Investigation of a pre-operative lymph node imager using an M-HPD

Describes the design of a fast imaging system aimed at providing the accurate location of the centroid of a sentinel lymph node. Through the proposed use of a new 80 mm diameter multi-pixel hybrid photo-diode, equipped with a fibre-optic window, a CsI(Tl) scintillation crystal and a specially optimised collimator, the authors expect to achieve a precision of ±3 mm within 20 s for the location of a lymph node. It has been assumed that the affected gland has a 10 mm diameter and had accumulated 3 μCi of ⁹⁹Tc through drainage of the region of the breast. The paper discusses the likely imaging quality of the larger tube based on measurements made with a smaller prototype detector. The design of two collimators is presented; one to provide a rapid location of the centroid of the SLN and the other to provide the surgeon with a measure of the depth of the potentially infected organ. A method for relating the image information to the patient´s anatomy to guide the surgeon is also presented