A resistive-anode based position-sensitive Rydberg atom detector.

We describe here the development and characterization of a position-sensitive detector for Rydberg atom experiments. The detector builds on an earlier design that field-ionized incident Rydberg positronium (Ps) atoms and then electrostatically focused the freed positrons onto a micro-channel plate (MCP) detector without the use of a position sensitive anode. In this design, pulses from the MCP are deposited onto a resistive anode, providing a means of measuring the incident particles' x, y positions. The first detector constructed utilized a pair of MCPs in a chevron configuration and was used to observe the focusing of Rydberg Ps atoms from an electrostatic mirror. A second detector, developed for use in a measurement of the 1S-2S interval of Ps, incorporates three MCPs in a Z-stack configuration to produce larger pulses. Using a UV-induced signal, we have characterized the performance of the assembled detectors, finding a spatial resolution of ∼1.4 mm for the largest induced pulses and for pulse widths of ∼7-10 ns FWHM; pulse times can be resolved to better than 1 ns. The Ps induced signal is anticipated to yield pulses ∼5 times larger, which are expected to achieve a spatial resolution of <1 mm. Appropriate lenses could make possible applications involving either imaging a large area or magnifying a small area of the incident Ps spatial distribution.

Detector for positronium temperature measurements by two-photon angular correlation.

We report on the design and characterization of a modular γ-ray detector assembly developed for accurate and efficient detection of coincident 511 keV back-to-back γ-rays following electron-positron annihilation. Each modular detector consists of 16 narrow lutetium yttrium oxyorthosilicate scintillators coupled to a multi-anode Hamamatsu H12700B photomultiplier tube. We discuss the operation and optimization of 511 keV γ-ray detection resulting from testing various scintillators and detector arrangements concluding with an estimate of the coincident 511 keV detection efficiency for the intended experiment and a preliminary test representing one-quarter of the completed array.

Focusing of a Rydberg Positronium Beam with an Ellipsoidal Electrostatic Mirror.

Slow atoms in Rydberg states can exhibit specular reflection from a cylindrical surface upon which an azimuthally periodic potential is imposed. We have constructed a concave mirror of this type, in the shape of a truncated oblate ellipsoid of revolution, which has a focal length of (1.50±0.01) m measured optically. When placed near the center of a long vacuum pipe, this structure brings a beam of n=32 positronium (Ps) atoms to a focus on a position sensitive detector at a distance of (6.03±0.03) m from the Ps source. The intensity at the focus implies an overall reflection efficiency of ∼30%. The focal spot diameter (32±1) mm full width at half maximum is independent of the atoms' flight times from 20 to 60 µs, thus indicating that the mirror is achromatic to a good approximation. Mirrors based on this principle would be of use in a variety of experiments, allowing for improved collection efficiency and tailored transport or imaging of beams of slow Rydberg atoms and molecules.

[Extragonadal germ cell tumor in HIV+ female]. / Tumor de células germinales extragonadal en mujer VIH+.

Extragodanal germ cell tumors (EGCT) are not common, especially among women. Although there is no evidence of relationship between this sort of tumor and HIV infection they can appear at the same time in a patient, because in both cases the maximum incidence occurs in patients in the same age group. We present the case of a 27 years old woman, poly-drug user, with a recently diagnosis of HIV infection, who was admitted to clinic because of infection and shortage of breath, and develops during her hospitalization diarrhoea, generalized tonic-clonic seizure and left hemiparesis. Complementary tests showed us diffuse interstitial pulmonary pattern, mediastinal mass with intrathoracic adenopathies, cerebral tumor and diffuse intestinal enlargement. The breath infection got better with a wide-ranging antibiotic treatment, which included cotrimoxazol and levofloxacin, but the brain tumor didnt get better with the antitoxoplasma treatment. The clinical presentation simulated in the beginning a disseminated lymphoma, in a HIV+ patient; nevertheless, after receiving the result of the biopsy of a supraclavicular adenopathy and a b-HCG, an extragodanal germ cell tumor was diagnosed. We haven't found any case of EGCT in young women infected with HIV in our bibliographical review (MEDLINE).

Luteinizing hormone-releasing hormone antagonist cetrorelix as primary single therapy in patients with advanced prostatic cancer and paraplegia due to metastatic invasion of spinal cord.

