| TRADEMARKS - Validity of
Dosimetry Data
The terms Roos® and Markus® are
registered trademarks of PTW-Freiburg and PTW-New York. These chambers
have been manufactured by PTW-Freiburg for many years under the PTW type
numbers 34001 and 23343. Dosimetry data published in scientific papers
and various dosimetry protocols refer to chambers manufactured by
PTW-Freiburg. Published data may not be valid for chambers manufactured
by other companies, even if they are sold as "Roos" or "Markus" type
chambers. Since Roos and Markus type chambers manufactured by
PTW-Freiburg are available via different channels, buyers should
carefully check whether they are purchasing an original Roos® or Markus®
or an imitation for which no dosimetry data are available.
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| Roos® Chamber, 0.35 cm³ | Type 34001 | |
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The Roos electron chamber, developed in cooperation with Dr. Roos,
PTB-Braunschweig (National Laboratory of Germany), is used as a
reference electron chamber. It is recommended by the IAEA for high
precision electron dosimetry in radiation therapy. The chamber has a 4
mm wide guard ring to exclude any perturbation effect even at low
electron energies. The polarity effect is negligible (< 0.5 % at 10
MeV).
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The energy response is only influenced by the stopping power ratios. The
chamber is waterproof for absolute dose and depth dose measurements in a
water phantom. The acrylic entrance window has a thickness of 1 mm. The
nominal useful energy range is from 2 MeV to 45 MeV. A calibration
certificate with a Co-60 calibration factor given in absorbed dose to
water is included. Air density correction is required for each
measurement. A radioactive check device with adapter is available as an
option. The chamber cable length is 1.08 m
See also the note on Validity of Dosimetry Data. |
Features:
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Markus® Chamber, 0.055 cm³ |
Type 23343 | |
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The Markus chamber is the well-known electron chamber with widespread
use throughout the world. Developed by Prof. Markus at Göttingen
University, Germany, it was the first high-performance ionization
chamber for precise dose measurements of high-energy electron beams in
radiation therapy. Its small sensitive volume and its waterproof
construction make this chamber suitable for dose distribution
measurements in a water phantom.
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It also can be used in solid state phantoms. The nominal useful electron
energy range is from 2 MeV to 45 MeV. The membrane material is
polyethylene of 0.03 mm thickness. The guard ring borders the measuring
volume. The Markus chamber comes with a protective acrylic cover of 0.87
mm thickness (1 mm water equivalence) for use in water. A calibration
certificate with a Co-60 calibration factor given in absorbed dose to
water is included. Air density correction is required for each
measurement. A radioactive check device is available as an option. The
chamber cable length is 1.05 m.
See also the note on Validity of Dosimetry Data. |
Features:
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| Advanced Markus® Chamber, 0.02 cm³ | Type 34045 | |
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The Advanced Markus chamber,
developed in cooperation with Prof. Rosenow, Göttingen University,
Germany, is the newest development of an electron chamber, combining
advantages of both Roos and Markus chamber types. Since the outer shape
is identical to the Markus chamber, all existing Markus chamber phantom
plates and adapters can be used with the Advanced Markus chamber.
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The small sensitive volume makes
the chamber ideal for dose distribution measurements in a water phantom,
giving a good spatial resolution. An improved design of the guard ring
reduces the influence of scattered radiation from the housing and makes
it possible to perform absolute electron dosimetry without perturbation
effects. The chamber features a flat energy response within the nominal
useful range from 4 MeV to 45 MeV. The membrane material is polyethylene
of 0.03 mm thickness. The Advanced Markus chamber comes with a
protective acrylic cover of 0.87 mm thickness (1 mm water equivalence)
for use in water. A calibration certificate with a Co-60 calibration
factor given in absorbed dose to water is included. Air density
correction is required for each measurement. A radioactive check device
is available as an option. The chamber cable length is 1.05 m.
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Features (also see
Markus chamber):
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Farmer® Chamber, 0.6 cm³ |
Type 30010, 30011, 30012, 30013 | |
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The 0.6 cm³ PTW Farmer chambers are designed for absolute photon and
electron dosimetry with therapy dosemeters.
Type 30010 is the standard chamber. The wall material is graphite with
a protective acrylic cover, and the electrode is made of Al. The
nominal useful energy range is from 30 keV to 50 MeV.
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Type 30011 with graphite wall and graphite electrode is used for therapy
dosimetry, where a completely graphite-built chamber is required. The
nominal useful energy range is from 140 keV to 50 MeV.
Type 30012 is used for therapy dosimetry, where a chamber with graphite
wall and Al electrode is required. The nominal useful energy range is
from 60 keV to 50 MeV.
Type 30013 is the waterproof standard chamber for absolute photon and
electron dosimetry. The nominal useful energy range is from 30 keV to 50
MeV. This chamber type is of rugged construction, since the wall
material is graphite with a protective acrylic cover and the electrode
is made of aluminum.
The guard rings of all chamber types border the measuring volume. An acrylic build-up cap for in-air measurement in Co-60 beams is included (chambers 30010/11/12), as well as a calibration certificate. |
Features:
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PinPoint® Chambers, 0.015 cm³, 0.03cm³ |
Type 31006, 31009, 31014, 31015, 31016 | |
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The waterproof PinPoint chambers have been specially designed for
relative beam profile measurements in a motorized water phantom for
characterization of LINAC radiation fields where superior spatial
resolution is desired.
