Table 1.

Overview of pros and cons of X-nuclei transmitter setting methods.

Nuclei	Method	Pros and Cons
Hyperpolarised Helium (3He)	A one-time procedure using a pickup coil and a 3He phantom [24,25].	Pro: Easy to set up for each coil providing transmitter settings without the use of hyperpolarised helium gas. Con: Use subject weight as loading and may introduce a bias given the difference in body coil and X-nuclei loading.
Sodium (23Na)	Natural abundance X-nuclei prescan of or default values [8,26,27].	Pro: Sodium signal has a high natural abundance in vivo making the signal renewable. Given the low sensitivity, the addition in time is limited compared to imaging acquisition time. Con: A dedicated X-nuclei scan needs to be performed per subject introducing workflow complexity.
Hyperpolarised Carbon (13C)	Using phantoms (e.g., urea or bicarbonate) or historical default values [16,18,28].	Pro: Ability to set transmitter settings without the use of hyperpolarised carbon. Con: Phantoms are placed away from the region of interest, introducing a bias. Default values may vary significantly in the abdominal and thoracic regions.
Hyperpolarised Xenon (129Xe)	X-nuclei prescan using low-concentration hyperpolarised xenon [3,29].	Pro: Provides in vivo pulmonary calibration of the xenon gas calibration. Con: Requires administration of an additional hyperpolarised xenon gas dose.