Comparison of three methods for determining CT dose profile: presenting the tritium method

Abstract

The purpose of the present work was to describe a method of using an imaging plate from a computed radiography system to determine the computed tomography (CT) dose profile (the tritium method) and to compare this method with point-dose measurements using a solid-state detector (CT Dose Profiler; RTI Electronics, Mölndal, Sweden) and the indirect method of comparing the air kerma-length product (P(KL)) at different beam collimations. The three methods were used to determine the full width at half maximum (FWHM) of the dose profile of a multi-slice CT at different nominal beam collimations. For all beam collimations, the obtained deviation between the tritium method and the CT Dose Profiler was smaller than 0.1 mm. The maximum relative error was 2 %. For the P(KL) method, the deviation from the CT Dose Profiler was between 0.2 and 0.4 mm, resulting in a relative error larger than 10 % for the smallest beam collimation even after normalisation to a known FWHM. In conclusion, the proposed method of using an imaging plate to determine the FWHM of the CT dose profile has a high accuracy and shows good agreement with the more advanced method of point-dose measurements using a solid-state detector.

Evaluation of different techniques for CT radiation profile width measurement

“…The 4 to 32 mAs exposure range was used in conjunction with 14 different combinations of S and G in order to locate the saturation point for each set of values and determine most useful S, G, and mAs settings to be utilized in profile width testing. Location of two exposure points below the saturation point is essential in obtaining accurate results when using a two‐exposure technique, (2) as exposing above saturation leads to artificial expansion of the profile width (1) …”

“…CR shows initial promise for application in CT radiation profile measurement due simply to its widespread availability and associated familiarity. Previous works have shown the feasibility to measure CT radiation profile width using the CR system; however, these works have focused largely on Fuji CR systems (1,2) . The vendor‐specific image plate (IP) exposure index and the assignation of pixel value make implementation on non‐Fuji systems difficult, directly affecting the measurement of profile width.…”

Estimation of primary radiation output for wide‐beam computed tomography scanner

“…14 The first exposure (20 mA) was taken for determination of the maximum CR pixel value at the beam center. 14 The first exposure (20 mA) was taken for determination of the maximum CR pixel value at the beam center.…”

“…The two-exposure technique was utilized for the determination of full width at half maximum (FWHM), which represents the beam width. 14 The first exposure (20 mA) was taken for determination of the maximum CR pixel value at the beam center. The second exposure (10 mA) was one-half of the first exposure and was performed for determination of the half-maximum exposure level in the first profile.…”

An investigation into factors affecting the precision of CT radiation dose profile width measurements using radiochromic films

“…The FWHM and FWTM of the radiation dose profile can be measured either directly from a solid-state radiation detector or computed from a digitized screen-film or computed radiography (CR) image. [4][5][6] Most recently, Jackson et al…”