Browse Prior Art Database

Fast Any Two-Out-Of-N Input Timer

IP.com Disclosure Number: IPCOM000037326D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Hrinya, SJ: AUTHOR [+2]

Abstract

Described is a device which rapidly measures the difference in arrival time between pulses at any two of several inputs. One application of this technique is to determine the position of the emitter in Positron Emission Tomography (PET). (Image Omitted)

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Fast Any Two-Out-Of-N Input Timer

Described is a device which rapidly measures the difference in arrival time between pulses at any two of several inputs. One application of this technique is to determine the position of the emitter in Positron Emission Tomography (PET).

(Image Omitted)

The PET scanner (Fig. 1) consists of a ring of N (Z256) detectors encircling the object to be scanned. A pair of coincident pulses indicates that an emitter lies along the line connecting the two detectors. The PET geometry ensures that the two pulses will arrive in different quadrants (spaced at least N/4 detectors apart).

The N inputs are used to trigger N/M (where M = 2, 4, 8) gated oscillators GO. The two detector pulses are latched into M+1 input event latches EL, which enable two different gated oscillators. The relative phase between the oscillators depends upon the difference in arrival times of the input pulses. The gated oscillator outputs from each quadrant are combined by a power combiner PC, and amplified. The signals are split by power splitters PS to feed six phase detectors PD. The power splitters/combiners and amplifiers provide RF isolation needed to prevent "pulling" of the gated oscillator outputs into phase lock.

One of the six phase detectors will have two active inputs from the gated oscillators and will produce a DC output proportional to their phase difference. This output is digitized by a fast analog- to-digital converter (ADC) to produce the desired time difference. The ADC result is stored, and the gated oscillators are reset to await the next event. This entire process can have a resolution of...