Recent developments in positron scintigraphy

Abstract

The use of positronemitting radionuclides offers unique ■ advantages for radionuclide scintigraphy and also presents unique problems. Positron scintigraphy is of interest for three reasons.First, the detection of the annihilation radiation results in high ■detection efficiency and high spatial resolution. The reason for this is that absorbing collimators are not an intrinsic part of the imaging system. As such collimators provide resolution for gammaray scintigraphy devices primarily by absorbing a large frac ■ .tioh of the gamma rays, it is clear that, in principle, positron scintigraphy efficiencies may be much higher than corresponding gammaray scintigraphy efficiencies (Brownell and Sweet, 1953;Brownell, 1964;Burnham, Aronow and Brownell, 1970).The second factor is the attenuation characteristics of the annihilation radiation. Since for' a given patient thickness the sum of the distance traversed by the two quanta is constant, the attenuation is independent of location of a source positioned between the two detectors.. This may aid in visualizing certain details of a radionuclide distribution and offers the possibility of obtaining absolute activity distributions by the. use of an external standard.

Changes in regional lung mechanics and ventilation distribution after unilateral pulmonary artery occlusion

“…Positron imaging. Dynamic VL r and gas transport were assessed by using a two-dimensional planar positron camera that recorded the radioactive decay events of the short-lived positron emitter 13 NN (t 1/2 5 9.96 min) as a matrix of 64 3 64 pixels (1). The camera's digital electronics were modified to allow collection of multiple-gated sequential images as short as 5 ms each.…”

The contribution of Medical Physics to Nuclear Medicine: looking back - a physicist’s perspective

“…The development of positron emission tomography (PET) followed a similar course with the earliest dual planar systems developed by Gordon Brownell at Mass General [ 30 ], and the first ring systems built in the early 1970s by Robertson, Yamamoto and colleagues at Brookhaven [ 31 ] and Michael Ter-Pogossian in conjunction with Mike Phelps and Ed Hoffman [ 32 ], who went on to install the first commercial system in 1976 and pioneer further early PET systems at UCLA. As with other sectors of Nuclear Medicine, it was the combination of chemistry (synthesis of FDG) and engineering/physics (development of medical cyclotrons and robust PET cameras) that triggered the widespread use of PET, initially as a research system but ultimately as an important clinical tool.…”

Positron emission tomography

“…The potential of positron imaging and the value of eliminating the collimator was recognized by the early developers of nuclear medicine instrumentation, long before the advent of reconstruction algorithms which could allow the generation of transverse sections from data covering a large number of angles. G Brownell and his group developed a family of instruments over several decades that nicely demonstrate the evolution of PET first from dual planar detectors (Brownell et al 1969) working in coincidence and providing longitudinal tomographic images, progressing from there to rotating detectors and using transverse reconstruction algorithms to obtain transverse sections and finally to complete circular stationary detector arrangements, first with a single slice (Burnham et al 1983) and subsequently using an increased number of transverse slices (Burnham et al 1985). Hal Anger also worked on positron imaging almost as soon as he developed the single photon Anger camera (Anger 1966).…”

“…It is also interesting to note that time-of-flight (TOF) imaging was a gleam in the eyes of these early investigators (Brownell et al 1969), leading Brownell to conclude in 1969 that with the then state-of-the-art scintillators and photomultiplier tubes, TOF-which increases in benefit as the object size increases-was useful for elephants, but not yet humans. TOF then went through a period of revival in the 1980s and is only now being revived for a third time, as will be described in more detail below.…”