03 Nuclear
SUV lean-body mass (James)
SUV_LBM = C × LBM / A_inj. James LBM from height, weight and sex.
Listen
Listen · English
Simulation
SUV lean-body mass (James) — Change the numbers; the scene follows.
Where it works
PET/CT
Patient / uptake
In the patient on the PET couch — activity concentration, SUV, and internal dose.
Open this machineFormula
Variables
Results
LBM
Lean body mass
65.1453kg
SUV_bw
Body-weight SUV
1.2162
SUV_lbm
Lean-body-mass SUV
0.8803
Explanation
What it means
Body-weight SUV overestimates uptake in obese patients because fat takes up almost no FDG. PERCIST prefers SUV normalised to lean body mass (SUL). The James formula is the most common: LBM from weight (kg) and height (cm), different coefficients for male and female. SUL_peak of the background liver is the PERCIST reference. This is a working relation in Nuclear medicine.
Where it is used
Clinically it sits on the PET/CT — Patient / uptake. In the patient on the PET couch — activity concentration, SUV, and internal dose. Nuclear-medicine relations sit in the hot lab, on the camera, and in the voxel: decay, SUV, TOF, and counting statistics. They decide whether an uptake is real or a clock error.
PET/CT · Open this machineHow to use it
Enter activity concentration C (kBq/ml), injected activity (MBq), weight (kg), height (cm) and sex (1 = male, 0 = female). Read LBM, SUV_bw and SUV_lbm. Change one input and watch the curve and the simulation follow.
Symbols
- CActivity concentration5 kBq/ml
- AInjected activity370 MBq
- WWeight90 kg
- HHeight175 cm
- sex1 male / 0 female1
Worked example
A typical case from the default values: C = 5 kBq/ml (Activity concentration); A = 370 MBq (Injected activity); W = 90 kg (Weight); H = 175 cm (Height); sex = 1 (1 male / 0 female). Substituting into the relation gives LBM = 65.1453 kg; SUV_bw = 1.2162; SUV_lbm = 0.8803. These are teaching numbers — align them with your machine.
Typical values give
- LBM = 65.1453kg
- SUV_bw = 1.2162
- SUV_lbm = 0.8803
Where it comes from
The displayed formula is the working relation. SUV_LBM = C × LBM / A_inj. James LBM from height, weight and sex. Usual reference: James 1976 / Wahl PERCIST. Derive it in the specialty lesson, then return here to pin the numbers.
Reference: James 1976 / Wahl PERCIST
Assumptions & limits
James, not Janma or Boer. Does not compute a lean-tissue density or a CT-derived LBM. C must be decay-corrected to injection time. Sex is a binary coefficient, not a continuum.
Pitfalls
Activity is not counts. SUV needs the true injected activity, the residual, and the correct decay time — a clock off by 10 min on ¹⁸F is a several-percent error. Do not compare SUVs across reconstructions. James, not Janma or Boer. Does not compute a lean-tissue density or a CT-derived LBM. C must be decay-corrected to injection time. Sex is a binary coefficient, not a continuum.
Keep this
Write the assay time next to every activity. Decay does the rest. James, not Janma or Boer. Does not compute a lean-tissue density or a CT-derived LBM. C must be decay-corrected to injection time. Sex is a binary coefficient, not a continuum.
In this specialty