When using a voltage source in EIT, it is necessary to know both the applied voltageand the resulting current with high precision. If it is desired to have the applied voltage remain unchanged for a wide range of load impedance, then it is necessary to have a voltage source with low output impedance.
n electrical impedance tomography (EIT), we inject currents through ... the output impedance at the frequency of 50 KHz or higher employing a better method of stray .... Measured boundary voltagedata are used to reconstruct cross-sectional ...
Yes from what I can see the existing commonly used Current sources such as Howland type suffer from having large phase shifts at even 1MHz. I have been measuring very small capactiances for about 30 years injecting current and think the methods use can be applied to EIT giving much better Current sources with low phase shift past 10MHz. But I haven't practically tested them yet. There are some papers investigating unique phase shiftss caused by cancer at around 3MHz. This is what inspired me to carry out some circuit design and simulation over the past three years.