A polymer gel for registration of the thermal profile in microwave ablation prof. Yves De Deene Laboratory for Quantitative and Molecular Nuclear Magnetic Resonance Imaging RADIOTHERAPY MR department

A thermal polymer gel: fabrication Amonium-persulphate (NH 4 ) 2 S 2 O 8 (0.1 % (w/w)) TEMED (0.03 % (w/w)) Gelatine (0.75 % (w/w)) Bovine Serum Albumin (6 % (w/w)) Sodium Chloride (1 % (w/w)) ACTIVE COMPONENTS Acrylamide (7 % (w/w)) N,N’-methylene-bis-acrylamide (0.14 % (w/w)) GELLATION AGENTS CATALYSTS HEATING 53 °C - 55 °C POURING THE GEL 90”

The final touch...

The mechanism Bovine Serum Albumin Denatured serum albumin T Interpenetrating polymer-network T BSA embedded in polyacrylamide network

Acrylamide N,N’-methylene-bis-acrylamide Polyacrylamide + Bovine Serum Albumin + gelatin Denatured proteins T CHEMICAL POLYMERIZATION The mechanism: Why these chemicals ? PHYSICAL REACTION catalysts

Macroscopic effects Interpenetrating polymer-network Change in light scattering Change in local water mobility Change in NMR spin-spin relaxation rate

Magnetic Resonance I.I. Rabi 1938 E. Purcell 1946 F. Bloch 1946 Water H2OH2O B0B0

Magnetic Resonance signal B0B0 I.I. Rabi 1938 E. Purcell 1946 F. Bloch 1946 COIL Signal- processing E. Hahn 1949 COIL

Polymer, protein,... M M t t T2 large T2 short N. Bloembergen R. Pound E. Purcell Magnetic Resonance spin-spin relaxation

R2 = 1 / T2 Quantitative MR measurements S0 HH 

Possible research perspectives Quantitative integrating thermometry using NMR (T2, Magnetization Transfer,...) Change in dielectric properties ? (conductivity, permitivity,...) Tuning the isothermal point ? (pH, gelatin concentration) Change in acoustic properties ? (Ultrasound ?) Other applications (laser treatments, hyperthermia)

CAUTION The gel may contain traces of acrylamide monomers Acrylamide = carcinogenic