To turn the advantage of energy measurement in x-ray transmission diagnosis into practice, we propose a novel detector for the estimation of x-ray energy distribution. This detector consists of several segment detectors arrayed in the direction of x-ray incidence. Each segment detector measures x-rays as current. With unfolding measured currents, the x-ray energy distribution is obtained. The practical application of this detector was verified by estimating the iodine thickness in an acryl phantom.

For ion beam radiation therapy, the measurement of effective atomic numbers is necessary to know the material distribution in a human body: the range of ion beams entering the human body is influenced by the material distribution along their paths. Effective atomic numbers, however, cannot be measured at hospitals because monochromatic X-rays with different energies are necessary and are used only at synchrotron facilities. To make the effective atomic number measurements at hand, we propose energy-resolved computed tomography (CT) using a "transXend detector". By assigning two narrow energy ranges in the unfolding process of the data obtained by the transXend detector, the effective atomic numbers for acrylic and aluminum can be estimated by energy-resolved CT. The estimated effective atomic numbers are compared with those obtained by dual-energy and monochromatic X-ray CT.

To turn the advantage of energy measurement in x-ray transmission diagnosis into practice, we propose a novel detector for the estimation of x-ray energy distribution. This detector consists of several segment detectors arrayed in the direction of x-ray incidence. Each segment detector measures x-rays as current. With unfolding measured currents, the x-ray energy distribution is obtained. The practical application of this detector was verified by estimating the iodine thickness in an acryl phantom.

The advantages of energy measurement of x-rays over current measurement in transmission radiography and computed tomography (CT) for detecting iodine contrast media are discussed. Simulation studies on both methods of measurement are carried out, followed by experiments. As data for energy measurement of x-rays, the event ratio of two energy regions with a K-edge of iodine between them is employed. The energy measurement method is immune to beam hardening, while current measurement suffers greatly with changes in x-ray tube voltage and thickness of the body under measurement. This method is useful in interventional radiology and in CT. It will also be useful for detecting other types of contrast medium.

The computed tomography (CT) values obtained by the energy subtraction method with a transXend detector, which measured X-rays as current and gave the corresponding X-ray energy information, show the disadvantage that the CT values are dependent on the thickness of a homogeneous phantom. In order to obtain constant CT values for a uniform material, a new unfolding method is proposed using variable response functions of the transXend detector according to the X-ray path length in the phantom. The CT values measured using the new unfolding method are discussed with respect to the energy range used in the unfolding process, the number of segment detectors, and the substrate of the segment detectors.