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DOSIMETRIC STUDY OF GENIPIN GELATIN-CHEMICAL ADDITIVES POLYMER GEL USING 6 MV AND 10 MV THERAPEUTIC FACILITIES

DOSIMETRIC STUDY OF GENIPIN GELATIN-CHEMICAL ADDITIVES POLYMER GEL USING 6 MV AND 10 MV THERAPEUTIC FACILITIES

ABSTRAK

Gold nanoparticles AuNPs of high-Z materials, inorganic salts and glucose have been used in this study to enhance physical and radiological properties of GP gel dosimeter for different clinical applications. A series of experiments and analysis have been conducted to investigate the effectiveness of these additives on GP gel dosimeter. These additives were investigated for optimum visible absorption dose response, transparency, melting points, density, and water equivalency for 3D dose measurements. A reliable new gel formulation (GP-Gl-AuNPs) was formulated and evaluated for 3D dosimetry using optical evaluation and CT scanning techniques for dose readout.

The addition of glucose (Gl) with optimum concentration of 10% (w/w) was found to improve the thermal stability of the GP gel and increase its melting point (Tm) by 6°C. Furthermore, GI helps to adjust the gel mass density to obtain the desired tissue-equivalent properties. A drop of Tm and the gel strength were observed when salt was used as additives. As the salt concentration increase, gel strength and Tm decreased. The radiological water equivalence of each GP gel dosimeters was determined by evaluating the densities, effective atomic numbers, and the linear attenuation coefficients. All of these values were compared with water and muscle values, proving that the radiological properties of the new gel approximate muscle values and could be considered as a water equivalent gel.

The maximum optical dose responses of GP gel at 6 MV and 10 MV photon beams were –0.00526 and –0.00522 (cm–1Gy–1) respectively. The addition of AuNPs (optimum concentration, 200 ppm) has resulted in a slight increment of the optical dose response in less than 10%. According to the density calibration curve obtained from CT scan, the gel sample densities were extracted using the corresponding CTNs. The result displayed an increment of gel density approximately in the order of 0.5 mg cm–3Gy–1 due to irradiation. The dose resolutions calculations were also indicated that GP–Gl–AuNPs gel enhanced dose resolution.

The percent depth doses (PDDs) and dose profiles of 6 MV photon beams using an ionization chamber (IC), GP–Gl–AuNPs, and EBT3 films of field sizes (100 × 100 mm2) were investigated for comparison and verification purpose. According to the results, the maximum absolute percentage difference between the PDD measurements of GP–Gl–AuNPs with IC and EBT3 films were 4% and 6%. The flatness of the IC, GP–Gl–AuNPs and EBT3 films were 2.2%, 2.1% and 1.8%, respectively, while the symmetry of the IC, GP–Gl–AuNPs and EBT3 films were 0.9 % 1.0% and 0.8 % respectively. This study provides a significant contribution toward the development and successful implementation of gel dosimetry towards clinical radiotherapy.

 

KAJIAN DOSIMETRI GELATIN GENIPIN: BAHAN KIMIA TAMBAHAN- GEL POLIMER MENGGUNAKAN KEMUDAHAN TERAPEUTIK 6MV DAN 10MV

 

ABSTRAK

 

Nanopartikel emas AuNPs dari bahan bernombor atom (Z) tinggi, garam bukan organik dan glukosa telah digunakan dalam kajian ini untuk meningkatkan sifat-sifat fizikal dan radiologi GP dosimeter gel untuk aplikasi klinikal yang berbeza. Satu siri eksperimen dan analisis yang dijalankan untuk mengkaji keberkesanan bahan tambahan pada GP gel dosimeter. Bahan tambah ini telah dikaji untuk respon penyerapan dos yang optimum, ketelusan, takat lebur, ketumpatan, dan kesetaraan air terhadap pengukuran dos secara 3D. Formulasi gel boleh harap yang baharu (GP-Gl-AuNPs) telah diformulasi dan dinilai untuk dosimetri 3D menggunakan penilaian optik dan teknik pengimbasan CT untuk bacaan dos.

 

Penambahan glukosa (Gl) dengan kepekatan optimum 10% (w/w) didapati telah meningkat kestabilan terma gel GP dan meningkatkan takat lebur (Tm) sebanyak 6°C. Tambahan pula, GI membantu melaraskan ketumpatan jisim gel untuk memperoleh sifat-sifat kesetaraan yang dikehendaki. Setitik Tm dan kekuatan gel diperhatikan apabila garam digunakan sebagai bahan tambah. Dengan peningkatan kepekatan garam, kekuatan gel dan Tm menurun. Kesetaraan radiologi air bagi setiap GP gel dosimeter ditentukan dengan menilai ketumpatan, nombor atom berkesan, dan pekali pengecilan linear. Kesemua nilai dibandingkan dengan nilai air dan otot, membuktikan bahawa sifat radiologi gel baharu adalah menghampiri nilai otot dan boleh dianggap sebagai gel setara air.

 

Tindak balas maksimum dos optik gel GP pada foton 6 MV dan 10 MV adalah masing-masing -0.00526 dan -0.00522 (cm-1Gy-1). Penambahan AuNPs (kepekatan optimum, 200 ppm), menghasilkan sedikit peningkatan dos optik kurang daripada 10%. Mengikut keluk kalibrasi ketumpatan yang diperolehi dari pengimbas CT, ketumpatan sampel gel telah diekstrak menggunakan CTNs yang sama. Hasil menunjukan peningkatan ketumpatan gel lebih kurang mengikut urutan 0.5 mg cm–3Gy-1 disebabkan oleh penyinaran. Pengiraan resolusi dos juga menunjukkan bahawa gel GP-Gl-AuNPs meningkatkan resolusi dos.

 

Peratus kedalaman dos (PDDs) dan profil dos alur foton 6-MV menggunakan kebuk pengionan (IC), GP-Gl-AuNPs, dan filem EBT3 untuk saiz bidang (100 × 100) mm2) dikaji untuk perbandingan dan pengesahan. Berdasarkan keputusan, perbezaan peratusan maksimum mutlak antara ukuran PDD GP-Gl-AuNPs dengan IC dan EBT3 filem adalah 4% dan 6%. Kesamarataan IC, GP-Gl-AuNPs dan EBT3 filem masing-masing ialah 2.2%, 2.1% dan 1.8%, manakala simetri IC, GP-Gl-AuNPs dan EBT3 filem masing-masing ialah 0.9% 1.0% dan 0.8. Kajian ini memberi sumbangan yang besar ke arah pembangunan dan kejayaan pelaksanaan dosimetri gel terhadap radioterapi klinikal