Cancer Research UK Cambridge Institute Uses ELVA-1’s 197 GHz Voltage Controlled Oscillator for Dynamic Nuclear Polarization (DNP) Imaging
ELVA-1 microwave sources have fundamental advantages over competitors for DNP applications in medicine like cancer and cardiovascular diseases imaging as these microwave sources are not affected by a high magnetic field, and there is also the ability to change the output power without increasing noise.
“A hyperpolarized pyruvate labeled with carbon 13C, has potential usage in the diagnostic imaging of cancer cells. Upon administration, carbon 13C hyperpolarized pyruvate (13C -pyruvate) is taken up by cancer cells and is further metabolized. Upon nuclear magnetic resonance (NMR)-based imaging (MRI), both hyperpolarized 13C-pyruvate as well as its metabolites can be detected and visualized in cancer cells; this may aid in the diagnosis of cancer. Hyperpolarization of 13C-pyruvate, using dynamic nuclear polarization (DNP), enhances NMR signals”. Source: www.cancer.gov
Dynamic nuclear polarization (DNP) technique for 13C-pyruvate requires microwave irradiation source with precise tunable output frequency around 197 GHz, calculated for Cambridge Institute’s Hyperpolariser with 7T magnet. The maximum positive solid state 13C polarization frequency is not known in advance as depends on 13C molecule, the radical and the magnetic field strength. ELVA-1 oscillator has ensured the tuning of the output frequency within 196 to 198 GHz spectrum range with an accuracy of 4 decimal places, which led to successful experiments held in Cancer Research UK Cambridge Institute.
Non-invasive imaging plays a central role in cancer disease for determining diagnosis, prognosis, and optimizing patient management. Common imaging methods like computed tomography (CT), single photon emission computed tomography (SPECT), and positron emission tomography (PET) expose patients to ionizing radiation that’s why could not be recommended for often use.
Magnetic resonance (MR) applies no ionizing radiation and is now considered the gold standard in assessing anatomy, function and mass. Hyperpolarization, using the dynamic nuclear polarization (DNP) technique, can yield greater than 10,000-fold signal increases in MR-active nuclei. When used with MR imaging and/or spectroscopy, hyperpolarized 13C carbon labelled metabolic tracers allow unprecedented real-time visualization of the biochemical pathways. Among cancer treatment, it is also possible that, in the future, hyperpolarized magnetic resonance will play a major role in clinical cardiology.
The DNP process transfers the electronic polarization to the 13C-labelled molecule of interest using microwave irradiation. This is achieved by mixing a source of free electrons (called a radical) with the 13C-labeled sample to be hyperpolarized. The mixed sample is then placed in a high magnetic field and rapidly frozen in liquid helium at temperature to approximately 1 K. Microwave irradiation by 197 GHz frequency is another necessary impact to transfer the polarization from the electrons to the carbon molecules.
Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge has built multi-sample 7 T dynamic nuclear polarization polarizer for preclinical hyperpolarized MR samples. As a source of microwave irradiation, it has ELVA-1 split 197 GHz microwave source which is directly connected to the microwave flange of the polarizer.
The model of microwave source is digitally controlled mm-wave IMPATT generator VCOM-05/197/2/50-DAF-M. It has 60 mW output power with 1 mW power step. As it was described in A multisample 7 T dynamic nuclear polarization polarizer for preclinical hyperpolarized MR article, power modes of 45 mW and 20 mW were used in this research. The maximum positive solid state 13C polarization was achieved at 196.7xxx GHz frequency with 20 mW microwave power.
ELVA-1 197 GHz microwave source is custom-designed device from VCOM-XX series of digitally controlled mm-wave IMPATT oscillators. VCOM-XX high power oscillator series is designed for reliable work at scientific experiments which last for a long time, a few weeks or even months.
Key features of VCOM-05/197/2/50-DAF-M mm-wave source:
- A sufficiently large power level for frequencies of about 200 GHz;
- Possibility of smooth frequency tuning within operating frequency range;
- Microwave source is not affected by a high magnetic field;
- Built-in frequency counter to stabilize the operating frequency, which is important under long-term experimental conditions. The frequency should not go out of resonance for hours;
- Adjustable output power level with low noise level;
- The possibility of frequency modulation of the signal as important feature;
- Remote digital control of the oscillator, which is also convenient for long duration experiments;
- SNMP (Ethernet) control;
- The oscillator has internal diagnostics of key parameters during its operation..
VCOM-05/197/2/50-DAF-M specification:
|
Frequency Range (controlled) |
196.0…198.0 GHz |
|
Output power (typ) *) |
60 mW |
|
Frequency step (typ) |
500 kHz |
|
Power level step (min) |
1 mW |
|
SPECTRUM LINE Width -20dBc |
<500 kHz |
|
Frequency stability |
< 1 MHz over +10…+40°C temperature range |
|
Frequency settling time |
1 sec (max) |
|
Absolute accuracy of set frequency |
+/- 0.5 MHz |
|
Max attenuation (MIN) |
40 dB |
|
FM input Signal |
0…+10V 5kHz max |
|
FM INPUT SENSETIVITY(typ) **) |
13MHz/V |
|
AM input Signal |
0…+10V 5kHz max |
|
generator output flange/waveguide |
WR-4.3/UG-387/U-M |
|
Remote diagnostic protocol |
Ethernet / SNMP v1 |
For more info on Dynamic nuclear polarization polarizer, please contact Cancer Research UK Cambridge Institute, University of Cambridge.
Read how they use 13C hyperpolarized pyruvate in clinical research https://radiology.medschl.cam.ac.uk/research/research-themes/c13-hyperpolariser/
For more specs of VCOM-05/197/2/50-DAF-M 197 GHz microwave source or to order microwave source for 94, 188 or 282 GHz corresponding to 3.35, 6.7 and 10.1T magnets, please contact ELVA-1.