DXA (Bone Densitometry)

What it does

DXA reads a dual-energy X-ray absorptiometry study: lumbar spine, hip and forearm scans, with a lateral-spine vertebral fracture assessment (VFA) image and a whole-body scan when they were acquired. Bone mineral density is measured by the scanner's own software, so the run takes the BMD values from the vendor result pages instead of measuring them again, and applies the ISCD reporting rules to them: T- and Z-scores per site, the WHO category, the change against the prior scan judged by least-significant change, and a FRAX prompt.

Where the images allow more, the run reads them too. On the VFA image it grades each vertebra for fracture and scores calcification of the abdominal aorta; on a whole-body scan it returns regional lean and fat mass. A quality check flags positioning and region-of-interest errors and the vertebrae that should be excluded from the spine result.

Intended use

Decision support for the clinician who reports or acts on the scan. Degenerative change and vertebral fractures can falsely raise spine BMD, and a vertebral fracture changes fracture risk and treatment whatever the T-score; both are easy to overlook on a printed result page. The run brings density, fractures and scan quality into one structured result.

Who it is for

GPs, endocrinologists, rheumatologists, geriatricians, radiologists and technologists in bone-density services. Developers can turn DXA exports into structured data for an osteoporosis registry or fracture liaison service.

Accepted input

• Vendor DXA exports from Hologic and GE: the scan images as Secondary Capture plus the vendor BMD results as DICOM SR or result pages.
• Spine, hip and forearm scans, optionally with a lateral-spine VFA image and a whole-body scan.
• A prior DXA study for change over time.

Requirements

Requirement	Why
Vendor BMD results (DICOM SR or result pages)	BMD values are parsed from them, not re-measured
Scan images with the vendor regions of interest	Positioning, ROI placement and excluded vertebrae are checked on the images
Age and sex	WHO T-score categories apply to postmenopausal women and men aged 50 and over; younger adults are reported by Z-score
Lateral-spine VFA image	Needed for vertebral fracture grades and the aortic calcification score
Whole-body scan	Needed for body composition
Prior study from the same scanner	Change is judged against the least-significant change

Optional context

Menopausal status, risk factors for FRAX (previous fracture, glucocorticoid use, parental hip fracture, smoking) and current treatment in clinical_context complete the fracture-risk prompt.

The result

One JSON result in sections, with every score traced to the vendor value or image it came from.

Section	Content
Bone density	Vendor BMD results per site parsed into T- and Z-scores, the WHO category by ISCD rules, change versus the prior against the least-significant change, and a FRAX prompt
Scan quality	Positioning, ROI placement, artefacts and vertebrae to exclude from the spine result
Vertebral fracture assessment	Genant grade for each vertebra on the VFA image
Aortic calcification	Abdominal aortic calcification score on the VFA image
Body composition	Regional lean and fat mass, appendicular lean mass index (ALMI), visceral adipose tissue and a sarcopenia flag
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

Standards

• Reporting: ISCD Official Positions for acquisition, analysis and reporting, including site selection and least-significant change.
• Classification: WHO T-score criteria for normal, low bone mass (osteopenia) and osteoporosis; FRAX for 10-year fracture probability.
• VFA: Genant semi-quantitative method as applied in ISCD vertebral fracture assessment.
• Aortic calcification: Kauppila AAC-24 score.
• Body composition: EWGSOP2 cut-offs for low muscle mass.
• DICOM: TID 1500 Measurement Report for scores and measurements, Encapsulated PDF.