myQA Blue Phantom3 - Detectors

Semiconductor Detectors

IBA Dosimetry GmbH provides five types of semiconductor detectors for field analysis:

• RFD: Reference detector with positive polarity (1)
• EFD: Field detector for electrons (2) 
• PFD: Field detector for photons (3) 
• RAZOR: Field detector for stereotactic beams (4

These field detectors allow field measurements with high spatial resolution due to the small size of the active semiconductor chip. All field detectors are based on the 3G-pSi semiconductor chip. An important benefit of the 3G-pSi chip is the dose rate independence.

Table 4.1. Semiconductor Detectors

Field Detector for Electrons

The EFD detector should be used for measurements in electron fields, where it produces a signal proportional to the absorbed dose in water, without any need for corrections.

Field Detector for Photons

The PFD detector is specially designed for measurements in photon fields. The detector has a built-in compensation for the energy dependence of Si. 

When irradiated in the axial direction the photon field detector gives a uniform resolution. The detector type is recommended for use in photon fields larger than 10 × 10 cm.

Field Detector for Stereotactic Applications

The RAZOR detector is specially designed for measurements in photon fields, for field sizes less than 10 × 10 cm. The spatial resolution of this detector is only 0.6 mm; it is therefore the choice in small fields or sharp gradient regions. The detector can also be used in electron fields if the integration time is increased.

Reference Detector

The RFD detector is specially designed to achieve a stable reference signal in both photon and electron beams. By detecting fluctuations in the beam, the inaccuracy of the relative measurement due to varying accelerator output is reduced.

IMPORTANT NOTICE: REFERENCE DIODE 
There are two types of reference diodes: RFD, 3^G -pSi reference detector (black colored) with normal polarity, TNC, can be used in combination with other detectors and the CCU-X.

Ionization Chambers

Ionization chambers are recommended for absolute dosimetry and used in relative dosimetry for the measurement of profiles and depth doses in photon and electron beams. For continuous scanning, they are usually used in pairs (one field chamber, one reference chamber).

The chambers are connected via chamber extension cables to the CCU-X. The CCU-X provides a bias voltage supply, which is controlled by the myQA Accept software. 

Each chamber is calibrated and delivered with an individual calibration certificate and waterproof without any additional accessory. 

More detailed specific information about the IBA chambers is provided within the dedicated Instructions for Use.

Compact Cylindrical Chambers (CC)

Each chamber is factory calibrated and delivered 

with an individual calibration certificate, and chambers are waterproof without any additional accessory. These chambers' intended applications are:

• RAZOR Chamber: Measurements of small fields and of ranges with high dose gradients (e.g., stereotactic fields) 
• CC04 and CC13: Standard chambers for clinical use in water phantoms, solid phantoms and in air (with build-up cap)

Table 4.2. Compact Chambers

Plane Parallel Chambers (PPC)

The plane parallel ionization chambers are intended for the following applications:

• PPC05: The conventional ionization chamber for electron dosimetry, used in water phantoms, solid phantoms and in air (with build-up cap) 
• PPC40: Fast measurements and easy data evaluation for dose determination in electron and proton beams

Table 4.3. Plane Parallel Chambers

Farmer Type Chambers (FC)

The Farmer type cylindrical ionization chambers are intended for absolute dosimetry in water phantoms, solid phantoms and in air (with build-up cap). Due to the robust wall material, the FC65 P is especially useful for all routine applications.

Table 4.4. Farmer Type Chambers

NACP Chamber

The NACP chamber is a sealed plane-parallel ionization chamber built to the specifications of the Nordic Association of Clinical Physicists (NACP). It is especially suited for measurements in low energy electron beams.

The NACP chamber features a thin front window, which allows shallow measurements, a small cavity minimizing field perturbation, low polarity effect and high stability of detector response.

Table 4.5. NACP chambers

Stealth Chamber

The Stealth Chamber is a large transmission ionization chamber intended to be used as reference chamber in relative dosimetry of photon and electron beams in radiotherapy for clinical use in water phantom scanning systems. It is used for PDD and profiles measurements in small fields. Since the perturbation due to the presence of the chamber in the field is minimal and the chamber can be considered invisible to the beam. It is available in round or square shapes respectively.

IMPORTANT NOTICE: STEALTH CHAMBER AS REFERENCE DETECTOR 
The Stealth Chamber can only be used as reference detector for small fields up to a field size of 20 cm × 20 cm. 
It can be used in combination with any suitable field detector.

Table 4.6. Stealth Chamber Detectors

With a dedicated holder, the Square Stealth Chamber can be mounted on the top of a water phantom. See the Stealth Chamber Instructions for Use for mounting instruction.