[Optimal Beam Quality in Chest Radiography Using CsI-flat Panel Detector for Detection of Pulmonary Nodules].

OBJECTIVES: Optimal beam quality for detection of pulmonary nodules in digital chest radiography using CsI-flat panel detector (FPD) was investigated in consideration of image quality and patient dose. METHODS: The human chest phantom with inserted imitated nodules (diameter: 10 mm, CT value: +30 Hounsfield unit (HU), -375 HU, -620 HU) was used for the measurement of contrast-to-noise ratio (CNR) of imitated nodules by twenty beams arranged by five tube voltages and four filters. RESULTS: The CNR varies with X-ray tube voltage and added filter. CNR correlates weakly to the tube voltage, fairly to the effective energy in second-order polynomial and strongly to the quality index (effective energy divided X-ray tube voltage). In order to improve the CNR, the effective energy and the quality index are kept about 50 keV and more than 0.5, respectively, using an 80-100 kV beam with a copper filter. CONCLUSION: A 90 kV (2.5 mm Al inherent filtration) beam with a 0.15 mm copper filter and a 90 kV or 100 kV (2.5 mm Al inherent filtration) beam with a 0.2 mm copper filter are appropriate for chest radiography using CsI-FPD.

[Evaluation of 90 kV Beam with 0.15 mm Cu Filter in Chest Radiography Using CsI-flat Panel Detector].

PURPOSE: To compare the visibility of anatomic structure in chest radiography acquired with different beam quality (120 kV beam and 90 kV beam with 0.15 mmCu) using CsI-flat panel detector. METHOD: Pair image obtained by different beam quality of 100 person's chest radiographies which were taken periodical health examination were compared with the visibility of normal structures (pulmonary vessels) and abnormal opacities by two pulmonologists and four radiological technologists. Moreover, the spectrum of the two beam quality were calculated using Monte Carlo simulation. RESULT: Dominant observers gave high score significantly (p<0.01) to the 90 kV beam's image in spite of 20% less dose. Monte Carlo simulation showed that 90 kV beam with 0.15 mmCu were much absorbed primary photon than 120 kV beam to CsI detector, and less absorbed secondary photon. CONCLUSION: The visibility of anatomic structure and abnormal opacities in FPD chest radiography was improved by using the 90 kV beam with 0.15 mmCu than traditional 120 kV beam's chest radiography.