See JAX Pipeline on the IMPC website for order of tasks for all mice tested

Project protocol: Dual Energy X-ray Absorptiometry (DXA)

• Introduction
• Study design
• Workflow
• Equipment, software and supplies
• Procedure
• Measurements
• Experimental and technical parameters

Introduction

DXA is used to measure bone mineral content and density as well as to assess body composition. DXA uses an X-ray generator of high stability to produce photons over a broad spectrum of energy levels. Its photon output is filtered to produce the two distinct peaks necessary to distinguish bone from soft tissue.

Study design

Paradigm: Baseline study

Panel: Collaborative Cross

Number of strains: 18

Sex: Both

Age: 13-15 wks

Sample size: Seven mice per sex from at least two litters

Number of cohorts: 1

Workflow

Step	Description	Equipment	Data collected
1	Anesthetize mice	-	-
2	Weigh mice, measure length	Balance, ruler	Body weight, body length
3	Measure bone mineral content and density, and determine body composition	DXA	Bone mineral content, bone mineral density, fat mass, lean mass, bone area

Equipment, software and supplies

• Dual Energy X-ray Absorptiometry: GE Medical Systems Lunar Piximus II [See Experimental and technical parameters]

Procedure

1. The volume of anesthetic solution (Avertin) required for i.p. injection is calculated and recorded.
2. Mice are anesthetized.
3. Mice are weighed and length is measured (nose to beginning of tail).
4. Each unconscious mouse is placed in the DXA analyzer.
5. A scout-scan is performed.
6. The area of interest is optimized and a measure-scan performed.
7. The standard analysis is a whole body analysis, excluding the head.
8. Remove mouse once image is captured. Place on heated mat set at 37°C, in a cage and monitor closely until consciousness is regained.

 

Data QC: Calibration of the system is done in daily intervals using the phantoms provided by the manufacturer.

Formulas and derivations: Fat mass = TTM x percent fat / 100. Lean mass = TTM - fat mass.

 

Measurements

LIMS field name	MPD variable name	Description	Units	Series	Primary measurement	Series order	MPD computed	Calculation	Method	Data type
Body weight	body_weight	body weight	g						DXA	Float
Fat mass	fat	fat tissue mass of whole body scan, head excluded	g						DXA	Float
Lean mass	lean	lean tissue mass of whole body scan, head excluded	g						DXA	Float
Bone mineral density	BMD	bone mineral density of whole body scan, head excluded	g/cm2						DXA	Float
Bone mineral content	BMC	bone mineral content of whole body scan, head excluded	g						DXA	Float
Body length	body_length	body length	cm						DXA	Float
BMC/Body weight	BMC_adj	bone mineral content to body weight ratio	ratio						DXA	Float
Lean/Body weight	lean_adj	lean tissue mass to body weight ratio	ratio						DXA	Float
Fat/Body weight	fat_adj	fat tissue mass to body weight ratio	ratio						DXA	Float
Bone area	bone_area	bone area, whole body scan, head excluded	cm2						DXA	Float
% fat	pct_fat	percent fat, whole body scan, head excluded	%						DXA	Float
TTM	TTM	total tissue mass, whole body scan, head excluded	g						DXA	Float

Experimental and technical parameters

Equipment name	Dual Energy X-ray Absorptiometry Analyzer
Equipment manufacturer	GE Medical Systems
Equipment model	Lunar Piximus II
Anesthesia	Avertin