calibration of computed tomography system and contrast media volume tailoring for optimal hounsfield units: a theoretical and experimental study

Purpose: the purpose of this study is to test the linearity of the ct system and ascertain the relationship between hounsfield unit (𝐻𝑈) values and weight/weight concentrations of iodine (𝑤𝑖 ) in mixtures. this aims to determine the iodine concentration thresholds for achieving effective contrasts with minimal iodine usage. materials and methods: aqueous solutions of iopaque, with 300mgi/ml of iodine, were prepared for different weight/weight (𝑤𝑖 ) iodine concentrations and filled in a water-pool phantom, and the 𝐻𝑈 observations were taken at different kvps for 10 different ct machines. the variation of 𝐻𝑈 with 𝑤𝑖 was analyzed as, 𝐻𝑈(𝑉; 𝑖) = 𝑏0(𝑉) + 𝑏1(𝑉)𝑤𝑖 . from this, the 𝑤𝑖 necessary for getting a required 𝐻𝑈 value is estimated. results: it is found that hu(v) varies linearly with 𝑤𝑖 for low wi values, although the coefficients 𝑏𝑜(𝑉) and 𝑏1(𝑉) vary widely between machines. for optimal hu enhancement, it was found that a 0.01% weight/weight concentration of iodine is adequate to produce an 𝐻𝑈 value of 450 at 80 kvp, while the corresponding concentration should be 0.025% weight/weight at 120 kvp. conclusion: linear dependence of hu on wi helps to reduce the contrast media volume by estimating the iodine concentration, necessary for obtaining a required hu. it also revealed that lower kvps could yield adequate hu enhancement with a reduced contrast agent, thus potentially minimizing patient exposure to radiation and contrast media.