The purpose of this study was to investigate the relationship between
tumor size and blood volume for patients with lung
tumors, using dual-energy computed tomography (DECT) and a gemstone spectral imaging (GSI) viewer. During the period from March 2011 to March 2013, 50 patients with 57 medically inoperable lung
tumors underwent DECT before stereotactic body radiotherapy (SBRT) of 50-60 Gy in 5-6 fractions. DECT was taken for pretreatment evaluation. The region-of-interest for a given spatial placement of the
tumors was set, and averages for CT value, water density and
iodine density were compared with
tumor size. The average values for
iodine density in
tumors of ≤ 2
cm, 2-3 cm, and >3 cm maximum diameter were 24.7, 19.6 and 16.0 (100 µg/cm(3)), respectively. The average value of the
iodine density was significantly lower in larger
tumors. No significant correlation was detected between
tumor size and average CT value or between
tumor size and average water density. Both the average water density and the average CT value were affected by the amount of air in the
tumor, but the average
iodine density was not affected by air in the
tumor. The average water density and the average CT value were significantly correlated, but the average
iodine density and the average CT value showed no significant correlation. The blood volume of
tumors can be indicated by the average
iodine density more accurately than it can by the average CT value. The average
iodine density as assessed by DECT might be a non-invasive and quantitative assessment of the radio-resistance ascribable to the hypoxic cell population in a
tumor.