Development of Upright CT and Its Initial Evaluation: Effect of Gravity on Human Body and Potential Clinical Application
Although humans spend most of their daily lives in an upright position, very few imaging methods can be used to analyze the anatomical structures and pathophysiology of the whole human body while in a standing or sitting position. In 2014, we initiated a project to develop an upright CT device that would enable the visualization and quantitative evaluation of the effects of gravity on the whole human anatomical structures and pathologic conditions. In 2017, the development of the first ever upright CT with 320-detector row CT scanner was completed and introduced at our hospital. Although achieving a high-speed, high-precision vertical rotation while minimizing vibration was challenging, we confirmed spatial resolution, noise, or CT number of the upright CT was comparable to those of a conventional 320-detector row CT scanner. Furthermore, differences in the anatomical structure of a normal volunteer were observed when images were taken in an upright versus supine position, suggesting potential advantages of using upright CT over conventional CT for the evaluation of certain diseases.
KeywordsUpright CT Horizontal CT Gravity Area detector CT 4-D CT
27.1 X-Ray Imaging of the Human Body
27.2 Cross-Sectional Imaging of Human Body
27.3 Development of Upright CT
Upright CT devices offer substantial advantages: (1) they have the potential to replace poorer quality X-ray examinations, (2) they enable the visualization of cross sections of the entire human body (including soft tissue) while the body is subjected to a load or gravity, and (3) they enable functional imaging using 4-D scanning.
We presented a proposal for an upright CT device to Toshiba Medical Systems (presently Canon Medical Systems). To assuage company concerns regarding clinical indications and profitability, we listed several conceivable clinical applications and gathered information regarding the needs and benefits of such a device from various medical fields to convince the company of the wide applications of such a device. The “Upright CT Project” was finally approved in 2014.
The most difficult task was to achieve a high-speed, high-precision vertical rotation while minimizing the vibration, since even miniscule amounts of vibration cause motion artifacts, degrading image quality. Several advanced technologies were introduced to solve this problem. The second task was to create various aids to enable the subject to maintain a stable standing position. We also created a knee-high acrylic wall that encircles the subject’s body to help prevent falls.
27.4 Physical Properties and Clinical Data Analysis
After the introduction of an upright CT device for whole body imaging at our institute, we first evaluated several physical properties using a phantom to confirm whether the vertical movements of the gantry degraded the image quality. Spatial resolution, noise, and low contrast resolution were analyzed using a modulation transfer function, noise-power spectrum and visual inspection, respectively. As a result, each factor of the upright CT was comparable to conventional 320-detector row CT scanner.
During scans of volunteers, we noticed that the workflow for upright CT examinations proceeds very smoothly, compared with conventional scans. In an upright CT examination, the patient enters the CT room and proceeds directly into the gantry space; the scan begins immediately thereafter. In a conventional CT examination, however, the patient must first lie down on the scanner bed and the examiner must then raise the bed and position the bed within the gantry.
A quantitative analysis of clinical data revealed that the structure of the brain is slightly descended when the subject is in an upright position, compared with a supine position, although the brain was previously thought not to move. We also found that gravity differentially affects the volume and shape of the vena cavae depending on position, while those of the aorta remain constant regardless of the position. The lung volume was larger in an upright position than in a supine position, and the amount of change was larger for the lower lobe than for the upper or middle lobes. The centerline of the body was strongly correlated with the area of contact between the hip joint and the femoral head. Furthermore, we also confirmed that an upright CT examination can reveal more remarkable findings than conventional CT examinations in patients with various diseases, such as spondylolisthesis, inguinal hernia and pelvic prolapse.
We would like to quantify all human anatomical structures in three-dimensions while the subject is in an upright position and to quantify the effect of gravity on the human body by comparing CT images taken while the subject is in either a supine or upright position. Upright CT has the potential to become a powerful tool for both functional evaluations and evaluations of pathogenesis in the human body.
- Haschek H, Lindenthal OT (1896) A contribution to the practical use of the photography according to Röntgen. Wien Klin Wschr 9:63Google Scholar
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