Objective evaluation method using multiple image analyses for panoramic radiography improvement

Introduction: In the standardization of panoramic radiography quality, the education and training of beginners on panoramic radiographic imaging are important. We evaluated the relationship between positioning error factors and multiple image analysis results for reproducible panoramic radiography. Material and methods: Using a panoramic radiography system and a dental phantom, reference images were acquired on the Frankfurt plane along the horizontal direction, midsagittal plane along the left-right direction, and for the canine on the forward-backward plane. Images with positioning errors were acquired with 1-5 mm shifts along the forward-backward direction and 2-10 degrees rotations along the horizontal (chin tipped high/low) and vertical (left-right side tilt) directions on the Frankfurt plane. The cross-correlation coefficient and angle difference of the occlusion congruent plane profile between the reference and positioning error images, peak signal-to-noise ratio (PSNR), and deformation vector value by deformable image registration were compared and evaluated. Results: The cross-correlation coefficients of the occlusal plane profiles showed the greatest change in the chin tipped high images and became negatively correlated from 6 degrees image rotation (r = -0.29). The angle difference tended to shift substantially with increasing positioning error, with an angle difference of 8.9 degrees for the 10 degrees chin tipped low image. The PSNR was above 30 dB only for images with a 1-mm backward shift. The positioning error owing to the vertical rotation was the largest for the deformation vector value. Conclusions: Multiple image analyses allow to determine factors contributing to positioning errors in panoramic radiography and may enable error correction. This study based on phantom imaging can support the education of beginners regarding panoramic radiography

Evaluating the index of panoramic X-ray image quality using K-means clustering method

Background A panoramic X-ray image is generally considered optimal when the occlusal plane is slightly arched, presenting with a gentle curve. However, the ideal angle of the occlusal plane has not been determined. This study provides a simple evaluation index for panoramic X-ray image quality, built using various image and cluster analyzes, which can be used as a training tool for radiological technologists and as a reference for image quality improvement. Results A reference panoramic X-ray image was acquired using a phantom with the Frankfurt plane positioned horizontally, centered in the middle, and frontal plane centered on the canine teeth. Other images with positioning errors were acquired with anteroposterior shifts, vertical rotations of the Frankfurt plane, and horizontal left/right rotations. The reference and positioning-error images were evaluated with the cross-correlation coefficients for the occlusal plane profile, left/right angle difference, peak signal-to-noise ratio (PSNR), and deformation vector fields (DVF). The results of the image analyzes were scored for positioning-error images using K-means clustering analysis. Next, we analyzed the correlations between the total score, cross-correlation analysis of the occlusal plane curves, left/right angle difference, PSNR, and DVF. In the scoring, the positioning-error images with the highest quality were the ones with posterior shifts of 1 mm. In the analysis of the correlations between each pair of results, the strongest correlations (r = 0.7–0.9) were between all combinations of PSNR, DVF, and total score. Conclusions The scoring of positioning-error images using K-means clustering analysis is a valid evaluation indicator of correct patient positioning for technologists in training

Quantitative Values from Synthetic MRI Correlate with Breast Cancer Subtypes

The purpose of this study is to correlate quantitative T1, T2, and proton density (PD) values with breast cancer subtypes. Twenty-eight breast cancer patients underwent MRI of the breast including synthetic MRI. T1, T2, and PD values were correlated with Ki-67 and were compared between ER-positive and ER-negative cancers, and between Luminal A and Luminal B cancers. The effectiveness of T1, T2, and PD in differentiating the ER-negative from the ER-positive group and Luminal A from Luminal B cancers was evaluated using receiver operating characteristic analysis. Mean T2 relaxation of ER-negative cancers was significantly higher than that of ER-positive cancers (p < 0.05). The T1, T2, and PD values exhibited a strong positive correlation with Ki-67 (Pearson’s r = 0.75, 0.69, and 0.60 respectively; p < 0.001). Among ER-positive cancers, T1, T2, and PD values of Luminal A cancers were significantly lower than those of Luminal B cancers (p < 0.05). The area under the curve (AUC) of T2 for discriminating ER-negative from ER-positive cancers was 0.87 (95% CI: 0.69–0.97). The AUC of T1 for discriminating Luminal A from Luminal B cancers was 0.83 (95% CI: 0.61–0.95). In conclusion, quantitative values derived from synthetic MRI show potential for subtyping of invasive breast cancers

