Yuji Ogata

Quantitative analysis for computed tomography findings of various diffuse lung diseases using volume histogram analysis.

Objectives: The aim of this study was to achieve the quantitative analysis of the characteristic computed tomography (CT) findings and course of interstitial pneumonia using the volume histogram method. Methods: Contrast (CNT), variance (VAR), and entropy (EPY) values from whole-lung volume data were compared between normal lungs and 5 diseases that have characteristic CT findings. Thirteen cases with nonspecific interstitial pneumonia (NSIP) were evaluated before and after treatment. Results: In cases with thickening of the bronchovascular bundles and interlobular thickening, ground-glass attenuation, airspace consolidation, and honeycombing, the values of VAR and EPY were greater than those in the normal cases (P < 0.05). In the cases with NSIP, the CNT value after treatment was significantly greater and the values of VAR and EPY after treatment were significantly lower than those before treatment (P < 0.05). Conclusions: Volume histogram analysis is a promising method for the evaluation of diffuse lung diseases and the effectiveness of treatment.

Clinical evaluation of a newly developed method for avoiding artifacts caused by dental fillings on X-ray CT.

To evaluate the clinical usefulness of gantry tilt scanning as an image reconstruction technique for avoiding artifacts caused by metallic dental fillings. Gantry tilt scanning was used with multidetector-row computed tomography for imaging in patients with dental fillings. Using a novel PC-based program, the oblique images obtained were reconstructed to transverse images using nearest neighbor and bilinear interpolation methodologies in order to avoid metallic streak artifacts. Coronal images were reformatted with the reconstructed transverse images, and the continuity of the reconstructed images was evaluated. Gantry tilt scanning was performed in 12 patients with metal artifacts, and the original and reconstructed images were classified into four grades and assessed by two radiologists. Results of the clinical evaluation indicated that the original images with artifacts, only 4% had good image quality in the region around the medial pterygoid muscle, only 8% depicted areas around the internal carotid artery and internal jugular vein, and only 12% could depict the areas around the parotid gland in the clinical evaluation. These values were improved to 60, 96, and 100%, respectively, in the reconstructed transverse images. Gantry tilt scanning as an image reconstruction technique improves image quality and removes most, if not all, artifacts caused by metallic dental fillings. The resulting images can be used in the evaluation of oropharyngeal lesions in patients with dental fillings.

Volume histogram analysis for lung thin-section computed tomography: differentiation between usual interstitial pneumonia and nonspecific interstitial pneumonia.

Objective: The aim of this study was to evaluate volume histogram analysis between usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP). Methods: Sixty cases (UIP, n = 22; NSIP, n = 38) were evaluated retrospectively. Three parameters (contrast, variance, and entropy) were calculated in 3 types of regions of interest (ROIs): (a) whole lung, (b) right lower lobe, and (c) cubic ROIs. To evaluate the influence of extent of abnormal findings, the numbers of voxels with low or high density in whole lung were compared with the 3 parameters. Result: No significant differences were observed between the ROIs of whole lung and the right lower lobe. In all cubic ROIs, entropy in UIP was larger than that in NSIP (P < 0.001). The numbers of voxels with low-density areas significantly correlated with the values of contrast and entropy, whereas those with high-density areas significantly correlated with all 3 parameters. Conclusion: Volume histogram analysis for cubic ROIs may be feasible for differentiating between UIP and NSIP.

Novel display technique for reference images for visibility of temporal change on radiographs--color digital summation radiography.

PurposeThe present study investigated color digital summation radiography (CDSR) as a novel display technique for reference images for the visibility of temporal change on radiographs. In CDSR, only the parts with temporal differences are displayed in color. Moreover, all other parts are displayed in gray scale.Materials and MethodsCDSR was defined as “radiographs combined by the additive color mixture method”. The visibility of simulated nodules located in the lung fields and mediastinum was evaluated by 12 radiologists (mean experience, 9.8 years; range, 1–26 years) for 24 conventional radiographs and CDSR for 6 color patterns. A five-point rating system (5, very good; 4, good; 3, adequate; 2, poor; 1, very poor) was used.ResultsThe mean scores (average±standard deviation) for the visibility of simulated nodules were as follows: magenta, 3.88±0.90; blue, 3.08±0.72; green, 3.04±0.86; red, 3.00±0.98; cyan, 2.71±0.86; and yellow, 2.50±0.72. Compared to conventional radiography in gray scale, at 1.21±0.41, all six color patterns for CDSR displayed significantly improved scores (p<0.001).ConclusionCDSR might represent a useful technique for reference images from chest digital radiography.

Evaluation of usefulness of color digital summation radiography for solitary pulmonary nodules on chest radiographs.

PurposeThe aim of this study was to evaluate the usefulness of novel color digital summation radiography (CDSR) for detecting solitary pulmonary nodules on chest radiographs by observers with different levels of experience.Materials and methodsA total of 30 healthy controls and 30 patients with newly detected solitary pulmonary nodules were evaluated. Six radiologists and five residents evaluated three image sets: set A, current and prior radiographs only; set B, set A with temporal subtraction images; and set C, set A with CDSR. The observers were asked to rate each image set using a continuous rating scale. In addition, the reading time required for each set was recorded.ResultsThe radiologists showed no significant differences in the mean Az value between set A, set B, and set C. However, the residents showed significant differences between set A and set B and between set A and set C. In addition, for set B and set C, the mean reading time per case of all readers was significantly shorter than that for set A.ConclusionThe detection capability of observers with little experience is comparable to that of experienced observers when reading radiographs with temporal subtraction images or with CDSR. The usefulness of CDSR is comparable to that of temporal subtraction.

Evaluation of the usefulness of color digital summation radiography in temporally sequential digital radiographs: a phantom study

PurposeThe purpose of this study was to assess the usefulness of color digital summation radiography (CDSR) for detection of nodules on chest radiographs by observers with different levels of experience.Materials and methodsA total of 30 radiographs of chest phantoms with abnormalities and 30 normal ones were arranged at random. Set A was conventional radiographs only. Set B consisted of both conventional radiographs and CDSR images, which were colored with magenta. Five chest radiologists and five residents evaluated both image sets on a TFT monitor. The observers were asked to rate each image set using a continuous rating scale. The reading time for each set was also recorded.ResultsIn set A, the performance of chest radiologists was significantly superior to that of the residents (P < 0.05). However, in set B, there was no significant difference in the performance of the chest radiologists and the residents. In both observer groups, the mean reading time per case in set B was significantly shorter than that in set A (P < 0.01).ConclusionBy using CDSR, the detection capability of observers with little experience improves and is comparable to that of experienced observers. Moreover, the reading time becomes much shorter using CDSR.

Low-dose x-ray imaging GLG: restoration by Kalman filter

The present study was designed to monitor novel ideas in the acquisition and manipulation of data in an X-ray imaging system. A grid was sandwiched between two cascaded imaging plates (Ips). Using a fan-beam X-ray tube and a single exposure scheme, the two Ips, respectively, recorded gridless and grid (GLG) type information of the object. Referring to the mathematical model of the GLG technique, it was explained that the collected data associated with the gridless IP was of high (S/N) and suppressed scattered components. Based on this assumption and using a Gaussian convolution kernel representing the effect of scattering, a technique was proposed to estimate scatter parameters of the GLG plates. Then, a Kalman filter was developed to restore noisy blurred images of the GLG techniques using the Ips data and estimated parameters. The results are shown for both the computer simulated and real X-ray phantom data.