Quantitative benchmarking of iodine imaging for two CT spectral imaging technologies: a phantom study.

BACKGROUND: The aim of this study was to quantitatively benchmark iodine imaging across specific virtual monoenergetic energy levels, iodine maps and virtual non-contrast images with different phantom sizes and iodine concentrations, using a rapid switching dual-energy CT (DECT) and a dual source DECT, in order to investigate accuracy and potential differences between the technologies. METHODS: Solutions of iodine contrast (10, 20, 30, 50, and 100 mg/mL), sterile water and saline were scanned in a phantom on a rapid switching single-source and dual-source DECT scanners from two different vendors. The phantom was equipped with polyurethane rings simulating three body sizes. The datasets were reconstructed in virtual monoenergetic energy levels (70, 80, 90, 100, 110, 120, 130, and 140 keV), virtual non-contrast images and iodine maps. HU and iodine concentrations were measured by placing ROIs in the iodine solutions. RESULTS: The iodine concentrations were reproduced with a high degree of accuracy for the single-source DECT (1.8-9.0%), showing a slight dependence on phantom size. The dual source DECT technique showed deviant values (error -33.8 to 12.0%) for high concentrations. In relation to the virtual non-contrast measurements, the images from both vendors were affected by the iodine concentration and phantom size (-127.8 to 539.1 HU). Phantom size did not affect the calculated monoenergetic attenuation values, but the attenuation values varied between the scanners. CONCLUSIONS: Quantitative measurements of post-processed images are dependent on the concentration of iodine, the phantom size and different technologies. However, our study indicates that the iodine maps are reliable for quantification of iodine.

CT density in lung cancer patients after radiotherapy sensitized by metoclopramide. A subgroup analysis of a randomized trial.

PURPOSE: To investigate the lung tissue response measured with computed tomography (CT) after radiotherapy (RT) combined with metoclopramide. PATIENTS AND METHODS: Patients with non-small cell lung cancer (tumor stage IIIA and IIIB), included in a multicenter, randomized phase III trial investigating the use of metoclopramide as a radiosensitizing agent, were examined with repetitive post-RT CT scans. The analysis comprised data up to 100 days after RT for a subgroup of 16 patients treated with a total dose of 60 Gy given in 1.82 Gy per fraction. RESULTS: Large radiation doses to subvolumes were associated with denser lung tissue measured with CT (p < 0.001). Opposed to this finding, the volume of lung tissue irradiated with significant doses (V(40Gy)) was negatively correlated with the average increase in lung tissue density (p = 0.003). Patients randomized to metoclopramide injections also experienced less increase in lung tissue density (p = 0.01). CONCLUSION: There was an increase in the density of irradiated lung tissue with radiation dose and time after RT. Metoclopramide and significant radiation doses to larger lung volumes (V(40Gy)) seemed to protect against fibrosis development.