Endoscopic diamond magnetometer for cancer surgery

At a Glance

Metadata	Details
Publication Date	2025-07-16
Journal	Physical Review Applied
Authors	NULL AUTHOR_ID, Suzanne Graham, Colin Stephen, Andrew M. Edmonds, Matthew Markham
Institutions	Engineering and Physical Sciences Research Council, Element Six (United Kingdom)
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Endoscopic NV Diamond Magnetometer

6CCVD Reference Analysis: Newman et al., Endoscopic fiber-coupled diamond magnetometer for cancer surgery (arXiv:2504.05884v1)

Executive Summary

This research successfully demonstrates a compact, fiber-coupled Nitrogen-Vacancy (N-V) center diamond magnetometer optimized for endoscopic and laparoscopic surgical applications, specifically Sentinel Lymph Node Biopsy (SLNB).

Core Achievement: Detection of superparamagnetic iron oxide nanoparticles (MagTrace™) used as magnetic tracers in breast cancer surgery.
Material Foundation: Utilizes a 0.5 mm³ low-strain, high-purity, 99.995%-¹²C CVD-grown Single Crystal Diamond (SCD) for optimal N-V ensemble performance.
Miniaturization: The sensor head achieves a maximum diameter of 10 mm, making it suitable for insertion via standard surgical trocars (typically 12 mm).
High Sensitivity: Achieved an unshielded sensitivity of 12.3 ± 4.1 nT/√Hz between 0.5 and 10 Hz.
Detection Limits: Demonstrated detection of iron mass as low as 0.56 mg (100 times less than the recommended dose) and concentrations down to 2.8 mg/ml.
Working Distance: Maximum detection range reached 14.6 mm at the highest tested concentration (100%).

Technical Specifications

The following hard data points were extracted from the experimental results, highlighting the performance metrics of the diamond magnetometer system.

Parameter	Value	Unit	Context
Diamond Material	0.5 mm cube	SCD	Low-strain, 99.995%-¹²C CVD-grown
Sensor Head Diameter (Max)	10	mm	Optimized for endoscopic/laparoscopic use
Unshielded Sensitivity	12.3 ± 4.1	nT/√Hz	Measured between 0.5 and 10 Hz
Minimum Concentration Detected	2.8	mg/ml	Iron oxide suspension (MagTrace™)
Minimum Iron Mass Detected	0.56	mg	Equivalent to 20 µl of 10% concentration
Maximum Working Distance (100% conc.)	14.6 ± 2.2	mm	Highest tested concentration (28 mg/ml)
Working Distance (Lowest conc.)	5.8 ± 4.23	mm	Distance for 10% concentration (2.8 mg/ml)
Laser Excitation Wavelength	532	nm	Used for N-V center excitation
Microwave Power	10	dBm	Used for ODMR measurements

Key Methodologies

The following steps outline the critical components and assembly techniques used to create the fiber-coupled N-V diamond magnetometer probe:

Optical Excitation: A 532 nm GEM laser (250 mW input) was used for N-V excitation, coupled into a Thorlabs FG910UEC fiber (1.5 m long, 910 µm core).
Diamond Coupling: The 0.5 mm³ SCD diamond was directly coupled and secured using glue (Loctite 401) to the polished, bare end of the optical fiber.
Microwave (MW) Delivery: A 0.4 mm diameter copper wire was wrapped once around the diamond to form the MW loop. This loop was soldered to a coaxial cable connected to the microwave source (Agilent N5172B).
Bias Field Generation: A single N42 neodymium-iron-boron magnet (2.5 x 7 x 2.5 mm) was attached to the side of the fiber end to provide a static bias field, aligned close to the [100] crystallographic axis.
Thermal Management: Thermal paste was applied to the fiber tip, diamond, and coaxial cable to aid heat transfer and prevent glue failure.
Signal Readout: Photoluminescence (PL) was collected back through the same fiber, separated by a dichroic mirror, and measured using a balanced detector (Thorlabs PD450A) coupled to a lock-in amplifier (Zurich MFLI).
Probe Encapsulation: The entire assembly was covered with a rubber heatshrink cap to protect the components and ensure light-tight operation, resulting in the final 10 mm diameter probe head.

