CAPINTEC, INC. CAPTUS
®
600
Detector
Your CAPTUS
®
600 system is equipped with a Probe (and possibly a Well), which consists of
a NaI (Tl) (thallium-activated sodium iodide) crystal and photomultiplier tube detector
assemblies. When a gamma or x-ray from a radioactive source reaches the NaI crystal, it
collides with the electrons in the crystal matrix and transfers energy. The excited electron
releases this energy as visible light in direct proportion to its absorbed energy. For this
reason, NaI detectors are classified as scintillation detectors. These sequential emissions of
light for each incident ray generated from the collisions appear to the measuring system as a
single light pulse. The intensity of the pulse is directly proportional to the energy of the
incident gamma or x-ray.
The light is eventually directed toward the photomultiplier tube. The photomultiplier tube,
which is optically connected to the sodium iodide crystal, converts the visible light pulses into
electrical energy and amplifies the signal through a series of dynodes. The resultant
electrical signal is directly proportional to the intensity of the incident light pulse. Therefore,
the pulse height generated by the system is directly proportional to the energy of the incident
gamma or x-ray detected by the system.
Multichannel Analyzer
A multichannel analyzer (MCA) records the number and height of the electrical pulses
generated by the system, divides the pulses into groups based upon pulse height, and
provides a visible picture or spectrum of the pulses as well as count information. The
CAPTUS
®
600 divides the pulses into 4 energy bands (200, 400, 800 and 1600 keV)
consisting of 256 channels each. Since pulse height is directly related to the energy of the
incident photon, the spectrum displays the pulse heights as a graph of pulses or counts on
the vertical scale and energy on the horizontal scale. By matching the displayed spectrum to
the decay scheme of an isotope, positive identification of the radioactive source can be
achieved.
TECHNICAL SPECIFICATIONS
Thyroid Uptake Stand
Rugged floor stand with heavy duty locking casters and an articulating arm for the positioning
of detector/collimator. Individual shelves provided for the CAPTUS
®
600 readout unit and the
printer. Mounting for the isolation transformer and the optional well detector is provided on
the base of the floor stand.
Dimensions: Height 175.3 cm (69")
Width 71.1 cm (28")
Depth 78.7 cm (31")
Weight 181.8 kg (400 lb.)
(with optional well) 213.6 kg (470 lb.)
2-2 FUNCTIONAL & TECHNICAL DESCRIPTION November 07
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