RESOLUTION PROPERTIES OF CRT MONITORS

We have developed a new technique for measuring the modulation transfer function (MTF) of a cathode ray tube (CRT) monitor. The "nominal" MTF was measured by displaying a line image of a width of one pixel on the CRT monitor using the pattern generator. We also measured the effective pixel width. In order to obtain the "actual" MTF, the nominal MTF was divided by the sinc function which is the Fourier transform of the effective pixel width. The results indicate that the corrected MTF　converges to the constant value as the effective pixel width is narrower. Thus, the actual MTFs were determined and compared in the horizontal direction for two CRT monitors

Physical Properties of Screen-Film Systems - New System for Chest Radiography -

胸部専用の新しい増感紙／フィルムシステムについて物理的画質特性を測定し、従来のシステムと比較を行った。測定した新システムは、日本コダックのインサイトシステムからHC/IT-1、富士メディカルシステムのADシステムからHG-M/UR-1、コニカのEXシステムからXG-S/ES-C である。従来のシステムとして富士メディカルシステムのHR-4/Super HR-S を使用した。その結果、新システムは22～73％感度は高く、特性曲線においては低濃度部を持ち上げ、最大コントラストは高濃度側にシフトしていた。空間周波数2cycles/mmで相対鮮鋭度を比較すると、新システムが10～30％程度の低下となっていた。ノイズは、濃度1.0で新システムが35～46％の減少となった。以上より、新システムは、縦隔部の濃度を上げ、粒状性の改善を重視した設計となっていることが分かった。The new three screen-film systems, Kodack INSIGHT system HC/IT-1, Fuji AD system HG-M/UR-1, and Konica EX system XG-S/ES-C for chest radiography were evaluated. In addition, the conventional system Fuji HR-4/Super HR-S was measured for comparison with new systems. The evaluation method is as follows. The image quality characteristics, speed, contrast, resolution and granularity were measured. The sensitivity and contrast were determined by measuring the MTF (modulation transfer function) and NCTF (normalized contrast transfer function). The granularity was estimated by measuring the Wiener spectrum. The speed of the new systems were improved by 22% to 73%. The dinsities at the maximum gradient value were shifted to high density (2.0-2.7). However, they had 10% to 30% less resolution. The other hand, the granularities were improved by 21% to 37% at 1.0 density. These results suggested that the emphasis of new systems was put on improving the image quality of mediastinum region, maintaining performance of the conventional system

Physical Image Quality of Rapid Processing Films

The imaging properties of Konica "new" SR series films and "old" MG-SR series films for rapid processing were measured in combination with green-emitting intensifying screens. The measured image quality prarameters include: characteristic curve, modulation transfer function (MTF) and Wiener spectrum. The relative speeds of the new SR series systems were slower than those of the old MG-SR series systems from 10 to 25%. The MTF's of the new systems were generally comparable to those of the old systems, except that SR-G system was improved with an increase of approximately 10%. In the Wiener spectrum measurement, however, the new systems showed from 10 to 35% decrease in low-frequency noise

Analysis of Tempormandibular Joint by Image Processing -Discrimination of Condylar Position-

Tomography is clinically useful in the diagnosis of the temporomandibular joint (TMJ) syndrome. The TMJ is formed by the condyle and the glenoid fossa, and there exists TMJ space between them. Image processing was employed in the present study, and the reference points of the condyle and the glenoid fossa were determined from the tomogram. Subsequently, the TMJ space was measured automatically in the image analysis. The TMJs of 98 patients were examined practically and the characteristics of each result were studied. There is a possibility of discriminating an abnormal condylar position from a normal one by making use of the TMJ space and the distance between two reference points

Granularity of Asymmetric Screen-Film System

非対称増感紙フィルム系について、両面乳剤フィルムのウィナースペクトル測定に及ぼす影響を検討した。濃度0.5～2.5のノイズ試料のフロント乳剤、バック乳剤、支持体層それぞれで測定したスペクトルの和と、両面同時に測定した全スペクトルとを比較した。その結果、全ウィナースペクトルの値は、フロント乳剤、バック乳剤の和より高くなった。また、試料濃度が高いほど、その差は大きくなった。これらは、マイクロデンシトメータの光学系の配置と両面乳剤フィルムの構造に起因している。したがって、非対称システムのようにフィルムの前面と後面で特性を分けて考える場合、注意を要する。We have examined a factor affecting the Wiener spectrum measurement of double-emulsion film. An asymmetric screen-film system (Kodak HC/INSIGHT system) was used in this study. The results indicated that the total Wiener spectra of double-emulsion films are higher than the sum of spectra obtained with the front emulsion and back emulsion separately. These differences are attributed to the arrangement of the optical system of the microdensitometer used to measure and the structure of double-emulsion film