A Comparison of TLD Dosimeter: LiF:Mg,Cu,P and 7-LiF:Mg,Cu,P For measurement of Diagnostics and Therapeutic Radiation Doses

Abstract

في هذه الدراسة تم سرد تفاصيل خصائص كل نوع من الكاشعفات الوميضية المذكورة بالتركيز على تلك الخصائص المهمة بالنسبة للتطبيقات الطبية. أيةضا تم شعرح لنظريةة التألق الحقراريةة وكذلك تفاصيل نظام الكاشعف الوميضي . اختبار الخطية أظهر بأن كل النوعين من الكاشعفات ) GR200A & GR207A ( له رد فعل خطى جيد بمعامل خطية 0.999 و 0.997 على الترتيب. بالنسبة لختبار الفقد فقد أظهر كل من الكاشعفين قراءة ثابتة تقريةبا على مدى ستة أسابيع وذلك بالنسبة لكل من التعرض للجرعات العالية والمنخفضة. الدقة ل GR200A ُروجد ْ يت أفضل ِ م ْ ين ذلك ل GR207A بنسبة خطِ أ مئوية ِ ة 18.2 % للول و 34 % للخي ِ ر. إختبار استجاب ِ ة لطاقا ِ ت الشععا ِ ع نو ِ ع الشععة السيني ِ ة، لوح َحظ بأ ّ ن GR200A لديةه َحر ّ د فعل أكثر استقرارً ا بمستوى تبايةن 0.01 بالمقارنة ب 0.02 GR207A . على أيةة حال كلتا النواع لوحظت بأن لها نفس الستجابة إلى طباقتين مختلفتين لشعا ِ ع جاما. بلورات GR200A لوحظت بهْ يا إختل َحف َحصغيي َحر بطاقا ِ ت الشععة السيني ِ ة بالنحقراف المعياري ِ م ْ ين 0.101 ُرمَحقارنة ب 0.138 لبلورات GR207A . ِ م ْ ين الَحنتاِ ئ ِ ج المتحقصل عليها ُرتسَحتنت ُرج بأ ّ ن هناك حاجة ل ْ يجراء َحب ْ يعض التصحقي ِ ح بخصوص الدق ِ ة والخطي ِ ة عندما َحتستعمل ِ ن مثل هذه المقايةيس في المعالجة الشععاعية التشخيصي ِ ة َحأو تطبيقا ِ ت العلج بالشعع ِ ة. Abstract Thermoluminescent dosimeters ( TLDs ) are used in a variety of medical applications including radiation therapy to verify the radiation doses received by patients, which is given results must be fully trustworthy, so physicians can confidently monitor and determine a patient's treatment . In diagnostic radiology, TLDs can also be used to measure skin dose for patient undergoing different x- ray examinations. The main objective of this Thesis is to compare between two types of TLD, LiF:Mg,Cu,P (GR200A), and 7 LiF:Mg,Cu,P (GR207A), with respect to different characteristics that affect their responses to radiations. In this study, the dosimetric properties of two types dosimeters have been stated in details with the emphasis on their characteristics that are particularly relevant to medical dosimetry namely linearity response, fading, accuracy, and energy response. Also, the theoretical bases of the TL phenomenon as well as details of the TLD system have been indicated. Linearity test showed that both TLD types (GR200A & GR207A) have good linearity response with regression of 0.997 and 0.999 respectively. Regarding fading both dosimeters showed very good stable reading over the period of six weeks both for high as well as for low doses. Accuracy of GR200A was found to be better than that for GR207A with percentage error of 18.2% for the former and 34% for the latter. Testing the response of the two dosimeters with respect to different x-ray energies showed that GR200A has a more stable response with variance of 0.010 in comparison with 0.02 for the GR207A. However both types showed the same response to two different gamma ray energies. GR200A crystals showed little variation with x-ray energies with standard deviation of 0.101 comparing with 0.138 for GR207A crystals. From the stated results it is concluded that t here is a need to make some correction regarding accuracy when using such dosimeters in diagnostic radiology or radiotherapy applications.