Characterization of a Linear Fiber-Optic Coupled Dosimeter
M Hoerner*, D Hintenlang, Univ Florida, Gainesville, FLSU-E-I-41 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall
Purpose: This study investigated the dosimetry performance of a linear fiber-optic coupled dosimeter with a sensitive element varying from 3 to 15 cm in length. The dosimeter is comprised of a tissue equivalent plastic scintillating fiber coupled to a photomultiplier tube (PMT). The sensitive element has a length representative of the dimensions of common adult internal organs and measures the absorbed dose along the entire sensitive length. The measurement of absorbed dose in one dimensional space provides a more meaningful measure of the average organ dose compared to current dosimeters which evaluate the dose at a small volume, or point inside the organ.
Method and Materials: A fiber-optic coupled dosimetry system was modified by increasing the linear dimension of the sensitive element to sizes ranging from 3 to 15 cm. A FOC element providing a variable output as a function of exposed dosimeter length, beam energy, depth, and beam intensity, was characterized for various exposure parameters relating to Computed Tomography. A clinical x-ray tube, with half-value layer of 5.60 mm Al at 120 kVp, was used to evaluate the dosimeter response to beam energy, intensity, beam quality, and exposed length. Results: The system consistently demonstrated linearity with tube output and length of the sensitive element and offering excellent sensitivity and reproducibility. The dosimeter also demonstrated a linear response of detected counts to length of scintillation material in the x-ray field over the range of interest. The sensitivity with respect to energy and depth showed a positive linear dependence. An 8% variation in sensitivity across a 12 cm depth was observed within a soft tissue-equivalent medium.
Conclusion: The system allows for rapid and accurate average organ dose measurements relevant to x-ray sources within the diagnostic energy range. The response to previously discussed parameters was independent of the sensitive element length.