Straight Gamma Probe: "HiSens"

1. Description

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The straight probe "HiSens" is our standard probe for the detection of sentinel lymph nodes in the surgical treatment of cancer (sentinel technique, breast cancer, melanoma).

It outstandingly fulfills the requirements of a modern gamma probe. High sensitivity (> 20.000 counts/s/MBq) with an excellent side shielding (> 99.97% @ 140 keV), good spatial and angular resolution (17 mm, 40°) with a probe diameter of 15 mm. The straight probe allows the exact localization of the labelled lymph node already from some distance just by aiming along the axis of the probe.

The probe is optimized for the energy range around 140 keV (99mTc), and can be used for gamma-ray energies between 70 keV (201Tl) and 511 keV (PET).

Additionally there is a set of collimator sleeves with different fields of view (15°, 20°, 40° - (default), 50°, 60°, 90°, 120°) for special applications and different energies (131J - 364 keV and PET (511 keV )) which broadens the area of application of the probe even further. These collimators are built into stainless steel tubes that can be unscrewed and steam sterilized separately.

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


2. Technical Data

Detector CsI:Tl-scintillation crystal Ø 6 mm x 8 mm long, read out by a 20 mm2 pin-photodiode
Gamma-energy range 60 keV … > 511 keV
Probe properties length: 220 mm;
length of cable: 3 m
diameter hand piece: 20 mm
diameter of tip: 15 mm
weight: about 7 ounce (200 g)
Special features 6 different collimator sleeves available

2.1 Collimation and Side-shielding

Material Tungsten, lateral thickness 3,15 mm (at all collimator sleeves with D = 15 mm), rear thickness 5 mm
side shielding = 99,97 % @ 140 keV (99mTc)
Dihedral angle (FOV) Standard 40° FWHM, changeable by 6 different collimator sleeves

2.2 Background sensitivity

Zero effect < 0,3 cps = 18 c/min

2.3 Sensitivity and Resolution

if you can read this, then something went wrong.Sensitivity
if you can read this, then something went wrong.Angular Resolution
if you can read this, then something went wrong.Local Resolution
if you can read this, then something went wrong.Phantom

The sensitivity of the probe depends on the used collimator. The basic sensitivity is determined by the standard collimator (40°). The sensitivity is shown in the figure - its depending on the distance between lymph-node and probe tip. The probe CXS-OP-SZBN has a high sensitivity > 20.000 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 with a standard collimator (40°) is determined in the near field (distance: 1 cm). The probe has an excellent spatial resolution < 17 mm.

Spatial resolution, angular resolution and sensitivity depend strongly on the actual measurement conditions and from the selected collimator geometry. In the table spatial resolution and sensitivity of different collimators were determined in a water phantom.

(distance tip-source: 30 mm) collimator dihedral angle
40° 90° 120°
local resolution in air mm 23 40 46
local resolution in water mm 24 40 47
sensitivity in air Counts/MBq 690 1360 1538
sensitivity in water Counts/MBq 585 1120 1154

2.4 Energy spectra

The energy spectra of the probe CXS-OP-SZBN, recorded with nuclides used most in medicine:

if you can read this, then something went wrong.18F (511 KeV-PET-Nuclide)
if you can read this, then something went wrong.123I (159 KeV)
if you can read this, then something went wrong.99mTc (140 keV)
if you can read this, then something went wrong.111In (171 keV, 245 keV)
if you can read this, then something went wrong.201Tl (70 keV)