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Probes

Beta Probe CXS-OP-ß

Description

Beta probeThe medical Beta-Probe CXS-OP-ß was made for the detection of low energy gamma radiation (12 keV < Egamma < 50 keV) and beta radiation (100 keV < Ebeta < 2 MeV) but can also be used for the application of PET-nuclides. The detection of PET-nuclides is limited by the different Beta+ energies of the used nuclides. Good results are achieved in particular by the use of 68Ga. The probe is not suitable for FDG.

The straight probe has a diameter of 12 mm and can be used intra-operatively (with a sterile cover) as well as preoperatively. The sensitivity is approximately 15,000 counts/s/MBq, the dihedral angle is 45°, the spatial resolution is about 12mm.


Technical Data

Detector 20 mm2 pin-photodiode, entrance window made of Saphire, D = 0.2 mm
Gamma-energy Range 20 keV … 60 keV
Beta-energy range 140 keV ... 2 MeV
Probe Properties Length: 220 mm
Length cable: 3m
Diameter hand piece: 20mm
Diameter of tip: 12mm
Weight: about 6 ounce (170 g)
Special Features No additional collimator sleeves available

Collimation

Material Tungsten, lateral 1.25 mm wall thickness, rear 5mm wall thickness
Dihedral angle (FOV) 45° FWHM

Background Sensitivity

Zero effect < 2 counts/min

Sensitivity

The sensitivity of the probe is determined by a 90Sr-source (EBeta, max. = 546 keV; activity of the point source is about 100 kBq). It’s documented in the supplied measurement protocol and is about 15,000 counts/s/MBq.

Spatial Resolution

The spatial resolution of the beta-probe is 5 mm at a distance of 0 mm between probe tip and the radiation source. It drops to 12 mm at a distance of 10 mm.

Use in PET Studies: Positron Detection **

The Beta-probe can be used conditionally for the localization of positron (beta+) radiation emitters which occur in the use of PET radiopharmaceuticals. The absorption mechanism is very similar to those of normal betas. The achievable spatial resolution and sensitivity allows the use with 68Ga. Because of the low beta+ energy the Beta-probe CXS-OP-ß cannot be used for 18F.

Sensitivity at Beta+-Detection

  1. 68Ga (beta+-energy about 1.9 MeV)
    The maximum sensitivity of the Beta-probe CXS-OP-ß for the beta+-emission of 68Ga (beta+-energy 1.9 MeV max.) is > 20,000 counts/s/MBq (extrapolated to the distance "0" of radiation source and probe tip)

    The figure shows the count rate of the beta+-detection of 68Ga-radiopharmaceuticals. The detection is possible up to a distance of 5 cm in air, which allows for use in surgical operations.
    chart
  2. 18F (beta+-Energy about 634 keV)
    The maximum sensitivity of the Beta-probe CXS-OP-ß for the beta+-emission of 18F (beta+-energy 634 keV max.) is < 300 counts/s/MBq (extrapolated to the distance "0" of radiation source and probe tip) and therefore almost 100 times lower as with 68Ga.

    The figure shows the count rate of the beta+-detection of 18F-radiopharmaceuticals. The detection is possible up to a distance of 1.5cm in air, which complicates the use in surgical operations.
    chart

Local Resolution at Beta+-Detection

  1. 68Ga (beta+-energy about 1,9 MeV)
    The local resolution of the Beta-probe CXS-OP-ß for 68Ga (beta+-energy 1.9 MeV max.)-PET is 8 mm at a distance of 6 mm and drops to 16 mm at a distance of 15 mm. Therefore a good localization of the radiation source in surgical operations is possible.
    chart
  2. 18F (beta+-energy ca. 634 keV)
    The local resolution of the Beta-probe CXS-OP-ß for 18F (beta+-energy 634 keV max.) is 10 mm at a distance of 6 mm and drops to > 40 mm at a distance of 20 mm, so nearly no local resolution is achieved. This properties in connection with the low count rates make a localization of the radiation source in surgical operations impossible.
    chart

** The measurements were performed at the Clinic for Nuclear Medicine, Institut J. Bordet, Bruxelles 1000, Belgium


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