Fowler J Charlotte, Solanki Chandra K, Barber Robert W, Swift E Anna, Guenther Ilonka, Ballinger James R, Purushotham Arnie D, Peters A Michael
Department of Nuclear Medicine, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK.
Nucl Med Commun. 2004 Sep;25(9):935-40. doi: 10.1097/00006231-200409000-00011.
99mTc nanocolloid (99mTc-NC) is the most widely used tracer for lymphoscintigraphy, although others have been proposed, including radiolabelled proteins such as human serum albumin and polyclonal human immunoglobulin G (HIG). The extraction fraction of such tracers by individual nodes is clearly important but has not previously been measured in humans.
Patients scheduled for axillary clearance surgery (three groups) received dual-labelled radiotracers 2-4 h before surgery: group 1 (3 patients) received 99mTc-NC (10 MBq) and 111In-HIG (2 MBq) as a mixture (0.2 ml) into the breast parenchyma above the primary tumour; group 2 (3 patients) received 99mTc-HIG (10 MBq) and 111In-HIG (2 MBq) as a mixture (0.2 ml) into the breast parenchyma above the primary tumour; and group 3 (4 patients) received 99mTc-HIG (10 MBq) and 111In-HIG (2 MBq) separately (both 0.2 ml) into the breast parenchyma above the tumour and the intradermal plane at the areola. All resected nodes were counted for Tc and In in a well-type scintillation counter. In group 1, nodes were ranked according to their Tc uptake. In groups 2 and 3, nodes were ranked separately according to their respective Tc and In uptakes. If nodes are arranged in linear order and each node extracts a constant fraction of incoming tracer, then the activity in the nodes would decrease exponentially with an individual nodal extraction fraction, E, equal to 1-e(-k), where k is the rate constant of decrease.
In the first group, 99mTc-NC and 111In-HIG identified the same sentinel and second echelon nodes. The observed decrease in nodal activity was exponential in all groups, at least for the first five nodes. Average values for E, based on the first five nodes were 0.69 (range 0.57-0.89; n=3) for 99mTc-NC and 0.45 (0.15-0.70; n=17) for HIG (irrespective of label) (Wilcoxon rank sum, P=0.02). With respect to HIG, there was no significant difference in E between 99mTc and 111In or between deep and superficial injections in group 3.
Although HIG has an extraction fraction less than 99mTc-NC, the value of E is still high enough to make HIG a useful tracer for lymphoscintigraphy, especially for identifying second echelon nodes in addition to sentinel nodes and for imaging lymphatic vessels as well as lymph nodes.
99mTc纳米胶体（99mTc-NC）是淋巴闪烁显像中使用最广泛的示踪剂，尽管也有人提出使用其他示踪剂，包括放射性标记的蛋白质，如人血清白蛋白和多克隆人免疫球蛋白G（HIG）。单个淋巴结对这些示踪剂的摄取分数显然很重要，但此前尚未在人体中进行测量。
计划进行腋窝清扫手术的患者（三组）在手术前2-4小时接受双标记放射性示踪剂：第一组（3例患者）将99mTc-NC（10MBq）和111In-HIG（2MBq）混合（0.2ml）注入原发肿瘤上方的乳腺实质；第二组（3例患者）将99mTc-HIG（10MBq）和111In-HIG（2MBq）混合（0.2ml）注入原发肿瘤上方的乳腺实质；第三组（4例患者）将99mTc-HIG（10MBq）和111In-HIG（2MBq）分别（均为0.2ml）注入肿瘤上方乳腺实质和乳晕处的皮内平面。所有切除的淋巴结在井型闪烁计数器中进行Tc和In计数。在第一组中，根据淋巴结的Tc摄取量进行排序。在第二组和第三组中，分别根据各自的Tc和In摄取量进行排序。如果淋巴结按线性顺序排列，且每个淋巴结摄取进入示踪剂的恒定分数，那么淋巴结中的活性将呈指数下降，单个淋巴结摄取分数E等于1-e（-k），其中k是下降速率常数。
在第一组中,99mTc-NC和111In-HIG识别出相同的前哨淋巴结和第二梯队淋巴结。在所有组中，观察到的淋巴结活性下降呈指数形式，至少在前五个淋巴结中是这样。基于前五个淋巴结的E平均值，99mTc-NC为0.69（范围0.57-0.89；n=3），HIG（无论标记如何）为0.4（0.15-0.70；n=17）（Wilcoxon秩和检验，P=0.02）。对于HIG，在第三组中，99mTc和111In之间或深部和浅部注射之间的E没有显著差异。
尽管HIG的摄取分数低于99mTc-NC，但E值仍然足够高，使HIG成为淋巴闪烁显像的有用示踪剂，特别是用于识别除前哨淋巴结外的第二梯队淋巴结以及对淋巴管和淋巴结进行成像。
