Abstract
PurposeIodine-125 (125I) seeds can be used as landmarks to locate non-palpable breast lesions instead of implanting metal wires. This relatively new technique requires a nuclear probe usually used for technetium-99m (99mTc) sentinel node detection. This study aimed to compare the performances of different probes and valid the feasibility of this technique, especially in the case of simultaneous 125I-seed and 99mTc breast cancer surgery.MethodsThree probes with different features (SOE-3211, SOE-3214 and GammaSUP-II) were characterised according to the NEMA NU3-2004 standards for a 99mTc source and a 125I-seed. Several tests such as sensitivity, linearity or spatial resolution allowed an objective comparison of their performances. NEMA testing was extended to work on signals discrimination in case of simultaneous detection of two different sources (innovative figure of merit “Shift Index”) and to assess the 99mTc scatter fraction, a useful parameter for the improvement of the probes in terms of detector materials and electronic system.ResultsAlthough the GammaSUP-II probe saturated at a lower activity (1.6 MBq at 10 mm depth), it allowed better sensitivity and spatial resolution at the different NEMA tests performed with the 99mTc source (7865 cps/MBq and 15 mm FWHM at 10 mm depth). With the 125I-seed, the GammaSUP-II was the most sensitive probe (3106 cps/MBq at 10 mm depth) and the SOE-3211 probe had the best spatial resolution (FWHM 20 mm at 10 mm depth). The SOE-3214 probe was more efficient on discriminating 125I from 99mTc in case of simultaneous detection. The SOE probes were more efficient concerning 99mTc scatter fraction assessments. The SOE-3211 probe, with overall polyvalent performances, seemed to be an interesting trade-off for detection of both 125I and 99mTc.ConclusionThe three probes showed heterogeneous performances but were all suitable for simultaneous 99mTc sentinel node and 125I-seed detection. This study provides an objective and innovative methodology to compare probes performances and then choose the best trade-off regarding their expected use.
Highlights
For the excision of non-palpable breast lesions, the surgeon needs a landmark previously placed under radiological or ultrasound imaging control
NEMA testing Sensitivity (Table 3) Sensitivity results are presented with their standard deviations but assuming a 0.5 mm spatial error positioning, a 15% error has to be added in quadrature [11]
The GammaSUP-II probe was more sensitive than the two other probes in air and scatter medium for both 99mTc and Iodine 125 (125I) sources
Summary
For the excision of non-palpable breast lesions, the surgeon needs a landmark previously placed under radiological or ultrasound imaging control. In France, the gold standard technique remains implanting a metal wire from the lesion to the skin. The Antoine Lacassagne Centre (Nice, France) is the first French hospital authorised to offer an alternative solution with an iodine-125-seed (125I-seed) implanted into the tumour [6]. The literature already tips the scales in favour of the 125I-seed technique [7]. The iodine technique seems to be an answer to these issues with a lower rate of repeated surgery and a lower psychological impact [8, 9]. Specific nuclear probes are needed to detect the seed into the breast
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