Standard Imaging A17 Manual de usuario
A17 Slice Therapy
Ionization Chamber
REF 92675
R
User Manual
STANDARD IMAGING INC.
7601 Murphy Drive
Middleton, WI 53562-2532
TEL 800.261.4446
TEL 608.831.0025
FAX 608.831.2202
Feb / 2005 ©2005 Standard Imaging Inc.
DOC #80444-02
WWW. .COM
A17 Slice Therapy
Ionization Chamber
REF 92675
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Warnings and Cautions alert users to dangerous con-
ditions that can occur if instructions in the manual are
not obeyed. Warnings are conditions that can cause
injury to the operator, while Cautions can cause dam-
age to the equipment.
WARNING:
Electrical shock hazard when connected to 300
V bias supply.
WARNING:
Exradin Ion Chambers are intended for quality
assurance and calibration measurements. They
are not intended to be connected to a patient for
real-time dosimetry measurements.
CAUTION:
Proper use of this device depends on careful
reading of all instructions and labels.
CAUTION:
Do not drop, mishandle, or disassemble unit
since it may result in a change of calibration
factor, or damage to the chamber. Refer all
servicing to qualied individuals.
CAUTION:
Do not sharply bend triax cable. Damage to the
cable may result in high leakage currents.
General Precautions
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PAGE
Table of Contents
General Operation
7601 MURPHY DRIVE
MIDDLETON, WI 53562-2532 USA
WWW.STANDARDIMAGING.COM
4 General Precautions
5 General Operation
7 Parts and Accessories
8 Features and Specications
11 Service Notes
12 Service Policy
13 Customer Responsibility
14 Warranty
Exradin chambers are attached to a 1.5 m length of low-
noise exible triaxial cable that is terminated by a triaxial or
coaxial connector. The collector of the chamber is common
with the center wire of the cable and the center contact of the
connector. The guard is common with the inner cable braid
and the middle connector contact of triaxial connectors, and
the connector body of coaxial connectors. The shell (outer
electrode), usually ground, is common with the outer braid
of the cable and the connector body in the case of triaxial
connectors and the pigtail extending out the rear of coaxial
connectors.
The design of Exradin chambers requires that the collector
and guard operate at essentially the same potential. The
polarizing potential, supplied by an electrometer, is applied
between the shell and the guard. Either polarity may be
applied to the shell and either the shell or guard may be
grounded. Safety and other considerations recommend
grounding the shell, which then requires an electrometer
with a oating input.
All Exradin chambers can support 1000 V between shell and
guard. However, depending on the particular circumstance
and radiation intensity, as little as 90 V may yield essentially
100% charge collection.
Because Exradin ionization chambers do not exhibit volt-
age soakage phenomena, readings of ionization current
may be made immediately after application of the polar-
izing potential. However, it is good practice to pause a
minute or two after changing the potential to allow switch-
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General Operation Continued
ing transients induced in the electrometer to completely
subside. Such transients are most evident in the rate
(current) mode.
The A17 chamber is designed to have an extremely at
response across its active volume. In addition, its water-
proof design and built-in wall thickness for Co60 energies
make it a valuable tool for tomotherapy applications, such
as weekly QA checks or patient dose verication. A 6 MeV
buildup cap is available as an accessory.
Figure 1 shows the at response of the chamber; it is at to
within +1.5% over the central 8.0 cm of its length.
Position on Chamber in mm (center is zero)
Percent of Maximum Value
Distill EndStem End
Figure 1: Flatness of the A17 Slice Therapy Chamber
Operating Instructions
1. With nothing connected to the input jack of the elec-
trometer, turn the power on and wait at least 15 minutes
for warm up.
2. Verify the leakage of the electrometer is within the
manufacturer’s stated acceptable limits.
3. Connect the ionization chamber to the electrometer and
apply desired voltage bias.
4. Allow the electrometer and ionization chamber system at
least 10 minutes to stabilize, making certain that all cabling
is lying at and unkinked.
5. Verify the leakage of the ionization chamber is within the
manufacturer’s stated acceptable limits. If measured in the
presence of background sources, note that this signal will
add to the leakage of the chamber.
6. Some electrometers, such as the Standard Imaging
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Parts and Accessories
REF
72722
72193
Description
A17 6 MeV Buildup Cap, 12.2 mm Delrin
In-Air Comparison Jig (REF 72722 mounts
directly to post of Jig)
General Operation Continued
MAX-4000 Electrometer, allow the user to zero the device
at any time. If desired, perform this system zeroing now.
7. Check the system leakage. Take a reading without ex-
posing the chamber to radiation. This reading should be
less than 0.1% of the nal signal expected. If it is not, the
leakage should be subtracted from the signal.
8. Measure atmospheric temperature and pressure.
9. Position the A17 chamber as desired, and take at least
3 measurements. Generally, the measurements should
not be moving in only one direction (i.e. three readings that
continue to drop and hence may not yet be stabilized). If
a current measurement is done, allow sufcient time for
value to stabilize.
10. Analyze the data taking into account the average
of the readings, system leakage, temperature/pressure
corrections, calibration factors and any other appropriate
corrections to be made. Keep in mind that the calibration
factor consists of the electrometer calibration and the ion-
ization chamber calibration factor.
11. When all measurements are completed, set bias volt-
age to 0 VDC, turn off the electrometer and disconnect the
ionization chamber.
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Collecting Volume:
Collecting Volume Length:
Collector Diameter:
Body Tube Outside Diameter:
Wall Thickness:
Chamber Length:
Body Tube and Guard Mate-
rial:
Response Uniformity over
the central 8.0 cm of chamber
length:
Collector Material:
Electrical Power Require-
ments:
Nominal Collection Efciency:
Maximum Polarizing Potential:
Nominal Inherent Leakage
Currents:
Low-Noise Triaxial Cable:
Connector:
Operating Parameters
Humidity:
Temperature:
Pressure:
Storage Parameters
Humidity:
Temperature:
Pressure:
Product Standards:
1.91 cc
8.0 cm
2.4 mm
12.7 mm
3.3 mm
17.0 cm
Shonka air-equivalent C552
plastic
±1.5%
Carbon Fiber
Operates at +300 VDC
100%
1000 VDC
10-15 A
1.5 m long; 50 ohms; 29 pf/Ft
Triaxial BNC Plug (2-Lug
Male pin) and protective cap
connected by chain (standard);
others available upon request
20 to 80%, non-condensing
10 to 40o C
680 to 770 mm Hg
0 to 95%, non-condensing
-15 to 50o C
600 to 800 mm Hg
IEC 60601-11, IEC 616741
Features and Specications
1 Designed to Meet
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Notes
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Notes
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