Users Manual Part 7

Clinical User’s Guide IBA | H-5|
Volume 1 - Treatment Session
Glossary of Terms |
Dee
Dees are located in opposite valleys of the accelerator with counter dees attached to
the magnet sector on each side of each dee. Dees resonate at the 4th harmonic of
the ion orbital frequency. See also: Accelerator, Counter Dee.
Degrader
A device located downstream from quadrupole Q2 used to transform the 230-MeV
fixed energy beam exiting the cyclotron into a beam having an energy level range of
70 MeV–230 MeV. See also: Absorber, First Scatterer, Second Scatterer.
Digital Imaging Device (DID)
A device used to digitally acquire the radiographic images required to verify the
position of each patient. The PPVS interfaces with each DID to ensure proper
movement. A DID is composed of a fluoroscent layer (converting the X-ray light into
a visible light) combined with a CCD (Charge Coupled Device) layer recording the
image.
Digital Signal Processor (DSP)
Refers to various techniques for improving the accuracy and reliability of digital
communications. An intelligent Integrated Circuit (IC) specialized in processing digital
signals. The theory behind DSP is quite complex. Basically though, DSP works by
clarifying, or standardizing, the levels or states of a digital signal. A DSP circuit is able
to differentiate between human-made signals, which are orderly, and noise, which is
inherently chaotic.
Digital Volt Meter (DVM)
A piece of equipment used to measure electrical voltage.
Directly Heated Cathode
A wire, or filament, designed to emit electrons that flow from cathode to plate. This
is done by passing a current through the filament; the current heats the filament to
the point where electrons are emitted.
Direct Current (DC)
A form of electrical current that flows in one direction.
Dose Monitor
A device located inside the nozzle used to monitor the proton beam delivered to each
patient. The system includes two dosimetry pads, located in the two downstream
ionization chambers, and related electronics. A dosimetry pad is a circular (diameter
2cm) parallel plate ionization chamber with a 1cm gap. See also: Ionization Chamber.