6CCVD Solutions & Capabilities

This research highlights the critical role of high-quality, customized CVD diamond in developing next-generation biomedical sensing tools. 6CCVD is uniquely positioned to supply the materials and engineering services required to replicate, optimize, and scale this technology.

Applicable Materials for NV Magnetometry

The performance of the N-V magnetometer is directly dependent on the purity and strain characteristics of the diamond material.

Material Requirement	6CCVD Solution	Technical Advantage
High-Purity SCD	Optical Grade Single Crystal Diamond (SCD)	Guaranteed low-strain material essential for maximizing N-V center coherence time (T₂) and achieving high magnetic sensitivity.
Isotopic Enrichment	Custom ¹²C Enrichment	We offer SCD with high ¹²C enrichment (e.g., 99.995% or higher) to minimize decoherence caused by residual ¹³C nuclear spins, crucial for high-performance quantum sensing.
Alternative Sensing Modes	Boron-Doped Diamond (BDD)	For electrochemical sensing or integrated heating elements (if required for future designs), 6CCVD supplies highly conductive BDD films.

Customization Potential & Engineering Services

The success of the endoscopic probe relies on precise material dimensions and robust integration. 6CCVD offers full customization to meet these stringent requirements:

Custom Dimensions and Shapes: The paper utilized a 0.5 mm cube. 6CCVD provides precision laser cutting and dicing services to deliver SCD plates and wafers in custom dimensions, including cubes, micro-disks, or plates up to 500 µm thick, ensuring optimal fit for miniaturized probes.
Ultra-Smooth Polishing: The fiber coupling requires extremely low surface roughness to minimize optical losses. 6CCVD guarantees SCD polishing to Ra < 1 nm, significantly improving photoluminescence (PL) collection efficiency and signal-to-noise ratio (SNR).
Integrated Metalization: While the paper used glued copper wire for the MW loop, 6CCVD offers robust, integrated metalization solutions. We can deposit thin films (Au, Pt, Ti, Cu, W) directly onto the diamond surface to create highly reliable, integrated microwave transmission lines or electrodes, eliminating the need for external wiring and glue.
Large-Scale Production: For scaling up clinical trials or manufacturing, 6CCVD can supply large-area Polycrystalline Diamond (PCD) or SCD wafers up to 125 mm in diameter, ensuring a consistent supply chain.

Engineering Support

6CCVD’s in-house PhD team specializes in CVD diamond growth and material science for quantum and biomedical applications. We can assist researchers and engineers with material selection, crystallographic orientation, and surface preparation protocols for similar NV Magnetometry and Biomedical Sensing projects.

Call to Action: For custom specifications, integrated metalization requirements, or material consultation for your next-generation quantum sensor, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).

View Original Abstract

Intraoperative measurements using magnetic sensors are a valuable technique in cancer surgery for finding magnetic tracers. Here we present a fiber-coupled nitrogen-vacancy center magnetometer capable of detecting iron oxide suspension (MagTrace™ from Endomagnetics Ltd.) used in breast cancer surgeries. Detection of an iron mass as low as 0.56 mg has been demonstrated, 100 times less than that of a recommended dose at a maximum distance of 5.8 mm. Detection of an iron concentration as low as 2.8 mg/ml has also been demonstrated, 20 times less than a recommended dose. The maximum working distance from the sensor can be as large as 14.6 mm for higher concentrations. The sensor head has a maximum diameter of 10 mm which would allow it to be used for endoscopy, laparoscopy, and intraoperative surgery.

Tech Support

Original Source

DOI: https://doi.org/10.1103/znt3-988w