The study protocol for the China Health Big Data (China Biobank) project

Abstract

Background: Osteoporosis, obesity, and fatty liver are increasingly common chronic diseases that seriously threaten people's health. Low-dose chest computed tomography (LDCT) scan is frequently used for lung cancer screening in health screenings and checkups. Quantitative computed tomography (QCT) enables the accurate measurement of volumetric bone mineral density (vBMD), liver fat content, and abdominal fat area using the existing LDCT data without extra radiation. We initiated a new project, the China Health Big Data (China Biobank), which combines the LDCT scan images from lung cancer screening of participants in health checkup with QCT to investigate the added value of QCT to LDCT, in order to establish the normative reference database and diagnosis criteria for the three aforementioned conditions.

Methods: The China Biobank project is a prospective nationwide multicenter cohort study that will combine QCT technology with LDCT scans to measure bone mineral density (BMD), intra-abdominal fat distribution, and liver fat content of the generally healthy checkup participants. Mindways QCT calibration phantom (Mindways Software Inc., Austin, TX, USA) and analysis software QCT PRO v6.0 will be used for all centers. Before data collection begins, the European Spine Phantom (ESP) will be used for quality control analysis at each collaborating center. The inclusion criteria are a healthy checkup participant aged 30-90 years, with LDCT as a part of his/her health checkup protocol. Exclusion criteria are pregnant women or participants with a metal implant in the CT scan area. The LDCT images will be transferred to the Mindways workstation for analysis, and vBMD in the L1 and L2 vertebrae, visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and liver fat content will be measured. As part of the health checkup, the demographic, anthropometric parameters, blood pressure, and a routine blood laboratory test will be collected. The estimated sample size will be about 30,000.

Results: The combination of QCT with LDCT of the chest was validated in this project. The vBMD of spine, visceral fat and liver fat can be measured with a LDCT chest scan.

Conclusions: The China Biobank project will assess the added value of QCT to LDCT, and enable accurate evaluation of the prevalence of osteoporosis, obesity, and fatty liver disease in a very large Chinese cohort.

Keywords: Osteoporosis; bone mineral density (BMD); liver fat content; quantitative computed tomography (QCT); soft tissue composition; subcutaneous adipose tissue (SAT); visceral adipose tissue (VAT).

Figure 1

QCT measurement of L1 (A) and L2 (B) lumbar spine BMD. The dual-yellow lines indicate the location and upper and lower range of interest (region of interest, ROI), the yellow oval ROIs show the measurement range of vertebral, and the BMD unit is mg/cm3. QCT, quantitative computed tomography; BMD, bone mineral density.

Figure 2

Measurement of abdominal fat by Mindways QCT software. The blue color represents the fat, and the yellow dashed line depicts the abdominal wall. The fat inside this wall is visceral fat (VAT), while the fat outside the wall is subcutaneous fat (SAT). Total fat area (TAT) = VAT + SAT. QCT, quantitative computed tomography.

Figure 3

Measurement of liver fat content by QCT using Mindways liver fat module. The slice in the middle of the L2 is chosen, 3 region of interests (ROIs) (shown in red circle) are measured, with one in the left robe of the liver (A) and two in the right lobe (B,C). The liver fat content in % is shown and saved in the database. The average of 3 ROIs is the value for this subject. QCT, quantitative computed tomography.