MHU
Mega Heat Units — the thermal capacity of an X-ray tube's anode. 1 HU = 1 watt-second × 1.35 (for three-phase generators); 1 MHU = 1 million HU. The headline thermal-capacity spec used in CT, interventional, and angiographic tube specifications.
Why it matters to buyers: Higher MHU supports longer or heavier protocols without cooling delays. Reference points:
- Performix Pro VCT 100 (GE) — 8.0 MHU.
- Straton (Siemens) — rotating-envelope architecture; effective heat handling exceeds the conventional MHU spec because heat sinks directly through the anode shaft.
- Gemstone Clarity (GE) and MegaCool (Siemens) and Philips MRC — modern liquid-cooled tubes with high effective heat handling.
Interventional and high-volume CT programs prioritize MHU; a marginal tube on a busy practice trips thermal limits at peak load.
Why it matters to engineers: A tube's MHU rating caps sustained duty cycle. Exceeding it triggers cooling delays; chronically pushing the limit shortens tube life. Modern liquid-cooled rotating-anode tubes effectively bypass conventional MHU calculations by sinking heat through the anode shaft into oil. Chiller / cooling-loop health is the upstream constraint.