BASICSCIENCES PHYSICS Dosimetryin Lymphoscintigraphy of Tc-99m AntimonySulfideColloid Lennart Bergqvist, Sven-Erik Strand, Bertil Persson, Larsolof HafstrOm, and Per-Ebbe JOnsson University of Lund, Lund, Sweden A quantitativekinetic technique usinga scintillationcamera has been devel o_ for Investigatinglymph drainage and the uptake in the lymph nodes of 9―1cSb@S3 colloid injected subcutaneously.Twenty-twopatientswith primary malignantmelanomawere examined.Lymph-nodedissectionwas performedand 185 lymphnodeswere Individuallymeasuredfor radioactivity.The kineticsof col bid uptake in individualnodes can be expressedby a simple two-compartment model. The outflow of colioid from the injection sfte was found to be monoexponen tiai, and the tissue volumecontainingthe injected colloid at the injectionsite in creased asymptotically with time. A model has been developed for calculating ab sorbeddosesat the injectionsite and in organswfth colloiduptake. The following absorbed doses were estimated (j@Gy/MBq):whole body 0.7-4.5, gonads 0-22, liver 1.0—3.9, lymphnodesupto 1000 andinjectionsite about10,000. PossIblebio logical effects in the skin and effective dose equivalentshave been estimated whenusingotherlymphoscintigraphicagents. J NucI Med 23: 698—705, 1982 There is considerable need for a method of examin ing the lymphatic drainage and lymph nodes in the di agnosis and treatment of malignant diseases. Although radiographic lymphography with contrast media is a clinically accepted method for investigating the lym phatic system (1), it is not always applicable because the contrast must be injected into a suitable lymph vessel. Moreover some clinical contraindications limit its use (2,3). An attractive alternative method is lymphoscintig raphy, which is safe and simple and has a number of technical advantages (4—6). Several lymphoscintigraphic studies have been made both in animals and in humans using a Au-I 98 colloid or various Tc-99m-labeled col bids (5—7). The disadvantages of using a Au-198 colloid, despite its favorable particle size, are that the photon energy is rather high for scintillation-camera measure ments and the high absorbed dose at the injection site, which may cause local tissue necrosis (4). In a previous experimental study, it was shown that Tc-99m-antimony sulphide colloid (TcSbSC) has a Received July 10, 1981; revision accepted Mar. 3, 1982. For reprints contact: Sven-Erik Strand, Ph.D., Dept. of Radiation Physics, University of Lund, S-22l 85 Lund, Sweden. particle size (3—30 nm) comparable with that of Au-198 colloid (5 nm), particles small enough to pass from the interstitial fluid into the lymphatic vessels (8). These observations were applied to clinical practice by developing a quantitative scintillation-camera tech nique for the investigation of lymph drainage and the uptake of TcSbSC in the lymph nodes of patients with malignant melanoma (9). The aim of the present investigation was to calculate, from the measured distribution of activity in patients, the absorbed doses in injection sites, individual lymph nodes, gonads, liver, and the whole body. In addition, dosimetric comparisons between different radiolabeled colloids and antibodies used in lymphoscintigraphy are given. MATERIAL AND METHODS Half a ml of TCSbSC with an activity of about I mCi (@-‘40 MBq), was drawn into a syringe without addition of hyaluronidase or eqivalent. drugs and injected sub cutaneously. The preparations were tested for free per technetate with a gel-chromatography column-scanning technique (8). The labeling yield was regularly better than 95%. .698 THE JOURNAL OF NUCLEAR MEDICINE by on August 3, 2015. For personal use only. jnm.snmjournals.org Downloaded from