with a 10 mm probe and 0.25 Tesla permanent magnet. The T2 relaxation times of the magnetite-antibody-cell mixtures were 31 ms with an R = 0.985 for both experimental samples. Our results demonstrate a significant decrease in T2 by binding of the magnetite-coated antibodies to these melanoma and carcinoma cells in vitro. The possibility of detecting subclinical local and metastatic disease with magnetite linked to monoclonal antibodies followed by MRI guided laser tumor ablation therapy may render this technique clinically attractive for treatment of deep-seated tumors.

Antibodies, Monoclonal↗

PubMed1991

Photodynamic therapy using rhodamine-123 as a new laser dye: biodistribution, metabolism and histology in New Zealand rabbits.

Rhodamine-123 (Rh-123) has been tested recently as a new laser dye for photodynamic therapy of human tumors in vitro and in vivo. Prior to initiation of clinical studies of this technique, we evaluated the biodistribution, metabolism, and pathological changes of Rh-123 in rabbits after systemic, repetitive injections of the dye in escalating doses. At doses between 0.1 to 1 mg/kg of Rh-123 injected intramuscularly (IM) daily for 5 days, no local or systemic toxicity was observed during the 4 weeks of follow-up. The peak concentrations of Rh-123 in micrograms/g of tissue was distributed as follows: kidney (3.24) greater than heart (2.24) greater than spleen (1.77) greater than lung (0.61) greater than liver (0.38) greater than skin (0.30) greater than skeletal muscle (0.17) greater than genitals (0.13) greater than brain (0.04). The elimination of Rh-123 was very rapid, with the dye falling to 2.7% of peak concentration at 72 hours in the kidneys, and to undetectable levels at 240 hours postinjection in all organs, except the skin, which retained 3% of the peak level at 240 hours. The low toxicity and rapid metabolism of Rh-123 in this preclinical model suggests that the dye and Argon laser may represent an effective combination for treatment of superficial malignancies.

Animals↗

PubMed1990

Interstitial laser phototherapy assisted by magnetic resonance imaging: a new technique for monitoring laser-tissue interaction.

The rapid technological advances of magnetic resonance imaging, laser fiberoptics, and compatible probes may allow treatment of deep and sometimes surgically unreachable tumors of the head and neck with minimal morbidity through interstitial laser phototherapy. In this study, a new application of magnetic resonance imaging was developed to monitor and quantify laser-induced tissue damages. Pig skin was exposed to increased levels of argon laser (514.5 nm) at energy densities between 62.5 and 375 J/cm2 as determined by an accurate and reproducible method of dosimetry. Thermal profiles were recorded using an infrared sensor and T1- and T2-weighted magnetic resonance images were taken; afterward, biopsies were performed to quantitate the level of tissue damage. Our results demonstrate that above a certain threshold of laser energy, the magnetic resonance imaging findings are temperature dependent. Appropriate development of a scale matching laser energies, temperature profiles, T1- and T2-weighted magnetic resonance images, and histological quantitation of tissue destruction will allow us to optimize the three-dimensional control and monitoring of laser-tissue interactions.

Animals↗

PubMed1988

Simultaneous measurements of strains on two surfaces of tendons and ligaments.

An optical rear projection device, coupled with a video dimensional analyzer (VDA) system, was developed for simultaneous measurement of tensile strains on opposite surfaces of tendons and ligaments. Stress-strain behaviors of the tissue based on the strains measured on either surface were determined and compared. Data obtained from canine femur-medial collateral ligament-tibia complexes (FMT) and isolated chicken flexor tendons revealed that the strains on opposite surfaces of these parallel fiber soft connective tissues were similar during a uniaxial tensile test.

Animals↗

PubMedDate not supplied

MR compatible winged infusion set.

Winged infusion sets are useful for short term venous infusion in a variety of applications and may be used without problem during CT scanning, ultrasound, or most other medical imaging applications. Drawbacks of using these standard winged infusion sets during MR scanning are torque and imaging artifacts. We describe a new MR compatible infusion set that overcomes these problems.

Equipment Design↗

PubMedDate not supplied

Volume growth rate of acoustic neuromas on MRI post-stereotactic radiosurgery.

Of the approximately 160 acoustic neuroma patients treated with stereotactic radiosurgery in the world up to 1987, 8 patients at UCLA Medical Center have had two or more magnetic resonance scans at least one year apart available for study (all 8 patients were treated with stereotactic radiosurgery for acoustic neuromas by the Department of Neurosurgery at the Karolinska Hospital, Stockholm, Sweden). The followup time after radiosurgery ranged from 4 to 8 years. The volume doubling rate post-stereotactic radiosurgery was calculated to be slow (763 to 888 days) in two patients, virtually arrested in five patients (doubling times larger than 2500 days) and negative (-563 days) in one patient indicating a shrinking tumor. Due to the limited sample size no radiological finding or clinical data correlated with the volume doubling times. A control patient that had no treatment for her tumor had a doubling time of 217 days for comparison.

Adult↗