The most recent probes detect intra-operatively either the high-energy annihilation γ rays (with adequate shielding and collimation), or directly the β+ particles (with a beta probe).
Since β+ particles have a very short range of penetration in tissues, beta-probe counting is only possible in direct contact with tissues (not affected by background γ radiation).
The use of either a high-energy gamma probe or a beta probe in radioguided surgery for assessing postresection [18F]FDG-avid residual disease yields in principle similar results.
Considering that the radiopharmaceutical used for mapping sentinel lymph nodes is 99mTc-Nanocoll, the intra-operative probe used must detect lowenergy γ rays as well.