Satisfaction with college by traditional and nontraditional college students.

University students (N=433) were surveyed about their satisfaction with a number of campus services and opportunities. Comparisons between traditional (up to 24 years old) and nontraditional (25 years old and older) students indicated the latter valued learning and school opportunities more and appreciated the efforts of their professors in interacting with them and communicating information. A number of similarities were noted. University administrations need to be aware of the important differences between such groups to be able to enhance students' satisfaction.

A spheroid positron emission tomograph for brain imaging: a feasibility study.

UNLABELLED: It has been long recognized that the primary advantage of imaging the brain with a positron emission tomography using GSO scintillation detectors placed on a spheroid surface is the large solid angle of acceptance for annihilation radiation, which results in improved system sensitivity and image signal-to-noise ratio. In the present study, we investigated spheroid system geometry, detector design and contribution of scattered coincidences. METHODS: Scintillation detector distribution on a spheroidal surface was investigated by approximating the surface by polygons. Finding a suitable crystal for this purpose led to the development of an experimental GSO block-type detector. The fraction of scattered coincidences was experimentally evaluated using phantoms and detector pairs in conjunction with a testing platform, and the relationship between scattered fraction and phantom volume was obtained. RESULTS: Spheroid geometry was best implemented with a polyhedron consisting of a series of consecutive rings formed by trapezoids. An experimental block-type detector with 36 GSO scintillators and four 14-mm-diameter photomultiplier tubes, together with custom electronics, yielded a spatial resolution of 3.4 mm FWHM and an energy resolution of 18% FWHM. Using nearly "ideal" scintillation detectors with a 350-keV threshold, we found the scatter fraction to be 0.32 for a 20-cm uniform phantom, 0.22 for a 15-cm phantom and closely proportional to the square root of the phantom volume. CONCLUSION: For cerebral studies, a spheroid PET using GSO scintillators has several advantages: optimized geometry for sensitivity, a dead-time fivefold smaller than an equivalent BGO system, and appreciably better light output for improved energy resolution and detector identification. The construction of such a system is within the capabilities of present technology.

A simple 18O water target for 18F production.

A simple low-volume (3 mL) target has been constructed for the production of 18F via the proton irradiation of 18O enriched water. The target is constructed of copper with the water cavity electroplated with nickel. This target routinely produces more than a curie of 18F (as [18F]fluoride) suitable for radiopharmaceutical syntheses.

PETT VI: a positron emission tomograph utilizing cesium fluoride scintillation detectors.

We designed and built a positron emission transverse tomograph (PETT VI), designed specifically for fast dynamic studies in the human brain, and for cardiac studies in experimental animals. The scintillation detectors incorporated into this device are fitted with cesium fluoride crystals. Cesium fluoride was selected for this purpose because its short fluorescence decay allows the use of a short coincidence resolving time with a concomitant reduction of unwanted random coincidences. PETT VI utilizes four rings of 72 detectors simultaneously yielding seven tomographic sections. The system can be operated in either a low or high resolution mode with intrinsic geometrical resolutions in the plane of section of 7.1 to 11.7 mm full width at half maximum (FWHM), for a slice thickness with a resolution at the center of 13.9 mm FWHM. The maximum sensitivity of the system for seven slices in the low resolution mode is 322,000 cps/microCi/cc in a 20 cm diameter phantom. The contribution of random coincidences before subtraction in PETT VI was found to be approximately 14% of the counts in the phantom image with a source of approximately 3.5 mCi of a positron emitting radionuclide dispersed in a 20 cm diameter tissue equivalent phantom with a concentration of 1 microCi/cc. The short coincidence resolving time of the system permits rapid data acquisition for attenuation corrections and clinical dynamic studies with data acquisition times of less than a minute.

Super PETT I: A Positron Emission Tomograph Utilizing Photon Time-of-Flight Information.

The physical characteristics and some imaging capabilities of Super PETT I, a positron emission tomograph utilizing time-of-flight (TOF) in its image reconstruction process were assessed experimentally by means of measurements carried out in phantoms and clinical imaging studies. The performance characteristics assessed included sensitivity, spatial resolution, image improvements resulting from time-of-flight information utilization, system dead time, and linearity. The clinical examples included imaging of the brain, the heart, the liver, and a demonstration of Super PETT I's capability of achieving cardiac gating.

Design considerations for a positron emission transverse tomograph (PETT V) for imaging of the brain.

Imaging of the brain by positron emission tomography can be optimized for sensitivity by dedicating the design of the tomograph to this application. We have designed a multislice positron emission tomograph (PETT V) for imaging the human brain and the whole body of small experimental animals. The detector system of PETT V consists of a circular array of 48 NaI(Tl) scintillation detectors, each fitted with two photomultiplier tubes, with one dimensional positioning capability. Suitable sampling is achieved by rotation of the circular array of detectors and by a wobbling motion of the detector circle. The proposed system is capable of providing seven slices simultaneously, with a spatial resolution in the plane of the slice from 7 to 15 mm and with slice thicknesses of 7 and 14 mm. The minimum scanning time is 1 sec. The estimated overall sensitivity of PETT V is 350,000 counts/sec/mCi in a 20 cm diameter phantom for a resolution of approximately 1.5 x 1.5 cm. The system is under construction.