The PinPoint chambers are ideally suited for this purpose with their inner diameters of only 2 mm (models 31006/31014) and 2.9 mm (models 31009/31015). |
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The chamber models 31006/31009 are used for the evaluation of
stereotactic and IMRT photon beams, while the chamber models 31014/31015
can also be used for analyses of larger photon and electron fields. The
chamber model 31016 shows a flat angular response, since the measuring
volume is approximately spherical. When calibrated against a PTW Farmer
chamber, the PinPoint chambers can be used for depth dose and absolute
dose measurements. The sensitive volume is vented. The wall material is
graphite with a protective acrylic cover. The chambers are fully guarded
up to the measuring volume. The nominal energy ranges are Co-60 up to 50
MV photons and 6 MeV to 50 MeV electrons. The chambers have a short stem
for mounting and a flexible connection cable. They can be supplied with
different connector types.
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Features:
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Semiflex Chambers 0.125 cm³ and 0.3 cm³ |
Type 31010, 31013 | |
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The semiflex chambers are designed for therapy dosimetry, mainly for
dose distribution measurements in motorized water phantoms. They have
a short stem for mounting and a flexible connection cable. The nominal
useful energy range is from 30 keV to 50 MeV photons.
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The wall material is graphite with a protective acrylic cover. The
guard ring borders the measuring volume. An acrylic build-up cap for
in-air measurement in Co-60 beams is included with each chamber, as
well as a calibration certificate for calibration in absorbed dose to
water or in air kerma. Air density correction is required for each
measurement, and a radioactive check device is available as an option.
Both chambers are shaped cylindrically with an inner diameter of 5.5
mm; they differ only in the length of the measuring volume. The 0.125
cm³ chamber is ideal for 3D dosimetry in a water phantom, since the
measuring volume is approximately spherical resulting in a flat
angular response over an angle of ± 160° and a uniform spatial
resolution along all three axes of a water phantom.
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Features:
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| Sealed Ionization Chambers | Type 23322, 23323 | |
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The flexible 0.1 cm³ chambers are to be used in environments with
varying temperature without the necessity of air density correction.
The sensitive volume is sealed to prevent entry of the surrounding air
according to IEC 60731. Therefore, the chambers are ideal for in-vivo
measurements during gynecological afterloading therapy.
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Chamber type 23322 is used with a catheter for measurements in the
bladder, whereas chamber type 23323 is designed for measurements in the
rectum, using a protective sleeve. The chambers are to be used with a
radioactive check device, which is available as an option. The nominal
useful energy range is from 140 keV to 50 MeV. Calibration is usually
conducted at 280 kV X-rays and Cs-137. Ir-192 calibration, for example
for patient dosimetry during afterloading treatment, can be obtained by
interpolation. The chambers are equipped with a flexible stem. The outer
diameter of the chamber type 23322 is 5.5 mm, and the diameter of
chamber type 23323 is 7 mm. The chambers are supplied with a flexible
cable of 1.5 m length. Different connector types are available. A
calibration certificate is included with each chamber.
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Features:
See also the product section In-Vivo Dosimetry |
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Rigid Stem Chambers 0.3 cm³ and 1 cm³ |
Type 30016, 30015 | |
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The rigid stem chambers are designed as reference chambers for
absolute dosimetry to be used in radiation therapy or by secondary
standard dosimetry laboratories (SSDL). The chambers have been type
tested by PTB-Braunschweig, the German National Laboratory. They have
very small variations of response with radiation quality from low
X-ray energies up to high-energy photon and electron radiation.
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The nominal useful energy range is from 30 keV to 50 MeV. Both chambers
are shaped cylindrically (thimble chambers). The wall material is
graphite with a protective acrylic cover. The electrodes are made of
graphite-coated aluminum. The guard rings border the measuring volume.
Both chambers are constructed with a long stem of approx. 25 cm length
for easy mounting in the radiation beam. An acrylic build-up cap for
in-air measurement in Co-60 beams is included with each chamber, as well
as a calibration certificate for calibration in absorbed dose to water
or in air kerma. Air density correction is required for each
measurement. A radioactive check device is available as an option.
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Features:
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Soft X-Ray Chambers 0.0053 cm³, 0.02 cm³, 0.20 cm³ |
Type 34013, 23342, 23344 | |
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The 0.02 cm³ soft X-ray chamber type 23342 is the standard ionization
chamber for dose measurements in superficial radiation therapy. The
0.20 cm³ chamber type 23344 with its bigger sensitive volume is used
for similar pur-poses, where a higher response is required.
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The usual calibration of both chambers is done at 15 kV to 70 kV. The
chambers have a very flat energy response in the range from 10 kV to
100 kV. The 0.0053 cm³ soft X-ray chamber type 34013 has an extremely
small sensitive volume and makes it possible to measure therapeutic
X-ray beams with very small field sizes or with steep fluence
gradients. The calibration is typically done at 15 to 50 kV. The
energy response within this range is ± 2 %. The membrane material is
polyethylene of 0.03 mm thickness. The guard ring borders the
measuring volume. A calibration certificate is included. Air density
correction is required for each measurement. A radioactive check
device is available as an option.
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Features:
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