Features
- Checks the constancy of LINAC electron energies in the range of (5 … 25) MeV
- Makes it possible to fulfill the AAPM TG-24 protocol
- Makes it possible to calculate the most probable energy at the surface Ep,O
The GESKE monitor is a helpful device for quality control in radiation therapy. Electron energy checks are recommended at least once a month by the AAPM according to TG-24. The GESKE monitor consists of nine parallel ion chambers and absorbers between the chambers. It connects to a standard dosemeter with 400 V high voltage supply. The collecting electrodes are interconnected and deliver a dose integral, which can be measured by any therapy dosemeter. The signal is proportional to the electron range (Rp, R50, R80). The reference values of the GESKE monitor are derived from water phantom depth dose curves. Frequent energy control as a constancy test can be performed simply by comparing the reference values with the actual measuring values. The most probable energy at the surface Ep 0 can be calculated from the electron range by well-known energy-range relations.
Specifications
| Type of product | ion chamber based energy monitor |
|---|---|
| Application | constancy tests of electron energies |
| Measuring quantity | electron energy |
| Design | group of 9 parallel plate ion chambers in a cylindrical housing |
| Direction of incidence | axial |
| Temperature response | < 0.15 % / K |
| Polarity effect |
± 1.5 % at 6 MeV ±0.2 % at 20 MeV |
| Chamber voltage | 400 V |
| Leakage current | < 1 pA |
| Cable leakage | ≤ 1 pC/(Gy·cm) |
Materials and measures
| Number of plates | 9 |
|---|---|
| Absorber above first plate | 5 mm aluminum |
| Absorber between plates | 5 mm aluminum |
| Absorber below last plate | 7 mm aluminum |
| Outer dimensions |
height 95 mm
cylinder diameter 50 mm base diameter 78 mm |
| Weight | 0.6 kg |
Useful Ranges
| Radiation quality | (5 … 25) MeV electrons |
|---|---|
| Temperature | (10 … 40) °C (50 … 104) °F |
| Humidity |
(10 … 80) %, max 20 g/m3 |
| Air pressure | (700 … 1060) hPa |
Parts
TN3405 GESKE Monitor, connecting system BNT
TW3405 GESKE Monitor, connecting system TNC
TM3405 GESKE Monitor, connecting system M
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