Optimization of an NV-Diamond CW-ODMR Magnetometer for Sentinel Lymph Node Detection
By Angelo, Anderson, Brian, Eshaan
NV diamonds has shown great promise in the field of sensing and navigation due to their high sensitivity to small changes in magnetic fields. Its incorporation into magnetometers is favorable due to its functionality at room temperature and ability to be made into a small size. One crystal structure consists of a vacancy and the replacement of a carbon atom with a nitrogen atom. From these defects, the vacancy holds two electrons and magnetic fields alters the spin states of the pair. By shining a beam of green light into the NV diamond, the intensity of the resulting red beam of light can be measured to determine the magnetic field. This project turns last year's breadboard NV-diamond magnetometer into a soldered, characterized instrument, then tests whether it can locate a magnetic tracer in a lymph-node phantom. It is scoped for about 3 hours of work per week.
When cancer spreads, it usually travels first through lymphatic vessels to the nearest lymph nodes, called sentinel nodes. Surgeons find these nodes by injecting a tracer near the tumor and following where it collects. The standard tracer is radioactive. A magnetic alternative, iron-oxide nanoparticles located with a handheld magnetometer, has been shown non-inferior to the radioactive method in breast cancer. A cheap, sensitive magnetometer therefore has a concrete use. Last year's device recorded dips in its fluorescence spectrum but was too noisy to extract a field value, and its sensitivity was never measured. Phase 1 of this project fixes this. Phase 2 applies the improved device to a phantom.
The project will expand upon quantum sensing by creating a robust model using inexpensive materials. The construction of such a system utilizes quantum principles such as electron spin and the Zeeman effect to conduct high precision measurements of magnetic fields. The magnetometer that we seek to create will become more compact and professional to allow for further variations to the design to occur in the future for other applications. Moreover, the project produces a measured noise budget for a low-cost LED-based NV magnetometer where noise sources dominate, and how far the device sits above its own fundamental limit. It then benchmarks the device on a sentinel-node phantom using the same metrics as clinical probe studies, so results compare directly with commercial probes.
A soldered, enclosed, documented device gives future QLab groups a working platform instead of a breadboard to reverse-engineer. The phantom study tests whether low-cost quantum sensors are a plausible route to radiation-free sentinel node detection. It makes no clinical claims. Magnetometers of this type would have many other uses such as imaging for biomedical practices or surface analysis and GPS-free navigation which could be extrapolated from our base model but is beyond the scope of this project.