Approximation and noise errors of measured T/sub 1/ in NMR imaging

Conference · Sun Jan 01 00:00:00 EST 1984 · J. Nucl. Med.; (United States)

OSTI ID:6866898

Persyk, D E

Photomultiplier tubes (PMTs) of various types from four manufacturers were measured to determine their gain drift characteristics. This was in turn related to retuning frequency in Anger cameras. A well stabilized light source illuminated sets of thirty-seven PMTs, simulating ideal steady-state conditions in an Anger camera. Anode outputs were sampled at six minute intervals for periods of up to three weeks using a multichannel data logger. Data were analyzed off line. It was found that PMT gains diverged form their initial values at a rate which decreased with time. The standard deviation of the gain changes, called drift, was plotted versus time. Drift was found to generally obey a power law function: D(%) = 0.16 x t/sup 0.6/ where t is the elapsed time in hours. In testing thousands of PMTs the authors occasionally found ''flyers'' with drift rates considerably larger than the average. The authors conclude that with sets of carefully selected PMTs the frequency of tuning would generally decrease as the tubes age. They also conclude that the presence of an occasional ''flyer'' PMT in a camera would undoubtedly necessitate more frequent tuning, in some cases on a weekly basis. These findings support the observed wide variation in tuning frequency among Anger cameras without active PMT gain compensation.

• Research Organization: Siemens Gammasonics, Inc., Des Plaines, IL
• OSTI ID: 6866898
• Report Number(s): CONF-840619-
• Journal Information: J. Nucl. Med.; (United States), Vol. 25:5; Conference: 31. annual meeting of the Society of Nuclear Medicine, Los Angeles, CA, USA, 5 Jun 1984
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
NUCLEAR MAGNETIC RESONANCE
IMAGE PROCESSING
NOISE
PHOTOMULTIPLIERS
ANODES
CAMERAS
COMPARATIVE EVALUATIONS
ERRORS
FREQUENCY DEPENDENCE
GAIN
LIGHT SOURCES
MULTI-CHANNEL ANALYZERS
TIME DEPENDENCE
TUNING
AMPLIFICATION
ELECTRODES
ELECTRONIC EQUIPMENT
EQUIPMENT
MAGNETIC RESONANCE
PHOTOTUBES
PROCESSING
PULSE ANALYZERS
RADIATION SOURCES
RESONANCE
550602* - Medicine- External Radiation in Diagnostics- (1980-)