Miniature low-cost γ-radiation sensor for localization of radioactively marked lymph nodes.

Merlin Behling,Peter P Pott,Felix Wezel

doi:10.1177/09544119211058918

Abstract

Detection of metastasis spread at an early stage of disease in lymph nodes can be achieved by imaging techniques, such as PET and fluoride-marked tumor cells. Intraoperative detection of small metastasis can be problematic especially in minimally invasive surgical settings. A γ-radiation sensor can be inserted in the situs to facilitate intraoperative localization of the lymph nodes. In the minimally invasive setting, the sensor must fit through the trocar and for robot-aided interventions, a small, capsule-like device is favorable. Size reduction could be achieved by using only a few simple electronic parts packed in a single-use sensor-head also leading to a low-cost device. This paper first describes the selection of an appropriate low-cost diode, which is placed in a sensor head (Ø 12 mm) and characterized in a validation experiment. Finally, the sensor and its performance during a detection experiment with nine subjects is evaluated. The subjects had to locate a 137Cs source (138 kBq activity, 612 keV) below a wooden plate seven times. Time to accomplish this task and error rate were recorded and evaluated. The time needed by the subjects to complete each run was 95 ± 68.1 s for the first trial down to 40 ± 23.9 s for the last. All subjects managed to locate the 137Cs source precisely. Further reduction in size and a sterilizable housing are prerequisites for in vitro tests on explanted human lymph nodes and finally in vivo testing.

Highlights

Metastatic spread is a hallmark of malignant and deadly cancers
Detection of small metastasis at an early stage of disease, that is, in lymph nodes can be achieved by modern imaging techniques, such as positron emission tomography (PET), usually combined with computed tomography (PET/CT) or magnetic resonance imaging (PET/MRI)
For diagnostic PET, tumor cells can be marked with fluoride 18F or other radiopharmacons attached to ligands that are characteristic for tumor cell metabolism, such as fluorodeoxyglucose (FDG), or ligands that bind to tumor cells, that is, prostate specific membrane antigen (PSMA) to detect prostate cancer cells.[2]

Summary

Introduction

Metastatic spread is a hallmark of malignant and deadly cancers. Under certain circumstances, metastasis-directed therapy by, that is, surgical resection or radiotherapy may be life prolonging or even curative in oligometastatic disease, when resection of metastatic lesions can be achieved.[1]. The first stage located directly next to the PIN diode amplifies the current pulse after gamma quant detection to a millivolts-level voltage that can be sent to the stage without too much losses. The pre-clinical applicable system (see Figure 6) consists of a cylindrical stainless steel tube of 12 mm diameter and 25 mm length, which forms the sensor head (see Figure 6), blocks a– and b–radiation, and allows basic hygiene measures This contains the actual sensor diodes and the primary stage amplifier for signal preamplification (see Figure 4(a))

Material and methods

Results

Discussion