Original Jpn J Radiol Technol 1999 ; 55 (11) :
Improvement in Visibility of Simulated Lung Nodules
on Computed Radiography(CR)Chest Images by Use
of Temporal Subtraction Technique

NOBUHIRO ODA, SHIGEHIKO KATSURAGAWA,1) KUNIO DOI,2) KEIJI FUJIMOTO, SEIICHI MURAKAMI, and HAJIME NAKATA3)
Department of Radiology, University Hospital of Occupational and Environmental Health
1) Division of Medical Engineering, Iwate Medical University
2) Kurt Rossmann Laboratories for Radiologic Image Research, Department of Radiology, University of Chicago
3) Department of Radiology, University of Occupational and Environmental Health, School of Medicine
Received May 19, 1999; Revision accepted Aug. 27, 1999; Code Nos. 254, 522
Summary
A temporal subtraction image obtained by subtraction of a previous image from a current one can enhance interval change on chest images. In this study, we compared the visibility of simulated lung nodules on CR images with and without temporal subtraction. Chest phantom images without and with simulated nodules were obtained as previous and current images, respectively, by a CR system. Then, subtraction images were produced with an iterative image warping technique. Twelve simulated nodules were attached on various locations of the chest phantom. The diameter of nodules having a CT number of 47 ranged from 3 mm to 10 mm. Seven radiologists subjectively evaluated the visibility of simulated nodules on CR images with and without temporal subtraction using a three-point rating scale(0: invisible, +1: questionable, +2:visible). The minimum diameter of simulated nodules visible at a frequency greater than 50% was 4 mm on the CR images with temporal subtraction and 6 mm on those without. Our results indicated that the subtraction images clearly improved the visibility of simulated nodules.
Key words: Chest radiography, Computed radiography(CR), Temporal subtraction, Image processing, Simulated lung nodule