Ultra-High-Resolution Computed Tomography of the Lung: Image Quality of a Prototype Scanner

Abstract

PurposeThe image noise and image quality of a prototype ultra-high-resolution computed tomography (U-HRCT) scanner was evaluated and compared with those of conventional high-resolution CT (C-HRCT) scanners.Materials and MethodsThis study was approved by the institutional review board. A U-HRCT scanner prototype with 0.25 mm x 4 rows and operating at 120 mAs was used. The C-HRCT images were obtained using a 0.5 mm x 16 or 0.5 mm x 64 detector-row CT scanner operating at 150 mAs. Images from both scanners were reconstructed at 0.1-mm intervals; the slice thickness was 0.25 mm for the U-HRCT scanner and 0.5 mm for the C-HRCT scanners. For both scanners, the display field of view was 80 mm. The image noise of each scanner was evaluated using a phantom. U-HRCT and C-HRCT images of 53 images selected from 37 lung nodules were then observed and graded using a 5-point score by 10 board-certified thoracic radiologists. The images were presented to the observers randomly and in a blinded manner.ResultsThe image noise for U-HRCT (100.87 ± 0.51 Hounsfield units [HU]) was greater than that for C-HRCT (40.41 ± 0.52 HU; P < .0001). The image quality of U-HRCT was graded as superior to that of C-HRCT (P < .0001) for all of the following parameters that were examined: margins of subsolid and solid nodules, edges of solid components and pulmonary vessels in subsolid nodules, air bronchograms, pleural indentations, margins of pulmonary vessels, edges of bronchi, and interlobar fissures.ConclusionDespite a larger image noise, the prototype U-HRCT scanner had a significantly better image quality than the C-HRCT scanners.

Influence of field of view size on image quality: ultra-high-resolution CT vs. conventional high-resolution CT

“…The scores of the evaluation items increased at a constant rate when the FOV was reduced to 80 mm, but only slightly when the FOV was further reduced * Significant difference between FOV 40 mm and FOV 80 mm (p < 0.001); ** significant difference between FOV 40 mm and FOV 80 mm (p = 0.001); # significant differences between FOV 40 mm and FOV 160 mm (p < 0.001); ## significant difference between FOV 40 mm and FOV 160 mm (p = 0.001); ☨ significant difference between FOV 80 mm and FOV 160 mm (p < 0.001); ☨☨ significant difference between FOV 80 mm and FOV 160 mm (p = 0.001) The image noise of U-HRCT, but not conventional HRCT, was increased when the FOV was reduced from 80 to 40 mm. The spatial resolution of conventional HRCT is in the range of 0.23-0.35 mm [5,9,10]. When using a 512 × 512 matrix size, the size of one pixel at FOV 160 mm (80 mm) is 0.313 mm (0.156 mm).…”

“…We can conclude that in conventional HRCT improvements in image quality cannot be expected, and noise would not significantly increase, when the FOV is reduced from 80 to 40 mm, because the pixel size becomes smaller than the resolution. In U-HRCT, the spatial resolution is 0.14 mm [5,[7][8][9]. When using a 512 × 512 matrix size, the pixel size at FOV 40 mm is 0.078 mm.…”

“…However, noise is increased and image quality deteriorated by reducing the FOV [3,4]. Recently, ultra-high-resolution CT (U-HRCT) has been developed, characterized by a smaller focal size of the detector elements and the X-ray tube compared with conventional highresolution CT (conventional HRCT), allowing clearer CT images [5]. U-HRCT with 1024 × 1024 matrix size has been reported to improve image quality and diagnostic potential [6], and that a U-HRCT matrix size of 2048 × 2048 leads to larger improvement than sizes 512 × 512 or 1024 × 1024 [7].…”

“…However, no studies investigated the influence of FOV size on image quality in U-HRCT. The spatial resolution of conventional HRCT has been reported to range from 0.23 to 0.35 mm, and that of U-HRCT to be 0.14 mm [5,[7][8][9]. One pixel of matrix size (512 × 512) corresponds to 0.156 mm (0.078 mm) when the FOV size is 80 mm (40 mm).…”

The Molecular and Microbial Microenvironments in Chronically Diseased Lungs

“…Thus, it is reasonable to hypothesize that both specific microbial interactions in the lungs and differential abundances of antibiotics could result in metabolic divergence, creating isolated regions of enhanced biofilm formation and tissue damage that is often observed in CF patients by chest X-rays and CT-scans. Application of advanced techniques such as Ultra-High-Resolution Computed Tomography in conjunction with the approach presented here could be a focus of future studies (38).…”