PET-Probe

1. Description

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The passive PET probe is derived from the standard probe "HiSens". The PET-probe is for the detection of higher-energy radiation like for example ¹³¹J (E_Gamma = 365 keV) and for the direct detection of radiation resulting from the positron annihilation of 511 keV.

In order to achieve nearly as good collimation as for the standard probes for 140 keV, the collimator sleeves / tips are dimensioned accordingly. The PET probe is available in two versions: with a probe diameter of 22 mm (side shielding 75% @ 511keV) and 31 mm (side shielding 93% @ 511 keV). Both models have a sensitivity > 5000 counts / s / MBq at a standard dihedral angle of 45°. The collimators are built in stainless steel tubes that can be screwed off and autoclaved separately.

When used intraoperatively the probe has to be protected by a sterile latex coating, as for example used in ultrasound diagnostics.

2. Technical Data

Detector	CsI:Tl-scintillation Ø 6 mm x 8 mm long, read-out by a 20 mm² pin-photodiode
Gamma-energy range	60 keV … > 511 keV
Dimensions	length: 220 mm; lenght of cable: 3 m diameter hand piece: 20 mm diameter tip: 22 mm, weight: about 10 ounce (270 g) diameter tip: 31 mm, weight: about 16 ounce (450 g)
Detection efficiency	35% @ 511 keV
Special features	2 different collimator sleeves available

2.1 Collimation Side-shielding

Material	Tungsten lateral 6,65 mm wall thickness, rear 8 mm wall thickness: side shielding = 75 % @ 511keV (¹⁸F, ⁶⁸Ga, FDG) lateral 11,15 mm wall thickness, rear 8 mm wall thickness: side shielding = 93 % @ 511 keV (¹⁸F; ⁶⁸Ga; FDG)
dihedral angle / FOV	Standard 40° FWHM

2.2 Background sensitivity

Zero effect < 0,1 cps = 6 c/min

2.3 Sensitivity and resolution

The sensitivity of the probe for 511 keV is determined under standard measurement conditions. The figure shows the sensitivity in dependence of the distance from source to probe tip. The PET-probe has a good sensitivity > 5.500 counts/s/MBq.

The angular resolution with a standard collimator (40°) is determined in the near field (distance: 3 cm) and in the far field (distance: 10 cm).

The spatial resolution is determined in the near field (distance: 1 cm). The probe has an excellent spatial resolution < 15 mm.

2.4 Energy spectra

The energy spectra of the PET-probe, recorded for ¹⁸F (511 keV):