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Biomedical subjects

Y Yuri

Publications and source records attributed to Y Yuri.

12 recordsLinked to original sources

Generating ultralow-emittance ion beams in a storage ring.

Laser cooling of heavy-ion beams in a storage ring is systematically studied with a multiparticle simulation code where not only exact lattice characteristics and space-charge forces but also realistic laser-ion interactions can be incorporated. The resonant coupling method is applied in order to extend the powerful longitudinal photon pressure to the transverse degrees of freedom. It is shown that, in spite of a space-charge-induced tune shift, the synchrobetatron resonance mechanism required for fast damping of transverse oscillations operates throughout the cooling process. Extremely efficient three-dimensional cooling of stored ion beams is thus feasible. It is demonstrated that, at low line density, normalized root-mean-squared emittances of the order of 10(-12) m.rad can be reached in all three directions by employing only existing technologies.

Journal Article↗

One-dimensional ordering of ultra-low-density ion beams in a storage ring.

The two-particle model, first introduced by Hasse, is employed to predict the beam temperature at which a one-dimensional ordered state of ions will be established in a cooler storage ring. The proposed state does not have the ions (in the beam frame) at rest, but simply has them not passing each other; i.e., remaining in the same (ordered) sequence. The model is applicable to an ultra-low-density beam where collective Coulomb interactions are negligible. It is pointed out that the nature of the anomalous beam behavior observed in electron-cooling experiments at GSI (Darmstadt) and MSL (Stockholm) is approximately free from such parameters as the lattice design, ion species, beam density, and energy. On the basis of the model, which is put in Hamiltonian form, scaled, and numerically studied, a universal criterion of one-dimensional beam ordering at low line density is derived. Analytic work is employed to explain the numerical results and derives an approximate criterion.

Journal Article↗

Oscillating Coulomb chain in a storage ring.

The dynamic behavior of a bunched one-dimensional crystalline beam is studied theoretically. It is shown that, owing to the existence of momentum dispersion, a Coulomb chain traveling in a storage ring performs a complex periodic oscillation whenever it is exposed to a longitudinal radio-frequency force. The equations of motion are derived to predict the oscillation pattern in an arbitrary lattice structure. The validity of the present theory is confirmed through multiparticle simulations. Various features of an oscillating string beam, such as the lattice-parameter dependence of the orbit, the stability, and critical line density, etc., are also discussed.

Journal Article↗

Laparoscopic microwave thermotherapy on small renal tumors: experimental studies using implanted VX-2 tumors in rabbits.

OBJECTIVE: To investigate the effectiveness of microwave thermotherapy on implanted renal VX-2 tumors. METHODS: Fifteen rabbits with implanted renal VX-2 tumors were divided into three groups according to the type of therapy: nephrectomy, laparoscopic microwave thermotherapy, and no treatment. Both the anticancer effect and safety were compared among these groups. RESULTS: The survival rate in the laparoscopic microwave thermotherapy group was significantly higher than that in the no-treatment group, and was the same as that in the nephrectomy group. The serum creatinine level did not increase after microwave therapy. CONCLUSION: Laparoscopic microwave thermotherapy may be useful for a nephron-salvaging treatment in small implanted renal VX-2 tumors in rabbits.

Animals↗

Ultrasound-guided microwave thermotherapy on a VX-2 carcinoma implanted in rabbit kidney.

A temperature greater than 60 degrees C was maintained for 60 s within a 5-mm radius of a microwave electrode implanted in a rabbit kidney using 2450 MHz at 100 W for 30 s. Histological examination revealed complete coagulation necrosis in that area. VX-2 cells were inoculated into the kidneys of 10 rabbits. One week later, five rabbits received ultrasound-guided microwave thermotherapy, and the remaining five rabbits received no treatment. All rabbits with microwave thermotherapy had a complete response to treatment while all rabbits without therapy died of cancer within 6 weeks of the VX-2 implantation. These results indicate that ultrasound-guided microwave thermotherapy has the potential of being a nephron-salvaging treatment for small renal tumors.

Animals↗

Experimental study of microwave coagulation of a VX-2 carcinoma implanted in rabbit kidney.

This paper describes the results of an experimental study of the microwave coagulation of VX-2 renal tumors implanted in rabbits. The rabbits undergoing microwave treatment exhibited a satisfactory survival rate and a complete response to treatment, as verified by histological examination. All the rabbits receiving no treatment died within 6 weeks of implantation of the VX-2 carcinoma. These results indicate that microwave coagulation may be a curative method of treatment for a relatively small renal tumor. Intraoperative real-time ultrasonic scanning permits the percutaneous microwave coagulation of renal cancer in a clinical situation.

Animals↗

Local control of prostate cancer with transurethral intracavitary radiation therapy.

As of January 1986, 13 patients with adenocarcinoma of the prostate had been treated in our clinic by remote after-loading transurethral high dose rate radiotherapy using a 60Co source. Of these patients, four were at stage B2, three at stage C, three at stage D1, and three at stage D2. The mean total dose of transurethral radiotherapy was 35.2 Gy to the most distant prostatic capsule from the source. Three patients with stage D1 disease and one patient with stage C disease received additional external radiation with a total dose of 20 Gy to the prostate and 40 Gy to the pelvis. Local tumor response proved rapid and satisfactory as verified by rectal examination, ultrasonography, and needle biopsy. Serious complications such as proctitis, cystitis, incontinence, and urethral stricture were not evident during the average follow-up term of 34.9 months.

Adenocarcinoma↗