Further reduction of radiation dose in helical CT for lung cancer screening using small tube current and a newly designed filter.
A new aluminum filter, 5.8 mm thick at the center, was designed. The effective energy, exposure dose, absorbed dose, and noise were measured by using low-dose technique, very low-dose technique with a conventional filter, and very low-dose technique with a new filter on a chest phantom. Accuracy of very low-dose computed tomography (CT) with a new filter was compared against standard helical CT in 40 patients and against chest radiography in 35 patients. Effective energies were 42.6 keV and 51.6 keV at a conventional filter and the new filter, respectively. Compared against 20mA with a conventional filter, exposure dose was reduced by 17%, and absorbed dose was equivalent, at 30 mA with the new filter. Noise was improved by 9%. Compared with standard helical CT, the sensitivity, specificity, and accuracy of very-low-dose helical CT were 100%, 88%, and 95%, respectively. Very-low-dose helical CT was found to be significantly superior to chest radiography in the detection of lung cancers. Using a smaller tube current and an appropriate filter allows a further reduction in radiation dose in helical CT for lung cancer screening.
Itoh
S
S
Department of Radiology, Nagoya University School of Medicine, Japan.
Koyama
S
S
Ikeda
M
M
Ozaki
M
M
Sawaki
A
A
Iwano
S
S
Ishigaki
T
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000535:Aluminum; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*
D000535:Aluminum