In 1978 we were looking for a means to generate
tomographic myocardial perfusion images using Tl-201.
The notion of using depth dependent blurring to
generate tomographic images was advanced by Hal Anger
(1) in 1958 and the concept was later commercialized
by Siemens as the PhoCon Tomographic Whole-Body
Scanner. About the same time another intriguing idea
was advanced by Dr. Gerald Freedman
(2) which utilized
a rotating slanted-hole collimator to create a sequence
of variable angle views. This was commercialized by
Technicare and more recently Lasher et. al.(3). The
SPECT concept, which has gained widespread acceptance,
is based on the “Humongotron” rotational device which
was first described by John Keyes (4).
We rejected these sequential concepts because they lacked simultaneity in the formation of the images needed for tomographic reconstruction and developed the seven-pinhole (7PH) technique for cardiac tomography. Between 1978-82 about 250 of these 7PH systems where installed as “add-ons” for existing large and small-field of view gamma cameras with circular detectors. Because 7PH technology was limited to small organ imaging such as the heart, it was replaced by rotational SPECT tomographic devices with more generalized organ imaging capabilities.
We have continued to develop and utilize the 7PH technology within our “office-based” nuclear cardiology imaging lab and have extended the original 7PH concept using a Pentium based computer to acquire holospectral images of the heart (128 x 128 x 128) with sufficiently good statistical content to permit simultaneous imaging of Tl-201 stress images superimposed with Tc-99m Tetrofosmin resting images. Since 1995 we have performed about 12,000 of these simultaneous dual isotope studies utilizing a 7PH protocol which achieves 95% diagnostic accuracy (5).
More recently there has been a resurgence of interest in pinhole tomography for high resolution imaging of research animals. Most of these devices are adapted to rotational SPECT systems (6,7,8) with the notable exception of the work of Harrison Barrett (9). Our concept differs from that of Barrett in that we utilize several pinholes to form isolated images on larger area detectors. This simplifies reconstruction and lowers system cost.
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