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Formatting and Analysis of Thermal Images
Published in James Stewart Campbell, M. Nathaniel Mead, Human Medical Thermography, 2023
James Stewart Campbell, M. Nathaniel Mead
For these reasons, grayscale and reverse (negative) grayscale thermal images are now mainly of historical interest, though they are still found in research publications. Grayscale is also useful for manual focusing during image acquisition. Ironically, from a physics standpoint, all infrared images are grayscale (one analog value per pixel) and must be assigned “false colors” to be best analyzed by the human visual system. When displaying grayscale images, it is important to generate them from the original radiometric thermal image file. A blue-red spectral color thermogram printed as grayscale will give ambiguous gray values, as shown in Figure 7.5.
Principles behind Computed Tomography (CT)
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Mikael Gunnarsson, Kristina Ydström
The more grayscale levels an imaging system can represent, the better its contrast resolution. By changing the width of the window setting, center the grayscale levels to be presented, the contrast can be varied.
Introduction
Published in Debbie Peet, Emma Chung, Practical Medical Physics, 2021
Debbie Peet, Emma Chung, Jasdip Mangat, Joanne Cowe
Most, but not all, medical images are represented as a greyscale image ranging from white to black. It is important that equipment settings used to display medical images show the full range of greyscale; this can be tested by viewing a test card such as that shown in Figure 1.7. Each image also has a certain image resolution related to the number of pixels, or voxels, for a 3D dataset.
Anterior Segment Optical Coherence Tomography in Pediatric Ocular Pathology: Imaging Study of 115 eyes
Published in Expert Review of Medical Devices, 2023
Images were obtained at the horizontal (0° and 180°), vertical (90° and 270°) and oblique meridians (135° and 315°; 45° and 225°) as well. The examination was carried out in the sitting position for young children with the standard chin and forehead mounted-device. The height of the chin rest was adjusted for each patient. For smaller children, this was done in the standing position. Even smaller children were held in their laps by their parents. It is a non-contact device, with no need for any anesthesia. The AS-OCT images obtained by our device are in grayscale or monochrome, representing the backscattered light intensity in a cross-sectional scheme. The grayscale is directly related to the tissue reflectivity. False colors may be used to delineate the boundaries of various structures like the corneal layers but may create artificial boundaries.
A comparison of results following the treatment of placenta accreta and placenta increta using high-intensity focused ultrasound followed by hysteroscopic resection
Published in International Journal of Hyperthermia, 2021
Zhenjiang Lin, Chunmei Gong, Qin Huang, Zhendong Zhang, Donghong Wang, Li Yuan, Xi Wang, Qiang An, Dayong Chen, Song Liu, Xiaofeng Zou, Raymond Setzen, Bing Yang, Lian Zhang
All patients completed HIFU treatment in one session. As shown in Figure 2(B), grayscale change was observed in real-time ultrasound monitoring images and a non-perfused area was observed in contrast-enhanced ultrasound after HIFU (Figure 2(D)). The median interval between post-pregnancy and HIFU treatment was 16.8 ± 2.96 days in the group of patients with placenta accreta, and it was 11.71 ± 1.59 days in the group of patients with placenta increta. The median HIFU treatment time was 50 min (interquartile range: 24–71) and the median sonication time was 400 s (interquartile range: 300–730) in the group of patients with placenta accreta, while they were 69 min (interquartile range: 49–85) and 655 s (interquartile range: 450–950) in the group of patients with placenta increta. The median HIFU treatment energy was 160 (interquartile range: 117–292) KJ in the group of patients with placenta accreta, while it was 262 (interquartile range: 180–380) KJ in the group of patients with placenta increta. The median non-perfused volume (NPV) ratio, which was defined as NPV divided by the placenta volume immediately after HIFU treatment, was 87% in the group of patients with placenta accreta, while it was 90% in the group of patients with placenta increta. No significant difference was observed in the interval between post-pregnancy and HIFU, HIFU treatment time, acoustic energy generated during treatment, sonication time, and NPV ratio between the two groups (Table 2).
A novel technique for analysing histogram equalized medical images using superpixels
Published in Computer Assisted Surgery, 2019
In this paper, firstly, we make use of two techniques to equalize the histograms of low contrast grayscale images and then we use four superpixel algorithms to segment the histogram-equalized images into superpixels. Finally, we extract the superpixel segments of the equalized images using four segmentation algorithms and compare the results. Our results show that SLIC superpixels are compact, grid-shaped and equal to the k number of superpixels that we extracted before the histogram equalization. We have tested grayscale medical images for experiments. Figure 1 shows the original image, two histogram equalized images, and histograms of each image. The flowchart of the proposed method is shown in Figure 2. Where GHE and CLAHE stands for Global Histogram Equalization and Contrast Limited Adaptive Histogram Equalization respectively. Moreover, Figure 3 illustrates the superpixels of original images as well as a comparison between the superpixels generated before and after histogram equalization. Subsequent sections of this paper contain a discussion of the histogram equalization techniques in section 2, a brief introduction of superpixel segmentation algorithms in section 3, our proposed technique in section 4, comparison of the results of segmentation is shown in section 5 and finally, section 6 concludes the paper.