Determination of depth distribution of internal mammary lymph nodes on lateral lymphoscintigraphy

A method using a calibrated ruler for measuring lymph node depth on lateral lymphoscintigrams is described. The accuracy of the method was confirmed with a plexiglass phantom. At the time of internal mammary lymphoscintigraphy, lateral images were obtained in 201 patients. A total of 545 lymph nodes were visualised and categorised into 13 depth intervals. The average lymph node depth was 3.0 +/- 1.1 cm with a range of 1.0-7.1 cm. Average lymph node depth was classified according to body weight with an average depth of 2.5, 3.1 and 3.7 cm for patients weighing less than 60, 60-75 and more than 75 kg, respectively. Lateral lymphoscintigrams demonstrated normal anatomical communication between internal mammary and anterior mediastinal lymph nodes in 3.5% of patients.