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D C Ficke

Publications and source records attributed to D C Ficke.

7 recordsLinked to original sources
PubMed1996

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.

Brain↗
PubMed1982

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.

Animals↗
PubMed1981

Photon time-of-flight-assisted positron emission tomography.

In positron emission tomography (PET), the annihilation radiation is usually detected as a coincidence occurrence that localizes the position of the annihilation event to a straight line joining the detectors. The measure of the difference between the time of flight (TOF) of the annihilation photons between their inception and their detection permits the localization of the position of the annihilation event along the coincidence line. The incorporation of TOF information into the PET reconstruction process improves the signal-to-noise ratio in the image obtained. The utilization of scintillation detectors utilizing cesium fluoride scintillators, fast photomultiplier tubes, and fast timing circuits allows sub-nanosecond coincidence timing resolution needed for the effective use of TOF in PET. Mathematical considerations and pilot experiments show that with state-of-the-art electronic components and through the application of proper reconstruction algorithms, the combination of TOF and PET positional data improves severalfold the signal-to-noise ratio with respect to conventional PET image reconstruction at the cost of increasing the amount of data to be processed. The construction of a TOF-assisted PET device is within the capability of state-of-the-art technology.

Electronics, Medical↗
PubMed1978

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.

Animals↗
PubMedDate not supplied

The super PET 3000-E: a PET scanner designed for high count rate cardiac applications.

OBJECTIVE: Mathematical models for the delineation of regional myocardial perfusion and metabolism with PET require faithful reconstruction of arterial and myocardial time-activity curves following administration of radiotracers. High temporal resolution is often required in such measurements. Many commercially available tomographs exhibit long dead times that limit their count rate capabilities. To overcome these limitations, we developed and tested a whole-body tomographic device (Super PET 3000-E) with high count rate capabilities. The use of cesium fluoride scintillation detectors coupled with a one-to-one detector photomultiplier configuration reduces the system resolving and dead times. MATERIALS AND METHODS: The Super PET 3000-E was subjected to a series of tests with phantoms to determine its resolution, sensitivity, linearity, count rate capabilities, dead time, and random coincidence contribution. RESULTS: The system sensitivity is 136 kcounts/s/microCi/ml and its transverse and longitudinal resolutions are 8.5 and 10.5 mm full width at half-maximum, respectively. The system can easily record a total event rate of 2.0 Mcounts/s with minimal dead time loss and excellent linearity. CONCLUSION: The system fulfills its design goals and allows the very high count rate performance needed for the application of the physiological models used in our cardiac studies.

Algorithms↗