RT Journal Article
SR Electronic
T1 Effects of energy window settings of intraoperative gamma probes on breast sentinel lymph node detection
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 2177
OP 2177
VO 54
IS supplement 2
A1 Kindem, Joel
A1 Bai, Chuanyong
A1 Felton, Kellita
A1 Yarnall, Steve
A1 Conwell, Richard
YR 2013
UL http://jnm.snmjournals.org/content/54/supplement_2/2177.abstract
AB 2177 Objectives Intraoperative gamma probes usually use very wide energy windows for sentinel lymph node (SLN) detection. However, wide energy windows reduce scatter rejection and may adversely affect the node detection. In this work, we evaluate the effects of energy window on breast SLN detection for a solid-state detector probe with 8% energy resolution at 140 keV. Methods We simulated energy windows of 16% and 48% centered at 140 keV. A point source with 400 uCi Tc-99m activity was positioned 3.0 cm deep in water to mimic the injection site. Nodes with different uptakes were positioned 3.0 cm deep in water but at different distance from the injection site laterally. The node to background ratio (NBR) was calculated as the sum of the count rate from the node and the scatter count rate from the injection site divided by the latter. Higher NBR was deemed to allow better node detection. A commercial probe with an energy window close to 48% was used to obtain measured data. Results Widening the energy window dramatically increased the scatter from the injection site but only mildly increased the counts from the nodes. The NBR was hence significantly lowered and node detection was decreased. Using the 16% energy window, the count rate from a 0.1% uptake 3.0 cm deep node was 4.8 counts per second (cps). The scatter count rate 5.0 cm from the injection site was 6.2 cps, and the NBR was 1.8. With the 48% window, the count rate from the node increased by 43% to 6.9 cps, but the scatter increased by 711% to 50.3 cps, and the NBR was reduced to 1.1. The same trend was observed for nodes up to 9.0 cm from the injection site. At 9.0 cm, the NBR reduced from 5.0 to 1.7 when using the 48% energy window. The commercial probe showed similar results with measured NBR of 1.1 and 1.3 at 5.0 cm and 9.0 cm away from the injection site, respectively. Conclusions For breast SLN detection, narrower energy window leads to better scatter rejection and node detection. Probes with high energy resolution that enables the use of narrow energy window while maintaining probe sensitivity are preferred.