İsmail Faruk DURMUŞ, Emine DİLARA ATALAY

Monte Carlo, Collapse Cone ve Pencil Beam Algoritmalarının Homojen ve İnhomojen Fantomda Açık Alan Ölçümleri

Radyoterapide doz dağılımının doğru hesaplanması için küçük alan ölçümleri ve hesaplama algoritmalarının doğruluğu kritik öneme sahiptir. İnhomojen ortamlarda küçük alan dozimetrisindeki belirsizlikler ve zorluklar daha da artmaktadır. Bu çalışmada inhomojen ve homojen fantomlarda 6MV, 6MV-FFF, 10MV ve 10MV-FFF enerjileri ile 1x1, 2x2, 3x3, 4x4, 5x5cm2 alan boyutlarında CC04 ve CC01 Razor iyon odaları ile ölçümler alındı. Ölçümler ile Monaco tedavi planlama sisteminde Monte Carlo-Dose to Medium (MC-Dm), Monte CarloDose to Water (MC-Dw), Collapse Cone (CC) ve Pencil Beam (PB) algoritmaları ile yapılan hesaplamalar karşılaştırıldı. Homojen fantom su eşdeğeri RW3 katı fantomlardan, inhomojen fantom ise su eşdeğeri RW3 katı fantom ve akciğer eşdeğeri balsa fantom kullanılarak oluşturuldu. CC04 ve CC01 Razor iyon odaları ile hem homojen hem de inhomojen fantomda ölçümler değerlendirildiğinde, MC-Dm, MC-Dw, CC ve PB ile uyumlu sonuçlar elde edildi. Her iki fantomda da en büyük farklar 1x1cm2 alanlarda olduğu görüldü. İnhomojen fantomdaki sonuçlar homojen fantomdaki sonuçlarla karşılaştırıldığında uyum oranının homojen fantomda daha iyi olduğu görüldü. CC01 Razor iyon odası 0.01cm3 hacme sahip ve merkezi elektrodu grafittir. Bu özellikleri ile CC01 Razor iyon odası ile yeterince güvenilir sonuçlar elde edilmiştir. Alan boyutu küçüldükçe ölçümler ve hesaplamalar arasındaki farklar artmaktadır.

Output Measurements of Monte Carlo, Collapse Cone and Pencil Beam Algorithms in Homogeneous and Inhomogeneous Phantom

Accuracy of small field measurements and calculation algorithms is critical for accurate calculation of dose distribution in Radiotherapy. In inhomogeneous and homogeneous phantoms, measurements (1x1, 2x2, 3x3, 4x4, 5x5cm2 field sizes) were made with CC04 and CC01 Razor ion chambers using 6MV, 6MV-FFF, 10MV and 10MV-FFF energies. In the Monaco treatment planning system, dose distribution was calculated by Monte Carlo-Dose to Medium (MC-Dm), Monte Carlo-Dose to Water (MC-Dw), Collapse Cone (CC) and Pencil Beam (PB) algorithms and compared with measurements. The homogeneous phantom water equivalent was generated from RW3 solid phantoms, and the inhomogeneous phantom was created using a water-equivalent RW3 solid phantom and a lung equivalent balsa phantom. When both the homogeneous and inhomogeneous phantom measurements were evaluated with CC04 and CC01Razor ion chambers, results consistent with MC-Dm, MC-Dw, CC and PB were obtained. The greatest differences in both phantoms were obtained in 1x1cm2 fields. When the results in the inhomogeneous phantom were compared with the results in the homogeneous phantom, the compliance ratio was observed to be better in the homogeneous phantom. The CC01 Razor ion chamber has a volume of 0.01cm3 and its central electrode is graphite. With the CC01 Razor ion chamber, reliable results were obtained. As the field size becomes smaller, the differences between measurements and calculations increase.

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