IN VIVO ENTRANCE DOSE MEASURMENTS IN

HEAD AND NECK CANCER TREATMENT USING THERMOLUMINESCENT DOSIMETERS



Abobaker El-Toomi, Abir El-Bousefi* and Abdurazk El-Megrab*

Radiotherapy and Nucl. Medicine Dep., National cancer Institute of Sabratha
*Department of Nucl. Eng., Faculty of Engineering, University of Tripoli

E-mail: megrab_am@yahoo.com

تهدف هذه الدراسة الى التحقق من الجرعات الاشعاعية الموصوفة لمرضى سرطان الرأس والرقبة بأحد أقسام الاشعة العلاجية وذلك باستخدام مقاييس الجرع الاشعاعية (TLD) ذات التوهج الحراري. قبل استخدام هذه المقاييس تم اختبارها ومعايرتها حسب الشروط المرجعية (100cGy باستخدام Co-60 وعلى بعد 80 سم وحقل إشعاعي 10x10 سم2) وذلك باستخدام شرائح برسبكس اضافة الى تعيين عوامل التصحيح لها. الدمية ATOM® والتي تحاكي الانسان استخدمت في تعيين توزيع الجرعات الاشعاعية في الرأس والرقبة بعد تشعيع بجرعة قدرها cGy 100. بعدها تم دراسة 35 حقل اشعاعي لعدد 25 حالة مرضية ومقارنة النتائج المتحصل عليها بقيم الجرعات المتوقعة حسابياً حيث وجد أن التفاوت بين الجرعات الاشعاعية المقاسة والمتوقعة أكبر من 5% فقط لثلاث حقول اشعاعية.

ABSTRACT
For performing in vivo entrance dose measurements in external photon beam radiotherapy, characteristics of thermoluminescent dosimeters (LiF: Mg; Ti), known as Harshow TLD-100, studies were carried out. The TLD system (reader and dosimeters) stability and reproducibility were investigated and the calibration of the TLD's was performed. The reference TLD was calibrated under a reference condition (100 cGy with Co-60; SSD 80cm; 10×10 cm2), using 30×30 cm2 Perspex slices. ATOM® female phantom studies for head and neck were performed. A dose of 100 cGy was del

الملخص



ABSTRACT



For performing in vivo entrance dose measurements in external photon beam radiotherapy, characteristics of thermoluminescent dosimeters (LiF: Mg; Ti), known as Harshow TLD-100, studies were carried out. The TLD system (reader and dosimeters) stability and reproducibility were investigated and the calibration of the TLD's was performed. The reference TLD was calibrated under a reference condition (100 cGy with Co-60; SSD 80cm; 10×10 cm2), using 30×30 cm2 Perspex slices. ATOM® female phantom studies for head and neck were performed. A dose of 100 cGy was delivered to the isocenter at the center of one sit of the phantom slices. The dose values “dose distribution” at different points were obtained. Entrance dose for 25 patients with 35 treatments for head and neck cancer were performed. The results were compared with the expected Dose values, only three treatments with discrepancy greater than 5% were observed.