OBJECTIVES: To assess the clinical response to luteinizing hormone-releasing hormone (LH-RH) antagonist cetrorelix (SB-75) in patients with advanced carcinoma of the prostate and paraplegia due to metastatic invasion of spinal cord. METHODS: Cetrorelix was given at two different dose regimens to 5 patients with prostatic cancer Stage D2 and paraplegia. Urologic and neurologic examinations, laboratory studies, radiography (myelography), and prostate ultrasonography were carried out. Prostate-specific antigen (PSA) and free testosterone were also measured. RESULTS: In all patients, the neurologic symptoms regressed. The recovery of the thermic and vibratory sensation and motility of the toes was observed. The neurologic improvement continued during the treatment and at 3 months all the patients were able to walk with the aid of a cane. In 1 patient, the myelography showed that the spinal cord compression had disappeared and prostate volume assessed by ultrasonography showed a significant decrease. The bladder function greatly improved in all 5 patients during the treatment with cetrorelix. Baseline levels of luteinizing hormone fell from 9.28 to 1.0 IU/L and those of follicle-stimulating hormone (FSH) fell from 18.28 to 12 IU/L (P < 0.05) after the first day of therapy with cetrorelix. Mean levels of free testosterone were reduced from 52.4 to 14.7 pmol/L (P < 0.005) at 12 hours and to 13.1 pmol/L (P < 0.005) 3 days after the first injection of cetrorelix. A persistent inhibition of gonadotropins and testosterone was maintained during the subsequent 3 months of therapy. The high levels of PSA gradually decreased. CONCLUSIONS: Our results show that LH-RH antagonist cetrorelix causes an immediate lowering of the serum testosterone levels in patients with prostate cancer and metastases in the spinal cord, in whom the LH-RH agonists cannot be used as single drugs because of the possibility of flare-up and appears to be appropriate for long-term therapy.

Responses to the antagonistic analog of LH-RH (SB-75, Cetrorelix) in patients with benign prostatic hyperplasia and prostatic cancer.

Among new highly potent antagonistic analogs of luteinizing hormone-releasing hormone (LH-RH), containing neutral hydrophilic D-ureidoalkyl amino acids such as D-Cit and D-Hci at position 6 and free of edematogenic and anaphylactoid reactions, Ac-D-Nal(2)1, D-Ph(4Cl)2, D-Pal(3)3, D-Cit6, D-Ala10 (LH-RH) (SB-75; Cetrorelix) was shown to be one of the most powerful. In this trial, we evaluated the response to 500 micrograms SB-75 given every 12 hr subcutaneously (sc) for 4 weeks in 11 patients with benign prostatic hyperplasia (BPH), and 6 weeks in 6 prostatic cancer patients (2 stage C, 4 stage D2). In patients with BPH presenting with prostatism and urinary outflow obstruction, there was a noticeable clinical improvement after the first week of SB-75 administration. This improvement continued during the course of treatment. Before therapy with SB-75, the serum levels of prostate-specific antigen (PSA) (6.73 +/- 1.46 ng/ml), acid phosphatases, total (12.67 +/- 1.15 U/l), and prostatic (2.27 +/- 0.34 U/l), were mildly elevated, but declined to normal values at 4 weeks: (2.13 +/- 0.59 ng/ml; P < 0.01), (7.68 +/- 0.89 U/l; P < 0.01), and (1.39 +/- 0.18 U/l; P < 0.01), respectively. Mean prostatic volume assessed by ultrasonography showed a significant decrease in all patients from 67.84 +/- 8.86 to 37.92 +/- 8.52 cm3; P < 0.01, which represents a reduction of 44%. In patients with prostate cancer, after the first week of therapy with SB-75, we observed a significant decrease in bone pain, relief in urinary outflow obstruction, and reversal of the signs of prostatism. Subjective improvement continued during the following weeks of treatment, so that the patients no longer needed analgesics. PSA, acid, and alkaline phosphatases gradually fell, achieving nearly normal values at 6 weeks. Initial serum testosterone levels in BPH and prostatic cancer patients were within normal limits, but during treatment with the antagonistic analog SB-75, fell to castration values. A major fall in free testosterone levels was observed after the first dose; the maximal inhibition was seen after 6-12 hr, with a simultaneous decrease in levels of both gonadotropins. Our results show that antagonist SB-75 can be safely administered for prolonged periods of time. The rapid shrinkage of the prostate and concomitant improvement in obstructive symptoms of prostatism obtained with antagonistic analog SB-75 in patients with BPH may decrease the morbidity of prostatic surgery and offer a therapeutic alternative in men who are considered poor surgical risks.(ABSTRACT TRUNCATED AT 400 WORDS)

[Usefulness of magnetic resonance images in percutaneous angioplasty for aortic coarctation]. / Utilidad de imágenes por resonancia magnética en la angioplastía percutánea de coartación aórtica.

From October 1985 to February 1992, we performed 80 percutaneous transluminal angioplasty procedures (PTA) in 76 patients with Coarctation of the Aorta (CoAo). Twenty eight patients (aged 2.6 to 62 years; mean, 11.4) underwent Magnetic Resonance Imaging (MRI) during the follow-up period, 2 to 60 months (m = 16) after dilation. Three of these patients were also studied before PTA. We found mild residual coarctation in 11, minimal irregularities in the aorta in five and excellent results in twelve cases. No aneurysms were found. In those patients that underwent MRI before the angioplasty was possible to choose the balloon, thus reducing the time during dilatation. In conclusion we believe that MRI is an excellent and well suited alternative for the serial studies in patients with CoAo, before PTA and in the follow-up.